Geogrid reinforced retaining structures and slopes

Abstract

Research has brought about the development of retaining structures using geogrid soil reinforcement and masonry face units. In this type of system, geogrid is embedded within the mortared or unmortared joint of the masonry wall. In mortared masonry units, the possibility exists of the embedment having an adverse effect on the flexural bond strength and compressive strength of the joint. In unmortared masonry units, the pull-out resistance of the geogrid within the unmortared joint is of interest along with the strains produced within the geogrid itself. As a result, the behaviour of the joint was examined through testing performed in an experimental program Concrete masonry blcok couplets were constructed using three types of geogrid and one type geotextile at 25, 50 and 100 percent embedment. The couplets were tested to determine flexural bond strength, compressive strength, compressive strength and pull-out resistance. The results indicate the flexural bond strength and compressive strength are not adversely affected by embedment of geogrid or geotextile. The maximum pull-out resistance was obtained for geogrid at 100 percent embedment. The pull-out resistance of geogrid used in connection with unmortared Wallstones was also examined. A small prototype wall was constructed in the laboratory. Three tests were performed varying the number of Wallstones on top of the geogrid. As can be expected, the pull-out resistance increased as normal load on the joint containing geogrid was increased. Soil backfill was then placed behind the Wallstone Wall The pull-out strength increased with the presence of the backfill. The addition of a ligh surcharge to the backfill resulted in a further increase in pull-out resistance. In addition to the above tests, Wallstone couplets with three types of geogrid and one type of geotextile were constructed at 50 and 100 percent embedment. The normal load was varied on the couplets with the results indicating that adequate pull-out resistance is provided by the unmortared joints. A description of the procedure used in applying strain gauges to geogrid is also provided