Verification of post failure behaviour of rock using closed-circuit servo-controlled testing machine


Author : Rini Asnida Abdullah & Mohd For Mohd AminPublication : Bulletin of the Geological Society of MalaysiaVolume : 54Page : 17-20Year : 2008


Description

Bulletin of the Geological Society of Malaysia, Volume 54, November 2008, pp. 17 - 20

 

Verification of post failure behaviour of rock using closed-circuit servo-controlled testing machine

Rini AsnidAbdullah & Mohd For Mohd Amin

Faculty of Civil Engineering, Universiti Teknologi Malaysia, 81310 Skudai, Johor Bahru, Malaysia

 

Abstract— The analysis of the stress-strain curve is a fundamental aspect in the field of rock mechanics. Most rock masses are not intact but have discontinuities. It is important to study the stress-strain curve beyond the peak failure as to assess the characteristic of intact rock against non-intact rock. However, several difficulties arise in obtaining the complete stress-strain curve. Since most rocks exhibit brittle behaviour, they fail violently and uncontrollably when tested on conventional compression machines. In this study, two series of uniaxial compression test were performed on sandstone samples. The first test was conducted using a 2000 kN MaTest conventional compression testing machine and the results were compared with a 3000 kN Tinius Olsen servo-controlled testing machine. Based on the results obtained from sandstone samples, post-peak failure can be achieved by using the servo-controlled testing machine. Comparison between the modes of failure observed from the tests on both types of machines clearly show that violent fracture is not the intrinsic characteristic of the rock but due to the rapid release of strain energy from the loading machine.

Keywords: Closed-circuit servo-controlled testing machine, complete stress-strain curve, excavation in rock, sandstone

 

Abstrak— Analisis lengkungan tegasan-terikan merupakan aspek asas di dalam bidang mekanik batuan. Oleh kerana kebanyakkan jasad batuan mempamerkan kelakuan dengan kewujudan ketakselaran dan bukannya batuan yang utuh. Dengan itu, adalah penting untuk memahami sifat-sifat lengkungan tegasan-terikan selepas kegagalan puncak sekiranya ingin mengkaji ciri-ciri batuan tak-utuh. Walaubagaimanapun, terdapat kesulitan di dalam memperolehi lengkungan tegasan-terikan yang lengkap, ini adalah disebabkan kebanyakan batuan adalah bersifat rapuh dan gagal secara tiba-tiba jika diuji dengan mesin ujikaji mampatan biasa. Di dalam kajian ini, dua siri ujikaji mampatan satu paksi dijalankan ke atas sampel batu pasir. Ujikaji pertama dijalankan dengan menggunakan mesin ujikaji mampatan biasa MaTest berkapasiti 2000 kN dan keputusannya dibandingkan dengan mesin kawalan-servo Tinius Olsen dengan kapasiti 3000 kN. Berdasarkan keputusan yang diperolehi daripada sampel-sampel batupasir, pasca-kegagalan puncak dapat dicapai dengan menggunakan mesin ujikaji berkawalan-servo. Jelasnya, perbandingan di antara kedua-dua mod kegagalan ini mengesahkan bahawa kegagalan secara tiba-tiba bukanlah sifat sebenar batuan, tetapi disebabkan oleh tenaga terikan yang dibebaskan oleh mesin ujikaji itu sendiri.