不同含水状态下砂岩剪切过程中声发射特性试验研究

EXPERIMENTAL STUDY OF ACOUSTIC EMISSION CHARACTERISTICS DURING SHEARING PROCESS OF SANDSTONE UNDER DIFFERENT WATER CONTENTS

利用自主研发的煤岩细观剪切试验装置和PCI-2型声发射测试分析系统对饱和度分别为0%,50%和100%三种不同含水状态下砂岩剪切破坏过程中的声发射特性进行试验研究,探讨声发射信号随时间的演化规律及其与砂岩裂纹的开裂、扩展之间的关系。研究结果表明:声发射活动伴随着砂岩整个剪切破坏过程,表现为剪应力峰值前,声发射活动不显著,声发射信号均较小,而在剪应力峰值后声发射信号出现剧增;且随着含水量增加,砂岩抗剪强度依次减小,声发射信号的剧增点出现的时间相应提前;在各含水状态下,声发射事件率峰值出现的时间总是滞后于剪应力达到峰值的时间;饱和度为0%时砂岩表面裂纹出现在剪应力峰值之后,且声发射活动最强烈,破坏时的累计声发射事件数最多,即累计损伤最大;而饱和度为50%和100%时砂岩表面裂纹出现在剪应力峰值之前,破坏后累计声发射事件数相对较少,累计损伤也相应小一些。

Based on the independent development of meso-shear test equipment for coal rock and PCI - 2 acoustic emission detection analysis system, acoustic emission features of sandstone with different saturation degrees of 0%, 50% and 100% during shearing process are studied： and the relationship between evolution law of acoustic emission signal and cracking and extension of sandstone is discussed. The results show that acoustic emission activity is associated with the whole shearing process of sandstone. The acoustic emission activity is not obvious and acoustic emission signal is comparatively small before the shear stress peak value, but after it the acoustic emission signal leaps. With the increase of water content, the shear strength reduces, and the leap point of acoustic emission signal appears in advance successively. Under different moisture states, the peak value of acoustic emission events rate always appears lag the time that the shear stress reaches its peak. With the saturation degree of 0%, the surface crack of sandstone appears after the shear stress peak and the acoustic emission activity is the most intense; the cumulative acoustic emission events at failure is the most, that is, the cumulative damage is the biggest. But with the saturation degrees of 50% and 100% the surface crack of sandstone appears before the shear stress peak, the cumulative acoustic emission events at failure is comparatively less, and the cumulative damage is smaller.