Volume 31, Issue 3 (May 2008)
Development of a Modified in situ Direct Shear Test Technique to Determine Shear Strength Parameters of Mine Rock Piles
A modified direct shear test apparatus was designed and used to measure cohesion and friction angle of rock pile materials. Two test apparatuses were constructed, a 30-cm square metal shear box and a 60-cm square metal shear box. In addition to the shear box, the testing apparatus has a metal top plate, a fabricated roller plate, normal and shear dial gages with wooden supports, and two hydraulic jacks and cylinders with a maximum oil pressure of 70 MPa (10,000 psi) and a load capacity of ten tons. The main difference between the in situ shear box and its conventional laboratory equivalent is that the in situ shear box consists of a single box that confines an excavated block of rock pile material. The lower half of the block consists of the rock pile material underneath the shear plane that is a semi-infinite domain. This modification in the shear test apparatus reduces the time needed for block preparation, helps perform several tests at different levels of the same sample block, and allows for accommodating large shear displacement with no reduction in the area of the shear plane.