Pore structure characteristics of an underground limestone chamber in the Three Gorges Reservoir area

摘要

Water–rock interaction is a common phenomenon in rock mass engineering. Water–rock interaction alters the mineralogicaland microstructural properties of a rock mass and leads to engineering problems such as leakage, deformation, and failureof a rock mass. To investigate the local leakage in the limestone reservoir, limestone specimens were taken from the undergroundchamber. In this study, two test conditions were designed: with and without regular replacement of the reservoirwater condition. The results indicated that the porosity increased sharply in the early stages of the soaking. But, the rateof increment dropped after 120 d (regular replacement of reservoir water condition) and 90 d (unchanged reservoir watercondition), respectively. The pore in the rock was 4.50 mm deep, while the reservoir water was replaced regularly, which is1.54 times that of the unchanged reservoir water condition (i.e., 2.50 mm), in 360 soaking days. Relatively, the renewal ofreservoir water enhanced the chemical reaction. The water–rock interaction altered the mineralogical composition, spatialstructure of the crystal, and pore structure of the rock. The change in the longitudinal wave velocity Vm measures the stateof pore development. The porosity evolution model for limestone rock was established by considering the impact of dissolutionon the spatial structure of the crystal skeleton. The model accurately predicted the variation trend of porosity in thelimestone rock under water–rock interaction.