襄阳护城河清淤底泥处理工艺改进及工程设计

针对清淤淤泥体量大、含水率高、絮凝沉淀困难等特点,襄阳护城河清淤底泥处理工程参照武汉东湖通道湖底淤泥处理工程设计运行经验,将含水率为95%的清淤泥浆经固结压滤脱水形成含水率≤35%的脱水泥饼。固结压滤脱水改进工艺对泥浆调节池及尾水回用系统进行了适用性改造,减小了占地面积,加快了泥水分离,提高了泥浆进料浓度。泥浆进料时间由每流程55 min降至每流程40 min,每台(套)设备可多处理186.6 m3/d水下自然方底泥,每台机每流程可节省22.5 kW·h电能,实现了河湖清淤底泥的快速高效处理,可为类似项目提供借鉴。     

钠基泥浆脱水试验效果及特性研究

针对建筑施工产生的高含泥量废弃泥浆难以脱水分离处理的难题,提出了采用钠基膨润土配制泥浆进行脱水试验研究。对钠基膨润土和水配制的不同含泥量的黏土泥浆进行密度、黏度和胶体率的测定,并用气压法对其脱水性能进行比较,阐明了含泥量、气压的差异对泥浆脱水的影响。选择最难脱水分离的泥浆作为研究对象,通过气压试验、絮凝试验、絮凝-气压试验(无机、有机),分析了各自的脱水效率和作用机理,得到了絮凝剂种类、添加量与脱水分离效果的关系。结果表明,含泥量越高的泥浆越难进行脱水分离,增大气压并不能显著地影响泥水分离效果。当无机絮凝剂聚氯化铝(poly aluminum chloride,PAC)添加量为0.5%时,物化协同处理脱水效果良好,物化协同絮凝-气压法技术可行、脱水效率极高,有工程上运用的前景。     

典型无机絮凝剂对疏浚淤泥絮凝效果及出水水质影响研究

针对淤泥堆场堆填处置中，天然底泥自重落淤固结缓慢等问题，工程中常添加化学药剂来加快泥水分离过程。利用量筒沉积柱试验研究了5种典型无机絮凝剂对高含水率疏浚淤泥的絮凝沉积效果及上覆水水质(浊度值)的影响规律。5种典型的无机絮凝剂中，CaCl₂,PAS(聚合硫酸铝)的絮凝效果相对较好。在此基础上，探明了这两种絮凝剂在不同掺量下对疏浚淤泥沉积规律的影响。试验结果表明，CaCl₂,PAS掺量不同，泥浆自重沉积固结稳定后沉降量、沉降速率、沉积稳定时间不同，得到CaCl₂和PAS的最优掺量分别为0.8%,0.2%。在最优掺量下上覆水的去浊率可达到84%左右。CaCl₂通过Ca²⁺的交换作用和电性中和作用发挥絮凝作用；PAS主要通过土颗粒表面的电性中和作用发挥絮凝作用。结果可为大规模疏浚淤泥的快速絮凝和余水排放研究和设计提供参考借鉴。     

基于层次分析法的泥水分离絮凝剂比选

建筑工程中常见大量废弃泥浆的产生,目前常见的处置方法是在废弃泥浆中添加絮凝剂初步处理,再使用泥浆分离设备进一步泥水分离。絮凝剂的絮凝效果是该工艺过程中的关键影响因素之一。基于层次分析法,根据选取的多个性能参数指标,选出适用于特定工程废弃泥浆的最佳絮凝剂。     

水利清淤工程底泥及余水处理一体化设计

为验证水利清淤工程底泥及余水处理一体化设计的应用效果,以某水库为例,对清淤底泥及余水处理的效果进行分析。该水库清淤项目拟通过前端添加絮凝剂、助滤剂等对泥浆调理后,经板框压滤机完成淤泥脱水,实现泥饼含水率≤45%,同时维持余水的p H值在6～9之间;产生的余水在添加多功能高分子絮凝剂后,经高速絮凝反应沉淀去除总磷(TP)和大部分悬浮物(SS),之后再通过脱氮分子筛矿物吸附过滤,进一步去除氨氮(NH₄-N)和SS,处理后最终要求TP≤0.2mg/L、NH₄-N≤1.0mg/L、pH6～9、SS≤30mg/L。结果表明,一体化处理系统可使泥饼和余水均达到验收要求,余水处理系统总计可分别减少TP、NH₄-N、SS排放量高达0.99t、6.10t、70.4t,该系统对于水库清淤工程具有一定的推广应用价值。     

CPAM对河道泥水混合物的絮凝效果研究

河道淤泥使水体变黑发臭,严重影响水体环境。近年来,利用清淤船吸取河道底部泥水混合物,然后添加絮凝剂加速泥水分离,从而达到清淤效果的应用研究已初步展开。但絮凝剂投加量对河道泥水混合物絮凝效果的影响尚未有系统的研究,严重影响了清淤船的设计。基于此,通过絮凝实验研究了阳离子型聚丙烯酰胺(CPAM)投加量对泥水混合物分离沉降效果的影响,以及分离后的出水水质。结果表明,当CPAM投加量达到0.79 mg/g时,泥水快速分离效果明显,出水浊度和COD值显著降低。     

钻孔灌注桩废弃泥浆快速泥水分离试验研究

针对钻孔灌注桩在施工过程中产生的大量废弃泥浆问题,在施工现场进行了快速泥水分离试验。首先研究了泥水样品的基本性质,采用配制不同浓度的絮凝剂与废弃泥浆融合试验,得出絮凝剂最佳配合比与泥水分离效果的关系;其次根据新型泥水分离设备工作原理进行了不同类型的泥水分离设备的性能、分离速率以及经济性试验研究;同时,将新型设备的试验结果与传统未经处理的泥浆外运进行综合对比分析。     

疏浚水体底泥再淤积过程研究

为保障疏浚效果的长效性,对疏浚前后底泥的淤积过程进行了模拟研究,并结合淤积过程中底泥性质和上覆水水质的变化,分析了疏浚水体底泥淤积的规律。结果表明,疏浚后底泥的淤积速率大幅提高,可由疏浚前的0.13 mm/d增至0.25 mm/d;疏浚后淤积底泥具有颗粒粒径大、含水率和有机质含量较高的特点;疏浚前后上覆水SS含量的变化不大,发生沉降的固体总量基本不变。由于疏浚前和疏浚后淤积底泥固体总量基本不变,而后者的粒径和含水率要高于前者,故相应的底泥体积和淤积厚度也要高。同时,疏浚后上覆水CODCr含量要高于疏浚前,这可能会导致水体上覆水水质恶化,并加速底泥的淤积。     

絮凝加速吹填土沉积的试验研究

水力吹填疏浚土后,上部泥浆需要一定时间沉积排水晾晒才能加固处理。通过室内试验,对比了疏水剂和高分子絮凝剂、排水条件、泥浆浓度和土体自重对沉积过程的影响,并进行了十万平方米的现场试验。研究表明,加入化学药剂后,泥浆前期沉降速度明显提高,泥水分离时间缩短;后期沉积速度变缓,沉积物强度低;配合一定排水条件可提高泥浆的后期沉积速度和沉积物强度;提高泥浆浓度和土体自重对沉积有一定的作用;利用絮凝技术的化学法加固施工具有可操作性。     

疏浚污泥的电性特征对脱水性能的影响研究

河流、湖泊、水库每年在日常维护中产生大量高含水率的疏浚污泥,借鉴生活污泥的处理方式,石灰常作为调理剂用于疏浚污泥的减量化。由于疏浚污泥与生活污泥性质相差较大,石灰调理的内在机理尚不清楚,并且脱水产物呈强碱性,需要找到替代石灰的调理剂。针对此问题,选用4种不同来源的疏浚污泥,测试石灰的脱水效果、Zeta电位。结果发现石灰均能加速疏浚污泥的快速分离,泥浆颗粒电性的改变是主要原因。氯化铝可以作为石灰替代的调理剂,氯化铝调整了泥浆的电性特征,同样获得了较优的脱水效果,并且脱水产物呈弱酸性,后续产物适合资源化利用。     

药剂真空预压法处理工程废浆试验

将适合于处理大面积高含水率淤泥的真空预压法与用于污水处理的絮凝沉淀法相结合(即药剂真空预压法)应用于工程废浆的固液分离。针对上海某桩基施工现场产生的废弃泥浆采用4种不同的絮凝剂进行了沉降柱试验,并对各自的絮凝效果进行了对比。采用最佳絮凝效果时的絮凝剂和配比,进行了室内药剂真空预压模型试验,试验过程中对出水量和废浆浆面高度进行监测;试验前后进行了含水率、颗粒分布、压汞和扫描电镜试验。试验发现:1废浆含水率从絮凝前的163%,降低到絮凝后的96%,经过真空预压后再降低到37%;2加入絮凝剂后絮体中的黏粒含量减少、粉粒含量增多,即絮凝会使小颗粒长大;3处理后废浆的孔隙率明显下降,沿径向向内逐渐减小。研究表明药剂真空预压法技术可行、效果显著,值得大范围推广。     

工程废浆处理过程中药剂真空预压法的防淤堵机理

选择有机高分子絮凝剂APAM作为药剂,进行室内药剂真空预压处理废浆的模型试验,探讨处理过程中药剂真空预压法的防淤堵机理。试验结果表明：①经药剂真空预压法处理工程废浆含水率由176%降至约40%,而经普通真空预压处理后工程废浆含水率由176%降至135%,药剂真空预压法处理效果非常明显|②药剂真空预压中采用了120μm、180μm和300μm三种不同等效孔径的过滤膜,发现三种过滤膜均能取得较好的效果,且结果相差不大,证明在药剂真空预压中改变等效孔径对防淤堵的影响不明显,其能够防淤堵主要是由于加入药剂改善了废浆性质|③加入药剂APAM后,由于吸附架桥作用土颗粒的粒径会增大而形成絮凝团聚体,在真空预压过程中发挥了很好的防淤堵作用,真空预压结束后连接团聚体的长链会断开,颗粒分布又恢复到接近原始废浆的状态|④常规反滤准则不再适用于药剂真空预压法,这可能与团聚体形状呈不规则的链状有关,仅仅用粒径指标并不能真实反映反滤特性。     

Comparison of the behaviour of various geotextiles used in the filtration of clayey sludge: An experimental study

This paper presents the results of an experimental study of various geotextiles used to filter clayey sludge. The use of geotextiles to filter clayey sludge or suspensions of fine particles in water is more complex than that for filtering suspensions of granular soils. In practice, such applications generally use flocculants to postpone the formation of a low-permeability filter cake. The objective of the present study, which does not use flocculants, is to determine how geotextile characteristics affect the capacity of the geotextile to filter clayey sludge. Three key questions are addressed: (1) What are the main differences between vertical and horizontal filtration? (2) How do geotextile characteristics (nature, opening size, permeability, etc.) affect its capacity to filter clayey sludge (3) How do clayey sludge characteristics (i.e., grain size distribution and concentration)? and the type of flow (i.e., constant head or constant flow) affect the filtering capacity of geotextiles? To evaluate the capacity of a geotextile to filter clayey sludge, we propose three relevant criteria and analyse two filtration phases induced by different cake-formation processes (controlled by the geotextile and controlled by the filter cake). To determine the main differences between vertical and horizontal filtration, the settling of fines in the testing device and its influence on the results are analysed and discussed. This study shows that, for the various clayey sludge tested, the geotextiles (needle-punched nonwoven and thermally bonded nonwoven) with the smallest opening sizes (O₉₀?≤?60?μm) give the most promising results for filtering fines without the use of flocculants. Of these geotextiles, the thermally bonded nonwoven structure seems to offer the best filtration performance for the largest range of fines concentration in the sludge.     

Leachate flow rate behavior through geotextile and soil filters and possible remediation methods

This paper presents flow rate data in the form of system permeability values using various filtration schemes involving both geotextiles and natural soil filters. The tests were conducted over a 20-month period using six different types of leachate. In total, 96 different combinations were evaluated. In all cases, permeabilities decreased over time due to a combination of sediment clogging and/or biological clogging. When a steady state permeability value appeared to be reached, after approximately 6 months, the first of four remediation schemes were attempted. It was seen that water backflush is the most effective in reinstituting high flow rates, followed by backflushing with leachate and nitrogen gas. The least effective remediation scheme was vacuum extraction. Biocide treated geosynthetics were also evaluated, but results were inconclusive. This was due to the long times required and/or the remnants of the micro-organisms which could not pass through the various filtering systems.

The long-term minimum permeability values were not identified, nor were the design required permeabilities for the various landfills, in question. These important items are currently being investigated.     

泥水盾构泥膜形成时开挖面地层孔压变化规律研究

为保证开挖面的稳定，泥水盾构泥水舱中的泥浆必须在开挖面上形成微透水的泥膜，将部分泥浆压力转化为有效应力，泥浆压力才能平衡地层中的土压力和水压力。目前关于泥膜形成时泥浆压力的转化规律及其影响因素尚不清楚。针对这一问题，在自制的泥浆渗透装置中，以12组不同性质的泥浆开展渗透试验，通过测定泥膜形成过程中地层超静孔隙水应力的变化，并分析影响其分布的因素，明确了泥膜的作用机理。结果表明：随着泥膜的形成，泥浆压力在地层中转化为抵抗地层静水压力的孔压、超静孔隙水应力和抵抗地层土压力的有效应力；超静孔隙水应力在泥膜段迅速降低，在地层深处逐渐趋于稳定；泥浆的密度是影响地层超静孔隙水压力分布规律的主要因素之一，泥浆黏度对其影响较小。这一结果对于泥浆压力的设定和泥浆的配制有重要的指导意义。     

Analytical solution on vacuum consolidation of dredged slurry considering clogging effects

This paper aims to establish an analytical model on vacuum consolidation of dredged slurry treated by PVD with special considerations on the clogging effects. A series of laboratory tests have been conducted to characterize the temporal/spatial variations of the clogging zone and the vacuum pressure in soil. Based on the nonlinear relationship between the compressibility, the permeability and the void ratio (e-p and e-k curves), an analytical model incorporating the clogging zone was proposed and solved considering the nonlinear attenuation of the vacuum pressure. The solution was verified and validated by comparing with published data and field test results, respectively. Parametric studies reveal that the clogging significantly slows down the consolidation rate, and thus reduces the final degree of consolidation of the dredged slurry.     

深圳河反滤土工布试验研究

对深圳河治理工程边坡防护反滤运行期的土工布进行了综合试验研究 ,分析了土工布长期运行过程中的渗透性、保土性和淤堵性能 ,从强度损失角度分析了土工布长期运行的强度衰减情况 ,并对土工布的耐久性进行了试验分析。由试验知 ,土工布渗透系数降低约 10 0倍左右 ,而土工布强度降低了 5 0 %左右 ,强度衰减速率小于 0 .2 6% /月。试验表明 ,土工布已进入稳定渗透期和强度的稳定衰减期 ,土工布满足防护反滤的要求     

Apparent clogging effect in vacuum-induced consolidation of dredged soil with prefabricated vertical drains

The improvement efficiency of a dredged slurry by vacuum preloading is greatly affected by the apparent clogging effect arising during the consolidation process, where the apparent clogging effect refers to the combined impacts of filter clogging and particle blinding around the drain due to particle migration and non-uniform consolidation. Three laboratory model tests with different types of soils were performed to investigate the apparent clogging effect. First, the filter clogging effect was investigated by scanning electron microscopy and cross-plane permeability tests. Second, changes in the particle size distribution due to particle migration were analysed at the micro- and macro-levels, and the particle migration induced blinding effect was assessed through the results of the compressibility and permeability tests. The test results indicated negligible particle migration in pure clay and relatively higher blinding effect in mixture soils. Finally, the effects of blinding due to particle migration and non-uniform consolidation on the overall consolidation rate were theoretically quantified. Both the analytical and tests results implied that the apparent clogging effect is predominantly by non-uniform consolidation rather than the particle migration-induced blinding effect, especially for cohesive marine clay.     

A study on biological clogging of nonwoven geotextiles under leachate flow

This paper presents results of long-term permittivity tests using leachate to evaluate biological clogging of nonwoven geotextiles. Three types of geotextiles with varying masses per unit area were used in the tests. The identification and quantification of microorganisms in the geotextile were carried out as well as microscopic investigations. The accuracies of semi-empirical models to evaluate the kinetics of bacteria growth and to correlate hydraulic properties and microbiological parameters were examined. Permittivity tests under increasing water heads were also performed on the geotextile samples already subjected to long-term leachate flow in order to evaluate the values of water heads required to wash the biofilms out of the geotextile pores. The results of the tests showed the marked reduction of geotextile permeability due to biological clogging and that the results of the predictions by semi-empirical methods were consistent with the biological mechanisms observed.