Comprehensive pipe gallery develop and utility tunnel project
1. Introduction
The utility tunnel project is located in collapsible shallow loess layer, adopted the constructing technology of pipe jacking. In the process of pipe jacking, due to the "overall-carrying-soil effect", the upper soil mass will collapse and adhere to the pipe roof along the jacking direction and then pile up in a conveyor belt manner, resulting in increasing jacking resistance, larger and larger collapse range, and more and more soil mass attached to the collapse, resulting in the uplift and subsidence of the surface in the affected range.
2. Solution
During the construction, the soil at the top of pipeline area was reinforced by grouting. When jacking into the reinforced soil, the upper soil can form a larger bearing arch, making the total contact between the pipe wall and the soil become partial contacted, reducing the friction resistance of the upper soil. Applying paraffin outside the pipe wall and injecting bentonite slurry between the pipe wall and the soil can greatly reduce the jacking resistance and avoid the "overall-carrying-soil effect". Meanwhile, the jacking loads to ensure the smooth jacking increases.
3. Construction situation
The utility tunnel project generally has a north-south orientation, with a length of about 180m, a circular concrete structure and a pipe inner diameter of 3.0m. This utility tunnel contains water supply, electricity, water supply for firefighting, air conditioning supply and return water, etc.
Drive pit in construction
Drive pit
Comprehensive pipe gallery initiation ceremony
Pipe-jacking initiation
3. Achieved Accomplishment
Through the ground grouting reinforcement in the strata, wall wax, grouting and smoothing, and increase of the jacking force, finally, the underground connection of utility tunnel was successfully realized, the pipe jacking test project was successfully completed, and certain technical experience was accumulated.
Substantially completed
4. FAQ
Q1: Why did you construct such a utility tunnel?
A: In response to the company's 13th five-year development plan, we expanded the new industries of development and utilization of underground space, and collected technical experience in utility tunnel design and construction. It is of great significance to the development and utilization of urban underground space and sustainable urban development.
Q2: On what basis is the jacking force designed?
A: According to the calculation of jacking force of Specification for Construction and Acceptance of Pipe Jacking, adjustments were based on the actual situation.
Q3: How about the cost of conducting pipe jacking?
A: The cost will be depended on many issues such as geological condition, amount of construction, operation difficulties level, etc. There will always be a feasibility research in advance which will refer the estimated cost.
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