Bored piles are used, as a rule, to strengthen the foundations of buildings undergoing reconstruction. Their widespread use is due to several factors. First of all, injection piles have small dimensions along with special technical capabilities for use. These structures allow working in rooms with a height of up to two meters, punching holes through masonry, reinforced concrete, concrete with a diameter of up to three hundred millimeters and a depth of up to fifty meters. A small-sized installation can carry out drilling indoors with an external power unit.
Bored piles are varieties. One of the types is the structure used in new buildings to strengthen walls in the ground and fences for vertical slopes. They are called "injection anchors." In this case, special anchor installations are used.
Depending on the ground conditions, one or another tool for drilling is selected. Bored piles have a length and diameter in accordance with a given bearing capacity of the piles or the force perceived by the anchor.
Drilling in unstable and flooded soils is carried out by flushing the well with a mud or using casing pipes.
The device of bored piles is carried out using reinforcement. Moreover, in accordance with the nature of the current load, reinforcement is carried out for the entire length or in the upper part. The length of the reinforcement section is determined in accordance with the height of the room. Armokark set after, before, or during pressure testing of the well.
The construction of pile foundations involves the presence of fixing components that center the piles in the wells and provide the necessary thickness of the protective layer in concrete. With the help of welded joints, the reinforcement cages are connected in length and, accordingly, the reinforcement is equally strong. On the contour of the pile at a distance not less than the diameter of the rod itself are the rods. Typically, the cross-sectional area of longitudinal reinforcement is not less than 0.5% of the cross-sectional area of the pile itself.
To strengthen the bearing characteristics of piles, due to compaction of the soil, pressure testing of the walls of the well and freshly laid concrete is carried out.
Crimping can be done in various ways.
So, they can pump an additional portion of the solution with a pump through a tampon, which is expanded at the wellhead, in the wellhead or in the existing base. In this case, the crimping is performed under a pressure of 0.2-0.3 MPa for two minutes. If it is not possible to maintain pressure during this time, the work is carried out again after an hour or two until the desired result is obtained.
Crimping can also be carried out in a specific section of the piles or in the borehole face through the augers.
Work is carried out using electric discharge technology. In this case, electrohydrodynamic pressure testing of the borehole bottom or walls is performed.
Another method is "re-injection." In this case, they pressurize a specific area on the pile shaft using an injection fracture of the primary concrete infusion.
Bored piles are arranged in accordance with a specific technological cycle, consisting of several operations:
- Drilling.
- The organization of the reinforced frame.
- Filling a well with concrete (fine-grained) mixture.
- Pressure testing of the fresh mixture.
It should be said that the reinforced cage is allowed to be installed both after and before filling the well with the mixture.
Recently, there has been a constant improvement of the equipment used, technological operations and techniques, which, undoubtedly, is aimed at improving the quality and bearing capacity of piles.