Table 4D–6 Hardness and unconfined compressive strength 4D–3 Table 4E–1 Line survey data 4E–1 Table 4E–2 Joint set spacing egories 4E–1 Part 631 National Engineering Handbook Engineering Classifiion of Rock Materials Chapter 4 (210–VI–NEH, Amend. 55, January 2012) 4–v. Figures Figure 4–1 Stairstep erosion pattern in flatlying rocks of variable 4–15 resistance ...