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1.
Geophysical methods—seismic refraction (SRFR), electrical resistivity tomography (ERT), and microgravity—were applied to the Dead Sea (DS) sinkhole problem in the Ein Gedi area at the earlier stage of the sinkhole development (1998–2002). They allowed determining the sinkhole formation mechanism and localizing the sinkhole hazardous zones. The SRFR method permitted to delineate the underground edge of a salt layer at the depth of 50 m. The salt edge was shaped like the sinkhole line on the surface. It was concluded that the sinkhole development is linked to the salt edge. Geoelectrical quasi-3D mapping based on the ERT technique detected large resistivity anomalies with 250–300 m2 diameter and 25–35 m deep. The Ein Gedi area has been also mapped by the use of Microgravity method. The residual Bouguer gravity anomaly map shows negative anomalies arranged along the edge of the salt layer. Those gravity anomalies overall are very similar in plan to the resistivity distribution in this area. The results of forward modeling indicate that both high resistivity and residual gravity anomalies are associated with a subsurface decompaction of the soil mass and deep cavity at the sinkhole site. Following monitoring of the sinkhole development carried out by the Geological Survey of Israel confirmed our suggestions. The drilling of numerous boreholes verified the location of the salt edge. Geographical Information System (GIS) database testifies that during 2003–2009 new sinkholes are continuing to develop along the salt edge within a narrow 50–100 m wide strip oriented approximately in north–south direction (slightly parallel to the shoreline). No promotion in west–east direction (perpendicularly to the DS shoreline) was observed in Israel. Collapse of sinkholes and their clustering have been occurred within the area of high resistivity anomaly and negative residual gravity anomaly. Similar studies carried out at the Ghor Al-Haditha area (Jordan) have shown that sinkholes there are also arranged along the winding line conforming to the salt edge. In this area sinkholes are slowly moved to the Dead Sea direction. Results of geophysical studies in numerous DS sites indicate similar sinkhole development. It allowed generating of the sinkhole formation model based on ancient (10,000–11,000-year old) salt belt girding the Dead Sea along its shores  相似文献   

2.
Sinkhole collapse is one of the main limitations on the development of karst areas, especially where bedrock is covered by unconsolidated material. Studies of sinkhole formation have shown that sinkholes are likely to develop in cutter (enlarged joint) zones as a result of subterranean erosion by flowing groundwater. Electrical resistivity imaging or tomography (RESTOM) is well suited to mapping sinkholes because of the ability of the technique for detecting resistive features and discriminating subtle resistivity variations. Two-dimensional electrical resistivity tomography surveys were conducted at two sinkhole sites near Cheria city where limestone is covered by about 10 m of clayey soils. A Wenner transect was conducted between the two sinkholes. The electrode spacing was 2 m. The length of transect is about 80 m. The survey results suggest that RESTOM is an ideal geophysical tool to aid in the detection and monitoring of sinkholes and other subsurface cavities.  相似文献   

3.
Sinkhole collapse is one of the main limitations in the development of karst areas, especially where bedrock is covered by unconsolidated material. Studies of sinkhole formation have shown that sinkholes are likely to develop in cutter (enlarged joint) zones as a result of subterranean erosion by flowing groundwater. Ground-penetrating radar (GPR) and electrical resistivity imaging or tomography (RESTOM) are well suited to mapping sinkholes because of the ability of these two techniques for detecting voids and discriminating subtle resistivity variations. Nine GPR profiles and two-dimensional electrical resistivity tomography have been applied, with relative success, to locate paleo-collapses and cavities, and to detect and characterize karst at two sinkhole sites near Cheria City where limestone is covered by about 10 m of clayey soils. The survey results suggest that GPR and RESTOM are ideal geophysical tools to aid in the detection and monitoring of sinkholes and other subsurface cavities.  相似文献   

4.
Approximately 60 % of the 2,150,000 km2 area of Saudi Arabia is underlain by soluble sediments (carbonate and evaporite rock formations, salt diapirs, sabkha deposits). Despite its hyper-arid climate, a wide variety of recent sinkholes have been reported in numerous areas, involving significant property losses. Human activities, most notably groundwater extraction, have induced unstable conditions on pre-existing cavities. This work provides an overview of the sinkhole hazard in Saudi Arabia, a scarcely explored topic. It identifies the main karst formations and the distribution of the most problematic sinkhole areas, illustrated through several case studies covering the wide spectrum of subsidence mechanisms. Some of the main investigation methods are presented through selected examples, including remote sensing, trenching and geophysics. Based on the available data, the main causal factors are identified and further actions that should be undertaken to better assess and manage the risk are discussed.  相似文献   

5.
Formation mechanism of large sinkhole collapses in Laibin,Guangxi, China   总被引：1，自引：1，他引：0  
On June 3, 2010, a series of karst sinkholes occurred at Jili village surrounded by Gui-Bei highway, Wu-Ping highway and Nan-Liu High-Speed Railway in Laibin, Guangxi, China. The straight-line distances from an large sinkhole pit, 85 m in diameter and 38 m in depth, to the above mainlines are 200, 600 and 500 m, respectively. Several investigation methods including geophysical technology, borehole and well drilling, groundwater elevation survey and hydrochemistry analysis of groundwater were used to study the formation mechanisms of these sinkholes. Based on the results, the spatial distribution of the Jili underground river was confirmed with a strike of SN along the middle Carboniferous limestone bedrock and the Quaternary deposits controlled the sinkhole formation. In addition, both historical sinkhole events and analysis of the groundwater–air pressure monitoring data installed in the underlying karst conduit system indicate that sinkholes in this area are more likely induced by extreme weather conditions within typical karst geological settings. Extreme weather conditions in the study area before the sinkhole collapses consisted of a year-long drought followed by continuous precipitation with a daily maximum precipitation of 442 mm between May 31 and June 1, 2010. Typical geological conditions include the Jili underground river overlain by the Quaternary overburden with thick clayey rubble. Especially in the recharge zone of the underground river, a stabilized shallow water table was formed in response to the extreme rainstorm because of the presence of the thick clayey rubble. When the underground conduit was flooded through the cave entrance on the surface, air blasting may have caused the cave roof collapse followed by formation of soil cavities and surface collapses. Borehole monitoring results of the groundwater–air pressure monitoring show that the potential karst sinkhole can pose threats to Shanbei village, the High-Speed Railway and the Wu-Ping highway. Local government needs to be aware of any early indicators of this geohazard so that devastating sinkholes can be prevented in the future. The results also suggest that groundwater–air pressure monitoring data collected both the Quaternary deposits and the bedrock karst system provide useful indicators for potential sinkhole collapses in similar karst areas where sinkholes usually occur during rainy season or karst groundwater level is always under the rockhead.  相似文献   

6.
Seismic refraction, magnetic resonance sounding (MRS), and the transient electromagnetic (TEM) method were applied to investigate the geological and hydrogeological conditions in the Nahal Hever South sinkhole development area at the Dead Sea (DS) coast of Israel. Microgravity and MRS results reliably reveal large karst cavity in the central part of investigated area. The map of the seismic velocity shows that sinkholes in Nahal Hever can be divided into two major groups: sinkholes close to the salt edge and sinkholes over compact salt formations between a few tens to a hundred meters from the major cavern. The present study shows that the formation of sinkholes of the first group is caused by soil collapsing into the cavern. In the area occupied by sinkholes of the second group, karst was not detected either by MRS or by seismic diffraction methods. TEM results reveal shallow clay layer saturated with DS brine underlain sinkholes of this group. It allows suggestion that the water drainage and intensive water circulation during rain events wash out fine rock particles from the unsaturated zone into the pre-existing cavern, initiating the formation of sinkholes of the second group. Karst development takes place at a very low bulk resistivity (<1 Ω m) of the DS aquifer, attesting to the fact that pores are filled with a highly saline solution. Refilling of the karstic cavities with collapsing and flushed soil slows down sinkhole development in the area. The sinkhole formation cycle at the site is estimated at 10 years. Sinkhole development throughout the studied area is triggered by a drop in the level of the DS, which reduces the head of the confined aquifer and the strength of the overlain sediments.
Abdallah Al-ZoubiEmail:
  相似文献   

7.
Quantitative sinkhole hazard assessments in karst areas allow calculation of the potential sinkhole risk and the performance of cost-benefit analyses. These estimations are of practical interest for planning, engineering, and insurance purposes. The sinkhole hazard assessments should include two components: the probability of occurrence of sinkholes (sinkholes/km2 year) and the severity of the sinkholes, which mainly refers to the subsidence mechanisms (progressive passive bending or catastrophic collapse) and the size of the sinkholes at the time of formation; a critical engineering design parameter. This requires the compilation of an exhaustive database on recent sinkholes, including information on the: (1) location, (2) chronology (precise date or age range), (3) size, and (4) subsidence mechanisms and rate. This work presents a hazard assessment from an alluvial evaporite karst area (0.81 km2) located in the periphery of the city of Zaragoza (Ebro River valley, NE Spain). Five sinkholes and four locations with features attributable to karstic subsidence where identified in an initial investigation phase providing a preliminary probability of occurrence of 0.14 sinkholes/km2 year (11.34% in annual probability). A trenching program conducted in a subsequent investigation phase allowed us to rule out the four probable sinkholes, reducing the probability of occurrence to 0.079 sinkholes/km2 year (6.4% in annual probability). The information on the severity indicates that collapse sinkholes 10–15 m in diameter may occur in the area. A detailed study of the deposits and deformational structures exposed by trenching in one of the sinkholes allowed us to infer a modern collapse sinkhole approximately 12 m in diameter and with a vertical throw of 8 m. This collapse structure is superimposed on a subsidence sinkhole around 80 m across that records at least 1.7 m of synsedimentary subsidence. Trenching, in combination with dating techniques, is proposed as a useful methodology to elucidate the origin of depressions with uncertain diagnosis and to gather practical information with predictive utility about particular sinkholes in alluvial karst settings: precise location, subsidence mechanisms and magnitude, and timing and rate of the subsidence episodes.  相似文献   

8.
The central Ebro Basin comprises thick evaporite materials whose high solubility produces typically karstic landforms. The sinkhole morphology developed in the overlying alluvium has been studied using gravimetry and ground-penetrating radar (GPR) on stream terraces, as well as analyzing the evolution of sinkhole morphologies observed in aerial photographs taken in 1928, 1957, and 1985. The sinkhole morphologies give some idea of possible subsurface processes as well as an indication of the final mechanisms involve in sinkhole development. On stream terraces and cover pediments the most commonly encountered dolines are bowl-shaped in their morphology with both diffuse and scarped edges. In contrast, dolines developed in the gypsiferous silt infilled valleys have a funnel and well-shaped morphology. The diffuse-edged bowl-shaped dolines are developed through the progressive subsidence of the alluvial cover, due to washing down of alluvial particles through small voids and cracks into deeper subsurface caves, resulting in a decrease alluvial density. Future compaction of the alluvial cover will produce surface subsidences. This type of dolines are associated with negative gravity anomalies. In contrast, the scarped-edge dolines are formed by the sudden collapse of a cavity roof. The cavities and cracks formed in the gypsum karst may migrate to the surface through the alluvial deposits by piping, and they may subsequently collapse. In this instance, the cavities can be detected by both gravity and GPR anomalies where the voids are not deeper than 4–5 m from the surface. These processes forming sinkholes can be enhanced by man-induced changes in the groundwater hydrologic regime by both inflows, due to irrigation, ditch losses, or pipe leakages, and by outflows from pumping activities.  相似文献   

9.
The Meitanba Coal Mine area in Hunan province, China, had been impacted by severe cover collapse sinkholes since 1982 due to mine dewatering. After the coal mine was closed in February 2015, the groundwater level has increased significantly. A series of sinkholes were recorded in the study area during groundwater-level recovery. Analysis of monitoring results and in-situ investigation indicated that 13 sinkhole collapses were more likely induced by abrupt change of groundwater–air pressure in response to heavy rainfall from March 2015 to July 2016 when the groundwater level increased by as much as 76 m. When the karst conduit was flooded, a relatively sealed environment was formed between saturated sediments and flooded karst conduit. Implosion of entrapped air might have caused the cave roof to collapse followed by surface collapses in a short time. On the other hand, four sinkholes occurred in November 2016 when the groundwater levels were near the soil–bedrock interface at elevations between 52.5 and 58.9 m amsl and the groundwater-level increase was at slower paces. Field measurements indicate that the groundwater-level fluctuation at the soil–bedrock interface could enlarge the soil cavity and accelerate the subsoil erosion process.  相似文献   

10.
This contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four Spanish Tertiary basins. Bedrock strata are subhorizontal evaporites, and in three of the basins they include halite and glauberite in the subsurface. Our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications; a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed. With the exception of solution dolines, it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements (cover, bedrock or caprock) and the main type of process involved (collapse, suffosion or sagging). Sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one (e.g. bedrock sagging and collapse sinkhole). The mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material, such as upward stoping of cavities by roof failure, development of well-defined failure planes and rock brecciation. Suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling. Sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock. The paleokarsts we analysed suggest that the sagging mechanism (not included in previous genetic classifications) plays an important role in the generation of sinkholes in evaporites. Moreover, collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst, primarily due to the greater solubility of the evaporites and the lower mechanical strength and ductile rheology of gypsum and salt rocks.  相似文献   

11.
《Applied Geochemistry》2005,20(10):1831-1847
The groundwater contribution into Green Lake and Black Lake (Vescovo Lakes Group), two cover collapse sinkholes in Pontina Plain (Central Italy), was estimated using water chemistry and a 222Rn budget. These data can constrain the interactions between sinkholes and deep seated fluid circulation, with a special focus on the possibility of the bedrock karst aquifer feeding the lake. The Rn budget accounted for all quantifiable surface and subsurface input and output fluxes including the flux across the sediment–water interface. The total value of groundwater discharge into Green Lake and Black Lake (∼540 ± 160 L s−1) obtained from the Rn budget is lower than, but comparable with historical data on the springs group discharge estimated in the same period of the year (800 ± 90 L s−1). Besides being an indirect test for the reliability of the Rn-budget “tool”, it confirms that both Green and Black Lake are effectively springs and not simply “water filled” sinkholes. New data on the water chemistry and the groundwater fluxes into the sinkhole area of Vescovo Lakes allows the assessment of the mechanism responsible for sinkhole formation in Pontina Plain and suggests the necessity of monitoring the changes of physical and chemical parameters of groundwater below the plain in order to mitigate the associated risk.  相似文献   

12.
Induced sinkholes (catastrophic subsidence) are those caused or accelerated by human activities These sinkholes commonly result from a water level decline due to pumpage Construction activities in a cone of depression greatly increases the likelihood of sinkhole occurrence Almost all occur where cavities develop in unconsolidated deposits overlying solution openings in carbonate rocks. Triggering mechanisms resulting from water level declines are (1) loss of buoyant support of the water, (2) increased gradient and water velocity, (3) water-level fluctuations, and (4) induced recharge Construction activities triggering sinkhole development include ditching, removing overburden, drilling, movement of heavy equipment, blasting and the diversion and impoundment of drainage Triggering mechanisms include piping, saturation, and loading Induced sinkholes resulting from human water development/management activities are most predictable in a youthful karst area impacted by groundwater withdrawals Shape, depth, and timing of catastrophic subsidence can be predicted in general terms Remote sensing techniques are used in prediction of locations of catastrophic subsidence. This provides a basis for design and relocation of structures such as a gas pipeline, dam, or building Utilization of techniques and a case history of the relocation of a pipeline are described  相似文献   

13.
湖南煤炭坝煤矿是我国著名的大水矿山,开采标高已降至-400 m,每小时排水量11 000 m3。长期的疏干排水,已形成面积达219.19 km2的地下水降落漏斗。以往的调查资料表明,矿山疏干诱发的岩溶塌陷主要发生在疏干开始、地下水位下降到基岩面附近、矿坑发生突水突泥灾害等3个阶段,在疏干区应该无诱发因素导致岩溶塌陷的发生。但近年来煤炭坝煤矿疏干区大成桥的岩溶塌陷特征表明,尽管相关部门采取了一系列处置措施,但岩溶塌陷仍然频繁发生。为了进一步揭示该地区岩溶塌陷发育规律,使处置决策更加科学化,作者所在团队选择大成桥为典型区,通过岩溶系统地下水气压力监测,分析诱发岩溶塌陷的动力来源及其变化规律。结果表明,疏干区岩溶管道裂隙系统中水气压力突变现象极为明显,年最大变幅达54.72 m,瞬时水气压力变化速率最大为70.6 cm/min,造成这一现象的主要原因是气爆、地下洞穴（溶洞、土洞）垮塌。   相似文献   

14.
截止2016年底,大成桥疏干区在地下水位恢复过程中共发生了17起岩溶塌陷,文章结合地下水动态监测、水文地质钻探成果以及现场调查资料等,研究地下水恢复特征及其对岩溶塌陷的作用机制,为研究区塌陷的预警防治提供科学依据。结果表明:研究区岩溶塌陷集中在河流两岸阶地和麻枣冲沟中;岩溶塌陷发生顺序为先补给区后径流区,与地下水恢复动态过程密切相关;区内地下水恢复过程可分为4个阶段,不同阶段岩溶塌陷机理可分为渗流潜蚀-气爆效应,负压吸蚀效应,软化增荷-挤压-吸蚀效应和软化-崩解效应等4种力学效应组合,不同力学效应作用下的致塌模式有所不同。其中地下水位在基岩面附近4~5 m范围波动更容易引发岩溶塌陷。目前补给区地下水位标高63.95~71.8 m,高于基岩面5~6 m;径流区为42.8~57.7 m,位于基岩面以下4~17 m,因此须密切观测研究区地下水位变化。   相似文献   

15.
In the valley of the Ebro River to the southeast of the city of Zaragoza (NE Spain), the dissolution of evaporite sediments (gypsum, halite and Na-sulphates) which underlie alluvial deposits gives rise to numerous sinkholes. These sinkholes are a potential hazard to human safety, particularly where they develop in a catastrophic way. Even slow-developing sinkholes are problematic, as they damage urban and agricultural infrastructure, necessitating costly repairs and vigilant maintenance. To assist in developing avoidance strategies for these hazards, the factors controlling sinkhole occurrence have been assessed using geomorphological maps produced from aerial photographs for 1956 and 1981. Important controls on sinkhole development are found to include underlying geological structure (manifest in preferred orientations of sinkholes on the azimuths N130-150E and N30-40E), and the presence of glauberite in the groundwater flow path, which apparently promotes accelerated gypsum dissolution. Perhaps surprisingly, alluvium thickness does not appear to significantly correlate with the density of sinkholes on the floodplain in this area. The maps for 1956 and 1981 reveal that both human activity and natural processes can serve to obscure the true density of sinkhole development. For instance, a large number of sinkholes which were conspicuous in 1956 have since been back-filled by farmers. In the most fluvially active zone of the Ebro valley (the meander belt), the relatively low density of sinkholes compared with adjoining zones suggests that subsidence is being masked by morpho-sedimentary dynamic processes (aggradation and erosion). Careful geomorphological mapping for different time periods yields a much more accurate impression of the frequency of sinkhole development than would be gained from surveying currently visible sinkholes in the area of interest.  相似文献   

16.
For the last four decades, the level of the Dead Sea has been subjected to continual variation which, among other important factors, has led to the occurrence of much subsidence and many sinkholes in the southern Dead Sea area. Sinkhole activities occurred repetitively and were observed in open farms, across roads, near dwellings and near an existing factory, thus causing a serious threat to the locals and farmers of the area and their properties. This paper presents the main results from detailed geological and geotechnical studies of this area. Aerial photo interpretation and borehole drilling aided these studies. Parallel geophysical investigations (vertical electrical sounding and seismic refraction) and hydrological and hydrogeological studies were made by others in the same area to also investigate this phenomenon. It was found that sinkholes are aligned to and follow old water channels and are concentrated parallel to the recent shoreline of the Dead Sea. The development of subsurface cavities is associated mainly with the variation in the level of the Dead Sea over the four past decades, the presence of regional salt intrusion under the surface of salt beds, the fluctuation of the water table and continuous dissolution and the active tectonism of the area. Moreover, this work showed that the area is still under active sinkhole hazards and other parts of the area will be inevitably affected by sinkholes in the future.No practical engineering solution to this problem is feasible. Received: 1 July 1999 / Accepted: 11 October 1999  相似文献   

17.
An active sinkhole around 100 m long has been investigated in the city of Zaragoza (NE Spain). Subsidence activity on this depression, including the sudden occurrence of a collapse sinkhole 5 m across, led to the abandonment of a factory in the 1990s. At the present time, a building with 100 flats and shallow pad foundations partially built on the sinkhole, is affected by rapid differential settlement. The development of the sinkhole results from the karstification of the halite- and glauberite- bearing bedrock and the sagging and collapse of the overlying bedrock and alluvium, more than 30 m thick. GPR and electrical resistivity profiles have provided information on the distribution and geometry of the subsidence structure. The application of the trenching technique and geochronological methods (AMS and OSL dating) has allowed us to infer objective and practical data on the sinkhole including (1) Limits of the subsidence structure, (2) subsidence mechanisms, (3) cumulative subsidence (>408 cm), (4) subsidence rates on specific failure planes (>1.8 cm/year), (5) episodic displacement regime of some fault planes. The available information indicates that the progressive deformation recorded in the building will continue and might be punctuated by events of more rapid displacement. This work illustrates the practicality of the trenching technique for the study of sinkholes in mantled karst areas.  相似文献   

18.
When karst lands are developed for residential or commercial purposes, sinkholes are to be properly managed or mitigated. This paper discusses various types of sinkholes and their possible formation mechanisms, presents some guidelines for sinkhole management, and summarizes several engineering measures for sinkhole remediation. Because a sinkhole is often not an isolated feature but a component of an integrated groundwater and surface water system, knowledge of the sinkhole geology and hydrology is essential in selection of the proper management tools and remediation options. Adverse effects including flooding, additional sinkholes, and groundwater contamination can result from poorly managed or improperly repaired sinkholes.  相似文献   

19.
 Several areas of Nakuru Town and its environs often undergo subsidence along the parallel fault zones during and after heavy rainfall. During the rainy season, when most of the subsidence occurs, the overlying unconsolidated volcanoclastic sediments become oversaturated with water. The water reduces the shear strength of the sediments and also introduces extra loading through saturation leading to subterranean erosion along faults. The unconsolidated sediments then collapse into the subsurface water channels which closely follow the fault zones, leading to formation of “sinkholes”. The frequent incidences of ground subsidence in the study area, have caused several fatalities, destroyed settlements and physical infrastructure. Furthermore persistent subsidence has increased the cost of construction and the repair of the destroyed properties. Apart from being hazardous, ground subsidence degrades environment when sewage water, refuse and garbage enter into the groundwater systems through the sinkholes. The fissures formed after subsidence also stand prominently as ugly features from the rest of the terrain. Mitigation measures including control, channelizing of drainage, proper engineering practices and appropriate land use are suggested in this paper. Received: 1 December 1998 · Accepted: 8 March 1999  相似文献   

20.
The Crestatx aquifer is the main source of water supply to the Bay of Alcudia, one of the largest resorts on the island of Majorca (Spain). This water has been used since the 1970s using several pumping wells, which draw an annual volume of 1.5 hm3. The seasonal exploitation of this karstic aquifer causes a substantial cone of depression with great variations in the piezometric level (up to 120 m) and dynamic water levels of down to 87 m below sea level. At the end of the 1990s, several sinkholes and subsidence depressions started being detected in a highly karstified area. Twenty subsidence and sinkhole morphologies have been inventoried in an area measuring 70,000 m2, with diameters up to 23 m and depth more than 15 m. The intense and continuous rainfall during recent years (2008–2010) has considerably accelerated the process, increasing the dimensions of existing sinkholes and the appearance of new morphologies. By means of electrical tomography techniques, a ground study was carried out. Numerous cavities have been identified in the upper 30 m. Using a map of the surface morphologies and the geophysical profiles, we can determine that the propagation and orientation of the sinkholes lie along three main directions: N30°E, N130°E and N60°E. The first is the most relevant, which is parallel to the main tectonic structures in the area. The interpretation of the electrical profiles has enabled us to identify the potentially most unstable areas, which is an effective tool to assess risk in the area, as there are roads and a housing development nearby. The high, but discontinuous, exploitation of the aquifer is considered the main trigger for these sinkholes and subsidence depressions, as it causes large variations of pressure and accelerates the dissolution process in the underlying rock.  相似文献   

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