Evolution of Load Reduction for High-Filled Cut-and-Cover Tunnels Subjected to Soil Creep

Abstract

The excessive load from the high embankments of high-filled cut-and-cover tunnels (HFCCTs) threatens the safety and stability of HFCCTs. Relatively low-compacted (RLC) soil can reduce such loads in the short term, but the long-term ability of RLC soil to reduce the load on HFCCTs is unknown. The changes in the soil arching effect that are resulted from soil creep needs to be considered carefully in HFCCT design. Three stages of analysis were conducted in this study: immediately after backfilling (0 month), during backfill creep, and after the soil deformation has stabilized (240 months/20 years). A finite difference program, FLAC3D, was employed to investigate the soil’s vertical earth pressure and displacement distribution around a cut-and-cover tunnel (CCT). The Burgers model was used to simulate the creep behavior of the soil. In addition, parametric studies for different dimensions and locations of RLC soil were conducted. The results show that the soil arching effect that is due to the inclusion of RLC soil works well initially to reduce the load but eventually disappears, which can result in a significant load rebound greater than 100 kPa and jeopardize the stability of the HFCCT.