DESIGN AND BEHAVIOR OF SOIL-FABRIC-AGGREGATE SYSTEMS

Abstract

The use of fabrics made of man-made fibers is having an increasing impact on the construction techniques used for and the technology of soil-aggregate systems. Certain fabrics, when placed between a soft subgrade soil and a layer of aggregate, will significantly improve the performance of the system. The fabrics are especially effective in improving the performance of those systems that have very soft subgrades and hence high deflections and a high tendency toward rutting. Although it can be demonstrated that fabrics can significantly improve the performance of soil-aggregate (S-A) systems that have soft subgrades, there are no reliable procedures availaibe to guide in the thickness design of these systems or in the selection of the appropriate fabric affects the behavior and performance of a soil-fabric-aggregate (S-F-A) system and describes the development of a design procedure for S-F-A systems that use MIRAFI-140 fabric. The four basic mechanisms by which fabrics affect the behavior and performance of S-F-A systems include (a) confinement and reinforcement of the aggregate layer, (b) confinement of the subgrade soil (c) separation of the soil and the aggregate layers, and (d) introduction of filter medium to facilitate drainage. Repeated plate-load tests on small- and large-scale S-A and S-F-A systems in a laboratory setting are described. The results of these tests are analyzed by using elementary theories and techniques, and a design procedure for S-F-A systems that use the MIRAFI-140 fabric is developed. An example of a typical design curve for S-A and and S-F-A systems is included.