The effect of basalt fiber addition on undrained shear strength of clayey soils

As the need for environmentally friendly materials is increasing day by day in geotechnical engineering as in every field, the number of studies on the use of natural and composite environmentally friendly additives to improve the strength behavior of soils is increasing rapidly. Natural and man-made fibers can be used to improve some of the mechanical and physical properties of soils as well as different uses. Studies on the use of natural basalt fibers in soil improvement have been increasing in the literature especially in the last 10 years. In this study, a clayey sample was chosen and this clayey soil was mixed, in different percentages, with 6 mm, 12 mm and 24 mm long basalt fiber. The study covers approximately 200 unconfined compression (UC) tests in total. The soil used in this study was classified as high plasticity clay (CH) according to both Turkish Standard (TS1500) and Unified Soil Classification System (USCS). %1, %2 and %3 basalt fiber added mixtures were prepared and compacted with standard compaction (Proctor) energy. After compaction, four samples were taken from every compacted soil and UC tests were conducted on these samples. In addition, to determine the relationship between macroscopic images and microstructure, Scanning Electron Microscopy (SEM) analyzes were carried out with natural ground samples and samples reinforced with basalt fibers. As a result of the experiments, it was observed that basalt fiber addition increased shear resistance for all lengths and ratios used. It has been shown that the maximum improvement in the shear strength of soils with basalt fiber addition is at the rate of 2% according to dry soil weight. The study showed that basalt fibers can be an alternative to other fiber and additive types to improve soil properties.