冻融循环条件下砂岩物理力学劣化特性的实验研究

Experimental Study on Physical and Mechanical Deterioration Characteristics of Sandstone under Freeze-thaw Cycle

为研究冻融循环对岩石的物理力学性质劣化影响,选取砂岩为试样进行冻融循环实验、核磁共振实验和单轴压缩声发射实验。研究结果表明:当冻融循环达到30次数时,试样外观首先发生劣化;试样的孔隙率与冻融循环次数呈正相关,而束缚流体饱和度则呈负相关;冻融循环次数的增加会使得试样单轴压缩过程中声发射事件率的变化趋势发生改变、临近破坏时的低事件率缺失面积减小,且在30次时最小;声发射峰值能率随冻融循环次数的增加而减小,“平稳期”平均能率与峰值能率的比值不断增大,在30次冻融循环时达到最高。30次冻融循环可划定为冻融循环作用对岩石试样劣化的分界线。

The sandstone was selected as samples for the freeze-thaw cycle experiment,nuclear magnetic resonance experiment,and uniaxial compression acoustic emission experiment to study the freeze-thaw cycle’s influence on the deterioration of rocks'physical and mechanical properties.The results show that when the freeze-thaw cycles reach 30 times,the sample's appearance deteriorates first.The sample's porosity is positively correlated with the number of freeze-thaw cycles,while the bound fluid saturation is negatively correlated.The increase of freeze-thaw cycles will change the changing trend of acoustic emission event rate during uniaxial compression of the sample,and the missing area of low event rate near failure will decrease and be the smallest at 30 cycles.The peak energy rate of acoustic emission decreases with the increase of freeze-thaw cycles.The average energy rate ratio to the peak energy rate in the“steady period”increases continuously,reaching the highest at 30 freeze-thaw cycles.Thirty freeze-thaw cycles may be defined as the dividing line of rock sample deterioration caused by freeze-thaw cycles.