Evaluation of Mechanical Behavior of Reinforced Expansive Soil

Abstract

Expansive soils undergo swell upon wetting and shrink upon drying, and the roads and the buildings constructed on these foundation soils often undergo differential settlements after certain period of time, which ultimately results in the collapse / failure of these structures. It is unavoidable in certain situations to use such types of soils, so, in this scenario, It is critical to improve these soils' performance properties. Different researchers used different additives such as jute fiber, palm fiber, lime fly ash silica fume, rubber powder, wheat straw ash, coconut fibers and ground nutshell etc., to enhance the performance properties of these soils. Despite this, this area still needs significant attention by engineers and scientists, innovating new technologies and methods to stabilize these soils on economic ground. The ground granulated blast furnace slag (GGBS) and bagasse ash (BA) are natural fiber residues, obtained from the refining processing of steel and sugarcane mills, respectively. Both binders contain silica, which has the ability to reduce the swelling potential of expansive soils while also improving soil stability through pozzolanic activities. So, the novelty of this research work involves examining the mechanical behavior of reinforced expansive soil. The bagasse ash and ground granulated blast furnace slag (GGBS) were used in the study. To examine the behavior of reinforced expansive soils, various testing approches such as index properties, direct shear, unconfined compressive strength, and oedometer tests were used. For a steady rise in the proportion of reinforcement up to a particular threshold, i.e., up to 3% of GGBS and 12% of BA, optimum moisture content increased, and generally maximum dry unit weights decreased. The optimum moisture content increased from 23.2 % to 26.78 % and maximum dry unit weight decreased from 15.84 kN/m2 to 15.34 kN/m2. In both soaked and unsoaked conditions, the cohesiveness reduced, and the angle of internal friction increased as the percentages of reinforcement increased. Similarly UCS increased from 98.4 kPa to 246.34 kPawith a decrease in swelling potential from 9.75 to 3.75 and it was maximum at 12% of BA and 3% of GGBS. The treated expansive soil's strength increased due to changes in soil behavior from clayey to silty, as well as a decrease in swelling potential and PI as well. The results of the tests revealed that ground granulated blast furnace slag and bagasse ash are effective additions for improving soil mechanical behavior.