As a newly developed pipe in the field of water supply and drainage, FRP jacking pipe can help finish installing the underground pipeline without digging the ground. It can directly runs across road, railway, rivers, surface and underground buildings. Owing to its great corrosion resistance, light weight, smooth inner wall, large flow, good adaptability to geological conditions and other features, the product has become the first choice in the pipe network reconstruction in large and medium-sized cities.

I. Design technology

1. Determination of design parameter

According to the specific service conditions of the FRP sand pipe-jacking of the pipe-jacking engineering, determine the pipe diameter and grade of pipe stiffness, soil parameter, design load (including internal pressure, negative pressure, pipe top vertical static earth pressure load, ground vehicle live load, pile-soil load) and other design parameters, which will provide theoretical basis for calculating the structure of the FRP sand pipe jacking.

2.Calculation of the structure of FRP sand pipe-jacking

In accordance with the selected design conditions and the design parameters as well as our national standard-Glass Fiber Reinforced Plastic Pipe Jacking (GB/T21492-2008), Pipe Jacking Technology, and the computer nonlinear finite element numerical simulation, the calculation on the structure of the FRP sand pipe jacking has been carried out. The calculation of the pipe structure includes the strength of jacking force, stiffness, flexural deflection, bending strength, stability analysis, earthquake intensity analysis and other calculation, analysis and verification.

II. Production technology

The design scheme and production technology of the integrated composite strengthening of pure FRP and the FRP sand is adopted.

1、Process route

Use the production technology for the 12m fixed-length-winding FRP sand pipe to turn out 4 sections of 3 meters’ FRP pipe-jacking on each mould on a one-time basis. Apply sand discontinuously as per the designed number of floor. The local reinforcement by fiberglass cloth shall be adopted for the pure FRP at 300-800mm at both ends of the top of each section. The pipe-jacking of each section is being ground and cut via special device and will be demoulded on a one-off basis after trimmed to the required shape and dimensions. The production efficiency can definitely keep up with the project schedule.

2、Production equipment

Our company’s two computer-controlled automatic production lines for the production of DN3000mm FRP sand pipes carries out slight transformation on the winding device by targeting at the features and specific requirements of FRP sand pipe-jacking and adds necessary cutting and trimming device, which enable the production of FRP sand pipe-jacking up to the requirements.

3、Production technology

a. Confirm and approve the design and production plan;

b. Making of lining;  

c. Wind the inner structural layer with fiberglass in a circular and crossed manner;

d. Discontinuously apply sand with special emery cloth (The emery cloth is continuous at the pure FRP but with stoppage of sand.)

e. The part for pure FRP shall be made without delay after applying sand at each layer.

f. The fiberglass shall wind the outer structural layer in a circular and crossed way.  

g. The trimming and cutting shall come up to the unified shape and the required dimensions.

h. Apply the steel shrink-ring and ship the products out of factory after demoulding.

III. Quality control

1、Standard of FRP sand pipe-jacking

Making shall be conducted in strict compliance with the national standard.

2 Main points of quality control

2.1 Raw material

It is a must to choose excellent raw materials as per requirements, especially the manufacturability of raw materials, which is especially important in making pipe-jacking.

2.2Carry out process strictly

After applying sand discontinuously at each layer, it is necessary to timely level the pure FRP via fiberglass cloth so as to form desired connection with the sand layer, which will ensure the transmission and extension of the end-face axial pressure and enable the pipe to be stressed entirely and free from damage. Otherwise, if the pure FRP is being repaired after applied sand for several times, the pure FRP and the sand layer will inevitably have an interface as well as extrusion and cutting, thus giving rise to damage between the junction of the pipe and the pure FRP and the sand layer.

2.3 Smoothness of external surface

It is a must to pay great attention to and ensure the smoothness of the external surface of the pipe-jacking. Only when the external surface has come up to a certain smoothness can it reduce the friction and jacking force and enable the pipe to enter smoothly and without damage.

2.4 End verticality

It is a must to meet the end verticality and reduce the error as much as possible. Only in this way can the jacking direction remain correct and keep the jacking force from increasing too fast.

2.5The length of the part made of pure FRP must be ensured or slightly increased and its curing degree must meet related requirements (The curing degree is equally important for the sand layer.) so as to meet the requirements of the jacking force for construction.

3、Mode of connection：

The embedded steel shrink-ring is being applied for connection and position between pipe sections. When jacked in, it is necessary to combine the FRP resin mouth for sealing. The two pipes can seal water after being connected. A platform at both ends of the pipe-jacking will be formed to enable the external diameter of the steel shrink-ring after connected with the pipe end to be consistent with the external diameter of pipe-jacking. The steel shrink-ring can facilitate positioning and enhance the ability in resisting the differential settlement partially.