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Lithological Unit Thickness Approach For Determining Intact Rock Strength (IRS) of Slope Forming Rock Material Of Crocker Formation

Lithological Unit Thickness Approach For Determining Intact Rock Strength (IRS) of Slope Forming Rock Material Of Crocker Formation

Authors                   : Ismail Abd Rahim, Sanudin Tahir, Baba Musta & Shariff A. K. Omang

Publication Date     : September 2009

Journal                    : Borneo Science

Volume                    :  25

Issue                        : -

Pages                       : 23-32

Abstract - The Intact Rock Strength (IRS) of the slope forming rock material has been determined by several different means in order to evaluate slope stability. The intact rock strength is determined using Unconfined Compressive Strength test, Point Load test, Schmidt hammer test, Equotip test and filed test called simple means for monolithological unit or homogeneous rock masses. In heterogeneous rock masses with varied lithological units some efforts have been taken to establish the most representative intact rock material for the slope forming rock material that includes ‘average weight of strong layer’, ‘average weight of strong and weak layer’, ‘thickness of strong and weak layer’ and ‘weaker layer’ approaches. A new ‘lithological unit thickness’ approach has been proposed in this study. This ‘lithological unit thickness’ denotes estimating the intact rock strength by geological mapping, slope geometry and lithological thickness measurement,  petrographical study, intact rock strength testing and modeling. The results show that the estimation of intact rock strength of the slope forming rock material by ‘lithological unit thickness’ approach is more representative and the value for slopes B1, B2, B3 and B4 of heterogeneous Crocker Formation in CPSB Stone Quarry, Tamparuli area are 129 MPa, 108 MPa, 117 MPa and 148 MPa, respectively  and can be classified as ‘strong’ rock masses.