Due to space constraints and congestion, in increasing amount of infrastructure is being constructed below ground level, in many cases requiring dewatering to be carried out in order to allow work to proceed safely.
Provided there is clear access between a tunnel or shaft and ground level, dewatering will often require the use of either vertical or inclined wells, drilled from ground level using normal dewatering techniques. When surface access is not possible, or there are obstructions to the drilling angle, dewatering can be carried out using small-diameter wells, drilled radially from the tunnel or shaft itself. Due to headroom restrictions, specialist in-tunnel drilling plants may be required. In some instances, where significant groundwater pressures are encountered, drilling must be carried out using stuffing-boxes with lost-bits.
For more in-depth information on tunnel dewatering, visit our Projects page for details and pictures of our work on the prestigious Tyne Tunnel 2.