Interaction of Soil Arching under Trapdoor Condition: Insights from 2D Discrete-Element Analysis

The trapdoor/trapdoor-like model test has been widely utilized to investigate the evolution of soil arching. However, the primary focus of previous studies has been on the mechanical and deformation behaviors of the arching field under the single-trapdoor condition, while the interaction of soil arching between adjacent trapdoors has not been well understood. In this paper, a series of discrete numerical models based on the plane–strain laboratory trapdoor test were established to investigate the interaction effect, with respect to stress redistributions, particle movement, anisotropy of contact forces, and energy regime. The effects of motion mode, namely the simultaneous and nonsimultaneous movement, and the spacing (B) between adjacent trapdoors on the arching performance were examined. The numerical results revealed that the simultaneous movement of twin trapdoor slightly influences earth pressures resting on the surface of both trapdoors. The deformation pattern is deeply influenced by a narrow spacing of 0.25B and characterized by two arching fields interacting with each other, resulting in a noticeable subsidence at the crest. The subsequent lowering of the second-lowered trapdoor under the nonsimultaneous movement condition increases pressures resting on the first-lowered trapdoor, yields additional settlement within the former arching field, and distorts adjacent arched force chains. An increase in spacing from 0.25B to 1B is beneficial for reducing the pressure increment, decreasing the arching deformations, minimizing the rotation of the major principal direction, and decreasing the friction energy distribution density above the stationary supports.