确定岩石中先存应力状态的声发射法

对经过三向预加压的石灰岩试件所进行的试验研究表明,其声发射活动的特点与单向受力时的情况完全不同。此时,在一个试件的一次加载过程中会出现两次Kaiser效应,分别对应于载荷达到预加压时所施加的轴压与围压值之时。利用回归分析的方法来处理试验数据,可以使声发射活动对应力的响应关系用三条回归直线来近似。这三条直线的两个交点所对应的应力值,可以确定出预加压时岩石试件承受的应力状态

USE OF ACOUSTIC EMISSION METHOD FOR ESTIMATION OF PREEXISTING STRESSES IN THE ROCK

An experiment of Indiana limestone has been conducted for estimation of preexisting stresses in rock cores. Five cylindrical specimens were pre-stressed under triaxial loading conditions to simulate various in situ stress fields. 26 pieces of specimens smaller, prepared from five pre-loaded rock specimens were under uniaxial pressure, when, acoustic emissions (AE) and applied stress were recorded as a function of time. The AE activity was presented as the sum of AE counts at each increment of 500 lbs. It was found possible for each experiment to fit a set of three straight lines to data obtained by using least square method. The value of stress at two intersections of these three lines. may serve to predict the levels of the maximal preexisting axial stress and confining pressure. The error for this technique may be found to be within 10％ for most of specimens in use