Upward soil arching effect under unloading: mechanism, theory and engineering application

Upward soil arching effect under unloading indicates the unloading part moves in a vertically downward direction, generating the arching zone and the loosened zone towards an upward direction. This study presents a summary of definitions, characteristics, theoretical models and engineering applications for the upward soil arching effect under unloading. The evolution of the upward soil arching effect is highly related to the unloading/differential displacement. The characteristics of the upward soil arching effect under unloading are comprehensively interpreted in terms of the normalized height of arching, the minimum soil arching ratio (at which state the maximum arching is developed) and the normalized unloading displacement to reach the maximum arching state. Two deformation-dependent theoretical models are introduced, to appropriately interpret and predict the variation of the soil arching ratio with the normalized unloading displacement (i.e., the ground reaction curve). Using the research findings for the upward soil arching effect under unloading, the settlement of the geosynthetic-reinforced pile-supported embankment as well as the face stability and ground settlement during tunnelling are proven to be precisely predicted and well controlled.