CONTROLLED YIELDING OF THE LATERAL BOUNDARIES OF SOIL RETAINING STRUCTURES

Lateral expansion of conventional or reinforced soil backfills is necessary to establish and maintain the minimum lateral stresses on soil retaining structures. Laboratory studies are detailed which show that these minimum conditions can be achieved by the provision of a compressible layer on the rear of the wall or facing psanel units. For unreinforced backfill this will mean achieving lateral forces on the real of the wall at or near "active" values. For reinforced backfills, the lateral forces can be less than "active" values; the amound being dependent on the number and stiffness of the reinforcing layers. For incremental construction, the resulting distribution of lateral stresses is shown to differ significantly from the hydrostatis forms derived on the basis of "at rest" or "active" conditions. The distribution can be identified as conforming most closely with rotation about the top and translation. Also it is suggested that, by using this technique, the minimum lateral stresses can be achieved during the construction period, thus post-construction deformations of the soil and the reinforcements, if present, ca be minimized. This is particularly important when relatively extensible polymeric materials are used to reinforce soils. Further reductions in post-construction deformations may be achieved with use of this technique by surcharging the backfill for a period, in order to pre-strain the reinforcements.