Investigation and modeling of mechanical characteristics of non-uniform and discontinuous rock mass in deep ground by in-situ triaxial tests

为了测量岩体的平均应力应变关系，1998年发明了原位三轴试验方法。由于试验样品是在地面上通过旋转钻孔制备的，因此对地面的干扰预计实际上是最小的。在2001财政年度，设计了先进版本的测试方法，使用CCD进行变形测量系统。该系统有望测量整个试样的应变分布，因此被认为对研究非均匀或不连续的岩体行为是有用的。在2002财政年度，引入CCD测量系统的单轴和三轴压缩装置被开发出来。此外，为了减少试件数量和避免分散数据的解释困难，研究了多步加载三轴试验方法。在2003财政年度，我们利用人造岩石样本进行了几次三轴测试。结果表明：随着轴向压缩的进行，试件的变形逐渐局部化。并对现场试验的试验设备进行了改进。变形测量的精度和速度比前一版本提高了十倍。还为实地试验选择了地点，并进行了初步地质调查。2004财政年度，在凝灰岩角砾岩地点进行了一系列实地试验。测量了典型非均匀岩体的平均应力和应变关系。还进行了一些室内三轴试验，以获得研究岩体尺度效应和其他特征的补充数据。

In-situ triaxial test method was invented in 1998 for the purpose to measure average stress and strain relationships of rock masses. Since the test specimens are prepared in the ground by rotary drilling, disturbance of the ground is expected to be as practically minimal.In the fiscal year 2001,the advanced version of the test method was devised using CCD for deformation measuring system. This system was expected to allow measurement of strain distribution throughout the test specimen, thus believed to be useful for studying non-uniform or discontinuous rock mass behavior.In the fiscal year 2002,uniaxial as well as triaxial compression devices were developed introducing this CCD measuring system. Furthermore, multi-step loading triaxial test method was investigated to reduce the number of test specimens and to avoid the difficulties of interpreting scattered data.In the fiscal year 2003, a couple of triaxial tests were conducted with CCD measurement using artificial rock specimens. The results demonstrated that the deformation of specimens became progressively localized as the axial compression proceeded. Moreover, test equipment for the field test was improved. The accuracy and speed of deformation measurement were enhanced as ten-fold as the previous version. Selection of site was also made for the field tests and preliminary geological investigation was conductedIn the fiscal year 2004,a series of field tests were carried out at the site of tuff breccia. Average stress and strain relationships were measured for typically non-uniform rock masses. Some laboratory triaxial tests were also done to obtain the complimentary data to study scale effect and some other features of rock mass behavior.