Theoretical prediction models for ground settlement during box jacking

Abstract

Box tunnels, compared with circular tunnels, can increase the space utilization ratio by approximately 20% and have been increasingly used in urban underground space. Box jacking generates more ground loss due to its special geometric shape, inducing larger ground settlement, compared with circular pipe jacking. Accurate prediction of ground settlement during box jacking is a key aspect for the success of a project. This paper proposes the ground settlement prediction models during box jacking based on stochastic medium theory and cavity expansion theory, and compares the applicability of the models. The comparison shows that the modified Verruijt model based on the cavity expansion theory can provide a relatively accurate prediction for the magnitude and trough width of the ground settlement. The analytical model is validated through numerical simulation and field instrumentation using the project of Shilianjie Station of No. 5 metro line in Suzhou, China as a testbed. The validation shows that the analytical predictions compare reasonably well with the numerical simulation results and field measurements with a maximum error within 13%. The analytical model in this paper can provide a quick estimate on the ground settlement during box jacking.