It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the mi...It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the microscopic parameters of parallel-bonded particle model for three-dimensional discrete element particle flow code(PFC3D).Variation ranges of microscopic of the microscopic parameters are created by analyzing the effects of microscopic parameters on macroscopic parameters(elastic modulus E,Poisson ratio v,uniaxial compressive strengthσc,and ratio of crack initial stress to uniaxial compressive strengthσci/σc)in order to obtain the actual uniform design talbe.The calculation equations of the microscopic and macroscopic parameters of rock materials can be established by the actual uniform design table and the regression analysis and thus the PFC3D microscopic parameters can be quantitatively determined.The PFC3D simulated results of the intact and pre-cracked rock specimens under uniaxial and triaxial compressions(including the macroscopic mechanical parameters,stress−strain curves and failure process)are in good agreement with experimental results,which can prove the validity of the calculation equations of microscopic and macroscopic parameters.展开更多
Direct shear tests were conducted on the rock joints under constant normal load(CNL), while the acoustic emission(AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shea...Direct shear tests were conducted on the rock joints under constant normal load(CNL), while the acoustic emission(AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shearing, the surfaces of rock joints were measured by the Talysurf CLI 2000. By correlating the AE events with the shear stress-shear displacement curve, one can observe four periods of the whole course of shearing of rock joints. By the contrast of AE location and actual damage zone, it is elucidated that the AE event is related to the morphology of the joint. With the increase of shearing times, the shear behavior of rock joints gradually presents from the response of brittle behavior to that of ductile behavior. By combining the results of topography measurement, four morphological parameters of joint surface, S p(the maximum height of joint surface), N(number of islands), A(projection area) and V(volume of joint) were introduced, which decrease with shearing. Both the joint roughness coefficient(JRC) and joint matching coefficient(JMC) drop with shearing, and the shear strength of rock joints can be predicted by the JRC-JMC model. It establishes the relationship between micro-topography and macroscopic strength, which have the same change rule with shearing.展开更多
以非饱和材料离散元试样生成法为基础,对PFC^(3D)(Particle Flow Code in Three Dimensions)颗粒流离散元分析程序进行改进,建立了同时适用于黏土与砂土的单轴拉伸离散元模型,并对单轴拉伸应力-位移关系及单轴抗拉强度开展研究;探究了...以非饱和材料离散元试样生成法为基础,对PFC^(3D)(Particle Flow Code in Three Dimensions)颗粒流离散元分析程序进行改进,建立了同时适用于黏土与砂土的单轴拉伸离散元模型,并对单轴拉伸应力-位移关系及单轴抗拉强度开展研究;探究了不同细观参数对土体拉伸破坏的影响,并以单轴抗拉强度为桥梁,建立了饱和度与颗粒间黏结强度的关系;进行了不同初始孔隙比和饱和度下黏土与砂土的单轴拉伸数值模拟,研究了非饱和土的拉伸特性及利用离散元模拟非饱和土的适用性.结果表明:在法向黏结强度、切向黏结强度、杨氏模量、刚度比、摩擦系数这5个细观参数中,法向黏结强度对抗拉强度的影响最大,切向黏结强度、杨氏模量、刚度比次之,而摩擦系数的影响最小;黏土的单轴抗拉强度随饱和度的增加呈现先增大后减小的趋势,并且单轴抗拉强度在左侧(干侧)的增加速度大于在右侧(湿侧)的减小速度;砂土的单轴抗拉强度随着饱和度的增加表现出“增大-减小-增大”的规律;模拟所得规律与室内实验结果具有较高的一致性,验证了在模拟非饱和材料单轴拉伸特性时该离散元模型及数值分析程序的适用性.展开更多
基金Projects(51474251,51874351)supported by the National Natural Science Foundation,China。
文摘It is important to calibrate micro-parameters for applying partied flow code(PFC)to study mechanical characteristics and failure mechanism of rock materials.Uniform design method is firstly adopted to determine the microscopic parameters of parallel-bonded particle model for three-dimensional discrete element particle flow code(PFC3D).Variation ranges of microscopic of the microscopic parameters are created by analyzing the effects of microscopic parameters on macroscopic parameters(elastic modulus E,Poisson ratio v,uniaxial compressive strengthσc,and ratio of crack initial stress to uniaxial compressive strengthσci/σc)in order to obtain the actual uniform design talbe.The calculation equations of the microscopic and macroscopic parameters of rock materials can be established by the actual uniform design table and the regression analysis and thus the PFC3D microscopic parameters can be quantitatively determined.The PFC3D simulated results of the intact and pre-cracked rock specimens under uniaxial and triaxial compressions(including the macroscopic mechanical parameters,stress−strain curves and failure process)are in good agreement with experimental results,which can prove the validity of the calculation equations of microscopic and macroscopic parameters.
基金Projects(51274249,51174228)supported by the National Natural Science Foundation of China
文摘Direct shear tests were conducted on the rock joints under constant normal load(CNL), while the acoustic emission(AE) signals generated during shear tests were monitored with PAC Micro-II system. Before and after shearing, the surfaces of rock joints were measured by the Talysurf CLI 2000. By correlating the AE events with the shear stress-shear displacement curve, one can observe four periods of the whole course of shearing of rock joints. By the contrast of AE location and actual damage zone, it is elucidated that the AE event is related to the morphology of the joint. With the increase of shearing times, the shear behavior of rock joints gradually presents from the response of brittle behavior to that of ductile behavior. By combining the results of topography measurement, four morphological parameters of joint surface, S p(the maximum height of joint surface), N(number of islands), A(projection area) and V(volume of joint) were introduced, which decrease with shearing. Both the joint roughness coefficient(JRC) and joint matching coefficient(JMC) drop with shearing, and the shear strength of rock joints can be predicted by the JRC-JMC model. It establishes the relationship between micro-topography and macroscopic strength, which have the same change rule with shearing.
文摘以非饱和材料离散元试样生成法为基础,对PFC^(3D)(Particle Flow Code in Three Dimensions)颗粒流离散元分析程序进行改进,建立了同时适用于黏土与砂土的单轴拉伸离散元模型,并对单轴拉伸应力-位移关系及单轴抗拉强度开展研究;探究了不同细观参数对土体拉伸破坏的影响,并以单轴抗拉强度为桥梁,建立了饱和度与颗粒间黏结强度的关系;进行了不同初始孔隙比和饱和度下黏土与砂土的单轴拉伸数值模拟,研究了非饱和土的拉伸特性及利用离散元模拟非饱和土的适用性.结果表明:在法向黏结强度、切向黏结强度、杨氏模量、刚度比、摩擦系数这5个细观参数中,法向黏结强度对抗拉强度的影响最大,切向黏结强度、杨氏模量、刚度比次之,而摩擦系数的影响最小;黏土的单轴抗拉强度随饱和度的增加呈现先增大后减小的趋势,并且单轴抗拉强度在左侧(干侧)的增加速度大于在右侧(湿侧)的减小速度;砂土的单轴抗拉强度随着饱和度的增加表现出“增大-减小-增大”的规律;模拟所得规律与室内实验结果具有较高的一致性,验证了在模拟非饱和材料单轴拉伸特性时该离散元模型及数值分析程序的适用性.
