A, deep mixing pile construction scheme
1. Overview
In order to ensure the safety performance of the retaining structure, deep mixing piles are reinforced outside the retaining piles. The section size of double-ended deep cement-soil mixing pile is 700* 1200, with an overlap of 200mm. The water-cement ratio is 0.55, the cement content 15% (natural bulk density of soil 18kn/m3), the 28-day strength of the pile is not less than 1.2Mpa, and the verticality of the pile bottom is less than 1/200. The absolute elevation of the top of deep mixing pile is+1.70 ~-10.8m, with 534 piles in total. The soil in the pit is reinforced by compaction grouting. Grouting pipe is arranged in a plum blossom shape, with a spacing of 800mm, cement content 12%, the length of grouting section in each hole is not more than 0.5m, and the grouting quantity in each section is not less than 0. 1 m3.
2. Process flow of deep mixing pile
3. Construction plan
3. 1 construction parameters
The deep mixing pile adopts the construction technology of two spraying and two mixing to ensure the uniformity of mixing.
3.2 Construction process
1. This subdivisional work shall be carried out after the construction of engineering piles, and the principle is not to affect the planned process arrangement of the main subdivisional work.
2. According to the engineering requirements of mixing piles, two mixing pile machines are respectively arranged for construction.
3.3 Construction preparation
1. Remove obstacles such as stones and old foundation in the pile-forming part to ensure the normal construction of the project.
2. Level and tamp the pile foundation, lay tracks and sleepers, and ensure that the pile driver does not sink during construction to ensure construction safety.
3. Do a good job in the maintenance of the equipment entering the site, so as to achieve corresponding matching, the best performance, convenient use and complete equipment.
3.4 Construction method
65438+ Arrange a 0.4m3 small excavator or manually excavate the sample tank (the excavation depth is about 1.2m, and the pile position deviation is not more than 50mm), reasonably pile up the residual soil and transport it abroad as appropriate.
2. Alignment in place: the mixing piles are constructed with double bits, and the overlap between piles is set to 20cm, and the construction interval shall not exceed 16 hours. Compaction grouting is used to reinforce piles.
3. Preparation for sinking: When the mixer sinks, it should run with no load and start the mechanical cooling circulation system. When it is normal, the wire rope can be loosened to make the mixer sink along the guide frame. The speed is controlled by the ammeter of the electric control device, and the working current shall not be greater than the rated value, generally controlled at 0.6-0.8m/min, and the working current shall not be greater than 70A. If the lower layer speed is too slow, mud can be supplied from the mud conveying system to facilitate drilling.
4. Curing agent slurry: According to the design, the mixing pile adopts the mixed liquid of 425# ordinary cement and water glass as the curing agent, and the dosage meets the design requirements (the dosage of water glass is 2% of the dosage of cement, the dosage of cement is 12%, and the water-cement ratio of grouting liquid is 0.5). The prepared cement slurry shall not be separated or allowed to stand for too long, and the cement slurry exceeding 2 hours shall be reduced.
5. First shotcreting and stirring lifting: the mixing head is lifted twice, and the mixing pile is grouted twice, with the first time accounting for 67% of the cement consumption and the second time accounting for 33%. After the mixing head sinks to the design elevation, start the booster pump, and after the slurry reaches the nozzle 1-2 minutes, the mixing head will mix the mortar with the soil, generally at a constant speed of 0.5m/min. When the mixing head is lifted to the designed top height by grouting, it is required that the cement slurry in the hopper is just emptied.
6. Repeated mixing and sinking: After the deep mixing pile is sprayed and lifted to the design elevation, turn off the mortar pump. In order to mix soft soil and mud evenly, the mixing head sinks again at a sinking speed of 0.8- 1.0m/min.
7. Second shotcreting and stirring lifting: After the stirring head sinks to the design depth for the second time, start the grouting pump for the second shotcreting and stirring, and the lifting speed is 1m/min. When the mixing head is lifted to the design elevation, the grouting pump is closed and the slurry in the hopper should be just emptied. When it is finished, it will form an 8-shaped columnar entity, which will be built one by one to form a wall-like entity.
8. Because the lifting speed of deep mixing equipment is generally 1m/min, and the specification requires that the lifting speed be controlled at 0.5m/min, it should be lowered and then lifted to ensure the uniformity and the strength of 15% cement mixture ratio can reach1.2mpa..
9. After the mixing shaft drops to a predetermined depth, start the pump to pump mud. The average lifting speed of the first bit shotcrete is less than 0.6m/min, and the second bit shotcrete lifting speed is 1m/min. When the mixing head is lifted to the specified height, the cement slurry configured according to the design should be delivered just now. It is especially important to note that the amount and pressure of slurry supply should be adjusted in time according to the actual situation during construction.
10. Each pile shall be mixed and sprayed at least twice. At the same time, the spraying process must be continuous, and the slurry must not be broken in the middle, otherwise it should be stirred and sunk 1 m before spraying.
1 1. Prepare cement slurry in strict accordance with the design mixture ratio, and the cement slurry shall not be separated.
12. Materials must be put into use with quality assurance and submitted for re-inspection.
4. Quality standards and acceptance specifications
4. 1 quality standard
Description of allowable deviation of serial number items
1 verticality ≤ 1/200
2 pile location ≤50 mm
3 Pile diameter +50 mm, -0 mm
4.2 Acceptance specification
According to the technical specification for foundation treatment.
4.3 Deep mixing intensity detection
1. The standard value of reinforced soil strength should be the unconfined compressive strength of 70.7×70.7×70.7mm test block at 28 days. The requirement is not less than 1.2Mpa, and the number of test blocks per working day is not less than three groups. The test block shall be kept underwater.
2. The three-day compressive strength of the mixing pile should be tested by light penetration test within three days after the pile is completed, so as to adjust the cement mixture ratio. The sampling frequency of light penetration test in mixing pile construction is 2%.
5. Construction quality control
5. 1 quality prevention measures
1. In order to ensure the verticality of mixing pile, attention should be paid to the flatness of lifting equipment and the verticality of guide frame to the ground. Generally, the verticality deviation is not more than 65438 0%.
2. In order to ensure the accuracy of the pile position, the positioning card must be used, and the deviation of the pile position is generally less than 50 mm ..
3. When pre-mixing the water tank, it is forbidden to work with water.
4. Any sinking pile washed by slurry conveying pipe must drain the water in the pipe before spraying concrete, and at the same time, the influence of washed pile on the strength of pile body should be considered.
5. When the curing agent slurry for mixing is poured into the hopper, it should be filtered with a sieve to avoid the slurry from caking and damaging the pump body.
6. During grouting, the foreground operation should closely cooperate with the background slurry supply, and the contact signal must be clear. The mud supply in the background must be continuous. Once the pulp is stopped for some reason, the front line must be informed immediately.
7. In order to prevent pile breakage and slurry separation, it is suggested that the mixer sink to half a meter below the slurry stop point, and then spray slurry when slurry supply is resumed.
8. If the machine is shut down for more than 3 hours, in order to prevent the slurry from induration and blocking the pipeline, it is recommended to dismantle the infusion pipeline first and clean it properly.
5.2 Quality management measures
1. Implement comprehensive, full-time and whole-process quality management, establish three-level quality assurance measures composed of team, project department and company, and accept the quality inspection and supervision of this project by the quality inspection team composed of design, Party A (supervision) or general contractor and construction unit.
2. Strengthen technical management: seriously implement various technical management systems, implement full-time post responsibility system before construction, and make technical disclosure, so that each construction worker can clearly understand the overall requirements of the project and deeply understand the responsibilities, quality and technical requirements of this post.
3. Implement the project quality and technical responsibility system, and establish a perfect quality management and quality information feedback network.
4. Establish process quality management protection measures and systems, define the responsible person for the key processes that affect the quality of the results, and the previous process is responsible for the next process. Any previous process that does not meet the quality standards shall not be transferred to the next process until it is corrected.
5. Implement a 24-hour shift work system for quality inspectors, strictly control the quality standards of each working procedure, and nip in the bud.
6. The quality inspection team must participate in the acceptance of purchased raw materials, and the materials used must conform to the relevant specifications of Shanghai.
7. Earnestly make all kinds of original records and construction diaries, so as to be accurate, timely and complete, and sort out and summarize the feedback information to guide the construction.
Second, the enclosure steel support construction scheme
1. Project overview
Horizontal steel supports are set in this project, with the center elevation of+1. 1m, two φ 609× 16 steel pipes are used for direct support, 400×400× 13×2 1mmH I-beams are used for splayed support, and φ 609×/0/mmh I-beams are used for angular support.
2. Construction preparation
1. Hold a safety technical disclosure meeting for construction personnel to emphasize the importance of construction quality and improve the quality awareness and technical requirements of construction personnel.
2. The general contractor is responsible for excavating the support groove and notifying the installation support team to enter the site three days before the installation support conditions are met. When materials are ready to arrive at the site, supports must be installed during ditching.
3. Prepare steel pipe supports, materials and equipment, check the specifications of various support materials in advance, and debug and maintain the required equipment and machines to ensure the normal construction.
3. Step of applying stress
This project is equipped with 1 set 100T jack and 2 sets 1 set of control boxes, and the stress is applied according to the design requirements. When stress is applied to each bearing, two jacks are applied at the same time and added to the design requirements. Plug the jacks with brake iron and record the applied stress.
4. Construction procedures
Pay-off-leveling welded steel column external support-assembling steel pipe support-prestressing-welding splayed support-installing hoop-checking the situation of each node-organizing completion acceptance-handing over the next working procedure excavation-monitoring during foundation pit excavation-removing support-exiting.
5. Technical measures for bracket installation
1. With the cooperation of Party A, copy the design drawings of steel support installation and the disclosure requirements of the general contractor, check the support position with the support axis, measure and check the actual length and size on site, and register according to the actual size of the support. After the steel support is hoisted in place, the levelness should be adjusted, and whether the connecting solder joints and bolts are firm and reliable should be checked. After the general contractor's supervision meets the requirements, it will be implemented by our company's professionals.
2. Install a steel-supported excavator to cooperate with hoisting construction, and arrange 12T truck crane to cooperate with vertical transportation on the north side of the foundation pit.
3. After the installation of the steel support is completed, the soil on the support should be covered more than 30cm after the acceptance by Party A, the general contractor, the supervisor and the design, and the support column should be clearly marked to remind the excavation unit to pay attention to the protection of the support system. During excavation, the subgrade box shall be supported by overhead steel, and it is forbidden for the excavation machinery to directly press on the support.
4. In order to ensure the construction progress, our company will consider the construction on normal sunny days 16 hours. In order to ensure construction safety, hoisting, installation and welding work are mainly carried out during the day, and welding is mainly carried out at night.
5. After prestressing, recheck the connection of each node. If necessary, each node will be reinforced and repaired, and the high-strength bolts between flanges must be re-tightened.
6. When the weld is fully welded, the welding wave on the surface of the weld shall be uniform, and there shall be no pores, slag inclusion, cracks and sarcoma. Strictly implement the acceptance system of welding quality records. After each working procedure is completed, slag removal and self-inspection must be carried out. After the inspection, the person in charge of construction shall notify the relevant personnel to carry out the inspection. (Information in duplicate)
7. Allowable deviation range of bracket installation quality: bracket plane axis deviation of 5cm, elevation deviation of 3cm.
6. Dismantle the support
1. The support shall be removed after the floor concrete reaches the design strength, and a written notice shall be issued by the designer or the general contractor, otherwise it shall not be removed.
2. Lift and dismantle the steel support with a tower crane. The steel support that cannot be operated by the tower crane is hoisted on the ground with a car crane or a two-legged pole. Two layers of car tires are stacked above the support to prevent damage to the foundation pit structure. Then, the support is dragged to the crane operation position with an electric hoist, and then loaded and transported away from the site.
7. Engineering quality assurance measures
1, our company adheres to the quality policy of customer first and quality first, and carefully organizes the construction to ensure the excellent quality of the project. Before the project starts, the construction organization and designers shall make technical disclosure to the construction team leader, make clear the quality requirements and standards of each working procedure, and the preventive measures for possible quality accidents, and then the on-site builder and monitor shall make a second disclosure to all construction personnel.
2. The eccentricity of the radial shaft of the mounting bracket must be controlled within the design requirements.
3, strengthen the inspection of welding quality, in strict accordance with the design requirements indicate the thickness of the weld, weld thickness is not indicated according to the steel structure construction specification.
4, after the completion of earthwork excavation, our company sent specialized technical personnel to the scene for night monitoring. If the retaining support is deformed or cracks appear in contact, the auxiliary welding must be strengthened immediately. At the same time, the supervision of Party A and the on-site duty personnel of the general contractor of civil engineering should discuss together and take corresponding measures immediately to ensure the safety of the foundation pit.
8. Safety measures
1, hoisting shall comply with the "ten no-lifting" regulations, welding and gas cutting shall comply with the "ten no-burning" regulations, and crane operation shall be commanded by special personnel during installation and dismantling.
2, night construction should have enough lighting, not only to keep bright lighting, but also to ensure the safety of construction electricity.
For the smooth excavation of earthwork and the stability of foundation pit, earthwork excavation must be carried out after the support is installed. The excavator digging the lower part of the support must work on the road, and direct contact with the support is not allowed. Paving should be laid more than 300mm above the support pipe, and it is required to be laid in two directions above the support.
Third, the construction scheme of retaining ring beam
1. Project overview
Φ 850 @1050 bored pile is used for the foundation pit enclosure of Building No.0 of Shimao Riverside Garden, and 1300×800 ring beam is set on it. A retaining wall with a height of 2500 and a thickness of 200 is tentatively set, and the elevation of the bottom of the retaining pile is-16.25m: the periphery is 2×φ700@500 deep mixing pile to stop water.
The ring beam is 800 meters high, 1300 meters wide, and the beam top height is+1.500 meters (absolute elevation). The top of retaining piles is anchored into the ring beam 50mm, retaining piles are anchored into the ring beam 70 mm, and the ring beam is made of C35 concrete.
2. Technical measures:
2. 1 template
2. 1. 1 template adopts seven splints, ribs adopt 50× 100 cubic meters, φ 12 opposite pulling screws, with horizontal spacing of 700 and vertical spacing of 500.
2. 1.2 The rib spacing of the seven splints is 350, and they are arranged vertically. Two steel pipes are arranged horizontally, and the opposite screws are pulled. See attached figure 3.3.2- 1 for details.
2. 1.3 Before the template is installed, the release agent must be painted, so as to dismantle the template and increase its service life.
2.2 reinforcement engineering
2.2. 1 Check the drawings carefully. If the local steel bars in the structure are too dense to ensure the construction quality, they should be submitted to the design department in advance for corresponding substitution and modification to ensure the construction quality.
2.2.2 According to the design drawings, make construction disclosure to the construction team, including binding sequence, steel bar specification, spacing position, protective layer pad, lap length and staggered position.
2.2.3 The steel bars used shall have the factory quality guarantee and welding test certificate, and the materials of various steel mills shall be sampled and tested, with sampling reports attached, and shall not be used blindly without testing.
2.2.4 Steel bars that are not straight in bending should be corrected before use, and steel bars contaminated by oil and sludge must be cleaned before use.
2.2.5 In the process of steel bar construction, if it is found that the steel bar collides with the built-in parts or other facilities, it should be studied and handled together with relevant personnel, and it is not allowed to bend, cut, dismantle or move at will.
2.2.6 In order to meet the requirements of protective layer specified in the design, lead wire pads should be made with 1:2 mortar in advance according to the thickness specified in the design, and the spacing is generally1.0m2..
2.3 concrete construction scheme
2.3. 1 The concrete is made of commercial concrete, with the ring beam number C35, and transported by pump truck.
2.3.2 The ring beam is poured in four times, and the position of the construction joint should be at the distance 1/3 between the two supports (subject to the built-in parts), and it is not allowed to stay at the corner.
2.3.3 Vibrators for concrete pouring should be mainly φ 70 vibrators, with some φ 50 and φ 30 vibrators, and the distribution density of vibrators should not be greater than 50cm.
2.3.4 The concrete must be poured in different skins, and it is not allowed to concentrate the cloth in one place, so that the concrete can flow by vibrating rods, and it is not allowed to cause excessive height difference.
2.3.5 Small-diameter vibrators should be used to vibrate the dense steel bars to ensure the compactness of concrete.
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