Using a combination of close-range photogrammetry and three-dimensional(3-D) limit equilibrium theory, a determination method for the shear strength parameters of rock-soil mixture is presented. A close-range photogra...Using a combination of close-range photogrammetry and three-dimensional(3-D) limit equilibrium theory, a determination method for the shear strength parameters of rock-soil mixture is presented. A close-range photogrammetry method is used for measurement of the 3-D terrain of the experimental target. Auto CAD Lisp and EXCEL VBA are used to perform 3-D limit equilibrium analysis of the stability of sliding mass and perform backanalysis of shear strength parameters. The presented method was used to determine the shear strength parameters of rock-soil mixtures at the Liyuan Hydropower Station. The 3-D terrain of sliding surface could be measured notably well using of closerange photogrammetry. The computed results reveal that the cohesion and friction angle of rock-soil mixtures were 3.15 k Pa and 29.88o for test A, respectively, and 4.43 k Pa and 28.30o for test B, respectively, within the range of shear strength parameters, as determined by field and laboratory tests. The computation of shear strength parameters is influenced by the mesh grid number, especially the cohesion of the rock-soil mixture. The application of close-range photogrammetry can reduce the siteworks and improve the computational efficiency and accuracy.展开更多
The distribution of shear stress on the cross-section of plastic metal solid circular shaft under pure torsion yielding,the applicability of complete plastic model assumption and the shear stress formula were research...The distribution of shear stress on the cross-section of plastic metal solid circular shaft under pure torsion yielding,the applicability of complete plastic model assumption and the shear stress formula were researched.Based on the shear stress formula of circular shaft under pure torsion in elastic stage,the formula of torque in elastic stage and the definition of yield,it is obtained that the yielding stage of plastic metal shaft under pure torsion is only a surface phenomenon of torque-torsion angle relationship,and the distribution of shear stress is essentially different from that of tensile stress when yielding under uniaxial tension.The pure torsion platform-torsion angle and the shape of torque-torsion angle curve cannot change the distribution of shear stress on the shaft cross-section.The distribution of shear stress is still linear with the maximum shear stress τs.The complete plasticity model assumption is not in accordance with the actual situation of shaft under torsion.The experimental strength data of nine plastic metals are consistent with the calculated results of the new limiting strain energy strength theory(LSEST).The traditional yield stress formula for plastic shaft under torsion is reasonable.The shear stress formula based on the plane assumption in material mechanics is applicable for all loaded stages of torsion shaft.展开更多
A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is ...A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is assessed using the site-specific variation of the natural water content with the effective mean stress. Subsequently, an iterative process is envisaged to obtain the clay stiffness and strength parameters.The at-rest earth pressure coefficient, as well as bearing capacity factor and rigidity index related to the cone penetration test, is also acquired from the analyses. Comparisons are presented between the measured clay parameters and the results of corresponding analyses in five different case studies. It is demonstrated that the presented approach can provide acceptable estimates of saturated clay stiffness and strength parameters. One of the main privileges of the presented methodology is the site-specific procedure developed based on the relationships between clay strength and stiffness parameters, rather than adopting direct correlations. Despite of the utilized iterative processes, the presented approach can be easily implemented using a simple spreadsheet, benefiting both geotechnical researchers and practitioners.展开更多
基金the support of the National Natural Science Foundation of China (Grant Nos. 41472272, 41102194)the Key Deployment Project of the Chinese Academy of Sciences (KZZD-EW-05-01)the Science Foundation for Excellent Youth Scholars of Sichuan University (2013SCU04A07)
文摘Using a combination of close-range photogrammetry and three-dimensional(3-D) limit equilibrium theory, a determination method for the shear strength parameters of rock-soil mixture is presented. A close-range photogrammetry method is used for measurement of the 3-D terrain of the experimental target. Auto CAD Lisp and EXCEL VBA are used to perform 3-D limit equilibrium analysis of the stability of sliding mass and perform backanalysis of shear strength parameters. The presented method was used to determine the shear strength parameters of rock-soil mixtures at the Liyuan Hydropower Station. The 3-D terrain of sliding surface could be measured notably well using of closerange photogrammetry. The computed results reveal that the cohesion and friction angle of rock-soil mixtures were 3.15 k Pa and 29.88o for test A, respectively, and 4.43 k Pa and 28.30o for test B, respectively, within the range of shear strength parameters, as determined by field and laboratory tests. The computation of shear strength parameters is influenced by the mesh grid number, especially the cohesion of the rock-soil mixture. The application of close-range photogrammetry can reduce the siteworks and improve the computational efficiency and accuracy.
文摘The distribution of shear stress on the cross-section of plastic metal solid circular shaft under pure torsion yielding,the applicability of complete plastic model assumption and the shear stress formula were researched.Based on the shear stress formula of circular shaft under pure torsion in elastic stage,the formula of torque in elastic stage and the definition of yield,it is obtained that the yielding stage of plastic metal shaft under pure torsion is only a surface phenomenon of torque-torsion angle relationship,and the distribution of shear stress is essentially different from that of tensile stress when yielding under uniaxial tension.The pure torsion platform-torsion angle and the shape of torque-torsion angle curve cannot change the distribution of shear stress on the shaft cross-section.The distribution of shear stress is still linear with the maximum shear stress τs.The complete plasticity model assumption is not in accordance with the actual situation of shaft under torsion.The experimental strength data of nine plastic metals are consistent with the calculated results of the new limiting strain energy strength theory(LSEST).The traditional yield stress formula for plastic shaft under torsion is reasonable.The shear stress formula based on the plane assumption in material mechanics is applicable for all loaded stages of torsion shaft.
文摘A new approach is developed to determine the shear wave velocity in saturated soft to firm clays using measurements of the liquid limit, plastic limit, and natural water content with depth. The shear wave velocity is assessed using the site-specific variation of the natural water content with the effective mean stress. Subsequently, an iterative process is envisaged to obtain the clay stiffness and strength parameters.The at-rest earth pressure coefficient, as well as bearing capacity factor and rigidity index related to the cone penetration test, is also acquired from the analyses. Comparisons are presented between the measured clay parameters and the results of corresponding analyses in five different case studies. It is demonstrated that the presented approach can provide acceptable estimates of saturated clay stiffness and strength parameters. One of the main privileges of the presented methodology is the site-specific procedure developed based on the relationships between clay strength and stiffness parameters, rather than adopting direct correlations. Despite of the utilized iterative processes, the presented approach can be easily implemented using a simple spreadsheet, benefiting both geotechnical researchers and practitioners.
