Co-operative research for developing reliable core-based methods for measuring in-situ stresses

8名研究人员开展了基础研究和实际地应力测量，以提高基于岩心的大深度地应力测量方法的可靠性。在应力测量中，将常见的岩心按不同的方法分配给每个进行应力测量的调查人员。在Kamaishi矿海拔550m和250m处提取了花岗闪长岩和石灰岩两组岩心。应力测量方法为：fujii博士和yamamoto教授的变形率分析法（DRA）， furuzumi教授和seto教授的声发射法（AE）和DRA结合法，oikawa教授和sano教授的差分应变（曲线）分析法（DSCA）。日本东北大学的matsuki教授和kojima博士执行了所有基于核心的方法。除了传统的DSCA外，oikawa先生还在静水压力下进行了一种改进的DRA， sano博士测量了弹性波速的各向异性，并将其应用于应力测量。研究人员给出的结果之间的比较尚未完成，但发现了一些一致的地方，也有一些分歧。作为基础研究工作，山本教授基于地壳内岩石应力均质化的概念，提出了单轴压应力达到法向地应力时非弹性变形发生的机理。matsuki教授和kojima博士还提出了另一种可以解释岩石行为的机制，在这种机制上，所有基于岩心的方法都是基于玻璃板的模型实验，玻璃板包含一个封闭的裂缝，在尖端有两个主翼裂缝。

Fundamental research as well as actual in-situ stress measurements have been carried out by eight researchers to enhance reliability of core-based methods for measuring in-situ stresses at great depth. In the stress measurements common rock cores were distributed to each investigator who has performed stress measurements according to each way. Two series of rock core, a granodiorite and a limestone, were extracted from 550m and 250m level from Kamaishi mine.The methods of stress measurement were Deformation Rate Analysis (DRA) for Dr.Fujii and Prof.Yamamoto, the combined method of Acoustic Emission (AE) and the DRA for Prof.Furuzumi and Dr.Seto and Differential Strain (Curve) Analysis (DSCA) for Mr.Oikawa and Prof.Sano. The members of Tohoku Univ., Prof.Matsuki and Dr.Kojima, performed all the core-based methods. Mr.Oikawa performed a midified DRA under hydrostatic pressure in addition to the conventional DSCA, and Dr.Sano measured the anisotropy of elastic wave velocity to apply it to stress measurement. The comparison among the results given by the researchers has not been completed, but some agreements as well as some disagreements have been found.As basic research work, Prof.Yamamoto has proposed the mechanism which describes how inelastic deformation occurs when uniaxial compressive stress reaches the normal in-situ stress by being based on the concept of stress homoginization in rock in the earth crust. Prof.Matsuki and Dr.Kojima also have proposed another mechanism which may explain the behavior of rock, on which all of the core-based methods are based by model experiments of a glass plate which contained a closed crack with two main wing cracks at the tips.