Four steps to improve the construction quality of PHC pipe pile

September 5, 2025

I. ACCESS CONTROL

The strength of the pipe pile shall reach 100% of the design value before it can be transported to the site.
The product qualification certificate, appearance and external dimensions shall be checked when entering the site.
1. Appearance: no honeycomb, exposed concrete, cracks, uniform color, no cracks at the top of the pile.
2. Shape: pile diameter ±5mm, pipe wall thickness ±5mm, pile tip center line less than 2mm, top surface flatness less than 10mm, pile top bending less than 1/1000L (L is the pile length).
3. The pile body shall have the marking of pipe pile, manufacturing date and pipe pile number.

II. SITE Piling

The two-point method is used to lift the pipe pile, or the hook can be used at both ends of the plate, and the angle between the rope and the pile body is greater than 45°.
During loading, unloading and lifting, it should be moved horizontally. Throwing, colliding and rolling should be strictly prohibited.
The pile storage site must be flat and firm, with drainage measures.
The lowermost layer of the pipe pile shall be set with a support block according to the two support points method, and the support points shall be on the same horizontal plane with a spacing of 2/3L (L is the pile length).
The pipe diameter of 400mm can be stacked 4 layers, the pipe diameter of 500mm and 600mm can be stacked 3 layers, each layer needs to be set with two support points.
Pile according to different specifications and models of piles.

III. Pre-construction preparations

The release of the axis shall be introduced by the control points of the national triangle network and shall be verified for many times. The position of the control points of the axis on the construction site shall not be affected by the sinking of piles, and the number shall not be less than two.
Check whether there are buildings near the construction site, poles and wires in the air, and pipelines underground, and take the following measures.
1. Dig anti-seismic ditches. The width 0.5~0.8m and depth of the ditches shall be determined according to the soil conditions and the self-supporting slope.
2. Set up bagged sand well, with a diameter of 70~80㎜, spacing 1~1.5m and depth of 10~12m.
Determine the order of piling according to the density of piles and the relationship with surrounding buildings.
1. If the piles are dense and far away from the building, it is advisable to proceed from the middle to the surrounding areas when the site is open.
2. If the piles are dense, the site is long and narrow, and the ends are far away from the building, it is advisable to proceed from the middle to the ends.
3. If the piles are dense and close to the building, it is advisable to start from the adjacent side of the building and proceed from near to far.
4. According to the specifications of the pile, it is advisable to start with large and then small, long and short.
Check whether all parts of the pile driver are running normally and whether the connection is firm. The pressure gauge must be tested and approved by the authority before it can be used.
The installation site of the pile driver shall be treated according to the construction requirements. The site shall be leveled and the ground shall reach the average bearing capacity of 35kPa.
Check the pile position, the deviation shall not be greater than 20mm.
Mark the length of the pipe pile in meters.

IV. Quality control

Vertical deviation of pipe pile lifting and insertion into the ground in section 1 shall not be greater than 0.5%. The verticality of the pile shall be monitored by setting up a theodolite from front and side at 90° direction with measuring instruments. If necessary, it is advisable to pull out and reinsert the pile. It is strictly prohibited to move the pile machine to correct the deviation.
When the pipe pile is extended, it should be carried out when the pile head is 0.5~1m above the ground.
When the pile is connected, the upper and lower piles should be kept straight, and the misalignment should not be greater than 2mm.
Clean the joint surface and bevel when connecting. If the gap between the pile section is large, fill it with iron plate and weld it firmly. The gap between the joint surface shall not be greater than 2mm.
During welding, start with symmetrical spot welding at points 4-6. Two certified welders shall then perform symmetrical welding. The number of welding layers must be no less than two: the first layer requires a 3.2mm diameter electrode for root pass, followed by a 4mm or 5mm diameter electrode for the second layer. The inner layer must be thoroughly cleaned before applying the outer layer. The weld thickness should exceed the groove by 1mm, with full and continuous weld seams free from porosity, slag, or cracks.
After welding, the rest time is more than 5min, and it is strictly prohibited to use cold water cooling or welding pressure.
During the pile pressing process, the pressure, verticality of the pile, the interval time between pile joints, the connection quality of the pile and the depth of pile pressing should be checked. For important projects, 10% of the welds of the pile joints should be inspected.
Do not weld when the temperature is lower than 0℃, rain, snow and other reliable measures to ensure welding quality.
Each pile should be constructed continuously in one time to minimize downtime.
If the pile spacing is less than 3 times the pile diameter, the pile must be drilled in a jump.
Control the elevation of the pile top, calculate the height of the pile according to the design elevation of the pile top, and mark it on the pile driver.
Protect the pile head above the ground. The pile should be cut with a cutting machine. It is strictly prohibited to hit or forcibly pull the pile with a hammer.