Estimation of rock engineering properties using hardness tests Faisal I. Shalabi a, ⁎ , Edward J. Cording b , Omar H. Al-Hattamleh a a Department of Civil Engineering, Hashemite University, 13115 Zarqa, Jordan b Department of Civil Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA Received 12 September 2006; received in revised form 17 December 2006; accepted 29 December 2006 Available online 17 January 2007 Abstract In engineering projects such as tunnels, dams, foundations, and slope stability, the strength and elastic properties of the intact rock affect both the project design and the construction operation. It is sometimes expensive and time consuming to perform direct tests to evaluate the engineering properties (such as strength, modulus of elasticity, and Poisson's ratio) of the intact rock. The purpose of this work is to investigate the relationships between the engineering properties of the intact rock and the different types of hardness (Schmidt, shore scleroscope, abrasion, and total hardness), which are relatively cheap and easy to evaluate. In this study, dolomite, dolomitic limestone, and shale rocks were used. For simplicity, linear statistical analyses were performed. The results show that there are good relationships between the engineering properties of the intact rock and its hardness. Also, the results of this study are compared well with the results obtained by other investigators conducted on different types of rocks. © 2007 Elsevier B.V. All rights reserved. Keywords: Abrasion; Elasticity; Poisson's ratio; Schmidt hardness; Shore hardness; Strength; Statistical relationships 1. Introduction Physical and mechanical properties of intact rocks are very important in civil engineering works that interact with rock such as underground structures, dams, foundations on rock, and rock slopes. Performing direct tests to evaluate rock strength and deformation is mostly expensive and required considerable time, especially the preparation of rock samples for testing. Different indirect testing methods were developed and used to interpret the engineering properties of rock. The indirect tests include point load, Schmidt rebound hardness, Shore Scleroscope hardness, and abrasion hardness. These tests are relatively easy to perform, not expensive, and take short testing time. The physical properties of the intact rocks depend on its microstructure. Willard and McWilliams (1969) indicated that the microstructure, including: minerals cleavage, grain boundaries, and microfractures, has an effect on the rock strength and the direction of failure. Merriam et al. (1970) found a good relationship between the strength of granitic rock and quartz content. Onodera and Asoka Kumara (1980) found that the strength of igneous rocks decreases linearly with the increase in grain size. Irfan (1996) indicated that the physical properties of the intact rocks are highly influenced by the type, texture, percentage, and fabric of the minerals forming the rock. Many studies had been carried out to correlate the engineering properties of rock with its physical index Engineering Geology 90 (2007) 138 – 147 www.elsevier.com/locate/enggeo ⁎ Corresponding author. Tel.: +962 5 390 3333; fax: +962 5 382 6348. E-mail address: fshalabi@hu.edu.jo (F.I. Shalabi). 0013-7952/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.enggeo.2006.12.006