Details shall be a lot. Check a Soil Testing for Engineers by Lambe.
Bore hole drilling can take many forms:
1)Dry -drive hollow impact or augering
2)Wash borings-using slush(with bentonite) or water
The methods depend on the soil type forecasted.
SPT is obtained when a 140lb. weight is used to hammer a split spoon into the borehole to a depth of 12". The amount of blows that drives the spoon to the 12" is the N value. The hammer must have a free fall of 30".
