in the second case. [Figs. 4] to 7 present a striking object lesson as to the inaccuracy of the Rankine method of treating experimental retaining walls.
In the next experiments, however, referring to a retaining structure consisting of two boards, hinged at the top, [Fig. 8], and backed by sand level at the top, the Rankine theory is applicable when the board,
, is placed either at or below the plane of rupture, on the left of
. The thrust on
is then assumed to act horizontally, at
above