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Pipeline crossing refers to the laying method of underwater or underground pipelines when transport pipelines pass through various unsuitable environments, such as rivers, lakes or railways. The location of the pipeline crossing is mostly in a place with certain construction conditions, such as a site with smooth water flow, geological stability and a construction site.
Digging and burying
The most common method for pipelines to cross underwater is to dig trenches and bury them. This method needs to consider the geology, rock formation and river characteristics of the construction site. Various trenching equipment has been perfected day by day, and there are more and more ways of trenching. The more common methods include cofferdam trenching, trench plow trenching, grab trench trenching, blasting trench formation and hydraulic flushing.
When the pipeline crosses the difficult-to-ditch pebble riverbed and other places, it can be completed by means of a stable pipe. Pipeline construction stabilization methods include rock-fill dams, gabions, pressed concrete anchor blocks or anchor rods.
When the pipeline crosses various road locations, the laying method of casing can be adopted. The laying method of pipeline casing is to install cement casing or steel casing under the roadbed and pass the pipeline through the casing to ensure the safety of both the pipeline and the road surface.
Pipe jacking or directional drilling
When the pipeline crosses the river bed, it can be completed by pipe jacking or horizontal directional drilling. Specifically, when laying the pipeline, pipe jacking equipment is used to push the pipe over the bottom of the river bed, or a directional drilling method is used to drill a curved round hole at the bottom of the river bed to draw the pipe from it.
When the pipeline crosses the river, in order to prevent the pipeline from being floated by the flow of water, the construction is usually completed by increasing the capacity. Increasing capacity refers to covering the outer wall of the pipeline crossing the river with a concrete layer, or adding mud to the annular space of the double-walled pipeline to increase the weight. The former can save steel and the latter is less difficult to construct.