Dewatering for Tunnels and Shafts | Groundwater Engineering

Dewatering for Tunnels and Shafts

Tunnelling and shaft construction often present special dewatering problems. Dewatering applications for tunnelling include:

• Dewatering and depressurisation for construction of shafts to launch or receive Tunnel Boring Machines (TBMs).
• Dewatering and depressurisation for construction of cross passages, tunnel enlargement, adits or other connections where the ground around a tunnel or shaft may be exposed temporarily.
• Dewatering for recovery of damaged or flooded TBMs.
• Dewatering to lower groundwater levels to below invert to allow open face tunnelling methods to be used in otherwise unstable ground. This is sometimes used when a TBM designed for relatively stable soils present over most of the tunnel length has to traverse a short section of alluvial or glacial soils which may be present in a buried channel or other geological feature.
• Dewatering to control groundwater velocities to allow use of ground treatment methods (such as artificial ground freezing or grouting) in problematic conditions.

Dewatering for tunnels and shafts can sometimes be achieved with vertical or inclined wells drilled from ground surface, provided that access is available above the tunnel, and that there are no intervening service pipes between ground level and the tunnel. However, in many cases that is not possible and dewatering is carried out using arrays small diameter wells drilled radially out from the tunnel or shaft.

Groundwater Engineering provides complete dewatering solutions:

• Design of dewatering systems
• Well drilling and installation
• Pumping tests
• Equipment sales and rental
• Monitoring systems
• On-site operation and maintenance