A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation ...A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint asperities.Firstly,models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear stages.Secondly,the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex body.Based on the variation law of the maximum possible dilation angle,the maximum possible shear strength model is proposed.Furthermore,a method to calculate the shear stiffness degradation in the plastic stage is proposed.According to the maximum possible shear strength of rock joints,the shear stress-shear displacement prediction model of rock joints is obtained.The new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness,and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.展开更多
Some crucial loads that current strength design specifications have not taken into ac-count are also considered when assessing the strength of a bogie frame.Calculation methods of these loads come from load analysis.F...Some crucial loads that current strength design specifications have not taken into ac-count are also considered when assessing the strength of a bogie frame.Calculation methods of these loads come from load analysis.Finite element simulation and fa-tigue test rig have been used to assess static strength and fatigue strength of a bogie frame.In addition to the two methods,actual running test is also used to assess bogie frame fatigue strength.In finite element simulation method,endurance limit and modified Goodman fatigue limit diagram are two important tools to judge whether fatigue strength of a bogie frame meets requirement.In actual running test method,Miner linear cumulative damage rule is used to assess bogie frame fatigue strength.Endurance limit and modified Goodman fatigue limit diagram are two effective tools to judge fatigue strength of the frame.For the measured dynamic stress data,Miner linear cumulative damage rule seems to be very effective when judging fatigue strength of the frame.All the above methods have proved that static and fatigue strength of the tested bogie frame meets requirement.展开更多
基金National Natural Science Foundation of China(Nos.52208328 and 52104090)Innovation Fund Research Project of State Key Laboratory for GeoMechanics and Deep Underground Engineering(No.SKLGDUEK202201)Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(No.Z020007).
文摘A consecutive joint shear strength model for soft rock joints is proposed in this paper,which takes into account the degradation law of the actual contact three-dimensional(3D)roughness.The essence of the degradation of the maximum possible dilation angle is the degradation of the 3D average equivalent dip angle of the actual contact joint asperities.Firstly,models for calculating the maximum possible dilation angle at the initial and residual shear stress stages are proposed by analyzing the 3D joint morphology characteristics of the corresponding shear stages.Secondly,the variation law of the maximum possible dilation angle is quantified by studying the degradation law of the joint micro convex body.Based on the variation law of the maximum possible dilation angle,the maximum possible shear strength model is proposed.Furthermore,a method to calculate the shear stiffness degradation in the plastic stage is proposed.According to the maximum possible shear strength of rock joints,the shear stress-shear displacement prediction model of rock joints is obtained.The new model reveals that there is a close relationship between joint shear strength and actual contact joint roughness,and the degradation of shear strength after the peak is due to the degradation of actual contact joint roughness.
文摘Some crucial loads that current strength design specifications have not taken into ac-count are also considered when assessing the strength of a bogie frame.Calculation methods of these loads come from load analysis.Finite element simulation and fa-tigue test rig have been used to assess static strength and fatigue strength of a bogie frame.In addition to the two methods,actual running test is also used to assess bogie frame fatigue strength.In finite element simulation method,endurance limit and modified Goodman fatigue limit diagram are two important tools to judge whether fatigue strength of a bogie frame meets requirement.In actual running test method,Miner linear cumulative damage rule is used to assess bogie frame fatigue strength.Endurance limit and modified Goodman fatigue limit diagram are two effective tools to judge fatigue strength of the frame.For the measured dynamic stress data,Miner linear cumulative damage rule seems to be very effective when judging fatigue strength of the frame.All the above methods have proved that static and fatigue strength of the tested bogie frame meets requirement.
