Construction Technology Of Liucheng Tunnel Under Expansive Soil And Water Conditions

Expansive soil can do great harm to tunnel constructions because of its distinct character of expanding when exposed to water and shrinking when lost water. There are many crannies in expansive soil and rocks, and they will break down and get lower shear strength because of exposure to water, and finally induce lower stability of tunnel soil and rocks.A construction project of tunnel supporting under expansive soil and water conditions is introduced in this thesis, taking Liucheng tunnel as an example. Liucheng tunnel is a shallow tunnel, with the length of 244 meters, along the railway from Beiing to Jiulong city. Less recognition of expansive soil and rocks has induced several rock and soil falls during the construction of the tunnel. The tunnel soil and rocks, with good hydroscopicity, are full of groundwater after several days' rainstorm. As the result, effective anchoring can not be provided to the intenerated soil and rocks by the rock bolts according to the original design plan. So rock and soil falls occurred just following the excavating of the tunnel portal.Basing on the engineering geological investigation and dilatability tests of the soil, the conclusions are drawn out that the railway can to through the area with a tunnel rather than cut slopes because cut slopes will cost more than a tunnel, and that the level of the wall rocks should be III but not IV. Some proposals are brought out about disposal of soil and rock falls, reinforcing of tunnel portal, supporting of wall rocks, and monitoring and measurement.The supporting methods and other disposals are tested to be appropriate in the actual constructions. The disposal of surface water and groundwater has decreased the expansion and intenerating of the expansive soil. The advance pipe roofing and grouting have taken affection of water stopping and increased the overarching capability of the soil. The supporting measures are brought forward aiming at water stopping in this thesis, which can be a good reference to the construction of tunnels locating in expansive soil and rock areas.