Control of Strata Deformation in Subway Interval Tunnels Crossing a High-Speed Rail Shield Tunnel at a Short Distance

The construction of subway interval tunnels at a short distance from existing buildings and engineering structures in cities is often a high-risk project. This research discusses subway interval tunnels crossing a high-speed rail shield tunnel at a short distance based on numerical simulations and on-site monitoring. The deformation patterns of the interior of tunnel, ground, and shield segments are analyzed, and the principle and function of reinforcement measures for deformation control are presented. The results indicate that constructing a temporary inverted arch using bolting and shotcreting as per the bench method has higher integral stiffness, and thus, the foot-locking effect of anchor pipes to reduce strata deformation is fully utilized. The deformation of upper high-speed railway shield tunnel segments induced by the construction of subway interval tunnels primarily occurs within a distance three times the diameter of the tunnel. Thus, this is the key area to install advanced support to control tunnel deformation. A compound advanced support approach including pipe sheds and deep-hole grouting is proposed that can exert the arching effect of deep-hole grouting and beam effect of pipe sheds to control strata deformation.