As the vertical reinforcement in the foundation, precast pipe piles interact with soil to form a rigid composite foundation. According to the test results and the experience of soft foundation treatment, the quality control of pipe pile comes down to the deviation control of pile position and the quality control of pile body. The following quality control and testing requirements are hereby put forward.
1) material
All incoming materials should pass the test.
2) original ground leveling, measuring and lofting
(1) Before the construction, the site shall be leveled, all the above-ground and underground obstacles within the scope of the construction site shall be removed, and a reference point shall be set near the pipe pile construction site, the position of which shall not be affected by piling, and the pile position where the pipe pile is placed shall be measured from the reference point.
(2) the control pile should be set on one side of the site (about 5m away from the site boundary), and protected, and its position should be checked frequently, usually once a week.
(3) As a large area pipe pile with composite foundation, the deviation of pile position should not exceed 15cm.
(4) During construction, attention should be paid to protecting the released pile location marks.
3) Key points of quality control
(1) Do a good job in commencement (resumption) report, construction measures, technical disclosure, positioning (setting-out) review, material test, material and equipment inspection, concealed engineering records, quality self-inspection, special inspection, re-inspection and handover (handover) data (construction data and dynamic and static test report), and the project supervision department shall formulate specific quality control measures.
(2) Supervisors shall inspect the entry components. The appearance quality and size of pipe piles shall meet the requirements of GBL 3476- 1999. When the component enters the site, it should provide its factory certificate, which should correspond to the factory name, production date and product model marked on the pile end, and the accessories provided should be complete, including: a. Pipe pile structure diagram; B, raw material quality certificate; C, steel bar test report; D, prestressed tensioning records; E, concrete block strength report; F, pile appearance inspection records; G. Test report on mechanical properties of pile body and pile joint: H. Steam curing record; A, product quality problem handling documents.
(3) During construction, the pile position number and pipe pile model should be distinguished, and the length and top elevation of each pile should be recorded in detail.
(4) When sinking the pile, the verticality deviation of the pile body shall not exceed 0.5%, and the construction unit shall be required to equip each pile driver with two qualified theodolite, and the observation shall be carried out at 90 degrees by special personnel.
⑤ When the top of the lower pile is about 1m from the ground, pile sinking will be suspended and pile extension will be implemented. Pile extension adopts steel end plate welding method. Before pile extension and positioning, both end plates shall be cleaned and positioned with positioning plates. If there is a gap at the joint, the wedge-shaped iron sheet shall be used for solid welding, and the groove welding at the splicing place shall be carried out symmetrically in layers (the welding slag shall be removed after each layer of welding is completed, and the next layer shall be welded after passing the quality inspection). The weld shall be continuous and full (meeting the quality of Grade III weld), and the welding slag shall be removed after welding, and the concealed works shall be recorded. The weld quality shall be inspected by the supervisor, and it can continue to sink after 8 minutes of natural cooling. The deviation of the center line of the upper and lower sections of the pile extension shall not be greater than 2mm, and the bending rise of the joint shall not be greater than 0. 1% of the pile section.
⑥ Control the actual pile top elevation according to the pile top elevation and ground elevation determined by the design drawings.
⑦ Due to the large soil squeezing effect of such piles, attention should be paid to controlling the piling sequence and speed to ensure the piling quality. The construction unit shall take necessary preventive measures (such as drilling soil and trenching to prevent extrusion), strengthen the monitoring and protection of buildings, structures and underground pipelines within the influence range of 1.5 times the pile length to prevent damage.
⑧ Supervisors should record the construction supervision in time, fill in the supervision diary and site records, and urge the full-time recording personnel of the construction unit to fill in the construction records in time, which will be checked and signed by the supervisors on duty.
Pet-name ruby when pile sinking is close to the design elevation, don't stop piling prematurely, so as to avoid encountering strong resistance when piling again, which will make pile sinking difficult.
Attending when the pile can't sink to the design elevation, it can be cut after being approved or demonstrated by the design department.
4) Key points of construction supervision
For the static pressure construction of pipe piles, in order to ensure the engineering quality, the technical requirements in the construction process are as follows:
(1) Determine the piling sequence
Understand the geological conditions and soil quality of the site before construction, and determine the reasonable and feasible pile pressing sequence according to the requirements of design documents and construction organization.
② Pile location lofting
According to the coordinate control points and leveling points determined by design documents and on-site technical disclosure, set out the pile position and determine the pile position with theodolite.
③ Pile pressing
Tie the pile with steel rope for single-point lifting, carefully move it into the pile driver, then level the pile driver, start the vertical and horizontal oil cylinders to move the pile driver for adjustment and centering, and check the verticality in two mutually perpendicular directions with theodolite to control the verticality in the soil within 65438 0%. Start the pile driver to start piling, record the piling time and readings of various pressure gauges, and keep continuous piling.
④ Pile extension and welding requirements
When connecting piles, the pile head should be 0.5 ~ 1.0m higher than the ground, and the pile head of the lower pile should be provided with guide wheels to make the lower pile installed in place. The upper pile and the lower pile should be kept straight, and the dislocation deviation should not be greater than 2mm. Before welding piles, the upper and lower surfaces shall be cleaned with iron brush until the groove is brushed with metallic luster. Welding shall be carried out at 6 points symmetrically around the groove, and the upper and lower piles shall be removed after being fixed. Welded pile joints shall be naturally cooled for at least 8min, and water cooling is strictly prohibited.
⑤ Pile sending
Before pile delivery, measure the ground elevation with a level, mark the pile delivery pole, track the pile delivery process and dynamically check the pile delivery depth. The lower end of the pile feeder should be provided with a pile pad with uniform thickness, which is in full-face contact with the pile top. After the pile is delivered to the design elevation, it will take 10 minute, and the settlement per minute will not exceed 2mm, and the pile delivery is completed.
⑥ piling termination standard.
Generally, the bearing layer of friction pile (design elevation of pipe pile) is used as the standard of final pressure of pipe pile. However, when the static pressure increases obviously, it should be terminated in advance, which is calibrated as: for 400PTC pipe piles, the final pressure can be reached when the static pressure is ≥100t. (Note: the static pressure standard required by the design is 60 tons).
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