During the intense debates between fixism and mobilism,Chinese geologist J.S.Lee published“The Fundamental Cause of Evolution of the Earth’s Surface Features”in 1926 in the Bulletin of the Geological Society of Chi...During the intense debates between fixism and mobilism,Chinese geologist J.S.Lee published“The Fundamental Cause of Evolution of the Earth’s Surface Features”in 1926 in the Bulletin of the Geological Society of China,supporting mobilism.He attributed continental movements to the variations of the Earth’s rotation speed:when the rotation speed increases,it generates forces that compel the continents and seawater to move horizontally from the poles toward the equator and vice versa.It was on this idea that his Geomechanics was established in the following decades.展开更多
Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surroundi...Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surrounding the cross-fault tunnel with poor geological conditions has been chosen for the study.The support capacity of 2^(nd) Generation-Negative Poisson’s Ratio(2G-NPR)bolt in an active fault tunnel has been carried out on the basis of relevant results obtained from the geomechanical model test and numerical investigations of failure model for existing unsupported fault tunnel.The investigation shows that surrounding rock of the tunnel is prone to shear deformation and crack formation along the fault,as a result,the rock mass on the upper part of the fault slips as a whole.Furthermore,small-scale deformation and loss of blocks are observed around the tunnel;however,the 2G-NPR bolt support is found to be helpful in keeping the overall tunnel intact without any damage and instability.Due to the blocking effect of fault,the stress of the surrounding rock on the upper and lower parts of the fault is significantly different,and the stress at the left shoulder of the tunnel is greater than that at the right shoulder.The asymmetrical arrangement of 2G-NPR bolts can effectively control the asymmetric deformation and instability of the surrounding rock.The present numerical scheme is in good agreement with the model test results,and can reasonably reflect the stress and displacement characteristics of the surrounding rock of the tunnel.In comparison to unsupported and ordinary PR(Poisson’s Ratio)bolt support,2G-NPR bolt can effectively limit the fault slip and control the stability of the surrounding rock of the fault tunnel.The research findings may serve as a guideline for the use of 2G-NPR bolts in fault tunnel support engineering.展开更多
Geological characteristics,geomechanical behavior and hydraulic fracture propagation mechanism in the Marcellus shale gas play are analyzed and compared with China’s Fuling shale play.Successful experiences in hydrau...Geological characteristics,geomechanical behavior and hydraulic fracture propagation mechanism in the Marcellus shale gas play are analyzed and compared with China’s Fuling shale play.Successful experiences in hydraulic fracturing and shale gas development in the Marcellus shale gas play are summarized,which might be applicable in other shale plays.The main factors contributing to the successful development of the Marcellus shale gas play include adoption of advanced drilling and completion technologies,increases of hydraulic fracturing stages,proppant concentration and fluid injection volume.The geological and geomechanical mechanisms related to those technologies are analyzed,particularly the in-situ stress impacts on hydraulic fracturing.The minimum horizontal stress controls where the fractures are initiated,and the maximum horizontal stress dominates the direction of the hydraulic fracture propagation.Hydraulic fracturing performed in the shale reservoir normally has no stress barriers in most cases because the shale has a high minimum horizontal stress,inducing hydraulic fractures propagating beyond the reservoir zone,resulting in inefficient stimulation.This is a common problem in shale plays,and its mechanism is studied in the paper.It is also found that the on-azimuth well has a higher productivity than the off-azimuth well,because shear fractures are created in the off-azimuth well,causing main fractures to kink and increasing fracture tortuosity and friction.The Fuling shale gas play has a markedly higher minimum horizontal stress and much smaller horizontal stress difference.The high minimum horizontal stress causes a much higher formation breakdown pressure;therefore,hydraulic fracturing in the Fuling shale gas play needs a higher treatment pressure,which implies higher difficulty in fracture propagation.The small difference in the two horizontal stresses in the Fuling shale gas play generates shorter and more complex hydraulic fractures,because hydraulic fractures in this case are prone to curve to preexisting fractures.To overcome these difficulties,we recommend reducing well spacing and increasing proppant concentration to increase gas productivity for the Fuling shale gas development.展开更多
The solution of a slope stability problem can be approached by its least upper-bound and maximum lower-bound with high accuracy. The limit equilibrium methods that employ vertical slices imply a lower bound of the fac...The solution of a slope stability problem can be approached by its least upper-bound and maximum lower-bound with high accuracy. The limit equilibrium methods that employ vertical slices imply a lower bound of the factor of safety. It has been successfully extended to the area of active earth pressure analysis that accounts for different input of locations of earth pressure applications. Those methods that employ slices with inclined interfaces give an upper-bound approach to the stability analysis. It enjoys a sound mechanical background and is able to provide accurate solutions of soil plasticity. It has been successfully extended to the area of bearing capacity analysis in which various empirical coefficients are no longer necessary. The 3D upper- and lower-bound methods under this framework have been made possible and show great potential for solving various engineering problems.展开更多
A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical be...A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical behaviour of the rocks and of the rock mass (deformation and strength parameters), is presented. Its aim is to give geologists as well as engineers the opportunity to compare phenomena in the field and phenomena belonging to particular mechanisms and to find the mechanism occurring. The presented catalogue of initial landslide mechanisms only comprises the mechanisms having a clearly defined mechanical model that can be divided into empirical relations and into mechanical models, as well as an overview of run out models, which can be divided into empirical relations and into mechanical models.展开更多
Recently, a four-dimensional lattice spring model(4D-LSM) was developed to overcome the Poisson’s ratio limitation of the classical LSM by introducing the fourth-dimensional spatial interaction. In this work, some as...Recently, a four-dimensional lattice spring model(4D-LSM) was developed to overcome the Poisson’s ratio limitation of the classical LSM by introducing the fourth-dimensional spatial interaction. In this work, some aspects of the 4D-LSM on solving problems in geomechanics are investigated, such as the ability to reproduce elastic properties of geomaterials, the capability of solving heterogeneous problems,the accuracy on modelling stress wave propagation, the ability to solve dynamic fracturing and the parallel computational efficiency. Our results indicate that the 4D-LSM is promising to deal with problems in geomechanics.展开更多
Fiber-optic distributed strain sensing(FO-DSS)has been successful in monitoring strain changes along horizontal wellbores in hydraulically fractured reservoirs.However,the mechanism driving the various FO-DSS response...Fiber-optic distributed strain sensing(FO-DSS)has been successful in monitoring strain changes along horizontal wellbores in hydraulically fractured reservoirs.However,the mechanism driving the various FO-DSS responses associated with near-wellbore hydraulic fracture properties is still unclear.To address this knowledge gap,we use coupled wellbore-reservoir-geomechanics simulations to study measured strain-change behavior and infer hydraulic fracture characteristics.The crossflow among fractures is captured through explicit modeling of the transient wellbore flow.In addition,local grid refinement is applied to accurately capture strain changes along the fiber.A Base Case model was designed with four fractures of varying properties,simulating strain change signals when the production well is shut-in for 10 d after 240 d of production and reopened for 2 d.Strain-pressure plots for different fracture clusters were used to gain insights into inferring fracture properties using DSS data.When comparing the model with and without the wellbore,distinct strain change signals were observed,emphasizing the importance of incorporating the wellbore in FO-DSS modeling.The effects of fracture spacing and matrix permeability on strain change signals were thoroughly investigated.The results of our numerical study can improve the understanding of the relation between DSS signals and fracture hydraulic properties,thus maximizing the value of the dataset for fracture diagnostics and characterization.展开更多
Injection of large volumes of carbon dioxide(CO) for the purposes of greenhouse-gas emissions reduction has the potential to induce earthquakes.Operators of proposed projects must therefore take steps to reduce the ri...Injection of large volumes of carbon dioxide(CO) for the purposes of greenhouse-gas emissions reduction has the potential to induce earthquakes.Operators of proposed projects must therefore take steps to reduce the risks posed by this induced seismicity.In this paper,we examine the causes of injection-induced seismicity(IIS),and how it should be monitored and modelled,and thereby mitigated.Many US case studies are found where fluids are injected into layers that are in close proximity to crystalline basement rocks.We investigate this issue further by comparing injection and seismicity in two areas where oilfield wastewater is injected in significant volumes:Oklahoma,where fluids are injected into a basal layer,and Saskatchewan,where fluids are injected into a much shallower layer.We suggest that the different induced seismicity responses in these two areas are at least in part due to these different injection depths.We go on to outline two different approaches for modelling IIS:a statistics based approach and a physical,numerical modelling based approach.Both modelling types have advantages and disadvantages,but share a need to be calibrated with good quality seismic monitoring data if they are to be used with any degree of reliability.We therefore encourage the use of seismic monitoring networks at all future carbon capture and storage(CCS) sites.展开更多
Taking the theory of mixture as a basic .framework, the paper merges the primesof rational mechanics irreivrsible thermodynamics and soil meehanics into an organicsystem and proposes an axiomatics of geomechanics .The...Taking the theory of mixture as a basic .framework, the paper merges the primesof rational mechanics irreivrsible thermodynamics and soil meehanics into an organicsystem and proposes an axiomatics of geomechanics .The theoretical system consistsof 5 basis laws and 8 constitutive principles .and it erects a bridge across the gapbetween the pure theory of mechanics and engineering practice .展开更多
Reservoir Geomechanics is a very comprehensive book spanning all aspects of stress within the accessible earth.The topics presented are interdisciplinary and encompass the fields of rock mechanics,tectonophysics,struc...Reservoir Geomechanics is a very comprehensive book spanning all aspects of stress within the accessible earth.The topics presented are interdisciplinary and encompass the fields of rock mechanics,tectonophysics,structural geology and petroleum engineering.It is divided into three parts in which the basic principles,stress indicators and measuring techniques,and their applications in addressing the problems of wellbore stability,permeability of critically stressed faults and reservoir depletion in sedimentary basins are presented and discussed in detail along with some case studies.展开更多
The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgr...The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgrade are even more paramount in the railroad track structure performance.A geomechanics classification for subgrade is proposed coupling the stiffness(resilient modulus)and permanent deformation behaviour evaluated by means of repeated triaxial loading tests.This classification covers from fine-to coarse-grained soils,grouped by UIC and ASTM.For this achievement,we first summarize the main models for estimating resilient modulus and permanent deformation,including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters.This is followed by the procedure required to arrive at the geomechanical classification and rating,as well as a discussion of the influence of environmental factors.This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.展开更多
Comprehensive mechanized top-coal caving mining is one of the efficient mining methods in coal mines.However,the goaf formed by comprehensive mechanized top-coal caving mining is high,and the goaf roof collapse will c...Comprehensive mechanized top-coal caving mining is one of the efficient mining methods in coal mines.However,the goaf formed by comprehensive mechanized top-coal caving mining is high,and the goaf roof collapse will cause strong dynamic pressure disturbance,especially the collapse of thick hard roof.Strong dynamic pressure disturbance has an influence on the stability of the roadway,which can lead to large deformation.In order to solve the above problem,a comprehensive pressure releasing and constant resistance energy absorbing control method is proposed.Comprehensive pressure releasing can change the roadway roof structure and cut off the stress transfer between goaf and roadway,which can improve the stress environment of the roadway.The constant resistance energy absorbing(CREA)anchor cable can absorb the energy of surrounding rock deformation and resist the impact load of gangue collapse,so as to ensure the stability of roadway disturbed by strong dynamic pressure.A three-dimensional geomechanics model test is carried out,based on the roadway disturbed by strong dynamic pressure of the extra-large coal mine in western China,to verify the control effect of the new control method.The stress and displacement evolution laws of the roadway with traditional control method and new control method are analyzed.The pressure releasing and energy absorbing control mechanism of the new control method is clarified.The geomechanics model test results show that the new control method can increase the range of low stress zone by 150%and reduce the average stress and the displacement by 34.7%and 67.8%respectively,compared with the traditional control method.The filed application results show that the new control method can reduce the roadway surrounding rock displacement by 67.4%compared with the traditional control method.It shows that the new control method can effectively control the displacement of the roadway disturbed by strong dynamic pressure and ensure that the roadway meets the safety requirements.On this basis,the engineering suggestions for large deformation control of this kind of roadway are put forward.The new control method can provide a control idea for the roadway disturbed by strong dynamic pressure.展开更多
The paper considers the methodology for a comprehensive analysis of the stability of an open pit-dump system,using limit equilibrium(LEM)and finite element(FEM)methods in the Russian CAE(computer-aided engineering)sof...The paper considers the methodology for a comprehensive analysis of the stability of an open pit-dump system,using limit equilibrium(LEM)and finite element(FEM)methods in the Russian CAE(computer-aided engineering)software Fidesys.It briefly highlights the issues of comparing limit equilibrium methods using the VNIMI(Research Institute of Geomechanics and Mine Surveying-Intersectoral Scientific Center"VNIMI")methodology and a specialized software product with numerical methods.The main focus of this study is to compare the results of the stability analysis in the volumetric model of the open pit-dump system using limit equilibrium and finite element methods in the CAE software Fidesys.It was found that,when modeling the combined operation of an open pit-dump system in complex terrain,both methods should be used,as each has its own advantages.The finite element method,for instance,has certain features that are not present in the calculations using the limit equilibrium approach.As a key scientific contribution,this paper introduces an automation program for calculating the stability of open-pit walls using the limit equilibrium method in CAE Fidesys,which was not previously integrated in the original software.The calculations performed with the use of this newly developed module were compared to those obtained from other widely used software solutions available on the market.The findings demonstrate a remarkable level of convergence in the calculation results for all relevant parameters,including the safety factor,localization,instability type,and deformation.The proposed approach i mproves the accuracy of calculati ons and ensures consistency between the higher stress design zones and the actual deformation and fracture patterns.It also enhances the ability to predict the behavior of rock mass when calculating stability parameters for facilities,both during operation and desi gn.展开更多
Fracture-cave reservoirs are widely developed in carbonate formations and account for over 55%of global petroleum reserves.The productivity,formation mechanisms,and in-situ stress states of these reservoirs,characteri...Fracture-cave reservoirs are widely developed in carbonate formations and account for over 55%of global petroleum reserves.The productivity,formation mechanisms,and in-situ stress states of these reservoirs,characterized by fault-fracture-cave systems,are inherently interconnected.However,solely relying on geometric characterizations of natural fractures and cavities fails to meet the demands of modern petroleum exploration and development,particularly due to their complex structures,significant spatial heterogeneity,and strong geomechanical anisotropy.A critical challenge remains:how to safely and efficiently drill high-yield wells through highly fractured and cavernous zones while mitigating drilling risks.Consequently,establishing geomechanical models for fracture-cave reservoirs and predicting 3D stress fields are imperative for well trajectory optimization and reservoir reconstruction.This study integrates seismic interpretations of strike-slip faults with multi-attribute inversions of fracture-cave reservoirs.Using ANSYS 21.0 software,a homogeneous geomechanical model was constructed based on finely characterized geometries of fracturecave systems.Rock mechanics parameters,interpreted from conventional logging data and seismic attributes,were inverted to generate 3D distributions.These parameters were subsequently incorporated into the homogeneous model to develop a heterogeneous geomechanical framework.In-situ stress orientations were calibrated using drilling-induced fracture data,enabling predictions of the contemporary stress field in complex fracture-cave reservoirs.The methodology was validated in the Yueman Block of the Tarim Basin’s deep carbonate reservoir.Results revealed stress distribution patterns and key controlling factors,which were applied to evaluate wellbore stability,fracture reactivation risks,and optimize well trajectories.This approach provides a technical foundation for safe and efficient exploration-development of fracture-cave reservoirs worldwide.展开更多
The feasibility of constructing shallow foundations on saturated sands remains uncertain.Seismic design standards simply stipulate that geotechnical investigations for a shallow foundation on such soils shall be condu...The feasibility of constructing shallow foundations on saturated sands remains uncertain.Seismic design standards simply stipulate that geotechnical investigations for a shallow foundation on such soils shall be conducted to mitigate the effects of the liquefaction hazard.This study investigates the seismic behavior of strip foundations on typical two-layered soil profiles-a natural loose sand layer supported by a dense sand layer.Coupled nonlinear dynamic analyses have been conducted to calculate response parameters,including seismic settlement,the acceleration response on the ground surface,and excess pore pressure beneath strip foundations.A novel liquefaction potential index(LPI_(footing)),based on excess pore pressure ratios across a given region of soil mass beneath footings is introduced to classify liquefaction severity into three distinct levels:minor,moderate,and severe.To validate the proposed LPI_(footing),the foundation settlement is evaluated for the different liquefaction potential classes.A classification tree model has been grown to predict liquefaction susceptibility,utilizing various input variables,including earthquake intensity on the ground surface,foundation pressure,sand permeability,and top layer thickness.Moreover,a nonlinear regression function has been established to map LPI_(footing) in relation to these input predictors.The models have been constructed using a substantial dataset comprising 13,824 excess pore pressure ratio time histories.The performance of the developed models has been examined using various methods,including the 10-fold cross-validation method.The predictive capability of the tree also has been validated through existing experimental studies.The results indicate that the classification tree is not only interpretable but also highly predictive,with a testing accuracy level of 78.1%.The decision tree provides valuable insights for engineers assessing liquefaction potential beneath strip foundations.展开更多
Tensile strength is a crucial parameter for assessing rock stability and fracture characteristics,which play a significant role in the prediction and engineering design of geohazards.However,fault slip activity can we...Tensile strength is a crucial parameter for assessing rock stability and fracture characteristics,which play a significant role in the prediction and engineering design of geohazards.However,fault slip activity can weaken the strength of the surrounding rock mass,thereby influencing its mechanical behavior and failure mode.This study investigates the spatial variation of the tensile strength(σ_(t)),compressive strength(σ_(c)),P-wave velocity(V_(p)),and acoustic emission(AE)characteristics at varying distances from the Xianshuihe Fault zone(XSHF),focusing on three representative profiles.The results show that theσ_(t),σ_(c),and V_(p)significantly decrease near the fault(0–5km).Specifically,the relative change rates ofσ_(t),σ_(c),and V_(p)at approximately 5km from the fault are 1.55–1.8 times,1.22–1.86 times,and 1.02–1.25 times greater,respectively,compared to the near-fault zone.As the distance from the fault increases(10–20km),the rock integrity improves,and the mechanical properties recover.AE monitoring reveals increased microcracks near the fault,with higher b-value and dominant tensile failure modes.Further from the fault,the rock exhibits increased brittleness,and tensile cracking becomes more prevalent.Overall,the mechanical parameters and AE characteristics demonstrate predictable spatial variation with distance,providing valuable insights for identifying stress concentration zones and potential geohazards.展开更多
In regions characterized with great mining depths,complex topography,and intense geological activities,solely relying on lateral pressure coefficients or linear boundary conditions for predicting the in situ stress fi...In regions characterized with great mining depths,complex topography,and intense geological activities,solely relying on lateral pressure coefficients or linear boundary conditions for predicting the in situ stress field of rock bodies can induce substantial deviations and limitations.This study focuses on a typical karst area in Southwest Guizhou,China as its research background.It employs a hybrid approach integrating machine learning,numerical simulations,and field experiments to develop an optimization algorithm for nonlinear prediction of the complex three-dimensional(3D)in situ stress fields.Through collecting and fitting analysis of in situ stress measurement data from the karst region,the distributions of in situ stresses with depth were identified with nonlinear boundary conditions.A prediction model for in situ stress was then established based on artificial neural network(ANN)and genetic algorithm(GA)approach,validated in the typical karst landscape mine,Jinfeng Gold Mine.The results demonstrate that the model's predictions align well with actual measurements,showcasing consistency and regularity.Specifically,the error between the predicted and actual values of the maximum horizontal principal stress was the smallest,with an absolute error 0.01-3 MPa and a relative error of 0.04-15.31%.This model accurately and effectively predicts in situ stresses in complex geological areas.展开更多
Underground engineering in extreme environments necessitates understanding rock mechanical behavior under coupled high-temperature and dynamic loading conditions.This study presents an innovative multi-scale cross-pla...Underground engineering in extreme environments necessitates understanding rock mechanical behavior under coupled high-temperature and dynamic loading conditions.This study presents an innovative multi-scale cross-platform PFC-FDEM coupling methodology that bridges microscopic thermal damage mechanisms with macroscopic dynamic fracture responses.The breakthrough coupling framework introduces:(1)bidirectional information transfer protocols enabling seamless integration between PFC’s particle-scale thermal damage characterization and FDEM’s continuum-scale fracture propagation,(2)multi-physics mapping algorithms that preserve crack network geometric invariants during scale transitions,and(3)cross-platform cohesive zone implementations for accurate SHTB dynamic loading simulation.The coupled approach reveals distinct three-stage crack evolution characteristics with temperature-dependent density following an exponential model.High-temperature exposure significantly reduces dynamic strength ratio(60%at 800℃)and diminishes strain-rate sensitivity,with dynamic increase factor decreasing from 1.0 to 2.2(25℃)to 1.0-1.3(800℃).Critically,the coupling methodology captures fundamental energy redistribution mechanisms:thermal crack networks alter elastic energy proportion from 75%to 35%while increasing fracture energy from 5%to 30%.Numerical predictions demonstrate excellent experimental agreement(±8%peak stress-strain errors),validating the PFC-FDEM coupling accuracy.This integrated framework provides essential computational tools for predicting complex thermal-mechanical rock behavior in underground engineering applications.展开更多
文摘During the intense debates between fixism and mobilism,Chinese geologist J.S.Lee published“The Fundamental Cause of Evolution of the Earth’s Surface Features”in 1926 in the Bulletin of the Geological Society of China,supporting mobilism.He attributed continental movements to the variations of the Earth’s rotation speed:when the rotation speed increases,it generates forces that compel the continents and seawater to move horizontally from the poles toward the equator and vice versa.It was on this idea that his Geomechanics was established in the following decades.
基金supported by the National Natural Science Foundation of China(NSFC)(41941018)the Program of China Scholarship Council(202106430031)。
文摘Active faults are a common adverse geological phenomenon that can occur during tunnel excavation and has a very negative impact on the construction and operation of the tunnel.In this paper,the grade IV rock surrounding the cross-fault tunnel with poor geological conditions has been chosen for the study.The support capacity of 2^(nd) Generation-Negative Poisson’s Ratio(2G-NPR)bolt in an active fault tunnel has been carried out on the basis of relevant results obtained from the geomechanical model test and numerical investigations of failure model for existing unsupported fault tunnel.The investigation shows that surrounding rock of the tunnel is prone to shear deformation and crack formation along the fault,as a result,the rock mass on the upper part of the fault slips as a whole.Furthermore,small-scale deformation and loss of blocks are observed around the tunnel;however,the 2G-NPR bolt support is found to be helpful in keeping the overall tunnel intact without any damage and instability.Due to the blocking effect of fault,the stress of the surrounding rock on the upper and lower parts of the fault is significantly different,and the stress at the left shoulder of the tunnel is greater than that at the right shoulder.The asymmetrical arrangement of 2G-NPR bolts can effectively control the asymmetric deformation and instability of the surrounding rock.The present numerical scheme is in good agreement with the model test results,and can reasonably reflect the stress and displacement characteristics of the surrounding rock of the tunnel.In comparison to unsupported and ordinary PR(Poisson’s Ratio)bolt support,2G-NPR bolt can effectively limit the fault slip and control the stability of the surrounding rock of the fault tunnel.The research findings may serve as a guideline for the use of 2G-NPR bolts in fault tunnel support engineering.
文摘Geological characteristics,geomechanical behavior and hydraulic fracture propagation mechanism in the Marcellus shale gas play are analyzed and compared with China’s Fuling shale play.Successful experiences in hydraulic fracturing and shale gas development in the Marcellus shale gas play are summarized,which might be applicable in other shale plays.The main factors contributing to the successful development of the Marcellus shale gas play include adoption of advanced drilling and completion technologies,increases of hydraulic fracturing stages,proppant concentration and fluid injection volume.The geological and geomechanical mechanisms related to those technologies are analyzed,particularly the in-situ stress impacts on hydraulic fracturing.The minimum horizontal stress controls where the fractures are initiated,and the maximum horizontal stress dominates the direction of the hydraulic fracture propagation.Hydraulic fracturing performed in the shale reservoir normally has no stress barriers in most cases because the shale has a high minimum horizontal stress,inducing hydraulic fractures propagating beyond the reservoir zone,resulting in inefficient stimulation.This is a common problem in shale plays,and its mechanism is studied in the paper.It is also found that the on-azimuth well has a higher productivity than the off-azimuth well,because shear fractures are created in the off-azimuth well,causing main fractures to kink and increasing fracture tortuosity and friction.The Fuling shale gas play has a markedly higher minimum horizontal stress and much smaller horizontal stress difference.The high minimum horizontal stress causes a much higher formation breakdown pressure;therefore,hydraulic fracturing in the Fuling shale gas play needs a higher treatment pressure,which implies higher difficulty in fracture propagation.The small difference in the two horizontal stresses in the Fuling shale gas play generates shorter and more complex hydraulic fractures,because hydraulic fractures in this case are prone to curve to preexisting fractures.To overcome these difficulties,we recommend reducing well spacing and increasing proppant concentration to increase gas productivity for the Fuling shale gas development.
基金Project (Nos. 50539100,50679035 and 50509027) supported by the National Natural ScienceFoundation of China
文摘The solution of a slope stability problem can be approached by its least upper-bound and maximum lower-bound with high accuracy. The limit equilibrium methods that employ vertical slices imply a lower bound of the factor of safety. It has been successfully extended to the area of active earth pressure analysis that accounts for different input of locations of earth pressure applications. Those methods that employ slices with inclined interfaces give an upper-bound approach to the stability analysis. It enjoys a sound mechanical background and is able to provide accurate solutions of soil plasticity. It has been successfully extended to the area of bearing capacity analysis in which various empirical coefficients are no longer necessary. The 3D upper- and lower-bound methods under this framework have been made possible and show great potential for solving various engineering problems.
文摘A catalogue of possible landslide initial failure mechanisms, taking into account the geological setting and the geometry of the slope, the joint structure, the habitus of the rock blocks, as well as the mechanical behaviour of the rocks and of the rock mass (deformation and strength parameters), is presented. Its aim is to give geologists as well as engineers the opportunity to compare phenomena in the field and phenomena belonging to particular mechanisms and to find the mechanism occurring. The presented catalogue of initial landslide mechanisms only comprises the mechanisms having a clearly defined mechanical model that can be divided into empirical relations and into mechanical models, as well as an overview of run out models, which can be divided into empirical relations and into mechanical models.
基金financially supported by the National Natural Science Foundation of China (Grant No. 1177020290)
文摘Recently, a four-dimensional lattice spring model(4D-LSM) was developed to overcome the Poisson’s ratio limitation of the classical LSM by introducing the fourth-dimensional spatial interaction. In this work, some aspects of the 4D-LSM on solving problems in geomechanics are investigated, such as the ability to reproduce elastic properties of geomaterials, the capability of solving heterogeneous problems,the accuracy on modelling stress wave propagation, the ability to solve dynamic fracturing and the parallel computational efficiency. Our results indicate that the 4D-LSM is promising to deal with problems in geomechanics.
基金funding support from the National Natural Science Foundation of China(Grant No.52204030)Youth Innovation and Technology Support Program for Higher Education Institutions of Shandong Province,China(Grant No.2022KJ070)the National Natural Science Foundation of China Enterprise Innovation and Development Joint Fund Project(Grant No.U19B6003).
文摘Fiber-optic distributed strain sensing(FO-DSS)has been successful in monitoring strain changes along horizontal wellbores in hydraulically fractured reservoirs.However,the mechanism driving the various FO-DSS responses associated with near-wellbore hydraulic fracture properties is still unclear.To address this knowledge gap,we use coupled wellbore-reservoir-geomechanics simulations to study measured strain-change behavior and infer hydraulic fracture characteristics.The crossflow among fractures is captured through explicit modeling of the transient wellbore flow.In addition,local grid refinement is applied to accurately capture strain changes along the fiber.A Base Case model was designed with four fractures of varying properties,simulating strain change signals when the production well is shut-in for 10 d after 240 d of production and reopened for 2 d.Strain-pressure plots for different fracture clusters were used to gain insights into inferring fracture properties using DSS data.When comparing the model with and without the wellbore,distinct strain change signals were observed,emphasizing the importance of incorporating the wellbore in FO-DSS modeling.The effects of fracture spacing and matrix permeability on strain change signals were thoroughly investigated.The results of our numerical study can improve the understanding of the relation between DSS signals and fracture hydraulic properties,thus maximizing the value of the dataset for fracture diagnostics and characterization.
文摘Injection of large volumes of carbon dioxide(CO) for the purposes of greenhouse-gas emissions reduction has the potential to induce earthquakes.Operators of proposed projects must therefore take steps to reduce the risks posed by this induced seismicity.In this paper,we examine the causes of injection-induced seismicity(IIS),and how it should be monitored and modelled,and thereby mitigated.Many US case studies are found where fluids are injected into layers that are in close proximity to crystalline basement rocks.We investigate this issue further by comparing injection and seismicity in two areas where oilfield wastewater is injected in significant volumes:Oklahoma,where fluids are injected into a basal layer,and Saskatchewan,where fluids are injected into a much shallower layer.We suggest that the different induced seismicity responses in these two areas are at least in part due to these different injection depths.We go on to outline two different approaches for modelling IIS:a statistics based approach and a physical,numerical modelling based approach.Both modelling types have advantages and disadvantages,but share a need to be calibrated with good quality seismic monitoring data if they are to be used with any degree of reliability.We therefore encourage the use of seismic monitoring networks at all future carbon capture and storage(CCS) sites.
文摘Taking the theory of mixture as a basic .framework, the paper merges the primesof rational mechanics irreivrsible thermodynamics and soil meehanics into an organicsystem and proposes an axiomatics of geomechanics .The theoretical system consistsof 5 basis laws and 8 constitutive principles .and it erects a bridge across the gapbetween the pure theory of mechanics and engineering practice .
文摘Reservoir Geomechanics is a very comprehensive book spanning all aspects of stress within the accessible earth.The topics presented are interdisciplinary and encompass the fields of rock mechanics,tectonophysics,structural geology and petroleum engineering.It is divided into three parts in which the basic principles,stress indicators and measuring techniques,and their applications in addressing the problems of wellbore stability,permeability of critically stressed faults and reservoir depletion in sedimentary basins are presented and discussed in detail along with some case studies.
基金This work was partially carried out under the framework of In2Track,a research project of Shift2Rail.This work was partly financed by FCT/MCTES through national funds(PIDDAC)under the R&D Unit Institute for Sustainability and Innovation in Structural Engineering(ISISE)under reference UIDB/04029/2020It has been also financially supported by national funds through FCT—Foundation for Science and Technology,under grant agreement[PD/BD/127814/2016]attributed to Ana Ramos.
文摘The type of subgrade of a railroad foundation is vital to the overall performance of the track structure.With the train speed and tonnage increase,as well as environmental changes,the evaluation and influence of subgrade are even more paramount in the railroad track structure performance.A geomechanics classification for subgrade is proposed coupling the stiffness(resilient modulus)and permanent deformation behaviour evaluated by means of repeated triaxial loading tests.This classification covers from fine-to coarse-grained soils,grouped by UIC and ASTM.For this achievement,we first summarize the main models for estimating resilient modulus and permanent deformation,including the evaluation of their robustness and their sensitivity to mechanical and environmental parameters.This is followed by the procedure required to arrive at the geomechanical classification and rating,as well as a discussion of the influence of environmental factors.This work is the first attempt to obtain a new geomechanical classification that can be a useful tool in the evaluation and modelling of the foundation of railway structures.
基金supported by the National Natural Science Foundation of China (Grant Nos.52074164,42077267,42277174 and 42177130)the Fundamental Research Funds for the Central Universities,China (Grant No.2022JCCXSB03).
文摘Comprehensive mechanized top-coal caving mining is one of the efficient mining methods in coal mines.However,the goaf formed by comprehensive mechanized top-coal caving mining is high,and the goaf roof collapse will cause strong dynamic pressure disturbance,especially the collapse of thick hard roof.Strong dynamic pressure disturbance has an influence on the stability of the roadway,which can lead to large deformation.In order to solve the above problem,a comprehensive pressure releasing and constant resistance energy absorbing control method is proposed.Comprehensive pressure releasing can change the roadway roof structure and cut off the stress transfer between goaf and roadway,which can improve the stress environment of the roadway.The constant resistance energy absorbing(CREA)anchor cable can absorb the energy of surrounding rock deformation and resist the impact load of gangue collapse,so as to ensure the stability of roadway disturbed by strong dynamic pressure.A three-dimensional geomechanics model test is carried out,based on the roadway disturbed by strong dynamic pressure of the extra-large coal mine in western China,to verify the control effect of the new control method.The stress and displacement evolution laws of the roadway with traditional control method and new control method are analyzed.The pressure releasing and energy absorbing control mechanism of the new control method is clarified.The geomechanics model test results show that the new control method can increase the range of low stress zone by 150%and reduce the average stress and the displacement by 34.7%and 67.8%respectively,compared with the traditional control method.The filed application results show that the new control method can reduce the roadway surrounding rock displacement by 67.4%compared with the traditional control method.It shows that the new control method can effectively control the displacement of the roadway disturbed by strong dynamic pressure and ensure that the roadway meets the safety requirements.On this basis,the engineering suggestions for large deformation control of this kind of roadway are put forward.The new control method can provide a control idea for the roadway disturbed by strong dynamic pressure.
文摘The paper considers the methodology for a comprehensive analysis of the stability of an open pit-dump system,using limit equilibrium(LEM)and finite element(FEM)methods in the Russian CAE(computer-aided engineering)software Fidesys.It briefly highlights the issues of comparing limit equilibrium methods using the VNIMI(Research Institute of Geomechanics and Mine Surveying-Intersectoral Scientific Center"VNIMI")methodology and a specialized software product with numerical methods.The main focus of this study is to compare the results of the stability analysis in the volumetric model of the open pit-dump system using limit equilibrium and finite element methods in the CAE software Fidesys.It was found that,when modeling the combined operation of an open pit-dump system in complex terrain,both methods should be used,as each has its own advantages.The finite element method,for instance,has certain features that are not present in the calculations using the limit equilibrium approach.As a key scientific contribution,this paper introduces an automation program for calculating the stability of open-pit walls using the limit equilibrium method in CAE Fidesys,which was not previously integrated in the original software.The calculations performed with the use of this newly developed module were compared to those obtained from other widely used software solutions available on the market.The findings demonstrate a remarkable level of convergence in the calculation results for all relevant parameters,including the safety factor,localization,instability type,and deformation.The proposed approach i mproves the accuracy of calculati ons and ensures consistency between the higher stress design zones and the actual deformation and fracture patterns.It also enhances the ability to predict the behavior of rock mass when calculating stability parameters for facilities,both during operation and desi gn.
基金supported by the National Science and Technology Major Project of China(No.2025ZD1401403)the National Natural Science Foundation of China(No.42102156)+1 种基金the Tarim Oilfield Company R&D Center Project“Research and Application of Exploration Geomechanics Technology”(No.YF202505)the“CUG Scholar”Scientific Research Funds at China University of Geosciences(Wuhan)(No.2022046).
文摘Fracture-cave reservoirs are widely developed in carbonate formations and account for over 55%of global petroleum reserves.The productivity,formation mechanisms,and in-situ stress states of these reservoirs,characterized by fault-fracture-cave systems,are inherently interconnected.However,solely relying on geometric characterizations of natural fractures and cavities fails to meet the demands of modern petroleum exploration and development,particularly due to their complex structures,significant spatial heterogeneity,and strong geomechanical anisotropy.A critical challenge remains:how to safely and efficiently drill high-yield wells through highly fractured and cavernous zones while mitigating drilling risks.Consequently,establishing geomechanical models for fracture-cave reservoirs and predicting 3D stress fields are imperative for well trajectory optimization and reservoir reconstruction.This study integrates seismic interpretations of strike-slip faults with multi-attribute inversions of fracture-cave reservoirs.Using ANSYS 21.0 software,a homogeneous geomechanical model was constructed based on finely characterized geometries of fracturecave systems.Rock mechanics parameters,interpreted from conventional logging data and seismic attributes,were inverted to generate 3D distributions.These parameters were subsequently incorporated into the homogeneous model to develop a heterogeneous geomechanical framework.In-situ stress orientations were calibrated using drilling-induced fracture data,enabling predictions of the contemporary stress field in complex fracture-cave reservoirs.The methodology was validated in the Yueman Block of the Tarim Basin’s deep carbonate reservoir.Results revealed stress distribution patterns and key controlling factors,which were applied to evaluate wellbore stability,fracture reactivation risks,and optimize well trajectories.This approach provides a technical foundation for safe and efficient exploration-development of fracture-cave reservoirs worldwide.
文摘The feasibility of constructing shallow foundations on saturated sands remains uncertain.Seismic design standards simply stipulate that geotechnical investigations for a shallow foundation on such soils shall be conducted to mitigate the effects of the liquefaction hazard.This study investigates the seismic behavior of strip foundations on typical two-layered soil profiles-a natural loose sand layer supported by a dense sand layer.Coupled nonlinear dynamic analyses have been conducted to calculate response parameters,including seismic settlement,the acceleration response on the ground surface,and excess pore pressure beneath strip foundations.A novel liquefaction potential index(LPI_(footing)),based on excess pore pressure ratios across a given region of soil mass beneath footings is introduced to classify liquefaction severity into three distinct levels:minor,moderate,and severe.To validate the proposed LPI_(footing),the foundation settlement is evaluated for the different liquefaction potential classes.A classification tree model has been grown to predict liquefaction susceptibility,utilizing various input variables,including earthquake intensity on the ground surface,foundation pressure,sand permeability,and top layer thickness.Moreover,a nonlinear regression function has been established to map LPI_(footing) in relation to these input predictors.The models have been constructed using a substantial dataset comprising 13,824 excess pore pressure ratio time histories.The performance of the developed models has been examined using various methods,including the 10-fold cross-validation method.The predictive capability of the tree also has been validated through existing experimental studies.The results indicate that the classification tree is not only interpretable but also highly predictive,with a testing accuracy level of 78.1%.The decision tree provides valuable insights for engineers assessing liquefaction potential beneath strip foundations.
基金financially supported by the National Key Research and Development Program of China(2023YFC3012004-05)the National Natural Science Foundation of China(42422706,42077266)+1 种基金the Second Tibetan Plateau Scientific Expedition and Research Program(2019QZKK0904)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(2022062).
文摘Tensile strength is a crucial parameter for assessing rock stability and fracture characteristics,which play a significant role in the prediction and engineering design of geohazards.However,fault slip activity can weaken the strength of the surrounding rock mass,thereby influencing its mechanical behavior and failure mode.This study investigates the spatial variation of the tensile strength(σ_(t)),compressive strength(σ_(c)),P-wave velocity(V_(p)),and acoustic emission(AE)characteristics at varying distances from the Xianshuihe Fault zone(XSHF),focusing on three representative profiles.The results show that theσ_(t),σ_(c),and V_(p)significantly decrease near the fault(0–5km).Specifically,the relative change rates ofσ_(t),σ_(c),and V_(p)at approximately 5km from the fault are 1.55–1.8 times,1.22–1.86 times,and 1.02–1.25 times greater,respectively,compared to the near-fault zone.As the distance from the fault increases(10–20km),the rock integrity improves,and the mechanical properties recover.AE monitoring reveals increased microcracks near the fault,with higher b-value and dominant tensile failure modes.Further from the fault,the rock exhibits increased brittleness,and tensile cracking becomes more prevalent.Overall,the mechanical parameters and AE characteristics demonstrate predictable spatial variation with distance,providing valuable insights for identifying stress concentration zones and potential geohazards.
基金financially supported by the National Natural Science Foundation of China(Grant No.52374118)the Science and Technology Support Project of Guizhou Province,China(Project Grant No.Qiankehe Support(2022)General 247).
文摘In regions characterized with great mining depths,complex topography,and intense geological activities,solely relying on lateral pressure coefficients or linear boundary conditions for predicting the in situ stress field of rock bodies can induce substantial deviations and limitations.This study focuses on a typical karst area in Southwest Guizhou,China as its research background.It employs a hybrid approach integrating machine learning,numerical simulations,and field experiments to develop an optimization algorithm for nonlinear prediction of the complex three-dimensional(3D)in situ stress fields.Through collecting and fitting analysis of in situ stress measurement data from the karst region,the distributions of in situ stresses with depth were identified with nonlinear boundary conditions.A prediction model for in situ stress was then established based on artificial neural network(ANN)and genetic algorithm(GA)approach,validated in the typical karst landscape mine,Jinfeng Gold Mine.The results demonstrate that the model's predictions align well with actual measurements,showcasing consistency and regularity.Specifically,the error between the predicted and actual values of the maximum horizontal principal stress was the smallest,with an absolute error 0.01-3 MPa and a relative error of 0.04-15.31%.This model accurately and effectively predicts in situ stresses in complex geological areas.
基金supported by the National Natural Science Foundations of China(Nos.12272411 and 42007259)the State Key Laboratory for GeoMechanics and Deep Underground Engineering,the China University of Mining&Technology(No.SKLGDUEK2207)the Department of Science and Technology of Shaanxi Province(Nos.2022KXJ-107 and 2022JC-LHJJ-16).
文摘Underground engineering in extreme environments necessitates understanding rock mechanical behavior under coupled high-temperature and dynamic loading conditions.This study presents an innovative multi-scale cross-platform PFC-FDEM coupling methodology that bridges microscopic thermal damage mechanisms with macroscopic dynamic fracture responses.The breakthrough coupling framework introduces:(1)bidirectional information transfer protocols enabling seamless integration between PFC’s particle-scale thermal damage characterization and FDEM’s continuum-scale fracture propagation,(2)multi-physics mapping algorithms that preserve crack network geometric invariants during scale transitions,and(3)cross-platform cohesive zone implementations for accurate SHTB dynamic loading simulation.The coupled approach reveals distinct three-stage crack evolution characteristics with temperature-dependent density following an exponential model.High-temperature exposure significantly reduces dynamic strength ratio(60%at 800℃)and diminishes strain-rate sensitivity,with dynamic increase factor decreasing from 1.0 to 2.2(25℃)to 1.0-1.3(800℃).Critically,the coupling methodology captures fundamental energy redistribution mechanisms:thermal crack networks alter elastic energy proportion from 75%to 35%while increasing fracture energy from 5%to 30%.Numerical predictions demonstrate excellent experimental agreement(±8%peak stress-strain errors),validating the PFC-FDEM coupling accuracy.This integrated framework provides essential computational tools for predicting complex thermal-mechanical rock behavior in underground engineering applications.
