Introduction of Pipe Jacking Construction Technology Chen Tianhao (Guangxi Cangzhou City Municipal Engineering Management Office Cangzhou underground project adopts pipe jacking construction method, avoiding interference with ground transportation and various activities, without demolition and moving problems, but also conducive to environmental protection and saving investment .
Pipe jacking construction is a modern method of pipe fitting. At present, in the construction of underground pipelines for underground sewers, underground walkways, and underground works such as railways, highways, and rivers, in order to avoid damage to the scenic spots and ground buildings, and to not affect traffic, this has been widely used at home and abroad. With the popularization and specialization of pipe jacking technology, its theory is also improving day by day. Even the simplest hand-drilling pipe jacking construction needs to theoretically demonstrate whether its mining is stable. The stability includes two aspects. Content: The first is whether the soil on the excavation surface in front of the tool tube is stable; the second is whether the soil above the tool tube is stable. If it is found to be unstable, it is necessary to take effective measures to prevent it. Now, the construction of the levee culvert of Wenyu Road, Hexi Flood Control, Hezhou City, is used to introduce the construction technology.
1 Determination of technical solutions 1.1 Engineering background Cangzhou Hexi flood control embankment Wenyu Road through the embankment is located under Wenyu Road and Hexi flood control embankment according to the needs of flood control and drainage planning, cancel the existing 1.5 km 1.75m arch channel of Wenyu Road, rebuild Y2200mm The embankment culvert 1.2 engineering geological muddy soil, thickness is 3. silty soil, bearing capacity 150kPa; 4 strong weathered sandstone, bearing capacity fk=320kPa groundwater is a submersible type, occurring in the lower part of the fill, the elevation is about 11.00m (Huanghai elevation, the same below) The main sources are production, domestic water and atmospheric precipitation.
1.3 Determination of technical schemes Since the construction of the flood control embankment in Hexi has been completed for nearly 2 years, in order not to damage the flood control dike and maintain the traffic of Wenyu Road, Wenyu Road is constructed by jacking method. According to the geological conditions of the site, after comparison, it is decided to adopt the hand-piercing pipe jacking construction technology with the advantages of simple construction operation, less equipment, low construction cost and fast construction progress. 2 Pipe jacking construction technology is now the key process in the construction of the project. The technical process, work ± pit pipe jacking construction in the construction of some technical measures to introduce.
Hand-type top pipe construction process such as 2.1 work pit construction work pit is the place to place all the jacking equipment, is also the starting place of the pipe jack tool tube, and at the same time is the structure that bears the reaction force of the main top cylinder, therefore, the work pit It must be strong and the size is large enough. The original design work pit of the project uses rectangular working pits with steel plates connected to the mouth. The plane size is 5.5m<6.8m, and the depth is 15.0. According to the geological data, the geological location of the culvert is from top to bottom: The 116-storey building is 0. 8.0m away from the outer wall of the working pit. To ensure safety, the following measures are taken: 1 The flow of the Y600mm pipe is cut off from the upstream and is separated from the safe range of the working pit; A first-stage concrete retaining wall is set on the outer side of the outer side, with a depth of 1.0m. Then, when the steel sheet pile is applied to 6.0m, a silt interlayer appears, and the earth wall collapses when the earthwork is excavated. The height of the reinforced concrete retaining wall is 0.7m, and then the steel plate is re-applied. When the construction reaches 11.0m deep, the muddy soil layer appears again. When the earthwork is excavated, the collapse wall is serious. After emergency treatment, it is determined that the remaining 4.0m deep mining
2.2 Pipe jacking construction process flow Pipe jacking construction process flow See the appearance of the pipe joint on the ground before the lower pipe: including the straightness of the pipe end face, the surface finish of the pipe surface, the longitudinal crack on the end face, the non-requirement It is forbidden to use. The concrete label of the reinforced concrete pipe used for the pipe jacking shall not be lower than the design specified pipe length, pipe wall thickness, pipe diameter, etc., in accordance with the design requirements. The reinforced concrete pipe shall be secured on the guide rail before the jacking, and the right pipe mouth shall be placed on the guide layer. In the linoleum, when the steel pipe is hung in the pipe, the pipe is not allowed to stand under the hanging point in the working pit. When the pipe joint is close to the guide rail, the worker re-stationizes the pipe to the rail and then checks the pipe wall and the guide rail. Whether the surface is in close contact, if it is found to be suspended, the phenomenon of lifting, the tube joint should be rotated until the tube joint is stable until the tube joint is completely closed, and the two tube joints are connected together at the opposite ends of the tube. The interface is rigidly connected to avoid misalignment after the force is applied in the jacking process. After the completion of the pipe joint elevation and direction of the quasi-sulfur-ampere tube and the interface in the jacking process, the inner low voltage (36V) lighting wires and other pipes are extended. After the pipeline is installed, the direction and elevation of the excavation pipe joint can be controlled on the working face of the pipe front end. Depending on the excavation operation, the excavation on the work surface not only affects the jacking efficiency, but more importantly, affects the quality control.
Requirements for excavation work on the working face: According to the soil quality of the working face and the high groundwater level, the method of excavation should not disturb the foundation soil of the pipe bottom, advance in time, measure in time, excavate the earth and transport it in time according to the geological conditions. Preferably, the front end of the pipe is not equipped with a cutting edge, and the excavation is carried out according to the requirements of the specification. The excavation of the top of the pipe is not more than 2~3cm, and the curvature of the soil at the bottom of the pipe is in the range of 120*135*. The super-excavation section along the direction of the guide rail and the excavated soil hole are arranged to advance into the top iron. The single-row force transmission type is used to set the annular top iron at the reinforced concrete nozzle, and the thrust of the main top cylinder is evenly distributed to the reinforced concrete. On the end face of the pipe, at the same time, the top iron of the protection pipe end face 2 shall not be eccentric or misaligned. The requirements are as follows: a) longitudinal curvature and misalignment to prevent eccentric load; b) the centerline of the single longitudinal longitudinal iron shall be consistent with the pipe axis ; c) When the longitudinal top iron is in contact with the end face of the pipe, the longitudinal top iron center line must pass through the average radius of the pipe wall, that is, the force point should be at the midpoint of the pipe wall thickness; d) the longitudinal top iron stress point is located outside Between 1/3 and 1/4 of the height of the diameter, and the lower half to prevent the point from being too high to lower the front tube; e) the longitudinal top iron and the horizontal top iron should be perpendicularly connected; /) for uniform contact A gasket should be added between the end face of the pipe and the top iron. The gasket material is installed with the linoleum jacking procedure. The front end of the pipe has been excavated and the hole can be pushed in. a) Start the oil pump, the jack oil plug is out, start first Compress the back and press the top iron, and then push into the pipe joint. When the jack oil plug rod extends to the critical length, immediately close the oil pump, stop the jacking, return the piston rod, and then install the top iron to continue to jack up. When a tube is completed, that is, when the length of the tube section left on the guide rail is about 0.4~0.5m, the jacking should be stopped regardless of whether the jack is out of the way. At this time, the jack stroke is returned, the top iron is removed, and then the measurement is made 2.3. Pipe jacking construction situation The pipe jacking construction of this project is basically smooth. When jacking up to 15. When the pipe passes through the silt soil, it is found that the first pipe sinks about 3.0cm. For this reason, some auxiliary measures have been taken. Exit a tube and slap short pine in the soil in the muddy soil ( Y 0m), the clamp clamps the stone, so that the foundation is reinforced, and the top is pushed forward so that the pipe end has a slightly upward control state, so that the pipe is finally passed smoothly through the muddy soil layer, and the measurement is verified. The left and right deviations of the sinking are within the allowable error range. 3 Construction summary Through the practice of this project, I believe that to do a good job in the construction of the pipe jacking method, we must pay attention to the following matters: the site selection of the work pit is very important, and it must meet the pipe jacking construction. The needs of the entire line, but also try to avoid housing, underground pipelines, river ponds, overhead lines and other places.
The construction process of the work pit should be comprehensively considered, continuously optimized according to geological conditions, continuously observed during the construction process, effective measures taken in time to find problems, and drainage work in the pit to make the work pit safe and stable.
In the process of jacking, pay attention to the change of the indication value of the pressure gauge of the oil pump in time. When the pressure suddenly rises, stop the jacking immediately, check the cause of the pressure rise, prevent the accidental control of the outer extension of the jack piston, and do not exceed the critical stroke to avoid damage. equipment.
If the stoppage time is too long, the groundwater penetration will increase, the soil arch will easily collapse, and the top force will rise sharply when the roof is opened. According to different geological conditions, the top will be excavated to avoid collapse.
The jacking speed is appropriate, too fast and easy to produce deviation, too slow and easy to collapse. Practice has proved that the pipe jacking construction has played a unique advantage in the construction of rain and sewage pipelines. The performance is as follows: the excavation part is only the work pit, the earthwork is open. The amount of digging is small, and the safety has less impact on traffic and takes up less space.
In the process of pipe jacking, only the earthwork of the pipe section is dug, and the amount of excavation is less than that of the slotted open excavation.
There are few construction workers, high degree of mechanization, high work efficiency and fast construction progress.
The construction of public hazards is less, and the degree of civilized construction is higher than that of the slotted construction. The amount of land subsidence is effectively controlled, thus protecting the surrounding environment and buildings.
Avoiding demolition or repeated construction of buildings on the ground, relocation or protection measures along underground pipelines greatly reduces the amount of pre-work and saves investment.
Since the gate well drains outside the flood control embankment of this project are arranged after the flood season (October 2000), this paper only discusses from the perspective of the pipe jacking construction of the Wenyu Road through the embankment (Y2200mm pipe). , has its limitations, only.
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