Effect of aqueous solution chemistry on the swelling of clayey rock

• The swelling of clayey rock was clearly anisotropic.
• The swelling of clayey rock was dependent on the concentration of aqueous solution.
• The more concentrated the solution, the weaker the swelling.
• The swelling of clayey rock was not directly correlated with the concentration of anions.

Clayey rock has a large clay mineral content. When in contact with aqueous solutions with different chemical properties, the rock expands considerably and presents a significant hazard to the stability of underground excavations. The swelling behaviour of Cenozoic clayey rock from Shandong Province, China, was investigated when subjected to various aqueous chemical solutions, using the free swell test method. The influence of different chemical paths on the swelling of clayey rock was analysed, and the basic mechanisms of the swelling and shrinkage variability of clayey rock were analysed by SEM–EDS. The results demonstrated that the swelling of clayey rock was clearly anisotropic, quantified by the swelling anisotropy coefficient. Swelling was independent of the chemical path, but dependent on the concentration of the aqueous solution. The more concentrated the solution, the weaker the swelling.