In biopolymer-soil stabilization, biopolymers function in the soil either as viscous fluids or rigid gels. However, the influence of these hydrogel states on soil liquefaction resistance and their underlying mechanisms remain insufficiently understood. This study examines the seismic response of sand treated with biopolymers under small-to-medium strain cyclic loading, with a focus on the efficacy of Cr3+-crosslinked xanthan gum (CrXG) in mitigating liquefaction. Liquefaction resistance and dynamic properties of CrXG-treated soil were compared against thermogelation and non-gelling viscous biopolymer treatments using cyclic direct simple shear and resonant column tests. CrXG treatment at 1 % content improved liquefaction resistance (CRR10) from 0.088 to 0.687 by preventing shear strain accumulation and pore pressure buildup, with enhancing dynamic shear stiffness and delaying stiffness degradation and damping ratio changes to higher strain levels. In contrast, soils treated with non-gelling viscous XG exhibited limited reinforcement under large strain cyclic loading, showing earlier liquefaction and lower CRR10 compared than untreated sand, alongside reduced dynamic shear modulus and rapid stiffness degradation. Comparisons across varying earthquake moment magnitudes revealed that CrXG-treated soil achieved liquefaction resistance comparable to other soil stabilization methods and demonstrated greater improvement efficiency than thermogelation biopolymers requiring thermal treatment. These findings highlight the potential of CrXG as a sustainable and practical solution for improving liquefiable soil stability under seismic loading.
When seismic loads are applied to saturated, loosely packed soils, shear strength is rapidly lost due to excess pore water pressure buildup, resulting in liquefaction. Experimental results highlight distinct influence of biopolymer hydrogels, depending on their state, on soil resistance to shear deformation under seismic loading. This section discusses the role of biopolymer hydrogel in the soil matrix during seismic loading based on their state. Fig. 9 presents a schematic figure illustrating the effects of biopolymer hydrogels in sand: non-gelling viscous type and gelation type, supported by environmental scanning electron microscope (ESEM, Quattro S, Thermo Fisher Scientific Inc.) images of XG- and CrXG-treated sand specimens captured under humid conditions.This research was supported by the Ministry of Oceans and Fisheries (MOF) of the Korean Government [No. 20220364] and National Research Foundation of Korea (NRF) funded by the Korean government (MSIT) [No. 2023R1A2C300559611]. Authors appreciate the Korea Institute of Civil Engineering and Building Technology (KICT) by providing technical support regarding to the cyclic simple shear apparatus.
