Waterproofing of a bored tunnel by employing an innovation composite membrane

An innovative method for the waterproofing of tunnels was employed for the 8 m diameter bored tunnel in Liuhe construction section of Dahuofang, a water transfer facility for the recently completed Dahuofang hydraulic tunnel from Huanren City to Benxi City in Northeast of China. Successful waterproofing was achieved by a composite membrane system, consisting of a minimum 10 mm thick HW sheet applied membrane, which is between two layers of sprayed concrete according to the hydrological and geological conditions of tunnel. The membrane provided bonding to the rock support sprayed concrete substrate, as well as to the inner layer of sprayed concrete which was applied onto the waterproof membrane after the initial curing. The waterproof membrane was applied to the full tunnel profile including the invert, to provide a single shell undrained solution. The double sided bonding which the system provides ensured no migration of water along the membrane-concrete interfaces. Hence, a continuous waterproof single-shell sprayed concrete structure was achieved. It was indicated in in-situ application that the waterproof and drainage system of composite liner structure effectively solve the problem of water seepage and ensure safety of underground structure. Mathematical models of waterproof plate supplied the basis for scheme selection and parameter design.