Environmental Engineering Reference
In-Depth Information
tion methods. The predominant mineral in the rock specimen and the degree of weather-
ing decomposition are controlling factors.
Measurement Criteria
The following criteria are used to establish hardness values:
1.
Moh's system of relative hardness for various minerals (see
Table 5.4).
2.
Field tests for engineering classification (see
Table 5.20).
3.
“Total” hardness concept of Deere (1970) based on laboratory tests and devel-
oped as an aid in the design of tunnel boring machines (TBMs). Ranges in total
hardness of common rock types are given in Figure 3.1.
4.
Testing methods for total hardness
(Tarkoy, 1975):
FIGURE 3.1
Range of “total” hardness for common rock types. Data are not all inclusive, but represent the range for rocks
tested in the Rock Mechanics Laboratory, University of Illinois, over recent years.
H
R
Schmidt hardness;
H
A
abrasion test hardness. (From Tarkoy, P. J.,
Proceedings of the 15th Symposium on Rock Mechanics,
Custer State
Park, South Dakota, ASCE, New York, 1975, pp. 415-447. With permission.) (a) Inset: Schmidt hammer.
