Mechanical response characteristics and seepage evolution mechanism of shaft lining concrete under different stress states

Abstract

This study investigates the mechanical response characteristics and seepage evolution mechanisms of shaft lining concrete across different stress states. The mechanical behavior of the concrete was analyzed through stress-strain curves, volumetric strain patterns, elastic modulus, crack initiation stress, damage stress, and other relevant parameters. The relationship between permeability evolution and axial strain, volumetric strain, and circumferential crack strain was established, along with the seepage characteristics of shaft lining concrete under different loading conditions. The results demonstrated that the peak strength of specimens undergoing graded loading and unloading was consistently lower than that of specimens subjected to continuous loading under the same confining and seepage pressure conditions, exhibiting a difference of 5.1 %. Furthermore, the inflection point of the volumetric strain in specimens subjected to graded loading and unloading occurred earlier. The elastic modulus of the specimens across varying stress states increased with higher confining pressure and decreased with increasing seepage pressure. The crack initiation stress and damage stress for specimens undergoing graded loading and unloading were lower than those for specimens subjected to continuous loading, with reductions of 34.4 % and 10.5 %, respectively. The permeability-axial strain relationship curve showed an initial decrease, followed by a subsequent increase. The volumetric strain exhibited two distinct phases—compression and expansion—under the applied deviatoric stress. The minimum permeability values for specimens undergoing graded loading and unloading and continuous loading occurred at 84.6 % and 89.2 % of the maximum volumetric compression and density points, respectively. Under the same external stress conditions, the crack circumferential strain inflection point for specimens subjected to graded loading and unloading occurred earlier than that of specimens under continuous loading, accompanied by a sharp change in the permeability curve.