Patent ID: 7927694

Claim:
A combination including: a waterproofing sheet in combination with and affixed to a layer of concrete or rock, wherein the waterproofing sheet which consists essentially of three layers: a first layer of plastic material that provides the whole with mechanical strength, a second intermediate layer of foam forming a union between the first and a third layer, and the third layer of impermeable plastic material, wherein the first, second and third layers are coextensive to each other, wherein the first layer is made of an elastomeric polyolefin of high strength, wherein the second layer is made of closed-cell, physically or chemically cross-linked polyethylene foam, wherein the third layer is made of polyolefin with high tear resistance, in that the tensile strength of the sheet is between 24 Mpa and 39 Mpa and the elongation at rupture of the sheet lies between 550% and 900%, wherein the waterproofing sheet is suitable for use in tunnels, channels, and underground construction, and wherein the third layer of polyolefin includes a plurality of channels provided on a surface of the third layer that faces the layer of concrete or rock in a sandwich layout and the plurality of channels are oriented in the third layer to facilitate the flow of liquid and prevent accumulation of liquid between the waterproofing sheet and the layer of concrete or rock.