Based on laboratory testing of bedded specimens made of artificial geomaterial, meta-siltstone and schist subjected to uniaxial compression and triaxial compression by the Karman scheme, the deformation and strength characteristics of the materials are determined as functions of the bedding angle. The elasticity properties and strength are estimated in accordance with the theoretical model by Salamon and Tien and the Hoek–Brown criterion. For the layered artificial geomaterial, the theoretical model by Salamon and Tien ensures a well-contended estimate of elastic properties. The strength parameter obtained based on the Hoek–Brown criterion is independent of the level of the lateral pressure applied.
Predictions of rock mass stability due to mining activities, including deep-level excavations, or estimations of load-bearing capacity of soil and rocks in foundation engineering and building construction as well as high quality modeling of rock mass behavior under various type loading should take into account the complicated structure, non-uniformity and anisotropic properties of rocks. The review of the recent literature shows that researchers focus on the effect of structure and texture of rocks, in particular with bedding, on their deformation [1–5].
It is technically difficult to produce sufficient number of specimens with the required undisturbed structure for testing and studying. This issue makes one of the main obstacles to development of adequate relations and strength criteria for anisotropic rock masses. In this respect, equivalent artificial geomaterials are advantageous in terms of repeatability of experiments and predictability of structure. This study addresses mechanisms of change in strength and deformation characteristics of specimens made of a layered-structure artificial geomaterial and bedded rocks (meta-siltstone and schist) under uniaxial and triaxial compression.
In the tests on INSTRON 8802 Servohydraulic Fatigue Testing System, the strain rate was 0.1 mm/min. The strength and deformation characteristics of the test materials were determined in accordance with ASTM. The artificial geomaterial specimens were made of two alternating layers of different compositions, namely, layer 1: sand 30 g; cement 10 g, Neolit glue 4 g and water 2.5 g; layer 2: sand 30 g, cement 5 g, Neolit glue 3.5 g and water 2.5 g. The cylindrical specimens were 60 mm long, with a diameter of 30 mm. The angle of bedding (angle between the cylinder specimen axis and the normal to the layer plane (isotropy)) was Ψ = 0°, 15°, 30°, 45°, 60°, 75° and 90°. The specimens made of the artificial geomaterial, meta-siltstone and schist are shown in Figs. 1–3, respectively.
