Model Test Study on Deformation Characteristics of a Fissured Expansive Soil Slope Subjected to Loading and Irrigation

Expansive soils are characterized by repeated swelling and shrinkage. They cause great damage to engineering projects because of their expansiveness, over-consolidation and propensity to crack. However, the impact of cracks on the stability of an expansive soil slope during loading and irrigation is not yet fully understood. This study aimed to investigate the relationship between slope state and crack development in fissured expansive soils. A series of physical model tests with different types of cracks were conducted, in which the fissured expansive soil slopes were subjected to different loadings (1.6, 3.2, 4.8, 6.4, 16 MPa), and irrigated at a flow rate of 25 mL/min. The VIC-2d software, which utilizes the digital image correlation principle, was used to quantitatively obtain the horizontal and vertical strain data of the slope model. The closure and opening of cracks, and the slope state after loading and irrigation were monitored by strain data analysis using VIC-2d software. The results indicate that the excessive overlying stress revives the existing cracks and produces sliding along the crack interface. The sliding surface of the fissured expansive soil slope became shallower due to the water infiltration. It was demonstrated that the middle and foot of the fissured expansive soil slope were the key positions for reinforcement from the perspective of the mutual transformation of tensile strain and compressive strain on the surface of the slope. It is of great importance to study the relationship between the crack strain state and deformation trend of a slope subjected to loading and infiltration to understand the progressive surface- or shallow-layer sliding mechanisms, and reinforce key areas of the slopes in areas containing moderately or strongly expansive soils with abundant cracks.