What Are the Most Common Piles Causes?

Hanging foot pile refers to a pile construction quality accident where the concrete at the bottom of the pile is suspended or mixed with mud and sand to form a soft layer. One of the common quality problems in the construction of immersed pipe cast-in-place piles.

Hanging foot pile refers to a pile construction quality accident where the concrete at the bottom of the pile is suspended or mixed with mud and sand to form a soft layer. One of the common quality problems in the construction of immersed pipe cast-in-place piles.

The reason is that the pile tip valve is not opened when the pipe is pulled out, and the concrete drops to a certain height, which is not dense and has gaps; or the prefabricated concrete pile tip used is of poor quality and insufficient strength, and the edge of the sinking pipe is crushed. The tip is squeezed into the tube, the impact and vibration are not enough when it is pulled out, and it is not pressed out, but it is dropped and stuck at a certain height.

The quality of prefabricated pile tip is poor. When sinking the pipe, the pile tip was squeezed and damaged due to insufficient strength and entered the pile pipe. When the pile tip was pulled out, it could not be pushed out until the pipe was pulled to a certain height, but it did not fall to the original level, forming " Hanging feet "; or after the tip of the pile is crushed and crushed, mud and sand are squeezed into the pile pipe from the damage and mixed with the concrete at the bottom of the pile to form a soft and weak layer.

When the length of the pile is longer, the tip of the valve flap cannot be opened by being surrounded by the surrounding soil.

The concrete grading is unreasonable and the workability is poor. When the pipe is pulled out, the concrete refuses to fall, causing no concrete or a small amount under the tip of the pile, which is generally called "soft pile". Similar to this kind of failure, you can use high-flow concrete Such as pressing the tube to prevent accidents.

Generally, it is a horizontal crack that runs through the entire section. The cause of the broken pile is basically the same as the diameter reduction. The main reasons are engineering geology, construction technology, concrete quality, design pile distance, and excavation collision. Especially in soft soil areas, when the pile density is relatively large, adjacent piles squeeze horizontally to each other, and often a fracture surface is formed at the bottom of the reinforced cage. The severity of the broken pile is greater than the shrinkage.

In theory, manual digging is the easiest pile type to control the construction quality, but the following construction quality should be guaranteed in actual construction:

Water on the bottom of the pile. If the water at the bottom of the pile can be removed manually, it must be removed and dried. If there is underground seepage and artificial drying is not possible, mechanical precipitation must be used, otherwise the pile bottom concrete will easily cause segregation. Because general digging piles are end bearing piles, accidents caused by pile bottom concrete segregation are difficult to handle.

Cast-in-place concrete. For piles with a short pile length, the slide method can be used for pouring instead of the direct pouring method. It is strictly forbidden to directly dump a long pile, otherwise it is very easy to cause concrete segregation, air trapping, and mud trapping; it is not recommended to use the slide method, and it is also easy to cause concrete segregation, air trapping, and mud trapping; the pipe method shall be used to send slurry , Using mechanical vibration while sending ^[1]

The construction of bored cast-in-situ piles includes procedures such as mud wall protection, underwater hole formation, underwater cage, hole clearing, and underwater infusion. Each procedure is more or less light or heavy, and some defects will occur.

The drilling is inclined. During the drilling process, encountering underground obstacles such as lone stones caused the drill bar to deflect, the degree of pile inclination was different, and the impact on the bearing capacity of the foundation pile was different. Since this type of accident cannot be measured by means of quality inspection of the foundation pile, Inspection of verticality is particularly important, especially for large diameter bored piles.

Collapse. It is easy to cause defects such as broken piles, sediment, and abrupt hole diameter.

The filling coefficient is too large. The general design requires the filling coefficient of concrete pouring to be between 1.05 and 1.25. However, due to the pore forming process and geological conditions, the filling coefficient exceeds 1.3 and even reaches 1.6 or greater. This is an abnormal construction phenomenon. This results in waste of materials and the disadvantages of inconsistent stiffness of the left and right piles.

The shrinkage of the pile body, the inclusion of mud, broken piles, and segregation are all quality problems of the pile body, which have a great impact on the bearing capacity of the foundation pile.

sediment at the bottom of the hole.

Quality accident caused by improper initial irrigation method.

Concrete pile head scum ^[2] .