Wear of Sandstone Surfaces During Direct Shear Testing of Sandstone/Concrete Joints

The shear behaviour of rock/concrete interface is a critical factor controlling the performance of drilled shafts socketed into rock. The authors have conducted an extensive series of direct shear tests on rough sandstone/concrete interfaces to investigate the performance of bored piles socketed into sandstone. During these tests, wear of the sandstone surface was apparent. As a result of this wear, the shear strength of the interface was significantly reduced compared to rock/concrete joints of similar roughness profiles in which no wear was observed. In order to develop an understanding of the wear mechanisms, an experimental program that focused on the wear process was carried out. Factors that affect the wear mechanism have been identified and a wear model developed. This model is based on the experimental observations, analysis of the test data and principles adopted from the field of Tribology. Comparisons of predicted and measured wear show good agreement.