(1. Research Center of Coastal and Urban Geotechnical Engineering，Zhejiang University，Hangzhou，Zhejiang 310058，China；
2. Engineering Research Center of Urban Underground Development of Zhejiang Province，Hangzhou，Zhejiang 310058，China；3. Institute of Geotechnical Engineering Science，Hohai University，Nanjing，Jiangsu 210098，China；4. Faculty of Engineering，China University of Geosciences(Wuhan)，Wuhan，Hubei 430074，China；5. Key Laboratory of Geotechnical and
Underground Engineering of Ministry of Education，Tongji University，Shanghai 200092，China)
Abstract：The excavation of the basement will break the original stress field of ground and hence has an unfavorable effect on the underlying tunnel. In this paper，a new simplified method is developed to evaluate the response of the existing tunnel duo to the unloading of the basement excavation. Firstly，the Euler Bernoulli beam resting on the Pasternak foundation was used to simulate the interaction between the existing tunnel and ground，and the coefficient of subgrade reaction considering the effect of the burial depth of the existing tunnel was adopted. Secondly，the ground displacement at the tunnel center induced by basement excavation was obtained with the application of Mindlins solution，. Then，a deformation control equation of tunnels was established based on the displacement coupling condition between the existing tunnel and the ground. Finally，the solution of the longitudinal response of the existing tunnel caused by adjacent excavation was obtained using the finite difference method. The accuracy and applicability of the proposed method were verified by comparison with the three-dimensional finite element method analysis and theoretical solutions published in other literature，and the influence of different factors on tunnel response was analyzed including the tunnel buried depth，relative space position between the basement and the existing tunnel，the excavation depth of the basement，the geometry of the basement，the relative rigidity between the existing tunnel and the ground，etc. Finally，a simplified formula for predicting the maximum vertical displacement of the tunnel induced by excavation was presented. The results could provide some theoretical support for similar projects.
2020, Vol. 39 
