The effect of material scalping and water content on the shear strength of Questa Mine materials

Direct shear tests of 50-mm, 60-mm and 300-mm samples were conducted on materials collected from Questa rock piles and their natural analogs to investigate the role of material scalping and water content on the shear strength of these materials. Normal stresses in the range of 50 to 700 kPa were used for the shear tests. The results of the laboratory tests presented in this paper suggest that scalping of the rock pile material causes reduction in friction angle. The effect of water content was studied as well. Air-dried, moist and saturated samples were tested using direct shear tests. It is shown that the friction angle of Questa rock pile material decreases with increasing water content. Therefore, for unsaturated conditions similar to that of the Questa mine region with a semi-arid environment, shear test results on saturated samples can cause underestimation of the frictional strength of the material.