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1.
Excessive groundwater withdrawal from an aquifer system leads to three-dimensional displacement, causing changes in the states of stress and strain. Often, land subsidence and sometimes earth fissures ensue. Field investigation indicates that land subsidence and earth fissures in Wuxi, a city in eastern China, are mainly due to excessive groundwater withdrawal, and that they are temporally and spatially related to groundwater pumping. Groundwater withdrawal may cause tensile strain to develop in aquifer systems, but tensile strain does not definitely mean tensile stress. Where earth fissures are concerned, the stress state should be adopted in numerical simulations instead of the strain state and displacement. The numerical simulation undertaken for the Wuxi area shows that the zone of tensile strain occupies a large area on the ground surface; nevertheless, the zone of tensile stress is very limited. The zone of tensile stress often occurs near the ground surface, beneath which the depth to the bedrock surface is relatively small and has considerable variability. Earth fissures often initiate near the ground surface where tensile stress occurs. Tensile stress and earth fissures rarely develop at the centers of land subsidence bowls, where compressive stress is dominant. 相似文献
2.
Mechanics of land subsidence due to groundwater pumping 总被引：1，自引：0，他引：1
This paper presents the formulation of the basic mechanics governing the changes in stress states from groundwater pumping and comparisons among predicted land subsidence from this mechanics with existing analyses and field data. Land subsidence is a growing, global problem caused by petroleum and groundwater withdrawal, mining operations, natural settlement, hydro‐compaction, settlement of collapsible soils, settlement of organic soils and sinkholes. This paper is concerned with the land subsidence due to groundwater level decline by groundwater pumping. It is shown that the stress state consists of asymmetric stresses that are best simulated by a Cosserat rather than a Cauchy continuum. Land subsidence from groundwater level decline consists of vertical compression (consolidation), shear displacement and macro‐rotation. The latter occurs when conditions are favorable (e.g. at a vertical interface) for the micro‐rotation imposed by asymmetric stresses to become macro‐rotation. When the length of the cone of depression is beyond √2 times the thickness of the aquifer, simple shear on vertical planes with rotation is the predominant deformation mode. Otherwise, simple shear on horizontal planes is present. The predicted subsidence using the mechanics developed in this paper compares well with data from satellite‐borne interferometric synthetic aperture radar. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
Investigation into subsidence hazards due to groundwater pumping from Aquifer II in Changzhou,China 总被引：2，自引：1，他引：1
Ye-Shuang Xu Yao Yuan Shui-Long Shen Zhen-Yu Yin Huai-Na Wu Lei Ma 《Natural Hazards》2015,78(1):281-296
This paper presents an investigation into increased deformation of Aquifer II caused by groundwater pumping from the aquifer in Changzhou, China. As groundwater levels of aquifers have been decreasing in recent decades due to uncontrolled water pumping, land subsidence is becoming a serious geohazard in Changzhou. Based on recently reported field data, the compression of aquitards has not increased compared to that of aquifers with the same scale of layer thickness. The Cosserat continuum model was adopted to analyse the observed phenomenon in this study. A classic Cauchy continuum model is also used for comparison. The comparison between these two models indicates that the proposed approach can interpret the increased deformation well, and the classic Cauchy continuum model underestimates the aquifer deformation as it does not consider shear displacement and macro-rotation. A discussion on the relationship between the groundwater level in the aquifer and subsidence is then undertaken. The results show that the severity of the annual subsidence is correlated with the variation in groundwater level in Aquifer II. To mitigate the subsidence hazards, countermeasures should be adopted to avoid the shear stress in aquifers which results from the high hydraulic gradient, by the appropriate allocation of pumping wells and by restricting groundwater withdrawal volume from each pumping operation. 相似文献
4.
The stress–strain behaviour of a soil is crucial to the recognition of the mechanism of slope failure. Triaxial tests, composed of isotropically consolidated drained (ICD) and undrained compression (ICU) tests and anisotropically consolidated constant deviatoric stress path (CQD) tests, were carried out with the aim of investigating the stress–strain behaviour of loosely compacted volcanic-derived soils. The fact that the critical states are the same for ICU, ICD and CQD tests may show that the critical state is independent of the above three stress paths. The critical state line, as defined in critical state soil mechanics, is obtained from the e–log p′ and q–p′ plots based on the results of the above tests. The initial state of the consolidated specimens at initiation of failure may be classified as dilative or contractive in the light of the locations of the soil state relative to the critical state line. For contractional soils, the increased pore water pressure generated by rainfall infiltration leads to a contractive failure in a drained manner, giving rise to high excess pore water pressure. The excess pore water pressure caused by contraction cannot be dissipated instantly, resulting in a decrease in the shear resistance of the soil. The failure process is rapid. The failed soil mass is prone to flow after failure under the action of gravity due to its high moisture content and inflow of surface runoff and rainwater. For dilational soils, the increased pore water pressure resulting from infiltration leads to dilation, which reduces pore water pressure and thus increases the shear resistance of the soil. However, continued rainfall infiltration may be able to equilibrate the reduction in pore water pressure caused by dilation and, therefore, the dilation or displacement can continue. In Hong Kong, volcanic-derived soil is characterized by high permeability. Both the high permeability of volcanic-derived soil and a shallow failure surface make it possible for the reduction in pore pressure to equilibrate relatively quickly. Therefore, the failure is also rapid, at least for poorly compacted fill slopes. 相似文献
5.
High-resolution seismic reflections have been used effectively to investigate sinkholes formed from the dissolution of a bedded salt unit found throughout most of Central Kansas. Surface subsidence can have devastating effects on transportation structures. Roads, rails, bridges, and pipeliues can even be dramatically affected by minor ground instability. Areas susceptible to surface subsidence can put public safety at risk. Subsurface expressions significantly larger than surface depressions are consistently observed on seismic images recorded over sinkholes in Kansas. Until subsidence reaches the ground surface, failure appears to be controlled by compressional forces evidenced by faults with reverse orientation. Once a surface depression forms or dissolution of the salt slows or stops, subsidence structures are consistent with a tensional stress environment with prevalent normal faults. Detecting areas of rapid subsidence potential, prior to surface failure, is the ultimate goal of any geotechnical survey where the ground surface is susceptible to settling. Seismic reflection images have helped correlate active subsidence to dormant paleofeatures, project horizontal growth of active sinkholes based on subsurface structures, and appraise the risk of catastrophic failure. 相似文献
6.
Refraction seismic measurements from Kattegat have been analysed for information about Quaternary deposits. Preliminary results show a gradual increase in thickness of the Quaternary deposits from about 50m in the SW to 150–250m in the NE, close to the Swedish coast. A number of narrow zones with extraordinarily great thickness are superimposed on this surface. Comparisons with structural features in the pre-Quaternary, as known from reflection seismic investigations, strongly indicate that the 'Kattegat Basin' is a structural phenomenon generated by subsidence under tensional stress perpendicular to the Fennoscandian border zone. Stratigraphical analysis which is available from wells on the islands in Kattegat and in Vendsyssel shows that subsidence of the 'Kattegat Basin' was initiated in Holstein or earlier. 相似文献
7.
The extraction of groundwater can generate land subsidence by causing the compaction of susceptible aquifer systems, typically unconsolidated alluvial or basin-fill aquifer systems comprising aquifers and aquitards. Various ground-based and remotely sensed methods are used to measure and map subsidence. Many areas of subsidence caused by groundwater pumping have been identified and monitored, and corrective measures to slow or halt subsidence have been devised. Two principal means are used to mitigate subsidence caused by groundwater withdrawal??reduction of groundwater withdrawal, and artificial recharge. Analysis and simulation of aquifer-system compaction follow from the basic relations between head, stress, compressibility, and groundwater flow and are addressed primarily using two approaches??one based on conventional groundwater flow theory and one based on linear poroelasticity theory. Research and development to improve the assessment and analysis of aquifer-system compaction, the accompanying subsidence and potential ground ruptures are needed in the topic areas of the hydromechanical behavior of aquitards, the role of horizontal deformation, the application of differential synthetic aperture radar interferometry, and the regional-scale simulation of coupled groundwater flow and aquifer-system deformation to support resource management and hazard mitigation measures. 相似文献
8.
One of the more promising techniques in soft ground tunneling through urbanized areas is the use of artificially frozen ground for temporary tunnel support. This paper describes the general design considerations involved in the ground freezing method. Various factors are discussed which influence the selection of the freezing temperature, the thickness of the frozen zones and the spacing of the freeze pipes. The time required to achieve freezing is discussed in addition to the amount and rate of frost heave caused by the freezing.
To illustrate the applicability of the freezing method, various considerations in the design of an 8-ft. diameter tunnel in upstate New York, a 75-ft. diameter tunnel in Georgia, and a 12 1/2-ft. diameter tunnel in Washington, D.C. are discussed. All three of the tunnels were to pass immediately beneath mainline railroad tracks. A laboratory testing program was implemented to determine the effects of the repetitive train loads on the zone of frozen soil around the tunnel perimeter. Stress-controlled repeated load triaxial tests were performed on both undisturbed and remolded samples frozen from temperatures of −7°C for the New York tunnel to −10°C for the Atlanta and Washington tunnels. Static testing consisted of both quick triaxial tests and creep tests on frozen samples of the various soil types.
It was found that there was little difference between the cumulative strain response from repeated load tests and static tests for the low frequencies investigated (one-quarter to one-half cycles per minute). Hyperbolic stress—strain functions were developed to simulate the stress—strain relationship for various cumulative loading times.
The stresses and strains in the frozen soil tunnel configuration were computed by the finite element method, using both linear and hyperbolic stress—strain functions. Tangent modulus values were varied to reflect the decreasing modulus with increasing loading time. The analyses indicated that zones of frozen soil of approximately 3 ft. thick were required for both the New York and Washington tunnels. However, high tensile stresses were calculated for the Atlanta tunnel, precluding the use of the freezing method. 相似文献
9.
中国地面沉降及其需要解决的几个问题 总被引：46，自引：2，他引：46
我国地面沉降主要出现在东、中部17个省市,总面积超过5×104km2,同时在17个省市出现成因上与它有关的地裂缝,危害是多方面的。沉降发生在经济高速发展的东部地区,造成的危害和损失也更大。我国地面沉降有下列特点:过量开采地下水是主要原因;各土层变形量既与其压缩性有关,也与它本身的厚度有关;砂土变形基本特征是压缩过程中总的应力与应变关系为非线性,压缩变形以塑性变形为主并包含有蠕变;水位恢复到开采前水平,沉降仍在继续,存在滞后等。从目前研究,特别是模拟研究的现状出发,指出存在8个方面的不足,进而提出需要研究解决的6个科学问题,为提高我国的研究水平献策。 相似文献
10.
乌尔逊—贝尔凹陷构造调节带特征、成因机制及其地质意义 总被引：1，自引：0，他引：1
综合运用地震、钻井等资料,结合乌尔逊—贝尔凹陷南屯期断层特征分析,建立研究区调节带识别标志并圈定其发育范围,最终划分了2个Ⅰ级和18个Ⅱ级构造调节带,分为横向调节型、同向叠覆型、同向趋近型和背向平行型4类。研究结果认为,区域不协调伸展应变以及侧列断层发育模式导致在沿伸展断层走向基底相对脆弱地带发育构造调节带。这些地带不仅是油气的有利聚集部位,而且控制凹陷"S"型平面展布和沉降中心迁移以及沉积物厚度变化。构造调节带通过侧列断层、走向斜坡、纵向凸起及双向调节等模式控制各次凹物源体系方向。 相似文献
11.
J. Martínez J. Benavente J.L. García-Arstegui M.C. Hidalgo J. Rey 《Engineering Geology》2009,108(3-4):161-168
The coastal aquifer of the Plio-Quaternary delta sediment deposits of the Vélez river (province of Málaga, Spain) presents a highly irregular basement morphology and widely varying fill thickness (10–80 m between neighbouring sectors). The basin, which is tectonically controlled, is filled with lutite facies alternating with channel-filling rudites. This detrital aquifer is affected by seasonal seawater intrusion–extrusion processes due to increasing withdrawal of groundwater for human consumption and irrigation during dry periods.A study was performed to improve the hydrogeological knowledge of this coastal aquifer system. The study examined the morphology of the impervious substratum, the facies distribution and the position of the seawater wedge. For this purpose, an Electrical Resistivity Tomography (ERT) geophysical technique was used and the tomographic data were calibrated using geological observations and borehole studies. An analysis was carried out to compare the direct information obtained from the 35 boreholes with the indirect data corresponding to the four electrical tomography profiles. In the study, over 9660 resistivity data points were processed.The ERT profiles perfectly corroborated the information derived from the boreholes. The profiles made it possible to detect thickness changes, lithological changes and the presence of faults. Moreover, from a hydrogeologic standpoint, this research technique is capable of detecting the position of the phreatic level and, in coastal aquifers such as the one examined in this study, the possible horizontal or vertical penetration of seawater intrusion. Therefore, the electrical geophysical prospecting based on ERT can be highly useful in areas lacking sufficient geological information and/or mechanical borehole data. 相似文献
12.
13.
Gunnar Aas 《Engineering Geology》1981,18(1-4):67-78
In connection with the building of a railway tunnel through the City of Oslo, temporary improvement of the soft clay by freezing was considered in order to reinforce the tunnel ceiling in an area where the rock cover was insufficient. The same solution was also considered for another part of the tunnel where the problem was to prevent bottom heave failure in a deep excavation.
As this marine clay deposit has a very high salt content (about 25 g/l pore liquid), it was reasonable to believe that the strength of the frozen clay would be relatively low compared to previously published data concerning fresh clay soils. To investigate the stress—strain properties of frozen Oslo clay, a fairly comprehensive research programme was carried out; including two different temperature levels and using different testing techniques. The clay was tested in compression, tension, bending and shear, respectively. The tests were run very slowly, time to failure was normally 70–100 days.
This paper presents the main test results, which indicate that there exists a fairly well defined critical shear stress level for a given freezing temperature. As long as the stresses do not exceed this stress level, the creep deformations are small and the creep rates are constant or decreasing with time. On the other hand, higher shear stresses lead to very extensive deformations or failure. 相似文献
14.
Over-exploitation of groundwater in many evolving urban settings causes ground subsidence and permanent loss of aquifer storage capacity. DInSAR (differential interferometric synthetic aperture radar) time series data from 2016 to 2019 were used to monitor and model the surface deformation around Nairobi, Kenya, where the water demand has exceeded the supply without capacity augmentation for over two decades. The aquifer system constitutes hard rock to semiconfined ash beds in volcanic terrain. The Small Baseline DInSAR technique identified the spatial pattern of subsidence and magnitude (line-of-sight (LOS) velocity), which exceeds 41 mm/year in the semiconfined aquifer towards the western-central part of Nairobi. The spatial distribution of subsidence is consistent with the groundwater level drop and probable compaction modeled using aquifer characteristics for 1950–2015. The Global Navigation Satellite System (GNSS) data at a station from 2007 to 2018 indicate a cumulative 4-cm subsidence which is comparable to ~2.5-cm LOS subsidence from the present study for 2016–2019. The correlation with other hydrological data suggests the aquifer is experiencing inelastic subsidence due to unsustainable groundwater extraction, putting a massive strain on Nairobi’s aquifer system. The present DInSAR based study establishes its effectiveness in the monitoring of groundwater over-exploitation-based subsidence and associated hazard to the aquifer in emerging urban centers.
相似文献15.
G. Y. Wang Greg Guanlin You B. Shi S. L. Wu J. Q. Wu 《Environmental Earth Sciences》2010,61(5):1085-1093
Jiangyin County is in the infamous Su–Xi–Chang land subsidence area caused by excessive groundwater withdrawal in Jiangsu
province, China. The maximum accumulated land subsidence reached 1,310 mm near the centre of the subsiding trough in 2006
in southern Jiangyin, and earth fissures of significant vertical offsets have been observed at Changjing, Hetang and Wenlin
which form an arc towards the subsidence trough. An ancient Yangtze River course is found underlying and passing through the
depression in southern Jiangyin, forming a local basin surrounded by outcropped bedrock ridges in the north and south. The
Quaternary stratigraphy demonstrates significant heterogeneities in the basin; the second confined aquifer is much thicker
and deeper and encapsulated inside the basin and absent above the ridges. The development of earth fissures along the Changjing–Hetang–Wenlin
arc might be a combination of an inward rotation of sediments due to a large differential subsidence, an inward movement driven
by seepage force and a steeper slope along the south-eastern shoulder of the basin that facilitates the development of horizontal
tensile strain and/or shear strain necessary for fissuring. The land subsidence has slowed down and no new earth fissure zone
has occurred in the area after the banning of deep groundwater extraction was enacted in 2001. 相似文献
16.
大型工程开挖中,高地应力环境下高储能脆性岩体通常会通过脆性破裂快速释放应变能,产生岩爆。针对这类岩爆现象进行了一系列理论探讨,认为:(1)开挖条件下脆性岩体的岩爆破坏主要为张破裂或者张剪性破裂,破裂角一般较小,呈薄片状或刀口状。笔者认为开挖产生次生张应力和压剪应力条件下微裂纹裂尖出现张应力是可能的,因此采用格里菲斯强度理论研究开挖岩体破裂是有效的;(2)以格里菲斯强度理论为基础,分析了岩体在二维和三维情形下的岩爆破裂应力判据和破裂角,指出在有张应力的条件下,岩体的剪破裂角会减小,直至为零,这就解释了开挖面附近薄片状、刀口状破裂现象的原因;(3)分析了脆性岩体岩爆破裂的能量过程,指出张性破裂所耗能量较小,而张剪性和压剪性破裂耗能较高。认为岩爆破裂消耗的能量主要转化为新生裂纹的表面能和破裂碎片的动能,并指出表面能所占比例较动能为小。由此解释了脆性岩体岩爆破坏以动力效应为主的特征;(4)本文理论分析成果的工程应用价值在于:可以预示开挖脆性岩体破裂部位、破裂方式和破裂范围;提出岩爆破裂的张性应力控制依据。 相似文献
17.
Land subsidence and earth fissures due to groundwater withdrawal in the Southern Yangtse Delta,China 总被引：1，自引：0，他引：1
Yun Zhang Yu-Qun Xue Ji-Chun Wu Jun Yu Zi-Xin Wei Qin-Fen Li 《Environmental Geology》2008,55(4):751-762
Excessive extraction of groundwater has caused severe land subsidence and earth fissures in the Southern Yangtse Delta, China.
Based on field data, the temporal and spatial distribution of land subsidence is investigated and the causes for earth fissures
are analyzed. The areal distribution of the land subsidence is closely related to the cones of depression in the main exploited
aquifers. The compaction of a hydrostratigraphic unit depends on its mechanical behavior, thickness, compressibility, and
the piezometric level changing. The primary subsidence layers in Shanghai have been the first aquitard before 1990 and the
third confined aquifer since then. But the second aquitard unit was the primary subsidence layer in Changzhou. Earth fissures,
trending in several directions, occurred in the Husu tectonic zone. They were mainly caused by differential subsidence and
horizontal displacement that resulted from tensile stress and shear stress in units. The majority of fissures in the study
area are tensile. 相似文献
18.
Land subsidence in China 总被引：19，自引：0，他引：19
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. 相似文献
19.
20.
Progressive failure mechanism in one-dimensional stability analysis of shallow slope failures 总被引：3，自引：0，他引：3
Chia-Nan Liu 《Landslides》2009,6(2):129-137
In many slopes, overstressed zones can develop where the shear stress is larger than the available shear strength. Along a
shear surface within a soil exhibiting a strain-softening behavior, the shear displacement increases while the available shear
strength decreases. The excess shear stress is transferred from the overstressed zone to the adjacent zones, providing more
shear strength. This stress-transferring mechanism induces stress redistribution within the slope and could enlarge the overstress
zone. A one-dimensional model that satisfies the strain compatibility and force equilibrium is proposed for the stability
analysis of a slope of strain-softening behavior. This paper’s objective is to facilitate the application of this model to
estimate stress distribution along the failure surface of a strain-softening slope and thereafter the stability status. The
study presents a set of specific solutions to this model by describing and demonstrating procedures to identify the pattern
of a stress state and to calculate stress distribution within a one-dimensional, strain-softening slope. The progressive failure
mechanism is also investigated by using the proposed approach. As the magnitude of released stress gets large enough, it induces
an overstressed zone adjacent to the initial unstable zone and progressive failure develops. The proposed approach is also
applied to study the pattern of stress redistribution. It is found that the pattern of stress redistribution is affected by
the magnitude of released stress. It is too complex to be reasonably expressed by simple models. Though some limitations exist,
the proposed approach serves as a simple tool for a better understanding of the progressive failure mechanism. 相似文献