Bürkle Mole Drill Head, Gravel Drill, Interchangeable Head for Soil Samplers, Iron/Steel, 5350-1040

Gravel presents a different challenge to a soil sampler than sand or clay, because individual stones can block the drill head rather than simply being displaced like finer material. The Mole drill head for gravel is designed to deal with these stones in the ground, featuring slightly curved, angled blades that pull themselves downwards as they rotate, trapping stones between their flanks. A drill head without this shape would have to repeatedly re-engage at precisely these points without making any real progress.

How the blades grip the gravel

The slanted, slightly curved blades of the gravel auger work differently to the straight flanks of sand and clay drill heads. As the drill bit is turned in, the blades pull themselves deeper into the ground rather than simply applying pressure from above, and larger stones are trapped between the flanks whilst finer material remains inside the drill bit. This means that when the bit is withdrawn, a sample is brought to the surface that contains both the coarse and finer material of the gravel substrate.

Not all gravel is the same

Just how fine or coarse a gravelly soil actually is varies considerably from site to site, ranging from fine gravel to fist-sized stones. The gravel auger covers the typical range of gravel soils in which individual stones can be trapped without blocking the auger. If individual stones are significantly larger than the auger head itself, using a different head beforehand helps to clear them out of the way before continuing with the gravel auger.

Use with the ‘Mole’ handle

Like all heads in the range, the gravel drill bit is an interchangeable attachment for the ‘Mole’ handle with shaft and does not function independently. The handle is 750 millimetres long; for greater drilling depths, a 100-centimetre extension (5350-1010) can be fitted.

Typical applications

The gravel auger is the ideal choice for soils where a few to many stones are to be expected, including:

• Sampling in gravelly, stony soils
• Site investigation on areas with a crushed stone or gravel subsoil
• Sampling in and around gravel pits
• Preliminary surveys for road construction on gravelly subsoil

When individual stones are in the way

If a single, larger stone blocks the borehole before the gravel drill bit is even used, the drill head’s stone catcher removes it first. If the ground is also hard and encrusted, rather than just loose and gravelly, the Riverside drill head with its protruding drill blades works more reliably. If the ground contains only a few coarse grains rather than proper gravel, the coarse sand drill head is usually sufficient.

Material and storage

Like all heads in the series, the gravel drill head is made of iron/steel and contains no electronics or battery. Contact with stones and coarse material causes mechanical wear to the material, but this does not affect the head’s function provided it is cleaned after use. A dry place at room temperature is sufficient for storage between uses.

Technical details

Contents

• Mole drill head, gravel drill

The Mole handle with shaft is not included in the scope of delivery and must be provided separately or ordered at the same time.

Service and procurement

For sites with larger individual stones in the gravel soil, LT Laborhandel can, on request, supply the gravel auger together with the stone catcher, so that obstacles can be cleared out of the way in advance, rather than having to laboriously work around them during sampling. If you have any questions regarding the nature of the gravel at your own site, please contact LT Laborhandel directly for assistance.