Injection technology consists of injecting appropriate mixes into the ground to improve its mechanical characteristics.
A possible technical solution is to inject mixtures through the drill pipes (either in progress or during extraction), also using self-drilling bars with continuous threads in case a steel support is needed.
In the case of medium-low permeability soils, up to fine sands, the technique of forced injections is normally used, intersecting the pseudo-impermeable soil with veins and cement reticulations.
In this case, the normal procedure is to:
- drill the hole
- insert a tube a manchette into the hole, with drilled holes at regular intervals covered by rubber check valves
- fill the external cavity with a low strength cement mixture (liner)
- carry out localised pressure injection at each cuff using a packer. The injection mixture lifts the check valve and spreads into the surrounding soil. Normally, in the first phase, a controlled volume of mix is injected to fill the coarser voids, in subsequent phases the injection is refined with more penetrating mixtures
- wash out the inside of the tube, allowing the injections to be repeated late
The use of ARCO self-drilling bar with valves, not only speeds up the pipe insertion operation at the same time as drilling, but also facilitates the insertion of the pipe in loose soils that tend to collapse, or in the presence of back pressure of water in the hole.
Features :
- Self-drilling bar thread machined to leave a smooth interior for optimum packer adhesion.
- Regularly spaced holes are “sealed” with a hot-injected polyurethane resin that ensures the use of drilling fluid pressure up to about 20 Bar. After the rods have been driven into the ground, the resin “plug” is blown off by a pressure stroke at about 40 Bar.
- The injection holes are covered by a rubber check valve and therefore function exactly like a conventional tube a manchette, allowing all the operations described above to be carried out. The check valve is protected by two steel rings pressed onto the tube itself
- A check valve is installed inside the drill bit to prevent water and/or sand from entering when adding bars.
