Why must the buried depth of the pipe be 2-6 meters when the pile hole is poured into the concrete?

Why must the burial depth be 2-6 meters

Question added: the meaning of 2-6M. The first irrigation is not a catheter with a depth of 70-80 cm. Then I think it is not enough to bury 1M in the irrigation.

Just checked the pile foundation specification mentioned in 6.3.30, one pouring is embedded in the concrete pouring surface not less than 0.8m;

The buried pipe 2-6m refers to the depth control of the buried pipe during the pouring process; however, I think it is not realistic because many pile foundations are now commercial concrete. When 1.2m piles go up by one car, the concrete surface rises 8m. It is possible to dismantle the pipe so many times in one car; once the construction is buried, the pipe is almost 20 meters. I think 2-6m is the requirement for the self-mixed concrete in the past, and the strength of the current pipe is also high, so the depth of the buried pipe can be enlarged.

The buried depth of the catheter should be controlled at 3-6 meters. The main reason is that your buried pipe is too deep. If the temperature of the pouring pile is not lower than -5 degrees in winter, there is no problem in waiting for 2 hours. The catheter is moved back and forth for 10 minutes. The main part of the pouring pile during the pouring process is the buried depth of the catheter, and the mass of the concrete. To prevent holes, so as not to empty the catheter!

In the case of pouring concrete, the mud-wall-protected cast-in-situ pile mainly controls the initial irrigation and the buried depth of the duct.