Additional stresses of disturbed soils induced by shield tunneling based on fictitious force method

The current researchers pay little attention to the additional stresses of disturbed soils caused by shield tunneling, and all the existing results are based on the assumption of homogenous soils. A theoretical approach, combined with the fictitious force method based on the basic solution for layered foundation, is proposed to analyze the additional stresses of disturbed soils induced by shield tunneling considering the layered effects. The additional stresses induced by the bulkhead additional pressure and the propulsion friction force between the shield machines and the surrounding soils are emphasized. A tunneling case in Shanghai for layered foundation is employed to analyze the distribution rules of the additional stresses caused by tunneling. Furthermore, the comparative researches with a case of homogenous soils are also conducted to study the effects of layered characteristics on disturbance stress field. The results show that the distribution rules of the additional stresses caused by the propulsion friction force are similar to those induced by the bulkhead additional pressure. The additional stresses attenuate quickly in the region close to excavation opening, and the influence sphere is generally small. The additional stresses attenuate slowly in the region away from excavation opening. The construction risk due to the friction force and bulkhead additional pressure should be highlighted. In addition, there are great differences in the characteristics of the stress fields with and without considering the layered effects. Therefore, the influence of non-homogenous soils should not be ignored in the design. It may provide a certain basis for correct preparation of protective measures of adjacent pipelines and buildings induced by shield tunneling in layered soils.