These walls were all at the limit of stability, and the first two are of appreciable height, 10 ft. and 4 ft., respectively.
The figures show that the theory, including the whole of the wall friction, agrees fairly well with experiment, but that the Rankine theory does not thus agree. In both theories, the thrust,
, is supposed to act at one-third of the height from the base of the wall to the surface of the filling; but, in the Rankine theory, this thrust is assumed to act horizontally, whereas, in the other theory, it is supposed to act in a direction making the angle,
, below the normal to the wall.
On combining the thrusts with the weight of the wall, as usual, the resultant strikes the base produced, at
in the first case (Rankine theory), but at
