Experiments to Determine Static and Dynamic Tensile Strength of Deccan Trap Rocks, India

摘要

Tensile strength of rocks is an important parameter in the design of underground structures and for various engineering applications. Lack of literature and rapid development of infrastructure in central region of India calls for a need to characterize the mechanical behaviour of rocks in Deccan trap region which is mainly composed of Basalt. In this paper, characterization of tensile behaviour of Basalt rocks from Deccan trap is done at different loading conditions. Indirect test method namely Brazilian test is used to calculate the static indirect tensile strength at a loading rate of 0.2 kN/s. Tests are performed on different diameters samples and desirable failure modes are recorded. Tensile strength values recorded at slow loading are obtained to be different for specimen having different diameters. However, strength of rock in engineering problems like blasting, mining, rock bursting and breakage are affected by high loading rates. To consider the dynamic loading effect, a modified split Hopkinson pressure bar technique is used. For dynamic tensile experimentation, Brazilian disc specimen are used which are slightly flattened before testing. The flat ended Brazilian discs (FEBD) are placed diametrically in SHPB setup. Dynamic force equilibrium is successfully achieved for the initial stages of fracture propagation till complete failure of sample. The factor for increase in dynamic tensile strength of Deccan Basalt has been evaluated in this work. Scope of further research has been identified for experimentations on soft rocks to determine their dynamic tensile strength characteristics.