Mechanical properties of monolithic EPS-coated lightweight soil: unconfined compressive strength and small-strain dynamic characterization

Abstract

Expanded polystyrene (EPS) foam lightweight soil, a novel lightweight geomaterial, offers significant advantages in addressing the challenges of soft ground settlement and slope instability. To address the issue of inconsistent EPS particle distribution, this study presents a new material called monolithic EPS-coated lightweight soil (MECS) structure. The static strength characteristics and small strain dynamic response characteristics of MECS were investigated by conducting unconfined compressive strength tests and resonant column tests. The results show that (1) MECS exhibits a typical shear damage mode under uniaxial compression conditions, and its unconfined compressive strength (q_s) is inversely proportional to the thickness (T) of the EPS sleeve. (2) In the small strain range, the dynamic shear modulus (G) of MECS decreases with increasing T, but increases with increasing confining pressure (P). The dynamic shear modulus-dynamic shear strain curve (G - γ_c) exhibits clear decay characteristics, with an accelerated decay when γ_c > 10^-3 (T influence) and γ_c > 10^-4 (P influence). (3) A relationship connecting q_s and the initial dynamic shear modulus (G₀) has been formulated. By modifying the Hardin-Drnevich model, it becomes possible to accurately predict the normalized dynamic shear modulus decay curve for MECS in the small strain range. This curve exhibits a typical inverse “S" shape distribution characteristic. (4) The damping ratio (D) of MECS is positively associated with the T and negatively linked to the P. The damping ratio - dynamic shear strain curve (D - γ_c) shows a growing trend, and the growth rate increases with the increase of γ_c. The maximum damping ratio (D_max) shows an “S” shape growth with the increase of T, and a “C” shape decrease with the increase of P. Research shows that Romo's empirical formula precisely captures the damping characteristics of MECS and offers a dependable approach for quantitatively analyzing the D within the small strain scope. The research furnishes a critical theoretical groundwork and technical assistance for the wide application of MECS in soft soil foundation construction.