What Does Cable Percussion Boring Mean?
Cable percussion boring is a common drilling method used for geotechnical site investigations. This drilling method allows the installation of casing inside the borehole allowing for deep boreholes. It is the most convenient and common method of intrusive geotechnical investigation and depending on ground conditions and access to the site, boreholes up to 60m depth can be drilled.
Different sample types can be retrieved using this method such as cohesive disturbed samples, granular disturbed samples, undisturbed samples, piston samples, and split barrel sampler (used for SPT – standard penetration test).
Trenchlesspedia Explains Cable Percussion Boring
The cable percussion boring rig consists of a winch and a derrick that can be folded down and towed to and from the site. For cohesive soils, the borehole is drilled using a clay cutter, and for non-cohesive soils, a shell is used.
A sampler is driven by percussion using weights to advance the borehole into the ground. The soil sample can be retrieved by bringing up the sampler. The borehole sides are supported using casing as the borehole proceeds.
For very hard ground that is difficult to penetrate or for obstructions such as boulders, a chiseling tool can be used.
Tests such as SPT, borehole vane test, and falling or rising head test can be carried out within the borehole.