Search

[Display omitted] • GSREI regarding accumulated subsidence, subsidence rate, and elevation. • VEI from population, GDP, construction land, viaduct and metro density. • Risk assessment model and the GSHI index. Urban ground subsidence (GS) causes ground elevation loss, threatens the safe operation of various facilities, and affects surface runoff and hydrological circulation. Therefore, it is vital to monitor the current status of GS to predict and evaluate potential risks to sustainable urban development. Sentinel SAR images from 2019 to 2020 combined with the data from the 2019–2020 Statistical Yearbook were used as data sources. Based on PS-InSAR and SBAS-InSAR, GIS was integrated with the AHP method. A ground subsidence risk evaluation index (REI) suitable for Shanghai was developed regarding three aspects of the amount of accumulated land subsidence (RS obtained): subsidence rate, and terrain elevation. The vulnerability evaluation index (VEI) was established from five aspects: population density, GDP per unit area, the proportion of construction land, viaduct density, and metro density. We introduced the fuzzy AHP method to complete the risk assessment of ground subsidence in Shanghai and obtained the ground subsidence hazard index (GSHI). We used GIS superimposed remote sensing images to visualize the individual evaluation indicators REI , VEI , and GSHI. Using GIS superimposed remote sensing images, various evaluation indicators and GSHI were visualized. Based on the evaluation results, targeted prevention and control recommendations are provided. The results of this research can provide a basis for scientific decision-making regarding Shanghai's territorial spatial planning and socio-economic development. [ABSTRACT FROM AUTHOR]

Geothermal reservoir operations can lead to seismic activity, for instance, due to increased pore pressure, but some observations are difficult to explain by pressure changes alone. Such observations include unexpected, induced events after injection well shut-in when pore pressures are thought to decrease. Here, we analyze induced seismicity up to M L 1.5 and surface deformation in Blue Mountain, Nevada using seismic, geodetic, and hydraulic data between 2016 and 2020. This period is characterized by long-term surface subsidence of up to 1 cm/yr above the reservoir. The long-term deformation is associated with modest seismic activity but also short-lived seismicity spikes during rapid maintenance shutdowns in 2017 and 2018. The seismicity is concentrated within the geothermal reservoir at 0.5 - 2.5 km depth, similar to injection operations. We present a numerical model of abrupt seismicity rate changes during the two shutdowns that explains the observation through short-term poroelastic effects leading to increased Coulomb stressing rates. In contrast, the long-term surface subsidence can be modeled statically by superimposing localized fault slip, and thermal contraction of the reservoir. Our findings demonstrate that poroelastic coupling drives the abrupt increase in seismic activity following well shutdown, while aseismic fault slip and thermal contraction dictate the long-term static deformation. [ABSTRACT FROM AUTHOR]

• Geosynthetic reinforcement to countermeasure sinkhole formation. • Finite-element based analysis on effects of geosynthetic parameters on sinkhole. • Database for machine learning to predict geosynthetic behavior over sinkhole. • Critical values of geogrid parameters are suggested by machine learning models. • Hyper-parameter tuning using Bayesian optimization. The present study describes the results of numerical investigations with implementation of Machine Learning approach to prevent the event of sinkhole formation into the ground by using geosynthetic reinforcement. A series of 2D finite-element analysis were carried out with emphasis on the effects of geosynthetics reinforcement parameters such as geogrid length, stiffness and spacing between the geogrid layers to evaluate the behavior of ground over the sinkhole. Moreover, a database was also generated from the simulations for the application of Machine Learning techniques to predict the behavior as well. The hyperparameters of the Machine Learning models were optimized using Bayesian optimization to enhance the prediction accuracy. The critical values of geogrid reinforcement parameters for maximum reinforcing effect are also suggested. The results indicate the effectiveness of geosynthetic reinforcement to significantly reduce the sinkhole deformations and also the potential of Machine Learning to predict ground subsidence. [ABSTRACT FROM AUTHOR]

Ground subsidence concerns the long-term development of mining areas, and if not addressed effectively, it could gradually evolve into a major issue limiting the future economic development and survival of mining firms and local populations. However, there is unpredictability and uncertainty in the analysis of ground subsidence in mining areas, which is a quantitative and qualitative problem coupled with multiple indicators. By creating a chain relationship between ground subsidence in mining areas, this research provides a spatiotemporal inference model that integrates remote sensing (RS), geographic information system (GIS), and probabilistic map theory. The model uses a dynamic Bayesian framework to integrate the ground subsidence hazard chain in mining areas, standardizes multi-source data using GIS, computes node probabilities, and applies the entropy weight approach to improve model parameters. The Pingshuo mining area in China served as the study area for the model, and the mean values of area under the curve (AUC) and Brier score (BS) of the inferred results were 0.85 and 0.18, respectively, demonstrating that the model had some accuracy and dependability. Further analysis was performed on the impact of weights on the outcomes and the sensitivity of the model to the input nodes. The findings indicated that the spatiotemporal distribution of the results inferred from the model essentially matched the actual circumstance and could offer data assistance for mine safety management. The matching of the subsidence areas was effectively improved by optimizing the model with weights. The accuracy would also grow as the number of input nodes increased. The model proposed in this study is not limited by data, and the structure can be adjusted with the change of disaster chains, which is applicable to the study of multiple uncertainty problems. • We propose a spatiotemporal inference model for ground subsidence in mining areas. • The model integrates RS, GIS and probabilistic graph theory. • The chain process of ground subsidence disaster in the mining area is considered. • The model uses weighted dynamic Bayes as the core algorithm. • Evaluation of model accuracy with AUC and BS. [ABSTRACT FROM AUTHOR]

• 1800 sets of data to study shield tunnelling–ground subsidence relationship. • XGBoost model established for ground subsidence prediction, better than DT and RF. • Nonlinear complex relationships between parameters and ground subsidence analysed. • Key parameters for controlling ground subsidence were identified. • MAE and RMSE used to analyse performance of intelligent prediction model. This study addresses a significant issue related to shield construction, namely the impact of shield construction parameters on ground subsidence. Shield tunnels, owing to their concealed construction, often lead to ground subsidence, causing severe disruptions to ground facilities, potential collapse, and consequent casualties and property loss. Most calculation methods for ground subsidence have a delay, making it difficult to predict ground subsidence in advance based on construction parameters. Therefore, this study collates over 1500 cases of shield construction in China and summarises the impact mechanisms of shield construction on ground subsidence through a detailed study of natural factors, engineering geology, types of structures, and types of construction parameters. Based on the influence law of the data, this study establishes three intelligent prediction methods to forecast ground subsidence. To select the hyperparameters in the models more effectively, a Bayesian optimisation algorithm was utilised. Through a comparative analysis of the models, a subsidence prediction method that is more in line with the construction characteristics and exhibits high accuracy was determined. The findings of this study serve as a valuable resource for predicting ground subsidence resulting from shield construction, enabling timely adjustments to construction parameters and the implementation of preventive measures to mitigate excessive subsidence. [ABSTRACT FROM AUTHOR]

The Gotthard Base Tunnel (GBT), constructed between 2000 and 2011, is a 57 km long and up to 2.5 km deep high-speed railway tunnel located in the Swiss Alps. Significant ground surface displacements reaching about 10 cm were observed during and after the tunnel construction. To gain a better understanding of the causal mechanism of such conspicuous ground deformations, we develop a three-dimensional (3D) fully-coupled hydro-mechanical model to simulate GBT-induced groundwater drainage, stress redistribution, rock mass consolidation, and fault zone deformation at the regional scale. First, we construct a geological model with topographical features, lithological units, and natural faults realistically represented. We constrain the material properties of fault zones and rock masses based on available extensive laboratory testing results and site characterisation datasets. We then simulate the tunnelling process over time, with the resulting coupled hydro-mechanical responses of faulted rock masses well captured and ground surface/subsurface displacements quantitatively analysed. The simulation results in general show a good agreement with the field monitoring data of ground surface displacement, subsurface tunnel settlement, and groundwater inflow into the tunnel. Our model indicates that ground surface displacements originate from GBT-induced water drainage and rock mass consolidation in the deep subsurface. Our results also show that the GBT construction could trigger faults to shear via drainage-induced pressure diffusion and poroelastic stressing. The research findings from our work have important implications for many groundwater drainage-related geoengineering activities such as underground excavation in alpine mountains and fluid withdrawal in subsurface reservoirs. [Display omitted] • 3D simulation captures tunnelling-induced groundwater flow and rock mass deformation. • The simulation explains ground subsidence in crystalline rock during deep tunnelling. • Drainage and consolidation in deep subsurface cause ground surface displacements. • Tunnelling-induced pressure diffusion and poroelastic stressing drive fault movement. [ABSTRACT FROM AUTHOR]

Abstract Using 3-year Sentinel-1 C-band synthetic aperture radar (SAR) data, we observed prominent ground subsidence around the construction site of the Milashan Tunnel, which is on top of the northern Sangri-Cuona Rift (SCR) in southern Tibet. The most deformed area extends ∼7 km in the north-south direction and ∼6 km in the east-west direction, with a peak subsidence rate of over 10 mm/a in the line of sight direction of both the descending and ascending satellites. Aside from the long-term ground subsidence arising directly from underground water outflow and rock excavation, a regional aseismic fault slip episode is also evident. The aseismic slip event began in May 2016 and ended in July 2016. The surface aseismic displacements can be explained by normal faulting with mainly down-dip movement and a modest right-lateral strike-slip component on a nearly north-south trending fault. The aseismic deformation triggered by the Milashan Tunnel construction demonstrates the sensitive response of crustal-scale tectonics to human activity, which poses high seismic hazards for the heavily populated region. [ABSTRACT FROM AUTHOR]

To investigate the compression of granular aquifer induced by fluctuations of pore pressure, series of repeated pore pressure induced loading-unloading tests on specimens made of Ottawa sand mixed with mica were conducted in a K o -triaxial consolidation system. To simulate the stress paths in the field, the vertical displacements of soil specimens were monitored while maintaining a constant total vertical stress and applying sinusoidal fluctuations of pore pressure to specimens under K o conditions. Shakedown theory is applied to interpret the testing data. The paper describes the laboratory setup, test procedure and findings from the test results. The results reveal that a shakedown behavior existed in saturated granular specimens and the accumulated permanent axial strains are 5 to 56 times of the values for conventional, monotonic loading. The finding evidently proves the significance of aquifer compression to ground subsidence due to repeated ground water fluctuations. [ABSTRACT FROM AUTHOR]

The 7.2 Mw Bohol earthquake in 2013 caused significant ground subsidence in some coastal zones northwest of the province, shifting the tidal inundation regime of intertidal habitats. These habitats included more than 500 ha of mangrove plantations particularly in island barangays which substrates are now 85% inundated annually from the 40% pre-quake conditions. Consequently, in less than three years after the quake, the effort of the subsided individual trees to produce new prop roots above the pre-quake height limits was found to be immediate, substantial, and tidally-linked. This prop root response resulted in an increase in the total length and volume by 74% and 39%, respectively, at 2.5-year post-quake relative to the 20-year pre-quake cumulative. With a mean elongation rate of ca. 1.1 m y −1 , some 1.5–2.2 year period was necessary for these new prop roots to reach the substrate, and effectively establish a new equilibrium. The results highlight the role of prop roots on the aeration and stability requirements of Rhizophora , and provide quantitative evidence against the common practice of harvesting prop roots for firewood, charcoal, and other various purposes. The study presents a short-term glimpse of the prop root response of Rhizophora to the otherwise long-term gradual process of sea level rise. [ABSTRACT FROM AUTHOR]

[Display omitted] • Land subsidence is occurring due to groundwater overexploitation in NW India. • Chandigarh city is undergoing a 60 mm/yr subsidence related to rapid urbanization. • Subsidence correlated well with overexploitation, aquifer geology, LULC change. Unsustainable groundwater exploitation often triggers inelastic aquifer compaction, endangering future groundwater potential. The Himalayan piedmont fan regions are undergoing fast urbanization and experiencing rapid groundwater depletion and water table drop. The piedmont fans have laterally varying aquifer geometry with slope-dominated aquifer water flow and experience variable spatiotemporal changes in response to groundwater depletion. We estimated the ground deformation over piedmont fans around Chandigarh (India), a growing urban centre, during 2014–2022 using satellite-based Interferometric Point Target Analysis (IPTA). We used both ascending and descending Differential Interferometric Synthetic Aperture Radar (DInSAR) acquisition modes to derive the vertical ground deformation by combining their line of sight (LOS) velocities. The region is experiencing vertical subsidence up to ∼60 mm/yr with prominent hotspots, where the temporal subsidence is compared with the groundwater cone of depression and urbanization over decades. Comparing the subsidence with the aquifer parameters from the bore wells suggests that the clay confining aquifer level III and semiconfined level II in the distal fan are experiencing the highest subsidence. The stress-strain relationship of these hotspot regions reveals the inelastic compaction of the aquifers producing severe subsidence. The piedmont zones of the Himalayas with identical aquifer geometry and population growth are facing similar challenges, and the combined DInSAR-IPTA and observational groundwater data modeling could provide a robust assessment for effective groundwater-aquifer health monitoring and management. [ABSTRACT FROM AUTHOR]

• Ground subsidence time series from five SAR sensors are fused with Quantile-Quantile Adjustment method. • The deceleration-acceleration-deceleration-rebound process is revealed in Xi'an over the past 30 years. • The ground subsidence is correlated with the urban extension and ground water extraction in Xi'an. • The elastic and inelastic water storage coefficients of the aquifer are calculated. Since the 1960s, Xi'an, China, has suffered from severe ground subsidence due to groundwater extraction and continuous urban construction. During the urbanization process, ground subsidence has threatened and will continue to threaten the stability of the city's infrastructure. Additionally, parts of Xi'an have recently experienced a period of rebound. In this context, we must monitor the spatial and long-term evolution of deformation in Xi'an city. First, archived SAR datasets from 1992 to the present, including ERS1/2, Envisat/ASAR, TerraSAR-X(TSX), ALSO/PALSAR-2(ALOS-2), and Sentinel-1(S1), provided independent historical deformation data in Xi'an city; different SAR interferometry methods can obtain the deformation rates and deformation time-series of the region. Second, to fuse the deformation time-series acquired by different sensors, the Quantile-Quantile Adjustment (QQA) algorithm was used to generate the long-term deformation time-series from October 2003 to May 2021, which has a higher precision than when using the Singular Value Decomposition (SVD) method. Quantitatively, the standard deviation (STD) of the QQA method was only 22 mm at maximum, considerably smaller than the 54 mm obtained with the SVD method. Third, ERS1/2 was linked by the segmental interpolation method to obtain the 30-year deformation time-series of Xi'an, which showed that ground deformation in Xi'an from 1992 to 2021 has experienced a "deceleration-acceleration-deceleration-rebound" process, with a maximum cumulative subsidence of over 2 m. Finally, land use type data and hydraulic head change data were also collected to analyze the deformation information. At the same time, the elastic and inelastic water storage coefficients of the aquifer were calculated by combining the long-term deformation time-series and groundwater head data; the deformation mechanism of the aquifer was analyzed accordingly. [ABSTRACT FROM AUTHOR]

• Pipe-soil interaction due to ground subsidence was experimentally investigated. • Fiber optic strain sensing technique was used for pipe-soil deformation monitoring. • A solution for earth pressure was given accounting for 3D soil arching effects. • An analytical model linking strain measurements to ground movements was proposed. Understanding the pipe-soil interaction is critical for the design and safety assessment of buried pipelines subjected to large differential ground motion. Laboratory model tests were conducted to study the mechanical response of polyvinyl chloride pipes to ground subsidence. The optical frequency domain reflectometry technique was employed to perform distributed strain sensing of the pipe-soil system. An analytical method was proposed to estimate greenfield settlements in terms of fiber optic strain measurements. The pipe-soil interaction mechanism due to ground subsidence was investigated concerning four aspects, i.e., displacement profile of the pipe-soil system, pipe bending, soil arching, and interfacial shearing. Accounting for three-dimensional soil arching effects, a limit equilibrium solution for the earth pressure imposed on the pipe crown was given. This solution was developed from the two-dimensional Terzaghi soil arching theory and was validated based on the measured earth pressures. The feasibility of distributed fiber optic strain sensing technique in monitoring pipe-soil deformation was discussed through the comparison with the data of displacement transducers. In addition, the change in relative pipe-soil stiffness with increasing ground movements was studied based on the bending behavior of the pipe. A simplified method was given for quantifying the axial pipe-soil interaction based on longitudinal strains. This paper presents new inspiration on the intricacies of pipe-soil interaction using high-resolution distributed fiber optic sensing, which can be applied to structural health monitoring and optimum design of buried pipelines. [ABSTRACT FROM AUTHOR]

The groundwater in Tucson, Arizona, is a major source for water supply to human residential areas and agricultural use, and the groundwater extraction causes ground deformation responding to aquifer-system compaction. Using multi-temporal C-band and L-band SAR images from ERS/ENVISAT and ALOS PALSAR satellites, we mapped the ground displacement in Tucson. The InSAR-derived ground displacement based on small baseline subset technique (SBAS) is compared to compaction from extensometers, land subsidence from GPS survey, and groundwater elevation at wells. Tucson is characterized by slow and relatively small subsidence over areas with upper stratigraphic till early 2000s when the groundwater had been extremely depleted and by uplifts in areas where the water level has been recently recovered into the slight increase of water table because of recharge into the aquifer. Our multi-sensor SBAS InSAR-derived vertical displacements enabled to monitor the temporal variability in the spatial extent and magnitude of the ground deformation, suggesting that recent ground subsidence is slowing down and the ground motion in places is stable. Our results can provide scientific basis for sound management of ground water pumping and recharge over the study area. [ABSTRACT FROM AUTHOR]

The geomorphology of the upper reaches of the Yellow River of China is composed by a sequence of fluvial terraces that were formed following phases of neotectonic uplift and subsequent river downward incision. Most of the terraces are covered by thick loess deposits. These quaternary deposits are characterized with high void ratio, vertical joint development, easy to collapse. This is particularly problematic along the terrace edge risers in the high relative relief terrain described here. Substantial water resource development projects, such as large dams and associated irrigation schemes have been developed in this region over the past 60 years. The level terrace surfaces were initially seen as ideal locations supporting migrating populations and irrigated agriculture. However, following the application of irrigation in these previously dry environments, the meta-stable loess collapsed upon wetting, causing widespread subsidence of the plateau levels (more than 2 m) and the build-up of groundwater, resulting in a loss of shearing resistance along the terrace edges and the instigation of large mass movements. Several measures and some academic research have been undertaken in this area, but neither the disastrous effect upon local people nor the evolutionary trend of the hazards have been studied clearly until now. This paper provides a summary of the hazards, their study and management history based on consideration of the extensive literature covering both academic articles and project reports. The paper concludes with a discussion of opportunities for mitigation of these hazards and appropriate management strategies for the irrigated surfaces. [ABSTRACT FROM AUTHOR]

This paper examines the ground subsidence caused by the uniform extraction of fluids from a disc-shaped region located within a poroelastic halfspace. Biot’s theory of poroelasticity is used to examine the problem. The fluid extraction over the circular region at the interior of the poroelastic domain induces time-dependent axisymmetric surface settlements. The theoretical results are also used to examine the accuracy of a multi-physics computational scheme that can be used to examine more complex geological settings. [ABSTRACT FROM AUTHOR]

Methods of SAR interferometry data processing can detect and monitor low-amplitude motion of the earth's surface having the natural or man-made nature. The method of Persistent Scatterers Interferometry (PSI) successfully used for monitoring above mentioned processes in many cities around the world. The results of PSI technologies allow to providing geodynamic zoning of urban areas and identifying the objects exposed to linear deformation - separate objects, extended linear features (e.g. subway). The paper present the results of PSI COSMO-SkyMed data processing for Astana city (capital of Kazakhstan), including the displacement distribution for individual buildings and structures, and areal coverage analysis of surface movements. Data of ENVISAT ASAR images for Almaty city received from ESA grant C1.P15390 “Spatio-temporal analysis of surface displacements in urban areas with high seismic risk by SAR interferometry data”. [ABSTRACT FROM AUTHOR]

Abstract: The Datong Basin is located to the north of the Fenwei Graben Basin, where ground fissures and subsidence are common geological hazards. The Datong Basin is also one of China's main energy bases and is known as “the hometown of coal”. In this study, the small baseline subset InSAR technique was used to process 40 scenes of Envisat ASAR images that cover this area. The magnitude and distribution of subsidence in the Datong Basin were obtained. Additionally, the relationships among the regional land subsidence, ground fissures and fault activity were addressed. The results reveal that Datong ground subsidence is affected by the groundwater exploitation and the nearby faults. The Datong ground fissures are controlled by regional fault activity (e.g., seismic activity) and its interaction with the ground subsidence. Meanwhile, the influence of surface precipitation on ground fissure activity was analyzed. The differential subsidence on both sides of the ground fissures was also studied. [Copyright &y& Elsevier]

Rapid urbanization and population growth in Hanoi city raise the demand for groundwater and the risk of land subsidence. This study is the first to conduct a long-term interferometric synthetic aperture radar (InSAR) analysis with different SAR sensors including ALOS, COSMO-SkyMed and Sentinel-1 to evaluate the spatiotemporal evolution of subsidence in Hanoi between 2007 and 2018. The results show that subsidence in Central Hanoi had been diminishing during these 12 years, while the southern and western outskirts (Ha Dong and Hoai Duc district) had become hot spots with peak rates of ~50 mm/yr. We further model the subsidence time-series with 22 years of piezometric records to estimate hydrogeological properties in the area. The modeling yields a mean consolidation coefficient of 0.56 m2/yr, a value typical for aquitards composed of >90% fine-grain materials. The model also predicts another 0.5–1.3 m of subsidence in Ha Dong by the end of this century. Based on these results, we propose zoning for subsidence susceptibility as the basis for future groundwater management in Hanoi. From a regional perspective, Hanoi is relatively less affected by land subsidence compared to other South East Asian cities due to geotechnical factors including small consolidation coefficients, as well as social factors such as lower population density. • The first long-term InSAR analysis of subsidence in Hanoi. • 1D coupled model yields consolidation coefficient values for the basin in Hanoi. • The model predicts 0.5–1.3 m of future subsidence by the end of this century. • Hanoi is more resistant to subsidence compared to other SEA cities. [ABSTRACT FROM AUTHOR]

We present a novel methodology for integration of multiple InSAR data sets for computation of two dimensional time series of ground deformation. The proposed approach allows combination of SAR data acquired with different acquisition parameters, temporal and spatial sampling and resolution, wavelength and polarization. Produced time series have combined coverage, improved temporal resolution and lower noise level. We apply this methodology for mapping coal mining related ground subsidence and uplift in the Greater Region of Luxembourg along the French–German border. For this we processed 167 Synthetic Aperture Radar ERS-1/2 and ENVISAT images acquired between 1995 and 2009 from one ascending (track 29) and one descending (track 337) tracks and created over five hundred interferograms that were used for time series analysis. Derived vertical and east–west linear deformation rates show with remarkable precision a region of localized ground deformation located above and caused by mining and post-mining activities. Time series of ground deformation display temporal variability: reversal from subsidence to uplift and acceleration of subsidence in the vertical component, and horizontal motion toward the center of the subsidence on the east–west component. InSAR results are validated by leveling measurements collected by the French Geological Survey (BRGM) during 2006–2008. We determined that deformation rate changes are mainly caused by water level variations in the mines. Due to higher temporal and spatial resolution the proposed space-borne method detected a larger number of subsidence and uplift areas in comparison to leveling measurements restricted to annual monitoring of benchmark points along roads. We also identified one deformation region that is not precisely located above the mining sites. Comparison of InSAR measurements with the water levels measured in the mining pits suggest that part of the water that filled the galleries after termination of the dewatering systems may come from this region. Providing that enough SAR data is available, this method opens new opportunities for detecting and locating man-made and natural ground deformation signals with high temporal resolution and precision. [ABSTRACT FROM AUTHOR]

Abstract: Salt rock is internationally accepted as an ideal medium for energy storage. As an energy storage structure, the safety of hydrocarbon storage caverns in salt rock is related to the national economy and to social public security. Risk analysis is an important method of engineering safety evaluation. In this paper the major risks associated with hydrocarbon storage caverns in bedded salt rock are defined. The major risks are classified under the headings of ‘oil and gas leakage’, ‘ground subsidence’, and ‘cavern failure’, and are discussed under these topical titles. The factors leading to the major risks associated with storage caverns are identified by reviewing descriptions of major accidents of salt storage caverns around the world. Fault tree models for the three major risks are established and analyzed. Basic paths of the risk and their occurrence probability ranking are derived. The risk factors which contribute greatly to the risk are identified by calculating the importance degree of all the basic events. Finally, a comprehensive evaluation methodology for major risk loss is generated based on the analytic hierarchy process. This provides a theoretical foundation for the evaluation and prevention of major risks in the construction and operation of storage caverns in bedded salt rock. [Copyright &y& Elsevier]

Abstract: The analysis of the ground movements due to underground mining operation is one of the many important problems of rock mass mechanics. It is difficult to calculate the ground movement due to deep underground mining of iron ore accurately because of the complexity of the problems. In this paper, the application is described of the fuzzy probability measures to the analysis of ground movements. Based on the definition of the fuzzy probability measure, the theories for the two- and three-dimensional problems are developed and are applied to the analysis of ground movements duo to underground deep underground mining of iron ore. [Copyright &y& Elsevier]

Abstract: This paper introduces a new analysis method – stochastic medium technique (SMT) combined with genetic programming (GP) in the prediction of ground subsidence due to tunneling in mountainous areas. The methodology involves the use of stochastic medium theory to generate theory models and to predict ground subsidence due to tunneling in mountainous areas. The parameters in the theory models which are optimized by genetic programming. The use of the integrated methodology is demonstrated via a case study in the prediction of ground subsidence due to tunneling in mountainous areas in Hebei, North China. The results show that the integrated stochastic medium technique – genetic programming (SMT-GP) gives the smallest error on the ground subsidence data when compared to traditional finite element method. The SMT-GP method is expected to provide a significant improvement when the ground subsidence data come from mountainous areas. The agreement of the theoretical results with the field measurements shows that the SMT-GP is satisfactory and the models and SMT-GP method proposed are valid and thus can be effectively used for predicting the ground surface subsidence due to tunneling engineering in mountainous areas and urban areas. [Copyright &y& Elsevier]

Abstract: We constructed hazard maps of ground subsidence around abandoned underground coal mines (AUCMs) in Samcheok City, Korea, using an adaptive neuro-fuzzy inference system (ANFIS) and a geographical information system (GIS). To evaluate the factors related to ground subsidence, a spatial database was constructed from topographic, geologic, mine tunnel, land use, and ground subsidence maps. An attribute database was also constructed from field investigations and reports on existing ground subsidence areas at the study site. Five major factors causing ground subsidence were extracted: (1) depth of drift; (2) distance from drift; (3) slope gradient; (4) geology; and (5) land use. The adaptive ANFIS model with different types of membership functions (MFs) was then applied for ground subsidence hazard mapping in the study area. Two ground subsidence hazard maps were prepared using the different MFs. Finally, the resulting ground subsidence hazard maps were validated using the ground subsidence test data which were not used for training the ANFIS. The validation results showed 95.12% accuracy using the generalized bell-shaped MF model and 94.94% accuracy using the Sigmoidal2 MF model. These accuracy results show that an ANFIS can be an effective tool in ground subsidence hazard mapping. Analysis of ground subsidence with the ANFIS model suggests that quantitative analysis of ground subsidence near AUCMs is possible. [Copyright &y& Elsevier]

Abstract: An overview of the geotechnical aspects of the building damage due to the 2011 Tohoku Pacific Earthquake is presented, based on field reconnaissance made after the earthquake. It is shown that (1) Extensive soil liquefaction occurred along the coast of Tokyo Bay and around the floodplain of the Tonegawa River. Liquefaction was primarily found within the relatively newly reclaimed area, with numerous sand boils and large ground settlements up to 60cm, accompanied by the settlement/tilting of wooden and reinforced concrete buildings supported by spread foundations. The extent and the distribution of the damage were significantly affected by the local soil conditions, including the thickness and the age of the reclaimed fills, the depth to the bedrock or the natural site period, and whether remedial measures had been taken against soil liquefaction, as well as the effects of structure–soil–structure interaction. (2) Numerous houses in Sendai''s hilly residential areas constructed with the cut-and fill method were badly damaged not only by the simple collapse of retaining walls, but also by slope failures in the fills. It was found that most of the slope failures occurred on earth fills. (3) Several pile-supported buildings tilted and settled not only in the Tohoku region, but also on the Kanto plain, implying damage to pile foundations. Ground subsidence with sand boils around those buildings suggests that soil liquefaction might have played a significant role in intensifying the damage. (4) Within Onagawa and Rikuzen-Takata, several steel and reinforced concrete structures were knocked over by tsunami surges, probably after having suffered damage to their pile foundations. Much of the pile damage was concentrated (a) at the joints between pile caps and the piles themselves and (b) near the pile heads. The buildings suffering such damage were old; apparently their pile foundations were not designed to withstand earthquakes. [Copyright &y& Elsevier]

Abstract: This paper gives an overview of the crustal deformation caused by “the 2011 off the Pacific Coast of Tohoku Earthquake” (hereinafter: “the Tohoku Earthquake”) as detected by the GPS Earth Observation Network (GEONET), a GPS continuous observation system operated by the Geospatial Information Authority of Japan (GSI), and of ground deformation resulting from liquefaction triggered by the earthquake motion as determined by a leveling survey. A very large part of the Japanese archipelago was affected by the crustal deformation caused by the mainshock. The subsidence in the Pacific coastal area of the Tohoku region is especially remarkable. Based on a resurvey after the earthquake, the GSI revised the coordinates and heights of survey marks, including the Origin of the Japanese Horizontal Control Network and the Origin of the Japanese Vertical Control Network. We estimated the geometry of the seismogenic fault of the Tohoku Earthquake, as well as a slip model for the boundary between the Pacific Plate and the North American Plate, based on crustal deformation data. Postseismic crustal deformation was also observed by GEONET. Even though the area that coseismicaly subsided is undergoing partial uplift from postseismic deformation, such uplift is not rapid enough to make up for the coseismic subsidence within the next several years. The earthquake caused liquefaction in large parts of the Kanto Region, especially on the Tokyo Bay side and at the lower reaches of the Tone River. Liquefaction was concentrated in areas of land reclamation and former river channels, where it is easy to recognize using time-series geospatial information such as olden topographic maps and olden aerial photographs. To determine the amount of land subsidence (cm) due to liquefaction in Urayasu City, the GSI carried out a leveling survey and compared the differences between pre- and post-earthquake LIDAR survey data with the relative subsidence obtained by leveling. [Copyright &y& Elsevier]

Abstract: Based on a series of experiments in numerical simulation, the model boundary conditions for in situ stress field inversion and excavation are discussed. Study results indicate that roller boundary conditions are reasonable for the in situ stress field inversion before excavation simulation, while, as a closed system, changing the roller boundary conditions to fixed boundary conditions in the subsequent excavation is optimal when the dimensions of the model borders are greater enough than the zone of influence of the excavation. As a case study, a comparative study of the mining-induced ground movement in a steeply dipping mine is carried out in two different stress fields. The results show that the mining-induced ground movement in the high-level tectonic stress field clearly differs from that in the ideal self-weight stress field. Because of the steep occurrence and large thickness of the ore body, the mining-induced ground subsidence exhibits different characteristics at different mining stages in the practical tectonic environment. Further studies elucidate the causes of these differences and clarify the effects of high-level tectonic stresses on rock mass movement and deformation. Finally, based on GPS monitoring results on the ground surface, the current ground subsidence is evaluated and its development trend is predicted. [Copyright &y& Elsevier]

Abstract: Ground subsidence, mainly caused by over exploitation of groundwater and other underground resources, such as oil, gas and coal, occurs in many cities in China. The annual direct loss associated with subsidence across the country is estimated to exceed 100 million US dollar. Interferometric SAR (InSAR) is a powerful tool to map ground deformation at an unprecedented level of spatial detail. It has been widely used to investigate the deformation resulting from earthquakes, volcanoes and subsidence. Repeat-pass InSAR, however, may fail due to impacts of spatial decorrelation, temporal decorrelation and heterogeneous refractivity of atmosphere. In urban areas, a large amount of natural stable radar reflectors exists, such as buildings and engineering structures, at which radar signals can remain coherent during a long time interval. Interferometric point target analysis (IPTA) technique, also known as persistent scatterers (PS) InSAR is based on these reflectors. It overcomes the shortfalls in conventional InSAR. This paper presents a procedure for urban subsidence monitoring with IPTA. Calculation of linear deformation rate and height residual, and the non-linear deformation estimate, respectively, are discussed in detail. Especially, the former is highlighted by a novel and easily implemented 2-dimensional spatial search algorithm. Practically useful solutions that can significantly improve the robustness of IPTA, are recommended. Finally, the proposed procedure is applied to mapping the ground subsidence in Suzhou city, Jiangsu province, China. Thirty-four ERS-1/2 SAR scenes are analyzed, and the deformation information over 38,881 point targets between 1992 and 2000 are generated. The IPTA-derived deformation estimates correspond well with leveling measurements, demonstrating the potential of the proposed subsidence monitoring procedure based on IPTA technique. Two shortcomings of the IPTA-based procedure, e.g., the requirement of large number of SAR images and assumed linear plus non-linear deformation model, are discussed as the topics of further research. [Copyright &y& Elsevier]

Abstract: Integrated techniques were developed, applied, and validated for the analysis of ground subsidence hazards by abandoned coal mines in Samcheok, Korea, using a geographic information system (GIS). Slope, depth of drift, distance from drift, groundwater level, permeability, geology, and land use were extracted or calculated from the digital elevation model, topographic, drift distribution, borehole, geologic, and land use database. By using the constructed spatial database, the relations between the ground subsidence location and seven related factors were identified and quantified by frequency ratio (FR), weights-of-evidence (WOE), logistic regression (LR), and artificial neural network (ANN) models. The relations were used as factor ratings in the overlay analysis to create ground subsidence hazard indices and maps. The four ground subsidence hazard maps were reflected as the new input factors and integrated using FR, WOE, LR, and ANN models to make a hazard map. All of the subsidence hazard maps were validated by comparison with known ground subsidence locations that were not used in the analysis. As a result, the integrated ground subsidence hazard maps used four new subsidence-related input factors that showed a greater accuracy (96.46% for FR, 97.22% for WOE, 97.20% for LR, and 96.70% for ANN, respectively), than the individual ground subsidence maps (95.54% for FR, 94.22% for WOE, 96.89% for LR, and 94.45% for ANN, respectively) using the first seven factors. [Copyright &y& Elsevier]

Abstract: Metal mine with fractured blocky rock mass is much different from coal mine, which shows discontinuity and irregularity, meanwhile large differences also exist in stratum structure, geological condition, ore body shape and mining methods, so the influential factors in metal mines is more complex and volatile. The research on theory and application of ground subsidence has not reached a mature stage at present. So this paper focused on the study of this issue based on neural network with its characteristic that it has fast learning speed and could approach to any non-liner mapping, which are adapted to the complex environment in metal mine. The time series prediction model was established, which is based on the measured data of the roof subsidence in the goaf of metal mine, and the tested sample data were trained and tested by many times. Finally the predicted value of the neural network was compared with the measured value by automatic optical level, which showed that the prediction model achieved good accuracy, and could be accepted in the engineering application. This method could fill the gap of incomplete monitoring data in mine ground subsidence, and provide a reference for production in the metal mine. [Copyright &y& Elsevier]

Abstract: The weights-of-evidence model, one of the Bayesian probability models was applied in evaluating a ground subsidence spatial hazard near abandoned underground coal mines (AUCMs) at Magyori area, Samcheok City in Korea using GIS. Using ground subsidence location and a spatial database containing information such as mining tunnel, borehole, topography, geology, and land use, the weights-of-evidence model was applied to calculate each relevant factor''s rating for the Magyori area in Korea. Seven major factors controlling or related to ground subsidence were determined from the probability analysis of the existing ground subsidence area; depth of drift and distance from drift from the mining tunnel map, slope gradient obtained from the topographical map, ground water level and permeability from borehole data, geology and land use. Tests of conditional independence were performed for the selection of factors, allowing 6 combinations of factors to be analyzed. For the analysis of mapping ground subsidence spatial hazard, the contrast values, W + and W −, of each factor''s rating were overlaid spatially. The results of the analysis were validated using receiver operating characteristic (ROC) with the previous ground subsidence locations. In the case of all factor used, the area under the ROC curve (AUC) showed 0.9667, which corresponds to an accuracy of 96.67%. In the case of the combinations, the case of distance from drift, depth of ground water and land use used, showed the 90.71% (AUC: 0.9071) accuracy which is the best result produced in this analysis. The results can be used for hazard prevention and land-use planning near AUCM areas. [Copyright &y& Elsevier]

Abstract: This paper introduces a new FPM method for prediction of surface subsidence due to inclined coal seam mining. Based on the non-symmetric membership function and the definition of the fuzzy probability measure, the mathematical model for the two-dimensional problem is developed and applied to the analysis of ground subsidence due to underground mining of inclined coal seam. The results of calculation with the new model indicate that the predicted value has good agreement with the measured data. [Copyright &y& Elsevier]

Abstract: The coupling upscaling finite element method is developed for solving the coupling problems of deformation and consolidation of heterogeneous saturated porous media under external loading conditions. The method couples two kinds of fully developed methodologies together, i.e., the numerical techniques developed for calculating the apparent and effective physical properties of the heterogeneous media and the upscaling techniques developed for simulating the fluid flow and mass transport properties in heterogeneous porous media. Equivalent permeability tensors and equivalent elastic modulus tensors are calculated for every coarse grid block in the coarse-scale model of the heterogeneous saturated porous media. Moreover, an oversampling technique is introduced to improve the calculation accuracy of the equivalent elastic modulus tensors. A numerical integration process is performed over the fine mesh within every coarse grid element to capture the small scale information induced by non-uniform scalar field properties such as density, compressibility, etc. Numerical experiments are carried out to examine the accuracy of the developed method. It shows that the numerical results obtained by the coupling upscaling finite element method on the coarse-scale models fit fairly well with the reference solutions obtained by traditional finite element method on the fine-scale models. Moreover, this method gets more accurate coarse-scale results than the previously developed coupling multiscale finite element method for solving this kind of coupling problems though it cannot recover the fine-scale solutions. At the same time, the method developed reduces dramatically the computing effort in both CPU time and memory for solving the transient problems, and therefore more large and computational-demanding coupling problems can be solved by computers. [Copyright &y& Elsevier]

Abstract: The aim of this paper is to detect ground deformation detection in the Rio-Antirio area (Western Greece), between 1992 and 2000. The construction of Rio-Antirio bridge, commenced in year 2000 and completed in 2004 when its operation was launched, demands the study of the historic deformation of the broader area. The Interferometric Point Target Analysis (IPTA) was applied using a dataset of 42 ERS-1 and 2 scenes. Two separate IPTA processing were performed using different reference points for Rio and Antirio respectively. It would not be possible to unwrap the entire scenes using a single reference point because of the presence of the sea water mass between Rio and Antirio. The majority of the point targets show subsidence for the area of Rio ranging between −1.8 mm/year and −6.2 mm/year and for the Antirio area stability or subsidence rates of less than 2 mm/year. Additionally, the deformation history for a number of point targets for both areas was investigated. The detected subsidence of the coastal plains and specially this of Rio could be attributed to the presence of active faults as the area is located over the hanging wall of the fault zone. [Copyright &y& Elsevier]

Abstract: Five microgravity surveys, done between 1972 and 2006, show that in the northern part of the Tauhara geothermal field there were large gravity decreases prior to 1985 associated with the expansion of steam zones resulting from pressure drawdown caused by fluid extraction at Wairakei. Since 1985 there have been gravity increases of up to 240μgal in the northern part of Tauhara, corresponding to a mass increase of about 20Mt. The gravity increases are centred near the unused deep well TH4, and are inferred to result mainly from resaturation of a deep steam zone due to a downflow of water in the well. We suggest that the water entered the well from a confined groundwater aquifer at a known casing break at 393m depth and exited in the region of slotted casing at about 900–1000m depth causing displacement of single-phase liquid upwards into the overlying steam zone. The average downflow rate is estimated to be about 110t/h (30kg/s); however, no downhole measurements in the well have been possible due to casing breaks. Simple modelling of the gravity data suggests the region of resaturation had the form of a cone of impression 150–250m high and extending laterally for 1–2km. Since 1985, gravity changes in the central and southern parts of the Tauhara field have been less than 50μgal, indicating little net mass loss (<2Mt), and hence little effect in this area from the continuing production at Wairakei. The subsidence centred near Crown Road has been attributed to compaction of a thin, elliptical lens of porous, thermally-altered volcanic deposits at shallow depth as a result of a water level decline in the near-surface, steam-heated groundwater aquifer. Gravity data (1994 onwards) at a point near the centre of the subsidence bowl show that, despite ground subsidence of about 0.55m, there have been no significant gravity changes. One explanation for the absence of gravity changes is that the water lost from the near-surface aquifer has drained downwards increasing the saturation in part of a deeper, partly saturated layer. [Copyright &y& Elsevier]

Abstract: A localised ground subsidence anomaly at Crown Road, Taupo, within the Tauhara field of the Wairakei–Tauhara geothermal system, has been subjected to intense scrutiny because of its relatively recent onset and proximity to urban areas. Over a period of 20 years a maximum of 0.63m of subsidence has accumulated. Uncertainties regarding its cause remain, but the evidence now strongly favours a relatively shallow (about 50m depth) origin, compared with other geothermal subsidence bowls at Wairakei, Tauhara and Ohaaki. Declining water levels in a shallow boiling aquifer are considered to be the principal driving mechanism at Crown Road. The source of the subsidence is an anomalously compressible formation of intensely altered ignimbrite found at the base of a buried hydrothermal eruption deposit. This formation is dominated by soft kaolinite and smectite-illite clays of high plasticity and water content, resulting from alteration of highly vesiculated pumice, and is capped by a thin hardpan of silicified pyroclastic material, characterised by vuggy macro-porosity, at about 33m depth. During initiation of the subsidence event, this hardpan may have failed in shear mode around the edges of a buried eruption crater, allowing the overburden to fully load the underlying compressible clays. [Copyright &y& Elsevier]

Abstract: The multiscale finite element method is developed for solving the coupling problems of consolidation of heterogeneous saturated porous media under external loading conditions. Two sets of multiscale base functions are constructed, respectively, for the pressure field of fluid flow and the displacement field of solid skeleton. The coupling problems are then solved with a multiscale numerical procedure in space and time domain. The heterogeneities induced by permeabilities and mechanical parameters of the saturated porous media are both taken into account. Numerical experiments are carried out for different cases in comparison with the standard finite element method. The numerical results show that the coupling multiscale finite element method can be successfully used for solving the complicated coupling problems. It reduces greatly the computing effort in both memory and time for transient problems. [Copyright &y& Elsevier]

Abstract: Several levelling routes in the metropolitan Taipei Basin have been repeatedly conducted during the past decades, mainly in order to monitor the anthropogenic ground subsidence due to massive pumping of groundwater. We analysed the levelling data released from government and investigated the rate of ground level change from 1975 to 2003, which postdate the massive groundwater exploitation in Taipei area. Based on the contour maps created from the levelling data of 406 benchmarks, the overall subsidence rate in the Taipei Basin gradually decreased since 1975, and around 1989 the basin switched to slight uplift throughout a large part of the basin. Three mechanisms are proposed to be responsible for the observed land elevation changes, including shallow soil compaction, deformation within aquifer, and tectonic subsidence. The trend of the ground level change in 1975–2003 essentially demonstrated the effects of natural recharge to previously depleted aquifers, and is explained by the hydro-mechanical coupling of aquifer materials, i.e., elastic rebound, to the rising piezometric level. The rate of shallow soil compaction is estimated about 1–8 mm/yr throughout the basin according primarily to the shallow clay thickness. Asymmetric tectonic subsidence related to the Shanchiao Fault was estimated to be 1.75 mm/yr and 0.9 mm/yr in the western part and the central part of the basin, respectively. By subtracting the components of the soil compaction and tectonic subsidence from the surface land elevation change, the rebound of aquifer strata was estimated to be about 6.7 cm and 16 cm in western margin and Central Taipei, respectively. The amount of rebound is approximately 10% in magnitude comparing to the amount of previous anthropogenic subsidence due to massive groundwater pumping, totally about 2 m. [Copyright &y& Elsevier]

Serious seismic damage is expected owing to the occurrence of lateral displacement following soil liquefaction after a strong earthquake. Currently, there is a need for increased research on the lateral deformation occurring inside a liquefied foundation and its spatial distribution characteristics. Considering the initial geostatic stress of a slightly sloping site, a finite-element model that reflects the liquefaction-induced slippage of the liquefiable site with a slightly inclined ground was designed. According to the results, the steeper the ground slope is, the weaker the soil liquefaction in the slope body will be. As the ground inclination and the intensity of input ground motion vary, the lateral slippage of the liquefiable soil layer transforms from the liquefaction-induced slipping along a single sliding surface to that along multiple sliding surfaces. The dominant lateral displacement of liquefiable soil layers in the slope body changes as well, from liquefaction-induced slippage of soil to largely large single-direction accumulated shear deformation of softening soil, as a result of the drastically reduced intensity of the liquefiable soil. In addition, a similar linear relationship is found among the maximum lateral displacement, the ground settlement near the slope crest, and the ground uplift near the slope foot. ● An improved constitutive model used for the large deformation of liquefied soil. ● A FEM model designed for the slippage of the inclined liquefiable site. ● The distribution characteristics of soil liquefaction in the slope are proved. ● The mechanism for inducing the ground lateral displacement were investigated. [ABSTRACT FROM AUTHOR]

A complex resistivity (CR) survey was used to evaluate ground reinforcement following the injection of mortar, which is rich in clay minerals known to show strong induced polarization effects. CR surveys were used to determine the distribution of injected mortar along six survey lines parallel to a road in a karst area in Yongweol-ri, Muan-gun, Korea, which had suffered from ground subsidence and had been reinforced. CR data were collected at 0.125 Hz along each survey line and inverted to find two phase anomalies. We show that the phase anomalies indicate the accumulation of injected mortar. This interpretation was confirmed according to the amount of mortar injected at each borehole, and the time-lapse (TL) direct current data obtained during the reinforcement process. Furthermore, the CR data were three-dimensionally inverted, with the results compared to those of a two-dimensional (2-D) inversion, to demonstrate that 3-D inversion can provide more detailed information than 2-D analysis. A CR survey is an effective tool to determine the distribution of injected mortar. • Novel use of a complex resistivity survey to evaluate ground reinforcements. • Cement-based mortar induced polarization effects due to the presence of clay. • Injected mortar produces strong phase anomalies. • Three-dimensional complex resistivity analysis can be used to determine the distribution of injected mortar. [ABSTRACT FROM AUTHOR]

A sudden increase of groundwater inflow of 670 tons a day was experienced during tunneling in a limestone formation at around 53 m below the ground surface. The limestone cavities were expected to be located at 5–10 m or more above the tunnel crown in geotechnical exploration. However, limestone cavity network was encountered at the tunnel depth, and large groundwater inflow was experienced. Because of the excessive groundwater inflow into the tunnel, the groundwater level dropped to GL-32 m from the original level of GL-16 m, and consequently maximum of 23 mm of ground settlement and damage of adjacent structures took place. In this study the change of groundwater regime during tunneling in limestone area containing cavity network was analyzed through 3-dimensional numerical analysis, and the mechanism of groundwater level drawdown followed by ground subsidence was analyzed by comparing measurements and numerical analysis results. And also the analytical solution for determining the range of cutoff grouting was proposed to minimize groundwater inflow during excavation in a fractured zone. [ABSTRACT FROM AUTHOR]