Mechanical degradation behavior and damage constitutive model of muddy siltstone under cyclic wetting and drying conditions

Aiming at the deterioration of the mechanical properties of mud siltstone in northern Guangxi Province under the action of wet and dry cycles, uniaxial compressive strength tests and SEM tests with different numbers of wet and dry cycles were carried out, and based on the law of energy evolution, the complete compaction point of mud siltstone was determined, and the segmental damage constitutive model of mud siltstone was constructed. The results show that: (1) After five dry and wet cycles, the uniaxial compressive strength and modulus of elasticity of the siltstone decreased by 90.7% and 81.5%, respectively, and the damage mode changed from shear damage to tensile-shear composite damage. (2) The point where the dissipated energy is equal to the elastic strain energy is determined as the complete compaction point, and the compaction strain increases linearly with the increase of the number of dry-wet cycles. (3) The fitting results of the segmental damage constitutive model match well with the experimental data, which can more accurately describe the deformation and damage characteristics of muddy siltstone under the action of wet and dry cycles. The results of the study provide data support and theoretical reference for the stability of slopes subjected to rainfall-exposure cycles in Northern Guangxi.