Investigation of the effect of basalt fiber and cement additives on geotechnical properties of weak soils

Soil improvement may be a suitable method for strengthening weak soils in terms of being more economical and not requiring advanced technology compared to deep foundation applications. In the soil stabilization, it is aimed to make the soil more dense and to increase the bearing capacity and the shear strength of the soil as well as to eliminate the risk of liquefaction. In this context, the use of additives in improving the geotechnical properties of soils is frequently found in engineering applications. Although cement is generally used as an additive in soil improvement, scientific researches on the availability of different additives are still in progress. One of the examples that can be given to these additives, which can be used in soil improvement, is the basalt fiber which is classified as natural fiber and has high tensile strength. Although the raw material is cheap and the cost of production is low due to the basalt rocks which are commonly found in the earth's crust, the studies on the use of environmentally friendly basalt fibers in geotechnical applications have only begun in the last few years. In this study, after determining the physical properties and the soil class of the natural liquefiable sandy soils; compaction, California Bearing Ratio (CBR), direct shear box and unconfined compression tests have been conducted on the prepared specimens with the proportions of 2,5%, 5%, 10% cement and 1%, 2%, 3%, 4% basalt fiber (by weight of dry soil). When the test results were examined, it was observed that the cement and basalt fiber additive caused an increase in the shear strength, bearing capacity and compressive strength of the sandy soil. It was concluded that the ratio of cement is 10% and fiber ratio is 3% in the specimen with maximum shear strength. While the compressive strength reached to its maximum value at the end of 28 days of curing in the specimen with 10% cement and 4% fiber, it has been determined that the sample having the highest bearing capacity has 10% cement and 1% fiber additive. As a result, it has been revealed that the basalt fiber, to be used with cement, may be considered as an alternative to other additives in soil improvement applications on soils that may be subject to severe deformations by loss of strength and bearing capacity under static and seismic loads. Keywords: Basalt fiber, Cement, Liquefaction, Soil improvement