To study the water absorption characteristics and microscopic evolution law of strongly and moderately weathered siliceous slate under water-rich environment,the immersion test,scanning electron microscope test and X-ray diffraction test were conduced on the strongly and moderately weathered siliceous slate in Jiuzhai Tunnel of Yuxi-Chuxiong National Expressway.The results show that the water absorption process of strongly and moder-ately weathered siliceous slate under water-rich environment can be divided into three stages:rapid water absorp-tion(0-2 hours),slow water absorption(2-24 hours)and dynamic equilibrium water absorption(more than 24 hours).In the stage of rapid water absorption,the rock structure becomes loose,and pores and microcracks gradu-ally extend and develop.During the slow water absorption stage,the cement dissolves and falls off,and rock fur-ther loosens,producing further pores and cracksand forming obvious penetrating cracks gradually.In the stage of dynamic equilibrium water absorption,the looseness of rock structure and the development of pores and fratures basically reach a stable state.The main mineral components of strongly and moderately weathered siliceous slate are quartz and clay minerals.In water immersion test,the relative content of quartz increases,but clay minerals decrease.Clay minerals,such as illite and illite-montmorillonite mixed layer,are extremely unstable when ex-posed to water.They can not only react chemically with water and transform into quartz and other clay minerals,but also react physically with water,showing the characteristics of swelling,crushing and decomposition.The research results can provide reference for the theoretical research of water absorption and softening of strongly-moderately weathered siliceous slate.
water-rich environmentstrongly-moderately weathered siliceous slatewater absorption behaviormicroscopic evolution law