不同高径比石膏试样破坏特性及其能量耗散

采用RMT-150B岩石力学试验机,对七种不同高径比的石膏试样进行了单轴压缩试验,分析其力学特性及其破坏特征.根据单轴压缩力学试验结果,利用能量耗散理论,分析其能量耗散特性.研究结果表明:随轴压应力的增加,石膏试样内部微裂隙先闭合,而后在其尖端产生了新裂隙;新裂隙随轴压应力的增加而逐渐地扩展、贯通、形成破裂面,最终发生剪切滑移破坏;石膏试样的体积应变随轴压应力的增大,经历了先压缩后增加,最后急剧膨胀,表现出明显的非线性变形;石膏试样的峰值应力、弹性模量随高径比的减小而增大;轴向应变和横向应变随高径比的减小而减小;变形模量与高径比之间的关系不明确,不能用其表征石膏试样的变形特性;高径比越大的石膏试样受压后容易发生剪切破坏,破坏时吸收的能量增量越快,属于脆性破坏,而高径比越小的石膏试样则发生压酥破坏,属于塑性破坏.

Failure Characteristics and Energy Dissipation of the GypsumSample in Diffferent Height to Diameter Ratios

The uniaxial compression mechanical test of the gypsum sample with seven different height to diameter ratios were measured by using RMT-150B rock mechanics testing machine,and the mechanical properties and failure characteristics of the gypsum sample were analysed.Based on the test results,the energy dissipation characteristics of the gypsum in different height to diameter ratios were investigated by using the energy dissipation theory.The results show that the microcracks within the gypsum sample is closed firstly,and then produces a new fractures at the tip of the microcracks,and the new fractures are gradually expanded,run through crack,forming fructure plane,shear and slip failure with the increase of the uniaxial compressive stress.The volume strain of the gypsum sample is compressed firstly and then increases and rapid expands finally with the increase of the uniaxial compressive stress.The peak stress and elastic modulus increase with the decrease of the height to diameter ratio,and the axial strain and the lateral strain decrease with the decrease of the height to diameter ratio,and the relationship between deformation modulus and height to diameter ratio is not evident,which can not characterize the deformation characteristics of the gypsum sample.The gypsum sample that is easy to have shear and slip failure and is quick to absorb energy with the increase of the height to diameter ratio belongs to brittle failure,and on the contrary that is easy to have crisp failure,belongs to plastic failure.