After the excavation of deep mining tunnels and underground caverns,the stability of surrounding rock controlled by structural planes is prone to structural damage and even engineering disasters due to three-dimension...After the excavation of deep mining tunnels and underground caverns,the stability of surrounding rock controlled by structural planes is prone to structural damage and even engineering disasters due to three-dimensional stress redistribution and multi-directional dynamic construction interference.However,the shear mechanical behavior,fracture evolution mechanism and precursor characteristics of rockmass under true triaxial stress and multi-directional coupling disturbance are not unclear.Therefore,this study carried out true triaxial shear tests on limestone intermittent structural planes under uni-,bi-and tri-directional coupling disturbances to analyze its mechanical behavior,fracture evolution mechanism and precursor characteristics.The results show that as the disturbance direction increase,the shear strength of limestone generally decreases,while the roughness of structural planes and the degree of anisotropy generally exhibit an increasing trend.The proportion of shear cracks on the structural plane increases with the increase of shear stress.The disturbance strain rate before failure shows a U-shaped trend.Near to disturbance failure,there were more high-energy and high-amplitude acoustic emission events near the structural plane,and b-value drops rapidly below 1,while lgN/b ratio increased to above 3.These findings provide experimental recognition and theoretical support for assessing the stability of rockmass under blasting excavation.展开更多
On the basis of Betti's theorem,the constitutive relation of multi- crack rockmass which considers the effect of crack-closure is developed in this paper. Meanwhile,based on mathematical elasticity,the paper gives...On the basis of Betti's theorem,the constitutive relation of multi- crack rockmass which considers the effect of crack-closure is developed in this paper. Meanwhile,based on mathematical elasticity,the paper gives an analytical formula for the compression transmitting coefficient and the shearing transmitting coefficient. A damage evolution equation of rock-mass is presented and an engineering application is given as well.展开更多
Post failure rheology, as an important deformable behavior of average to very poor rockmass,is discussed in this paper. Three kinds of deformations, transition deformation, post failure rheological deformation and swe...Post failure rheology, as an important deformable behavior of average to very poor rockmass,is discussed in this paper. Three kinds of deformations, transition deformation, post failure rheological deformation and swelling deformation, are also introduced for they are totally different from that of traditional concepts. Transition and post failure deformations are sensitive to the environmental factors, and need to be studied in the future.展开更多
On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sichuan, China. This devastating earthquake led to a heavy death toll of greater than 80,000. The seismic origin of this ear...On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sichuan, China. This devastating earthquake led to a heavy death toll of greater than 80,000. The seismic origin of this earthquake is currently hotly debated. We suppose that it is a special type of intraplate earthquake called an active-nappe-type earthquake. Using a holistic methodology, incorporating rockmass structure cybernetics and Byerlee's law, we present a comprehensive study on the geological origin of macroseisms in the Longmen Shan area and the seismic origin of the 2008 Wenchuan earthquake. Previous studies of neotectonic activity indicate that the Longmen Shan nappe moves at a rate of 1~3 mm/yr, due to horizontal compressive stress from the Tibetan Plateau. The difference between movement rates in the Bayankala block, Longmen Shan nappe and Sichuan Basin cause slow shear stress and strain accumulation in the Longmen Shan nappe. It is exhibited a relatively simple linear relations for the shear strength and the buried depth of the structural planes, and the detachment layer of the nappe has a higher shearing-sliding strength compared to the overlying fault planes and the underlying ductile shear belts, thus making it more prone to stick-slip deformation. Therefore, the detachment layer was the main section responsible for the Wenchuan earthquake. The initial rupture burst in the detachment layer under the Yingxiu-Beichuan fault, the rupture area nearly 1.4454 × 104 km2,encompassed the cross point of the Yingxiu and the Anxian-Guanxian faults with the detachment layer, then caused the Yingxiu-Beichuan and Anxian-Guanxian faults took an active part in this earthquake, so this earthquake might consist of three chain-like earthquake stages, totally increasing the duration of this earthquake an unusually large amount, to 120 s. The focal depth spanned range of 10-20km,consistent with the observed result of this focal depth by several agencies.展开更多
The desired economics of hard rock surface mining is mainly determined by the parameters of process design which minimize the overall cost per tonne of the rock mined in drilling, blasting, handling and primary crushi...The desired economics of hard rock surface mining is mainly determined by the parameters of process design which minimize the overall cost per tonne of the rock mined in drilling, blasting, handling and primary crushing in given rockmass conditions. The most effective parameters of process design could be established based on the regression models of the cumulative influence of rockmass and mine design parameters on the overall cost per tonne of the rock drilled, blasted, handled and crushed. These models could be developed from the huge data accumulated worldwide on the costs per tonne of hard rock surface mining in drilling, blasting, handling and primary crushing vs the parameters of rockmass and mine design. This paper only dwelt on the development of regression models for oversize generation, blasthole productivity and blasting cost for iron ore surface mines, whose data is available. The SPSS standard statistical correlation – regression analysis software was used in the analysis. Interpretation of the models generated shows that the individual effects of the determinant rockmass and blast design parameters on oversize generation, blasthole productivity and blasting cost are all in compliance with the findings of other researchers and the theory of explosive rock fragmentation and could be used for the estimation of oversize generation, blasthole productivity and blasting cost in rockmass and blast design conditions similar to those of the iron ore surface mines examined in this study. However, the regression models obtained here could not be used alone for the optimization of blast design because most of the determinant parameters also have conflicting effect on the other processes of drilling, handling and primary crushing the blasted rock. Also, the quality and content of the regression models could be enhanced further by increasing the content of rockmass and blast design parameters and the volume of data considered in the regression analysis.展开更多
The strength of rockmass from two aspects is analyzed.Firstly,the strength of the rockmass is mainly controlled by the critical stress value of rock,and the contribution of joints is to increase the effective stresses...The strength of rockmass from two aspects is analyzed.Firstly,the strength of the rockmass is mainly controlled by the critical stress value of rock,and the contribution of joints is to increase the effective stresses of rock and to decrease the damage strength of rockmass according to the macro damage mechanics of rockmass.Secondly,the strength of rockmass is mainly controlled by the fracture strength of joints.Based on the comprehensive analysis and comparison for the damage strength of rockmass and the fracture strength of joints,a composite damage theory of rockmass may be established.展开更多
A parametric study was conducted to determine the influence of different bolt parameters(bolt length and diameter)on the maximum induced boundary displacements in jointed rockmass,using a numerical method based on fin...A parametric study was conducted to determine the influence of different bolt parameters(bolt length and diameter)on the maximum induced boundary displacements in jointed rockmass,using a numerical method based on finite element code.Three different types of jointed systems(Type A,Type B,and Type C)were considered and analyzed.Type A displays normal joint closure,Type B demonstrates a combination of normal and shear joint closure,and in Type C,the majority of the joint is loaded in shear condition.The ground surface settlement profiles for these three joint systems,under unsupported conditions,are presented in this work.For the same rockmass properties,the cases in Type A and Type B exhibit the maximum and minimum settlement,respectively.For each joint type,the effect of variable bolt parameters on the tunnel boundary is studied in terms of the total displacement.The simulation results confirm that an increase in the bolt length does not significantly reduce the boundary displacement,whereas an increase in the bolt diameter substantially reduces the tunnel boundary displacement.展开更多
岩溶洼地或冲沟汇集区为抽蓄工程建设提供了天然的有利地形条件,减少开挖量及建设成本;但此处强烈的岩溶作用将孕育多种潜在的工程地质问题,不利于工程建设;合理地评估岩溶区岩体完整程度和溶蚀程度是其中的关键问题.为克服评估过程中...岩溶洼地或冲沟汇集区为抽蓄工程建设提供了天然的有利地形条件,减少开挖量及建设成本;但此处强烈的岩溶作用将孕育多种潜在的工程地质问题,不利于工程建设;合理地评估岩溶区岩体完整程度和溶蚀程度是其中的关键问题.为克服评估过程中指标测定条件非简易满足、重复琐碎耗精力和区分精细度不够等问题,以秭归岩溶区某抽水蓄能工程为例,利用多源勘察信息,包括钻孔岩芯、钻孔声波和钻孔电视影像,三者协同互补,揭示了研究区各地层岩体完整与溶蚀程度规律,据此明确各地层岩体地质特点,再根据地层岩体地质特点不同赋予地层标签,以地层标签和岩体声波波速数据为输入,采用加权随机森林方法(weighted random forests,WRF),由此提出了一套适用于岩溶区岩体完整程度和溶蚀程度的多源信息融合评估方法.结果表明:相同位置的各信息相互关联,只因勘察手段和信息来源不同,信息的呈现形式存在差异;研究区各地层岩体的地质特点有很大差别,相应的各勘察手段信息的特征表现不尽相同,这影响我们利用多源勘察信息对岩体完整和溶蚀程度的评估.通过1073个样本训练并用118个样本测试,训练集/测试集完整程度评估吻合率达95.67%/94.92%,溶蚀程度评估测试集吻合率达98.02%/97.46%,且与野外针对性复勘校核结果吻合良好.与传统方法相比,本文方法综合利用了多源勘察信息,通过地层标签将各地层岩体地质特点融入岩体完整和溶蚀程度评估,更加高效、自动化与精细准确,绕开了传统方法的固有问题,便于岩溶区抽蓄工程岩体完整和溶蚀程度分级评价应用.展开更多
基金support received from the National Natural Science Foundation of China(Nos.52274145,52469019,and 52109119)the Guangxi Natural Science Foundation(No.2025GXNSFAA069165)the Chinese Postdoctoral Science Fund Project(No.2022M723408).
文摘After the excavation of deep mining tunnels and underground caverns,the stability of surrounding rock controlled by structural planes is prone to structural damage and even engineering disasters due to three-dimensional stress redistribution and multi-directional dynamic construction interference.However,the shear mechanical behavior,fracture evolution mechanism and precursor characteristics of rockmass under true triaxial stress and multi-directional coupling disturbance are not unclear.Therefore,this study carried out true triaxial shear tests on limestone intermittent structural planes under uni-,bi-and tri-directional coupling disturbances to analyze its mechanical behavior,fracture evolution mechanism and precursor characteristics.The results show that as the disturbance direction increase,the shear strength of limestone generally decreases,while the roughness of structural planes and the degree of anisotropy generally exhibit an increasing trend.The proportion of shear cracks on the structural plane increases with the increase of shear stress.The disturbance strain rate before failure shows a U-shaped trend.Near to disturbance failure,there were more high-energy and high-amplitude acoustic emission events near the structural plane,and b-value drops rapidly below 1,while lgN/b ratio increased to above 3.These findings provide experimental recognition and theoretical support for assessing the stability of rockmass under blasting excavation.
基金The project supported by the National Natural Science Foundation of China(59493600 and 59939190)
文摘On the basis of Betti's theorem,the constitutive relation of multi- crack rockmass which considers the effect of crack-closure is developed in this paper. Meanwhile,based on mathematical elasticity,the paper gives an analytical formula for the compression transmitting coefficient and the shearing transmitting coefficient. A damage evolution equation of rock-mass is presented and an engineering application is given as well.
文摘Post failure rheology, as an important deformable behavior of average to very poor rockmass,is discussed in this paper. Three kinds of deformations, transition deformation, post failure rheological deformation and swelling deformation, are also introduced for they are totally different from that of traditional concepts. Transition and post failure deformations are sensitive to the environmental factors, and need to be studied in the future.
文摘On 12 May 2008, the magnitude 8.0 Wenchuan Earthquake occurred along the Longmen Shan nappe, Sichuan, China. This devastating earthquake led to a heavy death toll of greater than 80,000. The seismic origin of this earthquake is currently hotly debated. We suppose that it is a special type of intraplate earthquake called an active-nappe-type earthquake. Using a holistic methodology, incorporating rockmass structure cybernetics and Byerlee's law, we present a comprehensive study on the geological origin of macroseisms in the Longmen Shan area and the seismic origin of the 2008 Wenchuan earthquake. Previous studies of neotectonic activity indicate that the Longmen Shan nappe moves at a rate of 1~3 mm/yr, due to horizontal compressive stress from the Tibetan Plateau. The difference between movement rates in the Bayankala block, Longmen Shan nappe and Sichuan Basin cause slow shear stress and strain accumulation in the Longmen Shan nappe. It is exhibited a relatively simple linear relations for the shear strength and the buried depth of the structural planes, and the detachment layer of the nappe has a higher shearing-sliding strength compared to the overlying fault planes and the underlying ductile shear belts, thus making it more prone to stick-slip deformation. Therefore, the detachment layer was the main section responsible for the Wenchuan earthquake. The initial rupture burst in the detachment layer under the Yingxiu-Beichuan fault, the rupture area nearly 1.4454 × 104 km2,encompassed the cross point of the Yingxiu and the Anxian-Guanxian faults with the detachment layer, then caused the Yingxiu-Beichuan and Anxian-Guanxian faults took an active part in this earthquake, so this earthquake might consist of three chain-like earthquake stages, totally increasing the duration of this earthquake an unusually large amount, to 120 s. The focal depth spanned range of 10-20km,consistent with the observed result of this focal depth by several agencies.
文摘The desired economics of hard rock surface mining is mainly determined by the parameters of process design which minimize the overall cost per tonne of the rock mined in drilling, blasting, handling and primary crushing in given rockmass conditions. The most effective parameters of process design could be established based on the regression models of the cumulative influence of rockmass and mine design parameters on the overall cost per tonne of the rock drilled, blasted, handled and crushed. These models could be developed from the huge data accumulated worldwide on the costs per tonne of hard rock surface mining in drilling, blasting, handling and primary crushing vs the parameters of rockmass and mine design. This paper only dwelt on the development of regression models for oversize generation, blasthole productivity and blasting cost for iron ore surface mines, whose data is available. The SPSS standard statistical correlation – regression analysis software was used in the analysis. Interpretation of the models generated shows that the individual effects of the determinant rockmass and blast design parameters on oversize generation, blasthole productivity and blasting cost are all in compliance with the findings of other researchers and the theory of explosive rock fragmentation and could be used for the estimation of oversize generation, blasthole productivity and blasting cost in rockmass and blast design conditions similar to those of the iron ore surface mines examined in this study. However, the regression models obtained here could not be used alone for the optimization of blast design because most of the determinant parameters also have conflicting effect on the other processes of drilling, handling and primary crushing the blasted rock. Also, the quality and content of the regression models could be enhanced further by increasing the content of rockmass and blast design parameters and the volume of data considered in the regression analysis.
文摘The strength of rockmass from two aspects is analyzed.Firstly,the strength of the rockmass is mainly controlled by the critical stress value of rock,and the contribution of joints is to increase the effective stresses of rock and to decrease the damage strength of rockmass according to the macro damage mechanics of rockmass.Secondly,the strength of rockmass is mainly controlled by the fracture strength of joints.Based on the comprehensive analysis and comparison for the damage strength of rockmass and the fracture strength of joints,a composite damage theory of rockmass may be established.
文摘A parametric study was conducted to determine the influence of different bolt parameters(bolt length and diameter)on the maximum induced boundary displacements in jointed rockmass,using a numerical method based on finite element code.Three different types of jointed systems(Type A,Type B,and Type C)were considered and analyzed.Type A displays normal joint closure,Type B demonstrates a combination of normal and shear joint closure,and in Type C,the majority of the joint is loaded in shear condition.The ground surface settlement profiles for these three joint systems,under unsupported conditions,are presented in this work.For the same rockmass properties,the cases in Type A and Type B exhibit the maximum and minimum settlement,respectively.For each joint type,the effect of variable bolt parameters on the tunnel boundary is studied in terms of the total displacement.The simulation results confirm that an increase in the bolt length does not significantly reduce the boundary displacement,whereas an increase in the bolt diameter substantially reduces the tunnel boundary displacement.
文摘岩溶洼地或冲沟汇集区为抽蓄工程建设提供了天然的有利地形条件,减少开挖量及建设成本;但此处强烈的岩溶作用将孕育多种潜在的工程地质问题,不利于工程建设;合理地评估岩溶区岩体完整程度和溶蚀程度是其中的关键问题.为克服评估过程中指标测定条件非简易满足、重复琐碎耗精力和区分精细度不够等问题,以秭归岩溶区某抽水蓄能工程为例,利用多源勘察信息,包括钻孔岩芯、钻孔声波和钻孔电视影像,三者协同互补,揭示了研究区各地层岩体完整与溶蚀程度规律,据此明确各地层岩体地质特点,再根据地层岩体地质特点不同赋予地层标签,以地层标签和岩体声波波速数据为输入,采用加权随机森林方法(weighted random forests,WRF),由此提出了一套适用于岩溶区岩体完整程度和溶蚀程度的多源信息融合评估方法.结果表明:相同位置的各信息相互关联,只因勘察手段和信息来源不同,信息的呈现形式存在差异;研究区各地层岩体的地质特点有很大差别,相应的各勘察手段信息的特征表现不尽相同,这影响我们利用多源勘察信息对岩体完整和溶蚀程度的评估.通过1073个样本训练并用118个样本测试,训练集/测试集完整程度评估吻合率达95.67%/94.92%,溶蚀程度评估测试集吻合率达98.02%/97.46%,且与野外针对性复勘校核结果吻合良好.与传统方法相比,本文方法综合利用了多源勘察信息,通过地层标签将各地层岩体地质特点融入岩体完整和溶蚀程度评估,更加高效、自动化与精细准确,绕开了传统方法的固有问题,便于岩溶区抽蓄工程岩体完整和溶蚀程度分级评价应用.
