Abstract: In light of the present situation of engineering rock mass stability control problem caused by strength deterioration of rock under wetting-drying cycles, taking the coal seam roof No.8 medium grained feldspar quartz sandstone of Baode coal mine in Xinzhou, Shanxi province, China, for example, modified tests by organic silicon material were carried out. The strength damage and deterioration rules of sandstone for modified and unmodified under different wetting-drying cycles were studied by uniaxial compression tests; the change rules of surface zeta potentials of sandstone for modified and unmodified were comparatively analyzed by electrophoresis; and modification mechanism of organic silicon material modified sandstone is discussed. The results show that: (1) The uniaxial compression strength (UCS), elastic modulus (E) and deformation modulus (Ed) of sandstone samples are increased obviously by modification, and raising the UCS, E and Ed of sandstone samples by 2.17%, 22.2% and 23% respectively. (2) The strength deterioration effect is obvious under wetting-drying cycles; and the UCS, E and Ed of sandstone samples decrease by negative exponent relationship with wetting-drying cycle times increase. (3) Organic silicon material greatly affects the surface of electrical behavior of sandstone; with the pH values of sandstone suspension samples decreasing, the surface electrical potential of sandstone varies from electronegative to electrically neutral and to electropositive in the end.

Key words: sandstone, uniaxial compressive strength, organic silicon material, zeta potential, modification