72:3 (2015) 31–39 | www.jurnalteknologi.utm.my | eISSN 2180–3722 | Full paper Jurnal Teknologi Discrete Element Modelling of Complex Failure Mechanism at Quarry Slope Rini A. Abdullah, * Mohd For Mohd Amin, Ahmad S.A. Rashid, S.M. Yahya Department of Geotechnics & Transportation, Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 UTM Johor Bahru, Johor Malaysia *Corresponding author: asnida@utm.my Article history Received: 17 August 2014 Received in revised form: 17 November 2014 Accepted: 24 December 2014 Graphical abstract Abstract Road cutting, open pit mining, quarrying and various other constructions in hilly terrain demand special attention in terms of slope stability. The analysis of slope stability is of great significance not only for ensuring safe design of excavated slope, but also for preventing potential hazards. This research was undertaken to identify the controlling parameters affecting the slope instability. As the rock slope behaviour is mostly governed by discontinuities, discontinuum numerical technique such as Discrete Element Method (DEM) which has the ability to address discontinuity controlled instability is well suited for this case. This study investigated the failure pattern and its responsible factors leading to failure of a slope at a slate quarry situated in Wales, United Kingdom as a case study. The research work consisted of field investigation, laboratory experiments and parametric analysis by powerful and renowned distinct element computational tool Universal Discrete Element Code (UDEC). Evidence showed that complex failure mechanism involving distinct planar sliding surface along with block-flexural toppling contributed to the instability at the studied slate quarry. Dip of discontinuity, presence of water, weathering state and slope angle were the significant factors found in this study to have profound impact on controlling rock slope instability. The modelling results also indicated that the influence of structurally dipping at 78 of cleavage in slate and the water filling in the crack which developed excess water pressure have triggered the failure. Keywords: Discrete element method; UDEC; rock slope; block-flexural toppling Abstrak Kerja-kerja yang melibatkan pemotongan cerun batuan seperti bagi pembinaan jalan raya, perlombongan, kuari dan lain-lain pembinaan memerlukan perhatian khusus dari sudut kestabilan cerun. Analisis kestabilan cerun bukan sahaja mengakibatkan impak yang besar bagi memastikan keselamatan rekabentuk cerun, malahan juga bagi mencegah kemungkinan bencana. Kajian ini bertujuan mengenal pasti parameter penting yang memberi pengaruh kepada ketidakstabilan cerun. Oleh kerana cerun batuan sangat dipengaruhi oleh sifat ketidakselanjaran itu sendiri, maka teknik berangka tak berhubung iaitu Kaedah Unsur Diskret yang berupaya menangani ketakselanjaran yang mengakibatkan ketidakstabilan cerun digunakan. Kajian ini dilakukan ke atas sifat kegagalan dan faktor-faktor yang menyebabkan kegagalan cerun di sebuah kuari yang terletak di Wales, United Kingdom. Kajian ini melibatkan penyiasatan lapangan, kerja-kerja makmal dan analisis berparameter dengan menggunakan perisian Universal Discrete Element Code (UDEC). Hasil kajian mendapati bahawa mekanisma kegagalan yang kompleks yang melibatkan gelongsoran dan blok-lenturan jatuhan menyebabkan ketidakstabilan pada cerun di kuari tersebut. Kemiringan ketakselanjaran, kehadiran air, tahap luluhawa dan sudut potongan cerun merupakan faktor utama yang dikenalpasti sebagai penyebab utama kepada ketidakstabilan cerun tersebut. Hasil daripada pemodelan juga menunjukkan bahawa sudut ketidaselanjaran berstruktur pada 78 dan kehadiran air di dalam retakan telah menyebabkan peningkatan tekanan air yang berlebihan telah mencetuskan kegagalan cerun ini. Kata kunci: Kaedah unsur diskret; Universal Discrete Element Code (UDEC); cerun batuan; blok-lenturan jatuhan © 2015 Penerbit UTM Press. All rights reserved. 1.0 INTRODUCTION In rock slope stability, there is no single parameter which dominates the rock slope behaviour. Rather, a combination of properties determines the slope behaviour [1-13]. Therefore, a robust type of analysis is required to represent the behaviour of rock slopes. Broad selections of analysis types are available, which includes limit equilibrium, kinematics and probability approaches and now more recently, the numerical types of analysis which covers finite element and discrete element