Compaction Characteristics of Fiber-Reinforced Soils

Soils reinforced with natural or artificial, randomly oriented fibers are used in various applications such as pavements and embankments. The safe design and construction of projects using fiber-reinforced soils requires the knowledge of their compaction characteristics. Therefore, the present study aims toward (a) the enrichment of the relatively limited available information on the laboratory documentation of the effect of soil properties and fiber type, length and content on the compaction behavior of fiber-reinforced soils and (b) the development of tools for estimating the compaction characteristics of fiber-reinforced soils. Accordingly, five soils ranging from “excellent” to “poor” materials for use in earthwork structures were tested in combination with five types of polypropylene fibers having lengths ranging from 9 to 50 mm. Tests were conducted with standard compactive effort on specimens with fiber contents ranging from 0.5 to 2% by weight of dry soil. The compaction curves of fiber-reinforced soils can be expressed by polynomial functions. Soil type and fiber content have the most significant and measurable effect, respectively, on the compaction characteristics of fiber-reinforced soils. The addition of fibers to the soil results in a decrease of the maximum dry unit weight of compacted soil by up to 10% and in increasing values of its optimum water content by up to 3.6%. Based on the correlations obtained using 212 measurements reported in this study and other research efforts for a wide variety of materials, easy-to-use empirical equations are proposed for the dependable estimation of the compaction characteristics of fiber-reinforced soils with reasonable accuracy for practical applications.