In the supporting drainage reconstruction project of Chongshan road reconstruction project in Shenyang, the pipe diameter DN2 100㎜ is 1650 m, and the pipe diameter DN1550m is 390 m ... The jacking force and jacking distance of the FRP pipe jacking project in Chongshan road are the first in China. This paper summarizes the application background, pipe characteristics, design technology, production technology and product quality control of FRP pipe jacking.
I. Application background
There are two overpasses on Chongshan Road. During the implementation of drainage reconstruction project of road reconstruction project, due to many underground obstacles under the overpass, such as underground pipe network and structures, the height of overpass approach, it is impossible to use the construction method of laying pipe culvert on the ground, and only the construction scheme of trenchless underground jacking can be adopted. At the same time, considering that the jacking process cannot affect the pier foundation, the minimum safe distance between the pipeline and the pier should be ensured. Only the glass fiber reinforced plastic pipe with sand has smooth inner wall and high circulation capacity, and the diameter of the pipe conveying the same flow is much smaller than other pipes, which can better ensure that the pier foundation is not affected. After repeated argumentation by experts from the aspects of technology, economy, construction, etc., it is finally decided to use glass fiber reinforced plastic sand pipe as the pipe jacking. On the premise of ensuring the flow, the pipe diameter is reduced to DN2 100㎜ and DN 1550.
Second, the pipeline characteristics
The pipe jacking construction of drainage pipes DN2 100㎜ and DN 1550㎜ of Chongshan Road Reconstruction Project in Shenyang started on June 15, 2002 and was completed on August 3 1 day, with an average progress of more than 6 meters per pit every day, which showed many advantages in the construction process, as follows:
1, fast construction progress: the daily progress of a single pit is not less than 6 meters, while the daily progress of a single pit for concrete pipes with the same flow is less than 1 meter, and that for steel pipes is 2 meters.
2, small jacking force: smooth appearance, small jacking force. At present, the maximum jacking force is dn 2 100㎜800t, dn 1550㎜500t. However, the appearance of concrete pipe is rough, the jacking force is large, the jacking is difficult and the jacking machinery is demanding.
3. High flow rate: the inner wall of glass fiber reinforced plastic sand pipe is very smooth, with roughness n=0.0084 and flow coefficient Cp= 150, which is obviously higher than that of steel pipe, cast iron pipe and concrete pipe Cp= 100. Therefore, under the same pressure, the diameter of glass fiber reinforced plastic sand pipe can be reduced by one step and the cost can be reduced.
4. Because the pipe diameter is reduced (from DN2400㎜DN2 100) and the pipe wall is thin (concrete pipe is 200㎜, while glass fiber reinforced plastic sand pipe is only 55), the difficulties caused by crossing with other pipes in the process of pipe jacking are avoided.
5. Rectification is simple: due to its light weight, the pipe joints are connected by steel sleeves, and then sealed with hand-pasted glass fiber reinforced plastic after construction, which makes it particularly easy to rectify the deviation during jacking.
6. Convenient connection: Because the connection of pipes in each working pit or receiving pit is not an integer length, if concrete pipes are used, they cannot be cut to any length for butt joint; if steel pipes are used, it takes 24 hours to weld two welds; if glass fiber reinforced plastic pipes are used, they can be cut to any length and connected within 2~3 hours.
7. Jacking with soil: Because of smooth appearance and small jacking force, even with soil, the jacking force will not be too great. In actual construction, because the soil is mostly sandy soil, considering the influence on the pier, the method of jacking with soil is generally adopted, but if concrete pipes are used, they will bow their heads and cannot pass.
8. There is basically no cohesive force between the pipe surface and the soil, and the pipe will not die when jacking. However, there is a great cohesive force between the surface of concrete pipe and soil, and it is easy to die when pressed in.
9, the use of machines and tools is simple, without large equipment. Light weight and low transportation and hoisting costs. In this project, a small truck crane is used to unload the pipe, a 5t electric hoist is used to lower the pipe, and two 400t hydraulic jacks are used to jack it up, which greatly saves the cost of machines and tools. The weight of concrete pipe is about 10~ 15 times that of glass fiber reinforced plastic sand pipe, and the transportation and hoisting costs are high.
10, glass fiber reinforced plastic sand pipe has excellent corrosion resistance, long service life, almost no warranty and maintenance, ensuring a service life of 50 years. However, the corrosion of steel bars in concrete pipes seriously affects the service life.
Glass fiber reinforced plastic pipe jacking with sand shows many advantages in the use process, especially in the complex section under the urban overpass, which solves the technical difficulties that traditional pipes can not solve, and is worth summing up experience and popularizing.
Third, design technology.
1, determination of design parameters
According to the specific application conditions of the FRP pipe jacking project in Chongshan Road, Shenyang, the design parameters such as pipe diameter, pipe stiffness grade, soil parameters and design load (including internal pressure, negative pressure, vertical static pressure load on the pipe top, live load of ground vehicles and soil piling load) are determined, which provides theoretical calculation basis for the structural calculation of FRP pipe jacking with sand.
2. Structural calculation of FRP pipe jacking with sand.
According to the selected design conditions and parameters, the structure calculation and computer nonlinear finite element numerical calculation of glass fiber reinforced thermosetting resin sand pressure pipe (JC/T838- 1998) and pipe jacking construction technology are carried out. The calculation of pipeline structure includes the calculation, analysis and check of jacking strength, stiffness, bending deformation, bending strength, stability analysis and seismic strength analysis. All the performance indexes designed in this project meet the requirements of the national standard of FRP sand pipe and the special requirements of FRP sand pipe jacking in this project. See the annex for the main technical parameters and inspection report.
Fourth, the production process
The design scheme and production process of the integration of pure FRP and FRP sand inclusion are adopted.
1, process route
Using the production process of 12m-long fixed-length winding glass fiber reinforced plastic sand-filled pipe, four 3m-long glass fiber reinforced plastic sand-filled pipe jacking pipes were produced on each die at one time. According to the design number of floors, sand is mixed intermittently, and 300~800mm pure glass fiber reinforced plastic parts at both ends of each pipe jacking are realized by local reinforcement of glass fiber fabric. Each pipe jacking room is polished and cut with special equipment, and can be demoulded when it reaches the specified shape and size. The production efficiency can fully meet the requirements of the specified project schedule.
2. Production equipment
According to the characteristics and specific requirements of DN3000mm FRP pipe jacking with sand, the winding equipment was slightly modified and necessary polishing and finishing devices were added to produce FRP pipe jacking with sand that meets the specified requirements.
3. Production technology
1) Determine and approve the design and production plan;
2) manufacturing an inner lining;
3) the glass fibers are wound and cross-wound in the internal structure layer;
4) Intermittent interlayer with special interlayer cloth (the interlayer cloth is continuous at the place of pure FRP, but the interlayer is stopped);
5) After each layer is mixed with sand, make pure glass fiber reinforced plastic parts in time;
6) the glass fiber is wound and cross wound around the external structural layer;
7) Trimming and cutting to achieve uniform shape and specified size;
8) demoulding, after inspection, the steel thimble leaves the factory.
Verb (abbreviation of verb) quality management
1, enterprise standard for glass fiber reinforced plastic pipe jacking with sand.
At present, there is no "pipe jacking" variety in the industry standard of glass fiber reinforced plastic sand pipe. In the data of "initial flexibility radial deformation rate", only the pipe stiffness grade below 10000N/m2 is specified. In order to meet the needs of the market and users, the enterprise standard of pipe jacking products is formulated with reference to industry standards and product characteristics as the basis for organizing production and quality inspection. Attached is the enterprise standard of glass fiber reinforced plastic pipe jacking with sand.
2, quality control points
2. 1, raw materials
It is very important to select high-quality raw materials according to the specified requirements, especially the manufacturability of raw materials.
2.2 strictly implement the process
After each layer of intermittent sand inclusion, fill pure glass fiber reinforced plastic with glass fiber fabric in time to form a good connection state with the sand layer, ensure the transmission and extension of axial pressure at the end face, and make the whole pipeline as undamaged as possible; Otherwise, if pure glass fiber reinforced plastic is replenished after sand inclusion for many times, the interface between pure glass fiber reinforced plastic and sand layer will inevitably appear, resulting in extrusion and shear, which will lead to the damage of the pipeline at the junction of pure glass fiber reinforced plastic and sand layer.
2.3, external surface flatness
We must attach great importance to and ensure the smoothness of the outer surface of the pipe jacking. Only when the outer surface reaches a certain smoothness can the friction resistance and jacking force be reduced and the pipeline can be successfully jacked without damage.
2.4. Verticality of end face
It is necessary to meet the verticality requirements of the end face of the pipe and make the error as small as possible. Only in this way can the jacking direction be ensured and the jacking force will not increase too fast.
2.5 The length of the pure FRP part must be guaranteed or slightly increased, and its curing degree should meet the specified requirements (the curing degree is equally important for the sand inclusion section) to meet the requirements of the actual construction jacking force.
2.6 For the glass fiber reinforced plastic pipe jacking project with sand in Chongshan Road, we have compiled quality planning documents such as Size Table of Top Pipe Joints, Quality Inspection and Acceptance Standard for Exterior Dimensions of Pipe Jacking Products, Operation and Acceptance Rules for Inner Wall Sealing of Top Pipe Joints, and Technical Design Book of Pipe Jacking, so as to guide production and construction and further ensure product quality and construction quality.
3. Connection mode
The embedded steel collar is used to connect and locate the pipe section, and the glass fiber reinforced plastic (FRP) port is sealed after the pipe jacking is in place. The two ends of the pipe jacking are turned out of the platform, so that the outer diameter of the steel collar is consistent with the outer diameter of the pipe jacking itself after the steel collar is sleeved on the pipe end. The outer collar is a highly elastic rubber ring with the same thickness as the inner plug. The two pipes can stop water after docking, and the steel collar plays a positioning role, which increases the ability to resist uneven settlement.
Concluding remarks
With the strong support from all sides, the company successfully completed the supply project of glass fiber reinforced plastic pipe jacking with sand in the road reconstruction project of Chongshan Road in Shenyang. Through the implementation of this project, the company has accumulated valuable experience in the production of glass fiber reinforced plastic pipe jacking with sand: in the future, when producing similar pipe jacking tasks, alkali-free glass fiber cloth with enhanced size should be prepared as soon as possible to repair the pure glass fiber reinforced plastic parts at both ends of the pipe to further strengthen the axial jacking force that the pipe end can bear; Through the technical transformation of equipment, the degree of production automation is further improved, the outer diameter of pipe jacking is ensured to be consistent, and the jacking force is reduced. We have reason to believe that through our continuous efforts, Liaoning Water Industry FRP Pipeline Co., Ltd. will do better in similar projects in the future.
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