1. Compilation basis

1. According to the construction drawing of the pile foundation project in the G area of ​​the Southern District of Qingzhu Lakeside Residential District, California, China Railway Real Estate Shuiying

2. "Engineering Survey Specifications and Technical Instructions" (JGJ33–86)

3. "Code for Construction and Acceptance of Foundation and Foundation Engineering" (GBJ202-83)

4. "Technical Specification for Building Foundation Treatment" (JGJ79-2002)

5. "Geotechnical Engineering Survey Specification" (GB50021-2001)

6. "Code for Design of Building Foundations" (DBJ 15-31-2003)

7. "Safety Code for Power Supply at Construction Site of Construction Engineering" (GB50194-93)

8. "Technical Specification for Building Pile Foundations" (JGJ94-94)

9. "Code for Design of Building Foundations" (GB50007-2002)

10. "Technical Code for Testing of Building Foundation Piles" (JGJ106-2003)

11. Specific situation on site

2. Project Overview

This project is located in Area G, Phase 4, Shuiying California, Southern District, Qingzhuhupan Community, Qingzhuhu Town, Kaifu District, Changsha. 0.000 is 46.00m, frame structure. There are a total of 2 buildings in Zone G of this project designed for foundation treatment with long spiral bored pile foundations. The designed pile diameter of the long spiral bored pile is 500mm. Take fully weathered granite 5 as the bearing layer, the pile head into the bearing layer is not less than 1.2m, the standard value of the pile tip soil limit end resistance, fully weathered granite 5 is qpk =1700kPa; the characteristic value of the vertical bearing capacity of a single pile: pile length When the pile length is 13m, it is 450kN, and when the pile length is 20m, it is 800kN.

Concrete strength grade: C25 for concrete caps, caps, and foundation beams; C30 for piles; and C15 for the concrete strength grade of the foundation cushion. The pile longitudinal reinforcement adopts grade Ⅲ, 7 diameters of 12; the spiral hoop adopts grade Ⅰ, the diameter of 6, the spacing is 200, and the spacing of the dense section is 100; a 12 stiffening hoop is set every 2000; the longitudinal reinforcement is double-sided welding, and the length of the weld is not less than 5d , The joints of stirrups and longitudinal bars are welded firmly.

The thickness of the reinforced concrete protective layer of the pile body is 50mm, the cap is 40mm, and the foundation beam is 35mm.

After the completion of the pile construction, the integrity of the pile body shall be tested by the dynamic test method. The number of piles under the three piles or under the three pile caps shall not be less than 1 pile, and the number of piles shall not be less than 20% of the total piles; the other shall be adopted The static load test of the vertical compressive bearing capacity of a single pile shall be carried out for acceptance inspection, and the number of inspections shall not be less than 1% of the total number of piles, and no less than 3 piles.

3. General Situation of Engineering Geology

According to the survey report, the site stratigraphic sequence and field characteristics are described as follows:

1. Artificial filling (Q4ml)① (① is the stratum serial number, the same as below): brownish yellow, brownish red, mainly composed of cohesive soil and construction waste, etc., loose structure, uneven density, unfinished self-weight consolidation, slightly wet.

2. Silty clay (Ql) ②: brown gray black, mainly composed of cohesive soil, slightly shiny cut surface, no shaking response, medium dry strength and toughness, plastic, slightly wet.

3. Silty clay (Qal) ③: brownish yellow, mainly composed of cohesive soil, with reticulated patterned structure, slightly shiny cut surface, no shaking response, medium dry strength and toughness, hard plastic, slightly wet.

4. Sandy cohesive soil (Qel) ④: yellowish brown, reddish brown, grayish white, which is formed by weathering granite, and retains the original rock structure characteristics. Feldspar has been weathered into kaolin. The content of medium and coarse-grained quartz is more than 20%. It has strong water permeability, slightly shiny cut surface, no shaking response, medium dry strength, low toughness, hard plastic, and slightly wet.

5. Fully weathered granite (γ) ⑤: grayish white, beige, reddish brown, the main mineral components are alkaline feldspar, plagioclase, quartz, mica and a small amount of apatite, with semi-automorphic granular structure, massive structure, The rock has been completely weathered into dense and coarse sand, and the feldspar has basically weathered into kaolin, with poor intergranular cementation, and the original rock structure and structure can still be distinguished. Hard and slightly wet.

6. Strongly weathered granite (γ) ⑥: grayish white, yellowish brown, reddish brown, the main mineral components are alkaline feldspar, plagioclase, quartz, mica and a small amount of apatite, with semi-automorphic granular structure and massive structure , The core is clastic, fragmented, and massive. The rock block can be broken by hand, the cementation between grains is poor, and the original rock structure is clear. It is soft rock, broken, the basic quality grade is Ⅴ, and the rock quality index RQD is poor (<25).

Fourth, the overall deployment of construction

(1) Construction preparation work plan:

Construction preparation is the prerequisite for the entire construction and production. According to the project content and actual conditions of this project, the company and the project department jointly formulate a construction preparation plan. Lay a good foundation for the smooth progress of the project.

Construction preparation work schedule

(2) Technical preparation:

The preparation work before construction must be carried out carefully and conscientiously, otherwise it will cause waste of manpower and material resources. The scope of construction preparation can be divided according to different construction stages.

1. Organize all professionals to familiarize themselves with the drawings, conduct self-examination on the drawings, and be familiar with and master all the contents and design intent of the construction drawings. If problems are found, negotiate with the construction unit and design unit in advance, and participate in the design submission and comprehensive review of drawings organized by the construction unit, design unit and supervision unit.

2. Compile the construction drawing budget, and calculate the detailed quantity of materials, labor quantity, and number of large-scale machinery required for the pile foundation project according to the construction drawings, so as to make schedule and supply plans, control costs and reduce consumption.

3. Do a good job in technical clarification. Before the start of each process of this project, technical clarification is required. Technical clarification is an important system of construction enterprise technical management and an important factor to ensure the quality of the project. The purpose is to make all personnel participating in the construction have technical requirements through technical clarification. Be aware of it in order to organize the construction scientifically and carry out the construction according to reasonable procedures and techniques.

(3) Material production preparation:

Ensuring the supply of materials and construction machinery as planned is of great importance to the entire construction process, otherwise it will directly affect the construction period.

1) Material preparation

According to the analysis of construction schedule and construction budget, construction materials should enter the site in batches according to actual conditions.

2) Construction machinery preparation

According to the project site, construction work surface and construction period and other factors, the following main mechanical equipment is temporarily selected:

(4) Preparation for construction organization:

In order to achieve the goals of good, high-speed, safe, civilized, and low-consumption construction of this project, this project adopts the management system of establishing a project manager department.

The project manager department is composed of project managers, technical leaders, construction workers, full-time safety inspectors, full-time quality inspectors, materials officers, data officers, laboratory workers and other members. Under the guidance of the construction unit, the supervision unit and the company, it is responsible for the The implementation of the organization, coordination, control and decision-making of the construction period, quality and safety of the project, and the implementation of dynamic management of the entire process of production and construction elements.

The project has a total of 127 piles, the construction period is short, and the amount of labor required is not large. Before the start of construction, work out a labor demand plan according to the construction schedule, organize personnel to enter the site, arrange life, register and conduct entry education.

(5) Preparation for the construction site:

1) Construction site control network

Cooperate with relevant units to complete the on-site handover work, including measuring control points and relevant technical data, and review the control points. Measure and set up permanent stakes in the site according to the given control points, and protect them as the basis for engineering surveys.

2) Complete the on-site "three connections and one leveling" work.

(6) General layout of construction

1. Rent nearby residential houses for temporary construction.

2. Construction site layout: determined according to site conditions

3. The temporary water and electricity system on site for construction water and electricity utilization has been connected to the construction site.

4. Construction technology and measures

(1) Process principle

The concrete cast-in-place pile is drilled to the design elevation with a long auger drill. After stopping drilling, while lifting the drilling, the concrete is pressure-filled through the concrete hole on the inner tube drill bit. After pressure-filling to the design pile top elevation, the drill rod is removed Press the steel cage into the pile body. When pressing concrete to the top of the pile, the poured concrete must exceed the top of the pile by 50cm to ensure the strength of the pile top concrete.

(2) Process flow

Positioning of piles, rechecking → drilling rig in place → drilling to the design depth → final hole acceptance → pouring concrete → removing soil to lift the drill rod → pouring concrete to 500 mm above the top of the designed pile → lifting the steel cage and vibrating hammer → starting the vibrating hammer and lowering Insert the reinforcement cage → insert the reinforcement cage to the design elevation → transfer the drill to the next pile position → completion of construction → pile foundation inspection

1. Measure and pay off:

① Take the measurement control reference point submitted by the owner as the control point, establish a closed wire control network, which is set up around the site, and place small wooden piles on the piles, and small iron nails on the top of the wooden piles. Construction can only be carried out after the review is correct.

②Accuracy of construction survey: According to "Engineering Survey Specification" (GB50026-93).

2. The pile machine is in place: center the basically in place pile machine with a wire hammer, and adjust the position of the pile machine until the center of the drill hole coincides with the center of the pile; For the depth of the hole, a control ruler is made on the frame or the machine tube for observation and recording during construction.

3. Drilling: When the drill bit just touches the ground, close the drill bit seal first, and the drilling speed should be slow. The normal drilling speed can be controlled at 1～1.50m/min. During the drilling process, if the drilling rig is stuck, the rig shakes or drifts, the drilling should be stopped to find out the cause, and the drilling can be continued after corrective measures are taken. Drilling operations should be carried out continuously in shifts, and the drilling construction records should be filled in carefully. The drilling situation and the precautions for the next shift should be reported when the shift is transferred. You should always pay attention to the changes in the soil layer. Take soil samples at all the changes in the soil layer.

4. The drilled earthwork is cleaned up in time and transferred to the designated place for stacking.

5. Final hole: When the drilling reaches the design elevation, the representative of the design, construction, supervision, construction and other units shall check and accept in accordance with the relevant acceptance conditions and design requirements. After the final hole is confirmed, the drilling can be stopped.

6. Concrete pouring

①Concrete must meet the design and specification requirements. The slump of concrete should be controlled at 180-200mm with good workability and fluidity. The concrete slump shall be inspected on site. Unqualified concrete shall not be used in this project.

②When lifting the drill pipe close to the ground, slow down the pipe lifting speed and clean up the muck at the hole in time to ensure the quality of the pile head concrete.

③A dedicated person is responsible for observing the pump pressure and the lifting of the drilling rig. The lifting speed of the drill pipe should match the pumping speed. The lifting speed of the pouring should be controlled at 2.5m/min. It is strictly forbidden to lift the drilling and then fill the material to ensure the quality of the pile. Concrete pouring must be Infuse to the surface.

④ Make a set of test blocks for each pile machine and each shift, and a special person will be responsible for making, maintaining and submitting for inspection according to the specifications. The age is 28 days.

7. Reinforcement cage production: must meet the design requirements and the requirements of reinforced concrete construction specifications. A protective layer pad (the thickness of the protective layer is 50mm) must be set on the steel cage; a pad to control the thickness of the protective layer should be set on the outside of the steel frame. Concrete pads with the same strength as the pile body concrete or steel bars can be used to weld in the vertical direction. On the main ribs, the vertical spacing is 2m, the horizontal circumference shall not be less than 4, and they shall be evenly arranged, and the top of the frame shall be equipped with lifting rings. The length of the longitudinal steel bars shall be welded, and the joints of the vertical and horizontal steel bars shall be welded firmly. After the steel frame is made, it should be stored according to the pile section number; when storing, the number of layers of small diameter piles cannot exceed two layers, and the large diameter piles are not allowed to be stacked to prevent deformation; when storing, the lower part of the frame should be padded with square wood or other items , The upper cover.

8. Rebar cage installation

①Renovate the pile machine to integrate the long spiral construction pouring and the lower steel cage. The cage will be inserted within three minutes after the concrete is poured, reducing the time difference and reducing the difficulty of cage insertion

② After the long auger drills the hole and pours the concrete to the ground, clean the surface earth in time, and immediately carry out the post-reinforcement cage construction. Put the qualified steel cage on the steel pipe, and hang it on the hook set on the flange with a steel wire rope.

③Because the steel cage is long, the inserted steel cage must be observed for two-way verticality, and the two-way line is used for vertical angle arrangement. If the vertical deviation is found to be too large, notify the operator to stop and correct it in time. Pile positions that have been poured.

④In the process of lowering the cage, you must first use the vibrating hammer and the steel cage to press in, and then start the vibrating hammer when it can not be pressed in to prevent the deviation of the steel cage caused by the vibration of the vibrating hammer. The insertion speed should be controlled at 1.2~1.5m/ min.

⑤After inserting the steel cage into the design position, turn off the power of the vibrating hammer, then remove the wire rope, use a long auger to lift the steel pipe and the vibrating hammer out of the hole, and turn on the vibrating hammer every 3 meters during the lifting process to ensure the compactness of the concrete .

9. Pile head cleaning: After the pile is formed, without affecting the subsequent pile formation, timely organize the equipment and personnel to clean and transport the pile driving spoil. When cleaning the soil, pay attention to the protection of the completed pile and the steel cage, and the spoil should be stacked until Designate a location to ensure continuous construction.

10. Pile foundation inspection: 28 days after the completion of the construction of the cast-in-place concrete pile, the inspection will be carried out, and the inspection test will be carried out by a professional inspection unit. The inspection pile position will be determined by the supervision unit and the construction unit after a joint review, and the construction unit will cooperate in the production of the pile cap.

5. Project quality assurance measures

1. Guarantee items:

1) The raw materials and concrete strength of the cast-in-place pile must meet the design requirements and construction specifications.

2) The actual amount of concrete poured must not be less than the calculated volume.

3) The elevation of the pile top after pouring the concrete and the treatment of floating slurry must meet the design requirements and construction specifications. The elevation of the finished surface of the pouring concrete of this project is required to be 500mm higher than the design elevation of the pile top.

4) The depth of the hole must meet the design requirements of the supporting layer. For piles with end-supported piles, the thickness of the sediment should not be greater than 100mm.

5) Within 24 hours after the concrete is poured, adjacent piles within 5m are prohibited from hole-forming construction.

2. Allowable deviation items, see the following table:

Permissible deviation table of long spiral bored pile

Note: d is the diameter of the pile, and H is the length of the pile.

6. Safe production guarantee measures

1. Based on the project situation, establish a quality and safety management network on site to achieve a clear division of responsibilities.

2. Hold a quality and safety meeting once a week.

3. The construction machinery must hang a safety operation card.

4. The construction electricity shall be connected in accordance with the three-phase five-wire system.

5. Regularly check the quality and safety situation, establish a quality and safety management network on the spot, achieve clear responsibilities, and promptly take corrective measures for hidden accidents.

6. Implement a safety operation clarification system. The construction workers and team leaders must make safety clarifications at the same time when assigning production tasks, and shall provide written confession and oral explanation.

7. Before the implementation of the shift, check the safety facilities before starting the operation after there are no hidden dangers.

8. When the operation is stopped or after get off work, the power must be switched off and the box must be closed and locked.

9. When entering the site, you must wear a safety helmet as required, and you must wear a safety belt when entering the heights.

10. The materials should be stacked at the designated location on the general plan to ensure unobstructed roads.

11. Provide regular fire safety education to workers and strengthen fire protection awareness.

12. Establish a fire safety team with individual responsibilities and strict management.

7. Civilized construction and environmental protection measures

1. Establish a sound on-site civilized construction management organization, implement a post responsibility system, and conduct regular civilized construction inspections.

2. Strengthen the work of civilized construction education for workers, and implement a certificate-holding system.

3. Carry out the plane layout according to the construction organization design, strengthen the management of on-site materials, equipment stacking, pipeline layout and transportation, and ensure the smooth flow of the roads on the site.

4. Keep the on-site environmental sanitation.

8. Construction measures in rainy season

(1) Project measures in rainy season

During the rainy season construction period, the rainy season construction measures must be strengthened to ensure the realization of the target construction period.

1. Sufficient raincoats and rain protection tools are available.

2. Collect ten-month and monthly weather forecasts, and try to avoid pouring concrete in piles during heavy rains. In case of temporary heavy rain, the concrete surface that has been poured and not yet solidified should be covered with plastic film, and the concrete pouring interface should be covered with a canopy to prevent rain from directly washing the concrete. When the pouring surface encounters rainwater to wash away the cement slurry, and only stones and sand are seen, a layer of mortar with the same label should be mixed; if only rainwater penetrates into the pouring surface, you can properly add some dry cement before tamping and closing the surface. When pouring in the rainy season, the tester should test the moisture content of the sand and gravel, appropriately reduce the water consumption of the mix ratio, and ensure the accurate mix ratio.

3. During thunderstorms, employees should not approach poles, iron towers, overhead wires and grounding conductors of lightning rods within 10m.

(2) Construction site measures

1. Ensure smooth drainage of the site and no accumulation of water.

2. Develop a rainy season drainage plan, make good waterproof and drainage equipment, ensure that the road access in the rainy season is unblocked, and make drainage ditches on both sides of the main transportation road, and ensure unblocked drainage, and ensure that the roadbed sinks after heavy rains, resulting in unsmooth traffic.

(3) Protection of mechanical and electrical equipment and materials

1. The switch box of the electromechanical equipment shall be protected from rain and moisture, and the grounding protection device shall be installed. The mechanical and electrical equipment must be equipped with a rain cover to prevent rain from damaging the equipment. Hand-held power tools shall be equipped with leakage protection devices. The mechanical and electrical equipment shall be inspected after the rain.

2. The grounding devices of on-site mechanical equipment such as pile drivers shall be fully inspected. The grounding device, the depth, distance, rod diameter, and ground wire cross-section of the grounding device, grounding body shall meet the requirements of the regulations, and be remotely measured to prevent lightning strikes.

3. Take rain-proof measures for raw materials, semi-finished products and materials that are afraid of rain, store them in storage, stack them up, and have good ventilation.