To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the pa...To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the paper conducted the numerical simulation of pre-drainage gas in drillings along coal seam, studied the relationship of adsorption constants and permeability, gas pressure, and effective drainage radius of coal seams, and applied the approach to the layout of pre-drainage gas drillings in coal seams. The results show that the permeability of coal seams is on the gradual increase with time, which is divided into three sections according to the increase rate: the drainage time 0–30 d is the sharp increase section;30–220 d is the gradual increase section; and the time above 200 d is the stable section. The permeability of coal seams is in negative linear and positive exponent relation with volume adsorption constant VLand pressure adsorption constant PL, respectively. The effective drainage radius is in negative linear relation with VLand in positive exponent relation with PL. Compared with the former design scheme, the engineering quantity of drilling could be reduced by 25%.展开更多
The efficiency of excavation a mining tunnel is definitely linked with modes of cut-holes. According to experience and methods of engineering analogy, the double-wedge cut, the 9-hole cut and the single spiral cut wer...The efficiency of excavation a mining tunnel is definitely linked with modes of cut-holes. According to experience and methods of engineering analogy, the double-wedge cut, the 9-hole cut and the single spiral cut were determined originally by considering the production conditions and blasting environment of the mining tunnels of the-74 m horizontal in the Da-ye iron mine. Based on acquired modes of cut-holes, the effect of the cut was studied, on the one hand, by a numerical simulation method with the aid of LS-DYNA3D, a nonlinear dynamic finite element program; on the other hand, a spot experiment was carried out in the mining tunnels. Both the numerical simulation and the spot experiment demonstrated and agreed that a single spiral cut provides the optimum excavation effect.展开更多
The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) appr...The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) approach that we have chosen has the advantage of being media independent.Beginning with the Maxwell equations in a two-dimensional structure,numerical formulas of finite-difference time-domain(FDTD) method with CPML boundary condition for transverse electric(TE) or transverse magnetic(TM) wave are presented in details.Also,there are three models for borehole-GPR simulation.By analyzing the simulation results,the features of targets in GPR are obtained,which can provide a better interpretation of real radar data.The results show that CPML is well suited for the simulation of borehole-GPR.展开更多
A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil archi...A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.展开更多
Based on the basic theory of gas seepage and coal seam deformation, using the numerical simulation method, this paper established the gas-solid coupling model of gas drainage from borehole. Using multi-physical coupli...Based on the basic theory of gas seepage and coal seam deformation, using the numerical simulation method, this paper established the gas-solid coupling model of gas drainage from borehole. Using multi-physical coupling analysis software, the authors studied the stress change conditions around the drainage borehole, the influence of the gas drainage effect caused by the drilling gap, and the gas drainage effect under the conditions of different borehole radius and different permeabilities. The results show that the effective drainage radius is 1.03 m during 30 days of drainage. The effect of the diameter change of the drainage borehole is limited, but the influence of coal seam permeability is much bigger. After the same drainage period, the greater the permeability of coal seam is, the bigger the drainage radius is. For a low permeability coal seam, coal miners should take pressure-relief measures and increase the permeability to improve the drainage effects before draining gas through drilling.展开更多
基金Financial support for this work,provided by the National Natural Science Foundation of China(Nos.51327007,51104118 and51204134)Shaanxi Province Youth Science and Technology Star Project of China(2014KJXX69)
文摘To determine reasonable distance of gas pre-drainage drillings in coal seams, a solid–gas coupling model that takes gas adsorption effect into account was constructed. In view of different adsorption constants,the paper conducted the numerical simulation of pre-drainage gas in drillings along coal seam, studied the relationship of adsorption constants and permeability, gas pressure, and effective drainage radius of coal seams, and applied the approach to the layout of pre-drainage gas drillings in coal seams. The results show that the permeability of coal seams is on the gradual increase with time, which is divided into three sections according to the increase rate: the drainage time 0–30 d is the sharp increase section;30–220 d is the gradual increase section; and the time above 200 d is the stable section. The permeability of coal seams is in negative linear and positive exponent relation with volume adsorption constant VLand pressure adsorption constant PL, respectively. The effective drainage radius is in negative linear relation with VLand in positive exponent relation with PL. Compared with the former design scheme, the engineering quantity of drilling could be reduced by 25%.
文摘The efficiency of excavation a mining tunnel is definitely linked with modes of cut-holes. According to experience and methods of engineering analogy, the double-wedge cut, the 9-hole cut and the single spiral cut were determined originally by considering the production conditions and blasting environment of the mining tunnels of the-74 m horizontal in the Da-ye iron mine. Based on acquired modes of cut-holes, the effect of the cut was studied, on the one hand, by a numerical simulation method with the aid of LS-DYNA3D, a nonlinear dynamic finite element program; on the other hand, a spot experiment was carried out in the mining tunnels. Both the numerical simulation and the spot experiment demonstrated and agreed that a single spiral cut provides the optimum excavation effect.
基金Project(41174061) supported by the National Natural Science Foundation of ChinaProject(2011QNZT011) supported by the Free Exploration Program of Central South University,China
文摘The absorbing boundary is the key in numerical simulation of borehole radar.Perfect match layer(PML) was chosen as the absorbing boundary in numerical simulation of GPR.But CPML(convolutional perfect match layer) approach that we have chosen has the advantage of being media independent.Beginning with the Maxwell equations in a two-dimensional structure,numerical formulas of finite-difference time-domain(FDTD) method with CPML boundary condition for transverse electric(TE) or transverse magnetic(TM) wave are presented in details.Also,there are three models for borehole-GPR simulation.By analyzing the simulation results,the features of targets in GPR are obtained,which can provide a better interpretation of real radar data.The results show that CPML is well suited for the simulation of borehole-GPR.
文摘A reliability based analysis method for a drilled shaft stabilized slope system is presented in this paper. The drilled shaft stabilization mechanisms for the slope were treated as the drilled shaft induced soil arching, which was quantified by the load transfer factor in the limited equilibrium analysis. However, due to the inherent uncertainties of the soil properties and the model error of the semi-empirical load transfer equation, an extension modification of the deterministic method into a probabilistic method is developed in this paper. The MCS （Monte Carlo simulation） with log-normal random variables has been employed to calculate the probability of failure （Pf） for the drilled shafts/slope system. The developed theories were coded into a computer program for analyzing complex slope geometry and slope profile conditions. Finally, a case study has been performed to illustrate the application analysis of the developed probability approach in drilled shafts/slope system.
基金Supported by the National Natural Science Foundation of China （51174212） the Program for New Century Excellent Talents in University of China （NCET-10-0724） the Fundamental Research Funds for the Central Universities （2010QZ05）
文摘Based on the basic theory of gas seepage and coal seam deformation, using the numerical simulation method, this paper established the gas-solid coupling model of gas drainage from borehole. Using multi-physical coupling analysis software, the authors studied the stress change conditions around the drainage borehole, the influence of the gas drainage effect caused by the drilling gap, and the gas drainage effect under the conditions of different borehole radius and different permeabilities. The results show that the effective drainage radius is 1.03 m during 30 days of drainage. The effect of the diameter change of the drainage borehole is limited, but the influence of coal seam permeability is much bigger. After the same drainage period, the greater the permeability of coal seam is, the bigger the drainage radius is. For a low permeability coal seam, coal miners should take pressure-relief measures and increase the permeability to improve the drainage effects before draining gas through drilling.
