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.
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.
When geotechnical crews perform excavations, it is crucial that engineers determine a safe slope angle, especially in situations where the ground is clay, silt or other fine-grained soils. A simple and quick test that estimates the undrained shear strength of saturated soils is the vane shear test.