Synergistic influence of lime and straw on dredged sludge reinforcement under vacuum preloading

Abstract

Dredged sludge, characterized by its elevated water content, fine particles, low permeability, and deficient drainage performance, poses challenges for practical engineering applications. This study aimed to enhance the efficacy of vacuum preloading treatment for dredged sludge while addressing environmental concerns associated with straw waste. The investigation focused on the synergistic effects of lime and straw in dredged sludge treatment. Laboratory modeling tests were conducted, varying lime and straw dosages, to monitor drainage and vacuum changes during vacuum preloading. Water content and shear strength measurements were taken at the conclusion of vacuum preloading. Subsequently, the microstructure of samples underwent analysis through mercury-in-pressure (MIP) testing, scanning electron microscopy (SEM), and x-ray diffractometry (XRD). Results demonstrated a significant increase in drainage rate during vacuum preloading when lime and straw were combined. The optimal lime and straw combination for drainage efficiency was found to be 0.3% lime + 0.2% straw (TS4), leading to a 20.74% increase in total drainage and a 281.74% increase in drainage rate compared to normal soil (C). In this scenario, vacuum pressure transfer efficiency rose by 125.6%, and soil shear strength exhibited a notable increase of 60.8%. MIP, SEM, and XRD outcomes confirmed the synergistic effect of lime and straw in the vacuum preloading of dredged sludge, with the most optimal combination identified as 0.3% lime + 0.2% straw. This study introduces a novel approach for treating dredged sludge, expanding the application of straw while mitigating its environmental impact.