Underground excavations through complex geology and strata variations often result in having to traverse discontinuities which can be water bearing. Tunnel excavations and shafts are themselves linear in nature and can be construed as being man – made discontinuities through Rock and Soil bodies.

The excavation of tunnels is usually undertaken to run a service more easily through a range of hills or mountains rather than to take such services over the top and around with the attendant potential problems which are associated with curvature and gradient.

Such services usually take the form of road or rail transport routes or can take the form of water transfer schemes passing millions of litres of water per day from an area of wet Highland through to the delivery areas in lower or dryland areas typically found close to large industrialised conurbations.

The excavation of tunnel schemes is carried out by either drill and blast or full face tunnel boring methods. Depending on the tunnel type, it is either required to prevent the ingress of water into the tunnel – ( typical of road transport schemes) or to prevent the loss of water under pressure from within the tunnel with the attendant water jetting effects of the more friable rock sections – ( typical of water transfer and delivery schemes).

The use of continuous barriers in the form of homogeneously welded geomembrane lining systems is frequently employed to provide an element of added security to the tunnel system. The liner system which is usually made up of a double or triple layer composite of Slip Liner / Geotextile and Main Liner occupies a position between the prepared shotcreted surface on the outside and the continuous concrete liner on the inside of the tunnel profile.

The Main Liner is usually supplied in narrow width rolls to facilitate handling and installation around the tunnel profile and is often composed of a BI-colour material. This bi-coloured liner is typically light coloured with a lighter coloured “Scratch layer or Signal layer “ which is used to enhance the Quality Control of the final installed system by improving defect identification under visual examination.

The integrity of the entire tunnel system is assured by a complex system of grouting which involves consolidation / Interface and cavity grouting and this requires appropriate penetration points through the liner system.

Enviro Seal has the necessary experience to provide all the input for materials and installation service for this type of work and would be happy to respond to any serious enquiries.

Typically, Linings which fall into this category can be divided, but certainly not limited to the following groups: Water Transfer schemes / Road and Transport Tunnels / Pumped hydro Electric water schemes with shafts and conduits / Cut and Cover operations.

Enviro Seal can advise and recommend on the most cost-effective, safe and appropriate lining solutions to meet clients specific requirements. Contact Enviro Seal now for a fully professional service relating to advice on product selection, capability profiling and quotations for the supply and /or installation of lining solutions for specific projects.