花岗岩的加载速率效应及能量机制研究

加载速率对岩石的力学性质以及变形破坏方式具有重要的影响。基于MTS810电液伺服材料试验系统与PCI-2声发射仪对岩样进行不同加载速率作用下的单轴压缩和声发射试验。研究结果表明：（1）在各级加载速率作用下，岩样单轴压缩应力-应变曲线大致经历了压密、弹性、屈服、破坏四个阶段。岩样峰后曲线在加载速率为0.001~0.01 mm/s时出现台阶型分段跌落状，在加载速率为0.01~0.1 mm/s时呈现光滑、陡峭的连续曲线。（2）岩样峰值强度、弹性模量随加载速率的增加而增大，与加载速率对数均呈现三次多项式拟合关系。峰值应变随加载速率的增加而减小，与加载速率对数呈现线性拟合关系。（3）随着加载速率由0.001mm/s增加至0.1mm/s，岩样吸收的总应变能 具有波动性，可释放的弹性应变能 增幅60.42%，耗散应变能 降幅 66.38%， 增幅43.33%， 降幅66.67%，岩样破裂模式由拉剪破坏逐渐向张拉劈裂破坏过渡，岩样破裂块数增多。（4）加载速率为0.001~0.1 mm/s时，岩样破坏方式有所不同，但破坏为同一类损伤过程。单轴压缩状态下，能量耗散使得岩样损伤致使强度丧失，而能量释放使得岩样宏观破裂面贯通，并向着能量释放的方向张裂或弹射破坏。

Investigations on loading rate effects and energy mechanism of granite

Loading rate has an important influence on rock mechanical properties and failure modes. Experiments on uniaxial compression and acoustic emission of different loading rates on granite were conducted by MTS810 servo-controlled testing machine and PCI-2 acoustic emission instrument. The results show that: (1) Stress-strain curves of granite under uniaxial compression have experienced compaction, elasticity, yield and failure four stages. Post-peak curves of the rock sample present stepped and segmented drop shape at loading rates from 0.001 mm/s to 0.01mm/s, and present a smooth, steeper continuous curve at loading rates from 0. 01 mm/s to 0. 1mm/s. (2)Peak strength and elastic modulus of rock increases with increasing loading rate, both present cubic polynomial relations with the logarithm of the loading rate. Peak strain decreases with increasing loading rate,which shows linear regression relationship with the logarithm of the loading rate. (3)As the loading rate increased from 0.001mm / s to 0. 1mm / s, the total strain energy was volatile, releasable elastic strain energy increased 60.42%, dissipated strain energy decreased 66.38%, the ratio of releasable elastic strain energy of the total strain energy increased 43.33%, the ratio of dissipated strain energy of the total strain energy decreased 66.67%, rock fracture mode changes from tensile shear failure to tensile splitting failure gradually, the number of broken pieces also increased. (4)When the loading rate from 0.001 mm / s to 0.1 mm / s, the failure process of rock sample is the same kind of damage although the failure mode is different. The energy dissipation makes rock damage and the strength loss, but the energy release makes the macrofracture surface be run-through, which towards the direction of the energy released by rifting or catapult destruction.