There are many techniques available for both shaft and tunnel construction. Some techniques can be carried out in ‘wet’ conditions but particularly for larger shafts, open cut tunnels, cross passages and complex underground junctions it is quicker and very much safer to reduce groundwater levels so that the excavations are in stable ‘dry’ ground. WJ can provide expert advice to clients on the viability of dewatering strategies in any particular geological setting at an early stage in a project development.
WJ also has low headroom drill rigs and compact pumping plant essential for work in restricted tunnel environments. WJ has also developed techniques and associated plant for installing wells out of tunnels into pressurised sand horizons using a combination of preventors, drill through valves and lost bit drilling.