The experimental results of 3-D fracture under compression are introduced in brief and the theory of stress criterion of 3-D fracture is studied. Methods to imitate initial fractures are developed. It is pointed that ...The experimental results of 3-D fracture under compression are introduced in brief and the theory of stress criterion of 3-D fracture is studied. Methods to imitate initial fractures are developed. It is pointed that there are important defects in the extreme value （EV） method ever proposed by Palaniswamy and Knauss. The major defect lies in that only two Euler angles （2EA） are considered, but another one is neglected. If the variation of all the three Euler angles （3EA） are considered, one can get better result which is consistent with the observation of faulting that extends on curved surfaces but not on planes. The method of evaluating maximal normal stress direction vector （NSDV） is proposed and further proved to be equivalent to the 3EA method. It is proved that the NSDV method can be further optimized to the method of composition of the first principal differential plane （CFPDP）. The results from CFPDP method can fit the curved surfaces of initial growth observed in the experiments of 3-D fracture. The CFPDP method can also be used to interpret the 3-D fractures of the slipping section between the asperities in the buried fault plane that is modeled as ellipse crack. The results of 3-D fracture can be applied to interpreting the related problems of faulting including the mechanism of a lot of shatter rocks with different dimensions, the cause of earthquakes occurred at the edge of plate under low shear stress, and the mechanism of anisotropy caused by the extensive dilatancy anisotropy （EDA） cracks.展开更多
Dynamic strength parameters are extensively used in mining engineering and rock mechanics.However,there are no widely accepted dynamic failure models for rocks.In this study,the dynamic punching shear strength,uniaxia...Dynamic strength parameters are extensively used in mining engineering and rock mechanics.However,there are no widely accepted dynamic failure models for rocks.In this study,the dynamic punching shear strength,uniaxial compressive strength(UCS) and tensile strength of fine-grained Fangshan marble(FM)are first measured by using a split Hopkinson pressure bar(SHPB) system.The pulse-shaping technique is then implemented to maintain the dynamic force balance in SHPB tests.Experimental results show that the dynamic punching shear strength,UCS and tensile strength increase with the loading rate.A recently developed dynamic Mohr-Coulomb theory is then used to interpret the testing data.In this model,the angle of internal friction φ is assumed to be independent of loading rate and is obtained using the static strength values.According to the dynamic Mohr-Coulomb theory,the dynamic UCS and the dynamic tensile strength are predicted from the dynamic punching shear strength.Furthermore,based on this dynamic theory,the dynamic UCS is predicted from the dynamic tensile strength.The consistency between the predicted and measured dynamic strengths demonstrates that the dynamic Mohr-Coulomb theory is applicable to FM.展开更多
基金supported by National Natural Science Foundation of China(No. 41090292)
文摘The experimental results of 3-D fracture under compression are introduced in brief and the theory of stress criterion of 3-D fracture is studied. Methods to imitate initial fractures are developed. It is pointed that there are important defects in the extreme value （EV） method ever proposed by Palaniswamy and Knauss. The major defect lies in that only two Euler angles （2EA） are considered, but another one is neglected. If the variation of all the three Euler angles （3EA） are considered, one can get better result which is consistent with the observation of faulting that extends on curved surfaces but not on planes. The method of evaluating maximal normal stress direction vector （NSDV） is proposed and further proved to be equivalent to the 3EA method. It is proved that the NSDV method can be further optimized to the method of composition of the first principal differential plane （CFPDP）. The results from CFPDP method can fit the curved surfaces of initial growth observed in the experiments of 3-D fracture. The CFPDP method can also be used to interpret the 3-D fractures of the slipping section between the asperities in the buried fault plane that is modeled as ellipse crack. The results of 3-D fracture can be applied to interpreting the related problems of faulting including the mechanism of a lot of shatter rocks with different dimensions, the cause of earthquakes occurred at the edge of plate under low shear stress, and the mechanism of anisotropy caused by the extensive dilatancy anisotropy （EDA） cracks.
基金provided by the Natural Sciences and Engineering Research Council of Canada(NSERC)through the Discovery Grant No.72031326
文摘Dynamic strength parameters are extensively used in mining engineering and rock mechanics.However,there are no widely accepted dynamic failure models for rocks.In this study,the dynamic punching shear strength,uniaxial compressive strength(UCS) and tensile strength of fine-grained Fangshan marble(FM)are first measured by using a split Hopkinson pressure bar(SHPB) system.The pulse-shaping technique is then implemented to maintain the dynamic force balance in SHPB tests.Experimental results show that the dynamic punching shear strength,UCS and tensile strength increase with the loading rate.A recently developed dynamic Mohr-Coulomb theory is then used to interpret the testing data.In this model,the angle of internal friction φ is assumed to be independent of loading rate and is obtained using the static strength values.According to the dynamic Mohr-Coulomb theory,the dynamic UCS and the dynamic tensile strength are predicted from the dynamic punching shear strength.Furthermore,based on this dynamic theory,the dynamic UCS is predicted from the dynamic tensile strength.The consistency between the predicted and measured dynamic strengths demonstrates that the dynamic Mohr-Coulomb theory is applicable to FM.
