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Suhe Special Zone Supporting Pile Foundation Project

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Suhe Special Zone Supporting Pile Foundation Project

  • Categories:Case
  • Time of issue:2021-08-05 10:45

(Summary description)The proposed building is located to the east of Wuchang Luxiang, with Luoyu Road on the north side and Plot A of Optics Valley World City on the south side. The pile type adopts manual digging pile, and the strength grade of pile core concrete is C30. The pile diameter is 0.9m.

Suhe Special Zone Supporting Pile Foundation Project

(Summary description)The proposed building is located to the east of Wuchang Luxiang, with Luoyu Road on the north side and Plot A of Optics Valley World City on the south side. The pile type adopts manual digging pile, and the strength grade of pile core concrete is C30. The pile diameter is 0.9m.

  • Categories:Case
  • Time of issue:2021-08-05 10:45
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Information

1. Project Overview

The proposed building is located to the east of Wuchang Luxiang, with Luoyu Road on the north side and Plot A of Optics Valley World City on the south side. The pile type adopts manual digging pile, and the strength grade of pile core concrete is C30. The pile diameter is 0.9m.

2. Engineering geological conditions

The geological conditions of the project site are detailed in the "Geotechnical Engineering Survey Report for Block B of Optics Valley World City" provided by the Central South Survey and Design Institute. The specific stratum conditions are as follows: (1) Miscellaneous fill; (2) Clay; (3) Residual soil ; (4)-1 strongly weathered mud shale; (4)-2 moderately weathered mud shale.

2. Compilation basis

1. Bidding documents for the foundation pit support project in Suhe Special Economic Zone

2. "Code for Design of Concrete Structures" (GB50010-2002)

3. "Code for Design of Building Foundation Foundation" (GB50007-2002)

4. "Code for Acceptance of Construction Quality of Building Foundation Engineering" (GB50202-2002)

5. "Code for Construction Quality Acceptance of Concrete Structure Engineering" (GB50204-2002)

6. "Technical Specification for Building Foundation Piles" (JGJ 94-2008)

7. "Technical Specification for Testing of Building Foundation Piles" (JGJ 106-2003)

8. "Code for Loads of Building Structures" (GB50009-2001)

9. "Technical Specification for Testing of Building Foundation Piles" (JGJ 106-2003)

10. "Basic Technical Specifications for Building Foundations" (DB42/242-2003)

11. Other relevant construction and acceptance specifications and procedures.

3. Equipment selection

Due to construction period requirements and based on geotechnical survey data and actual construction experience, rotary drilling rigs can be used to bore the piles for the project. The drilling rig equipment uses a China South Locomotive rotary drilling rig. If the selection of the above equipment is affected by the ground and cannot meet the requirements of the hole quality and construction period, the rotary drilling and manual digging are used to ensure the quality and construction period of the project.

Fourth, the construction plan

1. Rotary drilling construction technology and method

a) Construction technology

 

a

 

b) Construction method

1) Measurement control

(1) Before opening the hole, the pile position should be positioned accurately, and positioning gantry piles should be set outside the pile position.

(2) The pile position axis adopts a cross control network and reference points on the ground. When the drilling rig is in place, make sure that the deviation of the verticality is not more than 1%.

2) Hole formation:

1. In the process of drilling, the continuous cylinder type soil is used to drill into the hole.

2. The drilling rig is in place: crawling to the pile to be drilled through its own crawler, and the machine's own computer controls the horizontal and vertical adjustment of the drilling rig's mast and the fuselage.

3. Buried protective tube: After the drilling rig is in place, under the guidance of surveying and construction personnel, the drill point is aligned with the center of the pile position, and the drilling rig is rotated to a certain depth to take out the soil and then lower the protective tube. Generally, the buried depth of the protective tube is 1-2m, and the protective tube should be about 30cm above the ground according to the site conditions.

4. Re-measurement and correction of the deviation between the pile position and the center of the protective tube: After the protective tube is buried, the pile position review and correction will be carried out by the surveyor and the supervisory representative. After this process is completed, apply for the hole-opening notice and drill into the hole.

5. If the rotary drilling rig is unable to dig normally due to stratum reasons, an artificial pneumatic pick is used instead, and the protective tube is welded and pressed to the bottom of the hole to act as a protective wall. When the digging depth exceeds 10m, mechanical ventilation must be used. The lighting in the hole must use 12V safety voltage and explosion-proof lamp; the well hole must be equipped with a firm and reliable safety ladder to facilitate the construction personnel to get on and off. When the digging work is suspended, the hole must be covered.

2. Fabrication and placement of steel cage

a) The production of steel cages must be carefully processed according to the requirements of the design drawings.

b) The variety, steel number and size specifications of the steel bars should meet the design requirements, and the production deviations should meet the following requirements:

Main rib spacing: ±10mm

Stirrup spacing: ±20mm

Reinforcement cage diameter: ±10mm

Length of steel cage: ±50mm

Curvature of main bar: ≤1%

Reinforcement cage bending degree: ≤1%

b) Reinforcement cage welding requirements:

c) For the steel cage made in sections, the length of the steel bar is connected by single-sided lap welding, the length of the weld is 10d, and the closed hoop and the reinforcing ring are single-sided lap welding, and the length of the weld is 10d. The joints should be staggered during welding of the main reinforcement. The number of reinforcement joints in the section should not be more than 50% of the total number of main reinforcements. Most of the spiral stirrups should be spot welded with the main reinforcements to increase the strength of the reinforcement cage.

d) When tie-welding, the upper and lower main reinforcement positions are aligned to keep the upper and lower axes of the steel cage consistent.

e) Reinforcement cage protection layer requirements:

(1) When the steel cage is inserted into the hole, it should be aligned with the hole position and placed slowly into the hole. After the steel cage is inserted into the hole, it should be lowered slowly without turning left or right.

(2) The dirt on the surface of the welding part should be removed first.

(3) After the lower hole of the reinforcement cage meets the requirements, the main reinforcement can be spot welded to the hole protection tube or firmly tied to the hole with iron wire to locate the reinforcement cage and prevent movement.

2. Underwater concrete perfusion

After pouring the catheter down, clean the hole a second time to ensure that the thickness of the sediment at the bottom of the hole meets the specification requirements.

a) Check the completeness, verticality and connection tightness of the perfusion catheter, and conduct a water seal test on the catheter on schedule.

b) The bottom of the pipe in the lower entry hole is 300-500mm away from the bottom of the hole, and make a record.

c) Use a ball that matches the diameter of the catheter. Ensure that the initial irrigation volume is sufficient, the burial depth is 0.8 ~ 1.5m, and the burial depth is 2-6m for continuous irrigation. The irrigation should be continuous.

d) Send someone to measure the embedding depth of the catheter and make a record. In the process of pouring concrete, it is necessary to frequently detect the rising height of the concrete surface and check the depth of the buried pipe. When the concrete rises to more than 4m from the bottom of the frame, raise the pipe so that the bottom of the pipe is more than 2m above the bottom of the steel cage frame. The pouring speed can be restored and the normal buried pipe depth can be maintained. When pouring is close to the top of the pile, keep enough pipes The height, using short conduits and other measures, the underwater concrete pouring surface is 1.0~1.5m higher than the design height of the pile top (this height is tentatively determined according to the development of the stratum's fissures, etc., and the specific is determined by the design, supervision and the owner), In order to remove the floating slurry and ensure the quality of the concrete pile. Measure the elevation of the concrete surface before removing the conduit to ensure that the poured concrete reaches the design elevation.

e) The pipe lifting should be kept in the center to prevent it from hitting the steel cage, and the removed pipe should be flushed clean in time.

f) The filling coefficient is controlled at 1.1 when the concrete is poured. According to the test pile concrete filling coefficient is 1.3, but the filling coefficient may be greater than 1.1 when the ground is poured into the concrete, the excess concrete should be approved by Party A and the supervisor.

g) When approaching the top of the pile, due to the decrease of the concrete height in the pipe and the pressure drop to the bottom, the thickness of the mud outside the pipe increases, and the difficulty of pouring occurs, the height of the funnel should be increased.

h) When the concrete pouring is completed, the protective tube should be pulled out at the right time, and the orifice protection should be done to prevent accidents.

i) When pouring concrete, keep concrete specimens in the number required by the design and specifications, and measure the 28d strength.

3. Pile foundation inspection and acceptance

1. 28 days after the completion of the construction of the engineering piles, after the strength meets the design requirements, the large and small strains of the piles shall be tested according to the requirements of the "Technical Specification for Building Pile Foundations" (JGJ94-2008). Each pile shall be tested for small strains, and a certain amount of The piles are tested for large strains. The pile foundation inspection should be carried out by a qualified unit, and the piles for large strains should be jointly determined by the supervisor and the design institute, which must be representative and reflect the real situation of the construction.

2. After the construction of the pile foundation is completed, draw the completion drawing in time, make the pile location plan review, organize the completion data, and ask the quality supervision department to do the completion acceptance of the project pile in time, and deliver the superstructure construction in time.

3. The following completion documents should be submitted for pile foundation completion acceptance: pile position measurement and laying out plan, engineering geological survey, material test record and certificate, construction log, pile construction concealed record, pile position completion layout plan, pile static and dynamic load Test data, sub-project quality inspection and evaluation form, and submit the pile foundation project acceptance record file and the pile foundation project completion acceptance certificate at the same time.

4. Engineering quality assurance technical measures

1) A detailed measurement record must be kept every time the line is laid out, and each row of marker piles must be checked. The record of the measurement and installation results must be signed and approved by the on-site supervision engineer;

2) Make various quality records in detail, and accept inspections by on-site supervision and design departments at any time.

3) Quality inspection and control during construction

(1) The hole forming process includes hole position, hole diameter, hole depth, perpendicularity, sediment thickness and so on.

Hole position quality inspection and control: After the construction site is leveled, the pile position shall be accurately measured and placed according to the design drawings. The pile position error (D/6, and not greater than 100mm) shall be submitted to the supervisor for acceptance in writing. The deviation of the center line of the pile position shall not be greater than 50mm, and the axis control point shall be set at the position where the drilling is not affected, so that the deviation of the hole position can be determined after completion.

Aperture quality inspection and control: According to the performance of the drilling rig and geological conditions, carefully consider the form and size of the drill bit. It must be considered that the diameter of the hole should not be less than the design requirement, and it should not exceed the design requirement to cause waste. The aperture inspection can be inspected by making a hole gauge, according to inspection As a result, the drill diameter is corrected.

Hole depth quality inspection and control: The inspection is combined with the measurement of the rope and the original drilling tool records. The design depth must be guaranteed and the hole must not be artificially terminated in advance.

Verticality inspection and control: Before drilling and opening, check that the moving track of the drilling rig is firm and stable. The four corners of the top plane of the track are required to be at the same elevation. Reliable, light hammer should be used when drilling.

(2) The process of making steel cage includes steel type, diameter and quantity: main reinforcement spacing: spiral reinforcement spacing; stirrup spacing; reinforcement lap length; reinforcement welding condition, reinforcement cage diameter, reinforcement cage length; hanging reinforcement length.

Check whether the steel bar type, diameter, and quantity meet the design requirements. After the inspection is correct, the steel cage can be lowered, and the bending deformation of the steel bar can be checked when the steel cage is lowered.

Steel cage technical indicators: main reinforcement spacing: ±10mm; stirrup spacing or spiral hoops pitch: ±20mm, steel cage diameter: ±10mm; steel cage length: ±50mm; welding adopts single-sided lap welding, welding seam The thickness h is greater than or equal to 0.3d, the width b is greater than or equal to 0.7d; the welding length L is greater than or equal to 10d.

The protective layer of the underwater steel cage is controlled by prefabricated concrete blocks. The setting method: set one every 3-5M, and each pass is welded on the steel bar with stirrup steel passing through the precast concrete block with a diameter of 50mm. The steel cage is evenly distributed. When lowering the steel cage, if the steel cage cannot be lowered to the end. It is necessary to pull out the cage to sweep the holes and lower the steel cage again. After the steel cage is at the design position, during the pouring process, avoid hanging and touching the steel cage when pulling up the conduit, causing the steel cage to float up.

(3) Check the overfilling of concrete. The reason for the overfilling of bored piles is that the drill bit will expand to a certain extent when passing through the soft soil layer. At the same time, when the concrete is injected into the pile hole, a part of it will spread to the soft soil layer. The measures to control the amount of concrete overfilling are mainly to master the drilling speed of each layer of soil. During normal drilling operations, do not stop drilling in the middle to avoid excessive expansion.

(4) Constructors must insist on sampling with a sampler when the concrete is poured near the elevation of the pile top, strictly control the elevation of the pile top, and avoid over- or under-filling.

4) Quality inspection and control after the process is completed

(1) Adhere to the process handover inspection system. Adhere to the principle that the next process is not allowed to be carried out after the previous process is inspected. After the previous process is completed, the work team will first conduct a self-inspection, and the quality personnel will perform full-time inspections. When deemed qualified, the site supervisor will be notified to attend the site for the inspection, and the inspection will be verified and approved. , Before proceeding to the next process.

(2) When design changes or technical verification are proposed due to the owner's reasons, the supervisor must issue a notice to modify or change the technical parameters in writing.

(3) The completion acceptance of the pile foundation project shall be carried out in strict accordance with the "Technical Specification for Building Pile Foundations" JGJ94-2008) and the "Code for Acceptance of Construction Quality of Building Foundation Engineering" and the requirements for bored piles in the "Project Quality Management Record of Hubei Province" Acceptance of cast-in-place pile foundation works.

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