Ground Response due to Construction of Shallow Pipe-Jacked Tunnels in Sandy Soil: Laboratory Investigation

Pipe jacking is a microtunneling construction technique that is widely used as a trenchless technology in infrastructure and can be adopted in various geological conditions. Ground responses, such as displacements and soil fracturing, will occur during pipe jacking. In order to reduce disturbance to the surrounding soils, factors resulting in ground responses should be evaluated prior to construction. This article presents a series of laboratory tests to investigate the ground response that is due to shallow buried pipe jacking in sandy soil. Single and parallel pipe-jacked tunnel tests were conducted to simulate different construction conditions. Vertical soil displacements and corresponding jacking forces for various cases were observed and discussed. The results indicate that factors such as the existing pipes, the thickness of overburden soil, and the grouting slurry used have significant effects on the ground responses during pipe jacking. Slurry with a proper ratio is proposed for pipe jacking construction. Soil fracturing and grouting overflow can easily occur in the shallow buried tunnels when slurry injection points are opened at the upper side of the pipe. The jacking parameters should also be controlled within a range to reduce the risk of soil fracture and grouting overflow.