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| Experimental study on deterioration of the tensile strength of red sandstone during the operation of reservoir |
| ZHANG Zhenhua1，HUANG Xiang1，CUI Qiang2 |
| (1. School of Civil Engineering，Hefei University of Technology，Hefei，Auhui 230009，China；2. China Electric Power Research Institute，Beijing 102401，China) |
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Abstract Red sandstone is widely distributed in the drawdown area of Three Gorges Reservoir，China. Understanding the mechanisms of deterioration of the tensile strength of red sandstone under cyclic wetting-drying during the operation of reservoir is therefore very important for the stability evaluation to the slopes of red sandstone. The red sandstone samples from Majiagou landslide were taken for splitting test to measure the tensile strength under water pressure and cyclic wetting-drying conditions using the test system developed in house. The system can apply the water pressure and wetting-drying cycles. Meanwhile，the tensile strength deterioration of the red sandstone in drawdown area was discussed based on the results of SEM tests，XRD tests and water absorption tests. Experimental studies show that the tensile strength of the red sandstone under water pressure and cyclic wetting-drying conditions decreases gradually with the increasing of the number of wetting-drying cycles. The decreasing rate of the tensile strength after the first wetting-drying cycle is much greater than that after the latter wetting-drying cycle. After the fourth wetting-drying cycle，the decreasing rate of the tensile strength approaches zero，indicating that the tensile strength keeps nearly constant. The tensile strength degradation of the red sandstone is a cumulative process of damages resulting from the expansion of clay minerals due to hydration during wetting process，the shrinkage of clay minerals in the period of drying process，and increasing and propagation of micro pores and cracks under water pressure. The weakening effect of cementation between detrital minerals and cements caused by the hydration of clay minerals under cyclic wetting-drying conditions plays a main role for the degradation of the tensile strength.
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2017, Vol. 36 
