composite model with fractional flow dimensions for well test analysis in fractured rocks abstract the represented analytical model is addressed to fracture zone aquifers in which well test responses can be commonly matched with models involving fractional flow dimensions the model assumes a composite structure representing the fractures opening into the pumping well and the fracture system comprising the actual aquifer the aim is to assess the hydraulic properties for the near well zone and the aquifer in terms of concrete parameters even if flow dimensions have fractional values dimensionless drawdown in pumping and observation wells was solved by applying laplace transforms the early time approximation for the pumping well can be used to assess the transmissivity t 1 if the flow dimension in the inner zone n 1 is greater than about 1 7 the long time solutions indicate that the inner zone induces a pseudo skin effect that can be estimated by comparing the pumping well and observation well data if k 1 is known the extent of the inner zone r can be estimated from the pseudo skin factor the responses tend to form log log straight lines with slopes of 1 n 2 by plotting drawdown vs t 1 n 2 on the double logarithmic scale the product of the hydraulic conductivity and the through flow area at the wellbore radius ka 2 and the hydraulic diffusivity d 2 of the aquifer can be estimated from the slope and the intercept the hydraulic conductivity of the aquifer k 2 is estimated by considering the through flow area as a projection of an n 2 dimensional sphere with a radius of r wb through three dimensional space by an amount r 3 n 2 the analyzed field example comprises a pumping test of a fracture zone aquifer in south central finland for the pumping well simultaneous matching of drawdown and derivative type curves with observed responses can be used to verify the results of the early time analysis and the proposed straight line procedure in addition type curve matching yields estimates of the hydraulic diffusivity ratio and a value of the dimensionless wellbore storage the analyzed observation wells are considered to be sufficiently far from the inner zone consequently type curves are produced based on the dimensionless drawdown solution that is identical to generalized radial flow model type curve matching of the observation well responses produces estimates for ka 2 k 2 and d 2 the obtained values are similar to previous studies that included models relying on integer flow dimensions however models relying on the fractional flow dimensions are capable to simulate the observed responses more accurately

dual permeability flow behavior for modeling horizontal well production in fractured vuggy carbonate reservoirs summary fractured vuggy carbonate reservoirs are composed of by matrix fracture and vug systems this paper is the first investigation into the dual permeability flow issue for horizontal well production in a fractured vuggy carbonate reservoir considering dispersed vugs in carbonate reservoirs and treating media directly connected with horizontal wellbore as the matrix and fracture systems a test analysis model of a horizontal well was created and triple porosity and dual permeability flow behavior were modeled standard log log type curves were drawn up by numerical simulation and flow behavior characteristics were thoroughly analyzed numerical simulations showed that type curves are dominated by external boundary conditions as well as the permeability ratio of the fracture system to the sum of fracture and matrix systems the parameter is only relevant to the dual permeability model and if is one then the dual permeability model is equivalent to the single permeability model there are seven main flow regimes with constant rate of horizontal well production and five flow regimes with constant wellbore pressure of horizontal well production different flow regimes have different flow behavior characteristics early radial flow and linear flow regimes are typical characteristics of horizontal well production duration of early radial flow regime is usually short because formation thickness is generally less than 100 m derivative curves are w shaped which is a reflection of inter porosity flows between matrix fracture and vug systems a distorted w shape which could be produced in certain situations such as one involving an erroneously low time of inter porosity flows would handicap the recognition of a linear flow regime a real case application was successfully implemented and some useful reservoir parameters e g permeability and inter porosity flow factor were obtained from well testing interpretation

natural and anthropogenic lead in sediments of the rotorua lakes new zealand global atmospheric sources of lead have increased more than 100 fold over the past century as a result of deforestation coal combustion ore smelting and leaded petroleum lead compounds generally accumulate in depositional areas across the globe where due to low solubility and relative freedom from microbial degradation the history of their inputs is preserved in lakes there is rapid deposition and often little bioturbation of lead resulting in an excellent depositional history of changes in both natural and anthropogenic sources the objective of this study was to use sediments from a regionally bounded set of lakes to provide an indication of the rates of environmental inputs of lead whilst taking into account differences of trophic state and lead exposure between lakes intact sediment gravity cores were collected from 13 rotorua lakes in north island of new zealand between march 2006 and january 2007 cores penetrated sediments to a depth of 16 30 cm and contained volcanic tephra from the 1886 ad tarawera eruption the upper depth of the tarawera tephra enabled prescription of a date for the associated depth in the core 120 years each core showed a sub surface peak in lead concentration above the tarawera tephra which was contemporaneous with the peak use of lead alkyl as a petroleum additive in new zealand an 8 m piston core was taken in the largest of the lakes lake rotorua in march 2007 the lake is antipodal to the pre industrial sources of atmospheric lead but still shows increasing lead concentrations from 2 up to 3 5 g g 1 between the whakatane eruption 5530 60 cal yr bp and the tarawera eruption peaks in lead concentration in lake rotorua are associated with volcanic tephras but are small compared with those arising from recent anthropogenic derived lead deposition our results show that diagenetic processes associated with iron manganese and sulfate oxidation reduction and sulfide precipitation act to smooth distributions of lead from anthropogenic sources in the lake sediments the extent of this smoothing can be related to changes in sulfate availability and reduction in sulfide driven by differences in trophic status amongst the lakes greatest lead mobilisation occurs in mesotrophic lakes during seasonal anoxia as iron and manganese are released to the porewater allowing upward migration of lead towards the sediment water interface this lead mobilisation can only occur if sulfides are not present the sub surface peak in lead concentrations in lake sediments ascribed to lead alkyl in petroleum persists despite the diagenetic processes acting to disperse lead within the sediments and into the overlying water

integrated method of rs and gpr for monitoring the changes in the soil moisture and groundwater environment due to underground coal mining mining affects the environment in different ways depending on the physical context in which the mining occurs in mining areas with an arid environment mining affects plants growth by changing the amount of available water this paper discusses the effects of mining on two important determinants of plant growth soil moisture and groundwater table gwt which were investigated using an integrated approach involving a field sampling investigation with remote sensing rs and ground penetrating radar gpr to calculate and map the distribution of soil moisture for a target area we initially analyzed four models for regression analysis between soil moisture and apparent thermal inertia and finally selected a linear model for modeling the soil moisture at a depth 10 cm the relative error of the modeled soil moisture was about 6 3 and correlation coefficient 0 7794 a comparison of mined and unmined areas based on the results of limited field sampling tests or rs monitoring of landsat 5 thermatic mapping tm data indicated that soil moisture did not undergo remarkable changes following mining this result indicates that mining does not have an effect on soil moisture in the shendong coal mining area the coverage of vegetation in 2005 was compared with that in 1995 by means of the normalized difference vegetation index ndvi deduced from tm data and the results showed that the coverage of vegetation in shendong coal mining area has improved greatly since 1995 because of policy input rmb 0 4 per ton coal production by shendong coal mining company the factor most affected by coal mining was gwt which dropped from a depth of 35 41 m before mining to a depth of 43 38 m after mining at the bulianta coal mine based on water well measurements ground penetrating radar at frequencies of 25 and 50 mhz revealed that the deepest gwt was at about 43 4 m there was a weak water linkage between the unsaturated zone and groundwater and the decline of water table primarily resulted from the well pumping for mining safety rather than the movement of cracking strata this result is in agreement with the measurements of the water wells the roots of nine typical plants in the study area were investigated populus was found to have the deepest root system with a depth of about 26 m based on an assessment of plant growth demands and the effect of mining on environmental factors we concluded that mining will have less of an effect on plant growth at those sites where the primary gwt depth before mining was deep enough to be unavailable to plants if the primary gwt was available for plant growth before mining especially to those plants with deeper roots mining will have a significant effect on the growth of plants and the mechanism of this effect will include the loss of water to roots and damage to the root system

cross borehole slug test analysis in a fractured limestone aquifer summary this work proposes new semi analytical solutions for the interpretation of cross borehole slug tests in fractured media our model is an extension of a previous work by barker barker j a 1988 a generalized radial flow model for hydraulic tests in fractured rock water resources research 24 10 1796 1804 butler jr j j zhan x 2004 hydraulic tests in highly permeable aquifers water resources research 40 w12402 doi 10 1029 2003 wr002998 it includes inertial effects at both test and observation wells and a fractional flow dimension in the aquifer the model has five fitting parameters flow dimension n hydraulic conductivity k specific storage coefficient ss and effective lengths of test well le and of observation well leo the results of a sensitivity analysis show that the most sensitive parameter is the flow dimension n the model sensitivity to other parameters may be ranked as follows k le leo ss the sensitivity to aquifer storage remains one or two orders of magnitude lower than that to other parameters the model has been coupled to an automatic inversion algorithm for facilitating the interpretation of real field data this inversion algorithm is based on a gauss newton optimization procedure conditioned by re scaled sensitivities it has been used to interpret successfully cross borehole slug test data from the hydrogeological experimental site hes of poitiers france consisting of fractured and karstic limestones hes data provide flow dimension values ranging between 1 6 and 2 5 and hydraulic conductivity values ranging between 4 4 10 5 and 7 7 10 4 m s 1 these values are consistent with previous interpretations of single well slug tests the results of the sensitivity analysis are confirmed by calculations of relative errors on parameter estimates which show that accuracy on n and k is below 20 and that on ss is about one order of magnitude the k values interpreted from cross borehole slug tests are one order of magnitude higher than those previously interpreted from interference pumping tests these findings suggest that cross borehole slug tests focus on preferential flowpath networks made by fractures and karstic channels i e the head perturbation induced by a slug test propagates only through those flowpaths with the lowest hydraulic resistance as a result cross borehole slug tests are expected to identify the hydrodynamic properties of karstic channels and fracture flowpaths and may be considered as complementary to pumping tests which more likely provide bulk properties of the whole fracture karstic channel matrix system

a new method of data inversion for the identification of fractal characteristics and homogenization scale from hydraulic pumping tests in fractured aquifers hydraulic interference pumping tests are widely used for identifying mid to large scale aquifer hydraulic parameters fractured reservoirs often behave as fractal media for which classical interpretations may fail because of the decrease in permeability and fracture porosity or equivalently transmissivity and storage capacity with the pumping time and the extent over which the pumping stress has propagated a solution to hydraulic interference tests in fractal media is developed in dimensional variables which allows for a very rapid and unique fitting to data hydraulic parameters their scale exponents and the fractal dimension of the medium can be determined for each pressure draw down curve without any prior information or other calculation the method is applied to a large series of tests completed on the calcareous fractured aquifer of the experimental site in poitiers france even though data of pressure draw downs are various and show a fractal behavior permeability seems to rapidly homogenize for distances of 100 200 m on the other hand the fracture porosity shows a much progressive decrease with distance and homogenization is reached for scales beyond 300 500 m it is also shown that the classical cooper jacob interpretation of pressure draw downs may yield artifacts in the identification of permeability and fracture porosity orders of magnitude are comparable to that from fractal interpretation but their evolution with respect to time or distance scaling laws may strongly differ

study of automated top coal caving in extra thick coal seams using the continuum discontinuum element method abstract in order to investigate top coal drawing regularity and automated top coal caving technology in extra thick coal seams an approach coupling the particle element and the block element is presented based on the continuum discontinuum element method cdem then the constitutive model of hydraulic support is introduced into the cdem to simulate the top coal drawing process meanwhile the bergmark roos model for coal drawing of single support is extended into the collaborative coal drawing of multiple supports to optimize the automated top coal caving technology finally cdem models of hydraulic support armored face conveyer and coal rock strata are established according to the field conditions of the tongxin coal mine then the top coal drawing mechanism is analyzed and an automated top coal caving technology is proposed the results show that under the interaction between hydraulic support and surrounding rocks the final drawing body of initial top coal drawing appears as an irregular deflected ellipsoid shape during different support moving cycles the coal rock structure affects the coal drawing amount and support resistance a statistical comparison of the coal rock drawing amount based on 100 drawing openings indicates that the standard deviation of the coal drawing amount in automated one round coal caving is 1 83 m2 less than that in traditional coal caving 8 23 m2 and the coal drawing amount from each drawing window is more uniform for multi round coal caving techniques the average recovery rate remains at 79 4 and the rock mixed rate is less than 1 based on a comparison of several coal caving techniques automated four round coal caving technology is the optimal technology in which the change rate of the standard deviation of the coal drawing amount as well as the top coal recovery rate are both largest

dual porosity fractal models for transient flow analysis in fissured rocks a dual porosity fractal model is derived that considers transient flow from block to fissure skin between the fissure and the block and storage capacity and skin effect on the pumping well type curves for different flow dimensions are provided they concern the pumping well and observation wells located either in the fissure system or in a matrix block the interpretation of a field case using this model shows good agreement between the theoretical drawdown and the observed data with consistent results from the pumping well and the observation well a flow dimension of 1 45 is obtained

insights on pumping well interpretation from flow dimension analysis the learnings of a multi context field database abstract the flow dimension parameter n derived from the generalized radial flow model is a valuable tool to investigate the actual flow regimes that really occur during a pumping test rather than suppose them to be radial as postulated by the theis derived models a numerical approach has shown that when the flow dimension is not radial using the derivative analysis rather than the conventional theis and cooper jacob methods helps to estimate much more accurately the hydraulic conductivity of the aquifer although n has been analysed in numerous studies including field based studies there is a striking lack of knowledge about its occurrence in nature and how it may be related to the hydrogeological setting this study provides an overview of the occurrence of n in natural aquifers located in various geological contexts including crystalline rock carbonate rock and granular aquifers a comprehensive database is compiled from governmental and industrial sources based on 69 constant rate pumping tests by means of a sequential analysis approach we systematically performed a flow dimension analysis in which straight segments on drawdown log derivative time series are interpreted as successive specific and independent flow regimes to reduce the uncertainties inherent in the identification of n sequences we used the proprietary siren code to execute a dual simultaneous fit on both the drawdown and the drawdown log derivative signals using the stated database we investigate the frequency with which the radial and non radial flow regimes occur in fractured rock and granular aquifers and also provide outcomes that indicate the lack of applicability of theis derived models in representing nature the results also emphasize the complexity of hydraulic signatures observed in nature by pointing out n sequential signals and non integer n values that are frequently observed in the database

investigation of non explosive expansion material in roof caving field application abstract effective roof caving plays a significant role in mining safety a spatiotemporal coupling fracturing method using a non explosive expansion material neem is proposed in this paper this method depends on the high fracturing capacity of the neem and a change from vertical charging to inclined charging aimed at producing new free surfaces step by step until the integrity of the entire rock is destroyed from a space time perspective the expansion stress and water adsorption of the neem were studied to determine the optimum stress increase interval and soak time with respect to the space aspect the charging sequence of boreholes was negatively correlated to their incline angles bringing the neem s superiority into full play based on the generation of new free surfaces in steps with respect to the time aspect the charging intervals of the inclined boreholes were designed to obtain the best stress compensation and highest fracturing efficiency a field trial was carried out in pingdingshan no 2 mine the results of which showed that some radial cracks were produced around the charging boreholes and that they propagated to the pilot boreholes moreover four main cracks were formed and were approximately parallel to the direction of the borehole rows in a fracturing group a fracture network was eventually generated which verified the expansion capacity of the neem and the feasibility of the spatiotemporal coupling fracturing method for field application

skin effect in generalized radial flow model in fractured media summary a generalized radial flow model treating the flow dimension as an arbitrary number and taking into account the well skin effect is presented to describe the transient head distribution in a fractured medium under the robin condition during constant head tests the laplace domain solution for the head distribution is first developed via the laplace transforms and the corresponding time domain solution in terms of the hydraulic head is then obtained using the bromwich integral method in addition based on the head solution and darcy s law the solution for the wellbore flux is further developed to investigate the skin effect it is found that the skin effect on the wellbore flux is significant at early times under this circumstance it would not be appropriate to neglect the skin effect in the model in determining the hydraulic parameters from the analysis of field data our solutions will be useful for the predictions of the spatial and temporal head distribution and wellbore flux or in investigating the skin effect on the head distribution and wellbore flux for flow with various dimensions in fractured media

interference pumping tests in a fractured limestone poitiers france inversion of data by means of dual medium approaches hydraulic interference pumping tests remain a valuable method for obtaining information on underground flows at a scale compatible with the operation of a reservoir combining a dual medium model with the inversion of interference testing data in fractured rocks is very recent probably because the model is ruled by very contrasted sensitivities to its main parameters it is shown that an accurate and stable inversion requires a specific procedure based on re scaled sensitivities to parameters both homogeneous and fractal dual media have been inverted on two sets of data obtained from the fractured limestone of the experimental site in poitiers france the first data set can be homogenized with both homogeneous and fractal approaches yielding almost constant hydraulic parameters or only weak statistical variations beyond experienced distances of 200 m the second data set collected in a site perturbed by forced flows from the first campaign shows preferential flow paths with a piston like propagation of the pressure depletion only the fractal dual medium is able to partly homogenize the hydrodynamic behavior surprisingly the hydraulic conductivity is constant but the dimensioning constants of the capacity parameters continue to decrease with the size of the system thus the intrinsic decrease of parameters with the size of the system in the fractal approach is not sufficient to mimic the scale effects recorded by interference tests superimposition of piston like effects onto dual media shall be further investigated to better account for the influence of scarce flow paths with very high velocities

investigation of movement and damage of integral overburden during shallow coal seam mining abstract most prediction methods used to calculate mining induced subsidence are empirical which cannot explain the mechanism of fundamental rock strata movement in this paper based on key stratum theory and the mechanical analysis of overburden a new analytical solution the analogous hyperbola subsidence model ahsm was proposed to describe the movement and damage of inner burden mining induced rock strata movement was verified using the distinct element method udec to assess the performance of the theoretical model three subsidence parameters smax t sgoaf smax d h generally used to describe surface subsidence trough agree with statistical field measurements of the south coalfield in australia the surface subsidence and the movement boundary in the overburden are very close to the theoretical predictions additionally the primary key stratum damages the least in the overlying strata its broken length is the smallest the width of subsidence trough and maximum surface subsidence increase as the primary key stratum drops

surface stepped subsidence related to top coal caving longwall mining of extremely thick coal seam under shallow cover the surface stepped subsidence had badly affected the public infrastructure safety the formation mechanism of the surface stepped subsidence case was explained the surface subsidence profile after the sequent mining activity was predicted the possible controls of the stepped subsidence were lastly proposed

ground movements over longwall workings in the kamptee coalfield india abstract subsidence investigations were conducted over three superimposed longwall panels in the kamptee coalfield of central india the extracted contiguous seams were lying below a water bearing unconfined aquifer filling of voids with sand hydraulically was practised to avoid a sudden inrush of water into the under ground workings through ground movement induced cracks the non effective width of extraction varied between 0 55 and 0 61 times the thickness of intact rockmass in the overburden the maximum subsidence slope compressive and tensile strains were 9 of extraction thickness 6 1 6 6 and 5 3 mm m 1 respectively the angle of draw was influenced by the presence of a fault and composition of superincumbent strata the ground movements lowered water table by 6 5 m in the unconfined aquifer due to the mining

double porosity models for a fissured groundwater reservoir with fracture skin theories of flow to a well in a double porosity groundwater reservoir are modified to incorporate effects of a thin layer of low permeability material or fracture skin that may be present at fracture block interfaces as a result of mineral deposition or alteration the commonly used theory for flow in double porosity formations that is based upon the assumption of pseudo steady state block to fissure flow is shown to be a special case of the theory presented in this paper the latter is based on the assumption of transient block to fissure flow with fracture skin under conditions where fracture skin has a hydraulic conductivity that is less than that of the matrix rock it may be assumed to impede the interchange of fluid between the fissures and blocks resistance to flow at fracture block interfaces tends to reduce spatial variation of hydraulic head gradients within the blocks this provides theoretical justification for neglecting the divergence of flow in the blocks as required by the pseudo steady state flow model coupled boundary value problems for flow to a well discharging at a constant rate were solved in the laplace domain both slab shaped and sphere shaped blocks were considered as were effects of well bore storage and well bore skin resultsmore obtained by numerical inversion were used to construct dimensionless type curves that were applied to well test data for a pumped well and for an observation well from the fractured volcanic rock terrane of the nevada test site less

influence of overburden mass behavioural properties on subsidence limit characteristics abstract an analytical calculation model for the angle of draw is introduced in this paper on the supposition that the roof is considered as an elastic beam this model indicates the importance of the main factors which control the extent of subsidence produced on the surface and also provides some appreciation of the influence of overburden strength on the angle of draw a finite element model has been developed for application to subsidence related rock mechanics problems by the use of this model the authors have investigated the effects rock mass behavioural properties on the limit angle and also the effects of a distinct bed strong or weak in the overburden on the subsidence affected area at the surface relevant u k data from monitored sites for determining the three limit angles variation with the dip of seam are discussed the trend of the limit angle from the north of england to the midland coalfields is also discussed in the paper it has been found that the results from the data are in good agreement with numerical model results

a new method of characterizing fissured media by pumping tests with observation wells abstract an analogy has been defined between the relation s r t at n and the elementary solution derived from the general flow equation describing fluid flow in fissured media assuming a non integer flow dimension that analogy can be used to characterize a fissured medium by parameters that are similar to those describing a porous reservoir if at least two observation wells are available and if flow involves a sufficient number of fractures the flow system behaves as a fractal object with observation wells located along axes in several directions anisotropy can be characterized two field applications illustrate the proposed method

subsidence versus natural landslides when dealing with property damage liabilities in underground coal mines abstract this paper presents a case study in the town of boo asturias spain where land subsidence due to underground coal mining has been observed in the past along with landslides and natural ground settling the confluence of these phenomena represents a liability for mining companies any property damage caused by ground movements is considered by those affected to be a direct result of mining induced subsidence this has led to numerous property damage liability claims against mining companies even many years after the mining activities have stopped based on the analysis of geotechnical studies subsidence simulations developed with hundef and 3dec software and ground movement measurements together with research developed within the research fund for the coal and steel merida project the authors investigated the landslide and slope instability phenomena that are occurring in the town of boo moreover they determined the geographical and temporal limits to distinguish damages for which mining activity may be responsible from natural or human induced damages unrelated to mining this research will allow underground coal mining companies to manage property damage liability claims from a clearer perspective and may help researchers reconsider some studies that focused only on mining induced subsidence to explain ground movements within similar environments