The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on t...The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on three mining methods, namely Underground Mining Method(UMM), Highwall Mining System(HMS) and Local Steep Slope Mining Method(LSSMM). A model was firstly established to simulate the impact that UMM and HMS exert on monitoring points and surface deformation. The way that stripping and excavation amount varies with different slope angle, and the corresponding end slope stability were analyzed in the mode of LSSMM. Then a TOPSIS model was established by taking into account six indicators such as recovery ratio, technical complexity and adaptability, the impact on surface mining production, production safety and economic benefits. Finally, LSSMM was determined as the best mining method for mining ultra-thick coal seams in end slope in HSCM.展开更多
When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key...When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key strata as a semi-infinite Euler-Bernoulli beam rested on a Winkler foundation with a local subsidence area.The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff.Then,the analytical solutions are verified by the results from experimental tests,FEM and InSAR,respectively.After that,the influence of changing parameters on deflections is studied with sensitivity analysis.The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam.The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam.The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.展开更多
Repetitive mining beneath bedding slopes is identified as a critical factor in geomorphic disturbances, especially landslides and surface subsidence. Prior research has largely concentrated on surface deformation in p...Repetitive mining beneath bedding slopes is identified as a critical factor in geomorphic disturbances, especially landslides and surface subsidence. Prior research has largely concentrated on surface deformation in plains due to multi-seam coal mining and the instability of natural bedding slopes, yet the cumulative impact of different mining sequences on bedding slopes has been less explored. This study combines drone surveys and geological data to construct a comprehensive three-dimensional model of bedding slopes. Utilizing FLAC3D and PFC2D models, derived from laboratory experiments, it simulates stress, deformation, and failure dynamics of slopes under various mining sequences. Incorporating fractal dimension analysis, the research evaluates the stability of slopes in relation to different mining sequences. The findings reveal that mining in an upslope direction minimizes disruption to overlying strata. Initiating extraction from lower segments increases tensile-shear stress in coal pillar overburdens, resulting in greater creep deformation towards the downslope than when starting from upper segments, potentially leading to localized landslides and widespread creep deformation in mined-out areas. The downslope upward mining sequence exhibits the least fractal dimensions, indicating minimal disturbance to both strata and surface. While all five mining scenarios maintain good slope stability under normal conditions, recalibrated stability assessments based on fractal dimensions suggest that downslope upward mining offers the highest stability under rainfall, contrasting with the lower stability and potential instability risks of upslope downward mining. These insights are pivotal for mining operations and geological hazard mitigation in multi-seam coal exploitation on bedding slopes.展开更多
In view of the study on mining transferred from open-pit to underground, the research on the problem of the stabil- ity of slope is less. This article combined the actual situation of the Gaohai Coal Mine in Fuxin Cit...In view of the study on mining transferred from open-pit to underground, the research on the problem of the stabil- ity of slope is less. This article combined the actual situation of the Gaohai Coal Mine in Fuxin City and set up a three-dimensional model of the part of Huizhou open-pit slope by the finite difference software. Through the three-dimensional numerical simulation study of the influence on the stability of slope by underground mining, the basic characteristics of the open-pit slope deformation and the situation of basic stability were discussed. The simulation results of the mining slope of the displacement and deformation analysis of the state for mining provide a reference to the slope stability research.展开更多
During underground mining,accurate revelation on the deformation and failure mechanisms of a high-steep slope under multi-layer mining conditions facilitates the prevention and control of geological disasters in mines...During underground mining,accurate revelation on the deformation and failure mechanisms of a high-steep slope under multi-layer mining conditions facilitates the prevention and control of geological disasters in mines.Numerical simulation based on discrete element theory can be used to explore the characteristics and mechanism of action of deformation and failure of a slope under complex geological and multi-layer mining conditions.By utilising PFC2 D(particle flow code) software,the deformation and failure characteristics of a high-steep slope in Faer Coal Mine in Guizhou Province,China were investigated.Additionally,the mechanism of influence of different numbers of mining layers on the deformation and failure of the high and steep slope was elucidated.The result showed that after the goaf passed by the slope toe,multi-layer mining aggravated the subsidence and deformation of the slope toe:the slope toppled forward as it sank.The toppling of the slope changed the slope structures:the strata in the front of the slope were transformed from anti-dip to down-dip features.Extruded by collapsedtoppled rock mass,the slope toe and the rock mass located in the lower part of the slope toe generally exhibited a locking effect on the slope.Multi-layer mining degraded the overall stability of the slope,in that the total displacement of the slope was much greater than the total mining thickness of the coal seams.Based on the aforementioned research,ideas for preventing and controlling geological disasters during mining operations under a high-steep slope were proposed.展开更多
Levees are affected by over-exploitation of river sand and river adjustments after the formation of sand pits. The slope stability is seriously threatened, drawing wide concern among experts and scholars in the area o...Levees are affected by over-exploitation of river sand and river adjustments after the formation of sand pits. The slope stability is seriously threatened, drawing wide concern among experts and scholars in the area of water conservancy. This study analyzed the uncertainties of slope stability of levees under river sand mining conditions, including uncertainty caused by interest- driven over-exploitation by sand mining contractors, and uncertainty of the distance from the slope or sand pit to the bottom of the levee under the action of cross-flow force after the sand pit forms. Based on the results of uncertainty analysis, the distribution and related parameters of these uncertainties were estimated according to the Yangtze River sand mining practice. A risk model of the slope instability of a levee under river sand mining conditions was built, and the possibility of slope instability under different slope gradients in a certain reach of the Yangtze River was calculated with the Monte Carlo method and probability combination method. The results indicated that the probability of instability risk rose from 2.38% to 4.74% as the pits came into being.展开更多
The design and practice in supporting the cut slope of an open-pit mine wereintroduced, in which the high pressure grouting method was used in reinforcing the weak formation inthe slopes. Based on a detailed geologica...The design and practice in supporting the cut slope of an open-pit mine wereintroduced, in which the high pressure grouting method was used in reinforcing the weak formation inthe slopes. Based on a detailed geological survey of the slope, a theoretical analysis was carriedout, and the design parameters were proposed, where the Tresca or Mohr-Coulomb yield criteria wasemployed. A patent technology, named 'Technology of high pressure and multiple grouting in differentlevels within a single hole', was employed in the construction. Anchor bars were also installed asgrouting proceeds. This method combines anchoring and grouting comprehensively and was foundsuccessful in practice.展开更多
Based on the results of similar material simulation, the laws of slope movementdue to mining under a gully were analyzed. Selected a slope rock as objective, the mechanisms of slope movement influence upon underground...Based on the results of similar material simulation, the laws of slope movementdue to mining under a gully were analyzed. Selected a slope rock as objective, the mechanisms of slope movement influence upon underground mining were proposed, and respective structural models were built by means of numerical modeling and physical simulation.It holds the point that the influence of slope movement on underground mining could becontrolled to some extent by appropriate measures. The results indicate that, forgully-ward mining, which mines toward a gully, the slope rock slides horizontally and rotates in layers; for gully-away mining, which mines away from the gully, the slope rock rotates in a reversed polygon. The slope movement associated with mining under a gully isattributed to pre-existing free faces in the ground gully and underground mining-inducedfree faces.展开更多
The application of a double-face reinforced retaining wall during road construction can reduce engineering costs, speed road paving and have a good influence on environment. An ABAQUS numerical model of a double-face ...The application of a double-face reinforced retaining wall during road construction can reduce engineering costs, speed road paving and have a good influence on environment. An ABAQUS numerical model of a double-face reinforced retaining wall was built. The influence of surface subsidence induced by mining was considered. A physical model test was also performed in the laboratory on a reinforced retaining wall. The influence of subsidence induced by mining was observed. The numerical results match measurements in the laboratory very well. The vertical pressure on the base of the retaining wall, the horizontal displacement of the wall and the horizontal soil pressure acting on the wall were analyzed. The differential settlement of the reinforced belt and axial forces in the wall were also studied.展开更多
A new type of airtight wall with the combination of foamed concrete and pier support was designed in this study. Based on the theories and models related to the foamed concrete and blasting shock load, using the numer...A new type of airtight wall with the combination of foamed concrete and pier support was designed in this study. Based on the theories and models related to the foamed concrete and blasting shock load, using the numerical analysis method, this study obtains the new material's mechanical and destruction laws through analyzing its reaction to different conditions of load (mining and shock waves), airtight wall thickness (1.2, 1.5, 1.8, 2.1 m) and steel pipe diameters (400, 450, 500 and 600 mm). The results show that: ①foamed concrete can have very good suspension, and the pier column support is the main carrier of roof pressure; ② the damaged area of foamed concrete decreases as the foamed concrete thickness increases. Under impact loading, the thickness of the foamed concrete wall plays a more obvious role in retaining its integrity; ③under the same mining pressure, the damage area increases as the steel pipe diameter increases; ④ with additional mining stress increase, under whether static load or impact load, the stress on the foamed concrete and steel pipe will also increase gradually, therefore the actual airtight wall design will need to be based on specific circumstances in steel stress.展开更多
We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show th...We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface.The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully,whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully.The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable,multilateral block hinged structure,due to slipping.The subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground pressure.With an increase in the mass of the block body,the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf,resulting in a decrease of the underground pressure.展开更多
This paper outlines the results obtained from real time microseismic monitoring of an opencast coal mine in South India.The objective of the study is to investigate the stress changes within the rockmass along the slo...This paper outlines the results obtained from real time microseismic monitoring of an opencast coal mine in South India.The objective of the study is to investigate the stress changes within the rockmass along the slope due to underground mine development operation and their impact on the stability of the highwall slope.The installed microseismic systems recorded the seismic triggerings down toà2 moment magnitude.In general,most of the events recorded during the monitoring period are weak in seismic energy.The study adopts a simple and more reliable tool to characterize the seismically active zone for assessing the stability of the highwall in real time.The impact of underground working on the slope is studied on the basis of the seismic event impact contours and seismic clusters.During the monitoring period,it is observed that the intensity of the overall microseismic activity along the slope due to the mine development operations did not cause any adverse impact on the highwall stability.展开更多
Underground mining activities and rainfall have potential important influence on the initiation and reactivation of the slope deformations,especially on the steep rock slope. In this paper,using the discrete element m...Underground mining activities and rainfall have potential important influence on the initiation and reactivation of the slope deformations,especially on the steep rock slope. In this paper,using the discrete element method(UDEC),numerical simulation was carried out to investigate deformation features and the failure mechanism of the steep rock slope under mining activities and rainfall. A steep rock slope numerical model was created based on a case study at the Wulong area in Chongqing city,China. Mechanical parameters of the rock mass have been determined by situ measurements and laboratory measurements. A preliminary site monitoring system has been realized,aiming at getting structure movements and stresses of unstablerock masses at the most significant discontinuities. According to the numerical model calibrated based on the monitoring data,four types of operation conditions are designed to reveal the effect of mining excavation and extreme rainfall on the deformation of the steep rock slope.展开更多
This paper will present a detailed analysis of the deformation mechanism and stability assessment of the slope through field investigations, numerical modeling and measurements. Field investigation indicated that thre...This paper will present a detailed analysis of the deformation mechanism and stability assessment of the slope through field investigations, numerical modeling and measurements. Field investigation indicated that three thin coal seams encountered large mined-out area at one side and free surface of hill slope at the other side, which lead to the caving of roof strata movement, ground movement and crown crack along the preferred orientations of joints. The three-dimensional numeri- cal modeling study on the case demonstrated that the plasticity failure occurred gradually along with the extension of mined-out area in depth. When the depth of mining reached the verge defined by the seismic prospecting method, a large mount of tension failure occurred on the crown of the slope. The factor of safety was 1.36 calculated by the shear strength reduction technique, which indicated the slope was in stable state. The measurement showed that the residual deformation occurred before 1998 and became stable subsequently, which indicated that the residual deformation almost finished and the slope is in stable state.展开更多
Stability is always the most important problem after high slope was excavated.The study analyzed the stress and strain inside the slope by Finite Element Method(FEM) and carried through stress distribution and failure...Stability is always the most important problem after high slope was excavated.The study analyzed the stress and strain inside the slope by Finite Element Method(FEM) and carried through stress distribution and failure zone,then analyzed the stability of the slope using three different methods and came to the conclusion that it is in unstable condition,so the designed retaining wall was put forward which makes the slope stable.展开更多
Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining tech...Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining technology for residual coal of end slopes.In the proposal a conveyance road and ventilation conveyance near the slope are built,corresponding to the pit mining area and the surface coal mine dump,as well as an interval haulage tunnel and air-inlet tunnel.The outcome shows that such mining method may reduce the effect to slope stability from underground mining,it does not affect the dumping advance and has a high recovery rate of residual coal resources.The working face is timbered by single hydraulic props,transported by a scraper conveyor and supported by coal walls.This method of mining is one of layered top coal caving,with high resource recovery,low production cost where positive economic benefit can be realized.展开更多
The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a re...The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result,structurally-controlled failures(e.g.planar,wedge or toppling)are most likely to occur.The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties.This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method.Finally,these two probabilities are combined to provide an overall measure of the probability of failure(PoF)of the bench slope system.The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out.It is shown that by combining field and laboratory measurements and engineering judgment,the probability density functions(PDF)of the discontinuity parameters can be obtained.These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure.The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.展开更多
In order to study the influence of depth-thickness ratio on bedding slope stability, whose sliding surface is flexural concave in shape under mining conditions, this paper aims to study the characteristics ofdeformari...In order to study the influence of depth-thickness ratio on bedding slope stability, whose sliding surface is flexural concave in shape under mining conditions, this paper aims to study the characteristics ofdeformarion and damage of bedding sliding with depth-thickness ratios of 200:1,150:1,120:1,100:1 and 50:1 by adopting numerical simulation analysis software combined with laboratory-made "under the influence of mining variable sliding surface slope similar simulation test bed", and to propose identification methods for slope stability under the infuence of mining. The results show that mining activities under the slope reduce slope stability. With a decrease in the mining depth ratio, the influence of mining on the slope increases gradually, and the damage to the slope gradually expands, the stability of the slope grad- ually reduces, fracture occurs on the slope toe and the central fissure gradually develops to the surface, and reaches slide threshold when the depth-thickness ratio is 50:1.展开更多
To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of th...To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of the 34,600 profile are obtained on the basis of hydrology, geology, and monitoring data.The residual thrust method is utilized to calculate the stability coefficients, which are 1.225 and 1.00 under sound and transfixion conditions, respectively. According to the rock damage and fragmentation and the principle of mechanical parameter degradation, the mechanical models of the slide mass development of the hard and soft rock slopes are established. An integrated model for calculating the slope stability coefficient is built considering water, vibration, and other external factors that pertain to the structural plane damage mechanism and the generating mechanism of the sliding mass. The change curve of the stability coefficient in the slide mass development is obtained from the relevant analyses,and afterwards, the stability control measures are proposed. The analysis results indicate that in the cracking stage of the hard rock, the slope stability coefficient decreases linearly with the increase in the length Lbof the hard rock crack zone. The linear slope is positively correlated to rock cohesion c. In the transfixion stage of the soft rock, the decrease speed of the stability coefficient is positively correlated to the residual strength of the soft rock. When the slope is stable, the stability coefficient is in a quadratic-linear relationship with the decreased height Dh of the side slope and in a linear relationship with anchoring force P.展开更多
Based on the study of the slope with gently granular structure in Xingqiao open mine, a new safety cleaning bank mode for steep slope mining was developed, including setting up dint cut, and forming natural retaining ...Based on the study of the slope with gently granular structure in Xingqiao open mine, a new safety cleaning bank mode for steep slope mining was developed, including setting up dint cut, and forming natural retaining wall based on the character of gentle incline slope. It can effectively eliminate the impact of sliding body on the bottom working place and slope body, reduce the dilution of ore, keep rainwater from upper steps away, decrease influence of the weak intermediate layer, and cut cost of disposal waste rock. The safety and reliability of the mode were analyzed and verified from 3 aspects: static load calculation, ANSYS simulation of dynamic loading and spot experiment. The result of static loading calculation shows that the retaining wall can support accumulation and extrusion of granular body, and the glide or overturn disaster will not take place. The simulations of dynamic loading show that the retaining wall remains stable until sliding body collapses from 360 m (10 sublevels). Only one new safety cleaning bank in each 15 sublevels can fully meet the need of engineering. The new mode sustains steep slope (mining,) increases the angle of ultimate slope, and reduces invalid overburden amount of rock by 3%5%. The result of spot experiment has verified the exactness of the above calculations and simulations.展开更多
基金provided by the National Natural Science Foundation of China(No.90510002)the Science and Technology Research of the Ministry of Education of China(No.306008)
文摘The paper aims to identify a reasonable method for mining ultra-thick coal seams in an end-slope in surface mine, With a case study of Heidaigou surface coal mine(HSCM), the paper conducted a comparative research on three mining methods, namely Underground Mining Method(UMM), Highwall Mining System(HMS) and Local Steep Slope Mining Method(LSSMM). A model was firstly established to simulate the impact that UMM and HMS exert on monitoring points and surface deformation. The way that stripping and excavation amount varies with different slope angle, and the corresponding end slope stability were analyzed in the mode of LSSMM. Then a TOPSIS model was established by taking into account six indicators such as recovery ratio, technical complexity and adaptability, the impact on surface mining production, production safety and economic benefits. Finally, LSSMM was determined as the best mining method for mining ultra-thick coal seams in end slope in HSCM.
基金supported by the National Natural Science Foundation of China(No.52074042)National Key R&D Program of China(No.2018YFC1504802).
文摘When the mining goaf is close to the cliff,rock slope subsidence induced by underground mining is significantly affected by its boundary conditions.In this study,an analytical method is proposed by considering the key strata as a semi-infinite Euler-Bernoulli beam rested on a Winkler foundation with a local subsidence area.The analytical solutions of deflection are derived by analyzing the boundary and continuity conditions of the cliff.Then,the analytical solutions are verified by the results from experimental tests,FEM and InSAR,respectively.After that,the influence of changing parameters on deflections is studied with sensitivity analysis.The results show that the distance between goaf and cliff significantly affects the deflection of semi-infinite beam.The response of semi-infinite beam is obviously determined by the length of goaf and the bending stiffness of beam.The comparisons between semi-infinite beam and infinite beam illustrate the ascendancy of the improved model in such problems.
基金funded by the Sichuan Science and Technology Program (grant number 2022NSFSC1176)the open Fund for National Key Laboratory of Geological Disaster Prevention and Environmental Protection (grant number SKLGP2022K027)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project (SKLGP2022Z001)。
文摘Repetitive mining beneath bedding slopes is identified as a critical factor in geomorphic disturbances, especially landslides and surface subsidence. Prior research has largely concentrated on surface deformation in plains due to multi-seam coal mining and the instability of natural bedding slopes, yet the cumulative impact of different mining sequences on bedding slopes has been less explored. This study combines drone surveys and geological data to construct a comprehensive three-dimensional model of bedding slopes. Utilizing FLAC3D and PFC2D models, derived from laboratory experiments, it simulates stress, deformation, and failure dynamics of slopes under various mining sequences. Incorporating fractal dimension analysis, the research evaluates the stability of slopes in relation to different mining sequences. The findings reveal that mining in an upslope direction minimizes disruption to overlying strata. Initiating extraction from lower segments increases tensile-shear stress in coal pillar overburdens, resulting in greater creep deformation towards the downslope than when starting from upper segments, potentially leading to localized landslides and widespread creep deformation in mined-out areas. The downslope upward mining sequence exhibits the least fractal dimensions, indicating minimal disturbance to both strata and surface. While all five mining scenarios maintain good slope stability under normal conditions, recalibrated stability assessments based on fractal dimensions suggest that downslope upward mining offers the highest stability under rainfall, contrasting with the lower stability and potential instability risks of upslope downward mining. These insights are pivotal for mining operations and geological hazard mitigation in multi-seam coal exploitation on bedding slopes.
文摘In view of the study on mining transferred from open-pit to underground, the research on the problem of the stabil- ity of slope is less. This article combined the actual situation of the Gaohai Coal Mine in Fuxin City and set up a three-dimensional model of the part of Huizhou open-pit slope by the finite difference software. Through the three-dimensional numerical simulation study of the influence on the stability of slope by underground mining, the basic characteristics of the open-pit slope deformation and the situation of basic stability were discussed. The simulation results of the mining slope of the displacement and deformation analysis of the state for mining provide a reference to the slope stability research.
基金funded by the National Natural Science Foundation of China (Grants No. 41877273)the Innovative Research Groups of the National Natural Science Foundation of China (Grants No. 41521002)+1 种基金the State Key Laboratory of Geohazard Disaster Prevention and Geoenvironment Protection (Chengdu University of Technology) (Grants No. SKLGP2017Z016)the Guizhou Provincial Geological Environment Monitoring Institute, and the Faer Coal Mine。
文摘During underground mining,accurate revelation on the deformation and failure mechanisms of a high-steep slope under multi-layer mining conditions facilitates the prevention and control of geological disasters in mines.Numerical simulation based on discrete element theory can be used to explore the characteristics and mechanism of action of deformation and failure of a slope under complex geological and multi-layer mining conditions.By utilising PFC2 D(particle flow code) software,the deformation and failure characteristics of a high-steep slope in Faer Coal Mine in Guizhou Province,China were investigated.Additionally,the mechanism of influence of different numbers of mining layers on the deformation and failure of the high and steep slope was elucidated.The result showed that after the goaf passed by the slope toe,multi-layer mining aggravated the subsidence and deformation of the slope toe:the slope toppled forward as it sank.The toppling of the slope changed the slope structures:the strata in the front of the slope were transformed from anti-dip to down-dip features.Extruded by collapsedtoppled rock mass,the slope toe and the rock mass located in the lower part of the slope toe generally exhibited a locking effect on the slope.Multi-layer mining degraded the overall stability of the slope,in that the total displacement of the slope was much greater than the total mining thickness of the coal seams.Based on the aforementioned research,ideas for preventing and controlling geological disasters during mining operations under a high-steep slope were proposed.
基金supported by the Special Fund for Public Welfare Industry of the Ministry of Water Resources of China (Grant No. 201001007)
文摘Levees are affected by over-exploitation of river sand and river adjustments after the formation of sand pits. The slope stability is seriously threatened, drawing wide concern among experts and scholars in the area of water conservancy. This study analyzed the uncertainties of slope stability of levees under river sand mining conditions, including uncertainty caused by interest- driven over-exploitation by sand mining contractors, and uncertainty of the distance from the slope or sand pit to the bottom of the levee under the action of cross-flow force after the sand pit forms. Based on the results of uncertainty analysis, the distribution and related parameters of these uncertainties were estimated according to the Yangtze River sand mining practice. A risk model of the slope instability of a levee under river sand mining conditions was built, and the possibility of slope instability under different slope gradients in a certain reach of the Yangtze River was calculated with the Monte Carlo method and probability combination method. The results indicated that the probability of instability risk rose from 2.38% to 4.74% as the pits came into being.
文摘The design and practice in supporting the cut slope of an open-pit mine wereintroduced, in which the high pressure grouting method was used in reinforcing the weak formation inthe slopes. Based on a detailed geological survey of the slope, a theoretical analysis was carriedout, and the design parameters were proposed, where the Tresca or Mohr-Coulomb yield criteria wasemployed. A patent technology, named 'Technology of high pressure and multiple grouting in differentlevels within a single hole', was employed in the construction. Anchor bars were also installed asgrouting proceeds. This method combines anchoring and grouting comprehensively and was foundsuccessful in practice.
基金Supported by the Program for New Century Excellent Talents in University (NCET-05-0480)Gradute Student Scientific Research Innovation in University of Jiangsu Province
文摘Based on the results of similar material simulation, the laws of slope movementdue to mining under a gully were analyzed. Selected a slope rock as objective, the mechanisms of slope movement influence upon underground mining were proposed, and respective structural models were built by means of numerical modeling and physical simulation.It holds the point that the influence of slope movement on underground mining could becontrolled to some extent by appropriate measures. The results indicate that, forgully-ward mining, which mines toward a gully, the slope rock slides horizontally and rotates in layers; for gully-away mining, which mines away from the gully, the slope rock rotates in a reversed polygon. The slope movement associated with mining under a gully isattributed to pre-existing free faces in the ground gully and underground mining-inducedfree faces.
基金Projects 50874105 supported by the National Natural Science Foundation of China20070290532 by the Specialized Research Fund for Doctoral Program of Higher Education
文摘The application of a double-face reinforced retaining wall during road construction can reduce engineering costs, speed road paving and have a good influence on environment. An ABAQUS numerical model of a double-face reinforced retaining wall was built. The influence of surface subsidence induced by mining was considered. A physical model test was also performed in the laboratory on a reinforced retaining wall. The influence of subsidence induced by mining was observed. The numerical results match measurements in the laboratory very well. The vertical pressure on the base of the retaining wall, the horizontal displacement of the wall and the horizontal soil pressure acting on the wall were analyzed. The differential settlement of the reinforced belt and axial forces in the wall were also studied.
文摘A new type of airtight wall with the combination of foamed concrete and pier support was designed in this study. Based on the theories and models related to the foamed concrete and blasting shock load, using the numerical analysis method, this study obtains the new material's mechanical and destruction laws through analyzing its reaction to different conditions of load (mining and shock waves), airtight wall thickness (1.2, 1.5, 1.8, 2.1 m) and steel pipe diameters (400, 450, 500 and 600 mm). The results show that: ①foamed concrete can have very good suspension, and the pier column support is the main carrier of roof pressure; ② the damaged area of foamed concrete decreases as the foamed concrete thickness increases. Under impact loading, the thickness of the foamed concrete wall plays a more obvious role in retaining its integrity; ③under the same mining pressure, the damage area increases as the steel pipe diameter increases; ④ with additional mining stress increase, under whether static load or impact load, the stress on the foamed concrete and steel pipe will also increase gradually, therefore the actual airtight wall design will need to be based on specific circumstances in steel stress.
基金financial support for this work,provided by the National Natural Science Foundation of China(Nos.51004101 and 50904063)the Science Foundation for Young Scholars of China University of Mining & Technology(Nos.2008A003 and 2009A001 )the Graduate Student Scientific Research Innovation in the University of Jiangsu Province(No.CX07B_149z).
文摘We studied underground pressure and its mechanism during back-gully mining in a shallow coal seam under a bedrock gully slope,by means of physical simulation,numerical modeling and field monitoring.The results show that the intensity of underground pressure is related to its relative position at the coalface.The underground pressure is intensive and the support resistance reaches a maximum when the coalface is at the bottom of the gully,whereas the underground pressure is moderate and decreases gradually when the coalface passes the gully.The mechanism of these changes is analyzed when the slope rotated in a reversed direction to the slope dip during back-gully mining and form an unstable,multilateral block hinged structure,due to slipping.The subsidence of multilateral blocks is considerable when the block fragmentation is small,resulting in enormous changes in the underground pressure.With an increase in the mass of the block body,the block displacement will be reduced in conjunction with an increased clamp effect by both the unbroken rocks and broken rocks in the goaf,resulting in a decrease of the underground pressure.
基金the S&T project ‘‘High resolution microseismic monitoring for early detection and analysis of slope failure in opencast mines’’ funded by inistry of Coal,Government of IndiaThe Singareni Collieries Co Ltd (SCCL),Andhra Pradesh
文摘This paper outlines the results obtained from real time microseismic monitoring of an opencast coal mine in South India.The objective of the study is to investigate the stress changes within the rockmass along the slope due to underground mine development operation and their impact on the stability of the highwall slope.The installed microseismic systems recorded the seismic triggerings down toà2 moment magnitude.In general,most of the events recorded during the monitoring period are weak in seismic energy.The study adopts a simple and more reliable tool to characterize the seismically active zone for assessing the stability of the highwall in real time.The impact of underground working on the slope is studied on the basis of the seismic event impact contours and seismic clusters.During the monitoring period,it is observed that the intensity of the overall microseismic activity along the slope due to the mine development operations did not cause any adverse impact on the highwall stability.
基金financially supported by a grant from China Natural Science foundation (51379112,51422904)the National Program on Key Basic Research Project of China (973 Program)(2013CB036002)the National Natural Science Foundation of China (51309144)
文摘Underground mining activities and rainfall have potential important influence on the initiation and reactivation of the slope deformations,especially on the steep rock slope. In this paper,using the discrete element method(UDEC),numerical simulation was carried out to investigate deformation features and the failure mechanism of the steep rock slope under mining activities and rainfall. A steep rock slope numerical model was created based on a case study at the Wulong area in Chongqing city,China. Mechanical parameters of the rock mass have been determined by situ measurements and laboratory measurements. A preliminary site monitoring system has been realized,aiming at getting structure movements and stresses of unstablerock masses at the most significant discontinuities. According to the numerical model calibrated based on the monitoring data,four types of operation conditions are designed to reveal the effect of mining excavation and extreme rainfall on the deformation of the steep rock slope.
基金Supported by the National Natural Science Foundation of China for Youth (51004065) the National Basic Research Program of China (2012CB724208)
文摘This paper will present a detailed analysis of the deformation mechanism and stability assessment of the slope through field investigations, numerical modeling and measurements. Field investigation indicated that three thin coal seams encountered large mined-out area at one side and free surface of hill slope at the other side, which lead to the caving of roof strata movement, ground movement and crown crack along the preferred orientations of joints. The three-dimensional numeri- cal modeling study on the case demonstrated that the plasticity failure occurred gradually along with the extension of mined-out area in depth. When the depth of mining reached the verge defined by the seismic prospecting method, a large mount of tension failure occurred on the crown of the slope. The factor of safety was 1.36 calculated by the shear strength reduction technique, which indicated the slope was in stable state. The measurement showed that the residual deformation occurred before 1998 and became stable subsequently, which indicated that the residual deformation almost finished and the slope is in stable state.
文摘Stability is always the most important problem after high slope was excavated.The study analyzed the stress and strain inside the slope by Finite Element Method(FEM) and carried through stress distribution and failure zone,then analyzed the stability of the slope using three different methods and came to the conclusion that it is in unstable condition,so the designed retaining wall was put forward which makes the slope stable.
文摘Given the conditions of residual coal from the boundary of a flat dipping open-pit mine,which uses strip areas mining and inner dumping with slope-covering,we propose an open-pit and underground integrated mining technology for residual coal of end slopes.In the proposal a conveyance road and ventilation conveyance near the slope are built,corresponding to the pit mining area and the surface coal mine dump,as well as an interval haulage tunnel and air-inlet tunnel.The outcome shows that such mining method may reduce the effect to slope stability from underground mining,it does not affect the dumping advance and has a high recovery rate of residual coal resources.The working face is timbered by single hydraulic props,transported by a scraper conveyor and supported by coal walls.This method of mining is one of layered top coal caving,with high resource recovery,low production cost where positive economic benefit can be realized.
基金supported by a scholarship from the Peruvian Institute of Mining Engineers
文摘The geotechnical slope design of an open pit wall starts at the bench scale configuration.At this scale,the rock slope stability is governed primarily by the geological discontinuities within the rock mass and as a result,structurally-controlled failures(e.g.planar,wedge or toppling)are most likely to occur.The probabilistic approach offers a major advantage over the traditional deterministic method in that it accounts for the different degrees of variability and uncertainty often encountered in rock properties.This paper presents a bench slope stability assessment for an open pit mine in Peru using a probabilistic-based approach by coupling a kinematic analysis based on stereographic projection techniques followed by a kinetic analysis by means of the limit equilibrium method.Finally,these two probabilities are combined to provide an overall measure of the probability of failure(PoF)of the bench slope system.The case study is characterized by significant scatter in the geometrical and mechanical properties of the joints.Extensive surface mapping was conducted at 36 different sites following the ISRM suggested procedures.Several direct shear tests were carried out.It is shown that by combining field and laboratory measurements and engineering judgment,the probability density functions(PDF)of the discontinuity parameters can be obtained.These are then used in a Monte Carlo simulation process to compute both kinematic and kinetic probabilities of failure.The overall probability of failure aims to provide the design engineer with a tool to critically evaluate the bench performance from a geotechnical risk perspective and to provide a basis for future bench design optimization.
文摘In order to study the influence of depth-thickness ratio on bedding slope stability, whose sliding surface is flexural concave in shape under mining conditions, this paper aims to study the characteristics ofdeformarion and damage of bedding sliding with depth-thickness ratios of 200:1,150:1,120:1,100:1 and 50:1 by adopting numerical simulation analysis software combined with laboratory-made "under the influence of mining variable sliding surface slope similar simulation test bed", and to propose identification methods for slope stability under the infuence of mining. The results show that mining activities under the slope reduce slope stability. With a decrease in the mining depth ratio, the influence of mining on the slope increases gradually, and the damage to the slope gradually expands, the stability of the slope grad- ually reduces, fracture occurs on the slope toe and the central fissure gradually develops to the surface, and reaches slide threshold when the depth-thickness ratio is 50:1.
基金financially supported by the National Natural Science Foundation of China (No. 51034005)National High Technology Research and Development Program of China (No. 2012AA062004)Program for New Century Excellent Talents in University of China (No. NCET-13-1022)
文摘To study the stability of the west slope in Buzhaoba Open-Pit Mine and determine the aging stability coefficient during slide mass development, the deformation band of the west slope and the slide mass structure of the 34,600 profile are obtained on the basis of hydrology, geology, and monitoring data.The residual thrust method is utilized to calculate the stability coefficients, which are 1.225 and 1.00 under sound and transfixion conditions, respectively. According to the rock damage and fragmentation and the principle of mechanical parameter degradation, the mechanical models of the slide mass development of the hard and soft rock slopes are established. An integrated model for calculating the slope stability coefficient is built considering water, vibration, and other external factors that pertain to the structural plane damage mechanism and the generating mechanism of the sliding mass. The change curve of the stability coefficient in the slide mass development is obtained from the relevant analyses,and afterwards, the stability control measures are proposed. The analysis results indicate that in the cracking stage of the hard rock, the slope stability coefficient decreases linearly with the increase in the length Lbof the hard rock crack zone. The linear slope is positively correlated to rock cohesion c. In the transfixion stage of the soft rock, the decrease speed of the stability coefficient is positively correlated to the residual strength of the soft rock. When the slope is stable, the stability coefficient is in a quadratic-linear relationship with the decreased height Dh of the side slope and in a linear relationship with anchoring force P.
文摘Based on the study of the slope with gently granular structure in Xingqiao open mine, a new safety cleaning bank mode for steep slope mining was developed, including setting up dint cut, and forming natural retaining wall based on the character of gentle incline slope. It can effectively eliminate the impact of sliding body on the bottom working place and slope body, reduce the dilution of ore, keep rainwater from upper steps away, decrease influence of the weak intermediate layer, and cut cost of disposal waste rock. The safety and reliability of the mode were analyzed and verified from 3 aspects: static load calculation, ANSYS simulation of dynamic loading and spot experiment. The result of static loading calculation shows that the retaining wall can support accumulation and extrusion of granular body, and the glide or overturn disaster will not take place. The simulations of dynamic loading show that the retaining wall remains stable until sliding body collapses from 360 m (10 sublevels). Only one new safety cleaning bank in each 15 sublevels can fully meet the need of engineering. The new mode sustains steep slope (mining,) increases the angle of ultimate slope, and reduces invalid overburden amount of rock by 3%5%. The result of spot experiment has verified the exactness of the above calculations and simulations.