Mechanism of permeability evolution under stress-seepage coupling in concrete for drilling shaft lining of water-rich weakly cemented formations

To reveal the evolution mechanism of concrete permeability under stress-seepage coupling in drilling shaft linings of water-rich and weakly cemented formations, this study conducted an experimental investigation on concrete permeability under various combinations of confining pressure and osmotic water pressure. The analysis focused on the correlation between concrete permeability and crack evolution under stress-seepage coupling. The results can be summarized as follows. 1) elevated confining pressure led to significant shear damage in concrete, whereas increased osmotic water pressure intensified the tensile-shear damage characteristics of concrete. 2) Throughout the entire loading process, the concrete permeability followed a pattern of initial decrease, gradual increase, and subsequent rapid growth, with the peak permeability occurring after the peak of the stress-strain curve. 3) The crack circumferential strain better reflected the transition of concrete permeability into the stage of unstable crack extension. 4) Based on the experimental results and theoretical analysis, an equation was derived to establish the relationship between concrete permeability and damage variables with a fitting coefficient greater than 0.8. 5) The permeability of the concrete shaft lining under fluid-solid coupling was obtained by modeling tests. The findings of this study provide a foundation for the design of drilling shaft linings in water-rich and weakly cemented formations in the western regions, as well as for water control measures in wellbores.