Should some force be present that tends to push the wall into the earth mass it is
intended to retain—which therefore develops a resistance to slip on the failure plane or
a resistance to the lateral displacement needed to mobilize the active pressure state—a
condition known as passive pressure develops. The lateral earth pressure for which the
wall must be designed increases significantly, as much as 10 times, and requires special
attention. See Fig. 8.9 for a qualitative depiction of the relative lateral displacement