Thus, it is noted that the amount of displacement necessary to develop active pressure
can vary, say, for a 20-ft-high (6 m) wall, from less than 1⁄4 in (6 mm), in a dense
cohesionless material, to as much as 5 in (125 mm), in soft clay. Clearly, the backfill
material selected at any location plays a major role in the earth pressure for which a
wall must be designed