Methods of Determining Shear Strength of Rocks at Dynamic or Static Loading

Six test methods for determining dynamic or static shear strength of rocks are described in this peper. The shear strength of granite, marble, and sandstone have been systematically studied by means of these methods and the following results are obtained: 1 ) Shear strength of rocks clearly increases with the increase of loading rate, i.e. dynamic shear strength off rocks is higher than static shear strength, and shear strength of rocks increases with the increase of normal stress at the shear plane of specimens. 2) The value 400 kg/cm2 of confining pressure is a brittleness-ductility transference point for sandstone, i. e. the shear strength of sandstone increases with confining pressure going up when it is below 400 kg/cm2, and the shear strength of sandstone decreases with the increase of confining pressure when it is above 400 kg/cm2.The simple punch shear test method is recommended to determine static or dynamic shear strength of rocks.