Evolutionary mechanism of passive soil arching effect in sand at various relative densities and heights of fill

This study presents a series of trapdoor tests on dry sand at various relative densities and heights of the sandy fill to investigate the evolution of the passive soil arching effect with the upward movement of the trapdoor. During the test, the shear strain, the displacement contour and the soil stress were monitored. The testing results indicate that the evolution of passive soil arching effect is highly dependent on the trapdoor/loading displacement and the shear band. As the trapdoor displacement increases, the passive soil arching effect evolves from the initial state to the maximum arching state, with the soil stress on the trapdoor and the inclination angle of the shear band (equal to the dilatancy angle of sand) increases to the maximum value. With the continuous increase of the trapdoor displacement, stress recovery occurs until the ultimate arching state. Beyond the ultimate arching state, the passive soil arching effect remains relatively stable regardless of the trapdoor displacement. At a higher relative density of fill or a higher fill height, the influencing range of the disturbed zone increases, along with a more distinct passive soil arching effect.