chemical weathering indices applied to weathering profiles developed on heterogeneous felsic metamorphic parent rocks abstract chemical weathering indices are commonly used for characterizing weathering profiles by incorporating bulk major element oxide chemistry into a single metric for each sample generally on homogeneous parent rocks weathering indices change systematically with depth however the weathering of heterogeneous metamorphic rocks confounds the relationship between weathering index and depth in this paper we evaluate previously defined chemical weathering indices for their suitability in characterizing weathering profiles developed on felsic heterogeneous metasedimentary bedrock from coweeta hydrologic laboratory north carolina usa among the weathering indices evaluated here the weathering index of parker wip is the most appropriate for application to weathering profiles on heterogeneous and homogeneous parent rock because the wip includes only the highly mobile alkali and alkaline earth elements in its formulation it yields values that differ greatly from those of the parent rock in addition the wip allows for aluminum mobility unlike other weathering indices these characteristics combine to make the weathering index of parker the most applicable index for studying the weathering of heterogeneous metasedimentary rocks however the wip should be applied judiciously as alkali and alkaline earth metals may be readily depleted during weathering in addition to reflecting weathering the chemical index of alteration cia chemical index of weathering ciw plagioclase index of alteration pia and vogt s residual index v may be sensitive to subtle geochemical changes such as hydrothermal alteration along a fault and or alteration at the water table weathering indices that include iron in their calculations were not included in this study because they do not distinguish between ferric and ferrous iron the oxidation state and distribution of iron in a weathering profile is influenced by the proportion of oxidation states in the pre weathered metamorphic rock and interaction with groundwater during weathering

numerical simulation of floodplain hydrology despite the extensive research into hillslope and channel interactions in headwater catchments surprisingly little attention has been paid to such processes in lowland rivers in particular previous studies have not addressed the influence of hillslope contributions and have concentrated solely on in bank floods rather than more complex out of bank cases accordingly we combine field monitoring and numerical modeling to study hillslope floodplain and channel interactions for a lowland river piezometric precipitation and river stage data were used to parameterize and test a new two dimensional finite element model of saturated unsaturated flow applied to two vertically aligned cross sections through a lowland floodplain data for two major out of bank flood events were simulated which appeared to show the presence of a significant unsaturated zone extending up to 5 m below the surface the model simulated reasonably well the pressure head field that was recorded at a number of piezometers located internal to the computational domain on each transect and we conclude that floodplain hydrology is predominately a two dimensional lateral process three dimensional down reach flow effects would seem to become more significant at the beginning and end of each event the simulations also showed that the unsaturated zone remained close to saturation at all times and that it was not significant in terms of the floodplain hydrology examination of velocity vector patterns showed the formation of a strong groundwater ridge within the floodplain this led to the development of strong velocities directed toward hillslope areas as the inundation front approached the hillslope floodplain junction this suggests that surface water may move into hillslope areas adjoining the floodplain during major floods thus the extent of the hyporheic zone may be larger than previously thought

the variation of heat generation density and seismic velocity with rock type in the continental lithosphere abstract the petrophysical properties radioactive heat generation compressional wave velocity and density are related to rock type in crystalline rocks the cation fraction in the rock forming minerals is applied to determine the relationships quantitatively heat generation exhibits considerable variation with rock type as well as with the geologic age of the rocks therefore the relation between heat generation and rock type has been split into a relation for phanerozoic rocks and another for precambrian rocks which exhibit significantly lower heat generation only 1 3 of that of phanerozoic rocks the interrelations between the petrophysical properties are applied to fennoscandia precambrian terrane and southern bavaria northern alpine foreland phanerozoic rocks to estimate the heat generation by radioactivity in the crust and the heat flow density from the upper mantle

weathering of the oporto granite geotechnical and physical properties abstract this paper characterizes the weathering products of the two mica oporto granite in terms of its mineralogical chemical geotechnical and physical properties this information is used to identify a physical property that can be used as an index of the degree of weathering and to estimate other properties in outcrop the oporto granite is always weathered and weathering profiles frequently exceed 20 m within these profiles granitic saprolites are composed of quartz feldspars and some mica with kaolinite and gibbsite as final weathering products the average percentage of secondary minerals determined by bulk x ray diffraction xrd is low in both weathered rock 2 4 and saprolite 8 7 geotechnically the saprolites exhibit no or low plasticity plasticity index pi 12 the skeleton character of the saprolites is reflected in the significant proportion of fines 29 5

engineering and geological characteristics of granite weathering profiles in south china granite weathering profiles are widely distributed in south china their engineering and geological characteristics are major geotechnical subjects that are important in the design and construction of civil engineering projects this paper presents a summary of the weathering characteristics and zoning of granite weathering profiles in south china and discusses their engineering and geological properties a five grade scheme has been adopted in the zoning of a granite weathering profile studies have shown that the completely weathered granites cwg in south china have the following characteristics low moisture content low to medium plasticity w l 22 5 39 0 i p 6 5 11 8 medium void ratio 0 36 1 29 weak shrinkage and medium compressibility a 1 2 0 24 0 8 mpa 1 and high shear strength phi 20 30degrees c 20 40 kpa the cwgs are usually at a low or high plastic state and most of them are over consolidated soils a majority of the physical and mechanical properties have good statistical correlations with the degree of weathering the data presented in the paper are important in geotechnical engineering projects such as slope stability evaluation in china c 2002 elsevier science ltd all rights reserved

water table fluctuations near an incised stream walnut creek iowa abstract incised channels are common features in many agricultural watersheds but the effects of channel incision on riparian water table conditions have been poorly documented in this study we evaluate the water table fluctuations in the floodplain near an incised stream walnut creek iowa and investigate the roles that channel incision and variable recharge play in modifying the water table configuration in the floodplain groundwater flows from higher landscape positions towards walnut creek under hydraulic gradients that were steepest near the upland floodplain contact and in the near stream riparian zone annually water table fluctuations on the floodplain were greatest in wells located 30 m from the creek midway between the creek and upland water levels monitored continuously during a runoff event indicated that bank storage was confined to a narrow zone adjacent to the channel a steady state one dimensional analytical model was developed to describe the shape of the water table surface near an incised stream and evaluate how variable groundwater recharge and channel bed lowering has affected the shape of the water table surface results from this study have implications for managing the riparian buffers of incised streams with successful establishment dependent upon matching buffer vegetation to riparian water table conditions

weathering profiles and clay mineralogical developments bornholm denmark abstract saprock saprolite associations were studied by field and laboratory methods optical microscopy x ray powder diffraction scanning electron microscopy electron microprobe in order to describe regolith development in the crystalline rocks of the nygard kaolin pit bornholm denmark the clay sequences and stages of porosity development are similar to those observed for reservoir rocks from the utsira high riber et al 2016 the weathering of the parent granite began before the end of the mesozoic two stages of syn pre burial alteration followed by diagenesis during burial and then post uplift weathering have been recognized in stage plagioclase and some biotite biotite vermiculite kaolinite reacted to form elongate booklets of highly ordered kaolinite or smaller blocky pseudohexagonal crystals stage ii represented more extreme weathering developed along local fracture systems the higher potential for fluid flow in the fractures caused highly ordered kaolinite to alter to halloysitic poorly ordered kaolinite plagioclase biotite and k feldspar continued to interact with formation water and formed additional quantities of secondary clay minerals as a consequence of inter intra and trans granular cracks the original rock fabric deteriorated and porosity increased during later burial diagenetic siderite crystals filled voids and chlorite formed at the expense of kaolinite after re exposure calcite precipitated in localized zones smectite formed on a broader scale wherever high ionic strength groundwaters were present a mineralogical key to predicting where high porosity and permeability zones occur is the recognition of halloysitic poorly ordered kaolinite highly ordered kaolinite is abundant but it is ubiquitous siderite chlorite and smectite adversely affect permeability riber l dypvik h sorlie r and ferrell r 2016 clay minerals in deeply buried paleoregolith profiles norwegian north sea clays clay miner doi 10 1346 ccmn 2016 064036

surface subsurface water interactions in an alluviated mountain stream channel data from an instream tracer experiment performed in north fork dry run shenandoah national park virginia illustrate that the transport of water and conservative solute in the stream is greatly influenced by interaction with water present in both the relatively shallow gravel bed and in the relatively deeper alluvial infill material the shape of concentration time curves from the field tracer experiment exhibit storage of tracer in the subsurface short term storage imposed by exchange with the gravel bed and long term storage by exchange with the deeper alluvial infill time series models fit the observed concentration data very well estimates of mixing volumes generated by the time series analysis indicate that a large volume of the gravel bed participates in rapid mixing with the surface stream at one point along the study reach a second order time series model is supported by the data suggesting two independent parallel flow paths observations of tracer in wells more than 10 m from the stream and the very extended recession of the tracer in the stream where it flows over a bedrock ledge support the contention that the deeper alluvium plays an important role in transient storage of solute in north fork dry run the work implies that physically based models to predict transport and storage in alluviated mountain catchments may have to account for interactions between the stream and large portions of its floodplain

dynamics of floodplain island groundwater flow in the okavango delta botswana abstract surface water groundwater interactions play a crucial role in the hydrology and ecology of the okavango delta the hydrology of the delta is dominated by the annual arrival of a flood wave which is distributed over an number of branches subsequently the flood water feeds the phreatic aquifers underlying the delta islands in order to evaluate the seasonal and long term dynamics of the surface water groundwater interactions between the floodplains and the islands a network of piezometers located in various locations of the delta was monitored groundwater table fluctuations observed for up to 6 years were analysed and modelled using groundwater flow models the floodplain island groundwater flow is in general very dynamic and driven by island evaporation and transpiration a typical small to medium sized island width 500 m and at the perimeter of the flooded area is the influence of long term antecedent conditions apparent the knowledge gained during this study will be used for the improvement of the hydrological and hydro ecological model of the delta and can be useful for the description of floodplain dynamics in semi arid regions in general

the capillary fringe and its effect on water table response abstract shallow water tables are often observed to respond in a highly disproportionate manner to precipitation events that is the magnitude of the response is often much greater than would be predicted on the basis of the specific yield of the geologic material and the amount of rainfall physical arguments are presented to show that if the capillary fringe the zone of tension saturation extends to ground surface then the addition of a very small amount of water can result in an immediate and large rise in the water table the arguments are supported by a field experiment in which the addition of 0 3 cm of water caused the water table to rise 30 cm in 0 25 min thus demonstrating the large and highly transient influence of the capillary fringe on the position of the water table the evidence in this study as well as recent work of others suggests that the capillary fringe effect could have a major influence on the process of stream flow generation contaminant transport to surface waters and contaminant transport in hydrogeologic regimes having shallow water tables it is further shown that calculations of groundwater recharge and consumptive use based on water table response and an assumed specific yield could be substantially in error

simple spatially distributed models for predicting flood inundation a review abstract in this paper we review recent progress in the use of reduced complexity models for predicting floodplain inundation we review the theoretical basis for modelling floodplain flow with simplified hydraulic treatments based on a dimensional analysis of the one dimensional shallow water equations we then review how such schemes can be applied in practice and consider issues of space discretization time discretization and model parameterisation before going on to consider model assessment procedures we show that a key advantage of reduced complexity codes is that they force modellers to think about the minimum process representation necessary to predict particular quantities and act as a check on any tendency to reductionism at the same time however the use compared to standard hydraulic codes of strong simplifying assumptions requires us to also address the question how simple can a model be and still be physically realistic we show that by making explicit this debate about acceptable levels of abstraction reduced complexity codes allow progress to be made in addressing a number of long standing debates in hydraulics

generic transformation models for some intact rock properties a global intact rock database of nine parameters including uniaxial compressive strength and young s modulus is compiled from 184 studies this database labeled as rock 9 4069 consists of 27

water table fluctuations within the floodplain of the river severn england abstract in contrast to extensive research on hydrological processes operating in headwater basins there has been relatively little attention paid to the hydrological processes that occur on the floodplains of lowland rivers this dearth of information is all the more surprising given current interest in the use of floodplains as buffer zones between farmland and the riverine environment in the previous paper water resour res 36 2000 2517 bates et al reported preliminary results from a field site on the floodplain of the river severn in shropshire uk a large lowland river by british standards piezometric data suggested that during out of bank conditions a reverse groundwater ridge develops in the floodplain subsurface and results in strong groundwater flux velocities directed towards the base of hillslopes adjoining the floodplain bates et al showed that the impact of such ridges was to switch off hillslope inputs to the riparian zone they hypothesised that this occurred when surface inundation approached the back of the floodplain in this paper we provide a more detailed analysis of the events considered by bates et al and extend the analysis to the more common in bank flood condition in total five events are considered two out of bank and three in bank these were chosen to represent a wide range of event magnitudes antecedent conditions and local patterns of rainfall and runoff the analysis demonstrates that the reverse groundwater ridging process identified by bates et al also occurs during in bank events hillslope inputs to the floodplain are also switched off in these events if the flood stage is high in smaller floods water continues to move from slope to floodplain although coupling between slope and channel is only re established later in the recession we conclude that contrary to the conclusions of bates et al this process switching is not necessarily dependent on surface inundation approaching the back of the floodplain whilst the paper broadly confirms the operation of the simple reverse groundwater ridging process described by bates et al it shows that antecedent conditions local rainfall and runoff and flood stage all act to complicate this basic pattern lastly we consider the implications for catchment water quality of the newly identified processes

flood delineation in a large and complex alluvial valley lower panuco basin mexico determining the extent of flooding is an important role of the hydrological research community and provides a vital service to planners and engineers for large river systems located within distant settings it is practical to utilize a remote sensing approach this study combines a remote sensing and geomorphic approach to delineate the extent of a large hurricane generated flood event in the lower panuco basin 98 227 km2 the seventh largest river system draining into the gulf of mexico the lower panuco basin is located within the coastal plain of eastern mexico and has a complex alluvial valley data sources included a landsat 5tm and landsat 7etm scene and topographic and particle size data from fieldwork and laboratory analysis the landsat 5tm image was acquired after the peak of a large flood event in 1993 whereas the landsat 7etm scene was acquired during the dry season in 2000 the increasing number of days between flood crest and the date of flood image acquisition along the river valley provided the opportunity to examine several methods of flood delineation and to consider differences in floodplain geomorphology backswamp environments were easily delineated in flooded reaches within the panuco and tamuin valleys whereas in the moctezuma valley more sophisticated methods were required because of the greater time between image acquisition and flood peak and the complex floodplain topography this included principal component pc analysis and image classification within the floodplain residual holocene terraces complicated flood mapping classification of both images allowed consideration of the influence of permanent standing water although the flooded areas were greater in the lower reaches of the study area because this portion of the valley contained large floodplain lakes the amount of inundation was actually lower remote sensing offers the ability to examine large alluvial valleys in distant settings but does not imply that geomorphic criteria should be excluded indeed because of heterogeneous floodplain topography this study illustrates the importance of including field based geomorphic analysis so that the complexity of distinct floodplain environments are considered the findings from this study are significant because most remote sensing data obtained for the purpose of flood mapping will not coincide with the flood crest thus this study provides an appropriate method for mapping flood inundation in large and complex floodplain settings after flood crest recession

mechanisms of natural fracturing in a sedimentary basin mechanisms of natural fracture generation in a sedimentary basin may be studied by the use of physical properties of sedimentary rocks and of pore fluid pressure the physical properties of rocks such as poisson s ratio and young s modulus under laboratory conditions are available but only a few of these are reported under subsurface conditions in this paper in situ values of poisson s ratio derived from analysis of artificial hydrofracturing data in the gulf coast are used for estimating horizontal stresses in both hydrostatically and abnormally pressured zones there in a tectonically relaxed basin such as the gulf coast the horizontal stress can be a function of vertical overburden stress fluid pressure and poisson s ratio the horizontal stress increases with depth in the hydrostatic pressure zone but is abnormally low in the abnormally pressured zone fracture pressure and its gradient given as a sum of least horizontal stress and fluid pressure is however not abnormally low in the abnormally pressured zone because the fluid pressure there is abnormally high this paper describes the in situ fracture pressure gradient estimated for the gulf coast area on the basis of models of vertical fluid charging through an aquifer and a fault system during continuous burial the depth at which the charged fluid pressure gradient exceeds the fracture gradient or the point of natural hydrofracturing is estimated after an erosional event the most significant decline of fracture pressure gradient is expected in the uppermost part of the original abnormal pressure zone hydrofracturing there could occur if an effective fluid is charging from deep to shallow through an aquifer or a fault system if the erosion continues to a point at which approximately two thirds of the total sediment thickness is removed the horizontal stress may become almost zero if such a stress condition is developed the sedimentary rocks become greatly relaxed possibly causing fractures

is there a genetic relationship between selected regional joints and contemporary stress within the lithosphere of north america on the appalachian plateau of new york ene striking joints parallel the mid continent contemporary stress field and do not correlate with other structures joints within ohio indiana michigan and west virginia also parallel the mid continent maximum horizontal compression as indicated by hydraulic fracture measurements in northern indiana where the contemporary stress field deviates significantly from the orientation of the mid continent stress the attitude of the joints deviates accordingly in addition to joints structures on several scales from subcontinent size fracture systems to microfabrics in shales apparently parallel the mid continent stress field from this i conclude that these joints are mode i cracks whose orientation corresponds to the contemporary tectonic stress field in itself the formation of these structures constitutes a tectonic event that has often been overlooked in favor of tectonic events that produce the more spectacular but less pervasive faults and folds

relationships between the petrophysical properties density seismic velocity heat generation and mineralogical constitution the petrophysical properties density p compressional wave velocity v p and heat generation a exhibit considerable variation with rock type to characterize a given rock quantitatively a single parameter the cation fraction expressed by the k value has been found to be suited best 100 crystalline rocks have been sampled to cover the widest possible range in k value from silicic types like granophyres and granites through granodiorites tonalites diorites gabbros amphibolites hornblendites pyroxenites to ultrabasic rocks p k a and v p were determined experimentally the latter at 0 5 kbar 50 mpa the interrelations between these properties were established by regression analysis the relation k and v p k show a linear dependence whereas a k a and a v p follow exponential laws in a w m 3 12 20 230 5 k mole cm 3 in a 22 5 8 15 g cm 3 and in a 16 5 2 74 v p km s all correlation coefficients are better than 0 9

flood risk assessment in the kosi megafan using multi criteria decision analysis a hydro geomorphic approach abstract floods are one of the most devastating natural events that lead to enormous and recurring loss of life properties and resources around the globe in india floods remain a major hazard during the monsoon season in many parts of the country but most seriously in the flat and monotonous gangetic plains in the himalayan foreland one of the most flood prone rivers in india is the kosi in north bihar eastern india which also forms the largest active megafan in the world the kosi river is known as the sorrow of bihar because of its anomalous behavior and the damage it causes due to frequent floods in this region this study evaluates the flood hazard and flood vulnerability as separate entities and combines them to assess the flood risk in the kosi megafan region geomorphological hydrological and socio economic data have been integrated in a gis framework using a multi criteria decision tool called the analytical hierarchy process ahp to generate a process based flood risk map for 105 blocks administrative units of both nepal and india bihar such maps should encourage soft engineering solutions for flood mitigation aimed at minimizing the consequences of flooding and reducing flood risks this study has significant implications for developing measures and plans that will help government and relief agencies in the identification of flood prone areas and for planning emergency management strategies in this region

weathering indices for rhyolitic tuff and granite in hong kong a series of chemical analyses and dry density tests of rhyolitic tuff and granitic samples have been carried out the test results have been interpreted using a newly developed theoretical weathering model for calculating a mobility index of major elements in rock and soil it is found that this index is useful for describing changes of rock and soil during weathering and classifying the degrees of weathering based on the theoretical model a new parameter called the volume index which combines chemical and physical data is suggested this index appears to be a good indicator for classifying the degree of weathering in hong kong a quantitative classification scheme is suggested

quantitative definition of highly weathered granite using the slake durability test the results are presented that were obtained from slake durability tests conducted on weathered korean granites it is demonstrated that the test can identify granite in the hw grade but can also provide both an accurate and a sensitive measure of weathering intensity within the hw grade of granite sophisticated sampling is not required also the slake durability test provides a quantitative measure of the soil to rock ratio within such materials

dynamic streambed fluxes during rainfall runoff events observed 3 d temperature distributions within a streambed were used to analyze the effects on exchange fluxes between groundwater and the stream during rainfall runoff events by combining a dense vertical and lateral monitoring network of streambed temperatures with coupled surface subsurface 3 d flow and heat transport modeling we demonstrate how temperature can be used directly as a calibration target three model setups with different hydraulic conductivity distributions were evaluated in an optimization approach using temperature and hydraulic head data the hydraulic conductivity distributions were based on slug test surveys within the streambed and aquifer a detailed characterization of the hydraulic conductivity of the streambed and aquifer is needed to accurately simulate observed temperatures hence the most sensitive parameters the vertical hydraulic conductivity and the thermal conductivity were calibrated within different conductivity zones of the heterogeneous model simulated exchange fluxes across the streambed showed variations up to a factor of four within just a meter such differences may not have been correctly predicted using 1 d heat transport models due to lateral conduction amongst the different flow paths during the rainfall runoff event fluxes decreased substantially 50 due to a decrease in the hydraulic gradient with increased stream stage although no flow reversals were observed during the studied conditions it is possible that these can occur during larger rainfall runoff events we show that with the current sampling and modeling techniques 3 d temperature data can be used to estimate dynamic exchange in heterogeneous flow fields encountered in the field

weathering or hydrothermal alteration summary altered granites are sometimes attributed to deep weathering and sometimes to hydrothermal alteration the nature of the evidence for the latter is discussed and found inadequate in many instances the alteration at bega australia and dartmoor england is considered to result from deep weathering

modelling floods in hydrologically complex lowland river reaches abstract this paper considers the modelling of lowland river reaches which contain complex within reach hydrological interactions it is clear that river and floodplain flow are the most important processes in terms of flood modelling in lowland systems although there are often important lateral inflows from catchments and hillslopes bounding the floodplain and from interactions between the river and the floodplain which can all affect the propagation of the flood wave previous models have often either considered a complex representation of the fluvial processes with no representation of the hydrological inflows into the reach bates p d anderson m g price d a hardy r j smith c n 1996 analysis and development of hydraulic models for floodplain flows in anderson m g walling d e bates p d eds floodplain processes wiley chichester pp 215 254 or have simulated a range of catchment processes with a poor representation of the river and floodplain abbot m b bathurst j c cunge j a o connell p e rasmussen j 1986 an introduction to the european hydrological system systeme hydrologique europeen she 2 structure of a physically based distributed modelling system journal of hydrology 87 61 77 hence this paper develops a modelling approach based on a two dimensional finite element hydraulic model of river and floodplain flow which is linked to a series of simple hydrological models that simulate catchment runoff surface and subsurface hillslope runoff and floodplain infiltration simulations show that the model is able to predict flood hydrographs for a series of flood events under a range of different hydrological conditions down a reach of the river severn uk furthermore the comparison of results from simulations using hydrological representations of different degrees of complexity suggest that there are restrictions on the necessary complexity of the hydrological components depending on the application of the model and the available validation data simple approaches to the reach scale hydrology may be sufficient if only the bulk outflow hydrograph is required by the user however more complex spatially and temporally distributed models appear to be required if predictions of the flood inundation extent are desired the simulations raise the issue of the application of distributed models and attempt to provide a framework for future research the results suggest that there is a need for the validation of the internal predictions of distributed models of flood flow and suggests a need for field data of river and floodplain interactions within long lowland river reaches

a new chemical index of weathering for metamorphic silicate rocks in tropical regions a study from sri lanka abstract weathered and fresh samples of metamorphic rocks from sri lanka were collected from various localities and analysed for major elements by xrf method rigaku kg x system japan the content of water was determined by the ignition method the xrf results obtained from these samples form the basis of a new index of chemical weathering particularly for sri lanka which is named the silica titania index and is calculated as follows silica titania index sio 2 tio 2 sio 2 tio 2 al 2 o 3 tio 2 sio 2 al 2 o 3 100 molecular proportions the index can be used to determine the degree of weathering in chemically weathered silicate rocks of other countries in tropical regions a triangular diagram plots the position of this index the point load strengths of fresh rocksand weathered rocks with different degrees of weathering were correlated with the values of this new chemical index the relative variation in strengths of fresh rocks and weathered rocks clearly indicates its suitability and usefulness for engineering geologists

investigation of physical deterioration of malayer granitic rocks using a new weathering coefficient kr4 the main aim of this research is to find the most appropriate weathering indices among geomechanical chemical and petrographical indices to characterize malayer granitic rocks in the study area physical weathering and hydrothermal alteration are predominant degradation phenomena therefore it is necessary to distinguish between the effect of these two phenomena and chemical weathering on mineralogy as well as on geomechanical rock properties the most important evidences of hydrothermal alteration are the selective sericitization of plagioclase and the occurrence of prehnite also statistical analyses including simple and multiple linear regressions were applied to identify those indices that are most influenced on the progression of weathering based on the simple regression analysis petrographical and chemical indices do not show any good trend by increasing weathering degrees r2 0 72 finally a new quantitative weathering index kr4 has been developed regarding quick absorption index p wave velocity vp point load index is and total porosity n all the mentioned parameters can be quickly and inexpensively determined by portable laboratory instruments this new index kr4 has strongly correlated with weathering degrees r2 0 96 based on some results it seems that kr4 could be more suitable and credible to numerically evaluate the physical weathering accompanied by hydrothermal alteration processes of the studied rocks

weathering of gneiss in calabria southern italy abstract the effects of weathering in a mediterranean climate on the mineralogy and microfabric of paleozoic gneiss of the sila massif calabria southern italy have been studied field observations show highly weathered rock forms a residual soil micromorphological and mineralogical properties of bedrock and saprolite show that the weathering process is characterized by at least two major stages having two distinct rock microfabrics in the first stage the morphological features of the original rock are preserved and weathering is manifested mainly by microfracturing and large portions of the rock remain unaltered the second stage of weathering involves further development of microcracks and progressive chemical attack on the minerals this latter stage occurs along both compositional and microstructural discontinuities with etch pitting of feldspar and neoformation of clay minerals and ferruginous products replacing feldspar biotite and iron bearing garnet the determination of quantitative petrographic indices provides a measure of the various stages of weathering

geotechnical comparison of weathering degree and shear wave velocity in the decomposed granite layer in hongseong south korea as part of a fundamental characterization of a subsurface layer in south korea the weathering degree and shear wave velocity v s were evaluated in a decomposed granite in hongseong using x ray fluorescence analyses and site investigations including borehole drilling with standard penetration test spt and in situ seismic tests the subsurface layer was composed of a weathered layer 10 40 m thick at most sites weathering degree analyses indicated that three chemical weathering indices the modified weathering potential index mwpi vogt ratio vr and weathering index of parker wip generally increased with decreasing depth in situ seismic tests revealed that v s ranged between 200 and 500 m s in the weathered layer using the v s and n values from the spt at borehole seismic testing sites correlations between v s and n values were established for the weathered layer furthermore examination of the relationships of the v s and n values with the mwpi wip and 100 vr indices showed that the index values increased linearly with increasing v s and exponentially with increasing n values

new approaches to the characterization of clay bearing densely jointed and weak rock masses various classification systems for rock masses have been used in engineering applications however these systems are not sufficient to classify clay bearing densely jointed and weak rock masses among the factors that cause this deficiency are the damaging effect of water on rocks which has not sufficiently been described in the existing classification systems this factor was allowed for by the inclusion of new parameters in the modified rock mass classification m rmr system developed in recent years the aim of this study is to make contributions to the m rmr classification system and to overcome the difficulties encountered in the classification procedure for this purpose data were collected for rock mass classification from 13 clay bearing densely jointed and weak rock masses in four regions yatagan soma baskoyak and guvenc located in the western and middle parts of turkey the discontinuity data were collected by the line survey technique and evaluated by statistical methods in addition to the uniaxial compressive strength test for the determination of the rating for intact rock strength the block punch index test was also considered as an alternative parameter and the slake durability index test and x ray diffraction analyses were performed on 104 samples collected from the studied rock masses further the weathering coefficient wc determined by schmidt hammer was considered as an alternative parameter for the determination of the rating for joint weathering as a result of statistical evaluation of data obtained from the field and laboratory studies it has been concluded that the block punch index bpi could be used as an alternative parameter for the determination of the rating for intact rock strength in the m rmr classification system it was also found that the slake durability index id determined at the fourth cycle would be a more effective approach than the second cycle index that has previously been used to express the unfavourable effect of water on the rock mass the propositions made in the present work to contribute to the m rmr system were tested in back analyses of three previously failed slopes and the performance of the system with the newly introduced improvements appeared to be satisfactory

mass change calculations in altered rock series a technique is presented whereby precursors of altered rocks in a fractionated rock series can be identified and changes in chemical components mass and volume accurately calculated the procedure utilizes elements with high degrees of immobility in hydrothermal and associated interactive water rock systems igneous rock series and sedimentary and metamorphic rocks with primary continuity of chemical composition are amenable to this treatment in the procedure for igneous rocks best fit fractionation lines are established for an immobile igneous compatible incompatible element pair the latter element functioning as the fractionation monitor alteration paths are linear and pass through the origin intersections of the fractionation and alteration lines yield the immobile element concentrations in the precursors to the altered rocks mobile components are determined from fractionation lines and monitor values total mass changes are proportional to the displacement of altered samples from the fractionation line masses of other elements in an altered sample reconstructed values are recalculated to the concentration of the monitor element in the precursor chemical changes are the differences between the calculated precursor compositions and the reconstructed altered rock compositions errors are mainly a function of the positioning of the fractionation lines

role of floodplain sediments in reducing the nitrate concentration of subsurface run off a case study in the cotswolds uk discharge of groundwater from a limestone aquifer through floodplain sediments is associated with a large decrease in the nitrate concentration of the water results are presented to show that only a small amount of this reduction is caused by dilution of groundwater by water already present within the floodplain sediments most of the effect is an active reduction process most probably biological denitrification the nitrate reduction process appears to operate independently of surface vegetation type and tends to be focused in specific regions of the floodplain where sediments are anaerobic and carbon rich the results suggest that active denitrification can operate throughout the winter when nitrate concentrations in groundwater are at their highest and that the process remains effective even during periods of maximum run off the results show that undrained floodplains can be used as buffer zones to protect surface waters from groundwater polluted with agriculturally derived nitrate

pore property as an indicator of macro deterioration in slightly weathered tuffs abstract tuff rock is highly heterogeneous due to volcanic activity hydrothermal alteration and weathering it is difficult to explain the deterioration mechanisms of the weathered rocks merely based on mineralogical and chemical parameters it has been reported that subtle weathering can modify pore structure and subsequently affect the rock mechanical behavior of tuffs in this work the pore characteristics in slightly weathered tuffs and fresh tuffs are systematically analyzed based on nuclear magnetic resonance nmr and mercury intrusion porosimetry mip tests additionally meso level uniaxial compression tests were conducted on the tuff samples by utilizing the mti lm miniature tensile instrument light microscope system to detect the crack propagation and deformation process the results demonstrated that additional mesopore 10 50 nm increases with pore throat expansion during weathering and the change of pore structure influences the tuff failure mode specifically for the slightly weathered tuff crack initiates in the altered minerals or matrix and results in shear failure however as for the fresh tuff crack usually initiates in the intact and fresh minerals and matrix and eventually leads to tensile failure therefore we propose that tuff pore property can serve as potential indicator of the micro mechanism of substantial macro deterioration due to weathering

the use of cation packing index for characterizing the weathering degree of granitic rocks the weathering state and weatherability of rocks are highly important for engineering geology projects and the use of rocks as building stones the weathering state of rocks can be described by various chemical and petrographical weathering indices to determine weathering state of a rock considerable amount of chemical analyses is required weatherability of rocks depends on not only their mineral composition but also the number of cation replaceable with hydrogen in a mineral in this study the use of the k value cation packing index is defined as the number of cation in a mole for characterizing the degree of weathering of granitic rocks is investigated for the purpose of the study the kurtun granitic rocks are selected as the material of the study the study contains three main stages and these are field investigations laboratory studies and regression analyses during the field studies in situ weathering descriptions and sampling are carried out the samples are subjected to chemical and petrographic analyses and physical and mechanical tests at the final stage of the study a series of regression analyses between the cation packing index and other properties of the samples are performed the results show that the k value can be used as a weathering indicator when compared with the other chemical weathering indices the k value can be used as a weathering index without chemical analyses because it can be determined by mineralogical analyses

new weathering classifications for granitic rocks based on geomechanical parameters here we investigate the classification of weathering grade for granitic rocks from the malayer granitoid western iran using physico mechanical parameters the physical and mechanical properties of rock samples were measured across five weathering grades ranging from fresh rock to completely weathered statistical analyses including simple regression and multiple linear regression were applied to identify those physico mechanical parameters that are most influenced by the progression of weathering the parameters with significant correlations with weathering grade include strength retention index p wave velocity porosity brazilian tensile strength and point load index on the basis of the statistical results new classifications are developed these classifications can be used to predict the engineering properties of the malayer granitic rocks hamedan nw iran and should have more general application to the quantitative classification of granitic rocks in iran

correlation between deformation lamellae microfractures macrofractures and in situ stress measurements white river uplift colorado dynamic analyses of quartz deformation lamellae and microfractures in lower paleozoic quartzites from the white river uplift record a northwest direction of compression which can be related to joint and fault orientations and in situ stress determinations crystallographic orientations of deformation lamellae resemble those formed in the subbasal i relatively nonselective domain microfractures in quartz grains form orthogonal sets of generally north northeast and west northwest trending fracutres which are approximately normal to bedding the strongest set of microfractures in most samples lies in the 2 plane deduced from deformation lamellae analyses suggesting that the microfractures are extensional features maxima of microfractures correspond to maxima of joints measured at adjacent locations the strikes of prominent west northwest sets of microfractures and joints are subparellel to the dominant northwest strike of faults on the uplift in situ stress measurements conducted in the piceance basin and rangely colorado areas indicate principal stress orientations similar to those determined from quartz deformation lamellae microfractures and joints which are pre uplift to early uplift late laramide fabric elements

density and seismic velocity in relation to mineralogical constitution based on an ionic model for minerals considering silicates and spinels as a close packing of spherical ions the oxygen ions because of their relatively large ionic radius use up more than 90 of the total ionic volume the close packing of oxygen forms a framework structure with partially constant physical properties the cations including silicon are small enough to fit into the interstices between the large sized oxygen ions without widening their framework structure the idealized space filling character of the cations explains the variations in physical properties of minerals on the basis of one variable only the cation packing index labeled k value k number of cations per mole avogadro s number s molar volume this variable is used to describe the density as well as the seismic velocity it is shownthat relationships between k value and both density and seismic velocity have approximately a linear character

a test of the relationship between seismic velocity and heat production for crustal rocks new heat production data of 40 rock samples comprising a wide variety of crustal rocks are compared with respective p wave velocities and densities in order to test the empirical velocity density heat production systematics proposed by rybach and buntebarth 1 2 which have been used by several investigators to determine heat production with depth in the crust our laboratory data do not convincingly fit any of the proposed relationships the lack of confirmation is attributed to the fact that the physical rock properties are mainly related to the single crystal properties of the respective major minerals whereas heat production in the rocks results from radiogenic components which are largely concentrated in accessory minerals

deep weathering along a granite ridgeline in a subtropical climate abstract bulk chemical composition and mineralogy were examined in three soil profiles and a deeper 11 meter profile weathering on a granite ridgeline under subtropical climate conditions in south china the weathering sequence is delineated by mineralogy and major element variations apatite biotite hornblende and plagioclase dissolve early during weathering resulting in nearly 100 ca and na loss and significant mg fe and p depletion at depth the k feldspar reaction front begins at the depth of depletion of plagioclase leading to a loss of 80 of the k at the land surface near the bottom of the ridgeline and almost 100 at the top dissolution of quartz and other silicates releases about 60 of si in the profiles kaolinite is the dominant clay mineral and it transforms to gibbsite in the uppermost layer the soil horizon upper 100 cm is the zone dominated by pedogenic processes including active biological activity physical erosion and influx of high concentrations of atmospheric components especially co2 and o2 the pedogenic processes are characterized by low ph 4 54 to 5 85 high clay content kaolinite 6 16 wt gibbsite 2 8 wt and total organic carbon content 0 13 3 93 and intensive fracturing and dissolution of quartz and k feldspar compared with the lower horizons accumulation of organic material and resistant minerals downslope is attributed to down ridge movement of water termed here interflow and weathering products in the uppermost 100 cm down the ridgeline using a mass balance model calculation for the catena that assumes steady state soil thickness at all sites the bottom profile shows the highest apparent total chemical weathering loss rate 14 g m 2 y 1 whereas the middle position shows the highest physical erosion loss rate 44 g m 2 y 1 sio2 accounts for about 84 of the chemical weathering outflux from the soil horizons along the ridgeline hillslope chemical weathering rates at the bottom of the hillslope may be accelerated by high concentrations of organic material and by dissolution of kaolinite this study demonstrates that mineral reaction fronts in granite become separated over depth intervals of meters and that elemental fluxes and release mechanisms vary with position along a ridgeline catena

orthorhombically arranged vein arrays abstract it is commonly accepted that arrays of en echelon veins occur either singularly or in conjugate pairs bulk finite plane strain is accompanied by these singular or conjugately arranged arrays when their formation and subsequent displacement occur in the same kinematic framework a new geometric and kinematic model for vein arrays is proposed which takes into account the effects of bulk non plane strain deformations on the evolving arrays in this model four sets of arrays develop during coaxial non plane strain deformations and two non conjugate sets of arrays develop during non coaxial non plane strain deformations the formation of singular and conjugate arrays is restricted to bulk plane strain deformations this model is the natural extension to the brittle ductile realm of models proposed for the geometry and kinematics of brittle faults formed during non plane strain deformations en echelon vein arrays mapped in central australia which cannot be understood as simple conjugate structures are interpreted as having formed during a bulk non coaxial non plane strain deformation

controls of groundwater floodwave propagation in a gravelly floodplain summary interactions between surface water and groundwater can occur over a wide range of spatial and temporal scales within a high hydraulic conductivity gravelly floodplain in this research dynamics of river groundwater interactions in the floodplain of the matane river eastern canada are described on a flood event basis eleven piezometers equipped with pressure sensors were installed to monitor river stage and groundwater levels at a 15 min interval during the summer and fall of 2011 results suggest that the alluvial aquifer of the matane valley is hydraulically connected and primarily controlled by river stage fluctuations flood duration and magnitude the largest flood event recorded affected local groundwater flow orientation by generating an inversion of the hydraulic gradient for 16 h piezometric data show the propagation of a well defined groundwater floodwave for every flood recorded as well as for discharges below bankfull 0 5 qbf a wave propagated through the entire floodplain 250 m for each measured flood while its amplitude and velocity were highly dependent on hydroclimatic conditions the groundwater floodwave which is interpreted as a dynamic wave propagated through the floodplain at 2 3 orders of magnitude faster than groundwater flux velocities it was found that groundwater exfiltration can occur in areas distant from the channel even at stream discharges that are well below bankfull this study supports the idea that a river flood has a much larger effect in time and space than what is occurring within the channel

thermodynamic interpretation of weathering indices and its application to engineering properties of rocks abstract weathering indices typified by the miura index w o m that are the ratios of geochemically mobile to relatively immobile elements can be shown to be logarithmically related to the free energy of the weathering reaction this can be demonstrated for silicate minerals other extensive properties such as the moduli of elasticity and rigidity are similarly correlated the mass strength envelope implied by the corresponding o log w plot concurs well with plotted values for rocks suggesting that the correlation is valid for intact rocks as well by a combination of the miura index and an index believed to show not only the state of weathering but also the susceptibility to further weathering the parker index w o p it is possible to obtain estimates of the activation energy for the incongruent aqueous dissolution of minerals which compare favourably with experimental determinations although the engineering behaviour of rocks is generally governed by physical parameters and thus by short term mechanical or physico chemical forces there are some instances where failure has been attributed to the chemistry of the rock itself for these rocks a good correlation is obtained between a chemical weatherability index log w o m w o p and rock durability as measured by the los angeles abrasion test

testing the groundwater ridging hypothesis of streamflow generation during snowmelt in a forested catchment hydrometric and isotopic techniques were used to test the groundwater ridging hypothesis of stream flow generation during snowmelt in a forested catchment on the canadian shield the catchment contains a central wetland that drains to an ephemeral channel hydrograph separation using 2h as a tracer indicated that approximately 60 of total stream flow during snowmelt was supplied by pre event water this was supported by hydrometric results however contrary to the groundwater ridging hypothesis the response of water table levels in near stream areas to initial melt inputs failed to promote a rapid flux of ground water to the wetland and stream all stream flow originated as saturation overland flow from the wetland and groundwater flow during much of the melt was directed down the catchment s main axis and back under hillslopes surrounding the wetland and channel although the hydrograph separation indicated pronounced short term variations in pre event discharge from the catchment groundwater fluxes to the wetland remained relatively invariant following initiation of surface saturation streamflow fluctuations appear to have been generated by displacement of water held in surface storage induced by melt and rainwater inputs to the wetland this stored water had an isotopic signature intermediate between that of event and pre event water suggested oscillations in pre event runoff were an artifact of the mixing model approach to hydrograph separation rather than the result of rapid changes in groundwater fluxes to the wetland

joint orientation in devonian rocks in the northern portion of the lower peninsula of michigan the orientations of 4 787 joints were measured at 43 separate locations in the area from charlevoix michigan to alpena michigan and north to the tip of the lower peninsula of michigan the sample localities are all in devonian carbonate rocks and shales of the michigan basin nearly all of the joints are vertical at least one major joint set is identifiable at each location and four major sets are present at more than half of the locations at 40 of the 43 sample localities there is a joint set with a strike of about 54 degrees n54 e at 35 locations there is a set striking about 133 degrees n47 w at 32 locations there is a set with a strike of about 92 degrees n88 w and a set with a strike of about 2 degrees no2 e is present at 31 sample localities mean orientation of any of the four joint sets does vary from location to location but is relatively consistent over the entire area for each of the sets fluctuations in mean orientation of any of the joint sets or the presence or absence of the joint sets is independent of formation lithology and distance between sample stations joint set orientation is independent of the regional strike around the michigan basin which varies from 54 degrees n54 e to 114 degrees n66 w within the study area the joint pattern does not appear to be related to structural trends previously postulated to exist in the precambrian basement of the area two of the joint sets may be related to major low amplitude folds in the paleozoic strata of the michigan basin in situ stress measurements show the orientation of maximum horizontal compressive stress to be compatible with these joint sets and the folds

characteristics of weathering zones of granitic rocks in malaysia for geotechnical engineering design tropical climatic conditions cause severe weathering to rock masses resulting in thick weathering profiles consisting of different weathering zones with complex characteristics feasible geotechnical engineering design requires a detailed understanding of the characteristics of each weathering zone a typical weathering profile is usually characterized by field scale observation and geological study this paper presents the characteristics of weathering zones of various granitic rocks in the south of malaysia this region has a tropical climatic condition the study was carried out in four active quarries located in johor province malaysia and forty sections were investigated in the study areas a typical granitic weathering profile was characterized based on the geological and structural parameters i e joint characteristics corestone occurrence rock soil ratio mass homogeneity color of rock and discoloration at joints surfaces the profile includes common zones ranging from fresh to residual soil however two subzones are introduced based on corestone boulder occurrence in the highly weathered and completely weathered zones this study based on detailed field observations at the mentioned quarries followed by analysis presents an amalgamated picture of weathering zones in granitic profiles of a tropical region like malaysia moreover it is believed that the characterization of the typical weathering profile allows further classification of generally complex weathered rock masses for a specific geotechnical engineering design