Difficulties in drilling may occur if cohesionless soils
are drilled below the water table. Possibilities for sand lock or
wedging of cuttings may occur (2). In cases where sands enter
the HSA, water or drilling fluid may be added to the HSA
column to provide hydrostatic balance or special pilot bit
assemblies can be used (see 5.6). Problems may occur in
getting the soil core barrel or pilot bit assembly back to thebottom of the HSA column. Highly saturated sands or liquefiable material may be drawn into the HSA by vacuum created
when the sampler barrel or pilot bit assembly is initially pulled
back through the cutter head of the lead auger assembly from
the bottom of the borehole.