Definition - What does Soft-Ground Tunneling mean?
Soft ground tunneling describes the additional measures needed when Microtunneling through soil conditions that are vulnerable to collapse. Microtunnel Boring Machines (MTBM) are equipped with a supply of liquid slurry to create an internal tunnel pressure sufficient to keep the tunnel open and prevent the ingress of ground water. This process ensures tunneling can happen effectively in soft grounds.
Trenchlesspedia explains Soft-Ground Tunneling
Soft ground can cause problems in microtunneling operations in two specific ways. If no remedial action is take, the ground can collapse on the tunnel during installation thus causing delays and safety concerns. The use of slurry to provide an active pressure as the MTBM progresses along the planned route should keep the tunnel intact. However, if too much pressure is applied, the slurry pressure may cause the tunnel to burst open, especially if the installation is in shallow ground. Soft ground tunneling requires good knowledge of ground conditions, accurately engineered slurry supply and constant monitoring of the project.