How to construct steel pipe piles

In my country's coastal and inland plain areas, the soil is often very thick (50-60 meters deep) soft soil layer. When conventional reinforced concrete and prestressed concrete piles are difficult to adapt to, steel pipe piles are often used to reinforce the foundation.

Steel pipe piles have the advantages of light weight, good rigidity, high bearing capacity, easy adjustment of pile length and joint connection, safe and reliable project quality, small amount of soil discharge, little impact on adjacent buildings, and fast construction development speed. However, steel pipe piles also have shortcomings such as the large amount of steel, high project cost, complicated pile driving equipment, large impact of vibration and noise, poor pile protection and management, and easy corrosion.
1. Structure, type and specifications. The pipe material of steel pipe piles is generally made of ordinary carbon steel, including spiral seam steel pipes and straight seam steel pipes. Due to the high stiffness of spiral seam steel pipes, they are often used as accessories for steel pipe piles in engineering. They are mainly used to bear the upper load. The pile cover welded on the top of the pile, the flat steel strip welded on the top of the steel pipe pile, the protective ring used to protect the bottom of the pile, and the copper clamp used for welding the pile sections.

2. Selection of piling machinery. There are many types such as column foot type, mast type, tower type, gantry type, etc. Three-point support mast type (crawler walking) diesel pile driver is more commonly used.
3. Piling sequence, there are two methods: digging first and then piling, and first driving piling and then digging. In soft soil areas, the construction method of piling first and then digging can generally be adopted.
4. Transportation and hoisting of piles. Steel pipe piles can be transported to the construction site by a flatbed trailer and unloaded on the side of the pile driver using a crane. After that, according to the development sequence of piling and the supporting technical requirements and stacking of piles, it is advisable to adopt a single-layer arrangement when the site is wide, and pay attention to the direction. When hoisting steel pipe piles, wait until the pile position is reached for pile insertion. Align the steel pipe piles with the sample pile positions marked out with lime in advance to ensure that the pile position is correct and the pile body is straight.
5. Piling. In order to prevent the pile head from being damaged during hammering, before piling, a special pile cap must be placed on the top of the pile head, and a vibration-absorbing wooden pad should be placed in the part that will directly and economically withstand actual hammering.
6. Take piles. If the pipe diameter remains unchanged, groove welds of equal strength should be welded. If the pipe diameter changes, flanges and bolts can be used to connect. The same strength requirements should be met. Steel pipe piles are generally welded.

7. Send piles. When there is a certain gap between the pile top elevation and the ground, and the pile connection is no longer needed, the pile delivery tube can be used to drive the pile to the design elevation. The pile delivery tube should meet the following requirements: the driving resistance is not too large, and the impact energy can be effectively transmitted The piles driven are easy to pull out and can be used continuously and for a long time.
8. Penetration control. The specification for stopping driving is mainly based on the penetration depth, combined with the comprehensive determination of the penetration amount during pile driving, the number of hammer blows in the last 1m, and the total number of hammer blows for each pile; cutting of steel pipe piles, welding of pile caps, pile ends station connection.