leveling vs insar in urban underground construction monitoring pros and cons case of la sagrera railway station barcelona spain abstract monitoring is required when dewatering underground construction sites to anticipate unexpected events and preserve nearby existing structures and or buildings the most accurate and widespread monitoring method to measure displacements is leveling a point like surveying technique that typically allows for tens of discrete in situ sub millimeter measures per squared kilometer another emerging technique for mapping soil deformation is the interferometric synthetic aperture radar insar method which is based on sar images acquired from orbiting satellites this remote sensing technique can provide better spatial point density than leveling more extensive spatial coverage and lower cost acquisitions this paper analyses compares and discusses leveling and advanced multi temporal insar measurements when they are used to measure the soil deformation induced by the dewatering associated with underground constructions in urban areas this comparison which has not been considered in previous works is of paramount importance to ascertain the most suitable technique or combination of techniques in these contexts to do so an experiment was performed in the future railway station of la sagrera barcelona spain in which leveling and advanced multi temporal insar were used to quantify ground deformation by dewatering the results showed that soil displacements measured by leveling and insar were not always consistent in the context of soil deformation measurements produced by dewatering in urban areas insar measurements appear to be more accurate for investigating soil deformation whereas leveling was more appropriate for quantifying the real impact on the nearby buildings

model test on partial expansion in stratified subsidence during foundation pit dewatering abstract partial expansion was observed in stratified subsidence during foundation pit dewatering however the phenomenon was suspected to be an error because the compression of layers is known to occur when subsidence occurs a slice of the subsidence cone induced by drawdown was selected as the prototype model tests were performed to investigate the phenomenon the underlying confined aquifer was generated as a movable rigid plate with a hinge at one end the overlying layers were simulated with remolded materials collected from a construction site model tests performed under the conceptual model indicated that partial expansion occurred in stratified settlements under coordination deformation and consolidation conditions during foundation pit dewatering rapid drawdown resulted in rapid subsidence in the dewatered confined aquifer the rapidly subsiding confined aquifer top was the bottom deformation boundary of the overlying layers non coordination deformation was observed at the top and bottom of the subsiding overlying layers the subsidence of overlying layers was larger at the bottom than at the top the layers expanded and became thicker the phenomenon was verified using numerical simulation method based on finite difference method compared with numerical simulation results the boundary effect of the physical tests was obvious in the observation point close to the movable endpoint the tensile stress of the overlying soil layers induced by the underlying settlement of dewatered confined aquifer contributed to the expansion phenomenon the partial expansion of overlying soil layers was defined as inversed rebound the inversed rebound was induced by inversed coordination deformation compression was induced by the consolidation in the overlying soil layers because of drainage partial expansion occurred when the expansion exceeded the compression considering the inversed rebound traditional layer wise summation method for calculating subsidence should be revised and improved

large calcite and bulk rock volume loss in metacarbonate xenoliths from the querigut massif french pyrenees chemical mass transfer was quantified in a metacarbonate xenolith enclosed within the granodiorite of the querigut massif pyrenees france mass balance calculations suggest a strong decrease of cao sro and co2 contents up to 90 correlated with a decrease of modal calcite content as the contact is approached most other chemical elements behave immobile during metasomatism they are therefore passively enriched only a small increase of sio2 al2o3 and fe2o3 contents occurs in the immediate vicinity of the contact hence in this study skarn formation is characterized by the lack of large chemical element influx from the granitoid protolith a large decrease of the initial carbonate volume up to 86 resulted from a combination of decarbonation reactions and loss of cao and co2 the resulting volume change has potentially important consequences for the interpretation of stable isotope profiles the isotope alteration could have occured over greater distances than those observed today

dewatering induced subsidence during excavation in a shanghai soft deposit foundation dewatering has become a major cause of land subsidence in shanghai the burial depth of foundations in relation to geotechnical construction works is less than 75 m and the corresponding groundwater includes phreatic low pressure artesian and the first confined aquifers based on the geological and hydrogeological conditions beneath shanghai methods of dewatering may be divided into three modes and further five patterns according to the insertion depth of the dewatering retaining system the most common dewatering mode aims to reduce the water pressure in the confined aquifer by setting the dewatering wells inside the pit whilst the retaining walls are buried in the confined aquifer and partially cut off the confined aquifer layer to predict the settlement due to foundation dewatering numerical models are generally adopted which are similar to those used to predict land subsidence induced by regional groundwater withdrawal however since foundation dewatering is conducted along with the setting of retaining walls and foundation pit excavation which differs from regional groundwater withdrawal interactions between the retaining wall dewatering well the dewatering excavation and dewatering recharge are important factors affecting the analytical model since the grading of the shallow soil layers is different stratified settlement characteristics of the shallow soil strata and seepage erosion which results in additional deformation need to be given particular consideration

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

settlements around pumping wells analysis of influential factors and a simple calculation procedure abstract estimated and measured settlements caused by pumping rarely agree several reasons could explain this mismatch including the influence of layering the mechanical parameters used in the predictions or the relationship between settlements and drawdown we analyze the influence of the above issues by investigating the mechanical response of pumped elastic porous media under different conditions a radially symmetric conceptual model is considered and several hydro mechanical simulations are performed varying the boundary conditions the size of the modeled domain and the presence or not of an overlying layer the simplicity of the considered problem allows us to compare our results with existing analytical solutions to identify the role of each variable on pumping settlements and to generalize the results the most relevant results are as follows 1 settlements are proportional to drawdown only outside a circle of radius equal to 0 7 times the thickness of the pumped porous medium inside they are virtually constant which leads to two simple procedures for computing pumping settlements 2 poorly conductive layers located above or below a pumped porous medium with higher hydraulic conductivity reduce and smooth settlements 3 boundary constraints affect the local specific storage coefficient and the displacements occurred 4 the specific storage coefficient evaluated by interpreting pumping tests with the cooper and jacob method 1946 leads to overestimation of the actual young s modulus of the soil the main conclusion is that settlements are less differential than expected near pumping wells still they must always be evaluated acknowledging the nature of layering the boundary constraints and carefully selecting the mechanical parameters of the soil

microstructures of different soil layers caused by the high rise building group in shanghai the engineering characteristics of soils are controlled by the state of the microstructure of soils to a great extent with the withdrawal of groundwater controlled reasonably the engineering environmental effect of the high rise building group becomes the main cause of land subsidence in shanghai this paper studied the microstructure of each soil layer under the building loads in the centrifuge model by the scanning electron microscopy and the mercury intrusion porosimetry mip for qualitative analysis and quantitative analysis respectively the shape size and contact condition of the basic unit of the soil microstructure were analyzed the pore structure of each soil layer was studied by mip and the pore distribution of each soil layer was studied by the fractal theory the ink bottle effect exists in the intrusion stage in the mip test there are four different fractal dimensions for silty clay of layer no 4 and clayey soil of layer no 8 and three different fractal dimensions for silty sand of layer no 7 and layer no 9 the micro and macro mechanisms of land subsidence caused by the high rise building group were analyzed

field pumping experiments and numerical simulations of shield tunnel dewatering under the yangtze river the water conveyance tunnel for the changshu power plant is located under the riverbed of the yangtze river the tunnel passes through muddy silty clay and silty clay because quicksand and water bursting occurred in the tunnel due to confined water and biogas in layers and it can be concluded that the tunnel is intensely affected by the confined aquifer layer to obtain more accurate hydrogeological parameters of the aquifers in situ pumping tests were carried out the tests were divided into five stages and during the test process the flux and drawdown were monitored based on the measured data the permeability coefficients of the confined aquifers were calculated by the formula and numerical methods the calculated results indicate that the parameters derived from the two methods are very similar the hydraulic connections of the confined aquifers were also inversed from the pumping tests the dewatering schedule for tunnel recovery was simulated using modflow based on the numerical simulation 21 wells whose screens were installed in layer were designed for the dewatering operation during pumping the water levels declined to the drawdown requirement the results indicate that the dewatering approach is feasible for tunnel recovery and can provide solutions for similar projects

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

evaluation of the blocking effect of retaining walls on groundwater seepage in aquifers with different insertion depths abstract in the design of a deep retaining wall it is necessary to consider the blocking effect on groundwater seepage of retaining walls in aquifers in this study both laboratory tests and numerical simulation with finite element method fem were adopted to investigate the blocking effect on groundwater seepage under different insertion depths of retaining wall in aquifer laboratory tests were conducted to analyze this blocking effect in an unconfined aquifer the test results indicate that the effective insertion depth ratio j of a retaining wall in shanghai aquifer sand is about 70 a three dimensional numerical model 3d fem was conducted to analyze the laboratory test results the fem results show that fem is a reliable method to analyze the blocking effect on groundwater seepage in an aquifer based on the same aforementioned procedure a 3d fem model is established to investigate the blocking effect in the confined aquifer in shanghai deposit both laboratory test and fem results show that drawdown of groundwater level decreases with an increase of the insertion depth ratio j of retaining structures in an aquifer the optimal value of j approximately 70 is achieved for retaining wall based on the synthetic results from laboratory test fem analysis and the equation of pujades et al for either unconfined aquifers or confined aquifers of shanghai

oxygen isotopic exchange at an igneous intrusive contact oxygen isotope exchange at the contact of an igneous intrusion with host rock of different initial 18 o is examined for two examples in the santa rosa range nevada exchange zones near the contacts may have formed solely by diffusive transport of oxygen through the rock however the 18 o variation within the zones may also be consistent with fluid flow across the intrusive host rock contact perhaps due to the exsolution of magmatic water as the intrusion crystallized to explain the observed width of the exchange zones several mechanisms of diffusion are examined solid statediffusion either volume diffusion through silicate minerals or grain boundary diffusion is 4 5 orders of magnitude too slow diffusion through a water rich fluid phase released by dehydration reactions during contact metamorphism can be sufficiently rapid to produce the exchange zones the narrow width of these zonesimplies that only a small fraction of the water that could have been released by metamorphic dehydration reactions formed connected pathways through the rock

a mathematical model for seepage of deeply buried groundwater under higher pressure and temperature summary deeply buried groundwater such as brine is an important industrial raw material with high economic value because brine frequently exists under higher temperature and pressure the quantitative prediction of its seepage field is very difficult here we study the migration of deeply buried groundwater by using a numerical simulation based on laboratory test results in particular we express the pressure and temperature variation of seepage parameters such as hydraulic conductivity k and specific storage coefficient s in terms of the corresponding variation of the solid skeleton s permeability k porosity n compressibility coefficient s and seepage fluid s viscosity and compressibility coefficient w then through mathematical transformation and linearization methods the mathematical model with pressure and temperature dependent coefficients is reduced to the same form as the standard one for seepage flow the results are successfully applied to the moxi structure in sichuan basin the results show that the effect of higher pressure and temperature should be taken into account for quantitative study of deeply buried groundwater and that the effects are easily included by the transformation of the mathematical model to standard form

field measurement of high temperature bulk reaction rates i theory and technique knowledge of metamorphic reaction rates is crucial to accurately interpret rock and mineral chemistry the local equilibrium assumption used in geochronology geothermobarometry and material flux estimates requires that local reaction rates among system phases are fast relative to local rates of p t x change natural metamorphic reaction rates are essentially unknown and difficulties and disagreements exist regarding extrapolations of existing laboratory data to natural conditions growing recognition of natural effects that could be attributed to slower reaction rates justifies the need for a field based quantification of reaction rates to assess the accuracy of lab based predictions we describe in detail the theory and methodology of a technique for extracting bulk reaction rates directly from isotopic data derived from natural samples baxter and depaolo 2000 reaction rates measured using this technique may be judiciously applied to isotopic exchange or net reaction kinetics in other natural systems the technique requires collection of whole rock and garnet 87sr 86sr data along a sampling traverse normal to a lithologic contact where there was prior to metamorphism a sharp isotopic discontinuity garnet data provide information on syn metamorphic conditions and the time interval for the exchange process forward modeling of the reactive transport process using numerical methods and the equations for diffusive reactive transport allow determination of the reaction rate and bulk sr diffusivity that provides the best fit to the data measurement of reaction rates is best constrained if an isotopic step is preserved at the contact the size of which is directly proportional to the bulk reaction rate this contribution is intended to serve as a template for future use and development of this technique to acquire natural reaction rate data from metamorphic systems

centrifuge modeling of land subsidence caused by the high rise building group in the soft soil area with the increase of the high rise buildings land subsidence induced by human activities becomes a major problem land subsidence occurs slowly but the accumulation results in the cracks in the road the damage to the pipelines and in the tilting or the cracking of the buildings with the withdrawal of groundwater controlled reasonably the engineering environmental effect of the dense high rise building group comes to be the main cause of land subsidence based on the high rise building group in the soft soil area in shanghai the mechanism of land subsidence is studied in this paper by the centrifuge model tests the central area of the building group has larger subsidence and the subsidence superimposition effect is obvious it can exceed the allowance and cause land subsidence hazard the land subsidence affected by the different building distances is also studied for smaller building distances the subsidence superimposition effect is more obvious the larger excess pore water pressure in the pile base supporting layer of the central area shows that the stress superimposition effect is larger the earth pressure under the buildings fluctuates by the disturbance of the pile tips

ground settlements and drawdown of the water table around an excavation in the vicinity of an excavation in a saturated soil ground settlements are often caused by the combined effects of stress release and drawdown of the water table these settlements may be crucial if the excavation is carried out in a congested area a case history of excavation adjacent to closely constructed blocks of buildings is discussed in this study ground settlements and water surface levels were monitored during the excavation period as the settlement of the surrounding area was of concern the authors have previously developed a fully coupled numerical method that allows the computation of the displacements and pore pressures in a soil taking account of the drawdown of the water table which may accompany excavation this method is used here for back analysis of a full scale excavation that has been comprehensively documented comparisons between the field measurements and the calculated results are given in this paper key words consolidation excavation finite element seepage transient

numerical study on the responses of groundwater and strata to pumping and recharge in a deep confined aquifer abstract groundwater drawdown and strata settlements induced by dewatering in confined aquifers can be relieved by artificial recharge in this study numerical simulations of a field multi well pumping recharge test in a deep confined aquifer are conducted to analyze the responses of groundwater and strata to pumping and recharge a three dimensional numerical model is developed in a finite difference software which considers the fluid mechanical interaction using the biot consolidation theory the predicted groundwater drawdown and ground settlements are compared to the measured data to confirm the validation of the numerical analysis of the pumping and recharge both numerical results and measured data indicate that the effect of recharge on controlling the groundwater drawdown and strata settlements correlates with the injection rate and well arrangements since the groundwater drawdown induced by pumping can be controlled by artificial recharge soil compression can be relieved by reducing the changes of effective stress of the soils consequently strata settlement induced by pumping can be relieved by artificial recharge and ground settlements can be eliminated if an appropriate injection rate and well arrangement are being determined moreover the changes of the pore pressure and seepage force induced by pumping and recharge will also result in significant horizontal deformations in the strata near the recharge wells

field tests of pumping recharge technology for deep confined aquifers and its application to a deep excavation abstract the execution of deep excavation above confined aquifers asks for dewatering measurements to reduce the hydrostatic pressure so that the safety of the deep excavation can be assured dewatering will inevitably cause deformations in the surrounding strata to reduce the dewatering induced strata movement an innovative pumping recharge technology has been developed in which the dewatering is carried out in the excavation and the recharge is conducted near the protected facilities however the capacity and efficiency of this technology in deep confined aquifers need to be further investigated this paper presents two in situ pumping recharge tests in a deep confined aquifer under a deep foundation pit the feasibility of artificial recharge in the deep confined aquifer has been verified by conducting a single well pumping and multi well recharge test with different discharge and injection rates then a multi well pumping recharge test was carried out in accordance with the requirement and circumstance of construction to evaluate the capacity and efficiency of recharge in controlling the drawdown and ground settlement the results showed that multi well recharge could form a water curtain which has a water proof function to reduce the groundwater drawdown meanwhile by controlling the groundwater head of the confined aquifer during the recharge the pumping induced settlement of the surrounding area can be reduced or even eliminated the pumping effect in the pit would be affected by the recharge around the protected facilities so it is necessary to take in situ pumping recharge tests to determine the layout of wells and the discharge and injection rate finally the artificial recharge was applied to the construction of a deep excavation in shanghai and the drawdown and the ground settlement around the protected buildings were effectively controlled by recharge

comments on the article erosion calderas origins processes structural and climatic control by karatson d thouret j c moriya i lomoschitz a 1999 bull volcanol 61 17 4 193

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

water quality effects on clogging rates during reclaimed water asr in a carbonate aquifer summary well clogging remains a major operational issue particularly in light of the increased attention being given to the reuse of reclaimed water through the method of aquifer storage and recovery asr in seasonally arid regions at a reclaimed water asr trial site in a limestone aquifer at bolivar in south australia rates of clogging were related to the quality of the injectant over a 4 year study period during which time water quality generally improved due to advancements in pretreatment rates of clogging within a 4 m radius of the asr well defined by changes in the relative intrinsic permeability of the aquifer were enhanced at higher levels of turbidity total nitrogen ntot and ph due to their resultant effects on particle filtration microbial growth and calcite dissolution respectively water quality changes due to the movement of the injectant to an observation well at a radius of 4 m verified these processes at this site acceptably low rates of short and long term clogging were achieved for turbidity

reaction weakening and emplacement of crystalline thrusts diffusion control on reaction rate and strain rate abstract in the southern appalachians the blue ridge piedmont crystalline thrust sheet was emplaced onto low grade late precambrian and paleozoic sedimentary rocks in the footwall along a basal detachment consisting of phyllosilicate rich mylonites phyllonites the phyllonites developed first by mechanical breakdown of feldspar followed by chemical breakdown to white mica in the presence of a pore fluid diffusion of solute in the pore fluid is the rate limiting step in controlling reaction rate and also the strain rate assuming solute diffusion follows the stokes einstein equation the shear strain rate is given by t 2 n k t 5 r x 2 for shear stress 20 mpa where n is a constant is a geometric factor k is boltzmann s constant t is absolute temperature is water viscosity r is the atomic radius of the diffusing species and x is the diffusion distance a bulk diffusion coefficient in the range of 10 10 to 10 12 m 2 s over distances of 10 100 m results in strain rates of 10 14 to 10 13 s 1 in the temperature range 200 400 c it is concluded that greenschist grade crystalline thrust sheets develop on pre existing basement faults that become weak during reaction softening and localize into high strain phyllonite zones in which pore fluid diffusion controls reaction rate and strain rate

a heat production model of a shield area and its implications for the heat flow heat production relationship the pikwitonei and sachigo subprovinces of central manitoba provide a cross sectional view of the superior province crust to constrain thermal models of the crust we measured heat production and thermal conductivity in rocks from this terrain using standard gamma ray spectrometry and divided bar techniques these data when used in a two dimensional model of shield crust show that estimates of surface heat flow and surface heat production yield the well known linear relationship between surface heat production and surface heat flow observed for heat flow provinces this demonstrates that determinations of heat production with depth based on inversion of the linear heat production heat flow relationship are non unique

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

barrier effect of underground structures on aquifers abstract impervious structures below the water table modify the natural groundwater flow in aquifers they act as barriers causing heads to rise upgradient and to fall downgradient we define the barrier effect as the increase in head loss across the barrier with respect to the natural conditions prior to construction we distinguish between regional the minimum head loss observed at long distances and local the maximum head loss observed close to the structure barrier effects we use numerical and analytical methods to derive semi empirical equations to quantify the two barrier effects for semi permeable partially penetrating or fully penetrating but finite in length and barriers with a by pass in confined aquifers the resulting equations depend on the barrier geometry and on the natural head gradient in the aquifer and they are easy to apply we test their validity at two construction sites obtaining excellent agreement between the computed and observed barrier effects

diffusion controlled growth of albite and pyroxene reaction rims the growth rates of albite and pyroxene enstatite diopside spinel reaction rims were measured at 1000 c and 700 mpa and found to be parabolic indicating diffusion controlled growth the parabolic rate constants for the pyroxene spinel rims in samples with 0 5 wt h2o added or initially vacuum dried at 25 c and 250 c are 1 68 0 09 0 54 0 05 and 0 25 0 06 m2 h respectively the values for albite rim growth in samples initially dried at 60 c and with 0 1 wt h2o added are 0 25 0 04 and 0 33 0 03 m2 h respectively the latter values were used to derive the product of the grain boundary diffusion coefficient d a where a sio2 naalo2 or naalsi 1 and the grain boundary thickness in albite the calculated d sio2 in the albite aggregate for the situations of two different water contents are about 9 9 10 23 and 1 4 10 22 m3 s 1 respectively both the rate constants and the calculated d a demonstrate that the effect of water content on the grain boundary diffusion rate in monomineralic albite and polymineralic pyroxene spinel aggregates is small consistent with recent studies of monomineralic enstatite and forsterite rims

environmental protection using dewatering technology in a deep confined aquifer beneath a shallow aquifer abstract this paper presents an innovative technology referred to as dual function well dfw which has been developed in order to reduce the construction costs of dewatering when excavation is conducted in an aquitard over a confined aquifer dfw technology is a method to lower both shallow groundwater and deep groundwater either separately or simultaneously using one well the dfw includes two or more independent screens corresponding to each aquifer and a valve is located between the screens inside a steel pipe when the valve is closed groundwater is pumped from the upper screen in the shallow aquifer when the valve is open groundwater is pumped from the screens in both the shallow and deep aquifers dfw technology is used to replace the traditional method involving two sets of wells in which the first set of wells pumps groundwater from the shallow aquifer and a second set pumps groundwater from the deep aquifer to investigate the effectiveness of dfw field pumping tests using a dfw were conducted and both groundwater head and settlement were monitored numerical simulation was adopted to simulate the results of the pumping tests comparison between the results from the dfw and from an ordinary mixing well indicates that the use of a dfw with the valve closed can reduce the pumping time from a deep aquifer and can reduce the ground settlement caused by dewatering the results indicate the dfw technology is feasible and effective

land subsidence due to groundwater drawdown in shanghai introduction shanghai is located on the deltaic deposit of the yangtze river as illustrated in fig 1 fig 2 shows the main geological strata the total thickness of the quaternary deposit is about 300 m shanghai geology office 1976 1979 excessive pumping of the groundwater caused compression of the quaternary deposit and subsidence in shanghai although several countermeasures including recharge of the groundwater have been adopted to mitigate the rate of subsidence up to the present the recorded cumulative subsidence has been 2 3 m in the central area of shanghai this subsidence has caused a lot of social problems the immediate problem is the increase in the possibility of flooding from 1981 to 1994 rainfall flooding occurred 22 times at a rate of almost twice per year liu 2001 the possibility of tidal flooding also increased from 1956 the height of the dike along the coast line was increased four times with the crest elevation rising from 5 m to 6 8 m other problems caused by the land subsidence are damage to the sewerage system road buildings and subway tunnels etc in shanghai the monitoring of land subsidence started in 1921 the history of land subsidence in the urban area of shanghai can be divided into two periods namely a rapid subsidence period 1921 1965 and a controlled period 1965 present zhang han 2002 however there has been a tendency for the subsidence rate to increase after 1990 in this paper the mechanism of land subsidence due to excessive pumping of groundwater is discussed first then the measured field data are presented and the relationship between groundwater pumping and land subsidence is discussed

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

geological and hydrogeological environment in shanghai with geohazards to construction and maintenance of infrastructures shanghai administrative region sar is located on the deltaic deposit of the yangtze river the bed rock under sar is generally buried in the depth of 200 m to 300 m except for several massifs where the bed rock is exposed to the ground surface the quaternary deposit in shanghai is soft sediment the variation of palaeoclimate influenced the sea level and resulted in a very complicated sedimentary environment the quaternary deposit in sar is composed of an alternated multi aquifer aquitard system maas the groundwater system is composed of one artesian aquifer and five confined aquifer layers with very high groundwater pressure head the maas was formed mainly within the warm geological era updated to 2 6 million years ago between two aquifers there is an aquitard which is composed of soft clayey soil formed mainly within the cold era the aquitards are composed of very soft clayey silt with very high compressibility and humus content the humus material was transformed into methane gas under a long term geological process with the development of economy the infrastructures were or are being constructed in the top shallow soft clayey deposit aquifer i and aquifer ii in sar the following geohazards occurred or possibly occur during the construction and maintenance of infrastructures i quicksand and piping hazards ii pumping induced hazards and recharge cutoff hazards iii long term settlement due to the seasonal fluctuation of groundwater level and iv geohazards of methane gas

triassic caldera at tioga pass yosemite national park california structural relationships and significance a middle or late triassic volcanic vent structure named the tioga pass caldera is exposed near the eastern boundary of yosemite national park california the caldera and related volcanic and plutonic rocks part of an early mesozoic continental margin magmatic arc in east central california formed prior to or during an episode of contractional deformation in the arc field relationships show that a widespread 222 ma rhyolitic ash flow tuff was erupted as an extensive outflow sheet during the formation of the caldera the late triassic lee vining canyon pluton may represent the subvolcanic magma chamber that was partially evacuated during the eruption of the ash flow tuff the caldera wall is now exposed as a highly irregular boundary between prevolcanic basement and intracaldera rocks that formed by a combination of initial caldera collapse and subsequent intracaldera intrusive and extrusive events intracaldera rocks include a thick section of triassic metasedimentary and metavolcanic rocks on gaylor peak together with the dana sequence on mount dana all of the triassic rocks of the saddlebag lake pendant later underwent strong deformation and metamorphism involving folding and thrusting during middle jurassic time the caldera fill is now exposed in the lower plate of an east vergent jurassic thrust which emplaced lower paleozoic through jurassic metasedimentary and metavolcanic rocks structurally above the caldera fill the results of this study indicate that caldera formation may occur in a contractional arc setting structural and stratigraphic relationships described here may also provide clues to recognition of other caldera and vent complexes in highly deformed metavolcanic sequences in the western united states and elsewhere

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

application of grey theory based model to prediction of land subsidence due to engineering environment in shanghai land subsidence is a common geological hazard the long term accumulation of land subsidence in shanghai has caused economic loss to the city since the 1990s the engineering structures have become a new cause of land subsidence many factors affect the process of land subsidence although such a process cannot be explicitly expressed by a mathematical formula it is not a black box whose internal structure parameters and characteristics are unknown therefore the grey theory can be applied to the prediction of land subsidence and provides useful information for the control of land subsidence in this paper a grey model gm gm 1 1 with unequal time intervals was used to predict the subsidence of a high rise building in the lujiazui area of shanghai and the results were compared with the monitored data the prediction of subsidence was also corroborated by laboratory tests and the results were compared with measured data and the predicted data by the adaptive neuro fuzzy inference system anfis it is found that the gm 1 1 with unequal time intervals is accurate and feasible for the prediction of land subsidence

dewatering of a deep excavation undertaken in a layered soil in order to carry out deep excavations under the water table in urban environments the safety of the work site and of the adjacent buildings is a major cause for concern one of the most common and effective methods of undertaking these excavations involves combining the cut and cover method with a dewatering system the success of a construction depends on the stability of the excavation bottom the effects produced outside the excavation by dewatering soil movements and or the state of the enclosure defects in the diaphragm walls this study proposes a realistic multidisciplinary procedure to address these issues the work emphasizes the importance of soil characterisation and underlines the need to perform a watertightness assessment test wtat before the excavation stage the procedure was applied to the excavation of a deep shaft of the high speed train hst tunnel in barcelona an earlier geological characterisation at large scale ruled out the use of deep pumping wells however a subsequent hydrogeological characterisation which involved borehole logging grain size analyses natural gamma ray and pumping tests revealed the presence of thin transmissive layers inside the low hydraulic conductivity materials the dewatering system was designed by considering different model scenarios and the safest design was selected for the excavation depths of the enclosure and of the pumping wells differed in accordance with the scenarios the impacts settlements due to pumping and the stability in each scenario were computed the state of the enclosure underwent a wtat before the start of the excavation but after constructing the enclosure to verify its low permeability the test consisted in pumping inside the enclosure and monitoring the groundwater behaviour outside the enclosure numerical interpretation of this test showed a defect in the diaphragm walls below the excavation bottom since this defect was not repaired because of its location below the bottom of the excavation the dewatering system had to be redesigned to ensure safety surface settlements which were also a source of concern were small they were computed using coupled hydro mechanical models

land subsidence and pore structure of soils caused by the high rise building group through centrifuge model test abstract in the urban area of shanghai the dewatering of groundwater was controlled strictly and the engineering environment effect of the high rise building group became to be the main cause of land subsidence in shanghai based on the high rise building group in the soft soil area in shanghai the mechanism of land subsidence was studied in this paper by the centrifuge model test the central area of the building group has larger subsidence and the subsidence superimposition effect is obvious it can exceed the allowance and cause land subsidence hazard the land subsidence affected by the different building distances was also studied for smaller building distances the subsidence superimposition effect is more obvious the engineering characteristics of soils are controlled by the state of pore structure of soils to a great extent the parameter of specific subsidence was put forward as a tie to analyze the relationship between land subsidence and pore structure of soils the pore structure of each soil layer was studied by the mercury intrusion porosimetry test mip and the pore distribution of each soil layer was studied by the fractal theory there are mainly macropores in silty clay of layer no 4 clayey soil of layer no 8 silty sand of layer no 7 and layer no 9 in shanghai the ink bottle effect exists in the intrusion stage in the mip test there are four different fractal dimensions in silty clay of layer no 4 and clayey soil of layer no 8 and three different fractal dimensions in silty sand of layer no 7 and layer no 9

deformation characteristics of a clayey interbed during fluid injection surface deformation due to fluid withdrawal has long been observed at the surface above aquifers and oil reservoirs uplift associated with fluid injection has also been observed although the processes of subsidence and uplift are reversible in a poroelastic setting the presence of clayey interbeds can result in ground deformation behavior non reversible because of their low permeability and nonlinear behavior in this investigation a cam clay model is used in conjunction with a poroelastic model to simulate the presence of a laterally extensive lens shaped clayey interbed in a sandstone aquifer during fluid injection spatial and temporal changes associated with this interbed during aquifer pressurization are captured and can be clearly differentiated from the deformation of the surrounding poroelastic aquifer formation results for pore pressures and ground surface deformation patterns can be categorized into three distinct time intervals an early time interval where the aquifer is pressurized but not the interbed leading to a lower region above the interbed an intermediate time interval in which the interbed pressures slowly increase approaching the pressure of the adjacent aquifer leading to a potentially large surface uplift above the interbed and a late time interval in which pressure equilibration is achieved between the interbed and aquifer and a highly non symmetrical irregular surface deformation pattern results which may be higher or lower than the background depending on the interbed characteristics reservoir configuration is found to be an important factor influencing ground deformation behavior with more obvious deformation always occurring in a laterally confined aquifer as opposed to a laterally infinite aquifer

study on land subsidence under different plot ratios through centrifuge model test in soft soil territory since the mid 1990s multi storied buildings high rise buildings and skyscrapers have been emerging due to the new round of great scale development on the soft soil littoral land subsidence in soft soil areas caused by engineering environmental effect especially by construction of high dense building groups attracts more and more attention the plot ratio may be one of the most important factors on engineering induced land subsidence thus three geotechnical centrifugal model tests were conducted under three conditions of different plot ratios to study the ground settlement mechanism of high dense building groups in soft soil territory it is concluded that the subsidence superimposition effect is obvious in the central area of high dense building groups the settlement increases with the growth of plot ratio the urban planning department should take this subsidence situation into account when determining the construction plot ratio to utilize the earth more aptly and safely

erosion calderas origins processes structural and climatic control the origin and development of erosion modified erosion transformed and erosion induced depressions in volcanic terrains are reviewed and systematized a proposed classification addressing terminology issues considers structural geomorphic and climatic factors that contribute to the topographic modification of summit or flank depressions on volcanoes breaching of a closed crater or caldera generated by volcanic or non volcanic processes results in an outlet valley under climates with up to 2000 2500 mm annual rainfall craters and calderas are commonly drained by a single outlet the outlet valley can maintain its dominant downcutting position because it quickly enlarges its drainage basin by capturing the area of the primary depression multi drained volcanic depressions can form if special factors e g high rate geological processes such as faulting or glaciation suppress fluvial erosion normal fluvial erosion modified volcanic depressions the circular rim of which is derived from the original rim are termed erosion craters or erosion calderas depending on the pre existing depression the resulting landform should be classed as an erosion induced volcanic depression if the degradation of a cluster of craters produces a single drained irregular shaped basin or if flank erosion results in a quasi closed depression under humid climates craters and calderas degrade at a faster rate mostly at subtropical and tropical ocean island and island arc volcanoes their erosion results in so called amphitheater valleys that develop under heavy rainfall 2500 mm year rainstorms and high elevation differences structural and lithological control and groundwater in ocean islands may in turn preform and guide development of high energy valleys through rockfalls landsliding mudflows and mass wasting given the intense erosion amphitheater valleys are able to breach a primary depression from several directions and degrade the summit region at a high rate occasionally amphitheater valleys may create summit depressions without a pre existing crater or caldera the resulting negative landforms which may drain in several directions and the primary origin of which is commonly unrecognizable should be included in erosion transformed volcanic depressions

land subsidence in china land subsidence in china occurs in different regions it is primarily caused by excessive groundwater withdrawal other reasons for the subsidence include the oil warm groundwater withdrawal and the neotectonic movement the common characteristics of land subsidence in china are slow accumulative irreversible and other unique properties the range of subsidence still keeps extending and the accumulative subsidence increasing though some measures taken adjustment of the aquifer exploitation practice is a subsidiary way to control land subsidence but it cannot solve this problem completely in a specfic way of groundwater changing the contribution of a certain soil layer to the total subsidence depends on its compressibility and thickness besides the elasticity both cohesive soil layers aquitards and sand layers aquifers are observed to be plastic and creep when the groundwater level fluctuates in a specific way which often leads to subsidence delay

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

numerical assessment of asr recharge using small diameter wells and surface basins summary aquifer storage and recovery asr methods are increasingly used to overcome the temporal imbalance between water demand and availability common asr recharge methods utilize large diameter injection wells or surface infiltration basins and trenches and can be costly to implement a new low cost asr recharge method is currently being developed this approach is based on recharge via gravity in small diameter wells installed with direct push dp technology numerical modeling is used here to assess the potential of this new approach under conditions commonly faced in field settings the primary objective is to investigate if a battery of small diameter dp wells can serve as a viable alternative to a surface basin under typical field conditions while the secondary objective is to assess which subsurface parameters have the greatest control on dp well performance simulation results indicate that gravity recharge via small diameter wells appears to have a distinct advantage over recharge via surface infiltration basins for example two 0 05 m shallow vadose zone wells with 9 m screens can recharge water at a greater rate than a 60 m 2 basin also results reveal that contrary to an infiltration basin the recharge rate in a dp well has a much stronger dependence on the horizontal component of hydraulic conductivity than on the vertical component moreover near surface layers of low hydraulic conductivity which can significantly reduce the recharge capacity of a surface basin have a relatively small impact on the recharge capacity of a well as long as a significant portion of the well screen is installed below those layers given that installation and operation costs can be low in comparison to common asr recharge methods this new approach appears to have great potential for recharging good quality water in shallow unconsolidated aquifers a field investigation has recently been initiated to follow up the findings of this simulation assessment

aquifer recharge using a partially penetrating well with clogging induced permeability reduction abstract well and aquifer clogging is one of the most serious problems restricting the application of managed aquifer recharge mar to address the clogging issue this study proposes an innovative model using partially penetrating wells ppw in confined aquifers while considering the clogging related permeability as an exponentially decayed function of time based on analysis of in situ observation data a combination of hankel transform and finite fourier cosine transform is adopted to solve the model the quasi solutions at early and late times and steady state are also derived using the developed analytical solution the developed solutions can be used to investigate the independent or combined effect of clogging induced permeability reduction well configuration and aquifer anisotropy on groundwater flow dynamics in confined aquifers or inversely used for estimating parameters associated with the clogging effect and aquifer property based on a semi log graphic approach the findings of this study can help for better understanding of the flow behaviors in the confined aquifers suffering clogging and find application in the estimation and prediction of well and aquifer clogging in mar using aquifer injection wells