Perforated piles are mainly used in rock and soil formations to form holes by percussion drilling, and then filling the holes with concrete or steel reinforced concrete, mainly used for forming holes in the rock and soil formations, the hole is made by lifting the punching cone bit to a certain height and then falling down freely. When the hole is made, the cone drill bit is lifted to a certain height to break the rock layer by free-falling impact, and then the slag cylinder is used to pull out the slurry in the hole.
The key points of attention for punched piles
The construction and use of conduit should be in accordance with the following provisions:
1. The wall thickness of the conduit should not be less than 3mm, and the diameter should be 200~250mm; the deviation of the diameter should not be more than 2mm, and the length of the conduit can be determined according to the requirements of the process, and the bottom length of the conduit should not be less than 4m, and the length of the other sections should be 2.53m, and the joints should adopt double-threaded square-button quick couplings. The use of double-threaded square buckle quick connector;
2, the conduit should be used before the test assembly, test pressure, water test pressure can be taken as 0.6 ~ 1.0MPa;
3, each filling should be cleaned inside and outside the conduit.
The quality control of underwater concrete filling should be:
1, start filling concrete, the distance from the bottom of the conduit to the bottom of the hole should be 300-500mm;
2, there should be enough concrete reserves, the conduit should be buried in the concrete below the surface of the concrete should not be less than 1.0m;
3, the conduit is buried in the concrete depth should be 2-6m. It is strictly prohibited to put the conduit out of the concrete filling surface, and should control the speed of lifting the conduit, there should be a person to measure the depth of the conduit and tube inside and outside the height difference between the concrete filling surface, fill in the record of the underwater concrete filling;
4, filling the underwater concrete must be a continuous construction, the filling time of each pile should be controlled according to the initial plate of the first set of concrete time, the filling process should be recorded for the record of failure;
5, should be controlled for the last filling volume should not be less than 1.0m;
5, should be controlled the last filling volume should not be less than 1.0m. The last filling volume should be controlled, and the overfilling height should be 0.8~1.0m, and the concrete strength of the exposed pile top must be guaranteed to reach the design grade after chiseling off the flooding height. After each pile is filled to the top, attention should be paid to the quality of the super height of 800mm, and the contractor should check the elevation. The elevation shall be checked at the design elevation plus 800mm.
6 The water content of mud and specific gravity of mud must be controlled before filling, which is a very important factor affecting the quality of pile foundation.
The concrete for underwater filling should comply with the following regulations:
1, the concrete for underwater filling must have good compatibility, and the ratio should be determined by test; the slump should be 180～220mm; the cement dosage should not be less than 360kg/m3 (the cement dosage can be exempted from this limitation when mixing with fly ash);
2, the sand rate of the underwater filling concrete should be 40%～50%, the sand rate should be 40%～50%, the sand rate should be 40%～50%. Sand rate should be 40% ~ 50%, and it is appropriate to choose the coarse sand; coarse aggregate maximum particle size should be less than 40mm; and should meet, coarse aggregate can be selected pebbles or crushed stone, the aggregate size shall not be greater than 1/3 of the minimum clear distance between the reinforcement bars.
3, underwater concrete should be mixed with additives.
4, the initial amount of concrete must be calculated to determine the initial amount of concrete: generally require the conduit inserted into the pile concrete depth of 1500mm;
5, the depth of the hole must meet the design requirements, the thickness of the slag is strictly prohibited to be greater than 50mm.
6, the initial amount of concrete should be to ensure that all the water in the conduit will be pressurized, and can be the conduit initially buried in the concrete 1 ~ 1.5m deep.
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