24 - Swelling behavior of expansive soils stabilized with expanded polystyrene geofoam inclusion

Abstract

Due to its undesirable volume change behavior, expansive soil causes great distress and severe damages to the overlying structures built on it. In particular, transportation infrastructures are highly susceptible to destruction as they extend over larger areas. Globally, the annual maintenance cost of expansive soils exceeds the cost of damage caused by natural catastrophes. Therefore these soils require modification, which demands an engineering solution to satisfy the design criteria. There are numerous techniques available to stabilize the expansive soils. Soil stabilization is one of the techniques used to mitigate the swelling potential in expansive soil widely through two approaches, namely chemical and mechanical stabilization. Chemical stabilization involves the addition of cementing agents (e.g., lime and cement) to improve the engineering properties and restrict the swelling. However, the physical stabilization involves compaction of soil with the help of reinforcing (e.g., geogrid and natural/synthetic fibers), cushioning (e.g., sand cushion method), or inclusion (e.g., geofoam and rubber) materials. The use of polymeric materials (i.e., geosynthetics) in soil stabilization is highly encouraged due to its desirable properties and durability. In this study, waste expanded polystyrene (EPS) is used to stabilize expansive soils. The innovative use of compressible EPS blocks as recycled geobeads (GB) and geofoam granules columns (GGC) in expansive soils to mitigate the swelling potential has been experimentally investigated. For this study, large one-dimensional laboratory consolidation equipment was developed to perform a series of swell-compression tests on compacted soil specimens. The prefabricated equipment was enabled to accommodate the California bearing ratio mold of 150mm internal diameter and 175mm height (circular area of 17,671mm2), covered with an outer tank provision for bottom drainage purposes. The developed large consolidation apparatus allows a maximum surcharge load of 600kPa applied in the lever arm (1:10). The vertical displacement was measured using a standard dial gauge with an accuracy of 0.01mm placed on top of the moving frame in the apparatus. The tests were carried out in remolded soil samples with varying EPS inclusion. From the series of tests results, qualitative and quantitative reductions in swelling potential were observed due to the presence of EPS geofoam (i.e., GB and GGC) in expansive soil. Furthermore, the mechanism of EPS geofoam influence on control swelling could be explained by the soil–EPS interaction.