Ground Response to Horizontal Spoil Discharge Jet Grouting with Impacts on the Existing Tunnels

AbstractThis study presents an application of horizontal spoil discharge jet-grouting (SDJG) columns in soil improvement between the new undercrossing tunnels and the existing tunnels in Changsha, China. To investigate the impact of SDJG construction on the ground and the existing tunnels, the ground pore-water pressure, induced hoop strain, vertical displacement, and rotation of the existing tunnel were monitored. The results indicate that SDJG columns were generally well constructed with an average unconfined compressive strength exceeding 3.50 MPa. Because of the quick discharge of spoils, there was only a slight increase in ground pressure and deformation of existing tunnels during the installation of SDJG columns. The influential range of the SDJG method is much smaller than that caused by pile driving and horizontal twin-jet grouting, and it is similar to that caused by wet deep mixing. SDJG is recommended to improve the area in which adjacent sensitive structures and infrastructures exist because of its reliable effect and minor disturbance to the surrounding ground.