repose, _C O_, it may be assumed arbitrarily that the line, _B O_,
bisecting this angle divides this area into two, in one of which the
weight resolves itself wholly into thrust, the other being an area of no
thrust, or wholly of weight bearing on the plane of repose. Calling this
line, _B O_, the haunch line, the thrust in the area, _A O B_, is
measured by its weight divided by the tangent of the angle,
_P Q R_ = [phi], which is the angle of repose; that is, the thrust at
any given point, _R_ = _R Q_ ÷ tan. [phi].

The writer suggests that, in those materials which have steeper angles
of repose than 45°, the area of pressure may be calculated as above, the
thrust being computed, however, as for an angle of 45 degrees.

In calculating the bending moment against a wall or bracing, there is
the weight of the mass multiplied by the distance of its center of
gravity vertically above the toe, or, approximately:

2
Area, _A O B_ × weight per unit × --- height,
3

where _h_ = height,

_W_ = weight per cubic foot of material = 90 lb.,

90° - [phi]
and [beta] = -------------
2

_P_ = pressure per linear foot (vertically),