High Pressure Injection drilling (HPI) in special foundation engineering requires the use of especially designed drill rigs to carry out tasks such as sealing dams; drilling deep foundations for buildings; and underpinning foundation supports.
HPI drilling was the main point of focus when KLEMM Bohrtechnik developed the KR 720—a drill rig which is particularly suited for drilling vertical, comparatively large, drill depths of up to 25 m in a single pass.
This rig offers a wide spectrum of applications, including compaction grouting for improving the load bearing capacity of the ground and rock grouting for filling fissures, cracks, and cavities. The KR 720 can also be configured to carry out tasks such as water extraction, deep hole hammer micro-piling (DTH) or continuous flight auger drilling.
The parallel kinematics of the boom and the 2-fold backstay cylinder kinematics are optimal for carrying out such operations. Not only is it easy to move the mast into the drill rig transport position, but adjusting the angle of the mast, and the longitudinal and transverse spacing of the drilling axis can be carried out with ease and accuracy. Initial drilling points can be easily reached by hydraulically adjusting the height of the mast.
For HPI operations the base mast can be combined with a gear feed system and lattice mast extensions which are individually removable. This allows the base mast to have a long, uninterrupted feed. The mast can also be fitted with bezels, sleds for flushing heads, safety rails and injection hose diverters.
The KLEMM KH 14SK – rotary head with mandrel – can grip and drive HDI rods with a diameter of up to 114 mm. The KLEMM KH 12SK is suitable for larger diameters of up to 133 mm.
A modified hydraulic excavator combined with an operator cabin make up the base of the KR 720. The 360° rotatable upper carriage enables drilling positions to be reached all around the pivot point. In order to have both a compact transport position and a high level of stability, KLEMM made the undercarriage of the rig base is telescopic. The electro-hydraulics and electronic controls on the KR 720 were developed especially for this model.