以声发射估计岩石试样先存应力的新方法

利用声发射话动的凯塞（Kaiser）效应测定岩石先存最大应力已成为声发射技术的重要应用领域。目前,判断岩石凯塞效应对应应力的方法仍被重视。作者在研究岩石在单轴压缩条件下的声发射话动时发现:除了通过凯塞效应可测定岩石的先存最大应力之外,还可根据重复加载时声发射话动的某些特点推断出加载前的先存最大应力,从而进一步验证和提高了利用凯塞效应测定先存最大应力的可靠性。重复加载时声发射话动在一定技术条件下会出现这样的特点:在应力达到第一次加载的最大应力值时出现凯塞效应;而在此之前,当应力达到加载前岩石的先存最大应力值时,声发射话动相对其前后有所特殊。作者认为,这种现象可能反映了材料对先前经历过的损伤的记忆能力。本文初步探讨了这一现象的物理基础。

A NEW METHOD FOR ESTIMATING PRE-EXISTING STRESS IN ROCK BY ACOUSTIC EMISSION

Extensive laboratory investigations on series reloading of rock specimen have resulted in the fact that the pre-existing stress in a rock sample prior to first reloading can be determined through a higher-level secondary reloading. The main feature of AE activity related to the secondary reloading has two aspects: (1) At the higher stress stage, Kaiser effect presents when the specimen is loaded to the maximum stress of first reloading; (2) At the lower stress stage, there is a notable increase of AE activity as soon as the specimen is loadsd to the pre-existing stress level prior to first reloading. In the authors'opinion, this phenomenon would probably be related to the structural damage within the material experienced in its past history.