声发射测量地应力综合分析方法与实验验证

Comprehensive analysis method and experimental vertification for in-situ stress measurement by acoustic emission tests

通过岩石声发射试验测量地应力需要确定声发射某个参数或参数累计的试验曲线的拐点,即Kaiser效应点,针对作图法难以精确确定试验曲线拐点的难题,提出了声发射试验测量地应力的一种综合分析方法,即首先通过作图法求取试验曲线的拐点作为近似的Kaiser效应点,其次采用G-P算法计算声发射能量关联分形维数,将近似的Kaiser效应点邻近的能量关联分形维数最小点确定为最终Kaiser效应点,对应的应力值即为试验中试件加载方向的原岩应力值。为了验证该综合方法的有效性,进行了现场套孔应力解除试验,得到了试件加载方向的实测应力值,共进行了11个试件的岩石声发射试验,试验结果表明:综合分析方法得到的地应力值精度明显高于作图法,可作为岩石声发射测量地应力试验的一种新的分析方法。

The Kaiser effect （KE） point where there is a substantial increase in acoustic emission （AE） is to be determined for the evaluation of the in-situ stress by using rock AE tests. However it is hard to get the point accurately by means of the graphing method. A comprehensive method is proposed based on the theoretical and experimental analyses. First, we can get the approximate KE point by projecting the tangent at the turning point of the AE activity curve although it is not very accurate. Second, the relevant fractal dimensions of AE energy in the whole AE tests are calculated by using the G-P algorithm. One of the points with the minimum value of the relevant fractal dimension adjacent to the approximate KE point is taken as the final KE point and its corresponding stress is the value of the pre-stress. To validate the effectiveness of the proposed method, in-situ stress experiments are carried out by means of the overcoring stress relief method. The rock cores are obtained from boreholes used in the overcoring stress relief method. And the pre-stress of rock core specimens along the loading direction is determined. AE tests on the l 1 rock specimens are carried out. The results indicate that it has higher accuracy in estimation of the pre-stress by using the proposed comprehensive method compared with the graphing method. It can be used as a new method in the evaluation ofpre-stress in AE tests.