Application of Three-parameter Model in Settlement Calculation of Immersed Tube Tunnel

The settlement of immersed tube tunnel is mainly caused by the compression of basal layer and recompression of the ground foundation layer. Defining the composite foundation as a combination of basal layer of immerse tube tunnel and ground foundation layer, a three-parameter model is proposed in this study to simulate the composite foundation in which the basal layer was represented using springs and the ground foundation layer by Kelvin's model. Based on the solution of beam on elastic foundation, analytical solution for settlement of immersed tube tunnel using the proposed three-parameter model was derived by means of Laplace transformation according to the correspondence principle and the constitutional relationship of the three-parameter model. Initial and final settlement as well as variation of settlement in terms of time were calculated and compared with the actual measured data in combination with actual data measured during tunnelling of Shenjiamen immersed tube tunnel in Zhoushan City. Results showed that the proposed three-parameter model is capable of replacing the basal and ground foundation layers. The calculated value matched favourably with the actual measured value and the variation of settlement in terms of time for immerse tube tunnel can be represented.