A New Analytical Model for Trapdoor Tests Considering Effect of Incomplete Soil Arching and Principal Stress Deflection

Since the ground reaction curve (GRC) is a useful tool for evaluating the formation deformation and the load acting on an underground structure, it is critical to determine the GRC, especially under small strain conditions. In this paper, a new analytical model considering the progressive development of loose soil was proposed to describe GRC in trapdoor tests. The proposed model is composed of an undisturbed zone, unloading zone, failure zone, and self-weight zone. The key parameters of the proposed model were determined through the existing literature. In addition, the formulas for calculating the lateral pressure coefficient and the height of the failure zone were derived, respectively. Considering the continuity of the principal stress deflection and lateral pressure coefficient in the unloading zone, and assuming that the unloading zone is a three-hinged arch with reasonable arch axis, the load transfer expression in the unloading zone was deduced. Then, based on the limit equilibrium theory, the vertical stress acting on the trapdoor was obtained. The effectiveness of the proposed model was verified by comparing the calculation results of the proposed model with model tests, a theoretical model, and a simplified model. Finally, the influence of the key parameters of the proposed model on GRC was discussed in detail. This work provides a meaningful reference for estimating the GRC.