The construction process of prestressed pipe piles is as follows: measurement and positioning → positioning of pile driver → counterweighting of pile driver → feeding pile to the front of pile driver → installing pile tip → lifting pile with crane and aligning pile position → adjusting verticality of pile and pile frame → applying pressure → rechecking verticality and continuing to apply pressure → connecting piles → measuring penetration → displacement of pile driver → static load test of pile foundation → acceptance of pile foundation.
(1) The engineering geological data is complete, the pile foundation design drawings have been reviewed, and the special construction plan for the pile foundation has been approved.
(2) The high-altitude, ground, and underground obstacles within the scope of the pile foundation have been removed, the site has been leveled and compacted, the construction machinery can operate normally on the site, and drainage measures have been implemented during the rainy season.
(3) According to the actual situation on site, vibration isolation measures have been taken for buildings (structures) near the piling site.
(4) The pile foundation axis and leveling base point control piles have been set up, and the confirmation and handover procedures have been completed after review.
(5) The pile position has been verified and marked with wooden piles, short steel bars, or white lime lines.
(6) The entry and exit routes for the piling equipment and the pile foundation construction sequence have been selected and determined.
(7) The appearance quality of the pipe piles has been checked, and the piles have been stacked near the pile driver according to the plan layout. Unqualified pipe piles have been marked and arranged to be removed from the site.
(8) The pile foundation construction equipment has been installed, and the pile foundation construction machinery and lifting tools have been checked to be intact. Water and electricity pipelines have been laid. (9) Before the construction of pipe piles and rotary excavation piles, test piles should be carried out according to the design requirements. The number of test piles should meet the design requirements, generally not less than 2. Manually excavated piles are generally not required to carry out test excavation, but when the geological conditions are complex and there are clear design requirements, test excavation can be carried out, and large-scale excavation can be carried out after inspection and confirmation by the survey and design units.
(1) The pile driving records to be provided to the designer include the following items: number of hammer blows per meter, number of hammer blows every 30cm in the last 2~3m, total number of hammer blows, drop height, pile verticality, pile deviation, welding time, pile segment composition, welding operation, etc., to determine the construction pile driver, pile hammer and pile hammer performance, liner and its parameters, check geological data, and cooperate with the design work.
(2) The piles shall be selected according to the various types of piles and their location, pile length, inclination, bearing layer conditions, and terrain and geomorphic conditions. The number shall be confirmed by the designer and the project department. Large-scale construction can only be carried out after the pile driving process report is approved by the project department and the supervisor.
When two-point lifting is used, the pile should be delivered to within 3m of the pile driver lifting position. During lifting, the pile should be protected from damage and breakage. The concrete precast pile can only be lifted when its concrete strength reaches 100%.
(1) When sinking piles, the verticality of the pile body should be controlled to meet the requirements, and the pile hammer, pile cap, and pile body center line should be in a straight line to avoid eccentric impact and damage to the pile head during pile sinking.
(2) When the pile is 50cm into the soil, the verticality of the pile and the horizontality of the platform should be corrected. When the pile is about 3m into the ground, the verticality of the pile body should be measured again to ensure that the vertical deviation of the pile in both the vertical and horizontal directions does not exceed 0.5%.
(3) According to the design and specifications, the verticality of the pile body should be controlled within 1%L (L is the pile length), and the verticality of the first section of the pile should be controlled within 0.5%L.
(4) The concrete strength of the precast concrete pile should reach 100% of the strength design value before pile sinking can be carried out.
(1) The pile tip should be made according to the design requirements. The site should be welded and installed after inspection and acceptance by the supervisor. To prevent the pile head from being damaged during hammering, a pile cap should be placed on the top of the pile head before pile driving, and a hardwood vibration-damping wooden pad should be placed on it.
(2) The pile foundation should be constructed in the order of flow and driven backward. When the pile group foundation or the distance between the pile centers is less than 3.5 times the pile diameter, the skip-driving method should be adopted.
(3) If water or mud enters the pile pipe during the sinking process, concrete should be poured into the pipe about 1.5m high before sinking the pipe.
(4) When driving the pile, the verticality of the pile frame guide rod and the pile should be checked and corrected, and the hammer, pile cap, and pile should be kept on the same axis. The penetration depth of the pile should meet the design and specification requirements. When the pile top is 60~80cm above the ground, stop hammering and connect the piles. When the pile top elevation is a certain distance from the ground and the pile connection is not adopted, the pile driver can be used to drive the pile to the design elevation.
(5) The last three hammering operations must be strictly controlled, and the penetration rate of each operation must meet the design requirements. (6) Principle of stopping hammering: When the pile end is located in the general soil layer, the pile end design elevation is the main control condition, and the penetration rate is the reference basis. When the pile end is located in other soil layers, the opposite is true.
(7) If there is a serious deviation, tilt, broken pile, etc., the design unit should be informed in time for processing.
(1) Reinforced concrete prestressed pipe piles should be connected by welding. The welding rods used for pile connection should meet the design requirements. Generally, E43 series welding rods are used. The welds at the pile connection must be accepted and qualified (if necessary, flaw detection should be carried out) before construction can continue.
(2) Pile connection is generally carried out about 1m above the ground. The centerline deviation of the upper and lower piles should be less than 10mm, and the node bending arrow height should not be greater than 1% of the pile length.
(1) The standard for stopping pile driving shall be based on the determined stop hammer standard. After the pile driving is completed, the pile delivery hole shall be filled and covered in time.
(2) If any of the following situations occur during pile driving, the on-site supervisor and project engineer shall be notified in time, and the geological survey and design units shall be contacted. The treatment plan shall be determined after research by all parties: 1) The penetration rate changes dramatically, or the final penetration rate is too large or too small relative to the design value or the test pile data; 2) The pile body suddenly tilts, deflects, or there is severe rebound when struck; 3) The pile top is severely broken or cracks appear in the pile body; 4) The pile frame shakes violently; 5) Other abnormal situations.
(3) Under normal circumstances, pile driving construction should be carried out continuously, and the rest time between the same piles should not exceed 30 minutes.
For broken piles, the treatment plan shall be determined on-site in conjunction with the design unit.
Sequence of pile driving
(1) It shall be carried out by the approved pile foundation construction plan.
(2) When the building area is large and the number of piles is large, the foundation piles can be divided into several sections, and pile driving shall be carried out separately within the range of each section.
(3) When constructing multiple pile platforms, the requirements of the pile foundation construction plan shall be met, and it is strictly forbidden to drive piles from both sides to the middle.
(1) Before construction, the corresponding pipe piles should be cleaned, and the height of the core filling concrete should meet the specific design requirements of each location.
(2) Pile cutting: The allowable deviation of the pile top elevation is ±50mm. For piles with a diameter of L≥800mm, the height of the pile top entering the pedestal should not be less than 100mm; for piles with a diameter of 250≤L＜800, the height of the pile top entering the pedestal should not be less than 50mm. Electric pile saws should be used for cutting the pile heads. Manual chiseling is strictly prohibited.
(3) Pile connection: When the pile top is lower than the design elevation by more than 2 times the pile diameter, the short pile cut on-site can be used for pile connection. When the pile head is 0.5~1.0m above the ground, the hammering should be stopped, and the pile should be extended. When connecting the piles, the mud and rust on the joints should be cleaned until the metallic luster is exposed, and then the special pile connection fixture should be fastened, and the pile to be connected should be hoisted into the fixture. The connection deviation should not be greater than 2mm. After welding, the welding slag should be removed, and the weld quality should be inspected and accepted by the supervision unit before construction can continue.
(1) The quality of prestressed pipe piles must meet the design and relevant requirements. Before construction, the supervision unit shall organize an appearance and data inspection of the pipe piles entering the site. Unqualified piles shall be marked and removed from the site promptly.
(2) During the construction of pipe piles, the axis, verticality, pressure, penetration, pile connection interval time, and appearance quality of the pile connection welds shall be checked. If necessary, the pile connection welds shall be inspected according to local regulations.
(3) The treatment of the joints of the piles, the pile head dowels, and other nodes shall meet the design requirements and construction specifications.
(4) During the waterproofing of the base plate, the waterproofing method of the pile head shall meet the design and relevant specifications.
(5) The bearing capacity inspection method and inspection quantity of reinforced concrete precast piles shall meet the design and relevant standard requirements. Generally, the static load test method is used for inspection.
(1) The prefabricated pipe piles that have been delivered should be stacked neatly. The stacking height should not exceed 4 layers. Each layer should be supported by square wood. The upper and lower support points should be on the same vertical line, and attention should be paid to prevent collision with construction machinery.
(2) The pile heads after construction should be protected from vehicle collision and rolling to prevent damage to the pile heads.
(3) During the piling process, a pile cap should be installed to prevent damage to the pile heads.
(1) Unqualified piles are not marked and removed from the site, but are used in pile foundation construction.
(2) The concrete strength of the finished pipe piles does not reach 100% of the design strength, but pile foundation construction is carried out.
(3) Obstacles around the pile position and underground are not removed before pile foundation construction, the straightness of the pile body does not meet the requirements, the upper and lower piles are not on the same axis, and fractures or lateral displacements occur during pile pressing. (4) The welding quality of the welds during pile connection does not meet the requirements, and construction continues without natural cooling after welding.
—Thanks—
Bored cast-in-place piles have the advantages of low construction noise, and low vibration, pile length…
Bored cast-in-place piles have the advantages of low construction noise, and low vibration,…
The four major construction technologies are dry hole forming technology, slurry static pressure technology, casing…
Soil nail support is a new type of retaining structure developed in recent years for…
Pile Foundation Classification and Construction Principles 1. Classification According to Load-Bearing Piles ① Friction type…
Steel sheet pile cofferdams are suitable for basic projects such as sandy soil, gravel soil,…
