Abstract
Lightweight fill can be advantageous in embankment construction for the purposes of reducing the (i) bearing pressures on the underlying soil foundation, (ii) destabilizing moments for constructed earthen slopes, and (iii) earth pressures acting behind retaining walls. This paper investigates the merits/limitations of particulate expanded polystyrene (EPS) beads mixed with clayey sand (CS) soil as lightweight fill, considering both geotechnical and environmental perspectives. The bench-scale geotechnical testing programme included standard Proctor (SP) compaction, California bearing ratio (CBR), direct shear (sheardox), oedometer and permeability testing performed on two different gradation CS soils amended with 0.5, 1.5 and 3.0 wt.% EPS, investigating two nominal bead sizes equivalent to poorly-graded medium and coarse sands. Compared to the unamended soils, the compacted dry density substantially decreased with increasing EPS beads content, from 2.09 t/m3 (0 wt.% EPS) to as low as 0.33 t/m3 for 3 wt.% (73 v.%) of larger-sized EPS beads. However, from analyses of the test results for the investigated 50 to 400 kPa applied stress range, even 0.5 wt.% (21 v.%) EPS beads caused a substantial mechanical failure, with a drastic decay of the CBR and compressibility parameters for the studied CS soils. Given the more detrimental environmental cost of leaving myriads of separate EPS beads mixed forever among the soil, it is concluded that the approach of adding particulate EPS beads to soils for producing uncemented lightened fill should not be employed in geotechnical engineering practice.
Highlights
A considerable share of the costs of building and infrastructure constructions depends on the geomechanical properties of the underlying soil deposits and the required foundation types
1nature of the 2EPS beads, the3 equilibrium axial compression increases for greater expanded polystyrene (EPS) content and for higher applied stress, with significantly greater compression occurring for those mixtures containing larger-sized EPS beads (EPS-2)
(21–73 v.%) EPS beads, and contrasting with the clayey sand (CS) soils themselves, as controls, the following conclusions are drawn: (a) In terms of dry density, expectedly, the compacted dry density value substantially decreased with increasing EPS beads content, reducing from 2.09 t/m3 for the controls
Summary
A considerable share of the costs of building and infrastructure constructions depends on the geomechanical properties of the underlying soil deposits and the required foundation types. Major problems, including inadequate bearing capacity, excessive subsidence or earth pressures next to structures, liquefaction potential and slope instability issues, adversely impact on financial costs, construction completion time and hazard risks in projects; as an example, a new highway flyover requiring approach embankments bearing on weak soil deposits, as well as face slopes and/or earth-retaining wall constructions. In this regard, utilizing lightened fill solutions reduces (i) bearing pressures acting on the embankment foundation, (ii) destabilizing moments for constructed earthen slopes that could otherwise have potential slope instability issues, and (iii) earth pressures acting be- 4.0/). For the latter (soil blends incorporating lightweight additives), it is known that the type, aspect ratio and content of these additives have important roles in the mechanical properties of the mixtures
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