characterization of land subsidence induced by groundwater withdrawals in su xi chang area china su xi chang area is one of the typical regions in china which suffers from severe land subsidence various tools of field monitoring were integrated to study the characteristics and mechanisms of land subsidence in this region the occurrence and the development of the land subsidence in this region are strongly related to the groundwater pumping both in time and space the main consolidation layers are the soft mud layers however the compressibility of the confined sandy layers should not be ignored the second and third confined aquifers contributed more than 30 of total subsidence meanwhile irrecoverable deformations were also observed in the sandy layers different sandy layers deform diversely under different stress conditions some have the elastic feature but the soil strata including both sandy layers and clayey layers located in the center of the groundwater level depression cone exhibited obvious viscous mechanical behavior which caused the common lag phenomenon the sand composition mingled with small clay particles or interbeds and sand rheology are the two main reasons for the lag phenomena in sandy layers a series of laboratory tests for modeling the effective stress changes due to groundwater withdrawals were conducted to investigate the mechanism of the lag phenomenon based on the test results the relationship of stress strain time for saturated sands is obtained and it could be expressed as power functions the results also showed that the compression of the sandy layers was time dependent and its deformation could be remarkable when establishing land subsidence model the deformation for the similar soil formation could be elastic visco elastic and even visco elastic plastic because of the different groundwater level fluctuation experienced

regional land subsidence simulation in su xi chang area and shanghai city china su xi chang area and shanghai city located in the south of yangtze delta china has subsided due to groundwater overpumping because of the regional scale of the groundwater exploitation cone of depression and land subsidence at present su xi chang area and shanghai city are treated as a single area for land subsidence study to avoid the uncertainty of boundary condition due to the regionalism the characteristics of aquifer system compaction are complex because of the difference in the types compositions and structures of the soils that the hydrostratigraphic units are composed of and in the histories of groundwater level change the hydrostratigraphic units have experienced considering the fact that different hydrostratigraphic units have different kinds of deformation and that an identical unit may also present different deformation characteristics such as elasticity elasto plasticity and visco elasto plasticity at different sites of the cone of depression or in different periods corresponding constitutive laws have been adopted this avoids the shortcomings of the previous research that the same constitutive law was adopted in all the hydrostratigraphic units during the entire time period a coupled flow and subsidence model which includes a three dimensional flow model with variable coefficients and a one dimensional vertical subsidence model is built according to the complicated hydrological condition in the region the simulation model is calibrated using observed data which include compression of individual strata from groups of extensometers and groundwater levels from observation wells from 1995 to 2002 the model reproduced that the primary subsidence layer in shanghai shifts from the shallow aquitard to the fourth confined aquifer because of the groundwater yield variations and the change of exploitation aquifers however the third aquitard was the primary subsidence layer in su xi chang area and the compaction deformation of the sandy aquifers was remarkable the simulation results could provide some reasonable advice about groundwater exploitation in the future

numerical evaluation of land subsidence induced by groundwater pumping in shanghai to predict the future behavior of land subsidence in shanghai due to pumping of groundwater a numerical model is established in the proposed model groundwater flow in three dimensional conditions and soil deformation in one dimen sional conditions are calculated the model takes into account the multi aquifer aquitard hydrogeological condition of the soft deposit of shanghai the variation of the coefficient of compressibility and coefficient of hydraulic conductivity of the soils with the consolidation process are simulated relationships among land subsidence groundwater withdrawal volume and groundwater level are analyzed comparison between the measured value and calculated value shows that the model simulates the measured value fairly well the future of land subsidence behavior due to groundwater withdrawal is predicted and discussed via consideration of the variation of the following parameters in the future 30 years net withdrawn volume of groundwater pumping layer and pumping region resume un modele numerique est propose afin de predire le comportement futur d un affaissement de sol cause par le pompage de l eau souterraine a shanghai dans le modele propose l ecoulement de l eau souterraine en trois dimensions et la deformation du sol en une dimension sont calcules le modele considere la condition hydrogeologique multi aquifere aquitard du depot mou de shanghai les variations du coefficient de compressibilite et du coefficient de conductivite hy draulique des sols lors du processus de consolidation sont simulees les relations entre l affaissement du sol le volume de retrait de l eau souterraine et le niveau phreatique sont analysees des comparaisons entre les valeurs mesurees et calculees montrent que le modele peut simuler les valeurs mesurees relativement bien le comportement futur du sol en affaissement cause par le retrait de l eau souterraine est predit et discute en considerant les variations pour les prochains 30 ans pour les parametres suivants le volume net d eau souterraine retire la couche de pompage et la region de pompage mots cles pompage de l eau souterraine affaissement du sol ecoulement de l eau souterraine en trois dimensions consoli dation en une dimension prediction traduit par la redaction

ground subsidence in semarang indonesia investigated by alos palsar satellite sar interferometry abstract the focus of this study is investigation of land subsidence in semarang city indonesia with the use of interferometry synthetic aperture radar insar of alos palsar satellite we processed 22 ascending sar images during january 2007 to january 2009 plus two descending sar images acquired on 6 june 2006 and 17 june 2007 the time series analysis of interferometry was performed by using 12 pairs of interferogram relative to 21 january 2007 and 8 pairs of interferogram relative 24 january 2008 the topographic phase contribution was removed using the 3 arcsec 90 m shuttle radar topography mission srtm digital elevation model dem we performed precision baseline estimation to vanish the fringes from baseline effect between master and slave data in order to investigate the contribution of horizontal movement in our analysis we constructed two interferograms of ascending orbit and descending orbit the time series results exhibited that the area is subsiding continuously without a significant seasonal effect during january 2007 to january 2009 the land subsidence observed from insar data is approximately up to 8 cm year three cross sections on image displacement show the extreme land subsidence occurred especially along the coastal area and lowland area where this area is considered as industrial with high density settlements consuming a lot of groundwater and land is changed from agriculture and cultivation purposes to industrial estates and house our result also shows a consistency with historical pattern of subsidence measured by leveling data the results highlight the potential use of insar measurements to provide better constraints for land subsidence in semarang city indonesia

mercury intrusion and permeability of louiseville clay several theories have been proposed to correlate the permeability hydraulic conductivity with the pore size distribution of soils and it seemed interesting to determine if these theories could be applied to natural clays for this purpose permeability and mercury intrusion porosimetry tests were performed on a champlain sea clay for both intact and remoulded conditions after compression of the specimens to strains varying from 0 to 42 the results show that for either intact or remoulded soil conditions there is a relationship between the pore size parameters and the permeability of the clay however there is no unique relationship for both intact and remoulded clays and for the silt and clay considered in previous studies consequently mercury intrusion porosimetry alone cannot be usepto evaluate the permeability of soils in general plusieurs thkories ont ctc proposces pour corrcler la permiabilite conductivitk hydraulique avec la distribution des grosseurs de pore des sols et il a semblc intiressant de verifier si ces theories pourraient 2tre appliquees aux argiles naturelles a cette fin des essais de permcabilitc et de porosimctrie a intrusion de mercure okt ctc rcaliscs sur l argile de la mer champlain dans des conditions tant intactes que remanikes apris la compression des specimens a des dcformations variant de 0 a 42 les rcsultats demontrent que pour des conditions soit intactes ou remanices il existe une relation entre les paramitres de grosseur de pore et la permcabilitc de l argile cependant il n existe pas de relation unique pour les argiles tant intactes que remanices et pour le limon et l argile ctudics antkrieurement en conscquence la porosimctrie a intrusion de mercure ne peut pas a elle seule tre utilisce pour cvaluer la permcabilitc des sols en general mots clds permcabilitc argile porosimctrie a intrusion de mercure structure traduit par la rcdaction

successful implementations of a real time and intelligent early warning system for loess landslides on the heifangtai terrace china abstract real time monitoring and intelligent early warning system are crucial and significant to take mitigation measures and reduce casualties and property losses related to landslides it is difficult to obtain entire monitoring data in the accelerated deformation phase in a landslide event and hard to issue early warning information using a traditional monitoring approach with fixed and low sampling frequency displacement increments of loess landslides induced by agriculture irrigation on the heifangtai terrace could be sudden and extremely rapid typical landslide types include loess flowslides and loess falls it is of practical significance to develop a self adaptive data acquisition monitoring technique and establish a real time landslide early warning system lews to meet the needs for risk mitigation of rapid sliding slopes on the heifangtai terrace the monitoring technique can wirelessly transmit displacement data and the lews was devised using the new artificial intelligence the lews could automatically release the warning information in advance of the event once the early warning parameters exceed default thresholds in this study the early warning procedures real time monitoring approach intelligent lews a multiple criteria warning model warning release and emergency mitigation measures and performance are introduced in detail six loess landslides at heifangtai and eight landslides in other regions of china have been successfully warned since its implementation in 2012 this study proposed an effective and practical solution for the early warning of loess landslides at heifangtai two typical loess landslides that had successful early warnings at heifangtai were presented the successful implementation could serve as a reference for global rapid slope failure cases considering the complex nature of landslide behaviors and failure mechanisms

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

investigation of land subsidence with the combination of distributed fiber optic sensing techniques and microstructure analysis of soils abstract land subsidence is a global phenomenon caused by a variety of factors and there are still many challenges in land subsidence monitoring the results of an investigation of land subsidence using the combination of distributed fiber optic sensing dfos techniques and microstructure analysis of soil are here presented two dfos techniques brillouin optical time domain reflectometry botdr and fiber bragg grating fbg were developed in two boreholes namely gm03 and sz01 in su xi chang area china to monitor movement of strata crossed by the borehole and pore pressure in some specific strata scanning electron microscope sem and mercury intrusion porosimetry mip were employed to quantify and characterize the microstructures of undisturbed soils from the boreholes based on the botdr monitoring results the annual levels of land subsidence in gm03 and sz01 are 1 2 mm and 2 9 mm respectively and the movement history of strata were clearly tracked for both boreholes the main contributors to subsidence are two aquitards ad2 and ad3 that exist adjacent to the second aquifer af2 the results obtained by fbg based sensors indicate good agreement with botdr and it confirms that the deformation of aquifer is significantly controlled by pore pressure sem images were analyzed with pore particle and crack analysis system pcas three statistical parameters including average form factor ffavg fractal dimension df and area probability distribution index b were used to describe the geometric characteristics of pores it is found that larger average form factor larger fractal dimension and higher proportion of large pores in soil microstructures favors land subsidence mip results confirm that area probability distribution index can be used for the estimation of strata compression potential in land subsidence investigations

greenland ice sheet mass balance reconstruction part i net snow accumulation 1600 2009 ice core data are combined with regional atmospheric climate model version 2 racmo2 output 1958 2010 to develop a reconstruction of greenland ice sheet net snow accumulation rate at g spanning the years 1600 2009 regression parameters from regional climate model rcm output regressed on 86 ice cores are used with available cores in a given year resulting in the reconstructed values each core site s residual variance is used to inversely weight the cores respective contributions the interannual amplitude of the reconstructed accumulation rate is damped by the regressions and is thus calibrated to match that of the rcm data uncertainty and significance of changes is measured using statistical models a 12 or 86 gt yr 21 increase in ice sheet accumulation rate is found from the end of the little ice age in 1840 to the last decade of the reconstruction this 1840 1996 trend is 30 higher than that of 1600 2009 suggesting an accelerating accumulation rate the correlation of at g with the average surface air temperature in the northern hemisphere satnht remains positive through time while the correlation of at g with local near surface air temperatures or north atlantic sea surface temperatures is inconsistent suggestinga hemispheric scale climateconnection an annualsensitivityof at g to satnhtof 6 8 k 21 or 51 gt k 21 is found the reconstuction at g correlates consistently highly with the north atlantic oscillation index however at the 11 yr time scale the sign of this correlation flips four times in the 1870 2005 period

multiscale organization of convection simulated with explicit cloud processes on an aquaplanet abstract this study investigated the multiscale organization of tropical convection on an aquaplanet in a model experiment with a horizontal mesh size of 3 5 km for a 10 day simulation and 7 km for a 40 day simulation the numerical experiment used the nonhydrostatic icosahedral atmospheric model nicam with explicit cloud physics the simulation realistically reproduced multiscale cloud systems eastward propagating super cloud clusters sccs contained westward propagating cloud clusters ccs sccs ccs had zonal sizes of several thousand hundred kilometers typical propagation speed was 17 10 m s 1 smaller convective structures such as mesoscale cloud systems mcs of o 10 km and cloud scale elements 16 km of o 100 km area was also reproduced planetary scale equatorial waves with wavelengths of 10 000 and 40 000 km had a major influence on the eastward propagation of the simulated scc destabilization east of the

characterisation and engineering properties of tiller clay abstract a detailed characterisation of the quick clay underlying the ntnu research site at tiller trondheim is presented the objective of the work is to provide guidance on quick clay parameters to engineers and researchers working with similar clays in scandinavia and north america especially on landslide hazard assessment the material is lightly overconsolidated and is characterised by its high degree of structure and very high sensitivity quick clay clay and water contents are both about 40 the plasticity index is low 5 this relates to the low active minerals of the clay and silt fractions illite chlorite and quartz feldspars respectively undrained shear strength is of the order of 30 kpa to 50 kpa medium stiff and increases with depth the deposit is consistent across the site and its properties are similar to other norwegian quick clays significant efforts have been made into examining sample disturbance effects on the material it was found that thin walled steel fixed piston samples can yield results similar to those of block samples provided the work is carried out with extreme care and storage time is minimised the piezocone cptu test proved very useful in characterising the material

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

a century of land subsidence in ravenna italy over the last century the ravenna area has been affected by a widespread land subsidence process of both natural and anthropogenic origin which has become a matter of increasingly great concern land settlement initially of the order of a few mm year dramatically increased up to 110 mm year after world war ii primarily due to groundwater pumping and subordinately gas production from a number of deep on shore and off shore reservoirs spirit leveling was carried out in the area of the ravenna municipality by various authorities and agencies ever since the end of the nineteenth century using an increasingly refined network of benchmarks the available information spanning the time interval from 1897 to 2002 has been implemented and homogenized into a geographic information system gis measurements processed by kriging provide the pattern of the subsidence rates over the municipal territory during eight sub periods the reliability of data processing is discussed for both magnitude and areal distribution of the occurrence showing a pronounced nonlinear behavior in time as related to the major responsible factors cumulative land subsidence approaches almost 1 m over more than one third of the municipality area including the city and a significant fraction of the coastland with peaks larger than 1 5 m over a 10 km2 zone located between the historical center and the coastline most recent records show that at present the mainland appears to be substantially stable whereas some coastal areas are still subsiding at a rate of about 10 mm year with a significant threat to the environment and the infrastructures as well although to a lesser extent than in the past decades

mining geohazards susceptibility and risk mapping the case of the amyntaio open pit coal mine west macedonia greece during the last decades numerous methodologies for the construction of both susceptibility and risk maps have been developed in order to identify and mitigate geohazards such as landslides and secondarily land subsidence phenomena caused by the collapse of natural or man made underground cavities according to literature review the conducted research concerning the assessment of land subsidence risk due to the overexploitation of the aquifer is still at an early stage this study focuses n the land subsidence phenomenon due to the overexploitation of the aquifer occurring in the amyntaio basin in west macedonia hosting the active amyntaio open pit coal mine this phenomenon has caused significant damage to settlements farmlands and infrastructure in order to construct susceptibility and risk maps knowledge of the geological geotechnical hydrogeological and tectonic settings of the study area is required the proposed methodology for the production of a susceptibility and a risk map of land subsidence was based on the semi quantitative method weighted linear combination wlc the results were evaluated with an extensive field survey action recording besides the above mentioned settings the spatial distribution of surface ruptures the excellent agreement between the produced maps and the findings of the field survey proved the added value of the maps assigning them as crucial tools for the management of land subsidence phenomena

depositional and post depositional geochemistry and its correlation with the geotechnical properties of marine clays in ariake bay japan the mineralogy geochemistry and geotechnical properties of clay samples in ariake bay japan are presented the mineralogy and geochemistry are discussed in terms of depositional and post depositional processes and the correlations of the clay mineralogy and geochemistry with the geotechnical properties were examined by multiple regression analysis the most predominant clay mineral in the deposits was found to be smectite the vertical distribution of trace elements in the deposits was indicative of the periodical changes in the parent materials involved in the depositional processes the chloride concentration in the pore water varied according to a change in the sea level from brackish to marine and then brackish towards the surface the higher iron oxide contents near the surface and in the deepest zones were the results of pyrite oxidation in the deposits due to weathering under subaerial conditions smectite content was the most predominant governing factor for the consistency limits and activi

large scale organization of tropical convection in two dimensional explicit numerical simulations the large scale organization of tropical deep convection is investigated in idealized two dimensional cloud resolving simulations a 20 000 km periodic computational domain allows interactions among moist convection mesoscale organization and surface exchange on a wide range of scales a uniform 10 m s 1 easterly wind and a uniform sea surface temperature of 30 c are assumed a prescribed temperature tendency mimicking the mean radiative cooling of the tropical troposphere is used in this pilot study the large scale organization of convection resembles the observed tropical atmosphere as well as results from some previous numerical studies using parametrized convection the simulation highlights mesoscale convective systems with horizontal scales of several hundred kilometres moving east to west with speeds similar to the mean flow and an envelope of convection with a horizontal extent of a few thousand kilometres and propagating west to east the propagation speed of the large scale envelope compares well with the phase velocitites of convectively coupled kelvin waves observed in the equatorial waveguide convective momentum transport and the impact of convective systems on temperature and moisture near the surface are key processes responsible for the large scale organization of convection these results are discussed in the context of recent observations and numerical studies of convection organization in the tropics

evolution of microstructure in compacted london clay during wetting and loading the influence of fabric on mechanical behaviour is explicitly considered in some of the current constitutive models for unsaturated soils these are based on assumptions regarding the interaction b

geomechanics of subsurface water withdrawal and injection land subsidence and uplift ground ruptures and induced seismicity are the principal geomechanic effects of groundwater withdrawal and injection the major environmental consequence of groundwater pumping is anthropogenic land subsidence the first observation concerning land settlement linked to subsurface processes was made in 1926 by the american geologists pratt and johnson who wrote that the cause of subsidence is to be found in the extensive extraction of fluid from beneath the affected area since then impressive progress has been made in terms of a recognizing the basic hydrologic and geomechanic principles underlying the occurrence b measuring aquifer compaction and ground displacements both vertical and horizontal c modeling and predicting the past and future event and d mitigating environmental impact through aquifer recharge and or surface water injection the first milestone in the theory of pumped aquifer consolidation was reached in 1923 by terzaghi who introduced the principle of effective intergranular stress in the early 1970s the emerging computer technology facilitated development of the first mathematical model of the subsidence of venice made by gambolati and freeze since then the comprehension measuring and simulation of the occurrence have improved dramatically more challenging today are the issues of ground ruptures and induced triggered seismicity which call for a shift from the classical continuum approach to discontinuous mechanics although well known for decades anthropogenic land subsidence is still threatening large urban centers and deltaic areas worldwide such as bangkok jakarta and mexico city at rates in the order of 10 cm yr

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

influence of holocene stratigraphic architecture on ground surface settlements a case study from the city of pisa tuscany italy abstract the holocene stratigraphic architecture of modern coastal and deltaic plains has peculiar characteristics that may influence ground surface settlements in the pisa urban area the inhomogeneous spatial distribution of geotechnically weak layers typically formed during the mid late holocene highstand coastal progradation is inferred to be responsible for urban ground settlement and building damage as evidenced by the tilt of several surface structures among which the famous leaning tower of pisa is the most prominent on the basis of integrated stratigraphic sedimentological and geotechnical data from a wide georeferenced database three facies associations with high deformability potential units 1 3 are identified in the uppermost 30 m as opposed to depositional facies units 4 5 with higher geotechnical strength whereas unit 1 represents a thick laterally extensive lagoonal clay deposit the overlying highly deformable units units 2 3 show more discontinuous spatial distribution controlled by the holocene paleohydrographic evolution of the arno coastal plain unit 2 dated between the neolithic and the etruscan age ca 5000 2000 yr bp is composed of swamp clays and silty clays recording lagoon infilling due to arno delta progradation units 3 and 4 which consist of wet levee deposits and stiff floodplain clays respectively formed during the subsequent phases of alluvial plain construction started around the roman age from ca 2000 yr bp whereas units 3 and 4 are recorded within the uppermost 5 m fluvial and distributary channel sands unit 5 cut the underlying deltaic alluvial succession at various stratigraphic levels down to unit 1 the spatial distribution of these units gives rise to three locally juxtaposed stratigraphic motifs in pisa underground reflecting different potential risks for settlement under building loads we show how lateral changes in stratigraphic architecture account for the irregular spatial distribution of geotechnically weak layers that are responsible for building damage and ground settlement

squall lines and convectively coupled gravity waves in the tropics why do most cloud systems propagate westward abstractthe coupling between tropical convection and zonally propagating gravity waves is assessed through fourier analysis of high resolution 3 hourly 0 5 satellite rainfall data results show the familiar enhancement in power along the dispersion curves of equatorially trapped inertia gravity waves with implied equivalent depths in the range 15 40 m i e pure gravity wave speeds in the range 12 20 m s 1 here such wave signals are seen to extend all the way down to zonal wavelengths of around 500 km and periods of around 8 h suggesting that convection wave coupling may be important even in the context of mesoscale squall lines this idea is supported by an objective wave tracking algorithm which shows that many previously studied squall lines in addition to 2 day waves can be classified as convectively coupled inertia gravity waves with the dispersion properties of shallow water gravity waves most of these disturbances propagate westward at speeds faster than the background flow to under

dependence of antarctic surface mass balance on temperature elevation and distance to open ocean the latest compilations of surface mass balance mean annual surface temperature and elevation for the antarctic ice sheet derived from data sets of approximately 1500 700 and 105 points respectively have been used to obtain areally integrated means for 24 ice drainage systems and 329 grid point values covering the whole ice sheet monthly summaries of remotely sensed sea ice data for 1973 1976 have been used to obtain mean annual distance to open ocean linear and second order regression analyses of surface balance on 1 temperature for the entire ice sheet 2 elevation for the conterminous grounded ice and 3 distance to the open ocean for the ice shelves including ice rises and attached islands have been made using both system means and grid point values these analyses show correlation coefficients of between 0 63 and 0 81 and they provide bases for descriptive models of the present antarctic ice sheet as well as for predictive models of the response of the ice sheet to air temperature changes and variations in meridional mass and energy transfers extrapolation to other ice sheets past and present may be possible but should be made cautiously linear models are recommended for paleoclimatic reconstructions of ice sheets in upper mid latitudes and second order models are recommended for those in high latitudes system means are shown to be reliable for these purposes incidental results are new estimates of the mean annual surface temperature for the whole ice sheet 36 c and mean surface elevation for the conterminous grounded ice 2290 m

pore structure characteristics of debris flow source material in the wenchuan earthquake area abstract wide grading loose soils wgls are a special slope deposit that often serve as a source for debris flows in the western mountainous area of china previous research indicated that rainfall infiltration induced the migration of fine particles within soil slopes and lead to the initiation of shallow failure and subsequent debris flows clearly soil pore structure exerts a profound influence on seepage during rainfall infiltration which is closely related to soil permeability and corresponding internal erosion the current understanding of the mechanisms of fine particle migration is limited because of the complexity of wgls micropore structure the challenge lies in how to systematically characterize wgls pore structure so that it provides a foundation for future numerical simulations of fine particle migration induced debris flows in this study the characteristics of wgls pore structure were analyzed quantitatively using scanning electron microscopy the results revealed that wgls predominantly contained micropores and mesopores the pore size distribution exhibited a bimodal nature with one peak occurring at a pore diameter of 12 m and another at 72 m the pore complexity of all samples exceeded 0 75 which indicates a low aspect ratio for each pore the average diameter of the fine particles that migrated was then determined with a laboratory seepage test a preliminary jamming probability analysis based on three dimensional micropore reconstruction and average fine particle diameter indicate that jamming is most prevalent along the slope

groundwater derived land subsidence in the north china plain land subsidence usually bears strong relationship to abstraction of underground fluid land subsidence occurs commonly in the north china plain ncp and has become a major environmental factor hindering regional sustainable development this paper focuses on issues associated with mechanism of land subsidence in the ncp the analysis shows that multi layer aquifer systems with deep confined aquifers and the thick normally consolidated or unconsolidated compressible clay layers are the key of geological and hydrogeological conditions favorable for the development of land subsidence in the ncp groundwater withdrawal results in an increase in the distribution of effective stress within the strata and the compression of the aquifers and the confining layers and then triggers land subsidence in the middle east plain of the ncp the land subsidence volume approximately represents the amount of water released from compression of deep aquifers and aquitards in that land subsidence is primarily caused by excessive groundwater withdrawal in deep aquifer system the percentage of water released from compression of aquifers and aquitards in deep groundwater abstraction is significant but distinct in cangzhou city and in the whole middle east plain this is due to the difference in local lithological structure and recharge and discharge conditions of deep groundwater system the hysteresis of land subsidence is also discussed in typical areas and the results reveal that the time for completing the primary consolidation ranges from less than one year to tens of years and that the rate of secondary compression tends to increase with the moisture content

long term land subsidence and strata compression in changzhou china abstract changzhou city underlain by a multi layered aquifer system in quaternary sediments in the great yangtze river delta region experienced a maximum land subsidence rate of 147 mm year in the early 1980s due to excessive groundwater extraction a large scale monitoring station of 11 borehole extensometers was established in the city in 1983 to investigate land subsidence nine strata were predetermined in the quaternary depth interval and monitored by borehole extensometers presented in this paper are the long term observations of land subsidence strata compression and groundwater level in four aquifers from 1984 to 2002 and discussion on strata compression based on the measured data with reference to the stratigraphy soil properties groundwater withdrawn and literature of similar situations the compression of strata varies significantly and is strongly influenced by groundwater drawdown in the second confined aquifer or ca2 the groundwater level in ca2 declined from 55 m in 1981 to 76 m in 1994 and the land subsidence rate remained high after the city government enforced restrictions on groundwater extraction in 1995 the extraction rate sharply reduced the groundwater level in ca2 steadily recovered to 56 m until 2003 and the land subsidence rate declined to 10 mm year in 2002 from 1984 to 2002 the land subsidence was mainly attributed to the consolidation of the thick aquitard overlying ca2 in the future to prevent the subsidence rate from rising it is vital to stop groundwater drawdown in aquifers

excessive groundwater withdrawal and resultant land subsidence in the su xi chang area china excessive groundwater withdrawal has caused severe land subsidence in the su xi chang sxc area china the restriction and prohibition on groundwater pumping have been carried out since the late 1990s based on the latest updated field data the changing pattern of groundwater level and the distribution of land subsidence are analyzed the distribution of land subsidence in sxc is closely related to that of the cone of depression in the second confined aquifer in time and space but land subsidence is not in synchronization with the changing groundwater level both aquitards and aquifers compacted continuously in the early period of groundwater level rising and behaved as creep materials a series of laboratory tests were conducted on aquifer sands which indicated that the creep deformation under virgin compression is much greater than that under recompression and unloading and that the creep of sands decreases rapidly with the cycles of repeating load the test results reveal the mechanism of sand creep under the condition of long term groundwater pumpage as a consequence of the restriction and prohibition on groundwater pumping groundwater level has obviously recovered in the vast majority of the sxc area and land subsidence has slowed down and even a little rebound has occurred in some sites in suzhou and changzhou if the pumpage is strictly limited continuously the groundwater level will not decline below the historical lowest value but fluctuate within a certain range in such a case land subsidence in sxc will no longer develop obviously

hydro geotechnical modelling of subsidence in the como urban area abstract the urban area of como italy is particularly susceptible to subsidence the reason is the particular structure of the subsoil combined with the anthropic modification of the lakeshore lands linked to the historical evolution of the area moreover this phenomenon exposes the lakefront areas to an increasing risk of flooding the primary purpose of this study was to develop an effective methodology for the assessment of subsidence in urban areas to be used as a support in groundwater management the development of a coupled hydrogeological geotechnical numerical model for the period 2004 2011 allowed recognizing the shoreline results as most susceptible areas to the phenomenon model results were critically evaluated through comparison with time series of psinsar and high precision levelling data available in the area the anthropic perturbations of groundwater flow linked to the construction of lake flooding defenses in 2008 2009 enhanced the subsidence phenomenon in a localized area pointing out the strong inter dependence of groundwater circulation lake level oscillations and geotechnical behavior of soils thus the model revealed the most critical zones and geotechnical units demonstrating to be a potential powerful tool to predict subsidence scenarios e g the future completion of the floods defense works in the shoreline area

multiscale convective wave disturbances in the tropics insights from a two dimensional cloud resolving model abstract multiscale convective wave disturbances with structures broadly resembling observed tropical waves are found to emerge spontaneously in a nonrotating two dimensional cloud model forced by uniform cooling to articulate the dynamics of these waves model outputs are objectively analyzed in a discrete truncated space consisting of three cloud types shallow convective deep convective and stratiform and three dynamical vertical wavelength bands model experiments confirm that diabatic processes in deep convective and stratiform regions are essential to the formation of multiscale convective wave patterns specifically upper level heating together with low level cooling serves to preferentially excite discrete horizontally propagating wave packets with roughly a full wavelength structure in troposphere and dry phase speeds cn in the range 16 18 m s 1 these wave packets enhance the triggering of new deep convective cloud systems via low level destabilization the new convection in turn caus

effects of convectively generated gravity waves and rotation on the organization of convection abstract the effects of latent heating gravity waves and planetary rotation on numerically simulated convective cloud systems are investigated first the nonlinear response of an initially motionless uniformly stratified dry atmosphere to steady heating that interacts with the environment through inertial gravity waves is examined planetary rotation confines the subsidence induced adiabatic warming to the neighborhood of the heated region on a time scale comparable to the lifetime of mesoscale convective systems in a moist atmosphere rotation induced localized descent stabilizes and dries the near environment and decreases the convective available potential energy the tropics is therefore a preferred region for convective clustering this hypothesis is tested in two sets of multiday convection resolving simulations on f planes representative of the tropics subtropics and midlatitudes convection is maintained by radiative cooling and surface fluxes of heat and moisture in a motionless mean sta

study of the structure of a sensitive champlain clay and of its evolution during consolidation scanning electron microscopy and mercury intrusion porosimetry are used in parallel to identify the structure of a medium sensitivity champlain clay the clay structure is observed firstly on intact remolded and oven dried soils and secondly on soils consolidated at various levels in one dimensional compression both methods of investigation reveal for the intact soil the existence of an aggregated structure characterized by an interaggregate and an intra aggregate porosity remolding affects interaggregate links but does not destroy aggregates the observation of clay structure at various levels of one dimensional compression shows that the collapse of the structure is progressive the largest interaggregate pores being the first affected as the consolidation proceeds smaller and smaller pores are affected for a given pressure increment only the largest existing pores are affected a structure anisotropy has been seen to develop with increasing compression the scanning electron microscope and the me

ageing effects in a compacted bentonite a microstructure approach it is suspected that the as compacted state of heavily compacted clays used as possible engineered barriers for nuclear waste disposal is time dependent and that further change may occur in the material even at constant water content and density this paper presents an investigation of the time dependent microstructure changes of an mx80 clay bentonite compacted at various dry densities and water contents microstructure investigation is based on mercury intrusion pore size distribution measurements and scanning electron microscopy sem results obtained by other researchers by using x ray diffraction at low angles are also used statically compacted samples of mx80 were kept at constant volume and water content for various periods of time 1 30 and 90 days prior to mercury intrusion and sem micro structure investigation a significant change in micro structure with time was observed characterised by a decrease in the inter aggregate porosity and an increase in the very thin porosity not intruded by

estimation of atmospheric transmissivity of solar radiation from precipitation in the himalaya and the tibetan plateau though solar radiation is important for glacier mass balance simulation solar radiation data are not always available as a result of analyzing meteorological data measured in the himalaya and the tibetan plateau a favorable correlation between precipitation and atmospheric transmissivity of solar radiation is found in terms of monthly values monthly mean solar radiation is derived from the relationship between atmospheric transmissivity of solar radiation and precipitation with input of monthly precipitation latitude skyline and time the differences between estimated and observed monthly mean solar radiation are 40 w m 2 in most cases however the differences at some sites are significantly large the error in the estimated solar radiation during the monsoon season can be large when the monthly mean precipitation rate is about 5 mm d 1 though the error in the estimated solar radiation during the non monsoon season is generally small due to low precipitation in the himalaya and the tibetan plateau during this season it can exceed 100 w m 2

land subsidence in tianjin china land subsidence has been affecting tianjin for the past 50 years it leads to comprehensive detrimental effects on society the economy and natural environment overpumping of groundwater is the main cause in 2008 the maximum cumulative subsidence reached 3 22 m and the total affected area nearly 8 000 km2 the subsidence reached its most critical state in the early 1980s when it occurred at a rate as high as 110 mm year at the same time groundwater extraction had also reached a maximum of 1 200 million m3 by importing the luan river to tianjin and restricting exploitation of groundwater hydraulic heads gradually recovered after 1986 in all aquifers and this has continued to the present in the second aquifer the subsidence rate in urban areas dropped to 10 15 mm year the area of groundwater extraction expanded to the suburban area with economic growth in the 1990s and it was shifted to the third and fourth aquifers at present with a subsidence rate of 30 40 mm year four new suburban subsidence centers have been formed several measures were adopted to mitigate and prevent land subsidence disasters these included restricting groundwater exploitation groundwater injection prohibiting use in the specific zone a pricing policy for water resources advocating water saving technology and strict enforcement of groundwater laws although the subsidence area is still increasing slowly the subsidence rate is being controlled

vertical mode and cloud decomposition of large scale convectively coupled gravity waves in a two dimensional cloud resolving model this paper describes an analysis of large scale o 1000 km convectively coupled gravity waves simulated using a two dimensional cloud resolving model the waves develop spontaneously under uniform radiative cooling and approximately zero mean flow conditions with wavenumber 2 of the domain appearing most prominently and right moving components dominating over left moving components for random reasons the analysis discretizes the model output in two ways first a vertical mode transform projects profiles of winds temperature and heating onto the vertical modes of the model s base state atmosphere second a cloud partitioning algorithm sorts sufficiently cloudy grid columns into three categories shallow convective deep convective and stratiform anvil results show that much of the tilted structures of the waves can be captured by just two main vertical spectral bands each consisting of a pair of vertical modes the slow modes have propagation speeds of 16 and 18 m s 1 and roughly a full wavelength vertical structure through the troposphere while the fast modes have speeds of 35 and 45 m s 1 and roughly a half wavelength structure deep convection anomalies in the waves are more or less in phase with the low level cold temperature anomalies of the slow modes and in quadrature with those of the fast modes owing to the characteristic life cycle of deep convective cloud systems shallow convective heating peaks 2 h prior to maximum deep convective heating while stratiform heating peaks 3 h after the onset of deep convection in the waves is preceded by a gradual deepening of shallow convection lasting a period of many hours results of this study are in broad agreement with simple two mode models of unstable large scale wave growth under the name stratiform instability differences here are that 1 the key dynamical modes have speeds in the range 16 18 m s 1 rather than 23 25 m s 1 owing to a shallower depth of imposed radiative cooling and 2 deep convective heating as well as stratiform heating is essential for the generation and maintenance of the slow modes

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

the effects of artificial recharge of groundwater on controlling land subsidence and its influence on groundwater quality and aquifer energy storage in shanghai china long term groundwater overpumping in shanghai has caused serious land subsidence to restore the declined piezometric groundwater levels and to decrease the land subsidence rate artificial recharge ar of groundwater into confined aquifers through injected wells has been proposed as an important measurement since the beginning of the 1960s in the case of shanghai recharge source is tap water whose chemical constituents and temperature are different from groundwater consequently the issues of groundwater quality change and thermal energy are worthy of discussion in this paper we discussed the influences of ar for controlling land subsidence on 1 groundwater level and land subsidence rate 2 groundwater quality 3 aquifer thermal energy storage the results based on the collected long term historical data in the study area show that ar not only is beneficial to groundwater level rising and land rebound but also provides cheap energy sources for industrial production the groundwater quality presented the trend of desalination and a general increase in sulfate iron and manganese contents organic and nitrogenous compounds after the tap water injection however the ar s influence on groundwater quality was limited with the radius 100 m for single well recharge and 1000 m for well groups recharge to control the development of the land subsidence within a safe limit in the study area the injected confined aquifers and the distribution of the ar wells need to be further adjusted due to the limitation of current ar

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

land subsidence in bangkok thailand abstract land subsidence from deep well pumping has been affecting bangkok for the past 35 years its impact is particularly critical because of the flat low lying topography and the presence of a thick soft clay layer at the ground surface that augment flood risk and foundation engineering problems respectively the subsidence reached its most critical state in the early 1980s when it occurred at a rate as high as 120 mm year the rate decreased in the subsequent period but the subsidence affected area expanded following the growth of the city despite various attempts implemented to remedy the crisis groundwater pumping from the thick aquifer system underneath the city continued to increase from 1 2 million m3 day in the early 1980s to more than 2 0 million m3 day at the turn of the century piezometric levels in the main aquifer layers had been drawn down by as much as 65 m monitoring data showed a clear correlation between the subsidence and piezometric drawdown the data suggested that for 1 m3 of groundwater pumped out in bangkok plain approximately 0 10 m3 of ground loss occurred at the surface significant development has been made in numerical methods for prediction of differential settlements between building foundations caused by the piezometric drawdown in the aquifers the strict mitigation measures adopted recently comprising a pricing policy for groundwater management an expansion of tap water supply and strict enforcement of groundwater laws have resulted in a marked drop in groundwater use however the land subsidence will continue for a long while owing to the time dependent consolidation behavior of the soft clay layer and clay aquitards

land subsidence due to groundwater withdrawal in the northern beijing plain china abstract beijing is an international metropolis where over exploration of water resource makes land subsidence becoming more and more serious the related problems cannot be avoided in the coming years because of the giant increase of population the aims of this study are to quantify land subsidence over the period 2003 to 2010 grasp the evolution of the process and investigate the relation with the triggering factors in the northern area of the beijing plain various data including deep compaction from vertical multiple borehole extensometers land subsidence from persistent scatterer interferometry and leveling surveys groundwater levels hydrogeological setting from wellbores and landsat tm image were collected and effectively used to detect the spatial and temporal features of land subsidence and its possible relation with groundwater level changes compressible layer thickness and urban development results show that land subsidence is unevenly distributed and continuously increased from 2003 to 2010 the average loss of elevation over the monitoring period amounted to 92 5 mm with rates up to 52 mm y the distribution of the subsidence bowl is only partially consistent with that of the groundwater depression cone because of the variable thickness of the most compressible fine deposits in fact extensometers reveal that silty clay layers account for the larger contribution to land subsidence with the 15 m thick silty clay layer between 102 and 117 m depth accounting for about 25 of the total subsidence finally no clear correlation has been observed between the subsidence rates and the increase of the load on the land surface connected to the impressive urban development this study represents a first step toward the development of a physically based model of the subsidence occurrence to be used for planning remediation strategies in the northern beijing plain

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

insar time series investigation of long term ground displacement at beijing capital international airport china abstract interferometric synthetic aperture radar insar time series analysis provides high spatial resolution and continuous temporal coverage for investigations of long term ground displacement beijing the capital city of china has suffered from land subsidence since the 1950s and extreme groundwater extraction has led to subsidence rates of 100 mm year in this study insar time series analysis is performed on different data subsets to investigate the ground displacement at capital international airport beijing between june 2003 and november 2013 the results show that the ground surface in the airport has deformed at different rates ranging from 66 2 mm year sinking to 8 2 mm year uplift relative to the reference point the projected vertical displacement rates agreed with measurements estimated from ground leveling surveys and the correlation coefficient of the fitting result is 0 96 with a standard deviation of 0 9 mm year and a mean different of 2 0 mm year the runways and terminals have been affected by land subsidence to various degrees previous studies has indicated that long term intense groundwater extraction is the main reason leading to land subsidence in this area other triggering factors such as active faults the quaternary compressible layers and urbanization also have different degrees of contribution or impact on land subsidence in beijing plain furthermore some interesting behaviors from groundwater such as inter and semi annual variations and subsidence the relationship between them are also found in this study

multi temporal insar evidence of ground subsidence induced by groundwater withdrawal the montellano aquifer sw spain this study uses the insar technique to analyse ground subsidence due to intensive exploitation of an aquifer for agricultural and urban purposes in the montellano town sw spain the detailed deformation maps clearly show that the spatial and temporal extent of subsidence is controlled by piezometric level fluctuations and the thickness of compressible sediments the total vertical displacement measured with multi temporal insar between 1992 and 2010 is 33 mm that corresponds with a decrease of 43 m in the groundwater level this technique allows monitoring the evolution of settlement related to water level fall in an area where subsidence has not yet been reported by population or authorities through infrastructure damages and to discuss the effect of the aquifer recovery this information is therefore valuable for implementing effective groundwater management schemes and land use planning and to propose new building regulations in the most affected areas

a probabilistic approach to soil layer and bedrock level modeling for risk assessment of groundwater drawdown induced land subsidence sub surface construction in urban areas generally involves drainage of groundwater which can induce subsidence in soil deposits knowledge of where compressible sediments are located and how thick these are is essential for estimating subsidence risk a probabilistic method for coupled bedrock level and soil layer modeling to detect compressible sediments is presented the method is applied in an area in central stockholm where clay is the compressible sediment layer first a bedrock level model was constructed from three sources of information a geotechnical drillings reaching the bedrock b drillings not reaching the bedrock and c mapped bedrock outcrops input data for the probabilistic bedrock level model was generated by a stepwise kriging procedure second a three layer soil model was constructed including the following materials a coarse grained post glacial and filling material below the ground surface b glacial and post glacial clays and c coarse grained glaciofluvial and glacial till deposits above the bedrock layer thicknesses were transformed to proportions of the total soil thickness since kriging requires data to be normally distributed the proportions were transformed from proportions p to standard normal quantiles z in each iteration of a monte carlo simulation a spatial distribution of the bedrock level was simulated together with the transformed values for the soil layer proportions from the iterations the probability density of the clay thickness compressible sediments at each grid cell was calculated the results of the case study map the expected value mean and the 95th percentile of the probability of compressible sediments at specific locations the resulting model is geologically realistic and validated through a cross validation procedure in order to be in good agreement with a reference dataset the case study showed that the method can efficiently handle large amounts of data and requires little manual adjustment moreover the mapped results can provide useful decision support when planning risk reducing measures and when communicating with stakeholders although this novel method is developed for risk assessment of groundwater drawdown induced subsidence it is useful for other applications involving spatial soil strata modeling

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

identifying poromechanism and spatially varying parameters of aquifer compaction in choushui river alluvial fan taiwan abstract subsidence occurs in many alluvial depositional environments causing substantial socio economic losses thick aquifers with interbedding or lens structured clay can contribute significantly to compaction the poromechanism of aquifer compaction is usually complicated and its spatial variation is poorly understood inhibiting our ability to fully explain the region wide nature of groundwater exploitation induced land subsidence in this study we explore the poromechanism of aquifer deformation in the choushui river alluvial fan taiwan groundwater level and multi layer compaction data were collected for analyses elastic plastic and viscous characteristics all appear in the deformation data to various extents a visco elasto plastic vep model composed of a visco elastic set and a visco plastic set in series which are associated with different viscous dampers is proposed to model the deformation compared with existing models the proposed model is superior in terms of simulating compaction as well as its applicability and versatility the proposed vep model is applied to observation wells in the proximal middle and distal fans of the choushui river alluvial fan to explore the spatial variation in the poromechanical properties the results show that the young s modulus of the elastic spring increases with depth and with the distance from the distal fan to the proximal fan the young s modulus of the plastic element decreases with depth the system response factor of the visco plastic set decreases with depth and with the distance from the distal fan to the proximal fan aquifer recovery incapability increases with depth both the trend and dynamic fluctuations in compaction for the choushui river alluvial fan are well captured by the proposed vep model which is essential for assessing long term land and water resource management and evaluating potential short term threats to infrastructure caused by seasonal subsidence

analysis of long term land subsidence near mexico city field investigations and predictive modeling the mexico city region has several flat plains formed on exceptionally porous 60 90 lacustrine deposits overlying a highly productive regional aquifer severe land subsidence due to consolidation of the lacustrine aquitard caused by aquifer exploitation has resulted in restrictions on pumping in the core of mexico city this has led to large increases in aquifer pumping in the outlying lacustrine plains where satellite communities are rapidly expanding the chalco basin is one of these lacustrine areas where pumping began in the 1950s and greatly increased in the 1980s the lacustrine sequence in the chalco area is significantly thicker than anywhere else in the basin of mexico averaging 100 m and reaching a maximum thickness of 300 m consequently this area is susceptible to the highest potential land subsidence effects as a result of groundwater extraction of anywhere in the basin land subsidence in the central part of the chalco basin has increased to 0 4 m yr since 1984 and by 1991 total subsidence had reached 8 m the rapid land subsidence in this area is causing the accumulation of meteoric waters during the rainy season resulting in extensive flooding of farmland this study first demonstrates a methodology for combining hydraulic data from a network of monitoring wells geotechnical data from core samples and a compilation of historical information on land surface elevation to quantify groundwater flow and land subsidence phenomena within the rapidly subsiding chalco basin then a one dimensional mathematical model is employed to develop predictions of future land subsidence under a range of pumping conditions the model permits the hydraulic properties of the aquitard to vary as transient functions of hydraulic head and porosity simulations suggest that under current pumping rates total land subsidence in the area of thickest lacustrine sediment will reach 15 m by the year 2010 if pumping is reduced to the extent that further decline in the potentiometric surface is prevented total maximum subsidence would be significantly less 10 m and the rate would nearly cease by 2010

nonlinear zonal propagation of organized convection in the tropics abstracta wide range of the observed variability in the itcz is frequently explained in terms of equatorially trapped modes arising from matsuno s linear shallow water model here a series of zona

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

the development and control of the land subsidence in the yangtze delta china land subsidence in china occurs predominantly in 17 provinces cities situated in the eastern and middle regions of the country including shanghai tianjin and jiangsu and hebei provinces it is primarily caused by groundwater overpumping one of the areas most severely affected by land subsidence is the yangtze delta most of which consists of shanghai city the su xi chang area suzhou wuxi and changzhou cities of jiangsu province and the hang jia hu area hangzhou jiaxing and huzhou cities of zhejiang province the excessive exploitation of groundwater forms in a large regional cone of depression and consequently land subsidence is also regional currently centered in the shanghai and su xi chang areas in 2002 the maximum cumulative subsidence of shanghai su xi chang and hang jia hu were 2 63 m 2 00 and 1 06 m respectively the land subsidence area is continuing to expand throughout the yangtze delta to study the characteristics and the pattern of this land subsidence the government has implemented a monitoring system involving the placement of 37 groups of extensometers layers marks and drilling of more than 1000 observation wells these provide an invaluable historical record of deformation and pore water pressure and facilitate studies on the special features of soil deformation when the groundwater level changes due to pumping several measures have been taken in recent years to control the development of the land subsidence in the different areas these include groundwater injection prohibition of pumping deep confined groundwater and an adjustment of the pumping depth and magnitude of the groundwater withdrawn at present although the subsidence area is still increasing slowly the subsidence rate is controlled

gravity waves in shear and implications for organized convection abstract it is known that gravity waves in the troposphere which are often excited by preexisting convection can favor or suppress the formation of new convection here it is shown that in the presence of wind shear or barotropic wind the gravity waves can create a more favorable environment on one side of preexisting convection than the other side both the nonlinear and linear analytic models developed here show that the greatest difference in favorability between the two sides is created by jet shears and little or no difference in favorability is created by wind profiles with shear at low levels and no shear in the upper troposphere a nonzero barotropic wind or equivalently a propagating heat source is shown to also affect the favorability on each side of the preexisting convection it is shown that these main features are captured by linear theory and advection by the background wind is the main physical mechanism at work these processes should play an important role in the organization of

a discussion of the application of mercury intrusion porosimetry for the investigation of soils including an evaluation of its use to estimate volume change in compacted clayey soils

genesis and evolution of hierarchical cloud clusters in a two dimensional cumulus resolving model abstract a two dimensional cloud ensemble model is integrated over a basin scale domain with prescribed sea surface temperature sst to study the formation and evolution of cloud clusters over a large scale warm pool neither a basic zonal flow is prescribed nor is a single perturbation initially given the results show that deep convective clouds appear in hierarchical clustered patterns and are limited to the area of warm sst above 28 c the most fundamental cloud cluster in the model has a horizontal scale of a few hundred kilometers in which new cumulus clouds are generated at the leading edge of a propagating surface cold air pool the gust front it may last for days and propagate for a long distance if the background flow is broad and persistent as is the case in the low level convergence zone of the sst induced background flow the largest hierarchical propagating cloud systems in the model have horizontal scales up to 3000 km and consist of up to four cloud clusters that are generally of gust

tropical intraseasonal oscillation super cloud clusters and cumulus convection schemes abstract a new framework for interpreting the origin of the tropical intraseasonal oscillation tiso which avoids the speed and scale selection problems in the previous theories is proposed in this study in this interpretation tiso is viewed as an oscillation driven by an eastward moving convective region this convective region consists of one or more super cloud clusters originating in the indian ocean and terminating in mid pacific and is then followed by another convective region arising in the indian ocean in a period of 40 50 days additionally a formal analogy is pointed out between super cloud clusters and the middle latitude baroclinic wave packets this study includes a simulation of tiso in a 2d model to support our interpretation experiments were conducted with four different convection schemes the authors advocate that the successful simulation of tiso depends on the successful simulation of super cloud clusters which in turn depends on the successful simulation of the life cycle of

effect of soil microstructure on the compressibility of natural singapore marine clay the effect of soil microstructure on the compressibility of natural singapore marine clay is studied in this paper it was found that natural singapore marine clay can sustain higher void ratio than reconstituted singapore marine clay at the same effective stress in one dimensional compression this difference is most noticeable between yield stress and two times the yield stress this void ratio difference is commonly attributed to soil microstructure and the decrease in this difference at higher stresses is attributed to progressive destructuration as a consequence of progressive destructuration the virgin compression curve is nonlinear and the compression index along the virgin compression range is variable which is only noticeable during the constant rate of strain consolidation test on high quality samples in the absence of high quality samples and constant rate of strain consolidation tests an empirical method is proposed to obtain a first order estimation of a nonlinear virgin compression cur

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

a microstructure approach to the sensitivity and compressibility of some eastern canada sensitive clays investigation of micro macro relationships in soils most often concerns granular soils in which both the elemental unit the grain and the physical laws governing inter grain interactions appear to be better known the situation is different for clays because the elementary unit and the inter unit interactions at the micro scale are more difficult to characterise in fine grained soils it has been shown that an intermediate level corresponding to the way clay and fine grained particles are arranged together had to be considered so as to link microscopic features to macroscopic behaviour an investigation of the change in microstructure during compression carried out some time ago on a sensitive clay from canada demonstrated that studying the changes in pore size distribution provides a satisfactory description of microstructure changes during compression the analysis is applied here to six other sensitive clays first a careful examination of the intact and remoulded microstructure is conducted in o

understanding the subsidence process of a quaternary plain by combining geological and hydrogeological modelling with satellite insar data the acque albule plain case study abstract this paper focuses on a multidisciplinary study carried out in an urban area affected by subsidence and related structural damages the study area is located about 20 km east of rome italy and is characterised by relevant groundwater exploitation for various purposes as well as by the presence of compressible soils immediately below the ground level extensive processing at different scales of sar satellite images ers and envisat provided by esa in the frame of a cat 1 project by means of a dinsar technique was performed the time histories of ground displacements have been analysed in combination with a detailed geological setting of the study area and with the hydrogeological changes occurred in the last decades as the response to the anthropic stress based on a large piezometric dataset this comprehensive dataset allowed us to describe the space and time distributions of the subsidence process the spatial pattern and deformation rate change is attributed to the following causes i the changes in the groundwater levels due to the intensification of mine exploitation requiring dewatering operations and ii the distribution and thickness of recent compressible deposits specifically it is derived that the groundwater level variations drive the timing of subsidence triggering over the area whereas the local geological conditions control the magnitude of the deformation process

a comprehensive mass flux scheme for cumulus parameterization in large scale models abstract observational studies indicate that a mass flux approach may provide a realistic framework for cumulus parameterization in large scale models but this approach through the introduction of a spectral cloud ensemble leads normally to rather complex schemes in this paper the question is addressed whether much simpler schemes can already provide realistic values of the thermal forcing by convection under various synoptic conditions this is done through verifying such a scheme first on data from field experiments for periods of tropical penetrative convection gate marshall islands tradewind cumuli atex bomex and extratropical organized convection sesame 79 and then in a nwp model the scheme considers a population of clouds where the cloud ensemble is described by a one dimensional bulk model as earlier applied by yanai et al in a diagnostic study of tropical convection cumulus scale downdrafts are included various types of convection are represented i e penetrative convection in c

effect of quaternary transgression and regression on the engineering properties of shanghai soft clays abstract the engineering properties of marine clays are closely related to its depositional environment however the correlation between the chemical properties and depositional environment and their effect on engineering properties of upper shanghai marine clay are still pending the sedimentary processes of upper shanghai marine clays from the quaternary transgression the correlation between the chemical properties and its depositional history are investigated in this study based on a series of laboratory experiments the distribution of chemical indicators e g ph value oxidation reduction potential and salt content with depth showed that the depositional environment directly affected the chemical properties of the soil layer the correlation of salt content with sensitivity liquid limit and liquidity index in upper shanghai layers represents a unique two stage distribution with the boundary at the bottom of the layer 4 clay the two stage distribution is caused by the quaternary transgression and regression which is confirmed to have different effects on the salt content sensitivity liquid limit and liquidity index the quantitative approaches used to evaluate the correlation between depositional environment chemical and mechanical properties can provide valuable references for investigating the engineering properties of soft clays

multiscale variability of deep convection in relation to large scale circulation in toga coare deep convection over the indo pacific oceanic warm pool in the tropical ocean global atmosphere coupled ocean atmosphere response experiment toga coare occurred in cloud clusters which grouped together in regions favoring their occurrence these large groups of cloud clusters produced large scale regions of satellite observed cold cloud top temperature this paper investigates the manner in which the cloud clusters were organized on time and space scales ranging from the seasonal mean pattern over the whole warm pool region to the scale of individual cloud clusters and their relationship to the large scale circulation and sea surface temperature sst the dominant convective variability was associated with the intraseasonal oscillation iso a large eastward propagating ensemble of cloud clusters marked the iso s progress the meridional structure of the iso was strongly affected by the seasonal cycle with a southward shift from the northern hemisphere in october november to the southern hemisphere in january february the sst had an intraseasonal signal in lagged quadrature with the cold cloudiness and rainfall in coare the sst increased decreased during the convectively suppressed active phases of the iso enhanced low level westerly winds occurred toward the later stages of the enhanced convection periods of the iso though not always centered at the equator the strongest westerlies tended to be located between two synoptic scale cyclonic gyres which were often not symmetric about the equator in the low level wind field this asymmetry in the anomalous equatorial low level westerlies may have different implications for the oceanic response in the coupled atmosphere ocean system than those centered on the equator the cyclonic gyres contained highly concentrated deep convection and in four cases the gyres developed into tropical cyclones within the envelope marking the convectively active phase of the iso cloud clusters were frequently concentrated into westward propagating disturbances with a local periodicity of similar to 2 days these 2 day disturbances have been identified in earlier spectral studies and appear to be related to westward propagating inertio gravity waves in coare they typically contained numerous cloud clusters which underwent a distinct diurnal cycle most of the cloud clusters embedded in the 2 day disturbances moved westward though some were stationary and a few moved eastward a cloud duster tracking program identified groups of clusters lime dusters that exhibited continuity in time and space in the most convectively active period of the iso the tracking program identified almost the entire iso cloud ensemble as a long lasting trackable superconvective system this observation indicates the lack of a distinct scale separation between convection and large scale disturbances during the most intense convective periods in coare

distributed acquisition characterization and process analysis of multi field information in slopes the slope is a multiphase composite system including solid liquid and gas phases slope stability changes under the actions of stress temperature and seepage slopes will be very prone to landslide if in an unstable state in this paper considering the contributions of different fields to the landslide the distributed acquisition characterization and stability analysis of multi field information from slopes was studied systematically using distributed fiber optic sensing dfos technology a sensing system based on dfos was designed and developed for multi field information monitoring including stress temperature seepage and deformation the corresponding methods for data processing identification and methods for characterization description are also proposed on this basis the evolution of the slope is analyzed finally monitoring results of the dfos system from the majiagou landslide are shown as a case study for verification

gregarious tropical convection abstract a beat source with a vertical profile like that of observed tropical mesoscale convective systems mcss is shown to cause through inviscid gravity wave dynamics upward displacement at low levels in a mesoscale region surrounding the heating typical values are 10 30 area contraction at the surface everywhere within 270 km of the heating 6 h after it starts as a result conditions near an existing mcs but beyond the area of mcs outflow become more favorable for the development of additional convection this theory predicts that cloud clusters should be gregarious infrared satellite imagery confirms that almost half of the cold cloudiness observed in a month over the oceanic warm pool region was contributed by just 14 objectively defined multiday supercluters

new precipitation and accumulation maps for greenland annual total precipitation and the annual accumulation on the greenland ice sheet are evaluated and presented in two maps the maps are based on accumulation measurements of 25 1 pits and cores obtained from the upper accumulation zone and precipitation measurements made at 35 meteorological stations in the coastal region to construct the accumulation map the annual precipitation was split into solid and liquid precipitation components annual total precipitation exceeding 2500 mm w e occurs on the southeastern tip of greenland while the minimum precipitation is estimated to occur on the northeastern slope of the ice sheet the mean annual precipitation for all of greenland is 340 mm w e the largest annual accumulation of about 1500 mm w e is found on the glaciers in the southeastern corner of greenland while the smallest accumulation is found on the northeastern slope of the ice sheet west of danmarkshavn the mean accumulation on the greenland ice sheet is estimated at 310 mm w e the regional difference in accumulation is examined with respect to the 850 hpa m bar level circulation the present surface topography is found to play an important role in determining regional accumulation on the ice sheet

the microscopic characteristics of shanghai soft clay and its effect on soil body deformation and land subsidence compaction of the 40 m thick upper shanghai soft clay contributes to land subsidence in the shanghai region the upper clay a marine deposit continuously subsides at rate of 3mm years despite mitigation strategies designed to control land subsidence these strategies include the artificial injection of water into the subsurface data describing the particle size distribution pore size distribution microstructure mineralogical composition pore solution composition and cation exchange capacity indicate that the clay is semidispersed substable and susceptible to compaction an evaluation of soil body deformation caused by artificial injection of dilute water into a marine clay suggests that depression of the electrostatic double 1ayer in the marine clays may be responsible for the observed compaction and resulting subsidence a decrease in the swelling pressure of the marine clays might result from a reduction in the concentration of dissolved sodium in pore fluids when calcium bicarbonate water is injected thus ironically the strategy designed to mitigate land subsidence could be contributing to it increasing the concentration of dissolved salts in the injection water may prevent the collapse of the clay structure and halt or reverse the subsidence process the analysis results indicate the deformation of soft clay by consolidation is subject to its microscopic physical and chemical features rather than the fluctuation of groundwater level this continuous compression contributes as a major part to the land subsidence in shanghai

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

time series analysis of subsidence associated with rapid urbanization in shanghai china measured with sbas insar method river delta plains deltas are susceptible to subsidence producing undesirable environmental impact and affecting dense population the city of shanghai located in the easternmost of yangtze delta in china is one of the most developed regions in china that experiences the greatest land subsidence excessive groundwater withdrawal is thought to be the primary cause of the land subsidence but rapid urbanization and economic development mass construction of skyscrapers metro lines and highways are also contributing factors in this paper a spatial temporal analysis of the land subsidence in shanghai was performed with the help of the small baseline subset interferometric synthetic aperture radar twenty l band alos palsar images acquired during 2007 2010 were used to produce a linear deformation rate map and to derive time series of ground deformation the results show homogeneous subsidence within the research area but exceptionally rapid subsidence around skyscrapers along metro lines elevated roads and highways was also observed because groundwater exploitation and rapid urbanization responsible for much of the subsidence in the shanghai region are expected to continue future subsidence monitoring is warranted

modeling visco elastic plastic deformation of soil with modified merchant model eighty four to ninety eight percent of land subsidence in shanghai city is caused by the visco elastic plastic deformation of sediments numerical experiments are done on the sediments with visco elastic plastic deformation in shanghai to verify the modified merchant model mm model and land subsidence model based on the modified merchant ls mm model there are two advantages of the mm model and the ls mm model one is that only a few parameters are involved there are three parameters in the mm model and four parameters in the ls mm model the other one is that both models can describe elastic elastic plastic and visco elastic deformation in addition to visco elastic plastic deformation the corresponding models are developed by setting proper values of the three parameters of 1 and 2 the two advantages make the ls mm model flexible and applicable to the simulation of the large regional land subsidence with visco elastic plastic deformation and other different kinds of deformation the results can be improved by variable parameters especially specific storage

observations of cloud cluster hierarchies over the tropical western pacific infrared radiance measurements at cloud top by the japanese geostationary meteorological satellite gms were used to study the structure and propagation of tropical convective systems over the equatorial western pacific results indicate that tropical convection in this region possesses three fundamental periodicities 1 day 2 3 days and 10 15 days cloud clusters within these convective systems interact to produce a hierarchy of collective motions covering all of these three basic time scales the 10 to 15 day time scale is closely related to the intraseasonal or 30 60 day oscillations that propagate from the indian ocean to the western pacific along the equator all year round large convective complexes known as supercloud clusters scc are found to organize in the 10 to 15 day time scale especially over the open warm water of the western central pacific 160 e to 180 the sccs generally propagate eastward although occasionally they can also propagate westward the zonal propagation can occur either continuously or intermittently in both cases the scc is found to be made up of several well organized cloud clusters which are generated at 2 to 3 day intervals and propagate in the opposite direction to the scc the diurnal variation is most pronounced over the maritime continent although significant amplitudes are also found over the open ocean the amplitude of the diurnal cycle is strongly modulated by the 2 to 3 day and 10 to 15 day oscillations advanced spectral analysis methods applied to convective indices derived from the radiance data confirm this hierarchical structure in cloud clusters in the tropical western pacific in addition to the embedding of well organized clusters within a scc in the spatial domain there is also a similar embedding by successive longer scales in the time domain interactions between the major frequency groups appear also to give rise to intermediate frequency variations a discussion of the present results in the context of equatorial wave dynamics of the moist tropical atmosphere is also presented