Experimental research on hydrophilic characteristics of natural soft rock at high stress state

In order to study features of rock–water interaction, a self-developed experimental system called Intelligent Testing System for Water Absorption in Deep Soft Rocks (ITSWADSR) was utilized to analyze the hydrophilic behaviors of natural soft rock at high stress state. Combining X-ray diffraction and mercury injection test, main influencing factors on hydrophilic characteristics were studied. According to the results, it could be concluded as the following: (1) the effective porosity, and the content of illite, illite/smectite formation (S = 5%) and kaolinite have positive correlation with the water absorption capacity of rock; meanwhile, the initial moisture content, fractal dimension of effective pores, illite/smectite formation (S = 30%) and chlorite present negative correlation; (2) among the positive factors, the ascending order is kaolinite, illite/smectite formation (S = 5%) and illite; (3) the descending order among the negative factors are chlorite, illite/smectite formation (S = 30%) and fractal dimension of the effective pores; (4) influence of effective porosity on the pressurized water absorbing capacity of rock is minimal, while it is maximal in the process of no pressurized water absorption.