Pipe jacking construction is a construction technology that uses hydraulic power to jack steel pipes (including multi-section steel pipes) or concrete pipes from point A to point B, instead of digging trenches on the surface. Our company has formed this construction technology through many engineering practices.
Process characteristics and scope of application
1, pipe jacking under the road, the road is clear;
2, the pipe jacking under the building does not affect the use function of the building;
3. Shorten the pipeline laying cycle and significantly reduce the project cost;
4. Single equipment and simple operation;
5. The pipe joints used in this process must be qualified products produced by national designated manufacturers;
6. It is suitable for the construction of railways, highways and underground pipelines that are difficult or unsuitable for trenching.
Process principle and process flow
The exposed pipeline is changed to be powered by machinery, and the pipeline is transported from point A to point B under the ground.
Construction preparation, measuring elevation and axis, digging pipe jacking pit, laying pipe jacking guide rail, installing jacking equipment on the back, hoisting pipe joint, jacking to measure the deviation of excavation, and then digging (pipe soil) to measure the jacking until the cycle operation is completed.
Main mechanical equipment: lifting equipment, high-pressure oil pump, large-tonnage jack, back pile and back beam, guide rail and unearthed tools, theodolite and level. The function and number of machines and tools depend on the diameter, length and weight of the pushed pipe joint.
Key points of construction
1 The excavation of the pipe jacking pit shall be carried out according to the construction scheme and specific environment, and the length and width of the pit shall depend on the soil quality, the diameter and length of the pipe jacking section, mechanical equipment, pipeline laying and excavation methods. In addition to installing the back, guide rail and pipe joint of pipe jacking machine, the working pit is also conducive to excavation outside the pit and operation of operators. Generally speaking, the distance between the leading edge of the upper mouth of the working pit and the kerb is ≥2m, and each side should have a working face of 1m after placing the pipe section. The space between the pipe section and the jack should be conducive to excavation. In an environment with water, puddles and drainage facilities should be set up. The slope coefficient of the working pit wall should meet the requirements according to the soil conditions, and the pit bottom should be compacted.
2. The guide rail consists of four rails and several sleepers, which are placed on the foundation soil at the height of 1/2 sleepers under the working pit, with the sleeper spacing of 800? 1000mm, the track length is equal to the length of the working pit bottom minus the position occupied by the track piles, and the track spacing depends on the outer diameter of the top pipe joint. Generally, it is necessary to ensure that the lower skin is 20mm higher than the sleeper epithelium after the pipe joint is placed, and the jack should have the largest contact surface with the cross section of the pipe joint after installation. The rails shall be installed straight and the front end shall have a slope of 0.5- 1.0%.
3. Jacking into the back: the firmness of the back directly affects the effect of pipe jacking, so the ability of the back must meet the needs of maximum jacking. The back is composed of back piles, back beams and compacted soil behind the back piles. Post piles are generally replaced by rails and buried about 1.5m below the pit bottom. The soil behind the pile is compacted in layers. The plane of the rear pile is perpendicular to the axis of the jacking direction, and the steel back beam is placed on the front guide rail of the pile. Other types of jacking backs include masonry rubble and precast reinforced concrete blocks.
4. Install jacking equipment and pipe joints: the jacking equipment consists of a high-pressure oil pump and two 200? 500t jack, which is installed between the back beam and the pipe joint. A special steel retainer and hemp or rubber pad are arranged between the back end of the pipe joint and the jack to protect the concrete pipe end. The outer wall of the pipeline is coated with paraffin wax as a lubricant to reduce the friction resistance of jacking. The jack pushes the pipe joint into the subgrade through the force transmission column.
5. Digging, jacking, measurement and rectification: After the equipment is installed, digging and jacking can be carried out without abnormality. The excavation depends on the soil quality and the thickness of the overburden on the top of the pipeline. The soil is dense and the overlying soil is thick, which is beneficial to the formation of unloading arch and should be dug more. If the soil is loose or the thickness of the covering soil is small, it is necessary to dig less and dig more, and the diameter of the excavation should not exceed the outer diameter of the pipe joint.
The tools for digging and moving soil depend on the diameter of the pipeline, with an inner diameter of 880? A special trolley with an inner diameter of 1500mm can be directly unearthed by a two-wheeled trolley, and the vertical transportation of soil can be carried by a crane or an electric hoist.
The jacking process shall be measured at any time. After each jacking process, the elevation and left-right deviation of the pipeline should be measured once. When problems are found, they should be rectified in time, and measures such as correcting left and right deviations and raising the head should be taken. Inclined braces can be set at the front end of the pipeline, supported on the soil wall in front of the pipeline, and combined with the overbreak side, the deviation can be corrected by jacking. The joint of the first two parts is reinforced by steel expansion ring welded with steel plate as a measure to prevent deviation.
Quality requirements and safety measures
Quality requirements: the pipe jacking should be straight, and the deviation between the pipe center and the axis should not exceed 3cm.
Safety measures:
1. Coordinate with railway, highway, municipal and other relevant departments before construction, and start construction only after the construction plan is approved by relevant management departments. Especially in the construction under the railway subgrade, it is necessary to contact the railway department at any time to master the situation of passing trains, and it is strictly forbidden to dig the top when trains pass through the line;
2. During excavation and jack-up, low-voltage traveling lamp transformer shall be used for lighting in the hole, and no open flame is allowed in the hole;
3, stop digging when jacking, dowel bar on both sides are not allowed to stand, all dowel bars must be placed straight;
4. When hoisting, the personnel in the pit should take protective measures and be commanded by special personnel. 5. When the pipe jacking length is 76m, gas supply facilities should be set to prevent hypoxia.
In addition, a municipal engineering pipe jacking construction scheme is also given to you, please give me extra points! !
XX municipal road and bridge project
top
Pipes/pipes
carry out
worker
square
situation
Construction unit:
Prepared by:
Examiner:
Approver:
date month year
I. Overview of the Project:
The municipal works of Xx Road (South Section) of XX Project K4+040 ~ K4+520 are 480M long and K5+560 ~ K5+860 are 825m long. DN 1200 and DN800 three-stage reinforced concrete pipe jacking has five φ 8000 working wells and eight φ 4000 receiving wells. Earthwork of the working well and the receiving well are excavated manually, and a relay room is arranged between the working well and the receiving well. The two jacking pipes are jointly provided with 10 relay room.
(a), engineering geological characteristics
According to DN 1200 and DN800 of XX Municipal Engineering Design Institute, the engineering geological conditions are as follows:
The two jacking pipes are located in Quaternary residual loam and carbon series strongly weathered sandstone, and the rocks are cut into pieces, most of which are eroded into soil. Residual loam is poor in water content and small in water quantity. Weathered sandstone has loose structure.
(2) The number of major projects is as follows:
serial number
Engineering content
amount
1
φ 8000 working well
The fifth district
2
φ 4000 receiving well
The eighth district
three
Grade Ⅲ reinforced concrete pipe jacking DN 1200 and DN800
825 meters
four
relay bungalow
10
five
Drag reduction along the line, injecting bentonite slurry into the orifice to stop water.
156 ton
six
Inject mud into the back wall of the working well.
30 tons
Second, the construction layout and temporary facilities layout
(1) Layout of construction access roads and on-site transportation roads
According to the field investigation, there is no road leading to the construction site inside and outside the site, so construction access roads must be built for transportation inside and outside the site. The road structure is as follows: After the subgrade is leveled, the pavement adopts a 750px thick 6% cement macadam stabilized layer, and the access road is 7 meters wide. During the construction period, do a good job in the maintenance and cleaning of the construction access road, and the construction access road will meet the safety and civilized model site standard of XX City Construction Committee.
(2) Temporary arrangement of offices and living rooms.
Our company plans to use the combined room to arrange temporary office and living facilities near the construction area. According to the field investigation, the production base is located near the construction site and used for mechanical parking, material transfer and semi-finished product processing. Civilized construction guardrails shall be fenced according to the standard of building enclosure in XX city.
Our company will remove trees, turf, sundries, etc. According to the red line of land requisition, the surface layer shall be drained of water and silt in ditches and pits, and the surface layer shall be cleared by machinery to level the construction site, and then the soil shall be filled and compacted to prepare for the early construction.
(3) Water supply and power supply scheme
According to the specific situation of the site, our company plans to set up a generator room at the construction site, using 1 120KW generator to generate electricity, and tn-s power supply is used for the construction transmission line; The construction water is dug in the field and pumped by centrifugal pump.
(4), yard, warehouse, computer room and workshop layout
The material warehouse and generator room are set in temporary buildings, the on-site warehouse and generator room adopt brick wall structure, and various material yards and processing plants are flexibly arranged in the construction site. Yard, warehouse, etc. are arranged to meet the safety and civilized model site standard of XX City Construction Committee.
(5), concrete production and use
1, concrete supply and transportation equipment layout
In order to ensure the quality of concrete, this project adopts commercial concrete, so there is no mixing station on site.
Third, the main engineering construction methods
(1) Construction of working wells and receiving wells
There are 13 open caissons in this project, including 5 φ8000 pipe jacking working wells; 8 φ4000 pipe jacking receiving wells. They were all built by hand digging wells.
1, the construction method of manual well digging is as follows:
1. 1 In the construction of manual dig-hole well, the hoist is used to excavate through the crane hanging hole on the bracket, and the manual bucket truck is transported to the slag disposal point at the bottom of the pit, and the excavator and truck regularly excavate and transport it out. After the shaft lining reinforcement is made and shaped in the processing plant, it is transported to the site by car for use, and the shaft lining concrete is poured from top to bottom by chute.
1.2 The main equipment required for construction includes shovels, pickaxes, buckets, car cranes, small gourds, pulleys, pneumatic drills, pneumatic pickaxes, templates, supports, submersible pumps, blowers and working lights.
1.3 labor organization and arrangement: every three people work in shifts, and the daily excavation depth of soil section 1.0m, strongly permeable sand section/0.5m and rock section1m. Considering the influence of groundwater, after the foundation pit dewatering, artificial well drilling is arranged to start construction.
1.4 construction technology of manual well digging
See figure 1.4- 1 for the process flow of well digging.
Figure 1.4- 1 process flow chart of well digging.
1.5 Construction method and technical measures of manual well digging
1.5. 1 well digging construction method
Conventional manual excavation, small winch lifting and transportation, sectional excavation, and pouring retaining wall concrete to form holes; The retaining wall concrete adopts commercial concrete.
When digging a hole in the strongly permeable sand layer, the principle of short footage and strong support is followed, and the method of grouting is used to strengthen the stratum and steel insert plate in the construction.
When digging a hole in the rock, artificial pneumatic drill is used to drill the hole, and shallow hole is used to control the blasting construction.
1.5.2 technical measures for well digging construction
(1) Positioning and locking
Measure the center position of the well, set out crosshairs around the well, excavate the first borehole, support the first formwork for retaining wall, and pour retaining wall concrete. The first section of concrete is 500px higher than the ground, which is convenient for water retaining and positioning. The center line of the hole ring coincides with the drilling axis, and the deviation from the axis is not more than 50px.
(2) Excavation and support
Divided into general strata and special conditions, described as follows:
1) general stratum excavation and support
Manual well digging adopts the construction method of subsection excavation and subsection support. According to the design requirements, each section is1.0m.
The retaining wall is made of C30 concrete, the thickness of the working well is 35~45cm, and the thickness of the receiving well is 20~750px. The structural form of the retaining wall is set as internal splayed lap, and the lap length is 2 10 mm ... The retaining wall formwork adopts tool-type steel formwork, with eight pieces in total. The formwork is connected by bolts and U-shaped fixtures, and there are two semicircular steel ring top frames on the formwork. Before pouring retaining wall concrete, use well point to correct the position of formwork. The concrete of the breast wall is transported by the commercial concrete to the pouring location of the orifice, vertically transported by the orifice winch to the pouring location, manually put into the mould, and tamped by the internal vibrator.
Drill holes manually, load the spoil into bucket, lift it to the ground with a small winch, and then transport it to the temporary spoil ground with a trolley.
2) Digging holes under special conditions
1 technical measures for pore-forming through strongly permeable sand layer
In order to ensure the safety of manual well digging, before manual well digging, dewatering construction should be carried out first, and the groundwater level should be reduced to 0.5~ 1m below the digging bottom, and a 600×600 collecting well should be set before manual well digging.
When it is difficult to form a hole by manually digging a well through a strongly permeable sand layer, the method of reducing the height of each wall of the well hole (generally between 0.3 m and 0.5 m) is adopted for construction. Timely acceptance after excavation, timely pouring retaining wall concrete.
When the above measures still don't work, the borehole should be backfilled with sand in time, the working face should be closed, the stratum should be reinforced by injecting double-liquid chemical grout in sections, and then the excavation should be continued, and the concrete for retaining wall should be injected in time with the steel sleeve formwork. Steel inserts can also be inserted around the digging well to prevent quicksand from flowing into the digging hole.
When quicksand excavation is serious, the borehole without quicksand nearby should be dug deep to make it play the role of precipitation and water collection. Then take the above measures to excavate quicksand and dig wells. The collecting well is located above the groundwater flow.
(3) Quality control and allowable deviation of hole digging.
(1) Before excavation, accurately locate the lofting well location, and lead the control point of logging center from the center of well location to the surrounding area. When the first borehole is dug, the formwork for retaining wall is installed, the position of formwork is corrected with the center point of the well, and cross control points are set on the first concrete retaining wall. The installation of each breast wall template should be corrected through the center point of the well, and the thickness of the breast wall should be checked.
(2) The hole formation of the dug well conforms to the allowable deviation in Table 1.5- 1.
Allowable deviation table of manual well digging construction 1.5- 1
serial number
project
Allowable deviation (mm)
test method
1
baseboard
Working well ≥350, receiving well ≥200.
20
Dipstick measurement
The length of retaining wall per cycle is ≤900.
-50
Diaphragm diameter (length)
Conform to design
2
Displacement deviation of well (perpendicular to the center line of well foundation)
50
Pull wire gauge
three
perpendicular/vertical
3‰
Hanging wire ruler measurement
four
Verticality of well string
H/ 1000
plumb line
five
Borehole diameter
50
Dipstick measurement
six
Bottom hole elevation
10
Rule and measurement
(3) The concrete for retaining wall shall be poured as soon as possible after drilling and excavation, and the pouring shall be completed at one time on the same day. When pouring retaining wall concrete, small-diameter plug-in vibrator and steel drill are used for tamping.
(4) The parapet formwork shall be removed after 10 ~ 12 hours according to the temperature and other conditions.
(5) After the hole is formed, remove the mud, residue at the bottom of the hole, eluvial soil, sundries and accumulated water. After inspection, quickly back cover.
(4) Safety measures for well digging construction
(1) In order to prevent ground construction personnel and objects from falling into the borehole, a guardrail with a height of 0.8m is set around the orifice for enclosure. The excavated earthwork shall be transported away in time, and silt and sundries shall not be piled up within 2m around the orifice, and the passage of motor vehicles shall not affect the safety of the shaft wall.
(2) The first semicircle welded with the channel steel tower is set at the top of the hole, and a frame cover is formed with1830× 910×18 plywood to ensure the safety of underground workers. In the process of earthwork hoisting, people stand under the cover plate to prevent falling objects from hurting people.
(3) Personnel use ladders made of steel bars in the well to go up and down the well. The ladder is welded firmly and anchored on the ridge set by the wellhead. Fasten the safety rope when people go up and down the well to ensure foolproof.
4 When the excavation depth of the borehole exceeds 5m, the toxic gas should be detected before the start of construction every day, and the gas should be supplied to the borehole for 5min, so that the turbid gas in the borehole can be discharged before the person can enter. When the hole depth exceeds 10m, the ground is equipped with special equipment to supply air to the hole, and the air volume is not less than 25l/s. When drilling at the bottom of the hole, increase the air volume, use instruments and small animals to carry out tests, and adopt wet operation to strengthen ventilation and dust removal to ensure personal safety.
5. All power supplies and electrical appliances on the construction site shall be installed and dismantled by certified electricians, and the electrical appliances shall be strictly grounded and connected to zero, and leakage protectors shall be used. Only after the electrical installation experience is qualified can the power supply be connected. Power is cut off in all boreholes, and it is forbidden to use one brake for multiple purposes. Wires and cables on the hole are overhead, and it is forbidden to mop the floor and bury the soil. Cables and wires in holes must be insulated to prevent wear, moisture and damage. 12V safety lights are used for lighting in the tunnel.
(2) Installation of working well equipment
During the construction of the working well, the equipment installation preparation on the working well can be carried out, including laying the brick wall of the mud pool of the thixotropic mud system, installing the mud treatment system, installing the mud pump and pipeline system that enter the mud, the screw pump and pipeline system that press the thixotropic mud, installing the ground operating system and the canopy of the operating system, and connecting the water and electricity.
After the completion of the construction of the working well, the equipment in the working well can be prepared for installation, including the installation of water sealing rubber at the wall-penetrating position, the installation of the integral jack-up, the installation of slurry pump and slurry discharge pipeline system, and the installation of measuring system.
④ Equipment installation in the working well.
The installation of equipment in the working well includes the installation of rear seat cushion, guide rail, oil cylinder bracket, oil cylinder and measuring shed.
Rear seat gasket installation
The backseat gasket transfers the reaction force of the thrust of the main jacking oil cylinder to the backseat wall of the jacking well. Through the back seat gasket, the reaction force of the oil cylinder can be evenly transmitted to the back seat wall, so that the back seat wall is not easy to be damaged.
Now, according to the drawings, line up the installation position of the back seat pad, mark the four corners of the back seat pad with red paint on the back seat wall, cut the wall within the pad, use bricks as the bottom, hang the back seat pad to the installation position, and adjust the horizontal and vertical directions (use the bottom of 2mm thin pad). The plane should be perpendicular to the jacking direction of the pipe jacking, and the dimensional error of positioning and installation should be controlled within 2mm. After adjustment, the rear seat pad and the rear seat wall should be filled.
Practice as shown in the figure:
Rail mounting
The guide rail of foundation pit is composed of two parallel guide rails, which have two main functions: one is to make the propulsion pipe have a stable guide rail in the jacking well and make the propulsion pipe enter the soil along this guide rail; Second, there should be reliable supports when the ring and arc top irons work.
Release the jacking axis of the pipe jacking at the bottom of the foundation pit, first adjust the center line of the guide rail to align with the jacking axis, and raise the height of the guide rail according to the drawings. When the longitudinal and elevation are adjusted, weld the guide rail firmly with the bottom reinforcement, fill the gap with concrete, and control the positioning and installation dimensional errors of the guide rail (including axis position, top elevation and distance between two rails) within 2mm.
C cylinder bracket and cylinder installation
The oil cylinder bracket is a bracket welded by channel steel, which plays the role of fixing the main top oil cylinder and makes the oil cylinder have a reliable bracket when working.
According to the jacking axis of pipe jacking released from the bottom surface of foundation pit, first adjust the center line of the support to align with the jacking axis, according to the drawings, pad the support to adjust the height of the support, when the longitudinal and elevation are adjusted, weld the support firmly with the bottom reinforcement, and fill the gap with concrete. After 24 hours, hoist the oil cylinder to the bracket and press it with steel plate, and control the positioning and installation dimension error of the oil cylinder bracket and the oil cylinder within 2mm.
D measurement shed erection
The measuring shed is located in the position of the oil cylinder and the rear seat cushion, which plays the role of protecting the instrument during measurement and serves as the base of the total station or electronic theodolite. The top is welded with Ф 25 steel pipe and covered with iron sheet.
Drainage of sump in working well
A 0.6m×0.6m×0.6m sump is set at one side of the jacking well. When the bottom plate is poured, the periphery of the sump is inclined to the sump position, forming a drainage slope. Set aside the position of sump when making the track, and collect the water flowing out of the pipeline and the water accumulated in the foundation pit. A submersible pump is arranged in the sump to pump the well to the sedimentation tank for sedimentation, and then it is discharged into the original drainage system.
⑤ Install ground equipment.
The ground equipment installation of the working well includes: erection of main control shed and installation of main roof device, erection of mud shed and installation of mud system equipment, and installation of ventilation shed and ventilation equipment. 35T truck crane is used to hoist pipe jacking equipment in working wells.
I. Erection of main control shed and installation of main roof device
The main roof device is mainly placed in the main control shed, including the main roof oil cylinder (underground), the main roof oil pump (including the control part) and the oil pipe. The propulsion and retraction of the main jacking oil cylinder are controlled by the control part of the main jacking oil pump, and the operation control of the whole pipe jacking machine is concentrated in the control cabinet, which is placed in a special container as the control platform of the whole pipe jacking machine.
The main control shed is welded with Ф 25 steel pipe and covered with iron sheet.
B. Construction of mud shed and installation of mud system equipment
The mud shed is welded with Ф 25 steel pipe and covered with iron sheet. An electric box, two mud pumps and a mud box are mainly placed in the mud shed.
C ventilation shed and ventilation equipment installation
The ventilation shed is welded with Ф 25 steel pipe and covered with iron sheet. A blower is mainly placed in the ventilation shed to prevent sun and rain.
⑥ Hoist the tool head into the well and debug the whole set of equipment.
After the installation of the upper and lower equipment in the working well is completed, all the tool heads transported to the site are hoisted into the well, the power cables, signal wires and oil pipes are connected, the whole machine is debugged on site, the whole jack-up frame is debugged, the mud water treatment system is debugged, and the laser theodolite of the measuring system is adjusted. Debugging work must be comprehensive and meticulous to ensure that the equipment is foolproof when it is officially jacked up.
⑦ Technical measures for in-hole construction
Pipe jacking access hole is one of the key links in the whole construction process, and the success of pipe jacking access hole is equal to half the success of the whole pipe jacking project. This project adopts manual well digging. After the completion of manual well digging, the retaining wall is drilled mechanically, and then the water stop ring of the hole is installed.
A treatment of working well going out of the hole: before going out of the hole, mechanically cut off the concrete of the shaft wall, weld the water-stop steel ring on the outside of the embedded parts of the shaft wall, and then install the water-stop rubber ring on the water-stop steel ring. When preparing to go out of the hole, cut off the steel mesh of the shaft wall, and jack it in immediately after cutting, so as to shorten the pause time. At this time, the water stop apron can play a role. Put the tool head into the wall-penetrating pipe, and the tool head is rigidly connected with the first section of concrete pipe to prevent the tool head from kowtowing. The construction of pipe jacking outside the tunnel is very important, and waterproof measures need to be taken at the exit.
B, receiving well entry treatment: when the pipe jacking reaches the wall position, cut off the sealing steel plate embedded in the reserved hole and quickly eject the tool head. In the process of going out of the hole, prepare enough straw. When sand flows through the wall, straw can be used to block the joints to prevent excessive sand loss. After the tool head is in place, fill the joint position with embedded pipes and seal the joint with quick-setting cement. Then use double liquid (cement slurry and water glass) to inject water.
⑧ Initial top wall
To mechanically cut the concrete of retaining wall, it is necessary to prepare enough water pump to pump water, hang the tool head, eject the jacking jack, align the annular jacking iron with the tail of the tool head, and slowly push the tool head into the wall-penetrating pipe. When the front of the cutterhead reaches the outside of the diaphragm wall, stop jacking, install all pipelines (power cable, signal wire, oil pipe, mud inlet and outlet pipe and thixotropic mud pipe), rotate the cutterhead and inject mud into the working chamber. When jacking in soft soil, in order to prevent the pipe joint from drifting, the first three pipes are integrated with the tool head.
(3), pipe jacking construction method
The total length of this project is 825m. The pipe jacking adopts Class III reinforced concrete DN 1200 and DN800 special pipe jacking and F-shaped steel ring interface, and is embedded with annular rubber ring to stop water.
1, construction preparation
(1) Preparation of production technology
(1) Construction survey, site setting-out.
(2) Determine the scope of pipeline construction and the exact location of all ground obstacles in the construction site, such as existing underground pipelines (determined according to the distribution data of existing underground pipelines along the line provided by Party A and the proven situation of manual trenching), telephone poles, green trees and nearby houses.
(3) Level the site and build construction roads. Try to use existing roads and pipelines as construction access roads.
④ Build temporary facilities and install temporary water and electricity. Repair the temporary drain pipe.
⑤ Level the site, prepare the stacking position of pipelines, and order the required materials such as iron well rings and well rings.
⑥ Processing and manufacturing of steel mesh and other non-standard equipment for top pipe.
⑦ Organize on-site construction personnel to study and review the construction drawings, conduct the blue prints.the design of various disciplines, and conduct design requirements and construction technical disclosure.
⑧ Compile the pipe jacking construction process card. Do a good job in retraining the operators of pipe jacking construction.
Pet-name ruby drawing temporary works and non-standard equipment and tools construction drawings.
2, jacking construction method and technology
According to the geological conditions of the construction site, soil distribution, pipe jacking workload and planned construction period (completed in three and a half months).
The pipe jacking method (1) is an earlier construction method: the working principle is to excavate the soil at the bottom of the pipe manually or mechanically (manual and mechanical jacking is adopted in this project), and then with the help of jacking equipment, the laid pipeline is jacked into the working pit according to the design center line and elevation requirements, and the soil is transported from the pipeline to the outside of the working well through horizontal and vertical transportation lines.
(2) Excavation and jacking
In this project, the rail is used as the guide rail (the pipe jacking is guided according to the designed center line and slope to ensure the accurate pipeline position before the pipe jacking is buried). ), the firm and accurate installation of guide rail has a great influence on the jacking of pipe jacking. Therefore, the installation of guide rail must meet the requirements of pipe jacking center, elevation and slope.
Lower the pipeline to the guide rail, install the jacking iron after it is in place, and check whether the elevation of the center and bottom of the pipeline meets the design requirements. Digging in front of the pipe can be carried out only after passing the inspection.
① Pipe jacking excavation and earth moving method in dense stratum.
Excavation in front of pipe is the key to ensure the quality of pipe jacking and the stability and safety of ground buildings. The direction and shape of digging in front of the pipe directly affect the accuracy of the pipe jacking position. Therefore, strictly control the surrounding area in front of the pipeline to avoid over-excavation. For dense cohesive soil, a gap of no more than 37.5px can be left above the pipe end to reduce the jacking resistance, and the lower part of the pipe end should not be over-excavated within the range of 1350 central angle to keep the pipe wall flush with the soil wall, or a soil layer with a thickness of 25px can be reserved and cut off during pipe jacking to prevent the pipe end from sinking.