A drilling method for deep site investigations through compacted soil and bedrock.

Rotary drilling is a method of borehole drilling which achieves greater depths in dense gravel or bedrock than Cable Percussion Drilling.

It utilises a powered rotary cutting head on a rotating shaft to form deep observation boreholes or gather representative soil and rock core samples. Lubrication by way of air, water, or drilling mud is used to cool the cutting head.

There are two types of rotary boring: open-hole and core drilling.

With open-hole drilling, the cutting head grinds the material to chips, and therefore the recovered material is highly disturbed and mixed with the drilling lubricant.

It is an efficient method where rapid drilling is required to greater depths but a detailed record of the recovered material is not required. It is also suitable for rapid establishment of monitoring wells.

Core drilling, involving wire-line, double or triple-tube core barrels, is typically done with diamond/tungsten-tipped bits, if samples are to be recovered.

The drill bit cuts an annulus around the core, which then preserves core inside the shaft of the drill rod. Core drilling provides less disturbed and less contaminated sampling of stiff soil and rock.

Triple-core barrels, featuring a non-rotating inner barrel, provide improved recovery of rock core.

It is ideal for bedrock or hard soils, retrieving all sample types from disturbed to class 1 undisturbed in hard soils/bedrock.

These drilling rigs are also able to conduct Standard Penetration Testing during borehole advancement.

Upon completion, boreholes serve for soakaway testing or instrumentation installation for monitoring ground movement, groundwater levels, water quality, and gas.