清淤底泥脱水干化研究Ⅱ:电渗联合真空预压技术

Research on dewatering and drying of dredged sediment II:Electroosmosis combined with vacuum preloading technology

针对进一步提高电渗真空预压的脱水效率、电压加载模式不清和工程应用评价指标难等问题,研发了一套自动化监测装置,模拟真空预压、双面排水真空预压、电渗真空预压和双面排水电渗真空预压的底泥脱水干化过程,确定了电渗真空预压的电压加载模式以及底部排水通道的影响,并通过沉降量预测含水率变化情况。结果表明:在4种模拟对比实验下,电渗真空预压效果最好,脱水干化后的含水率约40%,体积压缩率45%~47%,抗剪强度为66~76 kPa;增加底部排水通道、保证真空压力的有效传递、缩短了渗流途径,提高了排水效率、缩短了固结周期,改善了底泥深部脱水不良和不均匀沉降问题;根据电渗电压和出水速率之间关系及底泥电流的变化情况,确定了电压加载模式;若采用固定电压加载,电压大小为24 V,若采用逐级加载,初始电压为12 V持续48 h,24 V持续36 h,36 V持续24 h,48 V持续12 h,电压越高,持续时长越短;根据沉降量变化与排水量之间的关系,通过排水量与含水率之间的变化规律,确定了含水率与沉降量之间的关系公式,实现了通过沉降量预测含水率的目的,为含水率实时监测提供参考。

In response to issues such as further improving the dehydration efficiency of electroosmotic vacuum preloading,unclear voltage loading mode,and difficulty in evaluating engineering application indicators,an automated monitoring device has been developed.It simulated the dewatering and drying process of sediment through vacuum preloading,double-sided drainage vacuum preloading,electroosmotic vacuum preloading,and double-sided drainage electroosmotic vacuum preloading.The voltage loading mode of electroosmotic vacuum preloading and the influence of bottom drainage channel were determined,and the change in water content was predicted through settlement amount.The research results indicate that:under four simulated comparative experiments,the vacuum preloading effect of electroosmosis is the best,with a moisture content of about 40%after dehydration and drying,a volume compression rate of 45%~47%,and a shear strength of 66~76 kPa.It increased bottom drainage channels,ensured effective transmission of vacuum pressure,shortened seepage paths,improved drainage efficiency,shortened consolidation cycles,and improved the situation of poor dewatering and uneven settlement of deep sediment.Based on the relationship between electroosmotic voltage and water discharge rate,as well as the changes in sediment current,the voltage loading mode has been determined.If a fixed voltage loading is used,the voltage is 24 V.If a stepwise loading is used,the initial voltage is 12 V for 48 hours,24 V for 36 h,36 V for 24 h,and 48 V for 12 h.The higher the voltage,the shorter the duration.Based on the relationship between changes in settlement and drainage,and through the variation pattern between drainage and water content,the relationship formula between water content and settlement was determined,achieving the purpose of predicting water content through settlement and providing technical guidance for real-time monitoring of water content.