THE DESIGN OF REINFORCED SOIL WALLS BY COMPACTION THEORY

Currently, two design philosophies are available for the design of reinforced soil walls. The first, known as the tie-back structure hypothesis, models lateral earth pressures using simple active pressure theories. This presupposes that the top of the wall rotates actively outwards about its toe. It is further assumed that failure in the soil occurs along a planar surface. The second and later approach, known as the coherent gravity structure hypothesis, assumes lateral earth pressures to vary from the "at rest" condition at the top of the wall to the active condition further down the wall. This is coupled with the assumption of a logarithmic spiral failure surface. To achieve compatibility between these two assumptions there is the further assumption that the base of the wall rotates actively outwards about its top. This assumption is compared with field observations which clearly indicate wall rotation about the toe. Since neither of these theories quantifies the effects of compaction, a theory is introduced to relate compaction-induced earth pressures to basic compaction plant characteristics. Results from this compaction theory are then compared with those from several case histories. Finally, a comparison is drawn between the three design methods, and comments are made on the resulting design implications. (Author/TRRL)