EVALUATION OF UNIAXIAL COMPRESSIVE STRENGTH OF ROCKS FROM IRREGULAR LUMPS

Abstract

The usual methods for determining the uniaxial compressive strength of rocks require preparation of test specimens of cylindrical or cubical shape. The preparation of the cubes and cylinders require use of diamond saws or diamond drilling equipment, both of which are expensive. Hence evaluation of uniaxial compressive strength from ir-regular lumps would be cheap and quick. In the present study, a relation between the lump strength and uniaxial compressive strength in case of hard, homogeneous, compact, and crystalline rocks has been deter-min'ed'. It has been found that the following relation bet--ween ?IAA strength of the irregular lumps and uniaxial compressive strength 'q= of 2.5 cm cubes may be used for evaluating the uniaxial compressive strength of rocks.. q = 0.28 Zp + 559, where IA and q are in kg/cma Basic properties of rocks, for example, density, specific gravity, absorptionlsaturation coefficient, porosity, durability$ crystallinity, texture etc. have also been studied and their influence on the strength of the rock samples has been discussed.. It has been noted that uniaxial compressive strength of the rocks increases wit iLincrease of specific gravity, with decrease of may, with decrease of saturation coefficient and with decrease of durability value. It has also been found that the crystalline l~J rocks in general, have higher apparent specific gravity, lower porosity, lower saturation coefficient and lower dura-bility value as compared to sandstones and limestones (i.e. sedimentary rocks). The crystalline rocks also show increase of strength with decrease in grain size.