Experimental Investigation of Loess Slope Failure Modes under Varying Water Head Conditions

Groundwater is an important factor inducing slope instability, but there is limited research on the characteristics of deformation evolution and failure modes of loess slopes under the action of different water heads. In this paper, the loess slope is taken as the research object, and two sets of model tests are carried out, which correspond to the low head of 0.02 MPa and the high head of 0.06 MPa respectively. The failure process of slope instability under different water head heights is recorded, and the crack evolution characteristics and failure modes are analyzed. The experimental results show that as groundwater infiltrates, the wetting front develops from the rear to the front of the slope, and the slope gradually becomes saturated from the rear to the front and from the bottom to the top; the main deformation area of the slope occurs in the settlement at the top and the cracks on the slope surface; the direction of crack evolution develops from the front edge to the rear edge of the slope, and its development aggravates the deformation and failure of the slope; groundwater infiltration drives the soil particles in the slope body to accumulate from the rear to the front, weakening the cementation between soil particles, reducing its shear strength, and thus causing slope instability and failure. In the low water head state, the deformation and failure mode of the loess slope is: slope toe liquefaction → slope surface traction-type collapse → slow instability of the slope body. In the high water head state, the deformation and failure mode of the loess slope is: slope toe liquefaction → slope surface traction-type collapse → slope top settlement → overall sudden instability. This study has important engineering practical significance. The research results can provide theoretical basis for slope reinforcement design, and after the completion of slope construction, in terms of relevant failure parameter indicators, it can provide reference for the design of slope safety monitoring and early warning system.