Structure optimisation of a diaphragm wall with special modelling methods in a large-scale circular ventilating shaft considering shield crossing

In the design of a circular diaphragm wall, it is most important to determine the number of wall panels and vertical joint stiffness to achieve a desired retaining structure style. In this paper, a numerical model with special methods considering the modelling of panel joints and shield crossing the ventilating shaft was proposed: the joints between panels were simulated with the hinge mode of connection type, the interaction between surrounding soils and diaphragm wall simulated with ground springs, and the excavated soils within the shield tunnel simulated with solid elements were performed to model the stress release when shield crossing. With this model, six different operating cases considering the change of number of panels and joint stiffness were analysed in the Meizizhou ventilating shaft. The numerical results suggested the diaphragm wall with 24 panels and joint stiffness 100% of the panel stiffness (i.e., case 1) was optimal considering shield crossing the shaft in terms of evaluating the displacements, hoop stresses and vertical bending moments of wall panels.