Quality problems and prevention measures for bored pile.1

- Dec 13, 2019-

Bored piles have the advantages like low construction noise, low vibration, pile length, and diameter can be changed freely according to design requirements, the pile tip can reliably enter the holding layer, and the single pile has a large bearing capacity. 

However, from the beginning of drilling to the end of pile formation, due to various factors, it is easy to cause quality problems or even quality accidents, so quality control has become a difficult point in construction.

bored pile

1.The steel cage floats up

The reinforced skeleton that has been sunk to the design depth position, during the pouring process, the skeleton position is higher than the original design position, which is commonly referred to as a "floating cage".

1.1 Cause Analysis

1) The inner diameter of the steel cage cage is small with the distance between the duct and the coarse aggregate size is too large. The overlapped welding head of the main reinforcement is not welded flat. During the process of duct lifting and sinking, the flange is hung with a steel cage.

2) During the installation of the reinforcing steel, the skeleton is distorted, the stirrup deformed, the welding is dislodged, or the pipe is inclined, so that the steel bar is in close contact with the outer wall of the pipe.

3) Sometimes, due to the failure of the machine, stop when pouring the concrete, the concrete between the duct and the steel bar has condensed, and the steel bar is taken out when the pipe is lifted.

4) The pouring concrete speed is too fast, the concrete surface rises to the bottom of the reinforced cage, resulting in upward "buoyancy", which causes the reinforced cage to float up.

1.2 How to solve?

1) The “floating cage” appears as soon as the pouring is started, mainly because there is a phenomenon of hanging between the catheter and the cage; the pouring should be stopped immediately, and the catheter should be shaken up and down repeatedly or rotated in one direction.

2) During the pouring process, as the catheter is pulled out, the cage floats, but the plantar surface does not move. It is also due to the phenomenon of hanging between the catheter and the cage. The catheter should be repeatedly shaken and moved up and down to cut off the two. contact.

3) During the pouring process, as the surface rises and the cage floats, the amount and speed of pouring should be controlled.