Particle-scale insight into soil arching under trapdoor condition

Soil arching is an important phenomenon in the discussion on soil-structure interactions. Soil arching can increase the stresses exerted on a buried structure, while the absence of soil arching often results in differential surface settlement due to the difference in stiffness between the structure and the surrounding subsoil. In this investigation, model tests were conducted to relate the particle-scale responses of non-cohesive granular soils to the development of soil arching using spherical glass beads and two types of sandy soil. The trapdoor test apparatus, equipped with load cells, was used to measure both normal and shear stresses applied at the base. To explore the micromechanics of soil arching, complementary discrete element method simulations were performed using two types of particle shape: spherical particles and non-spherical particles, constituted by two adjoining spheres with a rigid connection. The results show that both sample height and particle shape play a vital role in arching behavior. Soil arching tends to develop as the ratio of the sample height to the width of the buried structure increases. The applied stresses on the buried structure are found to increase with increasing sample density and angularity of particle shape due to enhanced particle interlocking. Furthermore, the distribution of shear stress on the buried structure can be used to judge the presence or absence of a fully developed arch.