Page 110 - Moving the Earth_ The Workbook of Excavation

ROCK, SOIL, AND MUD

3.4 THE WORK

FIGURE 3.2B Classification of soils and soil-aggregate mixtures. (Courtesy of Portland Cement Association.)

FIGURE 3.3 Rock types.

Adhesion is the sticking of soil to the digging parts. It may increase the friction load substan-
tially in wet work.
Cohesion is resistance to tearing apart. Firm or hard materials may split readily along bedding
or cleavage planes so that they can be dug rather easily from the proper direction. Relatively soft
clay banks may be very difficult to dig because of strong and uniform cohesion. A tough forma-
tion lacking planes of weakness is described as “tight.”