Compaction Properties of Soil Composite Fills: Sand, Silt, Clay and Polypropylene Fiber Mixtures

Abstract

A laboratory experimental program including a series of compaction tests on various soil composite fill samples prepared by using sand, silt, clay and polypropylene (PP) fiber at different dry weight proportions was performed. As a result of the tests, the compaction curves were developed for distinct soil composite fill samples so as that the two most crucial and critical compaction engineering design parameters: maximum dry unit weight (γ_d-max) and optimum moisture content (w_opt) were determined. The change in the detected values of γ_d-max and w_opt was investigated by addition of; (i) silt, (ii) clay, (iii) PP fiber, (iv) or selected two of them, (v) or all of them into sand, and thus, the behavior in those two important compaction characteristics (γ_d-max, w_opt), that are decisive properties in design and construction of soil fill infrastructures, was identified for various different soil composite fill samples including different materials studied. It was seen that the γ_d-max decreases, whereas, the w_opt increases as a result of adding silt and/or clay into pure sandy soil. The greater change in the values was observed for clay inclusion compared to that of silt. On the other hand, the inclusion of PP fiber into sandy soil resulted in an increase in the measured values of γ_d-max, while a decrease in the detected values of w_opt. Consequently, the PP fiber served a relative advantage in comparison to the two other materials (silt, clay) by facilitating enhanced compaction properties for the improvement of the characteristics of soil composite fill under loading, and thereby, enabling highly densification or more desirable compaction of the fill not only at larger γ_d-max but also at lower w_opt so as to better comply with common design criteria in practice for the application of compaction procedure in the field during construction as well as to achieve higher bearing capacity (larger load-carrying resistance), and hence, superior performance during operation of the infrastructure built from this soil composite fill.