Installation of granular columns is a cost-effective and versatile in situ technique to improve the shear strength, settlement, and drainage behavior of weak soils. It involves backfilling vertical boreholes in the ground with granular materials stiffer than the native soil, such as stone or compacted sand. However, the massive use and overexploitation of sand and natural aggregates have depleted their reserves in recent decades, causing damage to the environment, creating sand shortages, and skyrocketing their price. Hence, it is essential to develop a sustainable alternative to natural aggregates to construct granular columns. The ever-increasing stockpiles of waste glass could be a potential replacement for natural sand in several geotechnical construction applications, noting that both materials have a similar chemical composition. Using crushed waste glass (CWG) as an alternative to traditional natural and manufactured (quarried) sands in granular columns could offer a multipronged benefit by recycling nonbiodegradable waste (glass) and by conserving a depleting natural resource (sand). Using a large direct shear (LDS) machine, this study investigated the shear strength behavior of kaolin (to represent a typical weak soil) reinforced with a central granular column. Three different materials were separately used to backfill the column, including natural sand (NS), manufactured sand (MS), and CWG. The results revealed that the geocomposites containing the CWG column have the highest peak friction angle and relatively greater shear strength under high normal stresses, favoring the potential use of CWG as a green alternative to traditional sands in backfilling granular columns, ultimately supporting resource conservation, waste recycling, and the paradigm shift toward a circular economy.

Granular columns are commonly used for ground improvement. However, minimal research is presently available on the effect of backfill particle size on the geotechnical performance of granular column-reinforced soil. Geo-environmentally, using crushed waste glass (CWG) as a sustainable replacement for depleting traditional construction sands could offer a cleaner feedstock to backfill granular columns while helping recycle growing stockpiles of waste glass, potentially supporting the circular economy transition and decarbonisation of the construction industry. Given these multi-pronged motivations, this study investigated the shear strength and consolidation behaviour of kaolin reinforced with a CWG granular column. Three different particle size ranges (PSR) of CWG were discretely used to install a granular column in the kaolin bed, including fine (0.50–1.0 mm), medium (1.0–1.7 mm) and coarse (1.7–3.35 mm) particles with median particle sizes of 0.78 mm, 1.42 mm and 2.30 mm, respectively. The geocomposite containing a medium CWG column showed the highest increase in friction angle, increasing from 14.0° for kaolin only specimens to 20.7° for the geocomposites. Similarly, the consolidation behaviour of reinforced kaolin (geocomposites) was typically superior to that of kaolin only specimens. Notably, installing a coarse, medium or fine CWG column decreased the average compression index (C_c) of the geocomposites by almost 17%, 35% or 50%, respectively, compared to that of the kaolin only specimens. Given the promising results of this initial study, some suggestions are provided for future studies on assessing the application of CWG as an alternative backfill and sustainable geomaterial in granular column construction. Video This internationally-partnered Video Abstract highlights the findings of the research study, indicating that crushed waste glass (CWG) could potentially serve as a sustainable geomaterial and be used as a replacement for traditional construction sand to backfill granular columns in clayey soils for ground improvement, helping reduce the unsustainable exploitation of sand resources and increasing waste glass recycling, potentially supporting the paradigm shift to a circular economy and contributing to decarbonisation of the construction industry.

This study examines the geotechnical and hydro-mechanical behaviour of a model slurry used in high-solids, high-salinity applications, both before and after inline flocculation with an anionic polyacrylamide. Initial evaluations showed untreated tailings (UT) with a water content of 107%, void ratio of 2.6, and dry density of 0.711 t/m³, compared to polymer-amended tailings (PAT) with 53% water content, a void ratio of 1.6, and a dry density of 1.069 t/m³. Post-flocculation consolidometer tests revealed a distinct consolidation mode, with PAT showing 60% less settlement within the first 48 h and achieving 50% more free water drainage. Polymer treatment improved consolidation parameters, yielding a lower compressibility index (Cc of 0.74 vs. 1.05 for raw slurry), a higher coefficient of consolidation (Cv of 0.005 cm²/s for PAT vs. 0.0009 cm²/s for raw slurry), and an increased water retention capacity. Additionally, PAT demonstrated a final void ratio of 0.62 compared to 0.51 for the UT sample and an internal porosity characterised by discrete voids, supporting enhanced stability for long-term rehabilitation. These findings underscore the potential of inline flocculation to improve tailings management in saline conditions.