Evolution and mechanism of passive arching in sand: physical and numerical modeling trapdoor problem

Uplift or pullout problem in geotechnical engineering issues involve passive soil arching effect. This study presents a series of experimental and numerical investigation on passive arching behavior in sand over a trapdoor. A transparent trapdoor test box, particle image velocimetry technique, and a series of sensors were used to capture the soil mass displacement, shear strain, stress, and load displacement curve during passive arching process. The surface upheaval, horizontal displacement, and volumetric change of sand layer as the passive arching process were quantified. Combining with a series of finite element limit analysis and multiplier elastoplastic finite element analysis, the passive arching behavior of load–displacement response, progressive failure, and stress transfer behavior have been comprehensively presented and evaluated. Initially, companied by compression deformation, a linear increase in load has been recorded. A pair of shear bands formed from the edges of the trapdoor, acquiring an approximately rectangular or inverted trapezoidal failure zone with weak intensity of shear strain. Then, pairs of shear bands with larger inclination angle, surrounding a trumpet-shaped influence zone. When the maximum arching is mobilized, the shear bands extended the surface with maximum inclination angle. The study can provide useful visualized data for modelling a displacement dependent uplift resistance and predicting the sand deformation above an uplifting structure.