Fundamental study on strength deterioration rate of weathered rocks

了解自然环境因素的综合作用是评价岩石和岩体稳定性的必要条件。然而，各因素的影响仍存在一些问题有待解决。特别是循环和循环加热的实验结果是有限的，尽管它们的重要性。本文对岩石的耐久性及其评价方法进行了研究，主要包括以下三个方面：1.岩石断裂韧度的各向异性效应为研究岩石各向异性对岩石风化的影响，本文采用ISRM建议的方法，对三种岩石进行了断裂韧度试验。研究发现，岩石中的预存裂纹对岩石的断裂韧度起着重要的作用，而纵波速度与岩石的断裂韧度成正比。2.岩石应力腐蚀实验研究通过真空室内单轴压缩实验，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。3.冻融作用下岩石的风化作用通过冻融循环试验，研究了岩石的风化作用对岩石强度和力学性能的影响。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表面扩展，而低速冻结和融化产生平行于自由表面的裂纹。

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.