For understanding the damage and failure rule of rock under different uniaxial compressive loads and dynamic loads, tests on red sandstone were carried out on Instron 1342 electro-servo controlled testing system with ...For understanding the damage and failure rule of rock under different uniaxial compressive loads and dynamic loads, tests on red sandstone were carried out on Instron 1342 electro-servo controlled testing system with different uniaxial compressive loads of 0, 2, 4 and 6 MPa. It is found that peak stress, peak strain, elastic modulus and total strain energy decrease with the increase of static compressive stress. Based on the test results, the mechanism on damage and failure of rock was analyzed, and according to the equivalent strain hypothesis, a new constitutive model of elastic-plastic damage was established, and then the calculated results with the established model were compared with test results to show a good agreement. Furthermore the rule of releasing ratio of damage strain energy was discussed.展开更多
Considering strain localization in the form of a narrow band initiated just at peak stress, three analytical expressions for stressstrain curves of quasibrittle geomaterial (such as rock and concrete) in uniaxial tens...Considering strain localization in the form of a narrow band initiated just at peak stress, three analytical expressions for stressstrain curves of quasibrittle geomaterial (such as rock and concrete) in uniaxial tension, direct shear and uniaxial compression were presented, respectively. The three derived stressstrain curves were generalized as a unified formula. Beyond the onset of strain localization, a linear strain-softening constitutive relation for localized band was assigned. The size of the band was controlled by internal or characteristic length according to gradient-dependent plasticity. Elastic strain within the entire specimen was assumed to be uniform and decreased with the increase of plastic strain in localized band. Total strain of the specimen was decomposed into elastic and plastic parts. Plastic strain of the specimen was the average value of plastic strains in localized band over the entire specimen. For different heights, the predicted softening branches of the relative stressstrain curves in uniaxial compression are consistent with the previously experimental results for normal concrete specimens. The present expressions for the post-peak stressdeformation curves in uniaxial tension and direct shear agree with the previously numerical results based on gradient-dependent plasticity.展开更多
文摘For understanding the damage and failure rule of rock under different uniaxial compressive loads and dynamic loads, tests on red sandstone were carried out on Instron 1342 electro-servo controlled testing system with different uniaxial compressive loads of 0, 2, 4 and 6 MPa. It is found that peak stress, peak strain, elastic modulus and total strain energy decrease with the increase of static compressive stress. Based on the test results, the mechanism on damage and failure of rock was analyzed, and according to the equivalent strain hypothesis, a new constitutive model of elastic-plastic damage was established, and then the calculated results with the established model were compared with test results to show a good agreement. Furthermore the rule of releasing ratio of damage strain energy was discussed.
文摘Considering strain localization in the form of a narrow band initiated just at peak stress, three analytical expressions for stressstrain curves of quasibrittle geomaterial (such as rock and concrete) in uniaxial tension, direct shear and uniaxial compression were presented, respectively. The three derived stressstrain curves were generalized as a unified formula. Beyond the onset of strain localization, a linear strain-softening constitutive relation for localized band was assigned. The size of the band was controlled by internal or characteristic length according to gradient-dependent plasticity. Elastic strain within the entire specimen was assumed to be uniform and decreased with the increase of plastic strain in localized band. Total strain of the specimen was decomposed into elastic and plastic parts. Plastic strain of the specimen was the average value of plastic strains in localized band over the entire specimen. For different heights, the predicted softening branches of the relative stressstrain curves in uniaxial compression are consistent with the previously experimental results for normal concrete specimens. The present expressions for the post-peak stressdeformation curves in uniaxial tension and direct shear agree with the previously numerical results based on gradient-dependent plasticity.
