Heat shrinkable polyethylene film can also be used for protection.
Before butt joint, the surface of the upper and lower plates shall be cleaned, and the groove shall show metallic luster.
During pile sinking, the supervisor and the constructor of the construction unit shall carefully make relevant records.
The pile sinking methods include hammer driving pile and static pressure pile（ 1) Drawing review and disclosure the project department shall organize the design unit, construction unit, survey unit and supervision unit to conduct joint review and disclosure of drawings.
The welding should be carried out symmetrically around the pile.
Avoid the collision of earthwork equipment with engineering piles, the brutal construction of pile cutting units, the extrusion of piles caused by non layered excavation of soft soil foundation, and the adverse impact of construction processes such as site vehicles, material processing and storage yard on piles（ 4) Suspend pile driving.
When the site conditions permit, it should be stacked in one or two layers.
Site elevation, positioning coordinates, pile top elevation, pile length range and other parameters shall be carefully checked.
After welding, the hammering can be continued only after natural cooling.
Between the pile feeder and the pile head, 1 ~ 2 layers of gunny bags or cardboard and other liners shall be set, filled with elastic liners, and the compacted thickness shall not be less than 60mm.
Micro expansive concrete can be used to fill the core or flexible waterproof materials can be precoated on the inner wall.
Party A’s engineer and Supervision Engineer shall recheck the positioning coordinates of each building and handle the site elevation survey handover with the construction unit（ 2) Prepare the special construction scheme.
Welding is a common way of pile connection.
Generally, the number of test piles shall not be less than 3（ 4) After the acceptance of materials and the arrival of pile foundation materials in the storage yard, the supervisor and the construction unit shall conduct sampling inspection on the size and appearance of the pile.
During pile connection, the upper and lower pile sections shall be kept straight, and the dislocation deviation shall not be greater than 2mm.
When one side is adjacent to the building, it can be driven from the adjacent building to the other direction.
For piles with soil depth ≥ 8m, the number of re compaction can be 2 ~ 3 times; For the pile with soil depth less than 8m, the number of re compaction can be 3 ~ 5 times.
Dense pile groups are generally driven symmetrically from the middle to two directions or around, or from one side to a single direction.
The pile sinking sequence has an obvious impact on the construction quality and progress.
When mechanical quick thread pile connection is adopted: the joints at both ends of the upper and lower pile sections shall be cleaned and coated with grease; The special joint taper shall be used for centering, and the upper and lower section piles shall be aligned for tightening connection; After locking, the plates at both ends shall have a gap of 1 ~ 2mm.
The natural cooling time shall not be less than 8min.
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▲ in the construction record of precast piles in the specification, each pile shall be driven continuously, and the effective pile length of the last section during static pressure pile sinking shall not be less than 5m.
The pile position deviation of driven pile shall meet the specification requirements.
The autocratic steel pile feeder shall be used for pile delivery, and the engineering pile shall not be used as pile feeder.
When mechanical engagement joint is used for pile connection: the upper and lower joint plates shall be cleaned; When the local foundation soil and groundwater contain medium or above corrosive medium, the surface of pile end plate shall be fully coated with asphalt coating（ 2) When the pile is driven by hammer, the control of pile termination hammering shall comply with the following provisions: when the pile end is located in the general soil layer, the design elevation of the pile end shall be mainly controlled, supplemented by the penetration.
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The number of pile extension shall be minimized, and the joint shall be located in the non polluted soil layer.
03 construction management: the verticality of precast pile shall be corrected before pile sinking, that is, the pile hammer, pile cap or pile feeder coincides with the center line of pile body.
（ 3) Static pressure pile sinking and final pressure condition the final pressure condition of static pressure pile is that the penetration depth reaches the design requirements and meets the final pressure value specified in the design.
For pipe piles constructed in winter, relevant measures shall be prepared according to the main frozen soil performance indexes of the foundation.
When driving piles by hammering, the driving depth shall not be greater than 2.0m.
The pile sinking sequence is unreasonable, and the pile driver goes back and forth repeatedly in the site, which will not only affect the on-site alternate construction, but also damage the completed piles.
When the pile end reaches hard and hard plastic cohesive soil, silt above medium density, sandy soil, gravel soil and weathered rock, the penetration control shall be the main, supplemented by the pile end elevation.
The pressure stabilizing and pile pressing force shall not be less than the final pressure, and the time for stable pile pressing shall be 5 ~ 10s.
In case of sharp change of penetration, sudden inclination of pile body, serious crack or breakage of pile body, obvious uplift of ground, floating of adjacent piles or excessive displacement, pile driving shall be suspended and discussed with relevant units in time“ Due to the change of geological conditions, the difficulty of construction of “underground” project changes..
Precast pile is a common pile foundation form on the project site, which has the characteristics of simple construction, low technical difficulty and short construction period.
During static pressure pile driving, when the effective pile length of most piles on the site is less than or equal to 15m or the bearing layer at the pile end is weathered soft rock, and re pressing is required, the pile driving depth should not exceed 1.5m; When the verticality deviation of the pile is less than 1% and the effective pile length of the pile is greater than 15m, the driving depth of the static pressure pile shall not exceed 8m（ 2) When the core filled prestressed concrete hollow pile at the bottom of the pile is embedded in strongly weathered rock, completely weathered rock and unsaturated soil that are easy to soften with water, it is recommended to take effective anti-seepage measures within about 2m above the pile end after pile sinking.
The pile type parameters, the requirements for the pile end to enter the bearing stratum, the value of the vertical bearing capacity of a single pile, the requirements for pile test, etc.
During pile extension, the supervising engineer shall stand by and make acceptance records.
When the pile extension is in place and corrected, it is not allowed to use a sledgehammer to knock laterally.
The construction site shall be equipped with pile verticality observation instruments, and the observer shall measure the verticality of the pile at any time.
01 preparation of precast pile before construction is a widely used foundation form at present.
When the prestressed concrete hollow pile is stacked in layers, the pile with outer diameter of 500 ~ 600mm shall not exceed 4 layers, and the pile with outer diameter of 300 ~ 400mm shall not exceed 5 layers（ According to article 7.2.3 of technical code for building pile foundation (jgj94-2008), the concealed acceptance of precast pile mainly includes the following two parts: pile extension acceptance and acceptance before pile sinking（ 1) The connection of pile extension can adopt welding, flange connection or mechanical quick connection (threaded type and meshing type).
is the top priority of project management.
The precast pile stacking site shall be flat and solid, with good drainage conditions, and it is not suitable to be transported multiple times at the construction site.
After the upper and lower pile sections are fixed, the guide hoop should be removed and then welded in layers; The number of welding layers shall not be less than 2, and the weld shall be continuous and full.
When stacking, rectangular wood or sleeper should be used for support and cushion, and angular metal components shall not be used.
It is strictly prohibited to use water for cooling or immediately after welding.
The construction unit shall prepare the special construction scheme according to the specifications and design requirements, and clarify the pile sinking sequence, pile connection method, suspension of pile sinking conditions, coordination requirements for foundation pit excavation, prevention and control of soil compaction and other measures.
When the pile joint is located in the polluted soil layer, the steel parts connected to the pile shall be coated with anti-corrosion and wear-resistant coating or the thickness of the steel parts shall be increased, and the corrosion allowance shall not be less than 2mm.
According to the design elevation of the foundation, it is better to be deep first and then shallow; According to the specification of pile, it is better to be large first and then small（ 3) Before the construction of test pile foundation, it is recommended to conduct test pile to determine relevant parameters.
The number of continuous re compaction of final compaction shall be determined according to pile length, geological conditions and other factors.
The deviation of perpendicularity during pile insertion shall not exceed 0.5%.
When the penetration has reached the design requirements but the pile end elevation has not been reached, continue to hammer for 3 times, and confirm that the penetration of 10 blows per array is not greater than the value specified in the design.
It is generally divided into concrete precast pile and prestressed concrete pipe pile.
If the cushion cap is buried deeply or there is a thick flow plastic muddy soil layer, the “soil excavation before pile driving” can be adopted to strictly control the additional load around the pile（ 1) The prefabricated pile shall be delivered to the design elevation as far as possible.
▲ negative case: unreasonable control of pile top elevation (3) pile sinking protection measures shall be taken in time after pile sinking to protect the completed pile from disturbance and damage.
shall be clarified.
