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对灰岩开展单轴、常规三轴与峰前卸荷试验,对比分析不同应力路径下灰岩变形过程的能量变化特征。试验分析表明,灰岩加荷破坏和卸荷破坏的能量变化规律存在明显差异。由于围压抑制了裂纹的扩展,与单轴压缩破坏相比,常规三轴压缩试验灰岩吸收的总能量U和积蓄的弹性能eU更多。常规三轴试验灰岩积蓄的弹性能eU在峰值强度前一直增加,而卸荷破坏的弹性能eU在卸荷开始后基本不变,说明卸荷破坏释放的弹性能eU主要是在加荷阶段累积完成的,岩体所处的初始地应力状态决定了其破坏的能量释放量。加荷和卸荷应力路径下,灰岩临近破坏点耗散能dU都快速增加,但是卸荷破坏耗散能dU增速远大于加荷破坏耗散能增速,耗散能的迅速增加表明岩石破坏的发生。随着围压升高,灰岩吸收的总能量U和储存的弹性能eU逐渐升高。随着卸荷速度增加,灰岩吸收的总能量U、储存的弹性能eU和耗散的应变能dU逐渐减小。
The uniaxial and conventional unloading tests of uniaxial and pre-peak limestone are carried out, and the energy variation characteristics of limestone deformation under different stress paths are compared and analyzed. Experimental analysis shows that there is a significant difference in energy variation between limestone loading failure and unloading failure. Since the confining pressure suppresses the crack propagation, the total energy U absorbed by the conventional triaxial compression test limestone and the accumulated elastic energy eU are more than the uniaxial compression failure. In the conventional triaxial tests, the elastic energy eU of accumulated limestone increased until the peak intensity, while the elastic energy eU of the unloading failure basically remained unchanged after the unloading started, indicating that the elastic energy eU released by unloading damage was mainly at the loading stage Accumulatively, the initial state of stress in the rock determines the amount of energy released. Under the loading and unloading stress paths, the dissipative energy dU at the rupture point near the limestone increases rapidly, but the unloading and destroying dissipated energy dU increases much faster than the destructive dissipative energy under loading and the rapid increase of dissipative energy shows Rock destruction occurred. As the confining pressure increases, the total energy absorbed by the limestone U and the stored elastic energy eU gradually increase. As the unloading rate increases, the total energy absorbed by the limestone U, the stored elastic energy eU and the dissipative strain energy dU gradually decrease.