Prediction of Brittleness Indices of Sandstones Using a Novel Physico-Mechanical Parameter
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ORIGINAL PAPER
Prediction of Brittleness Indices of Sandstones Using a Novel Physico-Mechanical Parameter Amin Jamshidi . Yasin Abdi . Ramin Sarikhani
Received: 12 September 2019 / Accepted: 15 April 2020 Ó Springer Nature Switzerland AG 2020
Abstract In this research, we proposed a novel physico-mechanical parameter (PMP) for predicting the brittleness indices of sandstones. For this purpose, 10 sandstone samples were selected and their uniaxial compressive strength (UCS), Brazilian tensile strength (BTS), point load index (PLI), porosity (n), and brittleness indices were determined. Then, the PMP of samples was calculated based on the ratio of PLI to n. Afterward, some equations were developed between brittleness indices and PMP using regression analyses. The validity of PMP for predicting the brittleness indices was investigated using the raw data obtained from the experimental work carried out by a researcher. It was concluded that the PMP is an accurate and rapid measure for predicting the brittleness indices of rocks. Keywords Physico-mechanical parameter Brittleness indices Point load index Porosity Sandstone
1 Introduction The brittleness is one of the crucial mechanical properties of rocks because of its strong effects on A. Jamshidi (&) Y. Abdi R. Sarikhani Department of Geology, Faculty of Basic Sciences, Lorestan University, Khorramabad, Iran e-mail: [email protected]
geotechnical engineering practices such as cuttability and drillability of rocks, rockburst, and the stability of underground structures and nuclear waste repository (Hussain et al. 2019). Brittleness is largely determined through empirical and computational techniques, but not easily through the empirical works. Several methods have been proposed for measuring rock brittleness through different approaches. Among the brittleness coefficients, those based on uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) are the most widely used ones for quantification of rock brittleness (Hucka and Das 1974; Altindag 2002; Gong and Zhao 2007; Kahraman 2002; Yagiz 2004, 2006). These equations are presented as follows: B1 ¼
UCS BTS
ð1Þ
B2 ¼
UCS BTS UCS þ BTS
ð2Þ
B3 ¼
UCS BTS MPa2 2
ð3Þ
where B1, B2, and B3 are brittleness indices, UCS is the uniaxial compressive strength (MPa), and BTS is the Brazilian tensile strength (MPa). Brittleness indices are obtained as a function of UCS and BTS of rock. The UCS and BTS tests are time-consuming, difficult, and expensive. Moreover, these tests require a standard specimen that often is not possible to prepare, particularly in soft or highly
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jointed rock masses. For these reasons, various physical and mechanical properties such as n, PLI, density (q), P-wave velocity (VP), and Schmidt hammer hardness (SH) are often used for predicting the brittleness indices. Several researchers have studied the relationships between brittleness indices (Eqs. 1–3) with the physical and mechanical properties
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