Particle Flow Simulation of Sand Loss through Cracks in Segmental Linings

Abstract

In order to investigate the problem of formation collapse caused by sand leakage from segmental lining cracks, this paper selected the logical idea of the silo calculation example in PFC3D and used numerical triaxial compression to calibrate the parameters of sand particles. By simulating the changes in the contact force chain between sand particles, the bottom plate load and the porosity of the sand layer during the process of layer collapse caused by sand leakage from segmental lining cracks, the layer subsidence and sand inrush phenomena, sand flow and loss laws of the sand layer due to different openings are studied. The results show that the dynamic process of continuous formation and destruction of the soil vault leads to continuous changes in the contact force between sand particles when the segmental lining cracks cause strata subsidence. The microscopic reason for the sand intrusion disaster was that after the thickness-to-span ratio exceeded the critical value, the soil arch continued to develop towards the top surface and the top surface was connected to the opening, resulting in the inability to form a stable soil arch between the sand particles. During the loss of sand, the change in load on the bottom plate and the change in porosity at the opening corresponded to the process of destruction and formation of the soil arch. Whenever the soil arch was formed, a local peak appeared in the load curve on the bottom plate and the porosity curve at the opening. In the later stage of the sand loss process, as the loss rate increased, the frequency of soil arch formation and destruction accelerated accordingly.