Abstract: In this paper, the sandstones of the Huangmaqing Group (T2h) were taken as the study object. The compressive and tensile tests were carried out on the rock samples, considering the influencing factors of the slope along the Qinhuai East River in Nanjing city. Since water is the main factor that affects the stability of the excavated slope, both the natural and saturated soaking-drying cycles were taken into account during the experiments. Based on the experimental results of the sandstones, the void and deterioration characteristics and deteriorating mechanism were analyzed in detail. With the increasing number of the soaking-drying cycle, the compressive and tensile strengths, and the cohesion of the sand rock samples all gradually deteriorate. The more the cycle numbers, the more serious damage of the rock mass, which indicates that the cycles have cumulative damage on the samples. Under the natural water absorption conditions (no water entering the small open voids), the strength and modulus of the rock slowly decrease. However, under the saturated water absorption conditions (the small open voids are filled with water), the strength and modulus rapidly decrease, which indicates that the deterioration effect due to existence of the small open voids is obvious. The micro-structures indicate that the voids in the rock increase with the number of soaking-drying cycle. Combined with the shear strength characteristics results, the declination of the cohesive strength is the main factor of rock strength deterioration, and the frictional strength almost has no change. The cycles lead to the water-rock reaction, causing gradual loss of rock particle cementation and cracking of the edges, and the rock is degraded in macroscopic scale. Research results have an important reference for the study of stability of new excavation slope, and provide favorable evidences for the long-term stability analysis of river bank slopes.

Key words: sandstone, deterioration due to water, test, void characteristic, natural water absorption, saturated water absorption, soaking-drying cycle