Perpustakaan Digital ITB

Common problem in mining activity is instability caused by jointed rock mass. The strength of jointed rock mass can be increased by cement injection. An artificial rock sample made from dental plaster type of moldano tara is used in this study to evaluate the influence of cement injection to the strength of jointed rock sample. The roughness of joint surface are obtained from the natural rock joints and divided into three groups of Joint Roughness Coefficient (JRC) values based on Barton criteria. The injection materials are mixture of cement and water with the ratio of water and cement of 4: 5 and 3: 2. This artificial samples are then subjected to direct shear tests. The test results are analyzed by Mohr-Coulomb criterion to obtain the cohesion and internal friction angle. It is revealed that cohesion and internal friction angle increased for injected rock sample. The strength increase varies by JRC condition. For Sample with JRC value between 8-10, the study find that injection material with water to cement ratio of 4:5 is more effective than cement injection with ratio of 3:2. For JRC value between 12-14, 16-18, and 18-20, it is found that cement injection with ratio of 3:2 is more effective than 4:5.