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Elemex Overburden Drilling Systems
Overburden drilling in sensitive ground
As much as 90% of the land surface of the earth is covered with loose, unconsolidated material such as soil, clay, silt, sand, gravel, and boulders that varies in depth from a few inches to hundreds of feet.
Drilling through this so-called overburden is often problematic due to the tendency of the earth to cave in behind the drill bit. This makes it difficult to retrieve the drill string after the hole has been drilled. In practice, the bore hole is often lost before a casing tube can be inserted to support it. The Atlas Copco range of overburden drilling systems represents the latest technology in simultaneous casing advancement.
Casing advancing with DTH is the most productive foundation drilling method available. The harder the ground, the more stones and boulders and the probable rock socket requirements increase the benefits of DTH drilling.
Foundation drilling and underpinning work are frequently carried out where existing foundations are sensitive to any kind of disturbance in their immediate surroundings. In those areas, DTH drilling gives one great challenge - controlling the removal of cuttings from the hole with compressed air. The flow of compressed air needs to be strong enough to transport the cuttings up to the surface, but must not escape into the surrounding ground or remove excessive soil. In clay, air from the DTH drilling can escape to surrounding working foundations and weaken the adhesion between soil and load-bearing elements. This brings a risk for sudden settlement. In sand, excessive flushing can unconsolidate the ground, decreasing the capacity of existing friction piles, which in turn might cause pile buckling and result in the settlement of buildings.
The new and reliable Elemex system for controlled flushing was invented by combining comprehensive field experience and testing with airflow simulation and analysis. Together with some of our most dedicated customers, Atlas Copco has designed this product to take on the most sensitive projects, and Elemex is already proving itself in the field.
The Elemex System
Conventional DTH drilling systems push air straight into the ground, which is a feature derived from rock drilling applications where the rock face needs as much air as possible to be cleaned efficiently.
The unique concept behind the Elemex design is built on redirecting the airflow. Once the air reaches the bit face, it is blown against the extended ring bit walls, which redirect the flow across the face. This way the air pressure is decreased just enough to allow an efficient flushing of the bit face without escaping to the surrounding ground.
The Elemex Movies
Elemex Movie explains the new concept for safer drilling
Shows actual drilling with the Symmetrix Elemex System