Before the construction of reinforced concrete precast pile, the construction scheme shall be formulated according to the construction drawing design requirements, pile type, soil extrusion during hole forming, geological exploration, pile test and other data.
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① The pile frame is generally composed of chassis, guide rod, lifting equipment, stay rod, etc.
Piling equipment and selection 2.
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Construction steps of driving method: 1.
Treatment of pile head 1.
⑥ The hammer weight shall be selected according to the geological conditions, engineering structure, pile type, density and construction conditions.
Reinforced concrete precast piles include square solid section piles and cylindrical hollow section piles.
The concrete pouring of precast piles should be mechanically mixed and vibrated; During concrete pouring, the correct position of reinforcement shall be strictly ensured, the pile tip shall be aligned with the longitudinal axis, the protective layer on the top of longitudinal reinforcement shall not be too thick, and the distance of reinforcement mesh shall be correct to prevent pile top damage and pile body concrete peeling damage during hammering.
The pile top and pile tip are directly impacted, which is easy to produce high local stress.
Determination of piling sequence 3.
The utility model has the advantages of flexible operation and convenient movement, and is suitable for the construction of various precast piles and cast-in-place piles.
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Determination of piling sequence (1) the piling sequence directly affects the quality and construction speed of pile foundation.
Analysis of common problems in piling construction 6.
The hoisting strength of precast pile reinforced concrete precast pile shall reach 70% of the design strength before hoisting; 100% of the design strength can be reached before transportation and piling.
Piling quality requirements and measurement records 5.
Overview of precast pile reinforced concrete precast pile: Precast in the precast component factory or construction site, and sunk into the soil at the design position with pile sinking equipment.
Formulation of construction scheme: before the construction of reinforced concrete precast pile, the construction scheme shall be formulated according to the construction drawing design requirements, pile type, soil extrusion during hole forming, geological exploration, pile test and other data.
Pipe piles and square piles with a length of less than 10m are fabricated in the prefabrication plant, and longer square piles are fabricated at the piling site.
2、 Fabrication, transportation and stacking of piles 1.
If there is no lifting ring and the design is not specified, the number and position of binding points shall be determined according to the pile length, which shall comply with the principle of minimum lifting bending moment, and can be bound according to the position shown in Figure 2-5.
Site leveling and surrounding obstacle treatment.
② The drop hammer is usually made of cast iron.
1、 Construction preparation 1.
Refer to table 4-3.
The lifting and handling of precast piles must be stable to avoid impact and vibration.
② Select the pile frame and determine the height of the pile frame according to the length of the pile, the height of the pile hammer and construction conditions.
(3) According to the design elevation of the foundation and the specification of the pile, the pile should be driven in the order of depth first and then shallow, large first and then small, long first and then short..
4-5).
The reinforcement configuration of pile top and pile tip (as shown in the figure below) shall be specially treated.
Diesel pile hammer, pile frame and power equipment form a diesel pile driver.
Reinforced concrete precast pile is a widely used pile type in China.
Pile positioning and embedding benchmark.
④ Crawler pile frame (Fig.
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There are two kinds of piercing hammer and gantry hammer, weighing 0.2 ~ 2T.
4-7) is composed of crawler crane as the main engine and pile frame working device.
It uses rope or steel wire rope to lift to a certain height along the pile frame guide rod by the winch through the hook, and then falls freely to hit the pile driving top (as shown in Fig.
① When the center distance of the pile is not more than 4 times the diameter or side length of the pile, it shall be driven symmetrically from the middle to both sides (Fig.
(3) Power plant The power unit of pile driving machinery is determined according to the selected pile hammer.
⑤ Vibratory hammer the vibratory hammer uses mechanical forced vibration and transmits it to the pile through the pile cap to make the pile sink.
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Formwork fabrication of precast piles The formwork can ensure the accurate geometric dimension of the pile and make the pile surface flat and straight; The pile top formwork shall be perpendicular to the pile axis; The pyramid surface of the pile tip is a regular pyramid, and the pile tip is located on the axis of the pile; During the production of bottom formwork, side formwork and overlapping method, the isolation layer shall be painted between the pile surfaces without bonding.
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Precautions during piling 7.
Its main contents include: Determination of construction method, selection of piling machinery, determination of piling sequence, prefabrication and transportation of piles, as well as technical and safety measures in the process of pile sinking.
(2) Pile frame The pile frame is a device that supports the pile body and pile hammer, guides the direction of the pile and maintains the stability of the pile during driving, and ensures that the pile hammer impacts along the required direction.
Quality inspection of precast pile the quality inspection standard of reinforced concrete precast pile shall comply with the provisions in Table 4-2.
3、 Driving method construction driving method, also known as hammering method, is a piling construction method that uses the impact force of the pile hammer falling on the pile top to overcome the resistance of the soil to the pile and make the pile sink to the predetermined depth or reach the bearing layer.
However, there is collision noise and vibration to the surface layer during construction, which limits the construction in urban areas and at night.
Fabrication of reinforcement framework of precast pile Butt welding shall be adopted for the connection of main reinforcement of reinforcement framework; The number of main reinforcement joints configured in the same section shall not exceed 50%; The distance between two joints of the same reinforcement shall be greater than 30d and not less than 500mm.
Pile frame height = pile length + pile hammer height + pulley block height ③ the pile frame is made of steel, including tire type, crawler type, track type, etc.
When air hammer is used, air compressor shall be equipped; When steam hammer is selected, steam boiler and winch shall be equipped.
Preparation of pile cap, cushion lining and pile feeding equipment and machines.
When the laminated method is adopted for production, the pouring of upper pile and adjacent pile can only be carried out after the concrete strength of lower pile and adjacent pile reaches 30% of the design strength.
Hammer driven pile is a common pile sinking method for concrete precast pile.
See Fig.
4-8 (c)), or from the middle to all around (Fig.
See the figure below.
Its characteristics: firm and durable, not affected by groundwater or humid environment, can bear large load, high degree of construction mechanization, fast progress, and can adapt to the construction of different soil layers.
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③ Steam hammer steam hammer is a pile driving machine powered by high-pressure steam or compressed air, including single acting steam hammer and double acting steam hammer (as shown in Figure 4-6).
The allowable deviation of reinforcement framework fabrication shall comply with the provisions in table 2-1.
If the lifting is carried out in advance, measures must be taken and it can only be carried out after passing the check calculation.
According to the requirements of construction drawing design, the position of pile foundation positioning axis shall be accurately measured at the construction site, and obvious signs shall be made.
Piling equipment and selection of piling equipment, including pile hammer, pile frame and power device.
(2) According to the density of piles, the driving sequence is generally divided into three types: driving section by section, driving from the middle to all around and driving from the middle to both sides, as shown in Figure 4-8.
Its main contents include: Determination of construction method, selection of piling machinery, determination of piling sequence, prefabrication and transportation of piles, as well as technical and safety measures in the process of pile sinking.
4-3 for fabrication of reinforced concrete precast pile concrete pouring.
The lifting point shall be stressed at the same time, and the position of the lifting point shall meet the design requirements.
The positioning point and benchmark of pile foundation axis shall be set at a place not affected by pile driving.
④ Diesel hammer diesel pile hammer uses fuel explosion to push the piston back and forth to hammer and pile driving.
4-8 (a)).
4-9 (b)).
2 ~ 4 benchmarks shall be set near the pile driving site to level the site and as the basis for checking the pile penetration depth.
Piling 4.
After pouring, the curing shall be strengthened immediately to prevent cracks due to concrete shrinkage, and the curing time shall not be less than 7d.
(1) Pile hammer ① Selection of pile hammer: drop hammer, steam hammer, diesel pile hammer and vibrating hammer can be selected.
2.
The piling sequence shall be reasonably determined according to the comprehensive consideration of pile density (pile spacing), pile specification, length, pile design elevation, working face layout, construction period requirements, etc.
It has the advantages of fast construction speed, high degree of mechanization and wide application range.
② When the center distance of the pile is greater than 4 times the side length or diameter of the pile, the above two driving methods can be adopted, or one-way driving row by row (Fig.
