Effect of densification on shear strength behavior of argillaceous siltstone subjected to variations in weathering-related physical and mechanical conditions

In order to study the effect of densification due to weathering on the strength behavior of soft rocks, this paper presents results of consecutive weathering and direct shear tests performed on an argillaceous siltstone. A specimen prepared with fresh argillaceous siltstone first underwent combined water and temperature variations under various stresses. Densification in weathering-related physical and mechanical conditions was indicated by measured dry densities. Then the weathered specimen was subjected to direct shear without remolding. The effect of densification during weathering on the shear strength behavior obtained from the subsequent direct shear tests was discussed. The study highlights that: (1) Densification during weathering is significant at stress values greater than 200 kPa. (2) Weathering leads to a 44% strength reduction of the fresh material with a stress of 50 kPa. (3) Weathering induced densification with a stress of 1400 kPa enhances the shear strength of the fresh material up to 259%.