Bo Deng

To address the need for enhanced geotechnical performance in gravelly soil stabilization, this study investigated the synergistic effects of guar gum as an additive in enzyme-induced calcium carbonate precipitation (EICP) treatment. Through systematic experimentation combining unconfined compressive strength (UCS) tests, carbonate content quantification, and triaxial analysis, the mechanical behavior of treated soils was evaluated under varying EICP solution concentrations (0–2 mol/L) and curing durations. Results demonstrated that a 1.5 mol/L EICP solution achieved peak strength and carbonate precipitation before subsequent decline, while a 1% guar gum dosage optimized mechanical properties by balancing initial strength enhancement and precipitation efficiency. Scanning electron microscopy revealed microstructural mechanisms wherein guar gum provided heterogeneous nucleation sites for calcite crystals, while its interaction with EICP enabled dual-phase pore filling and interparticle bonding. This synergistic effect created a three-dimensionally reinforced matrix, significantly improving both UCS and unconsolidated undrained shear strength compared to native and EICP-only specimens. The findings establish a theoretical framework for regulating calcite precipitation patterns and enhancing cementation mechanisms in gravelly soil improvement, offering practical guidelines for foundation engineering applications through the combined use of guar gum and EICP.

This study presents an environmentally friendly alternative to conventional energy-intensive methods for soil improvement by investigating an enzyme-induced active magnesium oxide carbonation (EIMC) technique for the stabilization of gravelly soil. The solidification efficacy and strengthening mechanism of EIMC-treated soil were systematically investigated through a combination of mechanical property tests and microstructural analyses. Results indicate that key mechanical properties—including compressive strength, shear strength, and elastic modulus—were directly proportional to the magnesium oxide (MgO) content. Notably, an 8% MgO content resulted in a 113-fold increase in unconfined compressive strength (UCS) compared to the untreated soil. The strength development stabilized after a five-day curing period. While higher MgO content yielded greater absolute strength, the efficiency of strength gain per unit of MgO peaked at a 4% dosage. Consequently, considering both performance and efficiency, an MgO content of 4% and a curing period of 5 days are recommended as the optimal parameters. The EIMC treatment substantially improved the soil’s mechanical properties, inducing a transition in the failure mode from plastic to brittle, with this brittleness becoming more pronounced at higher MgO concentrations. Furthermore, the treatment enhanced the soil’s water stability. Microstructural analysis revealed that the formation of hydrated magnesium carbonates filled voids, cemented particles, and created a dense structural matrix. This densification of the internal structure underpinned the observed mechanical improvements. These findings validate EIMC as a feasible and effective eco-friendly technique for gravelly soil stabilization.

Conventional structural analysis of hinged precast frame beams (HPFB) often relies on a simplified load distribution method that may not fully account for deformation compatibility, potentially affecting result accuracy. To address this limitation, this paper develops a rigorous analytical framework based on the Winkler foundation model. The framework explicitly incorporates soil-structure interaction (SSI) and enforces static equilibrium and deformation compatibility at all structural nodes and hinges, thereby enabling a mechanically consistent prediction of structural responses. A comprehensive comparative analysis with a traditional frame beam (TFB) reveals the unique mechanical behavior of the HPFB system. Key findings demonstrate the HPFB configuration achieves a drastic reduction in maximum negative bending moment (63.5–83.5%) and shear force (7.8–22.8%), while increasing the maximum positive bending moment by 46–62%. This fundamental shift in internal forces occurs in conjunction with a characteristic segmented deflection profile. Sensitivity analysis further indicates that while the subgrade reaction coefficient significantly influences deflection patterns, its effect on bending moments and shear forces remains marginal. The proposed framework provides designers with a robust and theoretically sound tool for the analysis and design of HPFB structures, ensuring performance reliability while addressing limitations observed in current analytical approaches.