The paper presents the results of laboratory tests performed on a large number of intact sedimentary rock specimens (limestone, sandstone, siltstone) from Greece. The physical properties (porosity, dry density), mechanical properties (uniaxial compressive strength), Young's modulus, point load index, Schmidt hardness) and dynamic properties (wave velocity) were determined. Furthermore, laboratory results of intact rock properties were collected and evaluated. From the statistical analysis of the data, regression equations were established amongst intact rock parameters. The ratio of rock strength and deformation modulus was investigated and its range was determined for all rock types. A comparison was made between existing empirical equations for the correlation of uniaxial strength, Schmidt hardness and dry density (σc-SHV- ρd). This comparison proved that Deere - Miller's (1966) chart yields the better prediction of the uniaxial compressive strength. Additionally, the correlation between uniaxial compressive strength, σc, and point load strength, Is50, shows that an exponential fit gives a significantly better fit than a linear one. Finally, a multivariable analysis was done between tangent Young's modulus, uniaxial compressive strength and wave velocity (Etc-Vp) and an empirical correlation is proposed.


Rock engineering properties is considered to be the most important parameters in the design of ground works and in the classification of rock for engineering purposes. The expression of correlations between the engineering properties of intact rock has always been the scope of experimental research, driven by the need to depict the actual behavior of rock and to calculate most accurately the design parameters.

At the present study investigation of physical, mechanical and dynamic properties was performed, correlations were expressed and compared by the ones proposed in literature. The strength and deformability of intact rock was investigated thoroughly. In order to accomplish that, a number of laboratory tests on limestone, sandstone and siltstone were conducted and a large database, containing results on laboratory tests on intact rock, was created.


A large number of rock mechanics laboratory tests were conducted on intact rock specimens of sedimentary rocks originated from central and southern Greece (Tziallas, 2008). The following tests were performed: determination of porosity and dry density (n, ρd), uniaxial compression test (σc) with determination of tangential Young modulus (Et), point load test (Is(50)), Schmidt hammer test (SHV) and ultrasonic wave propagation test (Vp, Vs). For the determination of Et, L.V.D.T. was used and a Schmidt hammer type L for the corresponding test.

In order to propose correlations of rock properties, a database (containing more than 5000 records) was created with data from literature as well as from the Central Laboratory of Public Works. The database contains laboratory tests on 37 different rock types. Both the laboratory tests and this large database resulted in more than 80 reliable correlations (with r2>0,5), and a number of conclusions as presented here after.

3.1. Range of Et and σ c ratio

The range of Young modulus in relation to the uniaxial compressive strength was determined.

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