he drained residual strength of cohesive soils in the Bromhead
ring shear apparatus. These procedures are termed: (1) single
stage, (2) preshearing, (3) multistage, and (4) the proposed . 'flush"
procedure. The main factor affecting the residual strength measured
in the Bromhead ring shear apparatus is the magnitude of
wall friction that is developed along the inner and outer circumferences
of the specimen. The farther the top porous stone settles
into the specimen container, the more wall friction that is developed
on the shear plane and the higher the measured residual
strength. In addition. during shear a small amount of soil is
usually extruded between the top porous stone and the walls of
the specimen container. As the top porolls stone settles into the
specimen container, the possibility of the extruded soil becoming
trapped between the container and porous stone becomes greater.
This may also lead to an increase in shearing resistance as the
top platen settles.