Estimation of uniaxial compressive strength based on P-wave and Schmidt hammer rebound using statistical method
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ORIGINAL PAPER
Estimation of uniaxial compressive strength based on P-wave and Schmidt hammer rebound using statistical method Behnaz Minaeian & Kaveh Ahangari
Received: 25 June 2011 / Accepted: 25 October 2011 / Published online: 2 December 2011 # Saudi Society for Geosciences 2011
Abstract Preparing high-quality samples, which can fulfill testing standards, from weak and block-in-matrix conglomerate for laboratory tests, is a big challenge in engineering projects. Hence, using indirect methods seems to be indispensable for determination uniaxial compressive strength (UCS). The main objective of this study is to estimate the relation between sonic velocity (Vp), Schmidt hammer rebound number (SCH) and UCS. For this reason, some samples of weak conglomeratic rock were collected from two different sites of dam in Iran (Bakhtiari and Hezardareh Formations). In order to evaluate the correlation, the measured and predicted values utilizing simple and multivariate regression techniques were examined. To control the performance of the proposed equation, root mean square error (RMSE) and value accounts for (VAF%) were determined. The VAF% and RMSE indices were computed as 94.34 and 1.56 for the relation between Vp and UCS from simple regression model. These were 94.39 and 1.6 between SCH and UCS, while these were 97.24 and 1.34 for uniaxial compressive strengths obtained from multivariate regression model.
B. Minaeian Department of Engineering Geology, Science and Research Branch, Islamic Azad University, Tehran, Iran e-mail: [email protected] K. Ahangari (*) Department of Mining Engineering, Engineering Faculty, Science and Research Branch, Islamic Azad University, Toward Hesarak, End of Ashrafi Esfahani, Poonak Square, 14515/ 775 and 14155/4933, 1477893855, Tehran, Iran e-mail: [email protected]
Keyword Uniaxial compressive strength . Schmidt hammer . P-wave . Multivariate regression model . Bakhtiari Formation . Hezardareh Formation
Introduction Estimation of rock mechanical properties is considered to be the most important components in any engineering project. One of the most commonly used and fundamental mechanical parameter is uniaxial compressive strength (UCS). The method for measuring UCS has been standardized by both ASTM and ISRM. This method is destructive in nature, timeconsuming, expensive, and also it requires a large number of well-prepared rock specimens. For this reason, many studies have considered the possibility of a quick and easy way to estimate the UCS of rock based on Schmidt hammer rebound (SHR), point load (Is(50)), P-wave velocity (Vp), slake durability index, and shore hardness. Of these parameters, SHR, Is50, and Vp tests are the comparatively cheap and easy to apply. The index-to-strength conversion factors have been proposed by a number of researchers and have been found to be rock-dependent (Akram and Bakar 2007). However, there is no reported equation in this regard for Plio–Pliocen conglomerate. Considering the vast distribution of conglomeratic formation around the world a
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