冻融循环和围压对岩石物理力学性质影响的试验研究

Experimental research of influences of freeze-thaw cycles and confining pressure on physical-mechanical characteristics of rocks

对饱和红砂岩进行开放系统下的冻融循环试验,记录红砂岩的冻融劣化过程及破坏特征;当试样经历0,5,10,20,40次冻融循环后,分别进行4种设定围压下的力学特性试验,分析了冻融循环和围压对岩石物理力学性质的影响规律。研究表明:红砂岩的冻融劣化模式主要为颗粒剥落、龟裂、脱落及断裂模式。随着冻融循环的进行,岩样的质量和密度呈现先增后减的趋势,而纵波波速持续减小;随着冻融循环次数和围压的增加,岩石的压缩性不断增强,峰值应变逐渐增大,塑性屈服段渐趋明显,残余强度降低速率减慢,破坏形式由脆性转化为延性;而弹性模量、抗压强度及残余强度随着围压的增大不断增大,随着冻融循环次数的增大明显减小。岩石的细观结构经历损伤的非线性演化,显现出宏观力学特性的变化。

The freeze-thaw cycling experiment was conducted for water-saturated sandstone under an open system to record the freeze-thaw deterioration process and failure characteristic of rock. And then the mechanical properties experiment with four kinds of confining pressures was carried out for sandstone on different freeze-thaw cycles（ 0,5,10,20,40 times）. Subsequently,the influence law of freeze-thaw cycles and confining pressure on the physical and mechanical properties of rock was analyzed systematically. The result shows that the primary modes of freeze-thaw damage deterioration for sandstone are spalling mode,crack mode,shedding mode and fracture mode. With the increase of freezethaw cycles,the quality and density of rock samples present the trend of increasing at first and then decreasing,while the speed of the longitudinal wave decreases continuously. With the increase of confining pressure and the number of freeze-thaw cycles,the compaction property is enhanced gradually,the peak strain increases constantly,the plastic yield segment is becoming obviously,and the reduction rate of residual strength decreases,exhibiting the failure mode of enhanced ductility and weakened brittleness. While the elastic modulus,compressive strength and residual strengthincrease obviously with the increase of confining pressure,and decrease with the increase of freeze-thaw cycles.Through the nonlinear evolution of meso-structural damage,the rock displays the variation of macroscopic mechanical properties.