What kind of borings typically cannot penetrate hard obstructions like bedrock effectively?

Auger borings are particularly designed for drilling into soil, typically using a helical screw mechanism to lift material out of the hole. However, their design limits their capacity to penetrate harder materials such as bedrock effectively. The cutting action of the auger is less efficient on very hard surfaces, which can lead to issues such as drilling difficulties or equipment damage.

In contrast, other methods like wash borings, which use water or mud to carry cuttings, or dynamic borings, which utilize a hammering action to drive a sampler into the ground, are generally more effective at penetrating through tough obstructions. Test pits, while not designed for drilling, allow for direct observation of subsurface materials and can inform about the presence of bedrock. Overall, auger borings are suited for softer soils and are limited when it comes to hard materials such as bedrock.