Mechanical properties of solidified dredged soils considering the effects of compaction degree and residual moisture content

Abstract

The use of biopolymers in combination with natural plant fibers to solidify soils has proven effective in civil engineering, as they are not only considered sustainable, but also have excellent mechanical properties. However, the specific quantitative relationships between mechanical strength and residual moisture content (RMC) in the cured system are still unclear. In this study, the solidification effects of xanthan gum (XG, weight ratio to dry soil of 1.5%) and jute fiber (JF, weight ratio to dry soil of 0.6% and length of 20 mm) on the Yellow River dredged soil (YRDS) were investigated at different degrees of compaction (90%, 94% and 98%) after reaching a preset RMC (75%, 50%, 25% and 0%). The results show that unconfined compressive strength (UCS) and splitting tensile strength (STS) increase significantly with decreasing RMC and increasing compaction. The effect of internal moisture on STS was even more dramatic, with a maximum increase of 404% especially when the RMC was reduced from 25% to 0%. The contribution rate of strength (Rcsi) of UCS reaches 49.09%–51.85%, while the Rcsi values of STS at the same RMC of 25% reach only 19.86%–23.08%. A logistic function based model can predict well the mechanical strength at different RMC (R2 ≥ 0.9789). MIP and SEM results show that increasing the degree of compaction mainly affects the large pores (20–100 μm) and improves the mechanical strength by enhancing the bonding effect between XG and JF in the soil particles. In addition, 94% compaction ratio is an optimal choice for practical engineering applications.