Fundamental study on strength deterioration rate of weathered rocks

了解自然环境因素的综合作用对于评价岩石和岩体的稳定性是必不可少的。然而，各个因素的影响还存在着尚未解决的问题。尤其是循环加热和循环加热的实验结果虽然很重要，但也是有限的。1.各向异性对岩石断裂韧度的影响为了研究各向异性对岩石风化的影响，采用ISRM推荐的方法，对三种岩石进行了断裂韧度试验。2.岩石应力腐蚀试验研究通过真空室单轴压缩试验，研究了应力、应变率、温度和水蒸气对岩石中裂纹扩展的影响。精确测定了岩石的应力腐蚀指数，讨论了岩石的蠕变现象以及岩石的长期强度。3.岩石的冻融风化。进行了冻融循环试验，明确了风化对岩石强度和力学性质的影响。结果表明，岩石中裂纹的扩展取决于冻结和/或融化的速度，高速冻结导致裂纹垂直于自由面扩展，而低速冻结和融化产生平行于自由面的裂纹。

Understanding of the composite action of natural environmental factors is indispensable for estimating the stability of rock and rock mass. However, there are unsolved problems for the effect of each factor. Especially, experimental results of the cyclic and cyclic heating are limited in spite of their importance. The present study on the durability of rock and its estimation method consists of three parts as follows :1.Anisotropy effect on fracture toughness of rock.To investigate the anisotropy effect on weathering of rock, the fracture toughness tests according to the suggested method of ISRM are performed, using three type of rock. It has been found out that the pre-existing crack within rock plays an important role in determing the fracture toughness, as well as the longitudinal wave velocity which is proportional to the fracture toughness.2.Experimental study on stress corrosion of rock.The influence of stress, strain rate, temperature and water vapor on the crack propagation in rock has been investigated by the uniaxial compressiontest in a vacuum chamber. The stress corrosion index has been precisely determined and the creep phenomena have been discussed as well as the long-term strength of rock.3.Weathering of rock with freezing and thawing.A cyclic test of freezing and thawing has been performed to make clear the weathering effect on the strength and the mechanical property of rock. In has been shown that the crack propagation in rock is depending upon the speed of freezing and/or thawing, and that a high speed freezing results the crack propagation normal to the free surface, but low speed freezing and thawing produce the cracks parallel to the free surface.