Shear strength parameter is a crucial in designing the rock mass structures such slope and tunnel. Stability of rock mass structure is affected by apparent joint sets and discontinuities present in the rock mass especially when the joint interfaces degraded and physically altered due to weathering effect. The weathered condition imposed on joint surface importantly play the role to control the shear strength characteristic and sliding behaviour. A comprehensive study and focussing on effect of weathering grade to the rock joint surface particularly for granite type of rock was introduced. A set of granite samples were collected from a quarry then been classified into respective grade of weathering based on surface hardness by using Schmidt rebound hammer and rock material density by using PUNDIT test. The standard laboratory testing of direct shear test that accordance to ISRM suggested method were carried out on jointed block samples with different grades of weathering. Detail assessment on rock joint samples were evaluated to characterize the physical appearance of different weathered joint surface condition. The rock joint surface assessment made based on Joint Roughness Coefficient (JRC) then been correlate with thin section petrographical results for justification with respect to mineral composition contents. As the result, the shear strength of weathered rock joint significantly influenced by the weathering grade due to changes of microstructure behaviour of the granite. Moreover, the lower grade of the granite sample has low frictional resistance force to against the sliding, hence indirectly produced low shear strength of the rock joint.

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This study deals with the effect of water on the tropical weathered granite and sandstone rock characteristics. Water act as an agent in the weathering process that lead to the weakness of the cementation and bonding condition. The process of wetting and drying are able to take place with the presence of water inside the rock microstructure, then further created the numbers of micro-pore which contributing to weakens the rock structure. Thus, this study is focusing to analyses the effect of the presence of water on the mechanical and dynamic properties of granitic rock depending on its weathering degree. The interaction between water and rock was observed through the water-rock interaction test by using saturation and caliper method, where all the rock samples, totalling 81 samples allowed to experience the wet and dry conditions for 21 days, 56 days and 90 days. Uniaxial compressive strength test, indirect (Brazilian) tensile strength and point load tests were conducted to determine the strength of the rock. Meanwhile, P-wave velocity test was conducted to measure the wave velocity that able to penetrate through the intact rock. In conclusion, the increasing of weathering degree, will allowed the rock to absorb the water as their particles has not more tightly bonding. Therefore, it found that the strength of tropical weathered granite was decrease as the interaction with water causes the interlocking of the rock particles is reduces from the process of weathering.