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Construction Technology Of Trenchless Buried Pipe

December 27, 2021

1. Technical Content

Trenchless buried pipe construction technology is mainly used for pipe jacking method, directional drilling crossing technology and large section rectangular channel excavation technology.

(1) Pipe jacking method

Pipe jacking method is a construction method for laying pipes in soft soil or water-rich soft ground. With the continuous development and maturity of pipe jacking technology, a large number of super large diameter and super long distance pipe jacking projects have emerged. The maximum diameter of the concrete jacking pipe can reach 4000mm, and the longest distance of one jacking can reach 2080m. With the emergence of a large number of super long distance and super large diameter pipe jacking projects, corresponding new pipe jacking construction techniques have also been produced.
1) In order to maintain the earth pressure balance during the ultra-long-distance jacking, the intelligent excavation speed control construction technology of the screw machine under the conditions of constant jacking speed and multi-stage jacking is adopted; this new technology combines the parameters of the reasonable fluctuation range of the earth pressure determined by analysis, The pipe jacking machine intelligently adapts to changes in soil pressure and avoids large vibrations.
2) Aiming at the problem of excessive jacking force in the process of super large diameter and super long distance jacking, a fully automatic grouting system has been developed to intelligently distribute the grouting volume and effectively reduce the local drag.
3) Ultra-long distance, multi-curve pipe jacking automatic measurement and deviation prediction technology is by far the most suitable measurement system for ultra-long distance, curved pipe jacking. The measurement system uses multiple measuring robots on-line tracking measurement technology, combined with historical data, The direction and amplitude of the tool pipe guidance are predicted, which greatly improves the jacking efficiency and the quality of the jacking pipe.
4) The splicing technology of prestressed steel cylinder concrete pipe jacking (JPCCP for short) uses the auxiliary rail, auxiliary roof, and main roof to adjust the posture of the joint interface in all directions, which can effectively solve the high-precision interface of this new type of composite pipe. Stitching puzzles.

(2) Directional drilling and crossing

Design a traversing curve according to the entry point and the excavation point, and then use a traversing drill to drill the pilot hole according to the traversing curve, and then carry out the reaming process. Drag back to complete the laying of the pipeline. Its new technologies include:
1) MWD system that measures the position of the drill bit. The key technology of the MWD system is the sealing of the drill pipe body and the sealing of the permanent cable connection in the drill pipe under the premise of ensuring the strength of the drill pipe.
2) A brand-new rotary steering drilling system with a hole bottom motor, which effectively solves the problem of the life of the stator and the bearing, and can perform rotary drilling according to the set direction.
(3) Construction technology of large-section rectangular underground passage excavation
A rectangular tunnel boring machine is used to dig in the front, and then the prefabricated concrete structures are jacked and assembled in the soil layer to form a non-excavation construction technology for an underground passage structure.
During the jacking process of the rectangular tunnel boring machine, the pressure of the mixing chamber can be controlled by adjusting the propulsion speed of the main cylinder of the rear jack or the speed of the screw conveyor to keep it in balance with the earth pressure of the stratum where the boring machine is located to ensure the excavation The smooth jacking of the machine and the realization of low disturbance of the overlying soil; under the continuous rotation of the cutter head, the soil cut from the excavation surface enters the mixing chamber and is stirred into soft plastic disturbance soil; for natural soil that cannot be softened, It is plasticized by adding water, clay or other substances, and mixed into a mixed soil with a certain degree of plasticity and fluidity, which is discharged from the mixing chamber by the screw conveyor, and then discharged by the special conveying equipment; the tunnel boring machine digs to the specified stroke, shrinks Return to the main push cylinder, hoist and assemble the prefabricated concrete pipe sections, and then continue to push in until the entire underground passage structure is formed.
Large-section rectangular underground passage tunneling construction technology has a high degree of construction mechanization, fast excavation speed, high rectangular section utilization rate, and a trenchless construction underground passage structure has little impact on ground operation facilities, which can meet the construction needs of underground passages of various cross-sectional sizes.

2. Technical Indicators

(1) Pipe jacking method

1) Analyze the changing trend of the excavation capacity of the screw machine under different pressure and soil conditions according to the actual project, design and set up the intelligent speed control function of the screw machine suitable for the project, and deal with the influence of different soil layers on the excavation mechanism;
2) Using a grouting device with a ball valve and automatic opening and closing, combined with an intelligent control platform, each grouting hole is included in the automatic control range, remotely controlled and set grouting parameters, and reasonable allocation of grouting volume, in comparison The hard pebble soil layer should be set with more grouting amount, and the soft, water-rich soil layer should be less grouted or not compressed, so as to achieve a targeted effect;
3) Prestressed steel cylinder concrete pipe jacking construction pressure-bearing pipeline adopts a special relay ring system, and the relay ring socket should be made according to the precision requirements of the prestressed steel cylinder concrete pipe socket to ensure the sealing performance of the interface with other pipe joints. good;
4) The splicing construction of the joints of the prestressed steel cylinder concrete jacking pipe joints. When using the three-dimensional splicing system, when the distance between the sockets is close, the jacking speed should be controlled to 0.001m/s, which should be slow rather than fast.

(2) Directional drilling and crossing

1) The use of wireless transmission instruments for measurement while drilling, avoiding the distance limitation caused by wired transmission, installing signal receiving instruments at the borehole position, timely feedback of track monitoring data and grasping the dynamics of the drilling direction.
2) Set the direction parameters of the rotary drill bit and the power parameters of the hole bottom motor according to the soil conditions, and combine the remote control platform to intelligently carry out the drilling and crossing construction.

(3) Construction technology of large-section rectangular underpass tunneling

The maximum width of the underground passage is 6.9m; the maximum height of the underground passage is 4.3m.

3. Scope of Application

(1) Pipe jacking method

1) Especially suitable for construction in soil layers with cohesive soil, silty soil and sandy soil, and also suitable for construction in soil layers with pebbles, gravel and weathered residual soil.
2) It is suitable for the construction of sewage interception pipes for urban water pollution control, for the construction of liquefied gas and natural gas transmission pipes, oil pipes, and pipeline construction for power cables, broadband networks, optical fiber networks and other cable projects.
3) It is suitable for the construction of comprehensive passages under roads, railways, buildings and subway pedestrian passages in urban municipal underground projects.

(2) Directional drilling and crossing

1) The suitable stratum conditions for the directional drilling crossing method are sandy soil, silt soil, cohesive soil, pebbles and other ground conditions.
2) It can be widely used in the construction of pipelines for water supply, gas, electric power, telecommunications, natural gas, and oil without excavating the ground surface.

(3) Construction technology of large-section rectangular underpass tunneling

It can adapt to all kinds of cohesive soil, sandy soil, silty soil and quicksand strata with N value below 10; it has good waterproof performance, and the maximum depth of the soil layer is 15m; it can meet the requirements through the combination of the section modulus of the tunnel boring machine Construction requirements for underground passages of various cross-section sizes.

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