The influence of moisture on sandstone properties in Iran

The presence and the behaviour of discontinuities are a dominant influence on the stability of rock slopes. Water has a profound effect on the shear behaviour of discontinuities. Several catastrophic failures of natural rock slopes have occurred as a result of pore water pressure build-up in jointed rock. The Khosh-Yeylagh main road is situated in north-eastern Iran, and connects Semnan province to the northern provinces. This region contains numerous rock slopes subjected to significant seasonal rainfall, which results in a great change in the discontinuity strength components followed by increased risk of failure. In this paper, the effect of moisture on the properties of sandstone discontinuities is experimentally investigated. For this purpose, large numbers of rock samples containing natural discontinuities were collected from slope faces, and then large- and small-scale tilt tests and multi-stage direct shear tests were performed under both dry and wet conditions. Finally, statistical analyses were carried out on the collected data. It was observed that under low levels of normal load the presence of water significantly influences the shear behaviour of sandstone discontinuities.