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利用改进的霍普金森压杆对不同围压、不同应变率下的岩样进行了试验研究,分析了其在中高应变率下的冲击响应特征与破坏模式。基于试验结果发现在围压一定情况下,岩石的动态抗压强度和峰值应变随应变率的增大而增大,其中抗压强度随应变率呈对数增长;弹性模量对围压和应变率不敏感,且应变率越大岩石破碎现象越严重。其次,在应变率相近情况下,花岗岩的动态抗压强度随围压呈增大趋势,其破坏模式由低围压下的轴向劈裂转向高围压下的压剪破坏;高围压下花岗岩应力–应变曲线出现屈服平台,具有明显的脆—延性转化特征。最后,检验了莫尔–库仑准则和霍克–布朗准则的适用性,指出此花岗岩更符合莫尔–库仑准则,其动态强度增大主要由黏聚力的应变率效应引起。
The rock samples under different confining pressures and different strain rates were tested by the improved Hopkinson pressure bar, and the impact response characteristics and failure modes at medium and high strain rates were analyzed. Based on the experimental results, it is found that under certain confining pressure, the dynamic compressive strength and peak strain of rock increase with the increase of strain rate, and the compressive strength increases logarithmically with strain rate. The elastic modulus affects the confining pressure and strain The rate is not sensitive, and the greater the strain rate, the more serious the rock is broken. Secondly, under similar strain rates, the dynamic compressive strength of granite tends to increase with the confining pressure, and the failure mode changes from the axial splitting under low confining pressure to the compression-scoring under high confining pressure. Under high confining pressure The stress-strain curves of granite show yield platform with obvious brittle-ductile transformation. Finally, we test the applicability of the Mohr-Coulomb criterion and the Hawk-Brown criterion, and point out that the granite is more in accordance with the Mohr-Coulomb criterion. The increase of dynamic strength is mainly caused by the strain rate effect of cohesion.