Abstract:A water diversion project passes through the bridge span of the Beijing-Guangzhou Railway. The excavated foundation pit and the cast-in-situ frame culvert is used as the protection channel of the raw water pipeline to pass through the railway. Due to the limitation of the clearance under the railway bridge, the foundation pit cannot be constructed by the large machinery and equipment. The underpass of the culvert is located on the existing river bed, which is often submerged due to the impact of the opening of the upstream reservoir and the discharge of floodwater. The geology of the riverbed is mainly coarse sand, gravel and other strong permeable layers, and the groundwater is connected with the existing river channel. Affected by the space constraints under the railway bridge, the geology of the strong permeable sand layer and the flood discharge of the upstream reservoir, the foundation pit water-stopping high-pressure jet grouting pile has poor piling quality in the dynamic water environment, and the water-stopping effect is not good. The water level in the foundation pit is connected with the groundwater outside the foundation pit. Due to the fact that groundwater extraction is not allowed for operations near railway bridges, the cast-in-place frame does not meet the conditions for dry ground operations. In order to reduce the impact on the existing railway bridge, near the railway, without extracting groundwater or using large-scale mechanical equipment, a new process technology of partial prefabrication and partial cast-in-place is used for the cast-in-place frame. The displacement and settlement deformation of the existing railway pier are monitored in the construction period. The horizontal displacement of bridge piers is affected by -1.01 to 2.30 mm, and the vertical displacement is affected by -0.12 to 1.04 mm. The practice proves that the new process has little impact on the construction of the adjacent railway bridge.
