ABSTRACT
Expansive soils in the geological strata around tunnels can threaten their stability severely. The high shrink-swell ability of these soils significantly impacts the tunnel’s long-term operation. The location of the expansive layer plays a crucial role in adjudicating the consequent response of the tunnel to additional swelling pressure. This study evaluates time-dependent response to stresses due to expansive soil’s specific location around the tunnel through model tests. The lab-prepared expansive soil sample was placed at the crown, shoulder, wall, and invert sections of the reduced-scale tunnel model and saturated to evaluate the tunnel response to swelling pressure in the context of time. The results projected a significant rise in pressure at different tunnel sections with time, implying long-term stability problems associated with the location of expansive layers in geological repositories. The movement of the surrounding ground was further evaluated through particle image velocimetry (PIV). The results suggest a strong relationship between expansive soil location, tunnel stability, and alterations in surrounding ground movements. Furthermore, the tunnel’s ground displacements decreased with the expansive soil’s depth. Therefore, the location of expansive soil around the tunnel can seriously impact the sustainability of the tunnel by influencing a specific section of the tunnel in direct contact with expansive strata and can cause the surrounding ground to deteriorate simultaneously.
