Undrained shear strength characteristics of compacted clay reinforced with natural hemp fibers

Abstract

Reinforcing clay with natural fibers is a common practice in various applications, such as the construction of steep slopes, repair of shallow slope failures, improving the performance of landfill covers, strengthening of roadbeds, etc. The reliance on this technique is on the rise as a result of the increasing demand for incorporating sustainable materials in construction. “Hemp” fibers are natural fibers derived from the plant Cannabis Sativa. Industrial Hemp is legally cultivated in a number of countries. Hemp is used in several industries, such as paper, textiles, clothing, biodegradable plastics, construction, body care products, food, medicine, and biofuel, in addition to applications in strengthening concrete and soils. The main objective of this paper is to investigate the potential use of natural Hemp fiber in improving the load response of compacted clays. A laboratory-testing program consisting of 18 unconsolidated undrained triaxial tests was designed for this purpose. Specimens of control clay and of clay mixed with Hemp fibers added at various fiber contents were prepared at a number of water contents and compacted using the standard proctor procedure. Specimens with diameters of 7.15 cm and heights of 14.3 cm were prepared at varying moisture contents (14%, 18%, and 20%) and mixed with fibers of 4 cm length at gravimetric contents ranging from 0.5% to 1.5%. Results show that improvements in shear strength of up to 100% could be realized for the Hemp reinforced specimens. The percent improvement increases with the fiber content up to a threshold value of 1.25% and differs depending on the magnitude of the water content used in compaction in reference to the optimum moisture content of the matrix clay.