Effects of bending stiffness and interface roughness on tunnel-embedded wall interaction

In urban area tunnelling projects, preventing the adverse effects of tunnel construction on nearby structures often involves the use of embedded walls or piles. Designing the key parameters of these embedded structures is challenging due to the complex interaction between the soil and the structure. This paper presents a numerical investigation into the effects of embedded wall bending stiffness and soil-wall interface roughness on tunnel-wall interaction in sandy ground. Three dimensional numerical models were developed to simulate tunnel construction near an embedded wall with varying parameters, with sand behaviour simulated using a hypoplastic constitutive model calibrated by element tests and centrifuge models. The findings reveal that a decrease in interface roughness enhances the wall’s effectiveness in reducing tunnelling-induced settlements, while a decrease in wall bending stiffness reduces its performance in mitigating surface settlements and increases the wall bending moment. Based on the results, an improved design chart was developed by introducing correction coefficients for wall depth, taking into account the effects of wall stiffness and interface roughness on the wall’s efficiency in reducing tunnelling-induced settlements. This chart aims to assist engineers in quickly determining the preliminary horizontal locations and depths of embedded walls, ensuring both safety and effectiveness in selecting the depth and horizontal position of the embedded wall relative to the tunnel. These findings provide valuable guidance for the practical design and implementation of protective measures in urban excavation projects.