不同温度及应力状态下北山花岗岩蠕变特征研究

 基于不同温度及应力状态下的蠕变特性试验，结合三维声发射实时监测信息，开展北山花岗岩的蠕变变形特性以及加载条件(温度、围压和应力状态)对其蠕变破坏过程的影响研究。试验结果表明，北山花岗岩的蠕变破坏包括初始蠕变阶段(瞬态蠕变)、稳定蠕变阶段和加速蠕变阶段三个阶段，在加速蠕变过程中裂纹迅速扩展和积聚是导致岩石最终破坏的主要原因。蠕变试验过程中，声发射累计数和岩石蠕变体积应变的演化趋势整体上具有一致性，但声发射信号对岩石变形破坏的敏感性更强。对试验数据综合对比分析显示，花岗岩蠕变破坏变形受围压的影响显著，围压越高，岩石蠕变破坏前所能承受的变形越大。温度和应力水平对蠕变破坏变形影响并不明显，但可以对蠕变速率造成影响，进而改变岩石的蠕变破坏时间。根据试验结果，在围压2，10，30 MPa条件下，北山花岗岩的蠕变破坏轴向应变平均值分别为0.34%，0.54%和0.71%。

CREEP BEHAVIOR OF THE BEISHAN GRANITE UNDER DIFFERENT TEMPERATURE AND STRESS CONDITIONS

Based on a series of creep tests with MTS815 rock mechanics test system and the acoustic emission(AE) monitoring system，the creep behavior of the Beishan granite is experimentally studied. A special attention is paid on the influence of temperature and stress level on the creep behavior and cracking process. The experiment data revealed that the creep process can be divided into three stages：the transient creep，the steady creep，and the accelerated creep. The rock failure is essentially related to the intensive accumulation and coalescence of microcracks during the accelerated creep stage. A consistent tendency between AE cumulative counts and volumetric creep strain is noticed. The variation of recorded AE events is found to be more sensitive to the occurrence of rock failure than the volumetric deformation. Under same confining pressure，it is indicated that the increase of temperature and stress level has quite limited affect on the total deformation before rock failure，while it may accelerate the cracking process，and consequently reduces the time to failure. The Beishan granite failed at a similar axial strain under the same confining pressure，of about 0.34%，0.54% and 0.71% under confining pressures of 2MPa，10MPa and 30MPa respectively.