Experimental Analysis on Mechanical Characteristics of Narrow Backfill behind Foundation Pit Diaphragm Wall

In order to study the failure mode and pressure distribution characteristics of narrow cohesionless backfill, relying on the test model box that can simulate different complex working conditions, the active earth pressure model tests in translational mode are carried out. The process of destruction during the parallel movement of the backfill with the retaining wall was recorded by a digital camera. Particle image velocimetry technology was used to analyze the deformation characteristics of narrow cohesionless backfill and the failure form. The measured active earth pressure was compared with the theoretical solution. The test results show that the change of the geometric conditions of the finite backfill affects the failure mode of the backfill. The limitation of the boundaries on both sides is the main reason for the multiple sliding surfaces inside narrow backfill under the translational mode. The sliding surfaces are presented as curved surfaces. The active earth pressure value increases with the increase of aspect ratio. Under the semi-infinite soil state, the active earth pressure value is close to the Coulomb earth pressure. The first "reflection point" moves up with the increase in the inclination of the retaining wall, and also moves up with the increase in the inclination of the natural slope. As the limited backfill area increases, the active earth pressure also increases.