Fundamental Study on Compact Triaxial Compression Test for In-situ Rock Mass.

1997年研制了原位岩体三轴压缩试验样机。利用该设备进行了考虑现场网架质量应用的模型试验。试件采用单轴抗压强度为15.4MPa的水泥砂浆制成，底端埋入混凝土中，试件为直径为100 mm的圆柱体。1998年在大沽市的以玄武岩为主要岩层的采石场进行了现场试验。用氮气压力转化为水压对取心试样施加围压。通过一系列的试验研究，得出以下结论：1）证实了新研制的试验装置具有预先编制的功能，在试验范围内，剪切强度和内摩擦角不存在尺寸效应;压实三轴压缩试验的剪切强度和内摩擦角比常规三轴压缩试验的剪切强度和内摩擦角小5%左右; 3）结构面的力学性质对三轴压缩强度也有很大的影响; 4）建议改进密封材料。由于填缝料对水压的密封能力不足，只有一个试件因反力不足而破坏。为了积累试验成果和试验技术，将继续在现场岩体中推广应用。

In 1997, prototype testing equipment of triaxial compression test for in-situ rock mass was manufactured. Model test considering application to in-situ rack mass was conducted using this equipment. The specimens, made of cement mortar with 15.4MPa of uniaxial compressive strength and rooted into concrete at bottom end, were cylinders of 100mm in diameter. The case that specimens have the single plane inclined with 60 degrees to the cylinder axis at middle part was also investigated.In 1998, in-situ test was carried out at the quarry which located at Taku City and main rock formation is basalt. Confining pressure was applied to the coring specimen by water pressure transformed from nitrogen gas pressure. Reaction force for axial loading was given by heavy back foe with 0.8MN of self weight.The following conclusions are drawn from a series of experimental research.1) It was confirmed that the newly manufactured testing equipment has the functions previously programmed.In the range of experiments, size effect about shear strength and internal frictional angle did not observed. The compact triaxial compression test gave about 5% less shear strength and internal frictional angle than the conventional triaxial compression test.3) Triaxial compressive strength was strongly affected by the mechanical properties of discontinuity as well.4) Improvement of sealing material was suggested, since calking material has not enough ability to seal the water pressure.Only one specimen reached to the failure due to the shortage of reaction force. In order to cumulate the tested results and testing know-how, it will continue to be applied to the in-situ rock mass.