1. Material requirements
(1) Precast reinforced concrete pile: the specifications and quality must meet the design requirements and construction specifications, and have the factory certificate.
(2) covered electrode (for pile extension): The model and performance must meet the design requirements and relevant standards. E4303 is usually suitable.
(3) Steel plate (for pile extension): the material and specifications meet the design requirements, and low carbon steel should be adopted.
2. Main machines and tools
Generally, diesel pile driver, electric welding machine, pile cap, pile car, rigging, steel wire rope, steel pad or channel steel and steel ruler shall be provided.
3. Fuck oak parts
(1) The axis and elevation of pile foundation have been determined, and the pre-inspection procedures have been completed after inspection. The axis and elevation control piles of the pile foundation shall be located in a place not affected by piling and protected.
(2) After dealing with high-altitude and underground obstacles. If the use and safety of adjacent buildings or structures are affected, effective measures shall be taken in conjunction with relevant units to deal with them.
(3) The site shall be rolled flat and the drainage shall be smooth. Ensure the movement and stability of the pile driver.
(4) setting out the pile line according to the axis; Nail the pile position with wooden stakes or steel bar heads and mark it with white ash to facilitate construction.
(5) Test pile. Before construction, the number of test piles shall be at least 2. Determine the penetration and check whether the piling equipment, construction technology and technical measures are appropriate.
(6) Select and determine the approach route and piling sequence of the pile driver, formulate the construction plan and make technical disclosure.
4. Operation process
Process flow:
Pile driver in place → lifting precast pile → stabilizing pile → piling → receiving pile → delivering pile → intermediate acceptance → moving pile machine.
(1) Pile driver in position. When the pile driver is in place, the pile position should be aligned to ensure verticality and stability, so as to ensure that it does not tilt or move during construction.
(2) Lifting precast piles. Fasten the steel wire rope and rigging for hanging piles first, then bind the place near the lifting ring at the upper end of the pile with rigging, generally not more than 30cm, and then start the machine to lift the precast pile. Make the pile tip perpendicular to the center of the pile position, slowly put it down and insert it into the soil, and the position should be accurate; Tighten the pile cap or pile hoop at the top of the pile to remove the rigging.
(3) Stabilized piles. After the pile tip is inserted into the pile position, use a small drop hammer of 1 ~ 2 times to make the pile vertically stable after it is buried to a certain depth. Short piles within the range of 10m can be corrected by visual inspection or line hammer. 10m above the pile or driven pile, need to use line hammer or theodolite bidirectional correction, visual inspection is not allowed. The verticality deviation during pile insertion shall not exceed 0.5%.
Before piling, a ruler should be set on the pile side or pile frame for observation and recording during construction.
(4) piling. When piling with a drop hammer or a single hammer, the maximum drop distance of the hammer should not exceed 1 m; When piling with diesel hammer, make the hammer jump normally.
1) A heavy hammer should be used for piling, and the weight of the hammer should be selected according to the engineering geological conditions, pile type, structure, density and construction conditions.
2) According to the foundation design elevation, the piling sequence should be deep first and then shallow; According to the specifications of the pile, it should be large first and then small, long first and then short. Due to the different densities of piles, they can be carried out symmetrically from the middle to two directions or around, or from one side to one direction.
(5) Pile extension:
1) When the pile length is not enough, the welded pile shall be used, and the surface of its embedded parts shall be clean; The gap between the upper and lower sections shall be welded firmly with iron pad; When welding, measures should be taken to reduce weld deformation. Welds shall be welded continuously and completely.
2) Pile extension is generally carried out when it is about 1 m from the ground. The deviation of the center line of the upper and lower piles shall not be greater than 10mm, and the joint shall be bent, and the height shall not be greater than 1‰ of the pile length.
3) Before the pile extension is buried, the exposed iron parts shall be repainted with antirust paint.
(6) sending piles. When the design requires pile delivery, the center line of pile delivery before pile delivery should be consistent with the pile body. If the pile top is uneven, it can be padded with sacks or thick paper. Pile holes left after pile delivery shall be backfilled and compacted immediately.
(7) Inspection and acceptance. Each pile meets the penetration requirements. When the pile tip elevation enters the bearing stratum and approaches the design elevation, or reaches the design elevation, intermediate acceptance shall be conducted. During control, it is generally required that the average penetration of the last three ten hammers is not greater than the specified value, or the pile tip is driven into the design elevation for control, and the construction record is filled in after the design requirements are met. Then move the pile driver to a new pile position. If there is a big difference between piling and requirements, it should be studied and handled by the relevant units.
(8) In the process of piling, the construction shall be suspended in case of any of the following conditions, and the relevant units shall study and deal with it in time.
1) drastic change of permeability;
2) Sudden inclination, displacement or serious rebound of the pile;
3) There are serious cracks or damages on the pile top or pile body.
(9) After all piles are completed, excavate to the design elevation, conduct final acceptance and submit technical data to the general contractor.
(10) If it is difficult to pile in the frozen soil area in winter, the frozen soil should be excavated or thawed first.
5. Quality standards
(1) guarantee project
1) The quality of precast reinforced concrete piles must meet the design requirements and construction specifications, and have the factory certificate.
2) Pile driving elevation or penetration and pile node treatment must meet the design requirements and construction specifications.
(2) Allowable deviation items.
Allowable deviation of precast reinforced concrete piles
Inspection method of allowable deviation (mm) of the project
1 the center position of the pile deviates from the direction of the center line of the foundation beam pile, 100 use theodolite or stay wire and ruler to check.
Along the center line of foundation beam 150
2 The number of piles is 1 ~ 2 or the number of single-row piles is 100.
The number of three piles is 3 ~ 20 D/2.
4 piles with more than 20 side piles D/2
Intermediate reactor d
Note: d refers to the diameter of the pile or the side length of the section.
6. Finished product protection
(1) The pile can only be lifted when it reaches 70% of the design strength, and can only be transported when it reaches 100%.
(2) When lifting and handling piles, the lifting points must meet the design requirements, and should be stable and not damaged.
(3) Pile stacking shall meet the following requirements:
1) The site shall be flat and firm, and uneven settlement is not allowed.
2) The stow-wood and the lifting point are in the same position and should be kept in the same plane.
3) Piles with the same number of piles should be stacked together, and the pile tip should face one end.
4) Multi-layer stow-wood should be aligned up and down, and the bottom stow-wood should be widened appropriately. The number of stacks should not exceed 4.
(4) Properly protect the axis and elevation control piles of the pile foundation, and avoid displacement due to collision and vibration.
(5) If the geological data is found to be inconsistent with the provided data during piling, the construction shall be stopped and the relevant units shall study and deal with it.
(6) When piling on adjacent buildings or bank slopes, effective measures shall be taken jointly with relevant units. Observe at any time during construction.
(7) When excavating the foundation pit after piling, reasonable construction sequence and technical measures should be formulated to prevent the displacement and inclination of piling.
7. Quality problems that should be paid attention to
(1) Precast piles must be ordered in advance. When piling, the strength of precast piles must reach 100% of the design strength, and the maintenance period of one month can be increased before piling.
(2) The pile is broken. It is caused by excessive bending of the pile, insufficient strength, obstacles on the ground, or no fracture of the pile during stacking, lifting and transportation.
(3) The pile top is broken. It is caused by insufficient strength of pile top, insufficient steel mesh, too small distance between main reinforcement and pile top, uneven pile top, improper selection of construction machines and tools, etc.
(4) The pile body is inclined. It is caused by uneven site, uneven chassis of pile driver or vertical pile stabilization, and pile tip touching hard objects underground.
(5) Cracking at the pile extension. The surface of the joint is not clean, the connecting iron pieces are uneven, the welding quality does not meet the requirements, and the upper and lower center lines of the pile extension are not in the same line.
The above is the technical disclosure of precast reinforced concrete piles provided by Zhong Da Consulting for construction personnel. For more knowledge of architectural terminology, please pay attention to the architectural knowledge column of Zhong Da Consulting.
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