Sains Malaysiana 51(2)(2022): 421-436

http://doi.org/10.17576/jsm-2022-5102-08

Application of a Comprehensive Rock Slope Stability Assessment Approach for Selected Malaysian Granitic Rock Slopes

(Pengaplikasian Pendekatan Penilaian Kestabilan Cerun Batu Komprehensif untuk Cerun Batu Granit Malaysia yang Terpilih)

AFIQ FARHAN ABDUL RAHIM¹, ABDUL GHANI MD RAFEK², AILIE SOFYIANA SERASA³, RINI ASNIDA ABDULLAH⁴, AFIKAH RAHIM⁴, WAN SALMI WAN HARUN⁵, FOONG SWEE YEOK⁶, MUSLIM ABDURRAHMAN⁷, LEE KHAI ERN⁸, NGUYEN XUAN HUY⁹, TRAN VAN XUAN⁹ & GOH THIAN LAI^{1, 10}*

¹Department of Earth Sciences and Environment, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Engineering Geology Advisory, 11, SS21/12, Damansara Utama, 47400 Petaling Jaya, Selangor Darul Ehsan, Malaysia

³School of Engineering (Petroleum), Asia Pacific University of Technology & Innovation (APU), Technology Park Malaysia, Bukit Jalil, 57000 Kuala Lumpur, Wilayah Persekutuan, Malaysia

⁴Department of Geotechnics & Transportation, School of Civil Engineering, Faculty of Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor Darul Takzim, Malaysia

⁵Jabatan Mineral dan Geosains Malaysia, Menara PJH, Tingkat 9, 2, Jalan Tun Abdul Razak, Presint 2, 62000 Putrajaya, Wilayah Persekutuan, Malaysia

⁶School of Biological Science, Universiti Sains Malaysia, 11800 Gelugor, Penang, Malaysia

⁷Department of Petroleum Engineering, Universitas Islam Riau, Kota Pekanbaru, Riau 28284, Indonesia

⁸Institute for Environment and Development (LESTARI), Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

⁹Faculty of Geology and Petroleum Engineering, Ho Chi Minh University of Technology, VNU-HCM, 268 Ly Thuong Kiet Street, District 10, Ho Chi Minh City 700000, Vietnam

¹⁰State key Laboratory for Geomechanics& Deep Underground Engineering, China University of Mining and Technology, Xuzhou 221116, China

Received: 19 January 2021/Accepted: 18 June 2021

ABSTRACT

In Malaysia, rock slope stability analysis has been largely confined to kinematic analysis with rock mass rating systems as assessment tools for stability analysis. While this method addresses the fundamental issues of rock slope stability including identifying potential failure modes, an information gap still exists between geologists and engineers in designing proper mitigation measures for rock slopes. This paper aims to address this issue by incorporating several methodologies, including kinematic analysis, slope mass rating and the Barton-Bandis criterion for the limit equilibrium method. Four rock slopes with potential instabilities namely KSA, KSB, LHA, and LHB were studied. KSA and KSB were located near Kajang, Selangor while LHA and LHB were located near Rawang, Selangor. Each slope exhibits multiple potential failures, with attention given on sliding-type failures in planar or wedge form. A slope mass rating value was assigned to each potential failure based on rock mass rating_basic and the slope mass rating based on readjustments for discontinuity orientation and excavation method. Factor of safety from limit equilibrium method show potentially unstable blocks and failed blocks (Factor of Safety <1.00) with confirmation on site. Water filling of discontinuity apertures plays an important role in destabilizing rock blocks, especially in wet conditions experienced in Malaysia’s tropical climate. Several geometries are identified as potentially unstable due to low slope mass rating (Class V) and factor of safety of <1.2, such as planar J5 and wedge J2*J5 at KSA, wedge forming with sets J3, J4 and fault plane at KSB, planar J2 at LHA, and wedge J3*J4 at LHB. Stabilization structures such as rock bolts can be better designed with the determined factor of safety values coupled with relevant geological and geotechnical inputs. In this comprehensive rock slope stability assessment approach, limit equilibrium method serves as a useful method in analyzing rock slope stability to complement kinematic analysis and stability ratings often used in Malaysia.

Keywords: Factor of safety; limit equilibrium method; rock slope stability; slope mass rating

ABSTRAK

Di Malaysia, sebahagian besar analisis kestabilan cerun batuan adalah tertumpu pada analisis kinematik dan diguna bersama dengan sistem perkadaran jasad batuan sebagai alat penilaian dalam analisis kestabilan. Walaupun kaedah ini dapat menangani isu-isu asas kestabilan cerun batuan dengan mengenal pasti ragam kegagalan yang berpotensi berlaku, jurang maklumat masih wujud antara geologi dengan jurutera dalam reka bentuk langkah-langkah mitigasi untuk cerun batuan yang lebih baik. Makalah ini bertujuan untuk mengatasi masalah ini dengan menggunakan beberapa kaedah iaitu analisis kinematik, perkadaran jasad cerun dan kriteria Barton-Bandis dalam kaedah had keseimbangan. Empat cerun batuan yang berpotensi tidak stabil dinamakan KSA, KSB, LHA dan LHB telah dikaji. KSA dan KSB terletak berhampiran Kajang, Selangor manakala LHA dan LHB terletak berhampiran Rawang, Selangor. Setiap cerun menunjukkan beberapa potensi kegagalan, terutamanya kegagalan jenis gelongsor dalam bentuk satah atau baji. Nilai perkadaran jasad cerun setiap potensi kegagalan telah ditentukan berdasarkan perkadaran jasad batuan_asas dan perkadaran jasad cerun yang berasaskan penyelarasan orientasi ketakselanjaran dan kaedah pengorekan. Faktor keselamatan yang diperoleh daripada kaedah had keseimbangan telah menentukan bongkah yang berpotensi tidak stabil dan gagal (Faktor Keselamatan <1.00) dan telah mendapat pengesahan di lapangan. Pengisian air dalam bukaan ketakselanjaran memainkan peranan penting dalam ketidakstabilan bongkah batuan, terutama dalam keadaan basah pada iklim tropika Malaysia. Beberapa geometri yang berpotensi tidak stabil telah dikenal pasti kerana mempunyai perkadaran jasad cerun yang rendah (kelas V) dan faktor keselamatan <1.2, seperti satah J5 dan baji J2 * J5 di KSA, baji yang terbentuk daripada set J3, J4 dan satah sesar di KSB, satah J2 di LHA, dan baji J3 * J4 di LHB. Struktur penstabilan seperti bolt batuan dapat direka bentuk dengan lebih baik hasil gabungan nilai faktor keselamatan dengan input geologi dan geoteknik yang berkaitan. Dalam pendekatan penilaian kestabilan cerun batuan yang menyeluruh ini, kaedah had keseimbangan berfungsi sebagai kaedah yang baik yang diguna bersama dengan analisis kinematik dan perkadaran kestabilan dalam penganalisisan kestabilan cerun batuan yang sering digunakan di Malaysia.

Kata kunci: Faktor keselamatan; kaedah had keseimbangan; kestabilan cerun batuan; perkadaran jasad cerun

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*Corresponding author; email: gdsbgoh@gmail.com