parameterization of soil properties for a model of topographic controls on shallow landsliding application to rio de janeiro a key problem in the use of physically based models of landslide hazards is how to parameterize the representation of soil properties we applied a physically based model for the topographic control on shallow landsliding shalstab to two catchments in rio de janeiro to investigate the accuracy of model results in relation to parameterization of soil properties in so doing we address the relevance of values derived from laboratory tests to the field problem as well as the trade offs inherent in model parameterization we ran the model for all combinations of reasonable cohesion bulk density and friction angle values and compared model predictions to mapped landslides scars we rank sorted model performance through the proportion of the total area of landslide scars correctly predicted as potentially unstable application of the model to an area where soil properties are not well known can be based on either a standard parameterization that emphasizes topographic controls or on local calibration of soil parameters against a map of known landslide locations our analysis suggests that in general acquisition of high quality digital elevation models dems is more important than generation of spatially detailed soil property values for reconnaissance level assessment of shallow landslide hazards

non monotonic decrease of coal permeability with depth in highly compressional tectonic settings a case study in the bide santang basin sw china abstract coal permeability dependence on depth has been studied and discussed for a long time however the scattered distribution of coal permeability versus depth and specifically the non monotonic permeability decrease in highly compressional tectonic settings has not been fully understood this paper takes the bide santang basin sw china as a case study to discuss the non monotonic decrease of coal permeability with depth the results show that three regime intervals including the uppermost normal regime interval the middle mixed regime interval and the deep normal regime interval are identified in the bide santang basin a tri segmented linear model provides a better fit of coal permeability than a single linear model does coal permeability in the uppermost normal regime interval is characterized by exceptionally high values and quick decrease rate with increasing depth in comparison with that in other intervals the middle mixed regime interval is characterized by a permeability increasing trend with depth related primarily to the increase of horizontal differential stress in this interval in the deep normal regime interval the horizontal differential stress does not show any obvious trend and coal permeability resumes its decreasing trend with depth this study reveals the primary role of the horizontal differential stress besides the effective stress in controlling coal permeability in highly compressional tectonic settings characterized by stress regime transitions

growth characteristics and genetic types of pores and fractures in a high rank coal reservoir of the southern qinshui basin abstract in this paper field investigations such as underground coal wall observations and core log analyses have been conducted and combined with laboratory experiments such as the mercury intrusion method the low temperature liquid nitrogen adsorption method photomicrography and scanning electron microscopy sem to study the growth characteristics and genetic types of pores micro fractures and macro fractures in coal bed 3 of the southern qinshui basin and to analyze the connections between pores and fractures the results show that this coal bed prioritizes micropores and transition pores i e intermolecular pores and residual gas pores followed by macropores i e plant tissue pores and intergranular pores mesopores metamorphic gas pores do not develop moreover coal bed 3 contains a considerable number of closed and semi closed pores it develops two groups of exogenous fractures and cleats i e endogenous fractures and the formation is controlled by a paleotectonic stress field the cleats have a relatively small density and are usually filled by calcite and other minerals which are harmful to the permeability of the coal bed shrinkage micro fissures static pressure micro fissures structure micro fissures and ultramicroscopic fissures are all widely developed and are not filled by minerals micro fissures are important channels for the connections between pores and cleats ultramicroscopic fissures cut through some gas pores these two types of fractures improve the permeability and connectivity of the coal bed and are important links between different sizes of pores and fractures there are three levels of connections between pores and fractures namely connections between ultramicrostructures and microstructures connections between microstructures and cleats and connections between cleats and exogenous fractures

factors controlling high yield coalbed methane vertical wells in the fanzhuang block southern qinshui basin abstract whether a coalbed methane cbm well achieves high yield is controlled by various factors structural and hydrological control models of cbm productivity in vertical wells were built using a combined investigation of basic tectonic settings and hydrological conditions as well as drainage parameters of the coal reservoir in the fanzhuang block southern qinshui basin this study indicates that gas water production differs significantly among wells with different structural settings or hydrogeological conditions low and unstable gas production rates in individual wells are the primary problem for the cbm development in the fanzhuang block the impacts of some geologic and engineering factors on gas production were analyzed and estimated based on comparative analysis quantitative analysis and gray system theory the results indicate that the critical reservoir ratio crr liquid column height lch and gas content are the most important factors in determining well productivity followed by the equivalent drainage radius edr the volume of frac sand and the decline rate of working fluid levels during initial production high yield wells in the fanzhuang block always have the following conditions gas content 20 m 3 t burial depth of 500 700 m crr 0 7 lch 400 m volume of frac sand 40 m 3 edr of 30 60 m and a decline rate of working fluid level lower than 2 m day during the initial production stage

landslide susceptibility analysis using gis and artificial neural network the purpose of this study is to develop landslide susceptibility analysis techniques using an arti cial neural network and to apply the newly developed techniques to the study area of yongin in korea landslide locations were identi ed in the study area from interpretation of aerial photographs eld survey data and a spatial database of the topography soil type and timber cover the landslide related factors slope curvature soil texture soil drainage soil effective thickness timber age and timber diameter were extracted from the spatial database using those factors landslide susceptibility was analysed by arti cial neural network methods the landslide susceptibility index was calculated by the back propagation method which is a type of arti cial neural network method and the susceptibility map was made with a geographic information system gis program the results of the landslide susceptibility analysis were veri ed using landslide location data the validation results showed satisfactory agreement between the susceptibility map and the existing data on landslide location a gis was used to ef ciently analyse the vast amount of data and an arti cial neural network to be an effective tool to maintain precision and accuracy the results can be used to reduce hazards associated with landslides and to plan land use and construction copyright 2003 john wiley sons ltd

gis based groundwater spring potential mapping in the sultan mountains konya turkey using frequency ratio weights of evidence and logistic regression methods and their comparison summary in this study groundwater spring potential maps produced by three different methods frequency ratio weights of evidence and logistic regression were evaluated using validation data sets and compared to each other groundwater spring occurrence potential maps in the sultan mountains konya turkey were constructed using the relationship between groundwater spring locations and their causative factors groundwater spring locations were identified in the study area from a topographic map different thematic maps of the study area such as geology topography geomorphology hydrology and land use cover have been used to identify groundwater potential zones seventeen spring related parameter layers of the entire study area were used to generate groundwater spring potential maps these are geology lithology fault density distance to fault relative permeability of lithologies elevation slope aspect slope steepness curvature plan curvature profile curvature topographic wetness index stream power index sediment transport capacity index drainage density distance to drainage land use cover and precipitation the predictive capability of each model was determined by the area under the relative operating characteristic curve the areas under the curve for frequency ratio weights of evidence and logistic regression methods were calculated as 0 903 0 880 and 0 840 respectively these results indicate that frequency ratio and weights of evidence models are relatively good estimators whereas logistic regression is a relatively poor estimator of groundwater spring potential mapping in the study area the frequency ratio model is simple the process of input calculation and output can be readily understood the produced groundwater spring potential maps can serve planners and engineers in groundwater development plans and land use planning

stress relief coalbed methane drainage by surface vertical wells in china abstract this paper summarizes the status of engineering practice technology and research related to stress relief coalbed methane cbm drainage using surface wells in china during the past 10 years comments are provided on the theory and technical progress of this method in high gas mining areas such as the huainan huaibei and tiefa mining areas characterized by heavily sheared coals with relatively low permeability stress relief cbm surface well drainage has been successfully implemented and has broad acceptance as a cbm exploitation technology the fundamental theories underpinning stress relief cbm surface well drainage were established in china and include elements relating to 1 rock layer deformation theory vertical zoning and horizontal partitioning and the change in the stress condition in mining stopes 2 a theory regarding an abscission circle in the development of mining horizontal abscission fracture and vertical broken fracture in overlaying rocks and 3 the theory of stress relief inducing permeability increase in protected coal seams during mining and the gas migration accumulation theory of stress relief cbm surface well drainage three kinds of technical drainage modes are described protected seam surface well drainage in areas influenced by mining represented mainly in the huainan mining area gob surface well drainage most prominently in the tiefa mining areas and the multipurpose surface well drainage used in the huaibei mining areas serial well allocation in which wells are used for different purposes as extraction and mining proceeds and well bore configurations and designs suitable for this purpose are described the development and utilization of cbm is significant to energy saving emission reduction and to ensure safety in coal production

implications of the pore pressure and in situ stress for the coalbed methane exploration in the southern junggar basin china abstract the southern junggar basin hosts abundant coalbed methane cbm resources and is expected to be an important cbm production base in china the pore pressure and in situ stress are key factors that influence the exploration and development of cbm however these factors are poorly understood in this area based on extended leak off test data mathematical models were established for pore pressure and in situ stress prediction using regression analysis subsequently the correlations between the pore pressure in situ stress and permeability were analyzed and the stress ratios were investigated finally the forming mechanism of stress zonation in the study area was discussed the results show that cbm reservoirs are generally underpressured and partly overpressured at depths greater than 800 m in the study area the study area is characterized by notable stress zoning the stress regime varies from reverse to strike slip to normal faulting with increasing depth significantly positive correlations exist between the pore pressure maximum principal stress minimum principal stress vertical stress and principal stress difference the minimum horizontal stress is approximately 70 of the vertical stress in the study area a mud weight window varying from the pore pressure to the most likely breakdown pressure is suggested at depths greater than 600 m a relatively high principal stress difference is observed which indicates that deep coals have a relatively high mechanical strength and their permeability can be enhanced by hydraulic fracturing the depth dependent stress zonation is mainly due to the influence of thrusting on the in situ stress which diminishes with increasing depth the compressional stress regime in the shallow area benefits the sealing of faults and the preservation of cbm resources in the study area the deep cbm resources have a development potential the outcomes of this study contribute to the cbm exploration and development in the study area

fast ground water mixing and basal recharge in an unconfined alluvial aquifer konza lter site northeastern kansas abstract ground water chemistry and water levels at three levels in a well nest were monitored biweekly for two and a half years in a shallow unconfined floodplain aquifer in order to study the dynamics of such shallow aquifers the aquifer in northeastern kansas consists of high porosity low hydraulic conductivity fine grained sediments dominated by silt and bounded by fractured limestone and shale bedrock results show that the aquifer underwent chemical stratification followed by homogenization three times during the study period the length of time between maximum stratification and complete homogenization was 3 5 months the chemical parameters most useful for demonstrating the mixing trends were dissolved nitrate and sulfate higher nitrate concentrations were typical of unsaturated zone water and were sourced from fertilizer applied to the cultivated fields on the floodplain variations in sulfate concentrations are attributed to dissolution of rare gypsum in limestone bedrock and variable evapoconcentration in the unsaturated zone the mixing of three chemically different waters entrained unsaturated zone water water entering the base of the floodplain aquifer and water in residence before each mixing event was simulated the resident water component for each mixing event was a fixed composition based on measured water chemistry in the intermediate part of the aquifer the entrained water composition was calculated using a measured composition of the shallow part of the aquifer and measurements of soil water content in the unsaturated zone the incoming basal water composition and the fractions of each mixing component were fitted to match the measured chemistry at the three levels in the aquifer a conceptual model for this site explains 1 rapid water level rises 2 water chemistry changes at all levels in the aquifer coincident with the water level rises 3 low measured hydraulic conductivity of the valley fill and apparent lack of preferential flow pathways 4 minuscule amounts of unsaturated zone recharge and 5 dissolved oxygen peaks in the saturated zone lagging water level peaks we postulate that rainfall enters fractures in bedrock adjacent to the floodplain this recharge water moves rapidly through the fractured bedrock into the base of the floodplain aquifer the recharge event through the bedrock causes a rapid rise in water level in the floodplain aquifer and the chemistry of the deepest water in the floodplain aquifer changes at that time the rising water also entrains slow moving nitrate rich unsaturated zone water altering the chemistry of water in the shallow part of the aquifer vertical chemical stratification in the aquifer is thus created by the change in water chemistry in the upper and lower parts of the saturated zone as the water level begins to decline the aquifer undergoes mixing that eventually results in homogeneous water chemistry the rise in water level from the recharge event also displaces gas from the unsaturated zone that is then replaced as the water level declines following the recharge event this new oxygen rich vadose zone air equilibrates rapidly with saturated zone water resulting in a dissolved oxygen pulse in the ground water that peaks one half to 2 months after the water level peak this oxygen pulse subsequently declines over a period of 2 6 months

comparison of bivariate and multivariate statistical approaches in landslide susceptibility mapping at a regional scale abstract landslide susceptibility assessment was undertaken for the waikato region new zealand landslide inventory data were extracted from a pre existing database that included few landslides in the region 1 4 of area and is limited in terms of completeness of record and location uncertainty this database is in contrast to those normally used for research which are derived for the research project and are complete and accurate but is representative of those that may exist within government bodies this paper applies statistical methods to derive a meaningful predictive map for planning purposes from such a relatively poorly defined database susceptibility maps for both logistic regression and weights of evidence were derived and evaluated using success prediction and roc curves both statistical methods gave models with fair predictive capacity for validation samples from the original database with areas under roc curves auc of 0 71 to 0 75 an independent set of landslide data compiled from observations made in google earth showed lower overall prediction quality with the logistic regression method giving the best prediction auc 0 71 for this regional assessment categorical data proved a major constraint on the application of logistic regression as the area considered has complex geology and geomorphology as a result the large number of categories required led to a complex and unwieldy statistical model whereas division into fewer categories meant that real variability in the area could not be adequately represented this limited the result to a model with two continuous variables slope and mean monthly rainfall the incomplete record in the database proved of little concern for the logistic regression method as the model was able to generalise landslide locations from the known sites well giving a similar auc value for the original and independent data the same was not true for the weights of evidence method which was not successful at predicting landslides outside those in the original data

assessing redox zones and seawater intrusion in a coastal aquifer in south korea using hydrogeological chemical and isotopic approaches a shallow 25 m coastal alluvial groundwater system underneath a paddy field in the yangyang area of south korea was investigated to examine the occurrence of redox processes the aquifer is affected by seawater intrusion and is characterized by a highly reducing environment facilitated by high organic matter in the sediments hydrochemical data with 34s and 18o of sulfate were examined for depth specific groundwater from two multilevel samplers that were installed at seaward yy2 and landward yy1 locations shallow groundwater showed distinct patterns of redox zoning evidence of significant bacterial sulfate reduction bsr was observed throughout the nearly entire depths of the two boreholes while at the depths of active seawater intrusion in yy2 conditions suitable for methanogenesis were never reached thus at yy2 the deep zone of intense bsr was overlain by a zone in which methanogenesis occurred in a low sulfate environment in contrast concurrent bsr and methanogenesis in yy1 occurred at depths with high sedimentary organic matter and low dissolved sulfate due to intensive bsr considerable bsr in the groundwater representing trapped seawater in a clay layer had resulted in a very strong increase of 34ssulfate up to 99 9 the inferred sulfur isotopic enrichment factor e for bsr in the lower part of yy2 was 12 3 while e at yy1 was much higher 45 9 in addition the observed trends of 18osulfate at yy1 indicated significant oxygen isotope exchange of sulfate oxygen with ambient water likely because of lower cell specific rates of bsr and higher sulfur isotope fractionation as indicated by the 34s in contrast there was little evidence of oxygen isotope exchange between water and so42 at yy2 this study indicates that in coastal aquifers with sulfate reducing activity 34s and 18o of sulfate can reveal zones of active seawater intrusion and of trapped seawater this study provides an example of the application of sulfur and oxygen isotope data with hydrochemical and hydrogeologic data to interpret complex redox zonation in an organic rich coastal environment

numerical modeling of gas flow in deformed well casing for the prediction of local resistance coefficients pertinent to longwall mining and its engineering evaluation during gob gas venthole ggv drainage the borehole casing is to withstand various forces induced by the movement of overlying strata of the longwall panel so as to become deformed tensile deformation compressive deformation and shear deformation are the most typical deformation modes of the casing once deformation of the casing occurs the flow resistance of gas in casing increases sharply which causes the volumetric flow of gob gas recovery to decrease through an analysis of the cross sectional shapes of three typical casing deformations the characteristic parameters of each kind of deformation were determined in addition a numerical simulation of the gas flow field was carried out using the four casing models i e one without deformation and three with typical deformations the changing characteristics of the local resistance coefficient of the deformed casing with varying characteristic parameters of corresponding deformation were analyzed in addition this study compared the local resistance coefficient of casings for the three deformation models and deduced that the local resistance coefficient resulting from shear deformation is the largest furthermore by considering the flow field characteristics of gas in the three models this study determined that the vortex induced by the separation of the boundary layer in the areas of deformation was a major cause of local resistance finally a method for predicting the characteristic parameter values of casing deformation was proposed and a case study was performed the research results provide a theoretical basis for predicting the influence of casing deformation on ggv drainage

isrm suggested methods for rock stress estimation part 3 hydraulic fracturing hf and or hydraulic testing of pre existing fractures htpf contents1 introduction 10112 summaryoftestmethods 10123 assumptionsandlimitations 10123 1 hydraulicfracturing hf 10123 2 hydraulictestsonpre existingfractures htpf 10124 apparatus 10134 1 fractureorientationdetectiondevices 10145 personnelquali cation 10146 equipmentperformance 10147 hydraulicfracturingtestprocedure 10148 hydraulic fracturedelineation 10168 1 impressionpackertechnique 10168 2 geophysicalimagingtechnique 10179 obtainingcriticalpressureparametersfromthepressure timerecords 101710 stresscalculations 101810 1 hydraulicfracturing hf 101810 2 hydraulictestsonpre existingfractures 101911 reportingofresults 1019references 1020

evolution of coal bed methane in southeast qinshui basin china insights from stable and noble gas isotopes abstract the late carboniferous early permian coal seams of the qinshui basin in shanxi province are the most prolific producer of coalbed methane cbm in china methane formed in the late triassic during deep burial and reheating in late jurassic early cretaceous driven by magmatic underplating basin inversion brought the coal seams to 400 700 m from the surface in the mid late cenozoic here we present results of a study aimed at understanding the origin of the methane and how it was affected by cenozoic exhumation of the basin methane from a 12 km traverse perpendicular to the basin margin in the southeast part of the basin have stable isotope compositions 13c 30 2 to 35 2 and d 155 to 194 indicating a thermogenic origin with limited biogenic input they are however lighter than expected based on coal maturity and c1 c2 c3 1000 are significantly higher than typical thermogenic methane 90 of the radiogenic 4he produced in the coals has been lost prior to equilibrium between gas and water phase in the reservoir this likely occurred in response to gas loss process during rapid exhumation in cenozoic showing that the he and ar content of natural gases is a sensitive indicator of gas loss event caused by recent basin inversion the event may have led to the loss of up to 44 of the methane from the coal seams this study demonstrates the importance of basin inversion on gas preservation in shallow cbm and shows that in contrast to 13cch4 the light noble gases are essential for tracing such a process

regional coseismic landslide hazard assessment without historical landslide inventories a new approach currently regional coseismic landslide hazard analyses require comprehensive historical landslide inventories as well as detailed geotechnical data consequently such analyses have not been possible where these data are not available a new approach is proposed herein to assess coseismic landslide hazard at regional scale for specific earthquake scenarios in areas without historical landslide inventories the proposed model employs fuzzy logic and geographic information systems to establish relationships between causative factors and coseismic slope failures in regions with well documented and substantially complete coseismic landslide inventories these relationships are then utilized to estimate the relative probability of landslide occurrence in regions with neither historical landslide inventories nor detailed geotechnical data statistical analyses of inventories from the 1994 northridge and 2008 wenchuan earthquakes reveal that shaking intensity topography and distance from active faults and streams are the main controls on the spatial distribution of coseismic landslides average fuzzy memberships for each factor are developed and aggregated to model the relative coseismic landslide hazard for both earthquakes the predictive capabilities of the models are assessed and show good to excellent model performance for both events these memberships are then applied to the 1999 chi chi earthquake using only a digital elevation model active fault map and isoseismal data replicating prediction of a future event in a region lacking historic inventories and or geotechnical data this similarly results in excellent model performance demonstrating the model s predictive potential and confirming it can be meaningfully applied in regions where previous methods could not for such regions this method may enable a greater ability to analyze coseismic landslide hazard from specific earthquake scenarios allowing for mitigation measures and emergency response plans to be better informed of earthquake related hazards

contamination of groundwater under cultivated fields in an arid environment central arava valley israel the purpose of this study is to obtain a better understanding of groundwater contamination processes in an arid environment precipitation of 50 mm year due to cultivation additional aims were to study the fate of n k and other ions along the whole hydrological system including the soil and vadose zone and to compare groundwater in its natural state with contaminated groundwater through the drilling of several wells a combination of physical chemical and isotopic analyses was used to describe the hydrogeological system and the recharge trends of water and salts to the aquifers the results indicate that intensive irrigation and fertilization substantially affected the quantity and quality of groundwater recharge low irrigation efficiency of about 50 contributes approximately 3 5 4 million m 3 year to the hydrological system which corresponds to 0 65 m per year of recharge in the irrigated area by far the

assessment of shallow landslide susceptibility by means of multivariate statistical techniques several multivariate statistical analyses have been performed to identify the most influential geological and geomorphological parameters on shallow landsliding and to quantify their relative contribution a data set was first prepared including more than 30 attributes of 230 failed and unfailed slopes the performance of principal component analysis t test and one way test allowed a preliminary selection of the most significant variables which were used as input variables for the discriminant analysis the function obtained has classified successfully 88 5 per cent of the overall slope population and 95 6 per cent of the failed slopes slope gradient watershed area and land use appeared as the most powerful discriminant factors a landslide susceptibility map based on the scores of the discriminant function has been prepared for ensija range in the eastern pyrenees an index of relative landslide density shows that the results of the map are consistent copyright 2001 john wiley sons ltd language en

gis based regional landslide susceptibility mapping a case study in southern california landslides threaten lives and property throughout the united states causing in excess of 2 billion in damages and 25 50 deaths annually in regions subjected to urban expansion caused by population growth and or increased storm intensities caused by changing climate patterns the economic and society costs of landslides will continue to rise using a geographic information system gis this paper develops and implements a multivariate statistical approach for mapping landslide susceptibility the presented susceptibility maps are intended to help in the design of hazard mitigation and land development policies at regional scales the paper presents a a gis based multivariate statistical approach for mapping landslide susceptibility b several dimensionless landslide susceptibility indexes developed to quantify and weight the influence of individual categories for given potential risk factors on landslides and c a case study in southern california which uses 11 111 seismic landslide scars collected from previous efforts and 5389 landslide scars newly digitized from local geologic maps in the case study seven potential risk factors were selected to map landslide susceptibility ground slope and event precipitation were the most important factors followed by land cover surface curvature proximity to fault elevation and proximity to coastline the developed landslide susceptibility maps show that areas classified as having high or very high susceptibilities contained 71 of the digitized landslide scars and 90 of the seismic landslide scars while only occupying 26 of the total study area these areas mostly have ground slopes higher than 46 and 2 year 6 hour precipitation greater than 51 mm only 12 of digitized landslides and less than 1 of recorded seismic landslides were located in areas classified as low or very low susceptibility while occupying 42 of the total study region these areas mostly have slopes less than 27 and 2 year 6 hour precipitation less than 41 mm copyright 2007 john wiley sons ltd

a gis based landslide susceptibility evaluation using bivariate and multivariate statistical analyses bivariate and multivariate statistical analyses were used to predict the spatial distribution of landslides in the cuyahoga river watershed northeastern ohio u s a the relationship between landslides and various instability factors contributing to their occurrence was evaluated using a geographic information system gis based investigation a landslide inventory map was prepared using landslide locations identified from aerial photographs field checks and existing literature instability factors such as slope angle soil type soil erodibility soil liquidity index landcover pattern precipitation and proximity to stream responsible for the occurrence of landslides were imported as raster data layers in arcgis and ranked using a numerical scale corresponding to the physical conditions of the region in order to investigate the role of each instability factor in controlling the spatial distribution of landslides both bivariate and multivariate models were used to analyze the digital dataset the logistic regression approach was used in the multivariate model analysis both models helped produce landslide susceptibility maps and the suitability of each model was evaluated by the area under the curve method and by comparing the maps with the known landslide locations the multivariate logistic regression model was found to be the better model in predicting landslide susceptibility of this area the logistic regression model produced a landslide susceptibility map at a scale of 1 24 000 that classified susceptibility into four categories low moderate high and very high the results also indicated that slope angle proximity to stream soil erodibility and soil type were statistically significant in controlling the slope movement

a physically based model for the topographic control on shallow landsliding a model for the topographic influence on shallow landslide initiation is developed by coupling digital terrain data with near surface through flow and slope stability models the hydrologic model topog o loughlin 1986 predicts the degree of soil saturation in response to a steady state rainfall for topographic elements defined by the intersection of contours and flow tube boundaries the slope stability component uses this relative soil saturation to analyze the stability of each topographic element for the case of cohesionless soils of spatially constant thickness and saturated conductivity the steady state rainfall predicted to cause instability in each topographic element provides a measure of the relative potential for shallow landsliding the spatial distribution of critical rainfall values is compared with landslide locations mapped from aerial photographs and in the field for three study basins where high resolution digital elevation data are available tennessee valley in marin county california mettman ridge in the oregon coast range and split creek on the olympic peninsula washington model predictions in each of these areas are consistent with spatial patterns of observed landslide scars although hydrologic complexities not accounted for in the model e g spatial variability of soil properties and bedrock flow control specific sites and timing of debris flow initiation within areas of similar topographic control

mapping of cleats and fractures as an indicator of in situ stress orientation jharia coalfield india abstract cleats and fractures in coal of barakar formation in jharia coalfield india have been mapped from the coal exposures around 21 opencast and 2 underground coal mines macro cleat distribution observed from this mapping is similar to that of well developed coalbed methane cbm basins the opencast coal mines are distributed in se nw direction along the boundary of the sickle shaped jharia coal basin permeability of cbm through coal seams is the most critical property deciding the viability of any cbm field it is largely controlled by the degree of cleat development this paper discusses cleat orientation and other structural features observed in the outcrops of 14 major coal seams in jharia coalfield and its directional relationship with the in situ stress sh orientation pattern cleat orientation is found to vary laterally within same seam at the different locations distributed from the south east part to the north western part of jharia coalfield face cleat orientation of the 21 opencast coal mines varies from n45 e to n45 w change of orientation of cleat observed around the mining areas is related the orientation of fault systems and orientation of igneous intrusions occurring within the coal bearing packet maximum in situ horizontal compressive stress sh direction is found to be parallel to the face cleat orientation in normal faulted basin like jharia coalfield an overall nne ssw and nw se orientation of the sh direction is predicted in the coal mines from cleat orientation mapping sh orientation is locally modified at places close to the tectonic features and igneous intrusives finite element stress modeling is carried out near moonidih area cleat orientation predicted stress direction matches well with the finite element stress results

a coupled approach to simulate initiation of outbursts of coal and gas model development an outburst of coal and gas is a major hazard in underground coal mining it occurs when certain conditions of coal stress strength and gassiness are met the outburst is recognized as a two step process i e initiation and development each step has its own characteristics and requires different approaches in numerical modeling as a first step the initiation process of the outburst is numerically simulated with a coupled simulator the simulator models the deformation and failure of a coal seam adsorption and desorption of gas and flow of gas and water in coal the simulator is developed by linking and sequentially executing two numerical codes flac3d and comet3 flac3d is a widely used commercial code designed for engineering mechanics computation while comet3 is a well established code to model gas and water production from desorption controlled reservoirs in this paper these two codes are linked and sequentially executed through coupling modules including a user designed c module and several modules developed with the build in fish language in flac3d these coupling modules are used to transfer relevant data between the codes a simple example to simulate the initiation of the outburst is also presented in this paper to demonstrate the capability of the coupled simulator

estimation of the water balance of alluvial aquifers in region of high isotopic contrast an example from southeastern france the much contrasted orographic and climatic characters of southeastern france serve to establish a hydrological balance of the porous aquifers in the region comparing a regional average gradient of 18o content versus elevation which was calculated on low water period karst waters content with a 10 5 average d of alpine rivers an estimate of the percentages brought to these aquifers is proposed under the form of an abacus it appears that the main groundwaters of the var the durance and the rhone are fed by an average of 20 30 of provencal underground contribution and 70 80 shallow contribution from the alpine rivers these figures reveal that local supplies range between 25 and 10 of the average yearly discharge flowing in the porous and shallow aquifers

constraining coalbed methane reservoir petrophysical and mechanical properties through a new coal structure index in the southern qinshui basin northern china implications for hydraulic fracturing structurally deformed coal sdc influences not only gas outbursts during coal mining but also coalbed methane cbm production different sdcs have different mechanical strengths and physical properties the structurally constrained petrophysical and mechanical properties of a cbm reservoir from the southern qinshui basin sqb northern china have been investigated by using a coal structure index csi the csi was established as a quantitative criterion for the deformation of sdcs based on surface conditions and blockiness using the data of 783 coring samples from 109 cbm wells the results show that undeformed coal and slight brittle sdcs are dominant in the sqb with ductile sdcs distributed locally both compressive strength and tensile strength decline exponentially with increasing csi average avg coal structure is a crucial factor for coal seam fracturing with an increasing csi avg the major fracture length will first increase to the maximum of 266 m at a csi avg of 45 and then decrease rapidly however branch fractures are independent of the csi avg the major fracture height attained a minimum of 4 39 m at a csi avg of 40 and then slowly increased therefore slightly brittle sdcs should be beneficial for fracturing at least for high rank coals the presence of variable sdcs can have a considerable impact on cbm reservoir petrophysical and mechanical properties finally a csi model that strives to establish the relation between structure deformation and cbm reservoir physical and mechanical properties in coal is expected to effectively guide hydraulic fracturing

landslide hazard evaluation a review of current techniques and their application in a multi scale study central italy in recent years growing population and expansion of settlements and life lines over hazardous areas have largely increased the impact of natural disasters both in industrialized and developing countries third world countries have difficulty meeting the high costs of controlling natural hazards through major engineering works and rational land use planning industrialized societies are increasingly reluctant to invest money in structural measures that can reduce natural risks hence the new issue is to implement warning systems and land utilization regulations aimed at minimizing the loss of lives and property without investing in long term costly projects of ground stabilization government and research institutions worldwide have long attempted to assess landslide hazard and risks and to portray its spatial distribution in maps several different methods for assessing landslide hazard were proposed or implemented the reliability of these maps and the criteria behind these hazard evaluations are ill formalized or poorly documented geomorphological information remains largely descriptive and subjective it is hence somewhat unsuitable to engineers policy makers or developers when planning land resources and mitigating the effects of geological hazards in the umbria and marche regions of central italy attempts at testing the proficiency and limitations of multivariate statistical techniques and of different methodologies for dividing the territory into suitable areas for landslide hazard assessment have been completed or are in progress at various scales these experiments showed that despite the operational and conceptual limitations landslide hazard assessment may indeed constitute a suitable cost effective aid to land use planning within this framework engineering geomorphology may play a renewed role in assessing areas at high landslide hazard and helping mitigate the associated risk

soft computing in assessment of earthquake triggered landslide susceptibility this study compared two soft computing methods that are applied to soft computation in assessment of earthquake triggered landslide susceptibility the support vector machine svm and artificial neural networks ann as a case study a series of landslide susceptibility maps were constructed for the affected area of the 2013 minxian zhangxian gansu province china mw 5 9 earthquake from data available 2330 coseismic landslides were partitioned into two subsets which were used as a training dataset and a test dataset respectively in addition other 1631 points on the map were randomly selected as non landslide samples in those areas were not influenced by the coseismic landslides ten conditioning factors of landslides were considered including elevation relative relief slope angle slope aspect slope curvature slope position lithology peak ground acceleration pga distance from the probable seismogenic fault and distance along the fault using the ann and svm ten landslide susceptibility maps were produced for the study area cross comparisons and validations of these ten resulting maps with real coseismic landslides show that the polynomial kernel type with a high enough polynomial degree term value e g 5 or 6 of the svm technology is most appropriate for coseismic landslide susceptibility assessment which is a challenge to the previously held notion that the svm method with radial basis function is the most suitable

geology of coalbed methane reservoirs in the southeast qinshui basin of china abstract the no 15 coal seam of the pennsylvanian taiyuan formation and the no 3 coal seam of the permian shanxi formation in the southeast qinshui basin are relatively thick 3 m laterally continuous and are of anthracite rank ro 2 2 4 5 the depth of these coal seams is generally between 200 and 700 m a tectonic thermal event during the jurassic to cretaceous yanshanian orogeny controlled coalification and thermogenic hydrocarbon generation because the generation of late stage bacterial gas coalbed methane in the southeast qinshui basin occupies two zones which are the mixed thermogenic and late stage bacterial gas zone near the basin margins and the dominantly thermogenic gas zone in the structurally deep part of the basin basin hydrodynamics causes low gas content in the shallow subsurface 20 m3 t because cleats are rare and are mostly filled with calcite the permeability of the coalbed methane reservoir is controlled by shear fractures the recharge and flow of groundwater not only control gas content but also control reservoir pressure abnormally high pressure reservoir in the deep stagnant zone is a favorable area for coalbed methane exploration and development the current coalbed methane wells are generally completed in the deep stagnant zone

lithology dependent minimum horizontal stress and in situ stress estimate abstract based on the generalized hooke s law with coupling stresses and pore pressure the minimum horizontal stress is solved with assumption that the vertical minimum and maximum horizontal stresses are in equilibrium in the subsurface formations from this derivation we find that the uniaxial strain method is the minimum value or lower bound of the minimum stress using anderson s faulting theory and this lower bound of the minimum horizontal stress the coefficient of friction of the fault is derived it shows that the coefficient of friction may have a much smaller value than what it is commonly assumed e g f 0 6 0 7 for in situ stress estimate using the derived coefficient of friction an improved stress polygon is drawn which can reduce the uncertainty of in situ stress calculation by narrowing the area of the conventional stress polygon it also shows that the coefficient of friction of the fault is dependent on lithology for example if the formation in the fault is composed of weak shales then the coefficient of friction of the fault may be small as low as f 0 2 this implies that this fault is weaker and more likely to have shear failures than the fault composed of sandstones to avoid the weak fault from shear sliding it needs to have a higher minimum stress and a lower shear stress that is the critically stressed weak fault maintains a higher minimum stress which explains why a low shear stress appears in the frictionally weak fault

permeability changes in coal analytical modeling abstract permeability changes can be very large during depletion of coalbed methane wells up to 100 times in the san juan basin analytic models of permeability increase during depletion are accessible easy to use and practical they are more transparent and less complicated than coupled numerical models however there are minor differences between the analytic models and these are reviewed here there are also discrepancies in attempting to match field data which is the final test of a model and these are discussed two different sets of san juan data have been modeled after suppressing the pressure dependent permeability with reasonably consistent reservoir parameters the matching parameters appear to be justifiable the small porosities do not seem to be ruled out by reservoir experts and the changes of elastic parameters including pore volume compressibility with depletion do not seem unreasonable the analytic models are used in reservoir simulators to model and predict injection of greenhouse gases in coal seams only when we can match the permeability increase of coalbed methane wells during depletion will we have the confidence to use the analytic models in reservoir simulators to match or predict sequestration of greenhouse gases such as co2

borehole stability analysis accounting for anisotropies in drilling to weak bedding planes abstract borehole instabilities pose significant challenges to drilling and completion operations particularly in regions with weak bedding planes and pre existing fractures where formations have strong anisotropies the bedding planes rock anisotropy and their impacts on horizontal stresses are considered in the proposed model to improve borehole stability modeling this improved model enables to calculate borehole failures and minimum mud weight along borehole trajectories with various drilling orientations versus bedding directions laboratory test data of rock compressive strengths are analyzed and a new correlation is developed to allow for predicting uniaxial compressive strengths in weak rocks from sonic velocities time dependent rock compressive strength is also examined to analyze the wellbore failure evolution with time the slip failure gradient in the weak planes is derived which can be used to model wellbore sliding shear failure in the planes of weakness the mud weight applied to prevent borehole shear failures in both intact rocks and ones with weak bedding planes can be obtained from the proposed model

distribution of oxygen and hydrogen isotopes in shallow groundwaters from southern india influence of a dual monsoon system oxygen and hydrogen isotopic investigation of groundwater and river water samples from the southern indian peninsula was undertaken to characterise the isotopic nature of the near surface water sources and provide basic framework for future hydrological studies it is assumed that the shallow groundwater retains the isotopic signature of the local precipitation averaged over a few tens of years except in a few cases where the same gets modified by post precipitation evaporation and or recharge contribution from surface water bodies therefore isotopic character of the groundwater can in principle be used to determine the relative influence of the different vapour sources contributing to the local regional precipitation and to characterise the modifications before groundwater recharge in the present context vapour sources for two rainy seasons namely southwest sw and northeast ne monsoon are respectively the indian ocean arabian sea and the asian continental sources together with the bay of bengal this study shows that i the regions dominated by ne monsoon have distinctly depleted isotopic composition compared to those dominated by sw monsoon ii the 18o d regression line slope of 6 in the east coast region is lower than that expected for local precipitation suggesting secondary evaporation iii the orography of the western ghats hill ranges plays a significant role in controlling the isotopic distribution along the west coast region iv the low d excess values in most part of study area indicate secondary evaporation v the high d excess values over the deccan plateau region in the nw part of the study area suggest admixture of recycled moisture with the inflowing oceanic vapour

probabilistic landslide susceptibility and factor effect analysis the susceptibility of landslides and the effect of landslide related factors at penang in malaysia using the geographic information system gis and remote sensing data have been evaluated landslide locations were identified in the study area from interpretation of aerial photographs and from field surveys topographical and geological data and satellite images were collected processed and constructed into a spatial database using gis and image processing the factors chosen that influence landslide occurrence were topographic slope topographic aspect topographic curvature and distance from drainage all from the topographic database lithology and distance from lineament taken from the geologic database land use from landsat thermatic mapper tm satellite images and the vegetation index value from spot hrv high resolution visible satellite images landslide hazardous areas were analyzed and mapped using the landslide occurrence factors employing the probability frequency ratio method using the all factors to assess the effect of these factors each factor was excluded from the analysis and its effect verified using the landslide location data as a result all factors had relatively positive effects except lithology on the landslide susceptibility maps in the study area

a numerical study on optimization of multilateral horizontal wellbore patterns for coalbed methane production in southern shanxi province china abstract china s southern shanxi province contains thick gassy coals of anthracite rank these high methane content higher than 500 ft 3 ton coals necessitate pre mining methane drainage to enhance the health and safety of underground coal workers both traditional vertical wells and multilateral horizontal wells which were shown to perform better have been drilled in the area in order to effectively reduce the gas content of coals however optimization of well drilling patterns is crucial to improve the gas drainage by boosting well performance and resulting in significant additional recovered gas in a cost effective manner in this study exploration borehole data from an undeveloped coalbed methane field in china s qinshui basin was obtained where permeability is expected to range from 0 1 to 10 md reservoir modeling conducted in this study concludes that in the presence of low permeability coals less than 1 0 md well patterns can be optimized to maintain high methane production rates in this work relationships to determine combinations of horizontal lateral spacing and permeability that yield similar production curves were developed in order to maximize production pinnate wells with laterals spaced at 600 ft intervals in reservoirs with 2 0 md permeability performed similar to those with 200 ft lateral intervals in 0 5 md reservoirs additional similar relationships were drawn for reservoirs ranging from 0 1 to 8 0 md furthermore because of the qinshui basin s potential high stress regime pitchfork and pinnate horizontal well patterns were analyzed based on their potential for catastrophic wellbore failure at well junctions and producing well branches analyses concluded that pitchfork wells had a significantly lower risk for significant wellbore loss due to borehole collapse while providing the opportunity for higher gas recovery in reservoirs exhibiting directional permeability

the effective stress law for stress sensitive transversely isotropic rocks abstract this paper first presents a review of the development of the concept of effective stress followed by major experimental and theoretical studies carried out to estimate the biot s coefficient it then uses the constitutive equations for vertically transverse isotropic vti reservoirs like coal derived using the principles of thermodynamics for estimation of the biot s coefficients in the vertical and horizontal directions laboratory data for tests conducted on two coal types retrieved from different geologic settings and geographical locations was used to carry out the modeling and validation exercise evidence is presented that values of biot s coefficient can be greater than one proposed by biot to be the limiting value for sorptive rocks to address this the term biot s coefficient is replaced with effective stress coefficient finally this paper discusses the pressure and stress dependent behavior of the biot s coefficient the results clearly show that the estimated values of biot s coefficients in both vertical and horizontal directions are different varying with pressure for methane depletion but remaining constant for helium depletion at the same time the nature of biot s coefficient re termed as effective stress coefficient was found to be greater than unity for methane depletion as a last step a conceptual physical model is proposed to explain the pressure dependent variation of effective stress biot s coefficients in terms of the contact area between grains based on the findings that the effective stress coefficient decreases with pressure it is concluded that the effective vertical stress would increase significantly with depletion which in turn would result in shear failure and increased permeability

shallow landslide susceptibility assessment in a semiarid environment a quaternary catchment of kwazulu natal south africa abstract this paper presents an evaluation of landslide susceptibility maps based on the frequency ratio fr landslide susceptibility index lsi logistic regression lr and artificial neural network ann methods applied within a quaternary catchment in the kwazulu natal region south africa landslide occurrence in this particular catchment is generally induced by heavy rainfall events where shallow landslips occur mostly on steep slopes thereby threatening informal housing at the base of slopes the scope of this study is to compare the performance of landslide susceptibility models and rate the importance of landslide causal factors thirteen landslide causal factors including altitude slope angle aspect slope total curvature slope plan curvature slope profile curvature proximity to stream network topographic wetness index twi lithology land cover proximity to faults proximity to dolerite sills and dykes and proximity to the road network were considered in the study furthermore each causal factor was rated according to the above mentioned methods and it was found that the most influential landslide causal factors are the altitude land cover and lithology the resulting susceptibility maps were classified into 5 classes ranging from very low to very high susceptibility model performance was tested using an independent validation set comprising 10 of all mapped landslides for verification of the models performance receiver operating curves rocs were calculated and the areas under curve auc for the success rate curves were 0 736 0 748 0 827 and 0 809 for fr lsi lr and ann respectively the findings revealed that models showed promising results for shallow landslide susceptibility modelling since they all give accuracy values higher than 73 the lr and ann methods however proved to be superior in representing landslide susceptibility throughout the study area

the effects of stress and fracturing on permeability of coal abstract this paper examines the changes in structure and permeability of coal under the stress conditions experienced around longwall faces the effect of fracturing on permeability of coal is discussed and the stress permeability relationship for fractured coal is compared with that of non fractured coal an empirical relationship between stress and permeability for coal is derived from the experimental data which relates the stress permeability behaviour of coal to its rank through the compressibility of the coal itself

a distributed slope stability model for steep forested basins a distributed physically based slope stability model dslam based on an infinite slope model a kinematic wave groundwater model and a continuous change vegetation root strength model is presented it is integrated with a contour line based topographic analysis and a geographic information system gis for spatial data extraction and display the model can be run with either individual rainfall events or long term sequences of storms these inputs can be either actual storm records or synthesized random events based on monte carlo simulation the model is designed to analyze rapid shallow landslides and the spatial distribution of safety factor fs in steep forested areas it can investigate the slope stability problem in both temporal and spatial dimensions for example the impact of timber harvesting on slope stability either at a given time or through an extended management period the probability of landslide occurrence for a given year and the delivery of landslide sediments to headwater streams the dslam model was applied in a steep forested drainage of cedar creek in the oregon coast ranges using actual spatial patterns of timber harvesting and measured rainfall during a major storm which triggered widespread landslides in that area in 1975 simulated volume and number of failures were 733 m3 and 4 respectively these values agreed closely with field measurements following the 1975 storm however the effect of parameter uncertainty may complicate this comparison for example when soil cohesion values of 2 0 and 3 0 kpa were used the failure volume changed by factors of 2 04 and 0 41 respectively compared with the average condition of 2 5 kpa used in the simulation for soil depths 30 higher and lower than the standard condition the failure volume changed by factors of 2 0 and 0 27 respectively when maximum root cohesion changed from 12 5 kpa average condition to 10 kpa the failure volume increased 1 73 fold for the case of 15 kpa the failure volume changed by a factor of 0 55 the simulated failures caused by the storm were mostly in hollows the simulations show that the spatial distribution of fs is controlled mainly by topography and timber harvesting patterns and is greatly affected by groundwater flow patterns during major rainstorms most areas with fs 3 0 corresponded with the distribution of blocks clear cut in 1968 and all elements with fs 2 0 were in areas clear cut in 1968 areas with low fs 1 0 1 6 expanded dramatically during the rainstorm and decreased at a slow rate after the storm factors of safety in hollows declined sharply during the storm

integrating borehole breakout dimensions strength criteria and leak off test results to constrain the state of stress across the chelungpu fault taiwan article the paper describes the computation of the maximum horizontal stress h magnitude in the vicinity of the chelungpu fault taiwan host of the slip zone during the chi chi earthquake mw 7 6 1999 the scientific hole b intercepts the chelungpu fault at 1136 m at the depths of logged breakouts 940 1310 m the vertical stress v as estimated from density logs increases linearly with depth from 22 to 31 mpa a series of leak off tests yielded two reliable shut in pressures 23 7 mpa at 1085 m and 29 8 mpa at 1279 m which are lower than the estimated v albeit by only 2 1 and 0 6 mpa respectively in our analysis the shut in pressures were considered to represent estimates of the least horizontal principal stresses h at the respective depths and consequently the test induced fractures were assumed to have been vertical principal stress directions had been previously determined by others 105 155 for the maximum horizontal stress h

reservoir simulation based modeling for characterizing longwall methane emissions and gob gas venthole production abstract longwall mining alters the fluid flow related reservoir properties of the rocks overlying and underlying an extracted panel due to fracturing and relaxation of the strata these mining related disturbances create new pressure depletion zones and new flow paths for gas migration and may cause unexpected or uncontrolled migration of gas into the underground workplace one common technique to control methane emissions in longwall mines is to drill vertical gob gas ventholes into each longwall panel to capture the methane within the overlying fractured strata before it enters the work environment thus it is important to optimize the well parameters e g the borehole diameter and the length and position of the slotted casing interval relative to the fractured gas bearing zones this paper presents the development and results of a comprehensive dynamic three dimensional reservoir model of a typical multi panel pittsburgh coalbed longwall mine the alteration of permeability fields in and above the panels as a result of the mining induced disturbances has been estimated from mechanical modeling of the overlying rock mass model calibration was performed through history matching the gas production from gob gas ventholes in the study area results presented in this paper include a simulation of gas flow patterns from the gas bearing zones in the overlying strata to the mine environment as well as the influence of completion practices on optimizing gas production from gob gas ventholes

geoelectric resistivity sounding of riverside alluvial aquifer in an agricultural area at buyeo geum river watershed korea an application to groundwater contamination study twenty profiles of vertical electric soundings ves were obtained in a riverside alluvium at the buyeo area south korea to examine the variations of subsurface geology and associated groundwater chemistry the combination of the ves data with the borehole data provided useful information on subsurface hydrogeologic conditions the vestige of an ancient river channel e g oxbow lake was identified on the resistivity profiles by the lateral continuation of a near surface perched aquifer parallel to the river such a perched aquifer is typically developed in the area with a clay rich silty surface alluvium which prohibits the infiltration of oxygen therefore groundwater below the oxbow lake shows a very low nitrate concentration and eh values under the strong anoxic condition the distribution of water resistivity is correlated with that of measured total dissolved solids concentration in groundwater while the earth resistivity of the aquifer shows a significant spatial variation it is interpreted that the earth resistivity of the aquifer is mainly controlled by the soil type rather than by the water chemistry in the study area

prediction of the occurrence of slope instability phenomenal through gis based hazard zonation slope instability hazard assessment is based on the analysis of the terrain conditions at sites where slope failures occurred in the past for the analysis of the causative factors the application of geographic information systems gis is an essential tool in the data analysis and subsequent hazard assessment three scale levels of hazard mapping are defined a direct experience driven mapping at reconnaissance level a statistical approach to determine the causative factors in a quantitative susceptibility mapping and a methodology at large scale making using of deterministic models

stability analyses of rainfall induced landslides the slope stability issues concerning rainfall induced slope failures are investigated and presented specifically the effect of both negative and positive pore water pressures on the stability of initially unsaturated slopes are carefully explained and coupled with infinite slope analysis methods in order to present a predictive formulation of slope failures that occur as a result of rainfall events the formulation serves as a baseline analysis method for evaluating potentially unstable soil slopes that are subject to surface infiltration and explains the various triggering mechanisms that may occur based on individual combinations of the slope geometry soil strength and infiltration parameters a procedural method is outlined for utilizing the analytical formulation to predict the change in the factor of safety for a slope subject to infiltration and a detailed analysis of a case study is presented to verify the method quantitative statements are made concerning the time and depth of failure in relationship to the soil slope and rainfall parameters

groundwater replenishment analysis by using natural isotopes in ejina basin northwestern china the ejina basin underlying complex aquifers is located in the lower reaches of the heihe river with an arid climate and 40 mm mean annual precipitation as the balance of the natural ecosystem in the ejina basin is fragile and easily upset it is very important to estimate and rationally use the limited groundwater resources to maintain the balance water samples were collected from the heihe river and wells for chemical and isotopic measurements across the basin the piper diagram gives two main types of hydrochemical features against the background of the regional geology combining isotope 18o tritium and chemical analysis with groundwater flows indicated by a shallow groundwater level contour map different kinds of groundwater sources and ways to replenish groundwater were discovered north of the study area are artesian wells that are replenished by the mountainous area at the boundary between china and mongolia replenishment for most of the groundwater resources of the gurinai oasis comes from the heihe river seepage flow of the highly conductive paleochannel not from the badain jaran desert as indicated by tds and tritium analysis the different groundwater ages which are younger than 35 years were approximately estimated by radioactive isotope tritium t by such efforts groundwater resources can be effectively evaluated with the engineering impact of the heihe river project

variation of in situ stress regime in coal reservoirs eastern yunnan region south china implications for coalbed methane production knowledge of in situ stress distribution is fundamental for coalbed methane production however it is poorly understood in the eastern yunnan region south china in this study the horizontal maximum shmax and minimum shmin principal stress and vertical stress sv were systematically analyzed for the first time the results indicated that the magnitudes of shmax shmin and sv showed positive correlations with burial depth in general three types of in situ stress fields were determined 1 shmax sv shmin in shallow layers with burial depths less than approximately 600 m 1970 ft below ground level bgl indicating a dominant strike slip faulting stress regime 2 in medium layers approximately 600 800 m 1970 2625 ft bgl the in situ stress state followed multiple relationships suggesting that the in situ stress regime was transformed and 3 sv shmax shmin in deep layers with burial depths greater than approximately 800 m 2625 ft bgl indicating a dominant normal faulting stress regime coal permeabilities obtained from injection falloff well tests showed that they were widely distributed and no obvious relationships were found between coal permeability and effective in situ stress magnitude in the study area the development and orientation of previously generated natural fractures combined with the present day in situ stress distribution controlled the permeability in coal reservoirs differential stress and presence of natural fractures significantly affected the geometry and pattern of hydraulic fractures in addition in the eastern yunnan region locations with relatively deep depths in vertical wells and approximately west northwest east southeast trending horizontal wells suffered high potential of borehole instability because of the high differential stress

horizontal stress anisotropy and effective stress as regulator of coal seam gas zonation in the sydney basin australia abstract coal seam gas zonation in the sydney basin nsw australia is related to basin hydrodynamics and hydrochemical facies evolution along the flow path from the subcrop to the basin center biogenic methane corresponds with meteoric water under hydrostatic pressure and persists down to the top of the geopressured zone 800 to 1000 m thermogenic gases including wet hydrocarbons can reach up to relatively shallow horizons of less than 500 600 m depth in the transition zone between the top of the geopressured and base of the hydrostatic zone a mixed water and gas regime prevails comprising brackish waters and gases of mixed biogenic thermogenic and inorganic origins including co 2 mechanisms for and the role of stress in the development of this layered hydrogeological and gas environment are investigated in this paper the inverse relationship between effective horizontal stress and permeability in coals through regulation of cleat volumes is well documented and there is evidence of regionally compartmentalized stress regimes with depth within the sydney and other eastern australian coal basins this regional stress regime can be overprinted by the effect of localized geological features it is hypothesized that the in situ stress regime plays an important role in the regulation of groundwater flow regimes and extents resulting in the development of the reported gas content and compositional zonation analysis of regional gas and stress data obtained from public and private databases as well as literature supports this hypothesis changes in gas concentration and composition with depth correspond with discernable variations in horizontal stress anisotropy gas contents generally increase with depth down to a peak gas horizon below which concentrations decrease this peak gas zone is coincident with a horizontal stress anisotropy change from moderately high to low levels associated with reverse to strike slip faulting conditions respectively the stress release zone also marks the top of the thermogenic gas zone identified by the first appearance of ethane in the vertical profile this zone also hosts gases of mixed origins biogenic thermogenic and inorganic co 2 and represents a mixed transitional groundwater flow environment the base of the mixed gas zone is the top of the geopressured only flow associated with thermogenic gases and is signaled by the return to high stress reverse faulting conditions below 850 900 m depth in the sydney basin

a multi method approach to study the stability of natural slopes and landslide susceptibility mapping abstract in this paper a multi method approach for the assessment of the stability of natural slopes and landslide hazard mapping applied to the dakar coastal region is presented this approach is based on the effective combination of geotechnical field and laboratory works of gis and of mechanical deterministic and numerical stability analysis by using this approach valuable results were gained regarding instability factors landslide kinematics simulation of slope failure and coastal erosion this led to a thorough assessment and strong reduction in the subjectivity of the slope stability and hazard assessment and to the development of an objective landslide danger map of the sw coast of dakar analysis of the results shows that the slides were influenced by the geotechnical properties of the soil the weathering the hydrogeological situation and the erosion by waves the landslide susceptibility assessment based on this methodological approach has allowed for an appropriate and adequate consideration of the multiple factors affecting the stability and the optimization of planning and investment for land development in the city

landslide hazard zoning using the gis approach a case study from the ramganga catchment himalayas abstract this paper deals with the development of a technique for risk assessment of landslide hazards using the geographic information system gis approach the method has been applied to the ramganga catchment lying in the lower himalayas and the investigations are based on multi data sets the landslide activity is related to a number of parameters viz lithology land use distance from major tectonic shear zone and azimuth direction based on the data for 522 landslides in four selected sub basins an index value called landslide nominal risk factor lnrf is defined and developed for each of the important factors different weights have been assigned to the terrain depending upon the lnrf and integrated in an ordinal scale to help locate areas of high moderate and low landslide risk

the present day in situ stress field within coalbed methane reservoirs yuwang block laochang basin south china abstract understanding in situ stress variation is extremely important for coalbed methane cbm exploration and development however precise information on the present day in situ stress field in the yuwang block of laochang basin is unclear in the present study the horizontal maximum shmax and minimum shmin principal stress and vertical stress sv in coal seams of yuwang block were systematically analyzed based on measured injection falloff data and geomechanical models the results indicated that in the yuwang block vertically shallow coal seams less than 800 m below ground level bgl mainly experienced the strike slip faulting stress regime shmax sv shmin whereas deep layers more than 800 m bgl were characterized by the dominant normal faulting stress regime sv shmax shmin laterally with the no 9 coal seam case study relatively lower stress magnitudes were mainly located around yuwang and well l 4 regions coal permeability obtained from injection falloff well tests decreased exponentially with the increased effective stress suggesting that coal permeability in the yuwang block was in situ stress controlled in addition differential stress and presence of natural fractures within coal seams significantly affected the geometry and pattern of hydraulic fractures in coal seams of yuwang block the present day in situ stress field contributed to generate complex hydraulic fracture networks the study results provided geological references for cbm development in the yuwang block of laochang basin

combined use of tracer approach and numerical simulation to estimate groundwater recharge in an alluvial aquifer system a case study of nasunogahara area central japan summary in this study we simulate the spatial and temporal distribution of groundwater recharge in an alluvial aquifer system in the nasunogahara area of japan natural stable isotopes 18 o d were considered as additional calibration targets in a numerical model the reliability of the model outputs was further validated by comparing the results from the numerical simulation and an independent tracer approach the results indicated that the calibrated model can effectively simulate the spatial and temporal characteristics of the contribution ratios of recharge sources to groundwater in the nasunogahara area however the tracer approach i e end member mixing analysis provided more reliable results at point scale particularly for the estimated contribution ratios of paddy field water the precipitation in the nasunogahara area is the major recharge source its mean contribution ratio is 58 for a one year period over the entire alluvial fan river seepage is significant in the upstream area of the alluvial fan and the contribution ratio of river waters along the river channels in the upstream area increases during the wet season paddy field water is a highly important recharge source in the midstream and downstream areas of the alluvial fan and the contribution ratio of paddy field water obviously increases from dry season to wet season because of irrigation this study demonstrates that combined use of the tracer approach and numerical simulation with stable isotopes as additional calibration targets can eliminate their respective limitations and can assist in better understanding the groundwater recharge mechanism in alluvial aquifer systems

probabilistic landslide hazard assessment at the basin scale abstract we propose a probabilistic model to determine landslide hazard at the basin scale the model predicts where landslides will occur how frequently they will occur and how large they will be we test the model in the staffora river basin in the northern apennines italy for the study area we prepare a multi temporal inventory map through the interpretation of multiple sets of aerial photographs taken between 1955 and 1999 we partition the basin into 2243 geo morpho hydrological units and obtain the probability of spatial occurrence of landslides by discriminant analysis of thematic variables including morphological lithological structural and land use for each mapping unit we obtain the landslide recurrence by dividing the total number of landslide events inventoried in the unit by the time span of the investigated period assuming that landslide recurrence will remain the same in the future and adopting a poisson probability model we determine the exceedance probability of having one or more landslides in each mapping unit for different periods we obtain the probability of landslide size by analysing the frequency area statistics of landslides obtained from the multi temporal inventory map assuming independence we obtain a quantitative estimate of landslide hazard for each mapping unit as the joint probability of landslide size of landslide temporal occurrence and of landslide spatial occurrence

discussion on integrating borehole breakout dimensions strength criteria and leak off test results to constrain the state of stress across the chelungpu fault taiwan abstract the in situ stress computations presented by haimson et al 2010 overestimated the maximum horizontal stress in the vicinity of the chelungpu fault taiwan our analyses from extended leak off tests drilling induced tensile fractures and anderson s faulting theory show considerable lower values for the maximum horizontal stress our results suggest that closer to the ruptured fault more s h is released implying a strong earth crest in the shallower section which is far away from the ruptured fault however it would require more detailed and intensive work in order to achieve an accurate interpretation of the in situ stress in this region

characteristics of natural fractures in the upper paleozoic coal bearing strata in the southern qinshui basin china implications for coalbed methane cbm development abstract natural fractures as the effective storage space and fluid flow pathway of hydrocarbons play a critical role in the exploration and development of unconventional gas resources in the coal bearing strata in the present study to reveal the effects of natural fractures on coalbed methane cbm preservation and development the types origins and development characteristics of natural fractures in the upper paleozoic permian shanxi formation in the southern qinshui basin were systematically described and analyzed based on outcrops cores borehole image logs thin sections and sem four types of natural fractures have been identified in the shanxi formation according to their geologic origins including the endogenic fractures cleats and exogenous fractures in the no 3 coal seam and tectonic fractures and diagenetic fractures in its roof and floor tectonic fractures can be further divided into small faults intraformational shear fractures intraformational open fractures and slip fractures while diagenetic fractures are mainly bed parallel fractures the statistical results show that the development and distribution characteristics of those types of fractures are significantly different which are mainly influenced by lithology layer thickness and geological structure further natural fractures with different types and distributions show different influences on cbm preservation and well productivity exogenous fractures can effectively improve the seepage capability of coal reservoirs and are conducive to cbm wells productivity whereas endogenic fractures have less contributions to coal permeability due to their poor effectiveness the intraformational open fractures in the fold axis zones and intraformational shear fractures and small faults in the fault zones are generally excessive developed those fractures may result in gas dissipation and external water supplement which have negative effects on cbm preservation and production however moderate developed intraformational shear fractures in the sandstone roof can favorably affect the pressure reduction of coal reservoir and improve the recovery potential of unconventional gas resources these investigations may serve as a geological basis for unconventional gas exploration and development of the upper paleozoic coal bearing strata in the southern qinshui basin

economic coalbed methane production in the canadian foothills solving the puzzle abstract the producibility of methane at economic rates from thick and very gassy coals in the canadian foothills and mountains remains a major challenge these structurally deformed and often sheared coals are generally characterized by low permeabilities which is the main limiting factor restricting the flow of gas through natural fractures a preliminary evaluation of the cleating in the coals and of the jointing in the interburden clastics was carried out in the elkview mine of se british columbia field observations were supplemented by microscopic evidence on coal microtextures produced by shearing and their impact on coal permeability permeability of the coals tested at simulated in situ stress conditions and parallel to bedding surfaces was highly variable ranging from 2 09 md in seam 3 greenhills mine to less than 0 001 md in the sheared seam 10 elkview mine this variation may be rationalized based on variations in maceral composition stress history degree of shearing and the mode of deformation of the coal seams in these tectonically complex regions shearing gave rise to a variety of complex textures in coal such as slickensides shear cones and striated features small scale thrusts in the hangingwall and brittle and ductile microtextures furthermore the coal seams act as aquitards to the flow of water most likely because of low permeability water flow occurs at the contact between coal and interbedded coarser clastics and within the highly fractured and jointed sandstone units the cone of effective depressurization required for coal gas drainage to occur in the study area is influenced by a the development of a joint system in the more competent clastic beds that would provide the high permeability pathways for water and gas and b the ability of the rocks above the coals to re pressurize as a result of either surface recharge or water flow both laterally and vertically within the succession therefore multidisciplinary studies of hydrology coalification history and structure would help increase our understanding of the mechanisms and timing of cleat development effect of shearing on coal permeability and presence of systematic fractures in the non coaly lithologies

the characteristics of coal reservoir pores and coal facies in liulin district hedong coal field of china the composition rank coal facies and coal pore structure characteristics of 15 coal samples were investigated systemically using methods of lithotype analysis maceral analysis proximate analysis mercury porosimetry analysis and nitrogen adsorption analysis these samples were directly collected from the working faces of no 4 8 9 seams in liulin district eastern margin ordos basin china four types of paleoenvironment including a wet forest swamp an intergradation forest swamp a drained forest swamp and a fresh water peat swamp were distinguished by lithotype and merceral analysis an r cluster analysis was performed to demonstrate the correlations between the coal facies and the pore structures the results showed that coal rank is the primary factor affecting the development of micropores and transition pores whereas coal facies control the development of seepage pores in similar coalification conditions especially in a local district and in a seam this work suggests that the vertical variations observed in coal properties macerals vitrinite reflectance mineral matters porosity bet specific area pore size distributions and pores connectivity were controlled by groundwater level fluctuations indicated by variations in the ground water index gwi in the ancient mires due to different accommodation and peat accumulation rates comparison of the porosity characteristics of various coal reservoirs developed in various coal facies indicates that wet forest swamp facies is favorable to the formation of a coalbed methane reservoir because of reasonable pore structure and good connectivity intergradation forest swamp facies rank the second and drained forest swamp facies are less advantageous

groundwater geochemistry of a nitrate contaminated agricultural site groundwater samples were collected from several soil depths down to 50 m below soil surface to investigate vertical profiles of no3 and hydrogeochemical characteristics of the experimental site the experimental site is located in the shimabara city nagasaki japan where nitrate contamination in groundwater is severe due to intensive agricultural production a transition zone regarding dissolved ions was found between specific depths caused by differences in the permeability of soil layers though no3 concentration decreased significantly in the transition zone the entire soil depth exceeded permissible levels 50 mg l 1 for drinking purposes comparing the temporal no3 fluctuation above the transition zone with that of the below distinct fluctuations were observed depending on sampling campaign high rainfall amounts typically lead to initial decrease in no3 concentration for the shallow groundwater after some time however increase in no3 concentration occurred due to leaching of accumulated no3 in the soil matrix this indicated that temporal no3 fluctuation is mainly controlled by natural impact and occurring crop system results of principal component analysis suggested that application of chemical fertilizers nh4 2so4 nh4no3 and kcl dissolution of minerals feldspar calcite and dolomite and ion exchange are the predominant factors resulting in the observed vertical groundwater chemistry the relative magnitude of these three principal component scores changed across the transition zone below the transition zone groundwater geochemistry reflected application of nh4no3 and kcl fertilizer and dissolution of albite and orthoclase less

dynamic variation effects of coal permeability during the coalbed methane development process in the qinshui basin china abstract the commercial exploitation of coalbed methane cbm has been achieved in the qinshui basin china however the productivity of wells varies greatly because of their different geological settings and production rules and the permeability damage to coal reservoirs caused during the development process is one of the most important factors affecting productivity in this study the patterns of permeability variation in coal seam no 3 and their influence on cbm recovery were analyzed and the degree of permeability damage caused by different factors was calculated the results show that the burial depth the bottom hole pressure and the dewatering rate affected the effective stress imposed on the coal reservoir which further induced changes in permeability and productivity the elastic modulus of the coal body reflects its ability to withstand compression the greater the elastic modulus is the less the permeability decreases when the pressure drops from 7 05 mpa to 0 20 mpa the relatively low elastic modulus of coal seam no 3 can cause a 10 decrease in permeability coals at different burial depths have different formation pressures and elastic moduli causing different levels of permeability damage during the development process calculations indicate that the absolute permeability will decrease by 5 5 and 14 3 at depths of 500 m and 1000 m respectively if the bottom hole pressure drops too fast or the dewatering rate is too high there will be a strong stress response resulting in decreasing permeability and productivity this study found that in high productivity wells a larger pressure drop approximately 0 022 mpa d and stroke 3 0 min are favorable in the early drainage period but a smaller pressure drop 0 002 mpa d and stroke 0 4 min should be applied when the gas peak appears

the effects of magma intrusion on localized stress distribution and its implications for coal mine outburst hazards abstract magma intrusions into coal seams are common throughout the world the high temperatures and pressures induced by magma intrusion can alter the properties of coal including its rank mechanical properties cleat and pore structures and adsorption desorption behaviors because the thermal properties of magma intrusions also affect localized in situ stress distributions both the alteration of coal properties and changes in stress distribution can directly influence coal seam gas outburst disasters this phenomenon was recently observed and confirmed by several outbursts in the haizi coal mines of huaibei china in this paper the processes and mechanisms of this magma intrusion are comprehensively analyzed based on an integrated data set including previously published geological data in house laboratory tests and field observations the results demonstrate that there is an intrinsic relationship between the intrusive sill and the subsequent in situ stress distribution these data suggest that the magma intrusion in the haizi coalfield originated as a crust mantle type controlled by magmatic underplating later transported mantle derived magma successively along the tanlu fracture belt the subei fault and the daliujia fault and finally intruded into the coalfield as a thick sill by comparing the lithologies of the coal seam roof and floor as well as the distances between key coal seams no 3 and no 7 it was discovered that the magma intrusion that entered the no 5 coal seam was also associated with erosional effects the squeezing that occurred during this intrusion changed the in situ stress distribution within the region which increased along with the increasing thickness of the overlying sill therefore the increased in situ stress also caused an increase in the outburst risk of the underlying coal seam a conclusion that was verified by measuring the quantity of drilling cuttings on working faces as well as onsite outburst events

coal strength and young s modulus related to coal rank compressional velocity and maceral composition abstract this paper presents an experimental investigation of coal rank and maceral composition influences on the coal mechanical behaviors the complete stress strain behavior uniaxial compressive strength young s modulus and acoustic compressional velocity were measured and correlated to coal ranks and microstructures the test results show that coal is an elasto brittle geo material and its uniaxial compressive strength and young s modulus increase as coal rank increases this occurs because as vitrinite reflectance or coal rank increases coal has less microporous structure and thus higher uniaxial compressive strength therefore using vitrinite reflectance value instead of vitrinite content is advantageous for correlating coal strength the experimental results also demonstrate that compressive strength and young s modulus have positive exponential correlation even for different types of coal therefore the compressive strength of coal is highly related to its young s modulus the uniaxial compressive strength and acoustic compressional velocity of coal are also correlated but a single correlation does not exist for different coal ranks instead different relationships occur for different types of coal

in situ stress pore pressure and stress dependent permeability in the southern qinshui basin this study focuses on the in situ stress pore pressure and permeability in the southern qinshui basin one of largest coalbed methane basins in china well tests show that permeability in this basin is higher than other coalbed methane reservoirs this is because it is located in an extensional basin where the normal faulting stress regime is dominated this in situ stress regime is advantageous to keep coal cleats open hydraulic fracturing tests indicate that the fracture gradient or minimum horizontal stress is much lower than the shales in the gulf of mexico and other oil basins the minimum horizontal stress model is proposed with consideration of the stress coefficient based on the uniaxial strain method this model provides a fairly good prediction on the minimum stress permeability data show that the effective stress dependent permeability is pronounced in the coalbed methane reservoir this is significant for the dual porosity and dual permeability coal reservoirs which consist of coal porous matrices and cleats the reason is that a rapid increase in effective stress can induce the closure of cleats which may cause a permanent loss of permeability in the cleats this reduces the connectivity between the cleats and coal matrices hence the coal matrices cannot deliver gas pressure to the cleats for supporting the cleat space therefore slowing down the effective stress change during production e g slowing reservoir drawdown can decelerate the permeability reduction this is particularly important for the reservoir in which the pore pressure is not significantly overpressured such that in the southern qinshui basin

formation of fractured zones in overburden due to longwall mining the fractured zones caused by mining were studied in the overburden of the torezko snezhnyanskaya area ukraine through the change in natural gas emission from these zones during longwall coal excavation zones of interconnected fractures and separate horizontal fractures were studied with vertical wells drilled from the ground surface down to active underground workings the maximum heights of the zone of interconnected fractures and separate horizontal fractures may reach 19 41 and 53 92 times the thickness of the coal seam respectively it was found that the ratio between the maximum height of the zone of interconnected fractures and the thickness of the extracted coal seam increases with the increasing number of rock layer interfaces and decreases with the increasing stiffness of immediate roof it is shown that the growth of the zone of interconnected fractures occurred during 17 39 days at an average rate of 0 94 1 97 m day 1 and it was accompanied by increasing methane emission from overburden observation shows that the formation of separate horizontal fractures began only 11 49 5 days after the height of the zone of interconnected fractures reached its maximum value formation of separate horizontal fractures in overburden over the longwall excavation occurred as a stepped process from lower to upper sandstone sandy shale layer interfaces in the direction of the ground surface

coalbed methane from hazard to resource abstract coalbed gas which mainly consists of methane has remained a major hazard affecting safety and productivity in underground coal mines for more than 100 years coalbed gas emissions have resulted in outbursts and explosions where ignited by open lights smoking or improper use of black blasting powder and machinery operations investigations of coal gas outbursts and explosions during the past century were aimed at predicting and preventing this mine hazard during this time gas emissions were diluted with ventilation by airways e g tunnels vertical and horizontal drillholes shafts and by drainage boreholes the 1970 s energy crisis led to studies of the feasibility of producing the gas for commercial use subsequent research on the origin accumulation distribution availability and recoverability has been pursued vigorously during the past two decades since the 1970 s research investigations on the causes and effects of coal mine outbursts and gas emissions have led to major advances towards the recovery and development of coalbed methane for commercial use thus coalbed methane as a mining hazard was harnessed as a conventional gas resource

comparison of genesis and geostatistical methods for characterizing the heterogeneity of alluvial media groundwater flow and transport simulations abstract we describe a new method for generating the sediment heterogeneity of alluvial deposits based on a genesis model which mimics some of the hydraulic rules by which meandering or braided streams deposit or erode sediments the new model is described and compared with other approaches and is then applied to a 5 4 1 4 km 2 reach of the aube river upstream of paris the model is based on data obtained from a single cross section of the alluvial plain with 44 auger holes along the 1 4 km stretch of the plain as the model describes the sediment facies we assign to each facies an assumed hydraulic conductivity flow and transport simulations are then made with the commonly used code modflow in order to compare the results with simulations based on other descriptions of heterogeneous media we then use classical geostatistical tools indicator simulations to generate alternative images of the same medium based on the same initial data and the same assumptions on the hydraulic conductivity of each facies finally an equivalent uniform medium obtained through permeability upscaling is also generated comparing these three approaches on the basis of the flow and transport results we show the intrinsic capacity of the new model to generate more realistic flow and transport processes in heterogeneous alluvial media where permeability barriers and buried channels dominate the spatial distribution of heterogeneities

identification of groundwater recharge sources and processes in a heterogeneous alluvial aquifer results from multi level monitoring of hydrochemistry and environmental isotopes in a riverside agricultural area in korea we evaluated sources and pathways of groundwater recharge for a heterogeneous alluvial aquifer beneath an agricultural field based on multi level monitoring of hydrochemistry and environmental isotopes of a riverside groundwater system at buyeo korea two distinct groundwater zones were identified with depth 1 a shallow oxic groundwater zone characterized by elevated concentrations of no3 and 2 a deeper 10 14 m from the ground surface sub oxic groundwater zone with high concentrations of dissolved fe silica and hco3 but little nitrate the change of redox zones occurred at a depth where the aquifer sediments change from an upper sandy stratum to a silty stratum with mud caps the 18o and 2h values of groundwater were also different between the two zones hydrochemical and 18o 2h data of oxic groundwater are similar to those of soil water this illustrates that recharge of oxic groundwater mainly occurs through direct infiltration of rain and irrigation water in the sandy soil area where vegetable cropping with abundant fertilizer use is predominant oxic groundwater is therefore severely contaminated by agrochemical pollutants such as nitrate in contrast deeper sub oxic groundwater contains only small amounts of dissolved oxygen do and no3 the 3h contents and elevated silica concentrations in sub oxic groundwater indicate a somewhat longer mean residence time of groundwater within this part of the aquifer sub oxic groundwater was also characterized by higher 18o and 2h values and lower d excess values indicating significant evaporation during recharge we suggest that recharge of sub oxic groundwater occurs in the areas of paddy rice fields where standing irrigation and rain water are affected by strong evaporation and that reducing conditions develop during subsequent sub surface infiltration this study illustrates the existence of two groundwater bodies with different recharge processes within an alluvial aquifer copyright 2009 john wiley sons ltd

deformation failure and permeability of coal bearing strata during longwall mining abstract to mitigate water shortage a few groundwater reservoirs are being built at the daliuta coal mine shaanxi province china it is essential to investigate the deformation failure and permeability of coal bearing strata during longwall mining and their influences on the construction of groundwater reservoirs in this paper the local geology was introduced briefly and the complete stress strain and permeability for different rock samples were investigated using laboratory experiments and then a three dimensional coupling model between stress and permeability was proposed after that a series of numerical simulation was performed to investigate the dynamics of stress permeability coefficient using flac3d it turns out that due to the relatively low mechanical strength of the coal bearing strata at the daliuta coal mine there are only two zones above the goaf that is caving zone and fracture zone and the fracture zone extends directly to the surface the rock mass permeability is closely related to the stress strain and the permeability decreases with the rise of stress in the stage of elastic deformation while it increases significantly in the stages of plastic deformation and failure the maximum value of permeability coefficient appears in the stage of strain softening and the value varies greatly with the rock lithology during the advancement of longwall face the redistribution range is much wider for permeability than for rock failure and the permeability is the largest on the periphery of goaf rock mass with increased permeability is horizontally oval shaped and vertically saddle shaped the permeability of coal seam roof and floor experiences three stages decrease increase and gradual recovery during coal mining the results are in good agreement with those of physical modeling and field observation the outcomes may contribute to the site selection and construction of the groundwater reservoir at the daliuta coal mine

production characteristics and the key factors in high rank coalbed methane fields a case study on the fanzhuang block southern qinshui basin china abstract the temporal and spatial production characteristics of coalbed methane cbm wells in the fanzhuang block of the southern qinshui basin the first commercial cbm producing basin in china were studied to determine the dominant factors the study indicates that gas production differs significantly in different wells adjacent to or located in different tectonic areas in combination with the production characteristics in the temporal and spatial variations the impact of seven factors burial depth thickness of coal gas content porosity permeability effect of fracturing structural setting and hydrogeological conditions on the gas production was analyzed based on bivariate correlation analysis and gray system theory which are suitable for solving the complex interrelationships between multiple factors and variables the results indicate that hydraulic fracturing is an effective guarantee of high production cbm wells in the first several months during a high rank cbm field development however the effect of hydraulic fracturing on enhancing the gas production of cbm wells decreases with time because the initial reservoir permeability lower than the hydraulic fracture permeability limits the adsorption diffusion and flow of cbm this limitation inevitably leads to a slow gas production rate when the adsorbed cbm from the initial reservoir becomes the main gas source instead of the fracturing affected zone gas content and permeability are two key factors that dominate cbm well productivity because they perform elementary roles in controlling the volume of gas sources and conductivity respectively the structural setting and hydrogeological condition are also two important factors that dominate cbm well productivity because they can influence the spatial distribution of permeability and gas content as well as other factors such as aquifers

application of seismic curvature attributes in the delineation of coal texture and deformation in zhengzhuang field southern qinshui basin coal texture refers to the in situ particle size morphological characteristics and structural components of coal beds and it determines the permeability and producibility of a coalbed methane cbm reservoir coal texture is commonly classified into undeformed coal with primary coal texture and deformed coal with increasing degree of deformation including cataclastic coal granulated coal and mylonitized coal geophysical logging has recently been proven effective for detecting coal texture in boreholes but it is inefficient for establishing a regional distribution where there have been only limited amounts of drilling in contrast seismic attributes have high lateral extent and an advantage in terms of characterizing fine structures even minor faults with throws of 2 3 m and other strata deformations by comparing seismic curvature data to the results of 221 core samples from the zhengzhuang field in the southern qinshui basin we provide a seismic curvature attribute based coal texture evaluation method evaluation of the results shows that the coal texture types of the no 3 coal seam include undeformed coal cataclastic coal and some granulated coal the undeformed coal is mainly located in the western and northwestern parts of the study area the cataclastic and granulated coals are mainly distributed in the southern and eastern parts of the study areas the permeability of no 3 coal seam is weakly correlated with undeformed coal and it has a high negative correlation with deformed coal permeability has a strong negative correlation with the maximum curvature attribute of the no 3 coal seam it is suggested that the in situ stress distribution combined with the curvature controlled the local development of the coal texture types and thus resulted in regional differences in permeability finally the distribution characteristics of coal textures of no 3 coal seam in the study area are divided into four types in which the undeformed cataclastic coal dominated area located in the midwestern part of the study area is the most favorable area for cbm production

engineering geomorphology of the widentobel catchment appenzell and sankt gallen switzerland a geomorphologuical inventory system applied to geotechnical appraisal of slope stability abstract the paper presents a method of applied and detailed 1 2000 scale geomorphological and geotechnical surveying developed in alpine areas and tested to its engineering consulting value in the widenbach valley appenzell and st gallen switzerland the investigation was carried out by a pair of geomorphologists trained in high relief terrain and well versed in mass movement characteristics a programme of wildbachverbauung the controlling of fluviatile erosion by the erection of dams was already undertaken in the twenties but this first generation of wooden dams is now being replaced by concrete constructions the widenbach valley situated in the marls and sandstones of the folded molasse zone untere susswasserzone was subjected to glacial scouring and deposition by a branch of the rhine glacier transfluencing westwards across the stosspass separating the widenbach valley at 940 m a s l from the appenzell depression postglacially various earthflows have originated from the instable morainic deposits as well as from the weathered marls and sandstones underlying the glacially oversteepened valley flanks they have built a two km long earthflow complex filling the widenbach valley to considerable depth the townships of eichberg and altstatten situated at the outlet of the system have since historic times experienced damage to forest and grazing land houses and roads in the midstream and upstream valley sections the widenbach is flowing on the earthflow morphology while the downstream part already constrained by new dams founded in exposed hard rock is controlled by fluvial processes the mass movement dynamics of the midstream and upstream sectors make a completely different engineering approach necesssary when this was made clear by the geomorphological reconnaissance the lack of data could only be filled by a detailed 1 2000 scale geomorphological site investigation as time and funds for long lasting monitoring of the earthflow system were not available this geomorphological survey contained the following elements pre field airphoto interpretation mapping of micro terrainforms classification of materials types and order of movement it placed emphasis on the behaviour of the various discontinuity planes expressed in the terrain

geologically controlled agricultural contamination and water rock interaction in an alluvial aquifer results from a hydrochemical study hydrogeochemistry data collected from three multi level monitoring wells in a sandy alluvial aquifer located in the keum river watershed south korea are used in this study to evaluate groundwater chemistry change in relation to geologic controls of groundwater recharge redox condition water rock interaction and contamination susceptibility a silt layer at a depth of about 10 m is a hydrologic barrier which prohibits the continued downflow of groundwater and divides the groundwater into two distinct masses i e shallow oxic groundwater and deeper sub oxic groundwater with different redox states and ion chemistry compared to sub oxic water oxic water has lower sio2 na k and higher ca no3 and so4 indicating significant contamination from agrochemicals and manures the higher ca and no3 but lower hco3 concentrations in oxic water result from lime dissolution and nitrification in contrast sub oxic water shows increased sio2 and hco3 suggesting the effect of water rock interaction in the aquifer potential sources of cations are na from albite mg from chlorite and illite and k from illite vertical fluctuations of cationic composition in sub oxic water suggest heterogeneity of aquifer mineralogy with depth mineral stability calculations show that the chemistry of oxic water plots in the kaolinite field while that of sub oxic water plots in the ca montmorillonite field and near the kaolinite montmorillonite equilibrium boundary concentrations of dissolved inorganic carbon dic in sub oxic water are much higher than total alkalinity hco3 co3 suggesting that co2 generated by redox reactions such as denitrification iron reduction and sulfate reduction causes increasing dic which also affects the dissolution of silicate minerals in an aquifer free of carbonate minerals

identification of coal structures using geophysical logging data in qinshui basin china investigation by kernel fisher discriminant analysis abstract coal structure is closely related to the porosity and permeability of coal reservoirs which not only affects the enrichment of coalbed methane cbm but also influences the hydraulic fracturing and efficient development of cbm the accurate identification of the coal structure would be a critical issue in cbm exploration and development and is always a challenge compared with traditional methods for identifying coal structure base on borehole cores or mining seam observation geophysical logging has become the most economic and efficient technique several linear correlations have been established to describe the relationships between the coal structures and well logs however those correlations cannot accurately reflect nonlinear relations between them therefore a reliable and efficient method to identify coal structure is needed as a powerful nonlinear classifier the kernel fisher discriminant analysis kfd method has been widely used due to its strong generalization ability in this paper a new quantitative coal structure identification model was developed based on the kfd method by using geophysical logging data the model was trained tested and optimized using 178 logging data sets from 15 cbm wells in qinshui basin china the approach accounted for all the available well logging attributes and the training data sizes and kernel parameters were analyzed to get the most appropriate model in practice in addition the built model was validated individually by employing logging data of a new cbm well the results indicate that the kfd based identification model has high prediction accuracy which can be used as a reliable method for coal structure identification the kfd method exhibits strong capability during the modeling and generalization in the determination of nonlinear relationships which provides an efficient way for the coal structure prediction in basic research of coal reservoirs

slope unit based approach for assessing regional seismic landslide displacement for deep and shallow failure abstract grid based approach is typically adopted to estimate the newmark type displacement for regional seismic landslide hazard assessment however the approach is limited to the assumption of infinite slope and rigid block movement which may be different from the actual behavior of slope under seismic loading in this study a slope unit based approach is proposed to quickly estimate earthquake induced displacements for finite slopes in regional scale hence regional seismic landslide hazard can be assessed by the estimated displacements the approach is advantageous as it considers slope geometry determines the failure mode automatically and considers the interaction of incident wave and slope the implementation of the approach is demonstrated by considering two areas that experience severe landslides during the chi chi and northridge earthquakes results show that the prediction rate of the proposed method is up to 73 compared with the landslide inventory given the estimated displacements

experimental research on the permeability of high rank coal under a varying stress and its influencing factors abstract in order to investigate the permeability behavior of high rank coal during early depletion of cbm and its influencing factors we collected 14 coal samples from ordos basin in northwest china and determined their air permeability under a varying effective stress of 2 5 20 mpa in laboratory we used effective confining pressure to simulate effective stress it turns out that high rank coal permeability is susceptible to effective stress permeability of coal samples declines exponentially with the rise of effective stress on the whole when effective confining pressure variation ranges from 2 5 mpa to 10 mpa permeability varies dramatically when effective confining pressure rises to above 10 mpa the curve of permeability decline gets gentle and the stress sensitivity becomes relatively weak coal permeability is also affected by coal moisture maceral fracturing and metamorphism degree permeability rises with the increase of vitrinite content and fracturing degree and decreases with the increase of moisture content permeability of wet and fractured coal samples is more sensitive to effective stress than dry intact ones and the irreversible permeability loss rate of fractured coal cores is significant over 80 comparison of tests results of medium and low rank coal samples and high rank ones shows that the stress sensitivity coefficient decreases with the increase of the maximum reflectance of vitrinite if experiencing the same load relief process the irreversible permeability loss rate of low rank coal is less than that of medium and high rank coals

evaluation of coal texture distributions in the southern qinshui basin north china investigation by a multiple geophysical logging method abstract coal texture is indicative of coal mechanical strength which is important not only for evaluating coalbed methane cbm reservoir permeability but also for evaluating the possibility of coal and gas outbursts in underground coal mining this paper begins with a foundation of a geophysical logging based coal texture evaluation method that compares the digital logging data with the results from 108 coring samples then the method was applied to the analyses of coal textures in 39 cbm wells the results of which are discussed in terms of the vertical distribution of coal textures in the study area finally a ternary diagram based on thickness proportions of coal textures was used to identify reservoir compartments in the zhengzhuang field of the southern qinshui basin the results show that undeformed coals are easily distinguished from cataclastic and granulated coals because of the high den and gr of undeformed coals meanwhile cataclastic coal has lower response values of ac and lld than granulated coal which can be used in identifying cataclastic from granulated coal a multiple geophysical logging method combining the log data of den gr ac and lld was provided for predication of the coal textures in the zhengzhuang field the predicated results show that the coal seam can be vertically divided into three to eight sub layers with a typical interbedded pattern of undeformed and cataclastic coals on the upper and lower parts and granulated coal in the middle at a relatively large thickness the study area is divided into four major regions and 11 sub regions based on the classification of coal texture types the undeformed coal dominated region is located in the southwestern part of the study area indicating a low permeability in the coal reservoir the granulated coal dominated region is mainly in the northern and eastern parts of the study area and has resulted from deep burial and multi period structural activities the cataclastic coal dominated region is in the middle of the study area the coal reservoir in this region is possibly the most favorable for cbm production

comparison of gis based landslide susceptibility models using frequency ratio logistic regression and artificial neural network in a tertiary region of ambon indonesia abstract this study aims to evaluate landslide causative factors in landslide susceptibility assessments and to compare landslide susceptibility models based on the bivariate frequency ratio fr multivariate logistic regression lr and artificial neural network ann the majority of landslide occurrences in ambon indonesia is induced by heavy rainfall events where slope failures occur mostly on steep slopes thereby endangering municipality areas at the base of the hills eight landslide causative factors were considered in the landslide susceptibility assessments the causative factors were elevation slope angle slope aspect proximity to stream network lithology density of geological boundaries proximity to faults and proximity to the road network the output susceptibility maps were reclassified into five classes ranging from very low to very high susceptibility using jenks natural breaks method twenty percent of all mapped landslides were used as the validation of the susceptibility models the validity and the accuracy of each model were tested by calculating areas under receiver operating characteristic curves rocs and the areas under the curve auc for the success rate curves of fr lr and ann were 0 688 0 687 and 0 734 respectively the auc for the prediction rate curve of fr lr and ann were 0 668 0 667 and 0 717 respectively all findings of the models show good results with the accuracy of all models being higher than 66 the ann method proved to be superior in explaining the relationship of landslide with each factor studied