Introduction of Glass Fiber Reinforced Plastic Jacking Pipe

Glass fiber reinforced plastic (GRP) pipe jacking is a newly developed pipe product in the water supply and drainage industry. It allows for underground pipeline installation without excavation. It can directly cross roads, railways, rivers, and surface and underground structures. Due to its excellent corrosion resistance, light weight, smooth interior, high flow capacity, and adaptability to geological conditions, it has become a popular pipe material for pipe network renovation in large and medium-sized cities.

I. Design Technology

1. Determination of Design Parameters

Based on the specific operating conditions of the GRP sand-filled pipe jacking project, design parameters such as pipe diameter, pipe stiffness level, soil parameters, and design loads (including internal pressure, negative pressure, vertical static earth pressure on the pipe top, ground vehicle live load, and earth pile load) are determined. This provides a theoretical basis for the structural calculation of the GRP sand-filled pipe jacking.

2. Fiberglass Sand-Filled Pipe Jacking Structural Calculation

Based on the selected design conditions and parameters, the structural calculation of the fiberglass sand-filled pipe was conducted in accordance with the Chinese building materials industry standards "Glass Fiber Wound Reinforced Thermosetting Resin Sand-Filled Pressure Pipe" (JC/T838-1998) and "Pipe Jacking Construction Technology," as well as computer nonlinear finite element numerical calculations. The pipe structural calculations included calculations, analyses, and verifications of jacking strength, stiffness, flexural deformation, bending strength, stability analysis, and seismic intensity analysis. All performance indicators of this project design meet the requirements of relevant national fiberglass sand-filled pipe standards, as well as the specific requirements for fiberglass sand-filled pipe jacking for this project. The main technical parameters and inspection report are attached.

II. Production Process

A design and production process integrating pure fiberglass and fiberglass sand-filled composite reinforcement is employed.

1. Process Route

A 12-meter fixed-length fiberglass sand-filled pipe production process is employed, with four 3-meter-long sections of fiberglass sand-filled pipe produced on each mold. Sand is intermittently added according to the designed number of layers. The 300-800mm pure FRP sections at both ends of each jacking section are locally reinforced with glass fiber fabric. Each section is ground and cut using specialized equipment, and once trimmed to the specified shape and size, it can be demolded in one go. The production efficiency fully meets the required project schedule.

2. Production Equipment

Our company has two computer-controlled automated production lines capable of producing DN3000mm FRP sand-filled pipes. By modifying the winding equipment and adding the necessary grinding and trimming equipment to meet the specific requirements of FRP sand-filled pipes, we can produce FRP sand-filled pipes that meet the specified specifications. 3. Production Process

1) Confirm and approve the design and production plan;

2) Fabricate the inner lining;

3) Circumferential and cross-wound fiberglass inner structural layer;

4) Intermittently sandblast with special sandpaper (continuous sandblasting with the cloth is applied to the pure FRP area, but with pauses);

5) Promptly fabricate the pure FRP portion after each sandblasting layer;

6) Circumferential and cross-wound fiberglass outer structural layer;

7) Trim and cut to a uniform shape and specified dimensions;

8) De-mold, and after passing inspection, install the steel collar before shipment.

III. Quality Control

1. Fiberglass Sand-Filled Pipe Jacking Enterprise Standard

Currently, the industry standard for fiberglass reinforced plastic (FRP) sand-filled pipes does not include a "jacking pipe" product. Furthermore, the "radial deformation rate of initial flexure" data only specifies pipe stiffness levels below 10.000 N/m². To meet market needs and user requirements, we are developing an enterprise standard for this product, referencing industry standards and incorporating the characteristics of pipe jacking products. This standard will serve as the basis for organizing production and quality inspection. The enterprise standard for FRP sand-filled pipe jacking is attached.

2 Key Quality Control Points

2.1 Raw Materials

Selecting raw materials according to specified requirements, especially their workability, is extremely important in pipe jacking production.

2.2 Strictly Implementing the Process

After each intermittent sand filling, promptly fill the pure FRP with fiberglass fabric to create a good connection with the sand layer. This ensures the transmission and extension of axial pressure on the end face, allowing the pipe to withstand stress as completely as possible without damage. Otherwise, if the pure FRP is filled after multiple sand fillings, an interface will inevitably form between the pure FRP and the sand layer, causing compression and shearing, leading to pipe damage at the interface between the pure FRP and the sand-filled layer.

2.3 External Surface Smoothness

The external surface smoothness of the pipe jacking must be highly valued and ensured. Only when the external surface achieves a certain degree of smoothness can frictional resistance and jacking force be reduced, allowing the pipe to be pushed smoothly without damage. 2.4 End Surface Verticality

Meeting pipe end surface verticality requirements and minimizing deviations is the only way to ensure the proper jacking direction and prevent excessive increases in jacking force.

2.5 The length of the pure FRP section should be maintained or slightly increased, and its degree of solidification should meet the specified requirements (solidification is also important for the sand-included section) to meet the actual jacking force requirements during construction.

3. Connection Method:

Embedded steel collars are used to connect and position the pipe sections. During jacking, the FRP resin seal is combined with the collar to provide a watertight seal after the two pipes are joined. A platform is machined at each end of the jacking pipe to ensure that the outer diameter of the steel collar is consistent with the outer diameter of the jacking pipe itself after the collar is placed on the pipe end. The collars provide positioning and provide some resistance to uneven settlement.