Steel pipe piles have the advantages of light weight, good rigidity, strong bearing capacity, easy adjustment of pile length, less soil discharge, little impact on adjacent buildings, simple joint connection, reliable engineering quality, and fast construction speed. However, steel pipe piles also have the disadvantages of high steel consumption and high engineering costs. The piling equipment is more complicated, with high vibration and noise.
1. Structure, type and specifications.
①The pipes of steel pipe piles are generally made of ordinary carbon steel. There are two types of spiral seam steel pipes and straight seam steel pipes. Because of the high rigidity of spiral welded steel pipe, it is more used in engineering.
②As accessories for steel pipe piles, there are mainly pile caps welded to the top of the pile to withstand higher loads, flat steel strips welded to the top of the steel pile and a protective ring used to protect the bottom of the pile, and copper welded to the pile section folder.
2. Choose piling machinery. There are mast type, column foot type, tower type, gantry type, etc., three-point support mast type diesel pile driver is commonly used.
3. The piling sequence. There are two methods: first digging and then stacking, then stacking and then digging. In soft soil areas, the construction method of piling first and then digging is generally adopted.
4. Transportation and hoisting of piles. The steel pipe piles can be transported to the site with a flatbed trailer, unloaded on the side of the pile machine with a crane, stacked according to the pile driving sequence and pile support requirements, and pay attention to the direction. When the site is wide, a single-layer layout should be adopted. Most of the suspended steel pipe piles are tied and lifted. When lifting the pile to the pile position, insert the pile and align the steel pipe pile with the sample pile position previously marked with lime so that the pile position is straight and the pile body is straight.
5. Piling. To prevent damage to the pile head during the hammering process, a special pile cap should be placed on top of the pile head before pile driving. The shock-absorbing wooden mat should be placed on the part directly hit by the hammer.
6. Connect the pile. The pipe diameter should be welded with equal-strength groove welds; if the pipe diameter is changed, flanges and bolts can be used for connection, and the same strength requirements should be met. Steel pipe piles are usually welded.
7. Send piles. When there is a certain gap between the top elevation of the pile and the ground and the pile connection is no longer needed, the pile can be used to drive the pile to the design elevation. The pile barrel should meet the following requirements: the driving resistance should not be too large; the striking energy can be effectively transmitted to the pile driver, it is easy to pull up and can be used continuously.
8. Penetration control. The standard for stopping driving is based on the depth of driving, combined with comprehensive judgments, such as the amount of driving during pile driving, the number of hammer strokes in the last 1 m, and the total number of hammer strokes per pile.
9. Steel pipe pile cutting.
10. Weld the pile cover and connect the pile end to the cap.