ABSTRACT:

The system of discontinuities that transverses a rock mass delimits rock blocks of many sizes, shapes and positions in a surficial excavation. By using the block theory, it is a possible to determine the most critical block within these isolated masses, which are denoted as key blocks and potential key blocks. This study is an example of the application of the block theory and kinematic analysis for a granite rock mass at a cut slope located at Fraser's Hill in Pahang, Malaysia. The purpose of this study is to indentify key blocks, potential key blocks, stable blocks and tapered blocks, and to determine the safety factor as well as the safe slope angle for this rock slope.

1. INTRODUCTION

Fraser's Hill is the tourism region in Pahang, Malaysia. The granitic rock mass which exist in the Fraser's Hill region contains a number of major discontinuities and a number of sets of minor discontinuities. Therefore, the rock engineering problems of high steep rock slopes in the Fraser's Hill are complicated. In the natural state, these rock slopes are in a stable condition. When the rock-mass is excavated, for example for road, some blocks will develop sliding according to structural planes and then a chain reaction may occur, which may lead to the collapse of the whole slope. The block theory is a method to analyze rock mass stability with graph theory, set theory, geometry and vector algebra. The reason for the rock mass collapse is due to structural blocks sliding over each other at discontinuities. Most previous research on the stability problem of discontinuous rock slope using block theory involve determination of sliding modes and safety factors of sliding blocks. Examples of application block theory for stability analysis of rock slope by Haswanto, and Ghani Rafek (2005, 2008), and Huang T. K. et.al (2003) and Jeongi-gi Um & Kulatilake P.H.S.W. (2001) are same case studies. The Block theory has been used to identify different block types that exist at the entry road cut slope at Fraser's Hill and the main purpose of this study is to determine a safe angle for the rock slope at this location. Then analysis using kinematics to determine the maximum safe slope angle for the rock slope and under influence gravity, groundwater and earthquake has been done.

2. GEOLOGY

Geology of Malaysian peninsula can be divided into three lines or parts which are the west line, the middle line, and the east line. Every line has their owns lithological characteristics, ages and tectonical structure. These lines are parallel a long with the Malaysian peninsula and the border of these lines was not clear yet and still debated. The west line is located in the west part of the Malaysian peninsula and its spread through Perlis-Kedah-Perak in the north to Negeri Sembilan and Melaka in the south. This line is bordered by the Raub-Bentong line and also formatted by the ancient rocks in Malaysia named Manchinchang Formation.

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