Thanks all for the inputs. We did contact some drilling contractors. They thought they can drill into whethered shale, top 5-6m below caly, but not into sound shale , bottom 6m of the caisson.
The rigs are mounted on cranes with 2 kelly bars.
We have a 1.5 to 1.7m diameter caissons to be drilled into approximately 10 m of soft clay and 12 m of Queenston shale with an RQD of 28 to 35 %. Can Kobelco Rig or Link-Belt Rig do the job?
Thanks