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。利用该设备进行了适用于现场机架质量的模型试验。试件为直径100mm的圆柱体，由水泥砂浆制成，单轴抗压强度为15.4MPa，下端根植于混凝土中。对试件中部呈与柱面呈60度斜角的单一平面的情况也进行了研究。1998年在大库市采石场进行了现场试验，主要岩层为玄武岩。取心试样的围压由氮气压力转化为水压。轴向载荷的反作用力由自重0.8MN的重型背弓提供。以下结论是通过一系列实验研究得出的。1)确认新制造的检测设备具有先前编程的功能。在试验范围内，未观察到抗剪强度和内摩擦角的尺寸效应。致密三轴压缩试验的抗剪强度和内摩擦角比常规三轴压缩试验低5%左右。3)三轴抗压强度也受断裂力学特性的强烈影响。4)结焦材料密封水压能力不足，建议对密封材料进行改进。由于反作用力不足，只有一个试件发生了破坏。为了积累试验成果和试验诀窍，将继续在原位岩体中应用。

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.