Analysis on Additional Response of Existing Tunnel

Abstract

With continuously upgrading and transformation of the urban infrastructure such as railway, road, subway, municipal engineering etc., the scale and the amount of urban underground construction are apparently enlarged. Thus, the newly-built urban underground construction will inevitably face close-space construction or even super close-space construction in the situation of tight urban land, complex underground pipelines and highly three-dimensional architectural layout. The negative environmental effects of the underground engineering construction closed to an existing building have been systematically and thoroughly studied according to the present research results. However, there is insufficient attention paid to the negative environmental effects induced by the construction of a deep foundation pit of narrow and long subway station "parallel with the existing subway section for a long-distance"

Therefore, taking the deep foundation pit of narrow and long subway station "parallel with the existing subway section for a long-distance" in soft clay as a research subject, the ground movement induced by deep foundation pit construction and the additional response of the existing subway section is studied in this thesis

First, the supporting structure deformation and ground settlement induced by the construction of a deep foundation pit of a narrow and long subway station in soft clay and the additional response of the existing subway section are analyzed through numerical simulation method, and the calculation results are compared by utilizing two constitutive models (i.e., Plastic-Hardening model and Mohr-Coulomb model). The results show that the negative environmental effects induced by the construction of a deep foundation pit of narrow and long subway station parallel with the existing subway section for a long- distance are significant and should be paid high attention to. By contrast to the Mohr- Coulomb model, the calculation results using Plastic-Hardening can reflect the characteristic of the deformation for soft clay induced by the construction of deep foundation pit of a narrow and long subway station.

Moreover, a parametric study is conducted by utilizing the Plastic-Hardening model in which the influence of the horizontal distance between the existing subway section and long and narrow deep foundation pit as well as the buried depth of existing subway section and other critical factors on the additional response of the existing subway section induced by the deep foundation pit. The results show that both the horizontal distance between the existing subway section and the long and narrow deep foundation pit as well as the buried depth of the existing subway section has a great impact on the additional response of the existing subway section. The additional response of the existing adjacent subway tunnel decreases with the horizontal distance between the existing subway section and the long and narrow deep foundation pit becoming larger

Keywords: deep excavation, existing tunnel, soft-soil, deformation, plastic-hardening, constitutive model, Mohr-Coulomb

DOI: 10.7176/CER/16-1-06

Publication date: May 31^st 2024