Sains Malaysiana 46(2)(2017): 181–188

http://dx.doi.org/10.17576/jsm-2017-4602-01

Peak Friction Angle Estimation from Joint Roughness Coefficient of Discontinuities of Limestone in Peninsular Malaysia

(Anggaran Sudut Geseran Puncak daripada Pekali Kasar Kekasaran Ketakselanjaran Batu Kapur

di Semenanjung Malaysia)

AILIE SOFYIANA SERASA^1,2, GOH THIAN LA^I*, ABDUL GHANI RAFEK³, AZIMAH HUSSIN¹, LEE KHAI ERN⁴ & TUAN RUSLI MOHAMED⁵

¹Geology Program, School of Environmental and Natural Resource Sciences, Faculty of Science

and Technology, Universiti Kebangsaan Malaysia, 43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

²Chemical and Petroleum Engineering Department, Faculty of Engineering, Technology and Built Environment, UCSI University, 56000 Cheras, Kuala Lumpur, Malaysia

³Department of Geosciences, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak Darul Ridzuan, Malaysia

⁴Institute for Environment and Development (LESTARI), Universiti Kebangsaan Malaysia

43600 UKM Bangi, Selangor Darul Ehsan, Malaysia

⁵Jabatan Mineral dan Geosains Malaysia, Perak, Jalan Sultan Azlan Shah, 31400 Ipoh,

Perak Darul Ridzuan, Malaysia

Diserahkan: 1 Mac 2016/Diterima: 6 Jun 2016

ABSTRACT

The peak friction angle (φ_peak) roughness of discontinuity surfaces is a value that is fundamental to the understanding of shear strength of geological discontinuities, considering its importance in determining the mechanical properties of the discontinuity surface. It is however, both time and cost demanding to determine the peak friction angle as it requires an extensive series of laboratory tests. This paper presents an approach in the form of an experimentally determined polynomial equation to estimate peak friction angle of limestone discontinuity surfaces by measuring the Joint Roughness Coefficient (JRC) values in a field survey study, and applying the fore mentioned empirical correlation. A total of 1967 tilt tests and JRC measurements were conducted in the laboratory to determine the peak friction angles of rough limestone discontinuity surfaces. The experimental results were analyzed and correlated to establish a polynomial equation of φ_peak = -0.0635JRC² + 3.95JRC + 25.2 with coefficient of determination (R²) of 0.99. The laboratory results were also compared with theoretical results calculated from Barton's linear equation. The results shown that estimation of peak friction angles were more accurate using the newly proposed polynomial equation since the percentage differences between measured and calculated peak friction angles is less than 6% compared to estimation from Barton's linear equation where the percentage of differences is less than 11%. The proposed correlation offers a practical method for estimation of peak friction angles of discontinuity surfaces of limestone from measurement of JRC in the field.

Keywords: Discontinuity surface roughness; empirical correlation; joint roughness coefficient (JRC); limestone; peak friction angle

ABSTRAK

Sudut geseran puncak (fpeak) kekasaran permukaan ketakselanjaran adalah nilai asasi kepada pemahaman tentangkekuatan ricih ketakselanjaran geologi, memandangkan kepentingannya dalam menentukan sifat mekanik permukaan ketakselanjaran. Walau bagaimanapun, ia memerlukan masa dan kos yang tinggi untuk menentukan sudut geseran puncak kerana ia memerlukan satu siri ujian makmal yang menyeluruh. Kertas ini membentangkan suatu pendekatan dalam bentuk persamaan polinomial yang dijalankan secara makmal untuk menganggar sudut geseran puncak permukaan ketakselanjaran batu kapur dengan mengukur Pekali Kekasaran Kekar (JRC) dalam kajian survei lapangan dan menggunakan empirikal korelasi yang disebutkan sebelum ini. Sejumlah 1967 ujian kemiringan dan pengukuran JRC telah dijalankan di dalam makmal untuk menentukan sudut geseran puncak permukaan kasar ketakselanjaran batu kapur. Keputusan ujian telah dianalisis dan dikorelasi untuk mewujudkan persamaan polinomial fpeak= - 0.0635JRC2 + 3.95JRC+ 25.2 dengan pekali penentuan (R2) sebanyak 0.99. Keputusan makmal juga dibandingkan dengan keputusan secara teori yang dikira daripada persamaan linear Barton. Hasil menunjukkan bahawa anggaran sudut geseran puncak adalah lebih tepat dengan menggunakan persamaan polinomial baru yang dicadangkan memandangkan perbezaan peratusan antara sudut geseran puncak yang diukur dengan yang dikira adalah kurang daripada 6% berbanding dengan anggaran daripada persamaan linear Barton dan peratusan perbezaan adalah kurang daripada 11%. Korelasi yang dicadangkan memberikan suatu kaedah praktikal untuk anggaran puncak sudut geseran permukaan ketakselanjaran batu kapur daripada pengukuran JRC dalam lapangan.

Kata kunci: Batu kapur; kekasaran ketakselanjaran permukaan; korelasi empirikal; pekali kekasaran kekar (JRC); sudut geseran puncak

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