Development and application of the Bi-Elliptical Displacement Controlled Method for shallow large-diameter tunnels

Displacement-Controlled Methods (DMs) for tunnelling simulations have demonstrated effectiveness when the focus is on ground displacements rather than on structural forces within the tunnel lining. The accuracy of DCM predictions largely depends on adopting a realistic displacement pattern. Among the various DCMs, the Circular DCM is one of the most commonly adopted. However, some researchers have pointed out that tunnel excavation profiles do not always conform to circular shapes. Although the Circular CM has been successfully applied in many cases, particularly for conventionally sized tunnels, its limitations become evident in shallow and large-diameter tunnels. where significant variations in soil stress and stiffness with depth are expected. In such cases, considering non-circular displacement patterns is crucial for achieving accurate predictions. In the following, the Bi-Elliptical CM is presented