the effect of cutoff walls on saltwater intrusion and groundwater extraction in coastal aquifers summary we use numerical simulations to study the effect of cutoff walls on saltwater intrusion and assess their protective effect on groundwater extractions near the coast results are presented in terms of dimensionless variables with ranges suitable for field applications we find that in the absence of groundwater extractions the effectiveness of cutoff walls is determined by the wall depth its distance from the coast the velocity ratio the intensity of mixing the conductivity anisotropy and the relative conductivity of the wall to assess the effectiveness of cutoff walls in practical applications we present graphs and empirical equations also we assess the protective effect of cutoff walls on groundwater extractions by means of drains and single wells we do so by calculating the maximum safe extraction rate before and after the construction of a cutoff wall i e the maximum rate of groundwater extraction for which the maximum salt concentration entering the drain or the well is below a certain threshold we find that the protective effect of cutoff walls is stronger for single wells rather than drains and for cases when the extractions are located at relative small distances from the coast relative large depths and in aquifers with small velocity ratio weak mixing and high anisotropy to facilitate the design of safe extractions we use numerical results to develop analytical approximations for the influence of cutoff walls

field experiments and numerical simulations of confined aquifer response to multi cycle recharge recovery process through a well summary shanghai is one of the cities suffering from land subsidence in china land subsidence has caused serious financial losses thus artificial recharge measures have been adopted to compensate the drawdown in shallow confined aquifers and thereby control land subsidence in this study a multi cycle recharge recovery field experiment was performed to investigate the response of a shallow confined aquifer to artificial recharge through a well in the experiment a series of recharge recovery cycles with different recharge volumes and durations with and without artificial pressure were performed the water levels monitored in the recharge and observation wells indicated the response of the aquifer to the multi cycle recharge recovery process meanwhile a finite difference method fdm numerical model was established and its parameters were obtained via a reversed numerical analysis on the experimental data the responses of the shallow confined aquifer to the multi cycle recharge recovery process were simulated in detail using the model the calculation results showed that the water level dropped significantly when the recharge ended moreover the efficiency of a multi cycle recharge was found to be higher than that of a concentrated one under the same recharge volume and time the relationship between recharge frequency and efficiency expressed as h 0 29498 f 0 40163 and r 2 0 97264 respectively was obtained through the fdm numerical simulation in the recharge intervals the optimal recharge efficiency was achieved when the water level rose to 40 of the peak

the nature of orthomagmatic hydrothermal fluids in the oka carbonatite quebec canada evidence from fluid inclusions fluid inclusions in apatite monticellite and calcite from the oka carbonatite complex generally comprise either aqueous liquid vapour or aqueous liquid vapour halite some inclusions also contain a variety of trapped solids including calcite strontianite nahcolite and mirabilite microthermometry and raman spectroscopy indicate that co2 is not an important constituent of these fluids microthermometric data also indicate that the hydrothermal fluids liberated from the carbonatitic magma had a wide range of salinities 4 2 to 49 eq wt nacl and densities 0 77 to 1 26 g cm3 most of the fluids had relatively low concentrations of so42 and co32 6 wt however the nature of the trapped minerals and the phase behaviour of some inclusions indicate that some fluids may have had higher concentrations of so42 co32 and or hco3 textural relationships indicate that the crystallization sequence for the host minerals was monticellite apatite calcite which when combined with fluid inclusion data from the three minerals indicates that fluid salinity decreased and fluid density increased during progressive crystallization of the magma the density increase is thought to have been mainly caused by decreasing temperature isochoric projections indicate that the fluids were exsolved at minimum pressures of 4 to 8 kb these data provide a basis with which to assess the involvement of orthomagmatic aqueous fluids in the formation of hydrothermal rare element mineralization associated with carbonatites

a case history of field pumping tests in a deep gravel formation in the taipei basin taiwan 33 large diameter wells embedded in 2 m thick 63 m deep diaphragm walls were constructed to reduce both the uplift pressures and the groundwater inflow during the excavations as the actual thickness of the pumped aquifer is unknown the installed wells are regarded as partial penetration wells single well and multi well pumping tests were conducted in the deep gravel formation of taipei basin to derive the hydraulic parameters and to investigate the drawdown characteristics at both the construction and remote sites however the tidal effect on the drawdown of both the pumping well and nearby observation wells was found significant additionally wellbore storage skin and leakage need to be taken into account for deriving the hydraulic parameters hence a method to remove these five factors influencing the drawdown curve is developed which takes advantage from the late time characteristics of drawdown data and the early time behavior of drawdown some currently available semi log graphic techniques are therefore proven applicable for parameter determination validity of the proposed method is verified by the good agreement between the calculated and the measured drawdown of both the pumping well and observation well

fluid rock interaction during progressive migration of carbonatitic fluids derived from small scale trace element and sr pb isotope distribution in hydrothermal fluorite associated with the cretaceous okorusu carbonatite complex namibia is a hydrothermal fluorite mineralization hosted in pan african country rock marbles which resulted from fluid rock reaction between the marbles and orthomagmatic carbonatitic fluids expelled from the carbonatite yellow fluorite i was deposited in veins up to 5 cm away from the wallrock contact followed by purple and colorless fluorite ii smoky quartz and barite a mn rich crust on early calcite and pure calcite this clear cut sequence of mineral growth allows an investigation into fluid rock interaction processes between the marble and the migrating carbonatitic fluid and element fractionation patterns between the fluid and subsequent hydrothermal precipitates fluorite i shows a progressive change in color from dark yellow to colorless with purple laminations over time of deposition subsequent fluorite i precipitates show an increase in ca and a continuous decrease in f sr ree y th u and pb contents the ratios eu eu cn th pb and u pb increase whereas y ho th u and la yb cn decrease the sr isotopic composition remains constant at 87sr 86sr 0 70456 0 70459 but with varying highly radiogenic pb 206pb 204pb 32 190 238u 204pb 7 63 fluorite ii has 87sr 86sr 0 70454 0 70459 206pb 204pb 18 349 and 207pb 204pb 15 600 and a chemical composition similar to youngest fluorite i the mn rich crust on early calcite accumulated ree ba pb zr cs th and u developing into pure calcite with a prominent negative ce anomaly and successively more radiogenic sr the calculated degrees of fluid rock interaction f weight fraction of fluid fluid marble decrease from fluorite i and most fluorite ii f 0 5 to calcite f 0 2 0 3 and hydrothermal quartz f 0 1 a crush leach experiment for fluid inclusions in the hydrothermal quartz yielded a rb sr isochron age of 103 12 ma crush leach analysis for the carbonatitic fluid trapped in the wallrock yielded a trend from the fluid leachate to the host quartz 206pb 204pb 18 224 and 18 602 207pb 204pb 15 616 and 15 636 respectively extending from carbonatite towards crustal rocks calculated trace element distribution coefficients fluorite fluid are below unity throughout and increase from la to yb elements largely excluded from fluorite ba pb lree relative to hree were incorporated later into the mn rich crust on calcite the trace element patterns of the hydrothermal minerals are related to changing aco2 and af in the fluid during continued fluid marble reaction a predominance of carbonate over fluoride complexing in the fluid as reactions proceeded controlled the y ho th u and ree patterns in the fluid and the crystallizing phases deviations from these trends indicate discontinuous processes of fluid rock reaction

areal subsidence under pumping well curtain interaction in subway foundation pit dewatering conceptual model and numerical simulations subway foundation pit dewatering may contribute to the regional land subsidence in a built up area when aquifers are too thick to be cut off by a curtain the land subsidence induced by subway foundation pit dewatering was divided into local subsidence and areal subsidence the former was managed by construction organizations while the latter was managed by a land resource urban management and hazard prevention department the areal subsidence could not be recovered after dewatering because of its vast influence area and contribution to regional land subsidence the boundary between local subsidence and areal subsidence was defined as the location of three times the foundation pit depth to the foundation pit boundary the subsidence within the boundary belonged to local subsidence whereas the subsidence outside the boundary belonged to areal subsidence with shanghai as background the conceptual and mathematical models that considered hydrogeological conditions curtain depth and pumping well screens were established and numerical simulations were performed when the pumping well screens were enveloped by a diaphragm wall the best vertical distance of about 1 0 4 0 m was obtained between the screen bottoms and curtain bottom the decreasing rate of areal subsidence was the highest under the interaction of diaphragm wall and pumping well screens further increasing the penetration depth of the diaphragm wall and shortening the length of the pumping well screen were both less efficient

a fluid inclusion study of vug minerals in dawsonite altered phonolite sills montreal quebec implications for hfse mobility ordovician limestones in the francon quarr on the island of montreal quebec are host to three sills of cretaceous age composed of phonolite that has been extensively altered to dawsonite an interesting feature of the sills is the presence of abundant vugs containing a wide variety of minerals including several in which one or more high field strength elements zr hf nb ti is a major component the most important of these latter minerals is weloganite a rare strontium zirconium hydrous carbonate first identified in the francon quarry four types of inclusions have been recognized in vug minerals aqueous aqueous carbonic carbonic and solidbearing aqueous inclusions homogenize at temperatures mainly between 70 and 170 c and between 230 and 390 c the homogenization temperatures of primary inclusions cluster around 350 c aqueous inclusions and the aqueous phase in aqueous carbonic inclusions have salinities ranging between 10 and 24 eq wt nacl equivalent primary aqueous carbonic inclusions have low xco2 0 7 carbonic inclusions are all secondary nahcolite dawsonite and weloganite occur as daughter minerals or trapped solids nahcolite and possibly natron or mirabilite appear to form in frozen inclusions analyses of fluid inclusion decrepitates detected high concentrations of na cl al s and c the extraordinarily high concentration of al in the fluid possibly exceeding 1 wt suggests a ph of approximately 10 pressure and temperature conditions estimated from stratigraphic reconstruction and the isochores of primary aqueous fluid inclusions were 450 bar and 360 to 400 c respectively the relatively high temperatures and compositions of primary fluid inclusions suggest that vug filling was the result of mineral precipitation from an orthomagmatic fluid a model is proposed in which a partially crystallized phonolite melt started exsolving a homogeneous low xco2 fluid immediately prior to or after intrusion sodium aluminium chlorine fluorine sulphur and hfse elements such as zr hf nb and ti were partitioned into the hydrous phase in the case of zr possibly to a concentration of 300 ppm the near horizontal orientation of the sills and the chilled margins produced by quenching of the magma created a tight seal that inhibited escape of the fluids as a result the phonolite stewed in its own juices long after crystallization giving rise to widespread replacement of primary igneous minerals by dawsonite and precipitation of this and other minerals in vugs once the sills had colled to temperatures between 200 and 300 c the aqueous fluid exsolved a high co2 fluid which was trapped as the secondary three phase type ii and type iii inclusions decreasing temperature is considered to have been the principal control of mineralization although in the case of the lower temperature minerals decreased bicarbonate or carbonate ion activity and a lower dielectric constant as a result of co2 exsolution may have played a role in the deposition of hfse bearing minerals

elemental composition of concentrated brines in subduction zones and the deep continental crust abstract it has been well established that fluids played an important part in determining chemical characteristics in many crustal terranes studies of fluid inclusions in eclogites have established that brines coexisted with the primary mineral assemblages during their metamorphic crystallization these brines are currently multiply saturated in halide salts carbonates oxides and sulfides as a first step in quantitatively bounding the composition of the brines during metamorphism the equilibrium compositions of the brines at room temperature were computed using the aqueous speciation codes eq3 6 the results demonstrate that the brines are high density solutions ca 1 4 g cm 3 that have ionic strengths of approximately 8 mol and are approximately 40 dissolved solids by weight these are predominately na and k rich brines with subordinate ca and mg the approximate na k ca mg molar ratios are 4 2 0 5 0 2 but are sensitive to the assumed hco 3 concentrations charge balance is primarily maintained by the very high cl concentrations these brines bear resemblance to brines analyzed from fluid inclusions in metamorphic rocks reported by roedder roedder e 1972 composition of fluid inclusions us geol surv prof paper 440jj p 164 although these fluids have the potential of acting as significant metasomatic agents in subduction zones and deep crustal environments their impact will be mineralogically discernible only if the fluid release and movement is channelized

statistical and hydro mechanical coupling analyses on groundwater drawdown and soil deformation caused by dewatering in a multi aquifer aquitard system abstract groundwater withdrawn in a multi aquifer aquitard system maas may cause vertical cross flow supplement and result in groundwater drawdown and soil deformation in both aquifers and aquitards this study investigates the responses of groundwater and deep soils to dewatering in the maas through statistical and numerical analyses field data of ten pumping tests conducted in the maas in shanghai urban area are collected and a statistical analysis for groundwater drawdown and ground settlement is performed field measurements indicate that the drawdowns are distributed linearly along radial distance in logarithmic coordinates however the ground settlements are disproportional to the drawdowns and show a trilinear distribution along the radial direction to examine the inconsistent distributions of the groundwater drawdown and the ground settlement representative dewatering models are developed numerically and solved explicitly by the coupled biot s three dimensional consolidation theory numerical results of dewatering in maas are compared to those obtained by a non coupling formula moreover effect of a micro confined aquifer on drawdown and soil deformation is discussed it is found that soil compression in each stratum is closely related to the decline of the pore pressure whilst small expansions are observed in early dewatering stages due to the hydro mechanical coupling effect the ground surface settlement near the pumping well obtained by the coupled numerical method is significantly smaller than that by the non coupling formula owing to horizontal and vertical cross flow supplement an additional aquifer embedded in aquitard above the pumping aquifer can relief both the groundwater drawdown and ground surface settlement significantly

responses of retaining wall and surrounding ground to pre excavation dewatering in an alternated multi aquifer aquitard system abstract pre excavation dewatering ped is an important construction stage in deep excavation field measurements show that retaining walls can develop obvious deflections during ped which has been rarely considered in the past the characteristics of ped induced wall deflection and the relationship of this deflection to surrounding ground deformation are still unclear in this study a ped test is simulated by a numerical model the model is verified by field observations and used to investigate the responses of retaining wall and surrounding ground to ped results indicate that the maximum wall defection hm and surface settlement vm can all reach centimeter level under common conditions of ped the ratio of vm to hm varies at the range of 0 45 0 67 wall and soil deformations will be more obvious if the soils within the dewatering depth hd have better permeability the relative positions between hd and strata i e aquifer or aquitard have great influence on the ped induced deformations if an aquifer appears below hd further increasing hd can induce a rapid growth of wall and soil deformations if thick aquitard appears below hd the deformation increments by further increasing hd are not apparent however once hd exceeds the center of the thick aquitard and reaches a thick confined aquifer the wall deflections and soil deformation zones behind the wall will enlarge significantly meanwhile a large bending moment in the retaining wall will arise around the bottom of the confined aquifer the designers should consider this condition and allocate enough steel rebars there preventing the appearance of wall cracks in the confined aquifer

analyses of leakage effect of waterproof curtain during excavation dewatering abstract the waterproof curtain that is used to block groundwater leaks occasionally during deep excavation and can have a harmful impact on the surroundings this study adopts a three dimensional 3d fluid solid coupled finite element model fem to analyze the impact due to a leakage in the waterproof curtain during excavation dewatering in the model both a user defined one dimensional leakage element and a solid leakage element are incorporated to simulate the leakage the leakage of the curtain in the soil is analysed by monitoring the variation in hydraulic conductivity the simulated results demonstrate that the leaking rate leaking volume groundwater drawdown and ground settlement are closely related to the hydraulic conductivity of the leakage point the results also show that the groundwater head outside the pit declines quickly when the leakage occurs but soil consolidation proceeds slowly in addition the characteristics of the soil that is adjacent to the leakage point also have a tangible effect on the groundwater head and ground settlement the hydraulic conductivity and deformation modulus of the soil has a significant effect on the ground settlement while the influence of the anisotropy of the soil is relatively low

field experiment and numerical simulation of coupling non darcy flow caused by curtain and pumping well in foundation pit dewatering abstract high velocity non darcy flow produced larger drawdown than darcy flow under the same pumping rate when the non darcy flow caused by curtain met non darcy flow caused by pumping wells superposition and amplification effect occurred in the coupling area the non darcy flow was defined as coupling non darcy flow the coupling non darcy flow can be produced and controlled using different combination of curtain and pumping wells in foundation pit dewatering to obtain the maximum drawdown using the minimum pumping rate the qianjiang century city station foundation pit of hangzhou subway china was selected as background field experiments were performed to observe the coupling non darcy flow in round gravel a generalized conceptual model was established to study the coupling effect under different combination of curtain and pumping wells numerical simulations of the coupling non darcy flow in foundation pit dewatering were carried out based on the forchheimer equation the non darcy flow area and flow velocity were influenced by the coupling effect short filter tube large pumping rate small horizontal distance between filter tube and diaphragm wall and small vertical distance between the filter tube and confined aquifer roof effectively strengthened the coupling effect and obtained a large drawdown the pumping wells installed close to a curtain was an intentional choice designed to create coupling non darcy flow and obtain the maximize drawdown it can be used in the dewatering of a long and narrow foundation pit such as a subway foundation pit

sizewell b foundation dewatering system design construction and performance monitoring the design construction and extended performance of a major dewatering system allowed the construction of sizewell b to take place in the dry over an area of 9 ha within a 56 m deep diaphragm wall enclosure over a four year period foundation excavations were up to 15 m below the water table the anisotropic permeability of the norwich crag aquifer and foundation was determined by an iterative analytical technique applied to pumping tests at the pre construction stage an electrical resistance network analogue model using miniaturized resistors was a primary tool for groundwater drawdown predictions which with non linear finite element analyses led to the establishment of a drawdown settlement relationship used to control the effects on the adjacent operational sizewell a a quantitative assessment of the ingress of water through the as made diaphragm wall and the underlying london clay cut off stratum based on the pumping records is given la conception la construction et amelioration des performa

large scale fluid flow in the middle devonian presqu ile barrier western canada sedimentary basin saddle dolomite cements are regionally extensive in the middle devonian presqu9ile or keg river barrier and are spatially associated with mississippi valley type mineralization at pine point northwest territories from northeastern british columbia to pine point over a lateral distance of 400 km these dolomite cements show general trends of decreasing 87 sr 86 sr ratios 0 7106 to 0 7081 and homogenization temperatures 178 to 92 c with some increase in 18 o values 16 to 7 pdb these regional trends suggest that hotter and more radiogenic basinal fluids moved eastward updip along the presqu9ile barrier and mixed with cooler ambient formation waters these movements of basinal fluids were probably related to tectonic thrusting and compression sedimentary loading and tectonic uplift on the western margin of the western canada sedimentary basin which began to form during late jurassic to early cretaceous time and climaxed during the late cretaceous to paleocene the middle devonian presqu9ile barrier appears to have acted as a deeply buried regional conduit system that played an important role in focusing and channeling these basinal fluids these regional fluid flows appear to have been responsible for extensive burial dolomitization secondary migration of hydrocarbons and local mississippi valley type mineralization in the western canada sedimentary basin

non darcian flow toward a larger diameter partially penetrating well in a confined aquifer in this study non darcian flow to a larger diameter partially penetrating well in a confined aquifer was investigated the flow in the horizontal direction was assumed to be non darcian and described by the izbash equation and the flow in the vertical direction was assumed to be darcian a linearization procedure was used to approximate the nonlinear governing equation the laplace transform associated with the finite cosine fourier transform was used to solve such non darcian flow model both the drawdowns inside the well and in the aquifer were analyzed under different conditions the results indicated that the drawdowns inside the well were generally the same at early times under different conditions and the features of the drawdowns inside the well at late times were similar to those of the drawdowns in the aquifer the drawdown in the aquifer for the non darcian flow case was larger at early times and smaller at late times than their counterparts of darcian flow case the drawdowns for a partially penetrating well were the same as those of a fully penetrating well at early times and were larger than those for a fully penetrating well at late times a longer well screen resulted in a smaller drawdown in the aquifer at late times a larger power index n in the izbash equation resulted in a larger drawdown in the aquifer at early times and led to a smaller drawdown in the aquifer at late times a larger well radius led to a smaller drawdown at early times but it had little impact on the drawdown at late times the wellbore storage effect disappears earlier when n is larger

using partial penetrating wells and curtains to lower the water level of confined aquifer of gravel abstract to address the difficulties of penetrating and dewatering of a deep and thick confined aquifer of gravel a dewatering approach that considers the anisotropic hydraulic conductivity of aquifer co work of partial penetrating curtains and partial penetrating pumping wells was developed using the deep foundation pit of the southern ventilation shaft of metro line 1 in hangzhou china as an example a numerical simulation model based on finite difference method was established to invert the parameters and determine the co work of partial penetrating curtains and wells the anisotropic characteristic of the aquifer indicated that the three dimensional flow caused by partial penetrating wells produced bigger drawdown by co working with the partial penetrating wells the partial penetrating curtains changed the horizontal flow to a vertical one lengthened the flow path and consumed more energy to produce bigger drawdown three simulation schemes with different lengths depths of well screen and pumping rates were performed the results indicated that a short screen for the pumping well embedded by curtains resulted in the biggest drawdown with minimum pumping rate based on numerical simulations four pumping wells with 4 m long screens embedded by curtains were installed inside the excavation zone the water level declined to the required drawdown which indicated that the approach is feasible and can provide solutions to problems on similar projects

the nature and origin of venusian canali venusian canali have many characteristics of terrestrial rivers notably cutoff meanders braiding point bars and deltas which required both erosion and sediment transport this implies that the canali were not formed by construction but rather by thermal or mechanical erosion we have evaluated the relative importance of these latter two mechanisms assuming a basaltic substrate and a surface temperature similar to that currently prevailing 470 c in order to have thermally eroded the canali the liquid must have been turbulent and at a temperature above that of the basalt solidus the most plausible candidates for this liquid are basalt and komatiite lavas however at realistic flow rates and extrusion temperatures flow of basaltic lava is laminar and therefore basaltic lavas could not have thermally eroded the canali although komatiite flow is initially turbulent the lava will cool in hours to its solidus temperature whereas it will take months to thermally erode canali by elimination only mechanical erosion can adequately explain canali formation based on incision and lateral migration rates for terrestrial rivers it could take from 5 years in unconsolidated regolith to 8 105 years in solid basalt to mechanically erode a typical venusian canale these estimates require that the eroding agent had a solidus temperature close to the venusian surface temperature and that viscosities remained low until solidification only halogen rich alkali carbonatite and sulfur lavas meet these criteria and only the former could have been present in sufficient volumes to form the canali we propose that the canali were mechanically eroded by such carbonatite lavas and that the latter originated from the fusion of anhydrous recycled crust which had been altered by interaction with a co2 so2 and halogen rich atmosphere

characteristics of groundwater seepage with cut off wall in gravel aquifer i field observations1 this paper presents a case history of the leakage behavior during dewatering tests in the gravel strata of an excavation pit of a metro station in hangzhou china the groundwater system at the tes

non darcian flow in fractured rocks with a linear flow pattern abstract groundwater flow through fractured rocks deserves special study due to its deviation from the classical darcian solutions the occurrence of linear flow towards extensive or medium length dipping geological structures such as faults joints contact surfaces and fractures is rather common especially in igneous and metamorphic rock environments in general these structural elements have permeabilities of many orders of magnitude greater than the host rock drilling any well in these structures is preferable since the hydraulically connected combination of the well and these main structures provides a surface which has an area several times greater than the well surface as a result of such combinations flow lines become parallel well losses are reduced and abstraction of water becomes easier most of the host rock of the main structures has fractures and fissures secondary flow in these conduits violates the darcian law because the type of flow becomes turbulent especially at high velocities hence it is the main purpose of this paper to present an analytical solution to account for the turbulent flow by means of the forchheimer law the results are documented in the form of type curves which give opportunity for practicing hydrogeologists to determine the aquifer parameters by a type curve matching procedure various graphs are presented to compare darcian and non darcian flows in fractured media application of the methodology developed herein is shown for some realistic field data

surface subsidence and drawdown of the water table due to pumping a fully coupled numerical method is presented for the analysis of the pumping of groundwater taking into account the drawdown of the water table the surface subsidence due to pumping is first studied assuming that the water table is not lowered as the groundwater is withdrawn this solution is then compared with the solution for the case in which the drawdown of the water table is considered extensive parametric studies were carried out to provide non dimensionalized design charts for surface subsidence and drawdown of the water table due to pumping l article presente une methode numerique permettant d analyser le pompage des eaux souterraines en prenant en compte le rabattement de la surface libre de la nappe la subsidence en surface du sol due au pompage est etudiee en supposant que la surface piezometrique ne baisse pas au fur et a mesure que l eau est pompee cette solution est ensuite comparee a la solution obtenue avec un rabattement de la surface piezometrique des etudes parametriques exten

a model of orientation of subcrystals in saddle dolomite abstract saddle dolomite crystals are composed of subcrystals that are slightly overlapped rotated and tilted with respect to each other the subcrystal arrangement resembles a screw like pattern the c axes of subcrystals are skew lines their directions change from horizontal to steeply inclined relative to the substrate in thin section the traces of the c axes of subcrystals simulate a divergent or convergent pattern which is the cause of sweeping extinction typical of saddle dolomite

evaluation of the effectiveness of an alternative to control groundwater inflow during a deep excavation into confined aquifers this paper presents a case study of groundwater control for a deep excavation into confined aquifers in fuzhou china field pumping tests were first carried out prior to the excavation to investigate the groundwater conditions at the site and as well as to evaluate the feasibility of previous designed dewatering systems 34 m diaphragm walls together with pumping wells the results showed that under the condition of previous dewatering systems it would have been extremely difficult to safely lower the water level inside the excavation a co working scenario of partially penetrating curtains and horizontal waterproof curtain with jet grouting was then proposed to control groundwater inflows additional water tightness assessment tests wat were then performed that allowed to confirm the efficiency of the proposed method from the feedbacks of wat this proposed scenario not only successfully lowered the water lever inside the excavation below the excavation bottom maximum drawdown up to 14 9 m but also it minimized the drawdown outside the excavation less than 0 2 m furthermore an approach was proposed to approximately estimate the hydraulic conductivity of the jet grouting at the real site from the result of wat the hydraulic conductivity of jet grouted soil is three orders of magnitude lower than that of the original sediments

solubility of anhydrite caso4 in nacl h2o solutions at high pressures and temperatures applications to fluid rock interaction anhydrite solubility in h2o nacl solutions was measured at 6 14 kbar 600 800 c and nacl mole fractions xnacl of 0 0 3 in piston cylinder apparatus solubilities were determined by weight changes of natural anhydrite in perforated pt envelopes confined with fluid in larger pt capsules in initially pure h2o at 10 kbar and 800 c caso4 concentration is low 0 03molal though much larger than at the same temperature and 1 kbar hematite buffered experiments showed slightly lower solubilities than unbuffered runs caso4 solubility increases enormously with nacl activity at 800 c and 10 kbar and xnacl of 0 3 caso4 molality is 200 times higher than with pure h2o whereas caso4 solubility in pure h2o decreases with rising t at low t and p the high p results show that anhydrite solubility increases with t at constant p at all xnacl investigated the effects of salinity and temperature are so great at 10 kbar that critical mixing between sulfate rich hydrosaline melts and aqueous salt solutions is probable at 900 c at xnacl 0 3 recent experimental evidence that volatile laden magmas crystallizing in the deep crust may evolve concentrated salt solutions could in light of the present work have important implications regarding such diverse processes as mount pinatubo type s rich volcanism high fo2 regional metamorphism and emplacement of porphyry cu mo ore bodies where anhydrite hematite alteration and fluid inclusions reveal the action of very oxidized saline solutions rich in sulfur

drainage equations and non darcian modelling in coarse porous media or geosynthetic materials abstract in coarse porous media darcy s law is not valid because of turbulence different alternative laws have been proposed like forchheimer s or izbash s law in the present study these two laws were experimentally investigated and have been shown to be equally suitable to describe the flow equation in different coarse materials namely gravel materials and geosynthetic products izbash s law v n n i has been preferred to derive drainage equations because it is in continuity with darcy s law and facilitates the development of an analytical solution it has been introduced in boussinesq s equation which has been solved by a semi analytical semi numerical method general equations for the drainage of coarse porous media have been derived and incorporated into the drainage model sidra which predicts water table elevations and drain flow rates for a given net recharge this allows for comparison i between predicted darcian and non darcian behaviours and ii between predicted drainage functionings of different coarse materials water table elevations are shown to be much more sensitive to non darcian flow equation and to the hydraulic properties of the materials than drain flow rates response surface maps of an objective function based on the nash criterion show that the water table predictions are almost not sensitive to drainable porosity values they also indicate that the two parameters of the izbash flow equation and n are dependent for water table prediction based on this result a method is proposed to determine hydraulic properties and drainage systems yielding similar water table elevations the results can help choosing between classical granular materials and geocomposite products in drainage systems such as leachate collection systems of landfills

evaluation of optimized depth of waterproof curtain to mitigate negative impacts during dewatering abstract dewatering using a combination of waterproof curtain and pumping wells is commonly adopted to ensure the stability of foundation pits in multi aquifer strata however dewatering is likely to result in environmental problems this paper investigates the impact on surroundings owing to the interaction between the waterproof curtain and pumping wells by numerical simulation the depth of the diaphragm wall penetrating the dewatering aquifer d and the filter length of pumping wells l are varied in the simulation the relationship between approximate hydraulic gradient i or ground settlement outside the foundation pit s with curtain depth ratio rd d over the thickness of the dewatering confined aquifer ha or filter length ratio rl l ha can be divided into three change parts namely initial gradual middle sharp and final gentle part three values of rd and rl namely effective suggested and control value are proposed rd and rl should vary between the effective and control value the suggested value of rd and rl is recommended in actual engineering by comprehensive consideration the effective suggested and control value of rd can be calculated by a linear equation according to the value of rl

low velocity non darcian flow to a well fully penetrating a confined aquifer in the first kind of leaky aquifer system in this study we use a finite difference method to solve low velocity non darcian flow to a well in the first kind of leaky aquifer system flow in the confined aquifer is assumed to be darcian and horizontal whereas flow in the aquitard is assumed to be non darcian and vertical the threshold hydraulic gradient existence of non darcian flow in low permeability porous media is employed to describe the non darcian flow in the aquitard a numerical solution has been obtained by using a finite difference method this solution is compared with the previous solution for darcian flow case in leaky aquifer system the error has been analyzed the comparison of this study and darcian flow case hantush and jacob 1955 in leaky aquifer system indicates that the error is very small and can be neglected however the hydrogeological parameter calculation of leaky aquifer system is remarkably influenced by low velocity non darcian flow in aquitard for the inflection point method hantush 1956 the absolute values of estimated errors for coefficient of transmissibility of confined aquifer and vertical hydraulic conductivity of aquitard show negative relationship with the pumping rate for the type curve fitting method walton 1962 the estimated errors for coefficient of transmissibility and elastic drainable porosity of confined aquifer are very small under small pumping rate in general the estimated errors for coefficient of transmissibility and elastic drainable porosity of confined aquifer can be controlled under certain level through adjusting pumping rate the estimated error of vertical hydraulic conductivity of aquitard is quite large no matter which method is used even up to nearly 300

the solubility of cepo4 monazite and ypo4 xenotime in kcl h2o fluids at 800 c and 1 0 gpa implications for ree transport in high grade crustal fluids

characteristics of groundwater seepage with cut off wall in gravel aquifer ii numerical analysis this paper presents a numerical investigation into the leakage behavior of cut off walls in gravel strata due to dewatering in a deep excavation pit the calculated values of the groundwater head and surface settlement using a model agree well with the measured values values of the hydraulic conductivity k and storage coefficient ss of each soil layer are obtained from the test results when the cut off wall is 43 m deep the leakage through the cut off wall in gravel is analyzed by considering a variation in hydraulic conductivity in different sections of the cut off wall the simulated results show that a significant leakage occurred in the 54 m deep cut off wall although leakage did occur in the full cut off wall in the confined aquifer the full cut off wall is still more efficient in preventing groundwater seepage than the partial cut off wall the relative depths of the cut off wall and of the wells have a significant effect on ground surface settlement during the withdrawal of groundwater the

magmatic fluids in the fen carbonatite complex s e norway three different types of carbonatite magma may be recognized in the cambrian fen complex s e norway 1 peralkaline calcite carbonatite magma derived from ijolitic magma 2 alkaline magnesian calcite carbonatite magma which yielded biotite amphibole sovite and dolomite carbonatite and 3 ferrocarbonatite liquids related to 2 and or to alkaline lamprophyre magma damjernite apatite formed during the pre emplacement evolution of 2 contains inclusions of calcite and dolomite devitrified mafic silicate glass and aqueous fluid all of these inclusions have a magmatic origin and were trapped during a mid crustal fractionation event p 4 kbars t 625 c where apatite and carbonates precipitated from a carbonatite magma which coexisted with a mafic silicate melt the fluid inclusions contain water dissolved ionic species mainly nacl with minor polyvalent metal salts and in some cases co2 two main groups of fluid inclusions are recognized type a co2 bearing inclusions of approximate molar composition h2o 88 90 co 27 5 nacl 5 d 0 85 0 87 g cm3 type b co2 free aqueous inclusions with salinities from 1 to 24 wt nacleq and densities betwen 0 7 and 1 0 g cm3 more strongly saline type b inclusions salinity ca 35wt d 1 0 to 1 1 g cm3 contain solid halite at room temperature and occur in overgrowths on apatite type a inclusions probably contain the most primitive fluid from which type b fluids have evolved during fractionation of the magmatic system type b inclusions define a continuous trend from low towards higher salinities and densities and formed as a result of cooling and partitioning of alkali chloride components in the carbonatite system into the fluid phase available petrological data on the carbonatites show that the fluid evolution in the fen complex leads from a regime dominated by juvenile co2 h2o fluids during the magmatic stage to groundwater derived aqueous fluids during post magmatic reequilibration

on the aquitard aquifer interface flow and the drawdown sensitivity with a partially penetrating pumping well in an anisotropic leaky confined aquifer summary a mathematical model for describing groundwater flow to a partially penetrating pumping well of a finite diameter in an anisotropic leaky confined aquifer is developed the model accounts for the jointed effects of aquitard storage aquifer anisotropy and wellbore storage by treating the aquitard leakage as a boundary condition at the aquitard aquifer interface rather than a volumetric source sink term in the governing equation which has never developed before a new semi analytical solution for the model is obtained by the laplace transform in conjunction with separation of variables specific attention was paid on the flow across the aquitard aquifer interface which is of concern if aquitard and aquifer have different pore water chemistry moreover laplace domain and steady state solutions are obtained to calculate the rate and volume of total leakage through the aquitard aquifer interface due to pump in a partially penetrating well which is also useful for engineers to manager water resources the sensitivity analyses for the drawdown illustrate that the drawdown is most sensitive to the well partial penetration it is apparently sensitive to the aquifer anisotropic ratio over the entire time of pumping it is moderately sensitive to the aquitard aquifer specific storage ratio at the intermediate times only it is moderately sensitive to the aquitard aquifer vertical hydraulic conductivity ratio and the aquitard aquifer thickness ratio with the identical influence at late times

groundwater control around a large basement melbourne s crown casino was constructed on a site bordering the yarra river and underlain by problem soils of the coode island silt formation the development needed to provide two levels of basement car park over the entire site an innovative approach to groundwater control around the excavation was required to avoid depressurisation of adjoining soils leading to settlements analysis showed a conventional bentonite cut off wall would still allow depressurisation by lateral flow through the coode island silt during the construction period the high cost and construction difficulty of a very low permeability wall mitigated against it an hydraulic wall was proposed in conjunction with a conventional cut off wall this comprised a curtain of wick drains surrounding the cut off wall and charged with water control of seepage through an underlying aquifer by a cut off wall was considered but a more cost effective method using recharge by wells was adopted when shown necessary monitoring of groundwater p

surface settlements at a soft soil site due to bedrock dewatering abstract construction of a 16 m deep 55 m wide almost square underground structure through 8 m of soft soils and 8 m of sandstone and siltstone led to the development of widespread settlements the affected area extended to distances of over 200 m from the perimeter of the structure the floor slab of the underground structure was not designed for water pressure thus operation of the structure requires continuous pumping of seepage water collected at a sump located at the lowermost elevation within the structure subsurface investigation and monitoring data obtained over 5 75 year period following the construction of the structure indicated that the settlement resulted from consolidation of soft soils due to depressurization of an aquifer within the underlying bedrock caused by continuous dewatering needed for the operation of the structure an analytical study was undertaken to project the long term settlement a simple analytical model could be used to simulate the complex hydrogeological problem reasonably the details of hydrogeologic setting subsurface investigation and monitoring activities and the analytical model for projecting long term settlements are presented in this paper

fluid inclusions in apatite from jacupiranga calcite carbonatites evidence for a fluid stratified carbonatite magma chamber carbonatites of the jacupiranga alkaline carbonatite complex in sao paulo state brazil were used to investigate mineral fluid interaction in a carbonatite magma chamber because apatite showed a marked discontinuity between primary fluid inclusion rich cores and fluid inclusion poor rims sylvite and burbankite apatite pyrite chalcopyrite and ilmenite are the common phases occurring as trapped solids within primary fluid inclusions and reflect the general assemblage of the carbonatite the apatite cores had higher sr and ree concentrations than apatite rims due to the presence of fluid inclusions into which these elements partitioned a positive cerium anomaly was observed in both the core and rim of apatite crystals because oxidised ce4 partitioned into the magma the combined evidence from apatite chemistry fluid inclusion distribution and fluid composition was used to test the hypotheses that the limit of fluid inclusion occurrence within apatite crystals arises from 1 generation of a separate fluid phase 2 utilization of all available fluid during the first stage of crystallization 3 removal of crystals from fluid rich magma to fluid poor magma 4 an increase in the growth rate of apatite or 5 escape of the fluids from the rim of the apatite after crystallization the findings are consistent with fractionation and crystal settling of a carbonatite assemblage in a fluid stratified magma chamber secondary fluid inclusions were trapped during a hydrothermal event that precipitated an assemblage of anhedral crystals strontianite carbocernaite barytocalcite barite and norsethite pyrophanite magnesian siderite and baddeleyite ancylite ce monazite ce and allanite the sr and ree rich nature of the secondary assemblage and lack of a positive cerium anomaly indicate that hydrothermal fluids have a similar source to the primary magma and are related to a later carbonatite intrusion

sulfate brines in fluid inclusions of hydrothermal veins compositional determinations in the system h2o na ca cl so4 sulfate is among the most abundant ions in seawater and sulfate bearing brines are common in sedimentary basins among other environments however the properties of sulfate bearing fluid inclusions during microthermometry are as yet poorly constrained restricting the interpretation of fluid inclusion compositions where sulfate is a major ion the schwarzwald mining district on the eastern shoulder of the upper rhinegraben rift is an example of a geologic system characterized by sulfate bearing brines and constraints on the anion abundances chloride versus sulfate would be desirable as a potential means to differentiate fluid sources in hydrothermal veins in these regions here we use the pitzer type formalism to calculate equilibrium conditions along the vapor saturated liquidus of the system h2o na ca cl so4 and construct phase diagrams displaying the predicted phase equilibria we combine these predicted phase relations with microthermometric and crush leach analyses of fluid inclusions from veins in the schwarzwald and upper rhinegraben to estimate the compositions of these brines in terms of bulk salinity as well as cation and anion loads sodium versus calcium and chloride versus sulfate these data indicate systematic differences in fluid compositions recorded by fluid inclusions and demonstrate the application of detailed low temperature microthermometry to determine compositions of sulfate bearing brines thus these data provide new constraints on fluid sources and paleo hydrology of these classic basin hosted ore forming systems moreover the phase diagrams presented herein can be applied directly to compositional determinations in other systems