Introduction to the concept of pipe jacking project for fiberglass reinforced plastic sand-filled pipes

A main traffic artery with a road width of 60 m and a large traffic volume, it is one of the important transportation hubs in Shenyang City. With the development of social economy, the original sewage pipes and canals on Chongshan Road can no longer meet the sewage discharge requirements. Therefore, it was decided to build a sewage interception pipe and canal on Chongshan Road to further improve the conditions for sewage discharge in Shenyang City and improve the smoothness of sewage discharge in Shenyang City. sex. Due to the dense buildings on both sides of the road and the criss-crossing underground pipe network, it was decided to use pipe jacking construction technology. The starting point of the project is the 724 Nullah, and the end point of the project is the Chongshan West Road Pumping Station. The main sewage interception channel runs from east to west, with a total length of 6.7 km, running through the Beiling Street Viaduct and the Huanghe Street Overpass. The designed cross-section of the sewage main channel is a 2.4 m It is 2151 m, of which the length of the fiberglass reinforced plastic sand-filled pipe with a jacking diameter of 2100 mm is 1771m, and the length of the fiberglass reinforced customized perforated sandblasted oxidized silver audio shell with a jacking diameter of 1550 mm is 380 m. The total investment in the project is more than 38 million yuan. ​​

2. Determination of the line position of the main sewage interception channel

There are currently two viaducts on Chongshan Road, namely the Beiling Street Viaduct and the Huanghe Street Overpass. The cross-sectional width of the two viaducts is 17 m, and the center lines of the two viaducts are located on the center line of Chongshan Road. Considering that Chongshan Road is the main traffic artery in the northern part of Shenyang City and cannot hinder traffic, after detailed demonstration and research, it was determined that when passing through the two viaducts, the pipeline location should be selected on the center line of Chongshan Road, that is, at the two viaducts. Down. ​

3. Construction characteristics of fiberglass sand-filled pipes

Because the main sewage interception channel on Chongshan Road is located under the bridge area of ​​two viaducts, and the main sewage interception channel needs to cross between the pier foundations of the two viaducts, the line position is quite special, so we conducted a comprehensive comparison and selection of pipe materials for jacking pipes. The comparison and selection factors include project cost, service life and construction period, etc. The final pipe jacking material is fiberglass sand-filled pipe. 3.1 High stiffness and hardness

​​This Chongshan Road sewage interception main channel project uses two specifications of fiberglass sand-filled pipes for pipe jacking in the bridge area and abutment area. Among them, a single row of FRP sand-filled pipes with a diameter of 2100 mm is used under the bridge area, and a double row of FRP sand-filled pipes with a diameter of 1550 mm is used under the abutment area. The stiffness of the two specifications of FRP sand-filled pipes must be ≥10 kPa, and the Barcol hardness of its pipes are all ≥40. ​​​

​Due to the high rigidity and hardness of the pipe, it fully meets the requirements for pipe jacking under underground geological conditions on Chongshan Road. ​​​

3.2 Under the condition of a certain flow rate, the water cross-sectional area is small

 

The total design flow rate of the newly built Chongshan Road sewage interception canal is 5.59 m3/s. Outside the bridge areas of the two viaducts, the sewage pipes are designed as single-hole underdrains with a cross-sectional size of 2.4 m /s. In the bridge area of ​​the two viaducts, the sewage pipes are designed as 3-8kg ductile iron coated sand casting parts. Because the roughness coefficient n of fiberglass sand-filled pipes is 0.008 4 to 0.009, while that of reinforced concrete culverts is 0.013. Therefore, the water-passing section of the fiberglass sand-filled pipe can be reduced by more than 1.44 times compared with the water-passing section of the reinforced concrete culvert. In the design, under the viaduct bridge area, the sewage pipes are designed as a single row of fiberglass sand-filled pipes with a diameter of 2100 mm. The designed filling degree is 0.75, the flow rate is 2.13 m/s, and the water passing capacity is 5.93 m3/s. In the abutment area, since the clear distance between bridge frames in the abutment area is only 3 m, the design uses double rows of fiberglass sand-filled pipes with a diameter of 1550 mm. The design fullness is 0.75, the flow rate is 2.13 m/s, and the water passing capacity is is 6.45 m3/s. ​​​​

3.3 The jacking force is small and causes little disturbance to the surrounding soil.

Due to the small roughness coefficient of the fiberglass sand-filled pipe, the wall surface is smooth. Therefore, the resistance is small when jacking. Secondly, since the fiberglass sand-filled pipe can minimize the cross-sectional area and has a thin wall, the wall thickness of the 2100 mm diameter pipe in the design is 48.4 mm, and the wall thickness of the 1550 mm diameter pipe is 34.8 mm. The wall thickness is only the steel bar with the same diameter. The wall thickness of the concrete jacking pipe is 1/4 to 1/5. Therefore, under the same soil quality, the jacking force of FRP sand-filled pipe jacking is only about 1/10 of the jacking force of reinforced concrete pipes of the same diameter, and the disturbance to the soil quality around the jacked pipe is small. ​​

4. Engineering design key points and technical requirements

4.1 Key points of engineering design

The main sewage interception canal of Chongshan Road in Shenyang runs from east to west, running through the Beiling Street Viaduct and the Huanghe Street Overpass.

The Beiling Viaduct is divided into three parts: approach, abutment, and bridge area. The east-west approach is 314 m long, and the bridge area is 316 m long. The underground foundation at the abutment is 3 reinforced concrete piles with a diameter of 2 m. Between the two piles The distance is 5 m, the clear distance is 3 m, and the pile depth is 8 m; the underground foundation of the bridge area is 2 reinforced concrete piles with a diameter of 2.4 m, the distance between the two piles is 8.5 m, and the clear distance is 6.1 m. The pile depth is 10 m.

The Yellow River Overpass is divided into three parts: approach, abutment, and bridge area. The east-west approach has a total length of 297.612 m, and the bridge area is 1308.59 m. The underground foundation at the abutment is 3 reinforced concrete piles with a diameter of 2 m. Between the two piles The distance is 5 m, the clear distance is 3 m, and the pile depth is 8.5 m; the underground foundation of the bridge area is 2 reinforced concrete piles with a diameter of 2.5 m, the distance between the two piles is 9 m, and the clear distance is 6.5 m. The pile depth is 8.5 to 9 m.

Based on the actual conditions of viaducts and overpasses, the design is divided into three sections:

(1) The main sewage interception channel crosses the approach road: pipe jacking construction is adopted. The pipe is made of fiberglass custom 5kg gray cast iron sand castings. The designed pipe diameter is 2100 mm, the wall thickness is 48.4 mm, the slope is 0.7‰, and the total length of the pipe jacking is 477.54 m. . ​​

(2) The sewage pipe crosses the abutment: the distance between the pier foundations at the two bridge abutments is 5 m, and the clear distance is 3 m; the depth of the pier foundation is 8 to 8.5 m. The foundation of the bridge pier is dug piles. The design uses two fiberglass sand-filled pipes with a diameter of 1550 mm and a wall thickness of 34.8 mm. The pipe slope is 0.7‰, which cross the bridge abutment respectively. The construction method adopts the pipe jacking construction method, and the length of one jacking is The longest length is 50 m, and the total length of the jacking pipe is 380 m. ​​​​

(3) The sewage pipe crosses the bridge area: the design adopts pipe jacking construction. The pipe is made of fiberglass sand-filled pipe. The designed pipe diameter is 2100 mm, the wall thickness is 48.4 mm, the slope is 0.7‰, and the total length of the pipe jacking is 1293.46 m . ​

4.2 Technical Requirements

Due to the special construction conditions of the Shenyang Chongshan Road sewage interception main channel project in the bridge area and abutment area, all pipes in the construction section of the bridge area and abutment area are constructed with fiberglass sand-filled pipe jacking. Therefore, the technology of fiberglass sand-filled pipes is proposed. The following requirements are required. ​

4.2.1 Requirements for raw materials for the production of FRP sand-filled pipe jacking

(1) Resin material selection: Use winding unsaturated polyester resin with high mechanical strength and good water resistance produced by domestic famous brand manufacturers.

(2) Fiber material selection: Use alkali-free and twist-free glass fibers produced by domestic famous brand manufacturers to directly wrap the sand. ​​

4.2.2 Technical requirements for fiberglass sand-filled pipes

(1) Pipe stiffness: The stiffness of fiberglass sand-filled pipes with specifications of diameter 1550 mm and diameter 2100 mm must be ≥10 kPa. ​​

(2) The Barcol hardness of the pipe is ≥40. ​​​​

(3) Initial deflection value of the pipeline: When the soil covering thickness of the pipeline is greater than 3.5 m, it must be ensured that the initial deflection value detected within 24 hours after the pipeline is buried is ≤ 2%.

(4) Pipeline leakage performance: During construction operations with water, it must be ensured that there should be no leakage in the pipe body and connecting parts, and the pipe pressure level must be determined (the pipe jacking in this project is a non-pressure pipe, and the maximum pressure of the non-pressure pipe must be 1.5 times the water pressure of 0.25 MPa) for inspection. ​​​​

(5) Pipe jacking: When the pipeline encounters soft soil layers such as sand and silt, the pipeline jacking operation with soil should ensure that the offset range of the pipeline is ≤15 mm. ​​​​

(6) During the jacking process, the cushion material used on the inner wall of the FRP 11kg gray iron sand casting machinery parts pipe should ensure that the inner wall of the pipe is not damaged when soil is transported inside the pipe. ​​

(7) The service life of the pipe is ≥50 years. ​​

The connection between the short glass fiber reinforced plastic sand-filled short pipe and the pipe in the inspection well adopts a pasted connection method of flat butt joints of the same material. ​

5 Conclusion

The construction of the Chongshan Road sewage interception canal project in Shenyang lasted for 80 days and has been successfully completed. The acceptance was completed in September 2002, and the project quality reached excellent quality.