动静组合加载下干燥与饱水石灰岩破坏特性

Failure characteristics of dry and saturated limestone under dynamic and static combined loading

为探究饱水石灰岩在高地应力和冲击扰动下的破坏特性,采用室内试验与数值模拟结合的方法,利用∅50 mm的分离式霍普金森杆装置对干燥与饱水的石灰岩试样进行动静组合下单轴冲击压缩试验,并采用高速摄像机记录破坏过程,然后进行数值模拟。结果表明:轴压作用下试样应力-应变曲线无压密阶段,曲线表现出峰后塑性,直至主裂纹产生;轴压相同,饱水石灰岩试样产生主裂纹的时间更短;饱水条件和轴压条件对石灰岩动态抗压强度的影响因子分别为1.055和1.098,在应变率分别为145,200,260 s^(-1)左右时,饱水石灰岩较干燥石灰岩峰值应力分别降低0.11,0.10,0.10倍,而轴压为8 MPa,较4 MPa的峰值应力分别降低0.18,0.05,0.07倍。轴压对岩石的破坏作用主要体现在应力波后的残余加载上,自由水会使裂纹接触面产生滑移从而表现出倾斜角度较大的裂纹。

In order to study the failure characteristics of water saturated limestone under high ground stress and impact disturbance,adopted a method that combines indoor experiments and numerical simulations,∅50mm split Hopkinson bar experimental device was used to conduct uniaxial impact compression experiments on dry and saturated limestone samples,and use high-speed camera to record the destruction process,then peoform numerical sumulations.The results show that the stress-strain curve of the sample under axial compression shows post peak plasticity without compaction stage until the main crack occurs,with the same axial pressure,and the time for the main crack to occur in the water saturated limestone sample is shorter.The influence factors of saturated conditions and axial compression conditions on the dynamic compressive strength of limestone are 1.055 and 1.098 respectively.When the strain rates are about 145 s^(-1),200 s^(-1) and 260 s^(-1) respectively,the peak stress of saturated limestone is 0.11 times,0.10 times and 0.10 times lower than that of dry limestone,while the peak stress of 8 MPa is 0.18 times,0.05 times and 0.07 times lower than that of 4 MPa.The destructive effect of axial compression on rocks is mainly reflected in the residual loading after stress waves.Free water can cause slip on the contact surface of cracks,resulting in cracks with larger inclination angles.