ABSTRACT

The main direct tensile problems of rock specimens have been analyzed at the laboratory conditions. Based on the laboratory and numerical experiments the geometry of saliferous specimen has been suggested considering the stress state mode arising under loading process, grain size, bracing influence. Rectangular samples sized 250 × 50 × 50 mm were used for this study. Before testing the sample has been cemented in metal clips to be used for clamping in the reversing device or in the grippers of the testing machine. The cementation of the samples is carried out using the magnesia cement mortar based on saturated carnallite brine. The experiments were carried out using the electromechanical testing machine Zwick/050. A constant traversing speed of 0.1 mm/min was maintained during the test. The measurement of longitudinal deformations was carried out on the surface of the sample with the help of three remote LVDT sensors with a measurement accuracy of 0.0005 mm arranged in an equilateral triangle. The “sensor-sample” contact was carried out with the help of plates fixed on the sample surface. The experiment continued until the sample was completely failure, i.e. when it was divided into two pieces. The obtained results were presented in the form of stress-strain diagrams, which were used to determine strength and strain parameters. Variation intervals of strength, failure strain, and deformation modulus and energy capacity of fracture under extension are established for the samples with different layering orientations.

The obtained results are intended to determine the mechanical salt rock characteristics of Verchnekamskoe potassium salts deposit under direct tensile loading.