Study on the Mobilization Factor of the Shear Strength for Non- persistent Joints

• Main Authors: Lee, Chun Hsun, 李俊勳
• Other Authors: Yang Zon-Yee
• Format: Others
• Language: zh-TW
• Published: 1996
• Online Access: http://ndltd.ncl.edu.tw/handle/03251361265468145642

碩士 === 淡江大學 === 土木工程學系 === 84 === The shear strength of non-persistent jointed rocks is usually estimated by superimposing the strengths of joints and rock bridges. Due to the different stiffness, the peak strengths of joints and rock bridge do not mobilize simultaneously. The direct superposition approach could over-estimate the strength of jointed rocks. A series test of non-persistent jointed rocks molded by artificial material is performed by direct shear test. The cases of persistence in this test program include 0 (intact rock), 0.5, 0.8, and 1.0 (persistence joint). The percentage of joint strength mobilized at the failure , called the mobilization factor C, is then back-calculated from the test results taken into account of deformabilities or strengths of rock bridge and joints. Moreover, the predicted strength considering the factor C is applied to sandstone.The main conclusions of this study are drawn as follows. (1) The mobilization factor C of joint strength increases as the joint persistence increases. (2) The shear strength of jointed rocks range between the lower and the upper strengths that obtained by strength approach and by deformability approach, respectively. (3) The C value is suggested as 1 when the normal stress is lower than 1/5JCS. (4) The factor C obtained by the deformability approach is more reasonable than the strength approach. (5) The frictional force on joint planes reduces the stress concentration of rock bridges. (6) The effect of the additional confining stress on shear force plane is really existing and the value equals 0.73 of the normal stress in this research.