Weighting Analysis on the Stress Influenced Volume in Jointed Rock Mass

• Main Authors: Chung-Hsien Chen, 陳忠賢
• Other Authors: 楊長義
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/97256420532406140846

碩士 === 淡江大學 === 土木工程學系碩士班 === 94 === While surface subjected to point load, the stress influenced volume differs from the laccolith’s properties. Therefore it’s essential to understand the stress influenced Volume. Bray (1977) experience formula deal with distribution of principle stress under transversely isotropic rock with single joint, it could interpret distribution of principle stress while changing the laccolith’s properties though, the influence proportion within parameters is hard to know. Besides, the application of Bray formula still have limits in multi-load, multi set of joints. Hence the study aims to rectify correspondence of influenced parameters through weighting analysis. This study analyzes the relation between stress influenced volume and parameters within Bray formula (such as joint direction, joint stiffness ratio, joint spacing, elastic modulus and poisson''s ratio of the rock material), then expand the formula to multi-load, multi set of joints, and slope condition using superposition of stresses, finally check the rationality of predicted stress volume. To conclude the 73,780 predicted conditions with influenced volume, width, depth under different inherent rock parameters and external loading condition. Using multiple regression analysis and correspondence analysis to obtain the weighing values and the difference between parameters, could get the following conclusions: (1) The influenced volume of maximum principle stress in rock mainly controlled by joint stiffness ratio, joint spacing and elastic modulus of rock. Although the joint direction controls the anisotropy of stress influenced distribution, it doesn’t influence the stress volume. (2) Under two set of point load, the stress influenced volume has superposition effect. While changing the scale of loadings and their distances, it highly influences the stress volume. (3) The anisotropy of influenced volume in two joint sets is lighter than single joint set. Though the stress volume have anisotropy in orthogonal joints, it doesn’t change with the joint direction. (4) While changing the direction of loading , joint stiffness ratio, joint spacing and elastic modulus of rock still mainly controls the influenced volume, as to the influenced depth and width the volume changes with the loading directions. (5) By using correspondence analysis, joint stiffness ratio, joint spacing and elastic modulus of rock highly influenced the stress scale and have great relationship. In spite of the difference between joint inclination and the former three is high, it influences the anisotropy of stress distribution greatest, while the poisson''s ratio influences least. Besides, the loading ratio, loading distance, and the angle of two set of joints influence the stress scale highly, even though it has little dependence.