1 construction sequence
The sequence of pipe jacking construction: old road crushing → pipe jacking working well and receiving well construction → pipe jacking construction → inspection well and internal pipeline construction → backfilling stone powder → road surface repair as it is.
2 Working well and receiving well construction
In this project, two working wells and three receiving wells are set, all of which are constructed by open caisson technology. Construction sequence of open caisson: foundation pit survey and setting out → foundation pit excavation → blade cushion construction → internal formwork and support of shaft barrel → steel bar binding → external formwork and support → concrete pouring in well → maintenance and formwork removal → plugging reserved holes → well point installation and dewatering → cutting cushion, digging and sinking → bottom hole grouting → pouring underwater concrete → binding bottom plate steel bars and pouring bottom plate concrete → binding back steel bars and pouring back concrete. The specific structure is as follows:
(1) survey and layout of foundation pit
According to the geological conditions revealed by the open caisson design drawings and engineering geological reports, the excavation depth of the open caisson foundation pit is 2m, the working distance from the outside of the open caisson blade foot to the edge of the foundation pit is 2m, and the slope of the foundation pit is 1: 1. After the site is leveled, calibrate the open caisson center pile, vertical and horizontal axis control pile and foundation pit excavation sideline according to the open caisson center seat. After construction lofting, the construction can only be carried out after the supervision engineer rechecks it accurately.
(2) Foundation pit excavation
After the boundary line of foundation pit excavation approved by the supervision engineer is determined, the excavation process can be carried out. 1m3 single bucket excavator for excavation, with manual cooperation. The floating mud at the bottom of the foundation pit should be cleaned up and kept flat and dry. Drainage ditch should be set around the bottom to communicate with the collecting well. The rainwater and groundwater collected by the collecting well should be pumped out in time to prevent the accumulated water from affecting the blade cushion construction.
(3) Construction of Blade Cushion
Blade cushion adopts sand cushion and concrete cushion with the same force.
A. Determination of sand cushion thickness
The thickness h of sand cushion can be calculated by the following formula:
N/B+γ sand H ≤ [σ]
According to the calculation results, the sand cushion thickness h of both the working well and the receiving well is 60 (cm).
Sand cushion construction adopts layered compaction with water, and the compaction tool is a flat vibrator.
B. Determination of concrete cushion thickness
The thickness of concrete cushion can be calculated by the following formula:
h=(G0/R-b)/2
According to the calculation results, the thickness h of the concrete cushion is 10 ~ 15cm (15cm for the working well and 10cm for the receiving well).
The surface of concrete cushion should be leveled with a level to keep it on the same level.
(4) formwork and support in vertical shaft barrel
Because the pipe jacking open caisson is about 9 meters high, the shaft concrete is poured in three sections, and the internal formwork is also installed in three sections. Wellbore formwork adopts combined steel formwork and local wooden formwork to cooperate with each other to ensure the sealing performance of internal model. The internal mold of blade root adopts brick structure, and the width is the same as that of blade root. What is the internal formwork support of the well? 48*5 steel pipe support. Steel pipe support must be built firmly, and scissors can be used to increase the stability of internal model when necessary.
(5) steel binding
The surface of steel bar should be clean, and the surface oil stain and rust scale should be removed before use; The steel bar should be straight without local bending, and the steel bar in the plate should be straightened; Butt welding and welding and sampling inspection shall be carried out for the main reinforcement in prefabricated members according to relevant regulations; Reinforced joints should be staggered, and in strict accordance with the national standard "Code for Construction and Acceptance of Concrete Structure Engineering" (GB50204-92). When steel bar is bound on site, the intersection shall be firmly bound with 2 1 # iron wire, and welded by electric welding when necessary. The specifications and dimensions of steel bars shall meet the requirements and regulations of design drawings. When binding steel bars, braces are used to fix the position of the second floor steel bars to ensure the design spacing of steel bars. In order to ensure the thickness of protective layer, cement mortar pads with the same strength grade should be set between reinforcement and formwork, and the pads should be firmly bound with reinforcement and staggered. After the steel binding is completed, it shall be reported to the supervision engineer for concealed acceptance. After concealed acceptance, the formwork can be erected outside.
(6) erection of external formwork and support
After the acceptance of steel binding, install external formwork and support. The inner and outer templates of the shaft wall are fixed with opposite pulling screws, and φ 16 round steel is used for the pulling screws, with water stop plates in the middle and iron plates at both ends to control the thickness and size of the shaft wall. The two ends of the round steel are hinged into threads and fixed with customized steel nuts. When the formwork is removed, the steel nut shall be removed first, and the exposed part shall be removed, and then it shall be leveled twice with waterproof mortar of the same label to ensure no water seepage. The external formwork support must be firm and firm to ensure that the formwork will not deform or run off when the concrete is cast.
(7) Cast shaft concrete
Template and support process is completed, must be approved by the supervision engineer. After acceptance, concrete can be poured. In order to shorten the construction period and ensure the engineering quality, commercial concrete is pumped. When pumping concrete, the hose of the conveying pipe can be directly put into the cast-in-place section, about 1 m away from the cast-in-place surface, so as to ensure that the concrete does not segregate.
Before concrete is cast, the positions and geometric dimensions of all kinds of reserved holes, reserved pipes and embedded parts should be strictly checked, and it is forbidden to leak and misplace.
The concrete shall be vibrated by an internal vibrator, and the vibrating rod shall be separated from the steel bar when inserted, but concrete segregation caused by uneven and dense concrete vibration shall be prevented. When vibrating concrete, attention should be paid to check the stress of formwork and reinforcement at any time to prevent the formwork from running off due to vibrating concrete.
The wellbore is poured with concrete in three sections: the average total height of the working well and the receiving well is 9 meters, and the wellbore is poured with concrete in three sections and sinks once. For the first time, the foot of the leaf is poured with a height of 2m, for the second time, 5m, and for the third time, 5m. When cast-in-place concrete is used, the construction joints should be completed in strict accordance with the requirements of the specification. Construction joints should be made into convex joints. When pouring, the concrete at the joints should be chiseled away and cleaned with water. When pouring, first use 12% UEA mortar to condense into slurry, and then lightly pour the first layer of concrete, and vibrate it tightly to avoid honeycomb formation and affect the quality of open caisson.
In the process of concrete pouring, we should also do a good job of concrete block to ensure the perfection of quality assurance information.
(8) Maintenance and form removal
The concrete shall be cured in time after being cast, and the curing method can be natural curing and plastic film covering. In the process of curing, the concrete surface needs to be watered and wet, and it is forbidden to damage the concrete by spraying water with a water pump. When curing, it is necessary to ensure that the concrete surface is not white, and it should be cured for at least seven days. During the curing period, the concrete surface shall be free from pressure, impact and pollution.
Pay attention to the time and sequence when ripping. The time of form removal should be controlled within 3 ~ 4 days after concrete is poured, and premature or late form removal is not conducive to concrete maintenance; Generally, the sequence of form removal is from top to bottom, and attention should be paid to avoid damaging the concrete surface. Cast-in-situ concrete is cast in sections, and the last row of formwork is reserved for upward formwork connection.
(9) seal the reserved holes.
Set and close all kinds of reserved holes in strict accordance with the requirements of design drawings to ensure that the reserved holes are watertight during the sinking of open caisson.
(10) well point installation and dewatering
In order to ensure the smooth sinking of open caisson, drainage sinking method is adopted. Use the well point to pump groundwater and reduce the groundwater level. Well points are arranged around the foundation pit, and pre-pumping is carried out in advance before excavation.
(1 1) Chisel off the cushion layer and dig for sinking.
Only after the concrete strength meets the design requirements can the open caisson sink. When sinking, the concrete cushion and brick internal mold at the root of the blade should be chiseled first.
The excavation tool is a grab excavator and hoisted out of the well. The sequence of open caisson excavation should be slightly lower in the middle than around, and the elevation difference of open caisson excavation should be controlled within 1 m. It is forbidden to dig at the bottom of the deep tank to prevent the danger of open caisson inclination caused by sudden sinking.
In addition, the sand filling outside the shaft wall must be uniform and full, so that the friction around the open caisson is similar and the sinking is even. When the open caisson sinks, it should be prevented from tilting, and the problems should be corrected in time. When the sinking of open caisson is difficult, other measures should be taken, and sudden sinking caused by a large number of deep excavation is not allowed.
Open caisson digging works continuously in three shifts, without stopping halfway, to ensure that open caisson sinks in place continuously and safely.
When the distance between the cutting edge and the design elevation is 1.5m, the sinking speed of open caisson should be gradually slowed down, and the digging height difference should be controlled within 50cm. When the open caisson approaches the elevation, anti-sinking measures should be taken in advance. Anti-sinking measures can be used to dig out grooves with design elevation at intervals around the blade foot, fill in the square wood, and pay attention to the throwing coefficient. It is forbidden to overbreak and overbreak.
(12) settlement observation
During the sinking of open caisson, the elevation of open caisson must be measured at any time to ensure uniform sinking, and the sinking of open caisson should be recorded. After the open caisson sinks to the design elevation (including throwing high), the surface floating mud and other sundries should be removed first. The open caisson foundation is based on clay and fully (strongly) weathered sandstone. If the actual situation is found to be inconsistent with the design during the construction, the design shall be notified in time for handling. At the contact surface between the bottom plate and the blade foot, all surface concrete must be chiseled and exposed with stones to facilitate the combination of new and old concrete.
(13) foundation grouting
The basement adopts double liquid grouting to prevent seepage. Grouting is carried out by grouting tank. When grouting, try to match the grouting ratio in the formal construction to test the applicability of the ratio. Grouting adopts 32.5R fresh ordinary portland cement mixed with 2% sodium silicate, and the water cement ratio is not less than 0.5. The grouting rate is 20%, the grouting pressure is 0.3- 1.0MPa, and the spacing of grouting holes is 0.8m m.
(14) pouring underwater concrete with back cover
When the cumulative subsidence of open caisson within 8 hours is not more than 10mm, underwater concrete can be poured for back cover. The concrete label is C20.
(15) Tie the bottom plate reinforcement and pour the bottom plate concrete.
After the back cover concrete is completed, the bottom plate reinforcement can be bound on it. When binding steel bars, the connection between the steel bars at the leaf foot and the bottom plate and the spacing between the upper and lower layers of steel bars should be ensured, and the concrete surface at the leaf foot should be chiseled to expose stones, so as to facilitate the combination of the concrete at the leaf foot and the bottom plate. After the concrete of the bottom plate is poured, it should be cured in time to ensure that its surface is not exposed, and to prevent the drastic change of sunshine and temperature difference, so as to avoid shrinkage cracks on the bottom plate and affect the construction quality and use function of the open caisson. Before pouring concrete, the guide rail (60 rails) shall be embedded in parallel along the jacking direction to guide the pipe jacking.
(16) Tie steel bars and pour back concrete.
Then, the back wall is constructed. The size of the back wall is 5×0m×0.5m, and the reinforcement is in the form of double reinforcement. The horizontal reinforcement is Ф18 @150mm, the horizontal reinforcement is Ф16 @/500mm, and the longitudinal reinforcement is Ф14 @/.
3 pipe jacking engineering construction
(1) Selection and installation of jacking equipment
Main jack: it is the main equipment in the jack-up system. For the sake of safety, the configuration of jacking equipment should be small, so as to facilitate parallel jacking at intervals. According to the estimation of jacking force, the main pipe jacking station is planned to be equipped with four 2000KN hydraulic jacks, which are symmetrically arranged left and right. The master cylinder oil pressure is supplied by electric oil pump, and the jack stroke is 1500mm.
Other equipment: including guide rail, jack bracket, top iron, pressure dividing ring, rear bearing wall, operating platform, ladder, etc. (pictured)
After the floor of the working well is completed, set up the safety fence and ladder, and then hoist the above equipment into the well with a crane at the edge of the working well, and install it according to the required accuracy.
(2) Selection and arrangement of equipment on the well
Pneumatic system: including air compressor, air filter, gas storage tank, pneumatic pipeline, one-way valve, pressure regulating valve, barometer, safety valve, etc. The system not only provides compressed air for the nose pressure chamber, but also provides ventilation for the pipeline.
1 6.0m3 air compressor is planned for the pipe jacking working well of this project. In order to prevent the air compressor from generating noise, it is planned to adopt an electric air compressor with less noise and install it in a double-wall sound-proof container.
Hydraulic system: including high-pressure oil pump, control valve, overflow valve and tubing tank, etc. Its function is to provide pressure oil for the main jack and the head correction jack group.
This project is equipped with 1 hydraulic system, the high-pressure oil pump is 3 1.5Mpa, and the oil pump flow is 18L/min.
Grouting system: including mud pit, mixer, grouting pump, pipes and various gate valves.
Hoisting equipment: This equipment mainly considers hoisting a single DN800 concrete pipe, and the dead weight of the single pipe is about 1 .6t.1set 16t truck crane is selected.
(3) Pipe jacking
When all the preparations inside and outside the well are completed, the nose can be hung on the guide rail in the well, the direction can be adjusted, and the pipe jacking can be started. The front wall of the working well is provided with holes for the organic head and the outlet of the pipeline. In order to prevent water and soil outside the well from flowing into the working well from the gap between the reserved hole and the outer wall of the head, a dynamic sealing device is set between the reserved hole and the pipeline.
The construction technology of this hole is as follows:
(4) Hole sealing structure
The function of the sealing structure of the outlet hole is to prevent mud from flowing into the well from the gap between the pipe joint and the hole during pipe jacking construction.
According to the center line of the pipeline and the position of the reserved hole in the shaft wall, an inner ring of steel structure is made, a rubber water stop plate is installed on the inner ring, the ring is installed between the reserved hole and the pipe joint, the periphery of the ring is welded on the embedded steel plate of the hole, and the rubber of the inner ring is close to the pipe joint. (pictured)
(5) wall breaking and jacking
When the front end of the nose enters the hole sealing ring, it can be pushed through the wall. The reserved hole of the working well is temporarily blocked with brick, and a part of the inner wall is cut off with a pneumatic pick before jacking, and then the nose is pushed forward, and the outer wall is broken with the knife edge at the front end of the nose and cut into the soil, so that the normal pipe jacking construction can be carried out.
When there is sandy soil layer with strong water permeability outside the hole, a certain range of soil around the hole should be tamped and grouted in advance to prevent external water and soil from entering the working well.
(6) Direction monitoring
Only by controlling the direction of the jacking hole can the whole pipe be jacked well, but if the jacking hole is not good, it is difficult to jack the whole pipe well. Therefore, we must strictly control the accuracy of the pipe jacking hole, and adopt tracking measurement to adjust the direction and elevation deviation of the nostril at any time.
(7) Jacking construction
When the tool pipe is jacked into the soil, leave its tail on the guide rail for about 300 mm, retract the jack piston rod, remove the jacking and pressure dividing rings, install the pipe joint, and start the pipe jacking construction. When installing the pipe joint with telescopic jack, it is necessary to temporarily support the nose or the pipe joint behind it to prevent the nose from retreating under air pressure and causing the ground to collapse. Temporary support measures should be maintained until the frictional resistance of the outer wall of the pipeline is greater than the air pressure reaction force. The following is a brief description of pneumatic pipe jacking technology.
A. Brief introduction of pneumatic pipe jacking
Pneumatic pipe jacking is to set two pneumatic sealing doors in the tool pipe (nose) in front of the jacking pipe, close the first door, and fill the front cabin with compressed air (the air pressure is about 0.030mpa, which is equivalent to the head pressure of 3m deep water). Because compressed air permeates into the gap of the soil layer in front of the tool pipe, the groundwater in the soil layer in front of the tool pipe is pushed far away from the pore of the soil, which provides a waterless and stable environment for the tool pipe operation, and the pressure of the gas also supports the front of the machine head.
When the second door is closed and pressurized, so that the pressure in the front cabin of the rear cabin is equal, the first door is opened, and the pipeline is pushed forward to transport the soil dug in front of the nose to the transfer cabin between the first and second doors; Then close the first door, the air pressure will continue to stabilize the front cabin of the nose, then gradually decompress the rear cabin to zero, and then open the second door to connect the rear cabin with the pipeline and transport the mud of the transfer cabin to the working well. Pipe excavation jacking, excavation quantity and jacking length match. This is a full-pressure manual excavation jacking method, and workers need to work under pressure.
B. jack-up balance control
Pneumatic balance pipe jacking is a brand-new construction concept. Firstly, during the jacking process of the pipe jacking machine, the pressure of the air cabin is in equilibrium with the groundwater pressure and earth pressure of the soil layer where it is located; Secondly, its excavation volume and the soil volume occupied by tunneling machine jacking are also in a state of balance.
In the process of jacking, if the pressure p in the pressure chamber is less than the groundwater pressure and active earth pressure P 1 of the soil layer, the ground will settle. On the contrary, if the pressure of the air cabin is greater than the groundwater pressure and passive earth pressure P2 of the soil layer, the ground will uplift, which is a dynamic balance process. We need to control the engine room pressure between P 1 and P2, which can be called balance. The technological process of artificially unearthed pneumatic pipe jacking is as follows:
(4) Grouting reinforcement and drag reduction during construction.
The sewage pipe of this project crosses the road and there is a gas station next to it, which requires high ground settlement, and quicksand is easy to appear during pipe jacking construction, which affects the smooth progress of pipe jacking and the safety of surrounding buildings. In order to prevent collapse and other diseases during pipe jacking construction, to ensure that the impact of engineering construction on the surrounding environment is minimized, and to ensure the safety of surrounding buildings, grouting reinforcement measures are taken in front of the pipe end to strengthen the soil, and then jacking is continued.
A. Cement fly ash slurry is used for grouting, the ratio of cement fly ash slurry is 3: 7, and early strength agent is added.
B. Drill 1 block in four directions at the front end of the pipeline? 32 holes, Will? 25 grouting pipe nicks, and the depth of grouting pipe nicks is 3m ~ 4.5m/ day.
C. mixing the cement slurry. The cement slurry shall be stirred with a 200-liter mixer, and the dosage of water and cement shall be strictly controlled during stirring. The cement slurry is too thin, the reinforcement effect is not good, the consolidation time is long, and the cement slurry is too thick, which makes it difficult to press in. Controlling the consistency of cement slurry is the key to grouting.
D. Start the grouting machine and press the cement slurry in.
E clean the grouting equipment immediately after grouting.
F jacking 3m/ knot each time, grouting once, alternately, greatly reducing water inflow and preventing landslide.
G. After injecting cement fly ash slurry, the resistance of pipe jacking is increased, and thixotropic mud is added around the pipe jacking to reduce the resistance. In the process of pipe jacking construction, injecting thixotropic mud into the outer wall of the pipeline to fill the gap around the pipeline is an important measure to stabilize the soil layer, prevent landslide and ground settlement, and reduce jacking resistance to realize long-distance pipe jacking.
Grouting pipe is located at the end of the nose, and then synchronous grouting is carried out for pipe jacking. In order to make the mud jacket formed on the periphery of the pipeline always play the role of supporting the stratum and reducing the resistance, it is necessary to track and supplement the mud at appropriate points in the relay room and the concrete pipeline to supplement the mud loss during jacking. The grouting process is as follows: pulping and standing → grouting → pipe jacking (grouting) → pipe jacking stop → stop grouting.
H. grouting equipment
Grouting system equipment includes: ① grouting pump (screw pump, displacement 1000L/min, pressure 3 MPa); ② Agitator; (3) grouting pipe (the main pipe is φ50mm steel pipe and the branch pipe is φ25mm rubber pipe); ④ Pipeline connection; ⑤ Control valve; ⑥ Pressure gauge.
I. Mud preparation
Thixotropic mud consists of bentonite, water and additives in a certain proportion. The weight proportion of thixotropic mud in the construction site is as follows:
Water: bentonite = 8: 1 bentonite: CMC = 30: 1
In this project, it is planned to purchase bentonite bagged composite materials, and add water to stir them at the construction site.
J. Quantity and pressure of grouting
The first grouting amount is 1.5~2.0 times of the annular gap around the pipeline. Grouting pressure depends on buried depth and natural weight of soil. 2γH(kPa) is proposed for this project, where γ is soil weight and h is pipeline depth. In the process of jacking, the grouting quantity and pressure should be appropriately adjusted according to different soil conditions and the change of overburden thickness.
K. arrangement of grouting holes
Each grouting section is provided with four grouting holes, which are arranged at 90 degrees along the circumference. Grouting holes shall be processed in the factory.
The grouting section shall be located at the nose and its back every10m.
Length grouting method
During each jacking, sufficient grout must be injected into the first grouting section behind the head of the pipe jacking machine to form a complete grout sleeve, and other sections shall be followed, grouted at constant pressure and quantitatively in turn.
4, pipe jacking measurement, rectification technology
(1) pipe jacking measurement
Ground and underground survey control systems must be established according to the set pipeline centerline and working well location. Control points should be located in places that are not easily disturbed, with clear sight and easy to check, and protected, and should be checked regularly during construction.
A measuring platform is set behind the pipe jacking working well, and its temporary leveling points are introduced from the ground leveling points, so as to check and adjust the instrument elevation during the shift change. The axis of pipe jacking is introduced into the working well according to the designed pipeline axis by theodolite, and then observed in the center.
Before the nose comes out of the hole, the axis and elevation of the nose cutting edge must be accurately measured, and the data should be fed back in time to finally adjust the nose installation.
Whether the pipeline is jacked along the axis of the design pipe shall be checked by measurement. Pipeline axis deviation is measured and controlled by theodolite dividing line method, and elevation deviation is measured by level.
Measuring frequency: Generally, it is measured once every 500mm jacking, and the frequency should be increased under special circumstances.
After the whole section is jacked, the axis position and elevation shall be measured at the joint of each pipe joint, and the relative elevation shall be measured when there is a gap.
(2) pipe jacking rectification
Deviation correction means that after the nose deviates from the design axis, the direction of the end face of the nose is changed by using the deviation correction jack arranged at the back of the nose to reduce the deviation, with the aim of jacking the pipeline along the design axis. The quality of nose rectification will directly affect the quality of pipe jacking construction.
Jack-up rectification is to adjust four rectification jacks for grouping operation. If the pipe is on the left, the jack will extend to the left and contract to the right, and vice versa. If there is elevation and direction deviation at the same time, the side with large deviation should be corrected first. When jacking, the direction of the nose must be strictly controlled, rectification should be carried out at any time, and the line shape of the pipeline should be well controlled.
When rectifying the deviation, it should be rectified in jack-up, gradually corrected at a small angle, and frequently adjusted and fine-tuned. The rectification work should be carried out under the guidance of simulation analysis.
When the head of the pipe jacking machine rotates, methods such as adding counterweight in the opposite direction in the pipe or providing rotation correction torque at the intermediate station can be adopted until it is normal, so as to prevent the deviation from increasing and affecting excavation and measurement.
5 Artificially unearthed
In this project, the pipe is excavated manually, and the soil outside the pipe is transported out mechanically. Centralized stacking, and then transported to the spoil ground outside Highway 6.
6 Ventilation and lighting measures
Ventilation in pipe jacking, if necessary, go in to repair equipment, etc. Ventilation is needed before entering the pipeline. Forced ventilation measures are adopted, and air is forced to enter the pipe jacking tool head through 1.5 inch steel pipe with fan. Power supply for lighting construction adopts 380V three-phase five-wire system, and the lighting connecting the ground, working well, pipeline, tool head and pipeline is supplied by 12-24V low-voltage power supply.
7 Other auxiliary construction methods
(1) Building shell
Some working wells and receiving wells in this project are located around, and arc-shaped colored profiled steel plates are used for enclosure. The fence range is 10×20m.
(2) Safety guardrail around the working well
Safety guardrails are set around the working well, with steel bars as the skeleton, with the height of 1.2m, and the lower part of 18cm is closed with wooden boards, and a safety net is hung on it.
(3) Escalator in the working well
There is an escalator in the working well. The escalator adopts angle steel L75×75× 10, and the steps are strengthened (diameter 20mm, spacing 30cm, L=500mm).
(7) Working well platform
The working wellhead is provided with a working platform for vertical transportation of earthwork and tools. The beam is made of four 30# I-beams (L= 10m), paved with15 *15m3, and then paved with 10mm thick steel plates.
8 inspection well construction
After the pipe jacking construction is completed, the masonry construction of the inspection well can be carried out. Inspection wells are basically built in the original working wells and receiving wells. In the process of construction, our company will strictly follow the design drawings. Different methods are used to build different types of inspection wells and receiving wells.
The inspection wells in this project are brick inspection wells. During the construction of the inspection well, it is required that the inspection well adopts MU7.5 brick, the foundation adopts C 10 concrete cushion, and the inner wall of the inspection well adopts cement mortar.
Construction process flow chart:
Install the well ring and manhole cover
C30 concrete is prefabricated in the well circle, and the bottom of 1: 3 cement mortar seat is paved. The manhole cover adopts a new type of nodular cast iron anti-theft well ring cover. In order to ensure the smoothness of the manhole cover and the pavement, our company will complete the installation of the well ring and manhole cover before the pavement construction according to the design elevation and vertical and horizontal slope of the pavement.
9 stone powder slag backfill
Backfilling stone powder slag requires water compaction, one-time vibrating insertion and two-time flat vibration construction technology. Using the fluidity of water and the permeability of stone powder slag, the loose surface of stone powder slag is pumped and poured by a water pump, and the pores of stone powder slag are filled through the permeability of water, and the vibrating operation is carried out by using plug-in vibrators, plate rammers and other tools to achieve the compaction effect. When backfilling, the maximum filling thickness of each layer is 30cm, which shall be compacted by layers. When pressing, both sides of the pipeline shall be symmetrical, and the pipeline shall not be displaced or damaged. Backfill construction should comply with the following provisions: ① The water pressure should be real-time, the scope of one-time irrigation should not be too large, and drainage should be strengthened; (2) Plug-in vibrators can be inserted in rows or staggered, and they are not allowed to be mixed to avoid vibration leakage. The moving distance of the vibrator is not more than 500mm, and the vibration time of each point is 30s, subject to the fact that the surface of the stone powder slag no longer sinks obviously. Insert quickly and pull slowly when operating. When vibrating, the vibrator twitches slightly up and down to make the vibration uniform. (3) The plate rammer must be rammed vertically and horizontally for more than two times, and should be rammed together during tamping, and no tamping shall be missed.
10 pavement repair
Restore the pavement as it is, and the specific structure is the same as the new pavement structure diagram.
The detailed information of "Main Construction Scheme of Sewage Pipe Jacking Project" can be found in the link of Zhong Da Consulting Design, and all relevant building construction information you want is available.
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