Taking subsoil core sample using hollow drill worm contg. sampler - with foil tube corrugated on bush, locking sampler by repeated dropping, drilling at low then higher speed

摘要

The method is for obtaining a ground sample (6) from non-binding water carrying sub-soil strata using a hollow drilling worm (13) containing a sample core taking unit (1) suspended (via 2,3) from a cable (4) and comprising a foil tube (7) of which the lower end is pulled over the upper end of a bush (8) so that it is folded in corrugations. When the worm is at the required level, the unit (1) is locked (2; 10,11) in position therein by alternately raising and dropping it. Drilling is then carried out in two successive stages, i.e. with high pressure and torque at a speed below 20 rpm followed by a speed above 60 rpm to move the strongly compacted material on the worm windings (14). The unit is then withdrawn whilst supplying water thereto to compensate pressure.