In order to help relevant personnel understand pile foundation pouring, Zhong Da consulted and compiled relevant information, and the basic situation is as follows:
Pile foundation is a deep foundation (see figure) composed of piles and caps connecting the top of piles, or a single pile foundation connected by columns and piles, referred to as pile foundation. If the pile body is completely buried in the soil and the bottom of the pile cap is in contact with the soil, it is called low pile cap pile foundation; If the upper part of the pile body is exposed to the ground and the bottom of the cap is exposed to the ground, it is called high cap pile foundation. Building pile foundation is usually a low pile cap pile foundation. Pile foundation is widely used in high-rise buildings.
In order to help the construction enterprise personnel understand the pile foundation pouring, Zhong Da consulted and compiled relevant information, and the basic situation is as follows:
Pile foundation pouring construction technology:
(1) Underwater concrete pouring conduit shall meet the following requirements:
A the inner wall of steel pipe is smooth and smooth, with consistent inner diameter and tight joints. The diameter of the conduit is adapted to the pile diameter and the concrete pouring speed, which can be 20 ~ 30cm. The length of the pipe joint should be 2m in the middle section and 4m in the bottom section, and the pipe with the length of 1m should be used under the funnel.
B before using the catheter, try to install and test the pressure, and number and mark the scale from bottom to top. The axis deviation of the assembled conduit should not exceed 0.5% of the hole depth, and should not be greater than 10cm, and the nut of the connecting bolt should be on it when connecting; Test the hydrostatic pressure at the bottom of the hole at a pressure of 1.5 times.
The length of the conduit is determined by the depth of the hole and the height of the workbench. The distance between the bottom of the funnel and the upper opening of the borehole is greater than the length of a section of intermediate conduit. Cone looper should be added at the flange of conduit joint, and there should be no flange at the lower end of the bottom conduit. Spiral threaded joints can be used when conditions permit, but there must be a locking device.
D the conduit shall be located in the center of the borehole, and the axis deviation of the conduit after assembly shall not exceed 0.5% of the borehole depth and shall not be greater than 10cm. Before pouring concrete, conduct lifting test. The capacity of lifting equipment for conduit hoisting should be compatible with the total weight and friction of all conduits filled with concrete, and there should be a certain safety reserve.
(2) Installation of conduit; According to the requirements of construction technology, a conduit with an inner diameter of 32.5cm and a thickness of 4mm is adopted, which should have sufficient rigidity and strength to meet the construction requirements. The conduit is connected with the conduit by screws, sealed with "○" rubber sealing ring, and subjected to water leakage test. Fill the assembled conduit with 70% water, then connect the air duct, and input the calculated wind pressure, which is 6.2 atmospheres (i.e. 58 1.9kpa). The test pressure shall not be lower than the maximum pressure dP that may be borne when pouring concrete. The specific calculation process is as follows:
(5) Before pouring pile foundation concrete, the working face should be cleaned, and mud prevention and drainage measures should be taken. Fill in the "Engineering Inspection Sheet" for checking the hole of bored pile and reinforcing cage as required, and fill in the "Underwater Concrete Pouring Record" when pouring.
(6) The initial stock of concrete shall meet the requirement that after the first batch of concrete is put into the hole, the depth of the conduit buried in concrete shall not be less than 1m and not more than 3m; When the pile is long, the depth of the conduit buried in concrete can be appropriately increased. When the concrete surface is close to the steel skeleton, slow down the pouring speed, and after the concrete surface enters the steel skeleton to a certain depth, properly lift the conduit to make the steel skeleton have a certain depth at the lower opening of the conduit.
(7) When pouring pile foundation concrete, it must be poured continuously, without stopping halfway, and the longest time shall not exceed 8h. If necessary, a retarding water reducer approved by the supervision engineer can be added. The buried depth of the conduit in concrete is 2-6m, and the distance from the concrete surface to the top of the casing is often detected, and the conduit length is compared, and the conduit is often pulled out. The pouring height of underwater concrete is over 1.0m higher than the designed pile top elevation. After concrete pouring, the liners below the ground and at the top of the pile should be pulled out before the initial setting of concrete.
(8) In the process of concrete pouring, the slump of concrete is often detected and recorded. Each pile shall be equipped with at least two groups of concrete test blocks for testing the compressive strength of underwater concrete.
(9) In the process of grouting, the mud overflowing from the hole should be discharged to a suitable place for treatment, so as to prevent the river and the surrounding environment from being polluted.
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