Вrilling piles

For limited urban conditions, the impact method of pile sinking is unacceptable in most cases. The use of the pile driving method is associated with significant technical difficulties, and in sandy soils, even when leading a static load, it is usually not enough to sink the pile to the design mark.

From the second half of the 20th century, and especially actively already in our time, rammed borehole injection piles have become widespread. They differ from bored piles in that the concrete is fed into the well, which is made with a preliminary excavation of the soil, with additional crimping. Concreting under pressure provides a good contact with the soil at the end of the pile and allows to achieve the design strength even with small indentations in the bearing foundation.

During the production of injection piles, the well is drilled with a hollow auger, the blades of which are filled with soil during drilling. After reaching the design mark, drilling is stopped. Holes are opened in the lower part of the auger, through which concrete is fed under a pressure of 0.2 – 0.4 MPa, while the auger with soil plays the role of a packer. In the process of gradually lifting the auger, the vacated cavity is filled with concrete. The reinforcing frame is inserted into fresh, already compacted concrete.

Thus, among driven piles, the most effective for driving unstable soils are borehole injection piles. When making them, there is no need to use casing pipes or clay mortar. Pressing fresh concrete helps to improve the conditions of joint work of the soil and the body of the pile.