In most geotechnical and environmental drilling, augers are used to drill in the majority of projects. However, the need still arises to perform core sampling for certain geotechnical projects, usually when the presence of bedrock needs to be confirmed. An auger or split spoon will not be able to enter the bedrock so drillers have to use core sampling methods to be able to penetrate and obtain a core sample.
The problem is that geotechnical drillers may not be familiar with the range of diamond core bits available. Choosing them can be risky as they are usually premium products and the wrong choice could be costly, especially if they are burned or worn down prematurely. Core bits made for geotechnical drilling, such as the GeoHawk series are economical and an ideal choice for starting a hole where the type of ground may not be known.
When drilling with augers, you usually do not need a lot of water. As a result, and to reduce costs, the types of pumps used in geotechnical drilling are sometimes not as high performance. When geotechnical drillers need to do core sampling, the water pump must have a high enough pressure to flush out cuttings and cool the bit.
Poor flushing of the cuttings may sometimes result in a bit that balls up with bits of clay or other soil. Most geotechnical drillers do not want to invest in a large, high performance pump when the majority of their work does not require it and so may try to tough it out when they drill bedrock.
Another option is to use a lightweight mud pump that is small enough to be used easily in geotechnical drilling yet offers high performance for projects that require core sampling.
Drilling fluid additives can also play an important role in helping to minimize the wear and tear on equipment, cool the core bits and extend their life. Some additives are abrasive though and the water pump must be able to handle bentonite or other additives.