3.2.2.4 Schmidt Hammer
This method is limited to very soft or very hard rocks [ISRM Brown (Ed) 1981]. The principle of the test is the determination of the amount of energy absorbed into a rock when impacted upon by a set amount of energy (0.74Nm). The orientation of the hammer is critical because values can be affected if the hammer is incorrectly used.
Carter and Sneddon [1977] found that the method was quick to perform, more than twice as many tests could be performed when compared to the standard UCS tests. They concluded that the results correlated well with UCS and could therefore be used as a quick alternative to a laboratory test. It was also suggested that the method was not as direct as the point load test because it does not fracture the sample. Aggistalis et al [1996] found a high positive correlation between the Schmidt hammer results (r=0.86) and the degree of weathering.