Aquifer thermal energy storage(ATES)system has received attention for heating or cooling buildings.However,it is well known that land subsidence becomes a major environmental concern for ATES projects.Yet,the effect o...Aquifer thermal energy storage(ATES)system has received attention for heating or cooling buildings.However,it is well known that land subsidence becomes a major environmental concern for ATES projects.Yet,the effect of temperature on land subsidence has received practically no attention in the past.This paper presents a thermo-hydro-mechanical(THM)coupled numerical study on an ATES system in Shanghai,China.Four water wells were installed for seasonal heating and cooling of an agriculture greenhouse.The target aquifer at a depth of 74e104.5 m consisted of alternating layers of sand and silty sand and was covered with clay.Groundwater level,temperature,and land subsidence data from 2015 to 2017 were collected using field monitoring instruments.Constrained by data,we constructed a field scale three-dimensional(3D)model using TOUGH(Transport of Unsaturated Groundwater and Heat)and FLAC3D(Fast Lagrangian Analysis of Continua)equipped with a thermo-elastoplastic constitutive model.The effectiveness of the numerical model was validated by field data.The model was used to reproduce groundwater flow,heat transfer,and mechanical responses in porous media over three years and capture the thermo-and pressure-induced land subsidence.The results show that the maximum thermoinduced land subsidence accounts for about 60%of the total subsidence.The thermo-induced subsidence is slightly greater in winter than that in summer,and more pronounced near the cold well area than the hot well area.This study provides some valuable guidelines for controlling land subsidence caused by ATES systems installed in soft soils.展开更多
Based on a large number of newly added deep well data in recent years,the subsidence of the Ordos Basin in the Mid-Late Triassic is systematically studied,and it is proposed that the Ordos Basin experienced two import...Based on a large number of newly added deep well data in recent years,the subsidence of the Ordos Basin in the Mid-Late Triassic is systematically studied,and it is proposed that the Ordos Basin experienced two important subsidence events during this depositional period.Through contrastive analysis of the two stages of tectonic subsidence,including stratigraphic characteristics,lithology combination,location of catchment area and sedimentary evolution,it is proposed that both of them are responses to the Indosinian Qinling tectonic activity on the edge of the craton basin.The early subsidence occurred in the Chang 10 Member was featured by high amplitude,large debris supply and fast deposition rate,with coarse debris filling and rapid subsidence accompanied by rapid accumulation,resulting in strata thickness increasing from northeast to southwest in wedge-shape.The subsidence center was located in Huanxian–Zhenyuan–Qingyang–Zhengning areas of southwestern basin with the strata thickness of 800–1300 m.The subsidence center deviating from the depocenter developed multiple catchment areas,until then,unified lake basin has not been formed yet.Under the combined action of subsidence and Carnian heavy rainfall event during the deposition period of Chang 7 Member,a large deep-water depression was formed with slow deposition rate,and the subsidence center coincided with the depocenter basically in the Mahuangshan–Huachi–Huangling areas.The deep-water sediments were 120–320 m thick in the subsidence center,characterized by fine grain.There are differences in the mechanism between the two stages of subsidence.The early one was the response to the northward subduction of the MianLüe Ocean and intense depression under compression in Qinling during Mid-Triassic.The later subsidence is controlled by the weak extensional tectonic environment of the post-collision stage during Late Triassic.展开更多
Despite the high efficiency of remote sensing methods for rapid and large-scale detection of subsidence phenomena,this technique has limitations such as atmospheric impact and temporal and spatial decorrelation that a...Despite the high efficiency of remote sensing methods for rapid and large-scale detection of subsidence phenomena,this technique has limitations such as atmospheric impact and temporal and spatial decorrelation that affect the accuracy of the results.This paper proposes a method based on an artificial neural network to improve the results of monitoring land subsidence due to groundwater overexploitation by radar interferometry in the Aliabad plain(Central Iran).In this regard,vertical ground deformations were monitored over 18 months using the Sentinel-1A SAR images.To model the land subsidence by a multilayer perceptron(MLP)artificial neural network,four parameters,including groundwater level,alluvial thickness,elastic modulus,and transmissivity have been applied.The model's generalizability was assessed using data derived for 144 days.According to the results,the neural network estimates the land subsidence at each ground point with an accuracy of 6.8 mm.A comparison between the predicted and actual values indicated a significant agreement.The MLP model can be used to improve the results of subsidence detection in the study area or other areas with similar characteristics.展开更多
When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key...When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key strata as a semi-infinite Euler-Bernoulli beam rested on a Winkler foundation with a local subsidence area.The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff.Then,the analytical solutions are verified by the results from experimental tests,FEM and InSAR,respectively.After that,the influence of changing parameters on deflections is studied with sensitivity analysis.The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam.The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam.The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.展开更多
Groundwater serves as an important water source for residents in and around mining areas.To achieve scientific planning and efficient utilization of water resources in mining areas,it is essential to figure out the ch...Groundwater serves as an important water source for residents in and around mining areas.To achieve scientific planning and efficient utilization of water resources in mining areas,it is essential to figure out the chemical formation process and the ground water sulfur cycle that transpire after the coal mining activities.Based on studies of hydrochemistry and D,^(18)O-H_(2)O,^(34)S-SO_(4)isotopes,this study applied principal component analysis,ion ratio and other methods in its attempts to reveal the hydrogeochemical action and sulfur cycle in the subsidence area of Pingyu mining area.The study discovered that,in the studied area,precipitation provides the major supply of groundwater and the main water chemistry effects are dominated by oxidation dissolution of sulfide minerals as well as the dissolution of carbonate and silicate rocks.The sulfate in groundwater primarily originates from oxidation and dissolution of sulfide minerals in coal-bearing strata and human activities.The mixed sulfate formed by the oxidation of sulfide minerals and by human activities continuously recharges the groundwater,promoting the dissolution of carbonate rock and silicate rock in the process.展开更多
In the context of global degradation and loss of natural wetlands,waterbirds have been increasingly using artificial wetlands as alternative habitats.However,waterbirds are facing various threats in these artificial w...In the context of global degradation and loss of natural wetlands,waterbirds have been increasingly using artificial wetlands as alternative habitats.However,waterbirds are facing various threats in these artificial wetlands,due to dramatic environmental changes induced by anthropogenic activities.Exploring the effects of these changes on the temporal dynamics of the waterbird communities can help understand how waterbirds adapt to environmental changes and thus formulate effective management and conservation plans.In this study,we carried out field surveys on waterbirds and environmental factors across 20 subsidence wetlands created by underground coal mining in the Huainan coal mining area in the breeding seasons of 2016 and 2021.We predicted that the waterbird assemblages(i.e.,number of individuals,species richness,Shannon-Wiener diversity,Pielou evenness and species composition) differed between the two years,and that these differences were correlated with the temporal changes in environmental factors.Across the surveyed wetlands,we recorded 26 waterbird species in 2016 and 23 in 2021.For individual wetlands,the number of waterbird individuals and species richness increased by 71.6% and 20.1%,respectively,over the five years,with no changes in Shannon-Wiener diversity and Pielou evenness.The overall increase in the number of bird individuals was mainly caused by an increase in vegetation gleaners and gulls that adapt well to anthropogenic activities.The species composition was significantly different between the two years,which was mainly caused by changes in the number of individuals of dominant species under influence of changes in human activities.For most wetlands,the temporal pairwiseβ-diversities could be explained by species turnover rather than nestedness,probably due to high mobility of waterbird species and dramatic changes in local environments.Our study suggests that waterbird communities could respond to environmental changes in subsidence wetlands,providing important implications for waterbird conservation in human-dominated artificial wetlands.展开更多
Subsidence data acquisition methods are crucial to mining subsidence research and an essential component of achieving the goal of environmentally friendly coal mining.The origin and history of the existing methods of ...Subsidence data acquisition methods are crucial to mining subsidence research and an essential component of achieving the goal of environmentally friendly coal mining.The origin and history of the existing methods of field monitoring,calcula-tion,and simulation were introduced.It summarized and analyzed the main applications,flaws and solutions,and improve-ments of these methods.Based on this analysis,the future developing directions of subsidence data acquisition methods were prospected and suggested.The subsidence monitoring methods have evolved from conventional ground monitoring to combined methods involving ground-based,space-based,and air-based measurements.While the conventional methods are mature in technology and reliable in accuracy,emerging remote sensing technologies have obvious advantages in terms of reducing field workload and increasing data coverage.However,these remote sensing methods require further technological development to be more suitable for monitoring mining subsidence.The existing subsidence calculation methods have been applied to various geological and mining conditions,and many improvements have already been made.In the future,more attention should be paid to unifying the studies of calculation methods and mechanical principles.The simulation methods are quite dependent on the similarity of the model to the site conditions and are generally used as an auxiliary data source for subsidence studies.The cross-disciplinary studies between subsidence data acquisition methods and other technologies should be given serious consideration,as they can be expected to lead to breakthroughs in areas such as theories,devices,software,and other aspects.展开更多
Coastal subsidence monitoring typically employs Global Navigation Satellite System(GNSS)positioning technology.This method provides information only about subsidence below the station base.Sediments in coastal areas t...Coastal subsidence monitoring typically employs Global Navigation Satellite System(GNSS)positioning technology.This method provides information only about subsidence below the station base.Sediments in coastal areas tend to accumulate quickly,and subsidence can change significantly due to compaction and alluvium.Therefore,monitoring subsidence above the base is essential to obtain overall coastal subsidence.A new technology called GNSS-Interferometric Reflectometry(GNSS-IR)has been recently developed,which can utilize multipath effects to monitor reflector height.Since the base of the GNSS station is deep and the base length remains constant,the height changes measured by the GNSS-IR technology can reflect subsidence above the base.Accordingly,this paper employs GNSS-IR technology to measure subsidence changes above the base.Additionally,GNSS positioning technology is used to obtain subsidence changes below the base,and the overall subsidence change is then calculated using both GNSS-IR and GNSS positioning technology.The Mississippi River Delta,known for its significant sediment thickness,was selected as the study area,and data from FSHS,GRIS,and MSIN stations was analyzed.The results demonstrate that GNSS-IR can be used to measure the subsidence rate above the base,and the corrected overall subsidence rate is equivalent to the relative sea level rise rate.展开更多
Undergroundgas storage caverns aremonitoredfor environmental safety in termsof equipmentandpotential emissions,particularly methane emissions from the underground and above-ground parts of the storage facility.Periodi...Undergroundgas storage caverns aremonitoredfor environmental safety in termsof equipmentandpotential emissions,particularly methane emissions from the underground and above-ground parts of the storage facility.Periodical measurements of land surface deformations and costly echometric measurements of convergence of individual storage facilities are carried out.The aims of environmental monitoring are:(1)to eliminate potential hazards in the shortest time,(2)assess the overall impact of intensive operation of storage facilities on the environment,(3)developmonitoringmethods relevant to environmental protection,and(4)take actions in case of failure.The paper presents a solution to the problem of determination of the convergence of underground caverns in a salt rock mass based on the results of land surface subsidence measurements carried out using the Gauss-Markov equalization algorithm.Themethod makes it possible for ongoing control of cavern volume convergence after each subsidence measurement on the ground surface and determining the actual impact of the use frequency(injection-mediumconsumption)on the convergence in time.The presentedmethodology is universal and verified on caverns located in a salt rockmass.The Gauss-Markov inversion model is the first used in this area,hence its application is significant.展开更多
The India–Eurasia collision has produced a number of Cenozoic deep intracontinental basins,which bear important information for revealing the far-afield responses to the remote collision.Despite their significance,th...The India–Eurasia collision has produced a number of Cenozoic deep intracontinental basins,which bear important information for revealing the far-afield responses to the remote collision.Despite their significance,their subsiding mechanism remains the subject of debate,with end-member models attributing it to either orogenic or sedimentary load.In this study,we conduct flexural subsidence modeling with a two-dimensional finite elastic plate model on the Hotan-Mazatagh section along the southern Tarim Basin,which defines a key region in the foreland of the West Kunlun Orogen,along the NW margin of the Tibetan Plateau.The modeling results indicate that the orogenic load of West Kunlun triggers the southern Tarim Basin to subside by up to less than ~6 km,with its impact weakening towards the basin interiors until ~230 km north from the Karakax fault.The sedimentary load,consisting of Cenozoic strata,forces the basin to subside by ~2 to~7 km.In combination with the retreat of the proto-Paratethys Sea and the paleogeographic reorganization of the Tarim Basin,we propose that surface processes,in particular a shift from an exorheic to an endorheic drainage system associated with the consequent thick sedimentary load,played a decisive role in forming deep intracontinental basins in the context of the India-Eurasia collision.展开更多
Long-term field monitoring finds that serious surface subsidence can still occur even if the high strength cemented fill method is adopted.Combining the results of numerical simulations with global position system(GPS...Long-term field monitoring finds that serious surface subsidence can still occur even if the high strength cemented fill method is adopted.Combining the results of numerical simulations with global position system(GPS)monitoring,we took a typical filling mining mine with a steeply inclined ore body as an example,and explored its ground subsidence mechanism.The results show that the ground subsidence caused by the mining of steep ore body is characterized by two settlement centers and a significantly uneven spatial distribution,which is visibly different from ground subsidence characteristic of the coal mine.The subsidence on the hanging wall is much larger than that on the footwall,and the settlement center tends to move to the hanging wall with the increase of mining depth.The backfill improves the strength and surrounding rock bearing capacity,which leads to a lag of about 3 years of the subsidence.However,under the actions of continuous and repeated mining disturbances,the supporting effect of the backfill can only reduce the amplitude of the deformation,but it cannot prevent the occurrence of settlement.展开更多
During subway operation,various factors will cause long-term land subsidence,such as the vibration subsidence of foundation soil caused by train vibration load,incomplete consolidation deformation of foundation soil d...During subway operation,various factors will cause long-term land subsidence,such as the vibration subsidence of foundation soil caused by train vibration load,incomplete consolidation deformation of foundation soil during tunnel construction,dense buildings and structures in the vicinity of the tunnel,and changes in water level in the stratum where the tunnel is located.The monitoring of long-term land subsidence during subway operation in high-density urban areas differs from that in low-density urban construction areas.The former is the gathering point of the entire urban population.There are many complex buildings around the project,busy road traffic,high pedestrian flow,and less vegetation cover.Several existing items requiremonitoring.However,monitoring distance is long,and providing early warning is difficult.This study uses the 2.8 km operation line between Wulin Square station and Ding’an Road station of Hangzhou Subway Line 1 as an example to propose the integrated method of DInSAR-GPS-GIS technology and the key algorithm for long-term land subsidence deformation.Then,it selects multiscene image data to analyze long-termland subsidence of high-density urban areas during subway operation.Results show that long-term land subsidence caused by the operation of Wulin Square station to Ding’an Road station of Hangzhou Subway Line 1 is small,with maximumsubsidence of 30.64 mm,and minimumsubsidence of 11.45 mm,and average subsidence ranging from 19.27 to 21.33 mm.And FLAC3D software was used to verify the monitoring situation,using the geological conditions of the soil in the study area and the tunnel profile to simulate the settlement under vehicle load,and the simulation results tended to be consistent with the monitoring situation.展开更多
Land subsidence is a severe hazard threatening Tanggu, a flat lowland area, and evidences of land subsidence can be seen throughout the city. A new reasonable GPS network was set up in this area from 2008 to 2010. The...Land subsidence is a severe hazard threatening Tanggu, a flat lowland area, and evidences of land subsidence can be seen throughout the city. A new reasonable GPS network was set up in this area from 2008 to 2010. The monitoring data show that land subsidence was serious and two main subsidence cones were obviously formed in the region. One emerged at Hujiayuan, with the maximum rate reaching 60 ram/a, and the influence region enlarged prominently from 2005 to 2010. The other one occurred at Kaifaqu, which became obvious only after 2005, and it showed a decreasing tendency with time. To analyze the causes of ground settlement, a correlation between groundwater withdrawal and land subsidence was firstly made. The results confirmed that over-exploitation of groundwater was the major cause for the severe settlement in Hujiayuan. Meanwhile, the subsidence of Kaifaqu was also related to groundwater withdrawal before 2005. However, the relationship became unconspicuous after 2005. To find the cause of this abnormity, a three-dimensional finite element numerical model, coupled with groundwater flow and subsidence, was built. The simulation results indicate that the subsidence induced by high-rise buildings is serious, but the affected range is limited and it also shows a decreasing trend with time, corresponding to the subsidence characteristics at Kaifaqu. Therefore, more attention should be paid to this hazard induced by engineering construction besides groundwater withdrawal, as more high-rise buildings are under construction in Tanggu.展开更多
Differential interferometric synthetic aperture radar(DIn SAR), a satellite-based remote sensing technique, has potential application for measuring mine subsidence on a regional scale with high spatial and temporal re...Differential interferometric synthetic aperture radar(DIn SAR), a satellite-based remote sensing technique, has potential application for measuring mine subsidence on a regional scale with high spatial and temporal resolutions. However, the characteristics of synthetic aperture radar(SAR) data and the effectiveness of DIn SAR for subsidence monitoring depend on the radar band(wavelength). This study evaluates the effectiveness of DIn SAR for monitoring subsidence due to longwall mining in central Utah using L-band(24 cm wavelength) SAR data from the advanced land observing satellite(ALOS)and X-band(3 cm wavelength) SAR data from the Terra SAR-X mission. In the Wasatch Plateau region of central Utah, which is characterized by steep terrain and variable ground cover conditions, areas affected by longwall mine subsidence are identifiable using both L-band and X-band DIn SAR.Generally, using L-band data, subsidence magnitudes are measurable. Compared to X-band, L-band data are less affected by signal saturation due to large deformation gradients and by temporal decorrelation due to changes in the surface conditions over time. The L-band data tend to be stable over relatively long periods(months). Short wavelength X-band data are strongly affected by signal saturation and temporal decorrelation, but regions of subsidence are typically identifiable over short periods(days). Additionally,though subsidence magnitudes are difficult to precisely measure in the central Utah region using X-band data, they can often be reasonably estimated.展开更多
Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coa...Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coalfields, which exacerbates the negative subsequences resulted from surface settlement. Therefore, effective approaches to control the ground subsidence are in urgent need for the Chinese coal mining industry. This paper presents a newly developed subsidence control technology: isolated overburden grout injection, including the theory, technique and applications. Relevant procedures such as injection system design, grouting material selection, borehole layout, grout take estimation and injection process design are proposed. The applicability of this technology has been demonstrated through physical modelling, field measurements, and case studies. Since 2009, the technology has been successfully applied to 14 longwall areas in 9 Chinese coal mines. The ultimate surface subsidence factors vary from 0.10 to 0.15. This method has a great potential to be popularized and performed where longwall mining are implemented under villages and ground infrastructures.展开更多
he lithosphere stretching, subsidence and basement thermal history of the Songliao, Yinggehai and Qiongdongnan basins in East China have been investigated by using backstripping technique and stretching models. ...he lithosphere stretching, subsidence and basement thermal history of the Songliao, Yinggehai and Qiongdongnan basins in East China have been investigated by using backstripping technique and stretching models. The subsidence curve of the Songliao basin characterizes a rift basin history evolving from synrift rapid subsidence to postrift thermal subsidence. The calculated stretching factor of the basin is about 1.8 to 2.0 and the horizontal extension is about 55-60 km. The reconstructed subsidence curves of the Qiongdongnan and Yinggehai basins show that the basins underwent several rapid subsidence episodes, which has been interpreted as the result of a multiple stretching of the lithosphere. The total mean stretching factors of the Qiongdongnan and Yinggehai basins, calculated by using a multiple instantaneous stretching model, are about 1.7-1.9 and 2.5-3.0 respectively. The stretching factors of these basins, estimated from subsidence, are consistent with those determined from crustal thinning. The reconstructed thermal histories of these basins are in agreement with the geological observation.展开更多
Based on the integrated study of structure attributions and characteristics of the original basin in combination with lithology and lithofacies, sedimentary provenance analysis and thickness distribution of the Mesozo...Based on the integrated study of structure attributions and characteristics of the original basin in combination with lithology and lithofacies, sedimentary provenance analysis and thickness distribution of the Mesozoic Ordos Basin, it is demonstrated that the depocenters migrated counterclockwise from southeast to the north and then to the southwest from the Middle-Late Triassic to the Early Cretaceous. There were no unified and larger-scale accumulation centers except several small isolated accumulation centers before the Early Cretaceous. The reasons why belts of relatively thick strata were well developed in the western basin in several stages are that this area is near the west boundary of the original Ordos Basin, there was abundant sediment supply and the hydrodynamic effect was strong. Therefore, they stand for local accumulation centers. Until the Early Cretaceous, depocenters, accumulation centers and subsidence centers were superposed as an entity in the southwest part of the Ordos Basin. Up to the end of the Middle Jurassic, there still appeared a paleogeographic and paleostructural higher-in-west and lower-in-east framework in the residual basin to the west of the Yellow River. The depocenters of the Ordos Basin from the Middle-Late Triassic to the Middle Jurassic were superposed consistently. The relatively high thermal maturation of Mesozoic and Paleozoic strata in the depocenters and their neighborhood suggest active deep effects in these areas. Generally, superposition of depocenters in several periods and their consistency with high thermal evolution areas reveal the control of subsidence processes. Therefore, depocenters may represent the positions of the subsidence centers. The subsidence centers (or depocenters) are located in the south of the large-scale cratonic Ordos Basin. This is associated with flexural subsidence of the foreland, resulting from the strong convergence and orogenic activity contemporaneous with the Qinling orogeny.展开更多
Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded...Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e. the rapid uplifting of the the Songpan-Garze fold belt was corresponding to the rapid subsidence of the basin;the Songpan-Garze fold belt has uplifted at a much greater rate than the West Sichuan foeland basin in the last 60 Ma;and (7) the palaeogeothermal gradient was 25℃ /km in the West Sichuan foreland basin.展开更多
Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good underst...Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good understanding for prediction of tunnel deformation and surface settlement during the engineering life of the structure. The deformational behaviour, design of sequential excavation and support of any jointed rock mass are challenging during underground construction. We have raised several commonly assumed issues while performing stability analysis of underground opening at shallow depth. For this purpose, Kainchi-mod Nerchowck twin tunnels(Himachal Pradesh, India) are taken for in-depth analysis of the stability of two asymmetric tunnels to address the influence of topography, twin tunnel dimension and geometry. The host rock encountered during excavation is composed mainly of moderately to highly jointed grey sandstone, maroon sandstone and siltstones. In contrast to equidimensional tunnels where the maximum subsidence is observed vertically above the centreline of the tunnel, the result from the present study shows shifting of the maximum subsidence away from the tunnel centreline. The maximum subsidence of 0.99 mm is observed at 4.54 m left to the escape tunnel centreline whereas the maximum subsidence of 3.14 mm is observed at 8.89 m right to the main tunnel centreline. This shifting clearly indicates the influence of undulating topography and inequidimensional noncircular tunnel.展开更多
The surface deformation prediction system(SDPS) program has been developed as an engineering tool for the calculation of subsidence deformation indices through the implementation of various prediction methods.From bas...The surface deformation prediction system(SDPS) program has been developed as an engineering tool for the calculation of subsidence deformation indices through the implementation of various prediction methods.From basic user-defined input parameters, SDPS can determine subsidence indices, such as mining induced displacements, strains, tilt, etc., at any elevation between the seam and the horizontal or varying surface topography.A fundamental parameter in obtaining reliable ground deformation results is the determination of the edge effect offset.The value assigned to the edge effect offset corresponds to a virtual offsetting of boundary lines delineating the extracted panel to allow for roof cantilevering over the mined-out area.The objective of this paper is to describe the methods implemented in updating the edge effect offset algorithm within SDPS.Using proven geometric equations, the newly developed algorithm provides a more robust calculation of the offset boundary of the extracted panel for simplistic as well as more complex mining geometries.Given that an extracted panel is represented by a closed polyline, the new edge offset algorithm calculates a polyline offset into the extracted panel with respect to the user defined edge effect offset distance.Surface deformations are then calculated using this adjusted panel geometry.The Matlab program was utilized for development and testing of the new edge effect offset algorithm.After completing rigorous testing regimes, the new offset algorithm will be integrated into SDPS further increasing the speed and reliability of the program resulting in a retrospective increase in capability and flexibility.展开更多
基金sponsored by the National Key Research and Development Program of China(Grant No.2020YFC1808102).
文摘Aquifer thermal energy storage(ATES)system has received attention for heating or cooling buildings.However,it is well known that land subsidence becomes a major environmental concern for ATES projects.Yet,the effect of temperature on land subsidence has received practically no attention in the past.This paper presents a thermo-hydro-mechanical(THM)coupled numerical study on an ATES system in Shanghai,China.Four water wells were installed for seasonal heating and cooling of an agriculture greenhouse.The target aquifer at a depth of 74e104.5 m consisted of alternating layers of sand and silty sand and was covered with clay.Groundwater level,temperature,and land subsidence data from 2015 to 2017 were collected using field monitoring instruments.Constrained by data,we constructed a field scale three-dimensional(3D)model using TOUGH(Transport of Unsaturated Groundwater and Heat)and FLAC3D(Fast Lagrangian Analysis of Continua)equipped with a thermo-elastoplastic constitutive model.The effectiveness of the numerical model was validated by field data.The model was used to reproduce groundwater flow,heat transfer,and mechanical responses in porous media over three years and capture the thermo-and pressure-induced land subsidence.The results show that the maximum thermoinduced land subsidence accounts for about 60%of the total subsidence.The thermo-induced subsidence is slightly greater in winter than that in summer,and more pronounced near the cold well area than the hot well area.This study provides some valuable guidelines for controlling land subsidence caused by ATES systems installed in soft soils.
基金Supported by the National Science and Technology Major Project(2017ZX05001)CNPC Science and Technology Project(2021DJ22).
文摘Based on a large number of newly added deep well data in recent years,the subsidence of the Ordos Basin in the Mid-Late Triassic is systematically studied,and it is proposed that the Ordos Basin experienced two important subsidence events during this depositional period.Through contrastive analysis of the two stages of tectonic subsidence,including stratigraphic characteristics,lithology combination,location of catchment area and sedimentary evolution,it is proposed that both of them are responses to the Indosinian Qinling tectonic activity on the edge of the craton basin.The early subsidence occurred in the Chang 10 Member was featured by high amplitude,large debris supply and fast deposition rate,with coarse debris filling and rapid subsidence accompanied by rapid accumulation,resulting in strata thickness increasing from northeast to southwest in wedge-shape.The subsidence center was located in Huanxian–Zhenyuan–Qingyang–Zhengning areas of southwestern basin with the strata thickness of 800–1300 m.The subsidence center deviating from the depocenter developed multiple catchment areas,until then,unified lake basin has not been formed yet.Under the combined action of subsidence and Carnian heavy rainfall event during the deposition period of Chang 7 Member,a large deep-water depression was formed with slow deposition rate,and the subsidence center coincided with the depocenter basically in the Mahuangshan–Huachi–Huangling areas.The deep-water sediments were 120–320 m thick in the subsidence center,characterized by fine grain.There are differences in the mechanism between the two stages of subsidence.The early one was the response to the northward subduction of the MianLüe Ocean and intense depression under compression in Qinling during Mid-Triassic.The later subsidence is controlled by the weak extensional tectonic environment of the post-collision stage during Late Triassic.
文摘Despite the high efficiency of remote sensing methods for rapid and large-scale detection of subsidence phenomena,this technique has limitations such as atmospheric impact and temporal and spatial decorrelation that affect the accuracy of the results.This paper proposes a method based on an artificial neural network to improve the results of monitoring land subsidence due to groundwater overexploitation by radar interferometry in the Aliabad plain(Central Iran).In this regard,vertical ground deformations were monitored over 18 months using the Sentinel-1A SAR images.To model the land subsidence by a multilayer perceptron(MLP)artificial neural network,four parameters,including groundwater level,alluvial thickness,elastic modulus,and transmissivity have been applied.The model's generalizability was assessed using data derived for 144 days.According to the results,the neural network estimates the land subsidence at each ground point with an accuracy of 6.8 mm.A comparison between the predicted and actual values indicated a significant agreement.The MLP model can be used to improve the results of subsidence detection in the study area or other areas with similar characteristics.
基金supported by the National Natural Science Foundation of China(No.52074042)National Key R&D Program of China(No.2018YFC1504802).
文摘When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key strata as a semi-infinite Euler-Bernoulli beam rested on a Winkler foundation with a local subsidence area.The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff.Then,the analytical solutions are verified by the results from experimental tests,FEM and InSAR,respectively.After that,the influence of changing parameters on deflections is studied with sensitivity analysis.The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam.The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam.The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.
基金supported by Geological Research Project of the Construction Management Bureau of the Middle Route of the South to North Water Diversion Project(ZXJ/HN/YW/GC-2020037)。
文摘Groundwater serves as an important water source for residents in and around mining areas.To achieve scientific planning and efficient utilization of water resources in mining areas,it is essential to figure out the chemical formation process and the ground water sulfur cycle that transpire after the coal mining activities.Based on studies of hydrochemistry and D,^(18)O-H_(2)O,^(34)S-SO_(4)isotopes,this study applied principal component analysis,ion ratio and other methods in its attempts to reveal the hydrogeochemical action and sulfur cycle in the subsidence area of Pingyu mining area.The study discovered that,in the studied area,precipitation provides the major supply of groundwater and the main water chemistry effects are dominated by oxidation dissolution of sulfide minerals as well as the dissolution of carbonate and silicate rocks.The sulfate in groundwater primarily originates from oxidation and dissolution of sulfide minerals in coal-bearing strata and human activities.The mixed sulfate formed by the oxidation of sulfide minerals and by human activities continuously recharges the groundwater,promoting the dissolution of carbonate rock and silicate rock in the process.
基金the National Natural Science Foundation of China(grant 31970500 and 31770571)the Excellent Youth Project of the Anhui Natural Science Foundation(grant 2108085Y09)。
文摘In the context of global degradation and loss of natural wetlands,waterbirds have been increasingly using artificial wetlands as alternative habitats.However,waterbirds are facing various threats in these artificial wetlands,due to dramatic environmental changes induced by anthropogenic activities.Exploring the effects of these changes on the temporal dynamics of the waterbird communities can help understand how waterbirds adapt to environmental changes and thus formulate effective management and conservation plans.In this study,we carried out field surveys on waterbirds and environmental factors across 20 subsidence wetlands created by underground coal mining in the Huainan coal mining area in the breeding seasons of 2016 and 2021.We predicted that the waterbird assemblages(i.e.,number of individuals,species richness,Shannon-Wiener diversity,Pielou evenness and species composition) differed between the two years,and that these differences were correlated with the temporal changes in environmental factors.Across the surveyed wetlands,we recorded 26 waterbird species in 2016 and 23 in 2021.For individual wetlands,the number of waterbird individuals and species richness increased by 71.6% and 20.1%,respectively,over the five years,with no changes in Shannon-Wiener diversity and Pielou evenness.The overall increase in the number of bird individuals was mainly caused by an increase in vegetation gleaners and gulls that adapt well to anthropogenic activities.The species composition was significantly different between the two years,which was mainly caused by changes in the number of individuals of dominant species under influence of changes in human activities.For most wetlands,the temporal pairwiseβ-diversities could be explained by species turnover rather than nestedness,probably due to high mobility of waterbird species and dramatic changes in local environments.Our study suggests that waterbird communities could respond to environmental changes in subsidence wetlands,providing important implications for waterbird conservation in human-dominated artificial wetlands.
基金supported by the Natural Science Foundation of Shanxi Province,China (201901D111074,20210302124437).
文摘Subsidence data acquisition methods are crucial to mining subsidence research and an essential component of achieving the goal of environmentally friendly coal mining.The origin and history of the existing methods of field monitoring,calcula-tion,and simulation were introduced.It summarized and analyzed the main applications,flaws and solutions,and improve-ments of these methods.Based on this analysis,the future developing directions of subsidence data acquisition methods were prospected and suggested.The subsidence monitoring methods have evolved from conventional ground monitoring to combined methods involving ground-based,space-based,and air-based measurements.While the conventional methods are mature in technology and reliable in accuracy,emerging remote sensing technologies have obvious advantages in terms of reducing field workload and increasing data coverage.However,these remote sensing methods require further technological development to be more suitable for monitoring mining subsidence.The existing subsidence calculation methods have been applied to various geological and mining conditions,and many improvements have already been made.In the future,more attention should be paid to unifying the studies of calculation methods and mechanical principles.The simulation methods are quite dependent on the similarity of the model to the site conditions and are generally used as an auxiliary data source for subsidence studies.The cross-disciplinary studies between subsidence data acquisition methods and other technologies should be given serious consideration,as they can be expected to lead to breakthroughs in areas such as theories,devices,software,and other aspects.
基金Fundamental Research Funds for the Central Universities(No.B200202015)National Natural Science Foundation of China(No.42004018)Natural Science Foundation of Jiangsu Province(No.BK20190496)。
文摘Coastal subsidence monitoring typically employs Global Navigation Satellite System(GNSS)positioning technology.This method provides information only about subsidence below the station base.Sediments in coastal areas tend to accumulate quickly,and subsidence can change significantly due to compaction and alluvium.Therefore,monitoring subsidence above the base is essential to obtain overall coastal subsidence.A new technology called GNSS-Interferometric Reflectometry(GNSS-IR)has been recently developed,which can utilize multipath effects to monitor reflector height.Since the base of the GNSS station is deep and the base length remains constant,the height changes measured by the GNSS-IR technology can reflect subsidence above the base.Accordingly,this paper employs GNSS-IR technology to measure subsidence changes above the base.Additionally,GNSS positioning technology is used to obtain subsidence changes below the base,and the overall subsidence change is then calculated using both GNSS-IR and GNSS positioning technology.The Mississippi River Delta,known for its significant sediment thickness,was selected as the study area,and data from FSHS,GRIS,and MSIN stations was analyzed.The results demonstrate that GNSS-IR can be used to measure the subsidence rate above the base,and the corrected overall subsidence rate is equivalent to the relative sea level rise rate.
文摘Undergroundgas storage caverns aremonitoredfor environmental safety in termsof equipmentandpotential emissions,particularly methane emissions from the underground and above-ground parts of the storage facility.Periodical measurements of land surface deformations and costly echometric measurements of convergence of individual storage facilities are carried out.The aims of environmental monitoring are:(1)to eliminate potential hazards in the shortest time,(2)assess the overall impact of intensive operation of storage facilities on the environment,(3)developmonitoringmethods relevant to environmental protection,and(4)take actions in case of failure.The paper presents a solution to the problem of determination of the convergence of underground caverns in a salt rock mass based on the results of land surface subsidence measurements carried out using the Gauss-Markov equalization algorithm.Themethod makes it possible for ongoing control of cavern volume convergence after each subsidence measurement on the ground surface and determining the actual impact of the use frequency(injection-mediumconsumption)on the convergence in time.The presentedmethodology is universal and verified on caverns located in a salt rockmass.The Gauss-Markov inversion model is the first used in this area,hence its application is significant.
基金funded by the National Natural Science Foundation of China(Grant Nos.U22B6002,41972217 and 42002219)the Second Tibetan Plateau Scientific Expedition and Research of China(Grant No.2019QZKK0708)。
文摘The India–Eurasia collision has produced a number of Cenozoic deep intracontinental basins,which bear important information for revealing the far-afield responses to the remote collision.Despite their significance,their subsiding mechanism remains the subject of debate,with end-member models attributing it to either orogenic or sedimentary load.In this study,we conduct flexural subsidence modeling with a two-dimensional finite elastic plate model on the Hotan-Mazatagh section along the southern Tarim Basin,which defines a key region in the foreland of the West Kunlun Orogen,along the NW margin of the Tibetan Plateau.The modeling results indicate that the orogenic load of West Kunlun triggers the southern Tarim Basin to subside by up to less than ~6 km,with its impact weakening towards the basin interiors until ~230 km north from the Karakax fault.The sedimentary load,consisting of Cenozoic strata,forces the basin to subside by ~2 to~7 km.In combination with the retreat of the proto-Paratethys Sea and the paleogeographic reorganization of the Tarim Basin,we propose that surface processes,in particular a shift from an exorheic to an endorheic drainage system associated with the consequent thick sedimentary load,played a decisive role in forming deep intracontinental basins in the context of the India-Eurasia collision.
基金support from the National Natural Science Foundation of China(Grant Nos.42072305 and 41831293)。
文摘Long-term field monitoring finds that serious surface subsidence can still occur even if the high strength cemented fill method is adopted.Combining the results of numerical simulations with global position system(GPS)monitoring,we took a typical filling mining mine with a steeply inclined ore body as an example,and explored its ground subsidence mechanism.The results show that the ground subsidence caused by the mining of steep ore body is characterized by two settlement centers and a significantly uneven spatial distribution,which is visibly different from ground subsidence characteristic of the coal mine.The subsidence on the hanging wall is much larger than that on the footwall,and the settlement center tends to move to the hanging wall with the increase of mining depth.The backfill improves the strength and surrounding rock bearing capacity,which leads to a lag of about 3 years of the subsidence.However,under the actions of continuous and repeated mining disturbances,the supporting effect of the backfill can only reduce the amplitude of the deformation,but it cannot prevent the occurrence of settlement.
基金financial supports for this research project by the National Natural Science Foundation of China(Nos.41602308,41967037)supported by Zhejiang Provincial Natural Science Foundation of China under Grant No.LY20E080005+1 种基金funded by National Key Research and Development Projects of China(No.2019YFC507502)Guangxi Science and Technology Plan Project(No.RZ2100000161).
文摘During subway operation,various factors will cause long-term land subsidence,such as the vibration subsidence of foundation soil caused by train vibration load,incomplete consolidation deformation of foundation soil during tunnel construction,dense buildings and structures in the vicinity of the tunnel,and changes in water level in the stratum where the tunnel is located.The monitoring of long-term land subsidence during subway operation in high-density urban areas differs from that in low-density urban construction areas.The former is the gathering point of the entire urban population.There are many complex buildings around the project,busy road traffic,high pedestrian flow,and less vegetation cover.Several existing items requiremonitoring.However,monitoring distance is long,and providing early warning is difficult.This study uses the 2.8 km operation line between Wulin Square station and Ding’an Road station of Hangzhou Subway Line 1 as an example to propose the integrated method of DInSAR-GPS-GIS technology and the key algorithm for long-term land subsidence deformation.Then,it selects multiscene image data to analyze long-termland subsidence of high-density urban areas during subway operation.Results show that long-term land subsidence caused by the operation of Wulin Square station to Ding’an Road station of Hangzhou Subway Line 1 is small,with maximumsubsidence of 30.64 mm,and minimumsubsidence of 11.45 mm,and average subsidence ranging from 19.27 to 21.33 mm.And FLAC3D software was used to verify the monitoring situation,using the geological conditions of the soil in the study area and the tunnel profile to simulate the settlement under vehicle load,and the simulation results tended to be consistent with the monitoring situation.
基金supported by the State Key Development Program for Basic Research of China(Grant No2010CB428803)the Knowledge Innovation Projects of the Chinese Academy of Science(Grant No KZCX2-YW-Q03-02)
文摘Land subsidence is a severe hazard threatening Tanggu, a flat lowland area, and evidences of land subsidence can be seen throughout the city. A new reasonable GPS network was set up in this area from 2008 to 2010. The monitoring data show that land subsidence was serious and two main subsidence cones were obviously formed in the region. One emerged at Hujiayuan, with the maximum rate reaching 60 ram/a, and the influence region enlarged prominently from 2005 to 2010. The other one occurred at Kaifaqu, which became obvious only after 2005, and it showed a decreasing tendency with time. To analyze the causes of ground settlement, a correlation between groundwater withdrawal and land subsidence was firstly made. The results confirmed that over-exploitation of groundwater was the major cause for the severe settlement in Hujiayuan. Meanwhile, the subsidence of Kaifaqu was also related to groundwater withdrawal before 2005. However, the relationship became unconspicuous after 2005. To find the cause of this abnormity, a three-dimensional finite element numerical model, coupled with groundwater flow and subsidence, was built. The simulation results indicate that the subsidence induced by high-rise buildings is serious, but the affected range is limited and it also shows a decreasing trend with time, corresponding to the subsidence characteristics at Kaifaqu. Therefore, more attention should be paid to this hazard induced by engineering construction besides groundwater withdrawal, as more high-rise buildings are under construction in Tanggu.
基金Funding for this research was provided by the National Institute for Occupational Health and Safety(NIOSH)
文摘Differential interferometric synthetic aperture radar(DIn SAR), a satellite-based remote sensing technique, has potential application for measuring mine subsidence on a regional scale with high spatial and temporal resolutions. However, the characteristics of synthetic aperture radar(SAR) data and the effectiveness of DIn SAR for subsidence monitoring depend on the radar band(wavelength). This study evaluates the effectiveness of DIn SAR for monitoring subsidence due to longwall mining in central Utah using L-band(24 cm wavelength) SAR data from the advanced land observing satellite(ALOS)and X-band(3 cm wavelength) SAR data from the Terra SAR-X mission. In the Wasatch Plateau region of central Utah, which is characterized by steep terrain and variable ground cover conditions, areas affected by longwall mine subsidence are identifiable using both L-band and X-band DIn SAR.Generally, using L-band data, subsidence magnitudes are measurable. Compared to X-band, L-band data are less affected by signal saturation due to large deformation gradients and by temporal decorrelation due to changes in the surface conditions over time. The L-band data tend to be stable over relatively long periods(months). Short wavelength X-band data are strongly affected by signal saturation and temporal decorrelation, but regions of subsidence are typically identifiable over short periods(days). Additionally,though subsidence magnitudes are difficult to precisely measure in the central Utah region using X-band data, they can often be reasonably estimated.
基金financial support provided by the National Natural Science Foundation of China(51604258)is greatly appreciated
文摘Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coalfields, which exacerbates the negative subsequences resulted from surface settlement. Therefore, effective approaches to control the ground subsidence are in urgent need for the Chinese coal mining industry. This paper presents a newly developed subsidence control technology: isolated overburden grout injection, including the theory, technique and applications. Relevant procedures such as injection system design, grouting material selection, borehole layout, grout take estimation and injection process design are proposed. The applicability of this technology has been demonstrated through physical modelling, field measurements, and case studies. Since 2009, the technology has been successfully applied to 14 longwall areas in 9 Chinese coal mines. The ultimate surface subsidence factors vary from 0.10 to 0.15. This method has a great potential to be popularized and performed where longwall mining are implemented under villages and ground infrastructures.
文摘he lithosphere stretching, subsidence and basement thermal history of the Songliao, Yinggehai and Qiongdongnan basins in East China have been investigated by using backstripping technique and stretching models. The subsidence curve of the Songliao basin characterizes a rift basin history evolving from synrift rapid subsidence to postrift thermal subsidence. The calculated stretching factor of the basin is about 1.8 to 2.0 and the horizontal extension is about 55-60 km. The reconstructed subsidence curves of the Qiongdongnan and Yinggehai basins show that the basins underwent several rapid subsidence episodes, which has been interpreted as the result of a multiple stretching of the lithosphere. The total mean stretching factors of the Qiongdongnan and Yinggehai basins, calculated by using a multiple instantaneous stretching model, are about 1.7-1.9 and 2.5-3.0 respectively. The stretching factors of these basins, estimated from subsidence, are consistent with those determined from crustal thinning. The reconstructed thermal histories of these basins are in agreement with the geological observation.
基金supported by the National Basic Research Program of China(Grant No.2003CB214600)China Postdoctoral Science Foundation(Grant No.20080431246)the Program for Changjiang scholars and Innovative Research Team in University(Grant No.IRT0559).
文摘Based on the integrated study of structure attributions and characteristics of the original basin in combination with lithology and lithofacies, sedimentary provenance analysis and thickness distribution of the Mesozoic Ordos Basin, it is demonstrated that the depocenters migrated counterclockwise from southeast to the north and then to the southwest from the Middle-Late Triassic to the Early Cretaceous. There were no unified and larger-scale accumulation centers except several small isolated accumulation centers before the Early Cretaceous. The reasons why belts of relatively thick strata were well developed in the western basin in several stages are that this area is near the west boundary of the original Ordos Basin, there was abundant sediment supply and the hydrodynamic effect was strong. Therefore, they stand for local accumulation centers. Until the Early Cretaceous, depocenters, accumulation centers and subsidence centers were superposed as an entity in the southwest part of the Ordos Basin. Up to the end of the Middle Jurassic, there still appeared a paleogeographic and paleostructural higher-in-west and lower-in-east framework in the residual basin to the west of the Yellow River. The depocenters of the Ordos Basin from the Middle-Late Triassic to the Middle Jurassic were superposed consistently. The relatively high thermal maturation of Mesozoic and Paleozoic strata in the depocenters and their neighborhood suggest active deep effects in these areas. Generally, superposition of depocenters in several periods and their consistency with high thermal evolution areas reveal the control of subsidence processes. Therefore, depocenters may represent the positions of the subsidence centers. The subsidence centers (or depocenters) are located in the south of the large-scale cratonic Ordos Basin. This is associated with flexural subsidence of the foreland, resulting from the strong convergence and orogenic activity contemporaneous with the Qinling orogeny.
基金the National Natural Science Foundation of china (poject No. 49070140)
文摘Based on fission track dating of apatite, and measurement of vitrinite reflectance of rock samples from the Longmenshan (Longmen Mountain)area and the West Sichuan foreland basin and computer modelling it is concluded that (l)the Songpan-Garze fold belt has uplifted at least by 3-4 km with an uplift rate of no less than 0.3-0.4 mm/a since 10 Ma B.P.; (2) the Longmenshan thrust nappe belt has uplifted at least by 5-6 km with an uplift rate of more than 0.5- 0.6 mm /a since 10 Ma B.P.; (3) the Longmenshan detachment belt has uplifted by 1 - 2 km at a rate of 0.016-0.032 mm/a since 60 Ma B.P.; (4) the West Sichuan foreland basin has uplifted by 1.7-3 km at a rate of 0.028-0.05 mm/a since 60 Ma B.P.; (5) the uplift rate of the area on the west side of the Beichuan-Yingxiu-Xiaoguanzi fault for the last 10 Ma is 40 times as much as that on its east side; (6) the uplifting of the the Songpan - Garze fold belt and the subsidence of the West Sichuan foreland basin 60 Ma ago exhibit a mirro-image correlation, i.e. the rapid uplifting of the the Songpan-Garze fold belt was corresponding to the rapid subsidence of the basin;the Songpan-Garze fold belt has uplifted at a much greater rate than the West Sichuan foeland basin in the last 60 Ma;and (7) the palaeogeothermal gradient was 25℃ /km in the West Sichuan foreland basin.
基金financial support from Indian Institute of Technology Bombay, India
文摘Tunnelling related hazards are very common in the Himalayan terrain and a number of such instances have been reported. Several twin tunnels are being planned for transportation purposes which will require good understanding for prediction of tunnel deformation and surface settlement during the engineering life of the structure. The deformational behaviour, design of sequential excavation and support of any jointed rock mass are challenging during underground construction. We have raised several commonly assumed issues while performing stability analysis of underground opening at shallow depth. For this purpose, Kainchi-mod Nerchowck twin tunnels(Himachal Pradesh, India) are taken for in-depth analysis of the stability of two asymmetric tunnels to address the influence of topography, twin tunnel dimension and geometry. The host rock encountered during excavation is composed mainly of moderately to highly jointed grey sandstone, maroon sandstone and siltstones. In contrast to equidimensional tunnels where the maximum subsidence is observed vertically above the centreline of the tunnel, the result from the present study shows shifting of the maximum subsidence away from the tunnel centreline. The maximum subsidence of 0.99 mm is observed at 4.54 m left to the escape tunnel centreline whereas the maximum subsidence of 3.14 mm is observed at 8.89 m right to the main tunnel centreline. This shifting clearly indicates the influence of undulating topography and inequidimensional noncircular tunnel.
文摘The surface deformation prediction system(SDPS) program has been developed as an engineering tool for the calculation of subsidence deformation indices through the implementation of various prediction methods.From basic user-defined input parameters, SDPS can determine subsidence indices, such as mining induced displacements, strains, tilt, etc., at any elevation between the seam and the horizontal or varying surface topography.A fundamental parameter in obtaining reliable ground deformation results is the determination of the edge effect offset.The value assigned to the edge effect offset corresponds to a virtual offsetting of boundary lines delineating the extracted panel to allow for roof cantilevering over the mined-out area.The objective of this paper is to describe the methods implemented in updating the edge effect offset algorithm within SDPS.Using proven geometric equations, the newly developed algorithm provides a more robust calculation of the offset boundary of the extracted panel for simplistic as well as more complex mining geometries.Given that an extracted panel is represented by a closed polyline, the new edge offset algorithm calculates a polyline offset into the extracted panel with respect to the user defined edge effect offset distance.Surface deformations are then calculated using this adjusted panel geometry.The Matlab program was utilized for development and testing of the new edge effect offset algorithm.After completing rigorous testing regimes, the new offset algorithm will be integrated into SDPS further increasing the speed and reliability of the program resulting in a retrospective increase in capability and flexibility.