Drilled casings are one of the most popular piling methods for foundations in urban areas. As a result, contractors are becoming increasingly interested in using down-the-hole (DTH) hammers in foundation construction. At the same time, there are concerns about the use of compressed air that might cause sensitive ground conditions to destabilize due to air leakage or result in damage to surrounding structures due to over-drilling. To meet these challenges, Atlas Copco has developed Elemex, a new drilled casing system that controls compressed air to flush cuttings, yet preserves the integrity of the overburden.
Conventional systems push air straight into the ground, a necessary feature in rock drilling applications where the rock face needs as much air as possible to be cleaned efficiently. However, in overburden drilling conditions, flushing should be just intense enough to get cuttings out of the hole.
The Elemex system redirects air flow, minimizing the amount of air escaping to the surrounding ground. Once air reaches the bit face, it is blown against the extended ring bit walls, which redirects the flow across the face. As a result, air pressure is decreased just enough to allow the bit face to be efficiently flushed, while impact to the surrounding ground is significantly reduced.
Because the Elemex system controls air flushing intensity, no special operator’s training is needed. Results of extensive field testing of the Elemex system revealed no variations in ground water levels and no settlement of surrounding buildings. Contractors can achieve maximum productivity with DTH drilling with the added benefit of a safer work site.