According to this technology, casing is advanced by rotary head thorough the casing clamps and simultaneously jacked. Casing consists of a series of rigidly connected sections. As the casing is advanced, the soil inside it is removed by an auger and then a new section is added. Auger is fixed to the end of the Kelly-bar that expands as the borehole is deepened.
Process starts with the advancing drilling of the borehole with casing with a reinforced tip (core bit). The core bit serves for drilling of soil and concrete of primary piles for construction of secant bored piles. The casing in inserted into the soil with a rotary head or the casing oscillator to a depth of 1,5-2,0 m. Further by using a telescopic Kelly bar with a short auger the casing is cleared from soil.
Operations on borehole drilling and soil extraction are repeated every 1.5-2.0 m of casing penetration. When the project depth drilling tool is extracted from the casing, drilling cuttings are removed from the hole, reinforcement cage is installed and fixed and the borehole is filled with tremie method.