Due to the construction of adjacent foundation pit

the tunnel is assumed to be an elastic continuous beam to simulate its stress and deformation

which could estimate the influence on existing metro tunnel more rationality and rapidly. A coupled finite element balance equation is deduced for analysing the interaction between the tunnel and surrounding soil mass. Meanwhile

an elastic layered half-space model is adopted to investigate the effects of the foundation pit unloading on the deformations of soil mass and tunnel. A coupling method is proposed to estimate the influence on adjacent tunnel due to foundation pit excavation in layered soil. Furthermore

the proposed method is compared with the two-stage method through a case study and is verified with the centrifuge results and measured results in site. Results show that

compared with the two-stage method

the coupling method can reflect the concentrations（or dispersion） of stress and strain in layered foundation soil. The proposed method can not only obtain more accurate results

but also reduce parameter numbers during calculation. The theoretical calculation results are basically consistent with that the results from centrifuge tests and measurements on site

which verifies the validity of the proposed approach. Useful conclusions obtained through practical applications may provide the certain theoretical basis for the rational development of protective measures for the construction of urban foundation pits on the adjacent tunnels.