Anisotropic shear behavior of jointed rock masses at ulu jelai hydroelectric project, Pahang
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Date
2018-09-01
Authors
Nur Khafiza Sapari
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Abstract
The anisotropic shear behavior of jointed rock mass is one of the crucial issues in engineering field especially to the construction and developments. This research focused on the geological condition, rock mass strength and in situ stress state. The research has been done at Ulu Jelai Hydroelectric Dam project, which currently constructed near Cameron Highland, Pahang. An 88 m height of roller-compacted concrete (RCC) of dam is build with 22 km diversion tunnel as a part of dam structure. The rock mass is very difficult due to repeated regional series of faulting and shearing. Geologically, Cameron Highland is characterized by NW, NE and N-S lineaments and cut by NW, NE and N-S by going through faults displaying evidence for Cenozoic movements. Recent field investigation has identified that some of these faults evidence for Quaternary Pleistocene to Holocene movements. On the other hand, major faults in the Peninsular Malaysia strike at N-S, NNW-SSE, NW-SE, WNW-ESE, E-W, ENE-WSW and NE-SW. The value of uniaxial compressive strength (UCS) test is in the range of 0.5 – 96.0 MPa while the Brazilian Tensile Strength (BTS) test is about 0.5 – 14.31 MPa. The in situ stress analysis shows that the fractures occur in the borehole and the induced fractures during the hydraulic fracturing test follows the major fault pattern of Peninsular Malaysia. The magnitude and the direction of fracture have been determined during this analysis study which is the maximum horizontal stress has been found approximately 6 MPa with the direction normal to the dam axis with an approximation of ± 30⁰ and the least pseudo-horizontal has been found approximately 4 MPa. The correlation has been made referring to the data obtained where there is a strong relationship between the orientations of principal stress regime at Susu Dam with the major fault pattern of Peninsular Malaysia. The correlation between the rock mass quality introduced by SMEC with the Rock Mass Rating (RMR) system introduced by Beiniawski also has been determined during this research. From the observation, the system developed by SMEC is limited to the degree mylonitisation while the RMR system is more general and can be widely used for any rock material conditions.