Abstract:

Cement, currently a widely utilized soil reinforcement material, elevates soil pH and poses potential risks of groundwater contamination during application. This study employed three environmentally friendly materials, namely, γ-polyglutamic acid (γ-PGA), β-glucan, and a cross-linked γ-PGA-β-glucan mixture (γ-PGA-β-G crosslinker), to reinforce silty soil. The mechanism by which cross-linked biopolymers enhance the compressive and shear strength of silty soil was examined through unconfined compressive strength tests, direct shear tests, Fourier transform infrared spectroscopy (FTIR) characterization, and scanning electron microscopy (SEM) observations before and after reinforcement. Results indicated that the compressive and shear strengths of the silty soil reinforced with cross-linked biopolymers outperformed those reinforced with single biopolymers. The dosage of the cross-linked biopolymer and the age of maintenance significantly influenced the improvement effect. Longer maintenance periods better enhanced silty soil. Within a certain dosage range, the strength of silty soil positively correlated with the dosage. Specifically, a 1.5% ratio provided optimal unconfined compressive strength for γ-PGA-β-G-improved silt, with the 28-day maintenance strength reaching 47.07 kPa, a 1.43-fold increase over untreated silt. The γ-PGA-β-G cross-linked biopolymers effectively augmented the cohesion and internal friction angle of silt. This enhancement mechanism is attributed to the three-dimensional mesh structure formed by the crosslinks, which exhibits superior mechanical properties and envelops the silt particles, thereby significantly boosting the silt’s strength.

Key words: silty soil, γ-polyglutamic acid, β-glucan, γ-PGA-β-G crosslinked biopolymer, unconfined compressive strength, shear strength