Application of pipe jacking technology in water supply and drainage pipeline construction?

Pipe jacking construction technology is a trenchless construction method, which means that the jacking equipment generates jacking force in the working pit, overcomes the friction between the pipeline and the surrounding soil, jacks the pipeline into the soil according to the design slope, and then transports the earthwork. After the first pipe is successfully jacked into the soil layer, the second pipe is jacked into the soil layer. Then let's learn about the application of pipe jacking technology in water supply and drainage pipeline construction.

With the help of the thrust between the pipeline and the main jacking oil cylinder, this technical method skillfully pushes the roadheader or tool pipe from the working pit and soil layer to the receiving pit for hoisting, and then embeds the pipeline pushed from behind between the two pits. Pipe jacking technology can effectively correct the deviation of pipeline in soil extension, and has wide applicability to trenchless laying of large and medium-sized pipelines. The advantages of this technology include no damage to the environment and buildings on the ground, no excavation of the ground, no influence on the differential deformation of pipelines, and comprehensive functions such as high efficiency, economy, safety and environmental protection. In recent years, with the dense population, busy traffic, increasing ground buildings and complicated underground pipelines in China, pipe jacking technology has been widely used in the construction of water supply and drainage pipelines, and its economic and social benefits are obvious to all.

1. Construction characteristics of pipe jacking technology in water supply and drainage pipeline construction

1. No need to dig trenches.

"Trenchless" is the primary feature of pipe jacking technology, and there is no need to dig trenches during construction, so the construction time is short and the work efficiency is high. Because of "trenchless", the whole construction process has little interference to the ground traffic and will not affect the normal passage of the ground traffic [2]. In addition, the technology directly goes through the soil layer for construction without demolishing the ground buildings, which effectively reduces the construction cost and protects the environment.

2. Zero pollution to the surrounding environment

Pipe jacking technology does not need to dig trenches and change the structure of soil layer itself, so the whole construction process will not produce ash layer, and the noise during construction will be small, which will not cause environmental pollution and will not affect the normal life of surrounding residents and users. In the engineering construction, the above-ground buildings and underground pipelines can still be used normally.

3. Distribution characteristics of construction points

The traditional trench buried underground pipeline construction technology has a linear construction surface, which occupies a large area and its social benefits are not optimistic. Pipe jacking technology has changed the defects of traditional pipeline construction technology, shortened the construction surface to point, effectively reduced the occupied area, and played a very positive role in alleviating the shortage of land resources in China.

Second, the construction technology of pipe jacking technology in water supply and drainage pipeline construction

1. Select the appropriate pipe jacking and equipment.

1. 1 Select pipe jacking.

Reinforced concrete pipe is generally used for pipe jacking, which is corrosion-resistant and convenient for construction. If there is no requirement for corrosion, steel pipes can be used. The reinforcement, stress checking and standard design of reinforced concrete pipe jacking should meet the relevant standards and should be produced by regular manufacturers with production licenses. There are two aspects to pay attention to when selecting pipe jacking: 1 Determine the length of pipe jacking. In general, long pipes are selected, because in the case of linear jacking, using long pipes can reduce the number of pipe installations, thus shortening the construction period [3]. However, if the route deviates seriously from the original route during construction, the use of long pipes will increase the length of jacking pit and the cost of excavation, backfilling, support and recovery. At this time, the short pipe should be selected to effectively control the jacking of the pipeline. 2 Selection of pipe jacking diameter. The inner diameter of pipe jacking should be determined according to the engineering nature and needs, while the outer diameter of pipe jacking should be determined according to the stress degree, reinforcement and thickness of pipe jacking. In general, the inner diameter of pipe jacking should be ≥0.5m to facilitate excavator operation.

1.2 Select jacking equipment

Common jacking equipment in water supply and drainage pipeline construction includes jacking iron, high-pressure electric oil pump and jack. Jack is the main equipment for well digging and pipe jacking, mainly including separated hydraulic jack, ultra-thin hydraulic jack, screw jack and vertical hydraulic jack. When selecting, it should be strictly calculated and determined according to the actual situation of the project. Jacking iron is a device that transmits and disperses jacking force. According to their different positions, there are three kinds of top irons: U-shaped top irons and horizontal top irons. When selecting, it is required to withstand jacking pressure without deformation and be easy to move. High-pressure electric oil pump is the equipment that provides tension power for prestressed jack, and its specification form is ZB2×2/50, where ZB is the code name of the equipment, the first two bits and the last two bits respectively represent the rated oil supply per minute and the number of oil supply circuits, and 50 is the rated oil pressure, so high-pressure electric oil pump should be selected according to the standard in construction. Among them, the tool pipes are mainly the operation cabin and the excavation cabin.

2. Work before pipe jacking construction

2. 1 site layout

The site layout before pipe jacking construction mainly includes the layout of water injection system, automatic control system, lifting equipment, pipe soil yard, material room, slag pit, slurry mixing yard and slurry mixing shed.

2.2 Reinforce the lying soil and the import and export of pipe jacking.

High-pressure jet grouting pile is used to reinforce the back soil and the inlet and outlet of pipe jacking to ensure the safety of pipe jacking machine. In order to effectively prevent the mud loss caused by the pipe jacking machine entering and leaving the reserved hole, it is necessary to install a water stop device at the working wellhead to ensure that thixotropic mud will not appear during the jacking process of the pipe jacking machine.

3. Construction requirements of pipe jacking technology

3. 1 Reasonable setting of top tube wells

Generally speaking, top tube wells refer to receiving wells and working wells, which are mainly reinforced concrete structures. If the local soil conditions are poor, in order to prevent the top tube well from collapsing and destroying the hole body, radial external bracing should be set in the well body to ensure its construction quality. According to the different structural arrangement, top tube wells can be divided into single row wells and single hole wells. Among them, single-row wells mostly adopt rectangular cross-section form, while single-hole wells have various cross-section forms such as rectangle, square and circle, among which the bearing capacity of circular cross-section is the largest and that of rectangular cross-section is the smallest. In the actual engineering construction, the types of top tube wells should be set and applied reasonably according to the specific terrain conditions. During the construction of drainage pipeline, the receiving well and the working well should be set at intervals, and the interval is the interval between inspection wells. After this setting, inspection wells can be located at the positions of receiving wells and working wells [4].

3.2 Master the construction process of pipe jacking technology

(1) Wall-penetrating construction. First of all, open the door panel of the wall, push the tool pipe out of the well, and set up the water-stopping equipment through the wall. In order to ensure the construction quality of pipe jacking through walls, the following points should be achieved:

(1) The paper-reinforced clay or low-strength cement-clay mixed soil filler is used to tightly fill and seal the through-wall pipeline to prevent the moisture in the construction environment from affecting the normal construction of the pipeline.

(2) Before the pipe jacking penetrates the wall, grouting should be carried out on the outside of the window wall pipe to make up for the insufficient strength of the wall hole.

(3) When pushing the tool pipe, move quickly and quickly to ensure that the waterproof facilities that pass through the wall have good working performance.

(4) According to their own pipe jacking construction experience, deal with possible problems in the construction process, so as to promote the smooth completion of the project.

(2) Pipe jacking out of the hole. For the treatment of pipe jacking hole, we should start with the following points:

(1) Before the pipeline is installed, carefully check the appearance of the pipeline to see if there are longitudinal cracks and damages.

(2) Ensure that the pipe wall is smooth, flat and free of bubbles and pits, and the end face should be straight.

(3) After passing the inspection, the pipe shall be hoisted to the guide rail of the working pit by crane, and lowered after being inspected by crane trial hoisting to ensure safety, so as to ensure that there are no construction personnel in the working pit during lowering.

(4) Place the first section of the pipeline on the guide rail, closely measure the elevation of the bottom of the pipeline at the front end, center and back end, and jack up the pipeline after confirming that the installation is qualified.

(3) Grouting wall protection. For a long pipe jacking construction, a layer of mortar should be injected around it to protect the pipe wall, improve the smoothness and compactness of the soil around the pipe, reduce the friction when the pipe is pushed, and prevent large-scale settlement.

(4) rectification methods. For the correction of jack, a small jack can be placed on the inner wall opposite to the pipe end deviation, and the other end can be held against the soil wall in front of the pipe with a pad, and the correction can be made after checking that the top is firm. For the rectification of overbreak, it is necessary to overbreak on the non-biased side of the pipeline and leave a hurdle on the biased side to form resistance and promote the pipeline to return to the correct position gradually.

label

The pipe jacking technology has changed the operation mode of randomly slotting and burying pipes, and realized the construction mode of burying pipes with little excavation or even no excavation, which not only meets the requirements of protecting the environment, reducing damage and saving resources, but also is one of the main construction methods of urban pipe network construction in the future.

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