The influence of ground stress was quantitatively analyzed on coal seam gas pressure and gas content in this paper.Mining activities in coal mine can result in stress concentration in the coal(rock)body around the min...The influence of ground stress was quantitatively analyzed on coal seam gas pressure and gas content in this paper.Mining activities in coal mine can result in stress concentration in the coal(rock)body around the mining space,but porosity of the coal seam would not change too much.Therefore,gas pressure and gas content in the coal seam are slightly affected.Studies showed that the free gas was gradually transformed into adsorbed gas,and the gas adsorption volume was small,and then gas pressure increases roughly linearly when the porosity decreased because of stress influence.Additionaly,when porosity of coal seam reduced to 40%,the amount of adsorbed gas accounted for no more than 10%of coal seam gas content,and the increase of gas pressure did not exceed 15%of the original gas pressure.展开更多
We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum ten...We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60° and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field.展开更多
Ground stress is the fundamental cause of deformation and failure during underground structural engi- neering. Field stress measurements in the main coal bed in the Lüliang mining area were made by the bore hole,...Ground stress is the fundamental cause of deformation and failure during underground structural engi- neering. Field stress measurements in the main coal bed in the Lüliang mining area were made by the bore hole, stress relief method. From these data the ground stress distribution of the mining area was obtained. The relationship between the horizontal principal stress and the deformation and failure of a roadway is discussed with an engineering example. The results indicate that horizontal stress dominates in the shallow crust in the Lüliang mining area. Roadways at different angles to the maximum principal stress have different levels of stress concentration. This leads to a significant difference in stability of the corresponding roadways. These research results provide an important criterion for determining roadway position and direction, stope layout, and roadway support design.展开更多
Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the per- meability in the extraction of gas by ground drilling. The ground stress around the well was ana...Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the per- meability in the extraction of gas by ground drilling. The ground stress around the well was analyzed by using theory of elasticity. The pressure when the well fractured is formulated and the effect of ground stress on pressure is discussed. The effect of ground-stress-differences on hydraulic fracturing was analyzed by using the numerical software RFPA2D-Flow in reference to the tectonic stress in Jincheng coal area. The results show that: 1) the position where initial fracture appears is random and fracture branches emerge when the fractures expand if ground stresses in any two directions within a horizontal plane are equal; 2) other- wise, the fractures expand in general along the direction of maximum ground stress and the critical pressure decreases with in- creasing ground-stress-differences and 3) the preferred well-disposition pattern is diamond shaped. The preferred well spacing is 250 m×300 m. This study can provide a reference for the design of wells.展开更多
A new back-analysis method of ground stress is proposed with comprehensive consideration of influence of topography, geology and nonlinear physical mechanical properties of rock on ground stress. This method based on ...A new back-analysis method of ground stress is proposed with comprehensive consideration of influence of topography, geology and nonlinear physical mechanical properties of rock on ground stress. This method based on non-uniform rational B-spline (NURBS) technology provides the means to build a refined three-dimensional finite element model with more accurate meshing under complex terrain and geological conditions. Meanwhile, this method is a back-analysis of ground stress with combination of multivariable linear regression model and neural network (ANN) model. Firstly, the regression model is used to fit approximately boundary loads. Regarding the regressed loads as mean value, some sets of boundary loads with the same interval are constructed according to the principle of orthogonal design, to calculate the corresponding ground stress at the observation positions using finite element method. The results (boundary loads and the corresponding ground stress) are added to the samples for ANN training. And on this basis, an ANN model is established to implement higher precise back-analysis of initial ground stress. A practical application case shows that the relative error between the inversed ground stress and observed value is mostly less than 10 %, which can meet the need of engineering design and construction requirements.展开更多
The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In add...The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In addition,the experimental equipment in many cases cannot meet the actual conditions and the experimental cost is very high. These comprehensive factors cause the existing casing design to not meet the actual conditions and cause casing deformation,affecting the drilling operation in Tarim oil field. The finite element method is the only effective method to solve this problem at present,but the re-modelling process is time-consuming because of the changes in the parameters,such as the cement properties,casing centrality,and the casing size. In this article,an artificial intelligence method based on support vector machine(SVM) to predict the maximum stress of an offcenter casing under non-uniform ground stress has been proposed. After a program based on a radial basis function(RBF)-support vector regression(SVR)(ε-SVR) model was established and validated,we constructed a data sample with a capacity of 120 by using the finite element method,which could meet the demand of the nine-factor ε-SVR model to predict the maximum stress of the casing. The results showed that the artificial intelligence prediction method proposed in this manuscript had satisfactory prediction accuracy and could be effectively used to predict the maximum stress of an off-center casing under complex downhole conditions.展开更多
In this paper, we discussed the influence of the initial tectonic stress on the relative measurement value of the ground stress when a long cylindrical straingauge is used in the viscoelastic media. We simulate the...In this paper, we discussed the influence of the initial tectonic stress on the relative measurement value of the ground stress when a long cylindrical straingauge is used in the viscoelastic media. We simulate the whole system consisting of the stratum, cement ring and the straingauge cylinder with a three layer medium model and obtain the solution of radial displacement on the inner wall of the straingauge under the action of initial tectonic stress by using the correspondence principle. The result showes: 1) The influence of initial stress making of the radial displacement on the inner wall of the straingauge increases gradually with time at a gradually reduced rate and tends to a certain value eventually; 2) The principal stress with a magnitude of [C 0+C 1 exp (- ω 1t)+ C 2 exp(- ω 2t )] σ i0 in the opposite direction of initial stress will be superimposed to the measuring result of stress change without considering the initial stress. where C 0, C 1, C 2 and ω 1, ω 2 are related only to the mechanical property of the stratum, σ i0 (i=1, 2) are the two principal components of the initial tectonic stress. It is pointed out that the initial tectonic stress affects obviously on the measurement of the relative change of ground stress in the cases of soft strata and high initial stress.展开更多
When mining metal mines with steep structure planes by the caving method,there is a mechanical model in which the horizontal stress on the rock mass is simplified as a column before surface subsidence.The model is use...When mining metal mines with steep structure planes by the caving method,there is a mechanical model in which the horizontal stress on the rock mass is simplified as a column before surface subsidence.The model is used to deduce critical support load and limiting column length for a given horizontal stress and support pressure.Considering the impact of the column effect,a method is proposed to determine the movement of the ground and caving area in a mine.After surface subsidence,the horizontal stress on a surrounding rock mass can be simplified to a cantilever beam mechanical model.Expressions for its bending fracture length are deduced,and a method is given to determine its stability.On this basis,an explanation for the large ground movement and subsidence scope was given.A case study shows that the damage effect of column and cantilever beam is significant for ground movement in metal-ore mine,and an appropriate correction value should be applied when designing for its angle of ground movements.展开更多
The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influen...The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.展开更多
Underground mining is going to be deeper gradually because near surface resources are going to be depleted. Therefore, risk of seismic events in underground mines is escalating. Additionally, existence of the large ra...Underground mining is going to be deeper gradually because near surface resources are going to be depleted. Therefore, risk of seismic events in underground mines is escalating. Additionally, existence of the large ratio of horizontal to vertical stress, could be a potential reason for high-stress condition and occurrence of dynamic activities. Depending on various parameters such as the level of induced stress, rock properties, etc., ground demand changes and it is difficult to estimate. On the other hand,under seismic condition, energy dissipation and deformation capacity of supports is the most important factors, however, rock support performance factors in dynamic conditions are still under investigation.Expanding the knowledge of reinforcement behaviour and capacity, specifically that of the rockbolt as a primary element in seismic conditions, would help to develop a suitable, safe and economic support design. This paper contains various methods to estimate ground demand including the intact rock properties approach, failure thickness and ejection velocity estimation, and rockburst damage potential method. It also covers measurement methods of rockbolts energy dissipation capacities such as drop test,blasting simulating, back calculation and momentum transfer measurement methods. A large-scale dynamic test rig is also explained. Based on the findings, a table and a graph to show the applicable range of each type of rockbolts were presented. Suitable rockbolt types for various ground energy demand and deformation capacity range were categorised in the table and the graph. The presented support selection method facilitates the selection of a suitable reinforcement system at the preliminary stages of design and guides the designer to adjust the support reinforcement system based on observed ground and support reaction.展开更多
This study proposes a novel approach to study stress field distribution and overlying ground pressure behavior in shallow seam mining in gully terrain.This approach combines numerical simulations and field tests based...This study proposes a novel approach to study stress field distribution and overlying ground pressure behavior in shallow seam mining in gully terrain.This approach combines numerical simulations and field tests based on the conditions of gully terrain in the Chuancao Gedan Mine.The effects of gully terrain on the in situ stress field of coal beds can be identified by the ratio of self-weight stress to vertical stress(η) at the location corresponding to the maximum vertical stress.Based on the function η =j(h),the effect of gully terrain on the stress field of overlying strata of the entire field can be characterized as a significantly affected area,moderately affected area,or non-affected area.Working face 6106 in the Chuancao Gedan Mine had a coal bed Jepth <80 m and was located in what was identified as a significantly affected area.Hence,mining may cause sliding of the gully slope and increased loading(including significant dynamic loading) on the roof strata.Field tests suggest that significant dynamic pressures were observed at the body and foot of the gully slope,and that dynamic loadings were observed upslope of the working face expansion,provided that the expanding direction of the working face is parallel to the gully.展开更多
On the basis of the analysis of coal bed gas pressure in deep mine, and the coal bed permeability ( k ) and the characteristic of adsorption parameter ( b ) changing with temperature, the author puts forward a new cal...On the basis of the analysis of coal bed gas pressure in deep mine, and the coal bed permeability ( k ) and the characteristic of adsorption parameter ( b ) changing with temperature, the author puts forward a new calculating method of gas content in coal seam influenced by in situ stress grads and ground temperature. At the same time, the contrast of the measuring results of coal bed gas pressure with the computing results of coal bed gas pressure and gas content in coal seam in theory indicate that the computing method can well reflect the authenticity of gas content in coal seam,and will further perfect the computing method of gas content in coal seam in theory,and have important value in theory on analyzing gas content in coal seam and forecasting distribution law of gas content in coal seam in deep mine.展开更多
The application of the finite layer & triangular prism element method to the 3D ground subsidence and stress analysis caused by mining is presented. The layer elements and the triangular prism elements have been a...The application of the finite layer & triangular prism element method to the 3D ground subsidence and stress analysis caused by mining is presented. The layer elements and the triangular prism elements have been alternatively used in the numerical simulation system, the displacement pattern, strain matrix, elastic matrix, stiffness matrix, load matrix and the stress matrix of the layer element and triangular prism element have been presented. By means of the Fortran90 programming language, a numerical simulation system based on finite layer & triangular prism element have been built up, and this system is suitable for subsidence prediction and stress analysis of all mining condition and mining methods. Comparing with the infinite element method, this approach dramatically reduces the size of the set of equations that need to be solved, and greatly reduces the amount of data preparation required. It not only saves the internal storage, and the computation time, but also decreases the cost.展开更多
buildings located at rock sites. Modelling wave propagation through soil medium helps to derive the primary and secondary wave velocities. Most of the time soil mediums are heterogeneous, layered and undergoes nonline...buildings located at rock sites. Modelling wave propagation through soil medium helps to derive the primary and secondary wave velocities. Most of the time soil mediums are heterogeneous, layered and undergoes nonlinear strains even under weak excitation. The equivalent linear approximation with one dimensional wave propagation is widely adopted for modeling earthquake excitation for layered soil. In this paper, importance of local soil effects, the process of wave propagation through three dimensional elastic medium, layered medium situated on rigid rock, attenuation of stress waves due to material damping, equivalent linear approximation, the concept of one dimensional wave propagation, and a case study of one dimensional wave propagation as a part of site-specific ground response analyses for Delhi region are included. The case study brings out the importance of carrying out site-specific ground response analyses of buildings considering the scenario earthquakes and actual soil conditions for Delhi region.展开更多
To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior a...To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.展开更多
基金Supported by the National Natural Science Foundation of China(Grant Nos.51734007,51704099 and 51604101)Program for Innovative Research Team in University of Ministry of Education of China(IRT_16R22)+1 种基金Key scientific research projects in Colleges and universities in Henan(Grant No.19A440003)the Opening Foundation of State Key Laboratory Cultivation Base for Gas Geology and Gas Control(Grant No.WS2017B14).
文摘The influence of ground stress was quantitatively analyzed on coal seam gas pressure and gas content in this paper.Mining activities in coal mine can result in stress concentration in the coal(rock)body around the mining space,but porosity of the coal seam would not change too much.Therefore,gas pressure and gas content in the coal seam are slightly affected.Studies showed that the free gas was gradually transformed into adsorbed gas,and the gas adsorption volume was small,and then gas pressure increases roughly linearly when the porosity decreased because of stress influence.Additionaly,when porosity of coal seam reduced to 40%,the amount of adsorbed gas accounted for no more than 10%of coal seam gas content,and the increase of gas pressure did not exceed 15%of the original gas pressure.
基金supported by the National Basic Research Program of China (No.2010CB226805)the National Natural Science Foundation of China (Nos.50874103 and 50974115)+1 种基金the Natural Science Foundation of Jiangsu Province (No.KB2008135)the State Key Laboratory Fund (No.SKLGDUEK 0905)
文摘We adopt the concept of generalized plane strain to model a roadway in a stress field.This can avoid limitations caused by simplifying the stress analysis as plane strain.FLAC3D was used to investigate the maximum tensile stress and displacement of a roadway in a known stress field for angles,α,between the roadway axial direction and the maximum principal stress of 0°,30°,45°,60° and 90°.This theory was applied to the analysis of an engineering case.The results indicate that stress and displacement of the surrounding rock increase as the angle,α,increases.This provides some significant guidance for a reasonable layout of roadways in a known stress field.
基金supported by the National Natural Science Foundation of China (No. 50874103)the National Basic Research Program of China (No. 2010CB226805)+1 种基金the Natural Science Foundation of Jiangsu Province (No. BK2008135)the Open Foundation of State Key Laboratory of Geomechanics and Deep Underground Engineering (No. SKLGDUEK0905)
文摘Ground stress is the fundamental cause of deformation and failure during underground structural engi- neering. Field stress measurements in the main coal bed in the Lüliang mining area were made by the bore hole, stress relief method. From these data the ground stress distribution of the mining area was obtained. The relationship between the horizontal principal stress and the deformation and failure of a roadway is discussed with an engineering example. The results indicate that horizontal stress dominates in the shallow crust in the Lüliang mining area. Roadways at different angles to the maximum principal stress have different levels of stress concentration. This leads to a significant difference in stability of the corresponding roadways. These research results provide an important criterion for determining roadway position and direction, stope layout, and roadway support design.
基金Projects 2007CB209400 supported by the National Basic Research Program of China50490273 by the National Natural Science Foundation of China
文摘Most of the coal reservoirs in China are of low-permeability, so hydraulic fracturing is widely used to improve the per- meability in the extraction of gas by ground drilling. The ground stress around the well was analyzed by using theory of elasticity. The pressure when the well fractured is formulated and the effect of ground stress on pressure is discussed. The effect of ground-stress-differences on hydraulic fracturing was analyzed by using the numerical software RFPA2D-Flow in reference to the tectonic stress in Jincheng coal area. The results show that: 1) the position where initial fracture appears is random and fracture branches emerge when the fractures expand if ground stresses in any two directions within a horizontal plane are equal; 2) other- wise, the fractures expand in general along the direction of maximum ground stress and the critical pressure decreases with in- creasing ground-stress-differences and 3) the preferred well-disposition pattern is diamond shaped. The preferred well spacing is 250 m×300 m. This study can provide a reference for the design of wells.
基金Innovative Research Groups of the National Natural Science Foundation of China (No.51021004)National Science Foundation of China (No. 51079096)Program for New Century Excellent Talents in University (No. NCET-08-0391)
文摘A new back-analysis method of ground stress is proposed with comprehensive consideration of influence of topography, geology and nonlinear physical mechanical properties of rock on ground stress. This method based on non-uniform rational B-spline (NURBS) technology provides the means to build a refined three-dimensional finite element model with more accurate meshing under complex terrain and geological conditions. Meanwhile, this method is a back-analysis of ground stress with combination of multivariable linear regression model and neural network (ANN) model. Firstly, the regression model is used to fit approximately boundary loads. Regarding the regressed loads as mean value, some sets of boundary loads with the same interval are constructed according to the principle of orthogonal design, to calculate the corresponding ground stress at the observation positions using finite element method. The results (boundary loads and the corresponding ground stress) are added to the samples for ANN training. And on this basis, an ANN model is established to implement higher precise back-analysis of initial ground stress. A practical application case shows that the relative error between the inversed ground stress and observed value is mostly less than 10 %, which can meet the need of engineering design and construction requirements.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.U1663205,51704191 and 51804194)the Shanghai Leading Academic Discipline Project(Grant No.S30106)+1 种基金the Shanghai Municipal Education Commission(Peak Discipline Construction Program)the Shanghai Sailing Program(Grant No.17YF1428000)。
文摘The situation of an off-center casing under non-uniform ground stress can occur in the process of drilling a salt-gypsum formation,and the related casing stress calculation has not yet been solved analytically. In addition,the experimental equipment in many cases cannot meet the actual conditions and the experimental cost is very high. These comprehensive factors cause the existing casing design to not meet the actual conditions and cause casing deformation,affecting the drilling operation in Tarim oil field. The finite element method is the only effective method to solve this problem at present,but the re-modelling process is time-consuming because of the changes in the parameters,such as the cement properties,casing centrality,and the casing size. In this article,an artificial intelligence method based on support vector machine(SVM) to predict the maximum stress of an offcenter casing under non-uniform ground stress has been proposed. After a program based on a radial basis function(RBF)-support vector regression(SVR)(ε-SVR) model was established and validated,we constructed a data sample with a capacity of 120 by using the finite element method,which could meet the demand of the nine-factor ε-SVR model to predict the maximum stress of the casing. The results showed that the artificial intelligence prediction method proposed in this manuscript had satisfactory prediction accuracy and could be effectively used to predict the maximum stress of an off-center casing under complex downhole conditions.
文摘In this paper, we discussed the influence of the initial tectonic stress on the relative measurement value of the ground stress when a long cylindrical straingauge is used in the viscoelastic media. We simulate the whole system consisting of the stratum, cement ring and the straingauge cylinder with a three layer medium model and obtain the solution of radial displacement on the inner wall of the straingauge under the action of initial tectonic stress by using the correspondence principle. The result showes: 1) The influence of initial stress making of the radial displacement on the inner wall of the straingauge increases gradually with time at a gradually reduced rate and tends to a certain value eventually; 2) The principal stress with a magnitude of [C 0+C 1 exp (- ω 1t)+ C 2 exp(- ω 2t )] σ i0 in the opposite direction of initial stress will be superimposed to the measuring result of stress change without considering the initial stress. where C 0, C 1, C 2 and ω 1, ω 2 are related only to the mechanical property of the stratum, σ i0 (i=1, 2) are the two principal components of the initial tectonic stress. It is pointed out that the initial tectonic stress affects obviously on the measurement of the relative change of ground stress in the cases of soft strata and high initial stress.
基金Project(51274188)supported by the National Natural Science Foundation of China
文摘When mining metal mines with steep structure planes by the caving method,there is a mechanical model in which the horizontal stress on the rock mass is simplified as a column before surface subsidence.The model is used to deduce critical support load and limiting column length for a given horizontal stress and support pressure.Considering the impact of the column effect,a method is proposed to determine the movement of the ground and caving area in a mine.After surface subsidence,the horizontal stress on a surrounding rock mass can be simplified to a cantilever beam mechanical model.Expressions for its bending fracture length are deduced,and a method is given to determine its stability.On this basis,an explanation for the large ground movement and subsidence scope was given.A case study shows that the damage effect of column and cantilever beam is significant for ground movement in metal-ore mine,and an appropriate correction value should be applied when designing for its angle of ground movements.
文摘The response of subsoil strata subjected to seismic excitations plays an important role in governing the response of the overlying superstructures at any site. Ground response analysis(GRA) helps to assess the influence of soil characteristics on the propagating seismic stress waves from the bedrock level to the ground surface during an earthquake. For the northeastern region of India, located in the highest seismic zone in the country, conducting an extensive GRA study is of prime importance. Conventionally, most of the GRA studies are carried out using the equivalent linear method, which, being a simplistic approach, cannot capture the nonlinear behavior of soil during seismic shaking. This paper presents the outcomes of a one-dimensional effective stress based nonlinear GRA conducted for Guwahati city(located in northeast India) incorporating the non-Masing load/unload/reload characteristics. The various ground response parameters evaluated from this study help in assessing the ground shaking, soil amplification, and site responses expected in this region. 2D contour maps, which are representative of the distribution of some of these parameters throughout Guwahati city, are also developed. The results presented herein can serve as guidelines for the design of foundations and superstructures in this region.
文摘Underground mining is going to be deeper gradually because near surface resources are going to be depleted. Therefore, risk of seismic events in underground mines is escalating. Additionally, existence of the large ratio of horizontal to vertical stress, could be a potential reason for high-stress condition and occurrence of dynamic activities. Depending on various parameters such as the level of induced stress, rock properties, etc., ground demand changes and it is difficult to estimate. On the other hand,under seismic condition, energy dissipation and deformation capacity of supports is the most important factors, however, rock support performance factors in dynamic conditions are still under investigation.Expanding the knowledge of reinforcement behaviour and capacity, specifically that of the rockbolt as a primary element in seismic conditions, would help to develop a suitable, safe and economic support design. This paper contains various methods to estimate ground demand including the intact rock properties approach, failure thickness and ejection velocity estimation, and rockburst damage potential method. It also covers measurement methods of rockbolts energy dissipation capacities such as drop test,blasting simulating, back calculation and momentum transfer measurement methods. A large-scale dynamic test rig is also explained. Based on the findings, a table and a graph to show the applicable range of each type of rockbolts were presented. Suitable rockbolt types for various ground energy demand and deformation capacity range were categorised in the table and the graph. The presented support selection method facilitates the selection of a suitable reinforcement system at the preliminary stages of design and guides the designer to adjust the support reinforcement system based on observed ground and support reaction.
基金supported by the Fundamental Research Funds for the Central Universities of China University of Mining and Technology(No.2014ZDPY21)
文摘This study proposes a novel approach to study stress field distribution and overlying ground pressure behavior in shallow seam mining in gully terrain.This approach combines numerical simulations and field tests based on the conditions of gully terrain in the Chuancao Gedan Mine.The effects of gully terrain on the in situ stress field of coal beds can be identified by the ratio of self-weight stress to vertical stress(η) at the location corresponding to the maximum vertical stress.Based on the function η =j(h),the effect of gully terrain on the stress field of overlying strata of the entire field can be characterized as a significantly affected area,moderately affected area,or non-affected area.Working face 6106 in the Chuancao Gedan Mine had a coal bed Jepth <80 m and was located in what was identified as a significantly affected area.Hence,mining may cause sliding of the gully slope and increased loading(including significant dynamic loading) on the roof strata.Field tests suggest that significant dynamic pressures were observed at the body and foot of the gully slope,and that dynamic loadings were observed upslope of the working face expansion,provided that the expanding direction of the working face is parallel to the gully.
文摘On the basis of the analysis of coal bed gas pressure in deep mine, and the coal bed permeability ( k ) and the characteristic of adsorption parameter ( b ) changing with temperature, the author puts forward a new calculating method of gas content in coal seam influenced by in situ stress grads and ground temperature. At the same time, the contrast of the measuring results of coal bed gas pressure with the computing results of coal bed gas pressure and gas content in coal seam in theory indicate that the computing method can well reflect the authenticity of gas content in coal seam,and will further perfect the computing method of gas content in coal seam in theory,and have important value in theory on analyzing gas content in coal seam and forecasting distribution law of gas content in coal seam in deep mine.
文摘The application of the finite layer & triangular prism element method to the 3D ground subsidence and stress analysis caused by mining is presented. The layer elements and the triangular prism elements have been alternatively used in the numerical simulation system, the displacement pattern, strain matrix, elastic matrix, stiffness matrix, load matrix and the stress matrix of the layer element and triangular prism element have been presented. By means of the Fortran90 programming language, a numerical simulation system based on finite layer & triangular prism element have been built up, and this system is suitable for subsidence prediction and stress analysis of all mining condition and mining methods. Comparing with the infinite element method, this approach dramatically reduces the size of the set of equations that need to be solved, and greatly reduces the amount of data preparation required. It not only saves the internal storage, and the computation time, but also decreases the cost.
文摘buildings located at rock sites. Modelling wave propagation through soil medium helps to derive the primary and secondary wave velocities. Most of the time soil mediums are heterogeneous, layered and undergoes nonlinear strains even under weak excitation. The equivalent linear approximation with one dimensional wave propagation is widely adopted for modeling earthquake excitation for layered soil. In this paper, importance of local soil effects, the process of wave propagation through three dimensional elastic medium, layered medium situated on rigid rock, attenuation of stress waves due to material damping, equivalent linear approximation, the concept of one dimensional wave propagation, and a case study of one dimensional wave propagation as a part of site-specific ground response analyses for Delhi region are included. The case study brings out the importance of carrying out site-specific ground response analyses of buildings considering the scenario earthquakes and actual soil conditions for Delhi region.
基金Project (07JJ4015) supported by the Natural Science Foundation of Hunan Province, China
文摘To discuss the soil arching effect on the load transferring model and sharing ratios by the piles and inter-pile subsoil in the bidirectionally reinforced composite ground, the forming mechanism, mechanical behavior and its effect factors were discussed in detail. Then, the unified strength theory was introduced to set up the elastoplastic equilibrium differential equation of the subsoil under the limit equilibrium state. And from the equation, the solutions were derived with the corresponding formulas presented to calculate the earth pressure over and beneath the horizontal reinforced cushion or pillow, the stress of inter-pile subsoil and the pile-soil stress ratio. Based on the obtained solutions and measured data from an engineering project, the influence rules by the soil property parameters (i.e., the cohesion c and internal friction angle φ) and pile spacing on the pile-soil stress ratio n were discussed respectively. The results show that to improve the load sharing ratio by the piles, the more effective means for filling materials with a larger value of φ is to increase the ratio of pile cap size to spacing, while to reduce the pile spacing properly and increase the value of cohesion c is advisable for those filling materials with a smaller value of φ.