Research on the Solidification Mechanism Based on the Water Characteristic Curve of Solidified Dredged Sediment

The fractal model about water characteristics of solidified sediment was built according to the granular metric analysis curve of solidified dredged sediment, the measured value during the low-suction stage of the curing process was used for fitting parameters in the model to obtain the complete water characteristic curve of solidified dredged sediment. Then, the quantitative calculation model of capillary water, attached water, evaporated water and bound water was built by the water characteristic curve and from the view of quantitative angle, the paper analyzed the solidification mechanism of solidified dredged sediment. The result showed that： the model can realize the quantitative calculation about different tapes of water during the curing process, the evaporated water during the curing process mainly came from the capillary water, and the generated bound water during the curing reaction came from the attached water.

Coupling effect of cement-stabilization and biopolymer-modification on the mechanical behavior of dredged sediment

Nowadays,biopolymer stabilization as a promising eco-friendly approach in soft ground improvement has attracted wide attentions.However,the feasibility of using biopolymer as a green additive of cementstabilized dredged sediment(CDS)with high water content is still unknown.In this study,guar gum(GG)and xanthan gum(XG)were adopted as typical biopolymers,and a series of unconfined compressive strength(UCS),splitting tensile strength(STS)and scanning electron microscopy(SEM)tests were performed to evaluate the mechanical and microstructural properties of XG-and GG-modified CDSs considering several factors including biopolymer modification,binderesoil ratio and wateresolid ratio.Furthermore,the micro-mechanisms revealing the evolutions of mechanical properties of biopolymermodified CDS were analyzed.The results indicate that the addition of XG can effectively improve the strength of CDS,while the GG has a side effect.The XG content of 9%was recommended,which can improve the 7 d-and 28 d-UCSs by 196%and 51.8%,together with the 7 d-and 28 d-STSs by 118.3%and 42.2%,respectively.Increasing the binderesoil ratio or decreasing the wateresolid ratio significantly improved the strength gaining but aggravated the brittleness characteristics of CDS.Adding XG to CDS contributed to the formation of microstructure with more compactness and higher cementation degrees of ordinary Portland cement(OPC)-XG-stabilized DS(CXDS).The micro-mechanism models revealing the interactions of multiple media including OPC cementation,biopolymer film bonding and bridging effects inside CXDS were proposed.The key findings confirm the feasibility of XG modification as a green and high-efficiency mean for improving the mechanical properties of CDS.

High-efficiency stabilization of dredged sediment using nano-modified and chemical-activated binary cement

High-efficiency disposal of dredged sediment(DS)has become an imperative geo-environmental engineering issue due to the limited landfilling space and severe environmental burdens.This study firstly developed a novel high-efficiency nano-modified and chemical-activated binary cement(NBC),which was composed of binary cement(BC)consisting ordinary Portland cement(OPC)and ground granulated blast-furnace slag(GGBS),chemical-activator and nano-modifier.The effects of chemical-activation and nano-modification on the strength development of BC-stabilized DS(BCDS),and the optimum mix of NBC were respectively achieved via a series of unconfined compressive strength and orthogonal tests.Then,the high-efficiency and economic applicability of NBC in DS stabilization were evaluated by comparing with OPC.Furthermore,the microstructure and mineral composition evolutions inside NBCstabilized DS(NDS)were explored by conducting X-ray diffraction(XRD)and scanning electron microscopy(SEM)tests.The results show that both chemical-activation and nano-modification could effectively improve the strength gain of BCDS,and compared with single chemical-activator and nanomodifier,the composite chemical-activators and nano-modifiers exhibited better performances.Based on BC with OPC/GGBS mass ratio of 1:1,both anhydrous sodium metasilicate/anhydrous sodium sulfate(SM/SS)and nano-SiO_(2)/nano-MgO(NS/NM)with mass ratio of 1:9 were respectively determined to be optimum chemical-activator and nano-modifier.The optimum mass ratio of BC,SM/SS and NS/NM was 20:2:1,i.e.the optimum mix of NBC.Compared with OPC,NBC exhibited higher stabilization efficiency and better economic applicability.The generation of calcium silicate hydrate(CSH),calcium aluminate hydrate(CAH)and ettringite contributed to the formation of dense cemented soil matrix inside NDS,and a conceptual micro-mechanism model characterizing the strength development under the coupling action of chemical-activation and nano-modification was proposed.

Numerical Modelling of Sediment Particle Transportation on a Navigation Inlet Using the Particle Tracking Model (PTM)

This paper investigates particle transportation using a numerical model application approach to understand the final fate of suspended sediment particle masses due to a dredging operation in a navigational harbor inlet using PTM (Particle Tracking Model). The investigation applied PTM and simulated particle transportation at a navigational harbor called St Jerome Creek Inlet in Chesapeake Bay in Maryland. The United States Army Corps of Engineers (USACE), Maryland District, designed jetties for the inlet, which, when constructed, would minimize dredging requirements from once in a two-year period to once in a ten-year period. In the meantime, due to the frequent dredging requirements of the inlet, there exists a need to understand the fate of the suspended sediments from the dredging operations to assess the environmental impact on the aquatic environment and the coastal community. This study used PTM to simulate the transportation of sediments in a 30-day period during a dredging operation. Ten sediment source locations were selected as possible sites from which dredged materials could be introduced into the flow system. The model output was analyzed to draw conclusions. Results showed that most suspended sediment particle masses moved from their initial site locations and settled along the shoreline, whilst the sediments that found their way out of the inlet system towards the ocean migrated southward and settled approximately 6 miles at the tip of the mainland. The objective of the study is to track sediment particles from a dredging operation. This would be significant in tracking possible contaminants in an aquatic environment for future environmental management decisions.

Utilization of Dredged River Sediment in Preparing Autoclaved Aerated Concrete Blocks

In this study,the dredged river sediment,soft texture and fine particles,is mixed with other materials and transformed into eco-friendly autoclaved aerated concrete(hereinafter referred to as AAC)blocks.The results indicated the bricks produced under the conditions of 30%–34%dredged river sediment,24%cement,10%quick lime,30%fly ash,2%gypsum and 0.09%aluminum powder with 0.5 water to material ratio,2.2 MPa autoclave pressure and 6 h autoclave time,the average compressive strength of 4.5 MPa and average dry density of 716.56 kg/m³were obtained,the two parameters(strength&density)both met the requirement of national industry standard.At the same time,the contents of dredged river sediment,cement,lime,fly ash,gypsum and aluminum powder were 15%,48%,20%,15%,2%and 0.09%,respectively,and the non-AAC block made of 0.5 water to material ratio,the average compressive strength of 3.1 MPa and average dry density of 924.19 kg/m³were obtained,the two parameters(strength&density)also met the requirement of national industry standard.In addition,the AAC block’s phase composition and morphology were micro-analyzed by SEM and XRD,the main substances in AAC block were found to be tobermorite and CSH,Among them,the chemical bond between Si-O-Si and Al-O-Al is broken,Al-O-Si is regenerated,Al substituted tobermorite with better strength is formed,and the compressive strength of AAC is further improved.

Experimental Research on the Dewatering of Dredged Sediment from Dianchi Lake

[Objective] The technological parameter suitable for the dewatering of dredged sediment from Dianchi Lake was studied.[Method] By means of the treatment method of sewage sludge in sewage treatment plant,flocculants including FeCl3,Al2(SO4)3 and PAM were taken as dewatering agents which were added in dredged sediment.[Result] The results showed that Al2(SO4)3 had better dewatering effect than FeCl3 and PAM,and the optimum dosing quantity of Al2(SO4)3 in dredged sediment was 170 mg/L,in addition,the water quality of supernatant met the first class B standard of GB18918-2002 and could be directly discharged to nature water without pollution.[Conclusion] The study could provide a simple and feasible way for the rapid dewatering of dredged sediment from Dianchi Lake,which would be convenient for the disposal and resource utilization of dredged sediment.

河湖库淤积治理中底泥清淤的内涵与发展方向

淤积问题对我国的水利事业影响深远,而底泥清淤是近些年淤积治理中经常采用的措施。针对底泥清淤的现状和存在问题,系统梳理了底泥清淤这一学科交叉领域的相关理论、技术和方法;阐述了对底泥清淤的概念、内涵、类型及基本问题的科学理解;提出了淤积治理中底泥清淤必须明确的四大问题:为什么治理、治理什么、用什么方法治理以及对后续产物如何处置。依据淤积对河湖库产生的危害,可分为物理性淤积、化学性污染和生态性损害三种类型。分别讨论了工程清淤、环保清淤和生态清淤间的共性和差异。对底泥清淤工程在目的、目标、手段及后续处理处置方面的现状及存在问题进行了评述。未来底泥清淤势必成为一个长期存在的工程和管理行为,因此更加高效、低投入、绿色、可持续的底泥清淤技术,是行业必然的发展方向。

城市内湖底泥特性及资源化利用分析

当前园林绿化用土是城市内湖底泥资源化利用的主要途径之一,但资源化利用过程中可能存在的环境污染风险问题不容忽视,因此了解底泥特性是指导其资源化利用途径的基础。以江西省九江市甘棠湖、南门湖疏浚底泥为研究对象,检测疏浚底泥的基本理化性质、营养肥力指标、重金属含量及多环芳烃含量,系统分析其底泥特性并探究其资源化利用方式的匹配性。结果表明:内湖疏浚底泥的有机质平均含量为45.5 g/kg,pH为5.7,水解性氮平均含量为130.7 mg/kg,有效磷平均含量为62.6 mg/kg,速效钾平均含量为248.7 mg/kg,基本理化性质及营养肥力指标均满足CJ/T340-2016《绿化种植土壤》要求,同时重金属、多环芳烃等典型污染因子在CJ/T340-2016《绿化种植土壤》、GB36600-2018《土壤环境质量建设用地土壤污染风险管控标准》要求范围内。相比采购种植土,利用疏浚底泥制备绿化种植土用于绿化工程的成本,显著降低30.5%。综上所述,针对养分含量高、重金属污染程度低的城市内湖底泥,经进一步处理后可用于园林绿化及种植土制备,其资源化利用潜力较大。研究成果可为城市内湖底泥处理处置去向及城市建设用土选择提供数据支撑和参考。

我国疏浚淤泥处置与利用研究进展

淤泥处理处置与资源化利用是当前困扰工程技术人员和阻碍清淤疏浚工程顺利开展的重大难题。梳理了目前我国疏浚淤泥处置与利用的主要技术方法,简要介绍和评述了每种技术的主要特点、原理和应用情况,同时对相关基本概念内涵进行了梳理,对疏浚淤泥处置利用的未来发展方向进行了展望。

Impacts of channel dredging on hydrodynamics and sediment dynamics in the main channels of the Jiaojiang River Estuary in China

Channel dredging in estuaries increases water depth and subsequently impacts sediment dynamics and morphology. The Jiaojiang River Estuary is dredged frequently owing to heavy shipping demands. In this study,the effects of different dredging schemes on siltation were assessed through numerical modeling. The sediment model of the Jiaojiang River Estuary utilized an optimized bottom boundary layer model that considered the bed sediment grain size and fluid mud, and this model was calibrated using field data. Result reveal that channel dredging modifies the flow velocity inside and around the channel by changing the bathymetry;subsequently, this affects the residual current, bed stress, suspended sediment concentration, and sediment fluxes. Increasing the dredging depth and width increases the net sediment fluxes into the channel and dredging depth has a greater influence on the channel siltation thickness. When the dredging depth is 8.4 m or11.4 m, the average siltation thickness of the channel is 0.07 m or 0.15 m per mouth respectively. The parallel movement of the channel has small effects on the siltation volume during the simulation period. The sediment deposits in the channel primarily originates from the tidal flats, through bottom sediment fluxes. Vertical net circulation has a dominant impact on siltation because the difference of horizontal current of each layer on the longitudinal section of the channel increases, which intensifies the lateral sediment transport between the shoal and channel. The influence of vertical frictional dissipation on the lateral circulation at the feature points accounts for more than 50% before dredging, while the non-linear advective term is dominant after dredging. Tidal pumping mainly affects the longitudinal sediment fluxes in the channel. These results can be used for channel management and planning for similar estuaries worldwide.

万家寨水库运行以来调洪库容变化规律及恢复措施研究

为了给万家寨水库调洪库容有效恢复提供科技支撑,系统梳理了万家寨水库入出库水沙变化情况、库区泥沙冲淤演变规律、调洪库容变化规律以及淤损库容恢复措施,结果表明:1)万家寨水库1999—2023年非汛期运行水位为952~980 m,1999—2010年汛期运行水位为950.9~967.2 m、2011—2023年(除2016年外)汛期降低水位运用后最低水位为921.6 m;2)万家寨水库1999—2023年多年平均入库水量约为185.19亿m^(3)、沙量约为0.501亿t,出库水量约为180.70亿m^(3)、沙量约为0.363亿t;3)万家寨水库2010年汛后淤积纵剖面基本达到设计淤积平衡状态;2011年以来水库排沙运用,截至2023年10月总库容淤损2.859亿m^(3)、调洪库容淤损0.191亿m^(3);4)万家寨水库入库长历时大流量过程有利于降低水位敞泄运用排沙,坝前水位低于952.00 m时出库含沙量迅速增加,降至淤积面以下或泄空敞泄时,产生的溯源冲刷有利于提高输沙效率;5)单纯依靠水力减淤已无法有效恢复万家寨水库调洪库容,可采用水力减淤与机械清淤相结合的方式减淤,清淤泥沙输送至主河槽随水流动力排出库区或输送至岸上进行泥沙综合利用。

重金属疏浚污泥快速脱水固稳化技术试验

针对我国疏浚污泥处置低效且成本高以及工业固废——高炉矿渣(GGBS)综合利用率低的问题,提出了一种疏浚污泥快速脱水固化稳定化新技术(PHDVPSS),并通过试验系统性地对新技术的实用可行性进行了分析。同时,进一步分析了GGBS对新技术的影响性。分析表明:该技术在脱水效率、固化强度和毒性浸出方面,较传统技术均具有明显优势。仅3 d时间可将底泥含水率降低近50%,90 d处理样品的UCS是传统方法处理的近11倍,而浸出浓度仅约为传统方法的2/3。GGBS添加量增加对新技术处理效果具有显著提高作用,采用30%GGBS时,仅4 d时间可将污泥含水率降低近2/3,在90 d时,VP-GM-3的UCS是VP-GM-1的近12倍,而浸出浓度仅为VP-GM-1的1/3左右。

底泥资源化利用研究进展

目的:为解决以底泥为主的内源污染问题,清淤疏浚等工程措施被广泛应用于河流、湖泊和水库等水体环境治理工程。目前,我国因清淤疏浚而产生的底泥高达7000万t,且仍以每年4%~6%的速度增长。同时,底泥“污染”和“资源”的双重属性也为其资源化利用带来了机遇与挑战。方法:为此,本文通过文献总结对现阶段底泥资源化利用技术的原理、优缺点、成本以及未来发展方向等进行了系统性梳理。结果与结论:发现底泥资源化利用已经涉及生态恢复、建筑施工、建材制造、能源回收、环保材料等多个领域。未来,底泥资源化利用应通过分区建立底泥数据库,提高疏浚工程精度,并在此基础上分区、分层、分类利用底泥,因地制宜选择资源化利用技术;同时,需要优化底泥前处理技术,提升底泥相关产品质量品级,并聚焦底泥中的有毒有害物质和新污染物以实现其安全利用;最终,完善底泥资源化利用全过程标准体系,逐步规范底泥资源化利用市场。

基于多场耦合有限元的天福庙水库清淤过程污染物磷释放行为研究

天福庙水库处于黄柏河流域东支,是宜昌市嫘祖镇的水源地,受周边磷矿开采的影响,2015年以来水库水环境质量不断恶化,为此宜昌市政府对天福庙库区河道实施了生态环保清淤工程。实施过程中发现,清淤船作业时清淤设备吸头会对周边水体及底泥造成扰动,进而可能会对水库水体造成二次污染。为了探究清淤过程导致的底泥沉积物扰动情况,利用COMSOL Multiphysics中的层流和稀物质传递等模块建立水库底泥污染物磷释放模型,基于天福庙水库水质和清淤设备的属性数据,以及前人总结的经验值,模拟清淤扰动过程中不同清淤时间和不同水平扰动范围下底泥的扩散速度分布特征,以及水库底泥和孔隙水中的磷污染物的释放规律,并进一步通过实地模拟底泥扰动实验验证模型可靠性。模拟和实验结果表明:当清淤扰动时间不断增加,底泥及其所含的污染物会逐渐向水面扩散,扩散速度和污染物浓度会随时间的推移而不断增大;在同一清淤扰动时间下,再悬浮液和磷污染物的纵向扩散受水平扰动范围的影响明显,水平扰动范围越大,底泥向水面扩散越多,底泥磷污染物释放浓度越多,对水库水环境质量危害越大。释放初期,水体中污染物浓度增加较为剧烈,孔隙水中的磷污染物释放起主导作用;随后水体中污染物浓度增加速度变缓,后期再悬浮液逐渐混合均匀,垂线上的总磷浓度差距减小,底泥中污染物的释放达到平衡状态。研究发现模型能够对清淤扰动造成的水体总磷浓度变化进行合理预测,为湖泊型深水水库清淤工程实践的防范措施提供了科学依据。

矿渣改性淤泥用于管沟回填的工程特性研究

矿渣、淤泥是典型固废材料,为拓展资源化利用途径,以矿渣、硫铝酸盐水泥为固化剂,将淤泥改性为早强流动化土,并用于市政管沟回填工程。采用室内试验方法研究矿渣替代部分水泥后,流动化土在不同含水率、矿渣替代率下的施工和易性与力学特性。结果表明:当含水率增大时流动度会随之增大而密度将随之减小,矿渣替代率的改变对流动度、密度影响有限;流动化土的无侧限抗压强度随着龄期的增加而增加,但随含水率和矿渣替代率的增加而减小,当矿渣替代率小于42.9%时,养护1天后强度可达100 kPa以上,流动化土的抗干湿循环能力随矿渣替代率的增加而降低;流动度与填充性呈正相关,当流动度>200 mm时,流动化土的填充率可达97%以上,能较好为工程所用。

Mechanical properties of dredged soil reinforced by xanthan gum and fibers

Biopolymers have become popular in geotechnical engineering as they provide a carbon-neutral alternative for soil solidification.Xanthan gum(XG)and jute fiber(JF)were selected to solidify the Yellow River dredged soil.The mechanical behavior of solidified dredged soil(SDS)was investigated using a series of uniaxial compression and splitting tension tests at different XG and JF contents and fiber lengths.The results indicate that on the 28th day,the unconfined compressive strength(UCS)values of SDS samples reached 2.83 MPa and splitting tensile strength(STS)of 0.763 MPa at an XG content of 1.5%.When the JF content was greater than 0.9%,the STS of the SDS samples decreased.This is because that the large fiber content weakened the cementation ability of XG.The addition of JF can significantly increase the strain at peak strength of SDS samples.There is a linear relationship between the UCS and STS of the dredged soils solidified by XG and JF.Microanalysis shows that the strength of SDS samples was improved mainly via the cementation of XG itself and the network structure formed by JF with soil particles.The dredged soil reinforced by XG and JF shows better mechanical performance and has great potential for application.

Clean-up and disposal process of polluted sediments from urban rivers

In this paper, the discussion is concentrated on the properties of the polluted sediments and the combination of clean-up and disposal process for the upper layer heavily polluted sediments with good flowability. Based on the systematic analyses of various clean-up processes, a suitable engineering process has been evaluated and recommended. The process has been applied to the river reclamation in Yangpu District of Shanghai City, China. An improved centrifuge is used for dewatering the dredged sludge, which plays an important role in the combination of clean-up and disposal process. The assessment of the engineering process shows its environmental and technical economy feasibility, which is much better than that of traditional dredging-disposal processes.

三峡水库清淤及淤积泥沙综合利用可行性研究

库容保持是水库发挥防洪、发电、航运、水资源利用等功能及综合效益的重要保障。三峡水库库容是极其宝贵的战略资源,根据实测资料分析,阐明了三峡水库运行以来库区泥沙淤积特征,基于三峡库区不同库段泥沙淤积特点和淤积泥沙适宜的利用途径分析,提出了三峡库区分段分类淤积泥沙利用总体方案。建议尽快编制三峡水库清淤及淤积泥沙综合利用总体实施方案,推进库区清淤及排沙试点工作并逐步推广实施,深入研究淤积泥沙低成本材料利用技术,为保障三峡水库库容安全以及综合效益的可持续发挥提供支撑。

改性松浦支渠疏浚底泥吸附重金属离子的研究

中国河流每年产生大量的疏浚底泥,大量堆积不仅占用土地资源,而且对环境还有很大的影响。底泥的二次利用显得尤为重要,基于以废制废的原则,提高底泥资源化利用的价值,以松花江松浦支渠疏浚底泥为目标,对其进行资源利用。首先以丙烯酸、富马酸为原料,以过硫酸铵为引发剂制备聚AA-FA,以磷酸氢二钠中和制得聚AA-FA磷酸盐。利用聚AA-FA磷酸盐对热解的疏浚底泥进行改性,制备得到聚AA-FA改性松浦支渠疏浚底泥。研究发现聚AA-FA改性松浦支渠疏浚底泥对于重金属离子具有较强的吸附作用。在添加量质量分数为9%时脱除离子的能力最高可达到99%,脱除不同离子的能力由大到小顺序为Ni^(2+)、Pb^(2+)、Cr^(3+)。

辛克雷水电站引水防沙体系设计

辛克雷水电站所在河流含沙量大、电站水头高,泥沙对水库有效库容和水轮机磨蚀影响较大。针对工程突出的泥沙问题,根据“正向泄洪冲沙、侧向引水”的思路开展电站引水防沙体系设计,通过综合采用首部枢纽“四道防线”减淤排沙、水库拦沙及机械清淤等措施,使进入压力管道的泥沙含量达到设计含沙量的控制要求。设计方案可为同类型工程提供借鉴。