不同电极电渗过程比较及基于电导率电渗排水量计算方法

发布时间：2018-03-12 09:21

本文选题：电极材料　切入点：电渗效果　出处：《浙江大学》2015年博士论文　论文类型：学位论文

【摘要】：我国广泛分布有天然软土地基,近年来蓬勃发展的疏浚工程和吹填工程产生了大量疏浚土和吹填土,这些软土往往含水量高、压缩性大、渗透性低,对其合理加固处理是相应工程成功的关键,传统的基于重力式固结的地基处理方法往往难以达到预期目标。电渗法因其排水速率与土颗粒大小无关,被认为是处理高含水量、低渗透性软土地基很有发展前途的方法,受到广泛关注和研究,但能耗较大、合理设计计算方法的欠缺一直制约着电渗法的推广应用。本文从改善电渗效果、提高电渗效率出发,基于已有文献对于常见电极材料(铁、铜、石墨和铝)电渗效果报道的分歧,从电渗效果和离子迁移两个方面系统地对比了四种电极材料的电渗过程,揭示了电极材料影响电渗过程的本质以及电渗中离子的运移规律；基于已有研究在电渗设计计算方面的欠缺,首次系统地研究了电渗排水速率与电流以及土壤电导率与含水量的关系,提出了基于电导率的电渗排水量计算方法。本文的主要工作及相应成果如下。 (1)分别采用铁和铜电极开展室内试验,比较了阳极和阴极材料影响电渗效果的程度,发现对电渗效果起主导作用的是阳极材料,阴极材料对电渗效果影响不大。 (2)在三种不同的电势梯度下分别采用铁、铜、石墨和铝电极开展电渗试验,分析了常规电极材料的电渗表现和电极材料的作用机制,得到：较高电势梯度下石墨电极表现较好,而较低电势梯度下石墨电极表现不如铁或铜电极,铜电极存在阳极钝化现象,而石墨电极易于分解；Fe2+/Fe3+和Cu2+迁移能力较差,阳极反应生成的Fe2+/Fe3+和Cu2+大多数聚集在阳极附近,少部分迁移到阴极的离子在碱性环境下生成沉淀；A13+迁移能力较强,阳极反应生成的A13+在电场作用下大多运移到阴极随水排出,少量A13+因阴极碱性环境产生沉淀滞留在阴极附近；电极材料对电渗过程的主要作用在于通过电极腐蚀、阳极钝化、分解以及电极与土体部分脱离引起电势损失,其通过电极反应生成离子进入土壤随电场迁移对电渗的促进甚小。 (3)采用铁、铜、石墨和铝电极开展电渗试验,监测了电渗排水和重力排水中多种元素含量(Na、K、Mg、Ca、Fe、Cu和Al)变化和土壤经电渗加固前后的元素含量变化,得出电渗过程中水分的转移主要依赖Na+、K+、Mg2+、Ca2+和A13+等迁移能力较强的离子,低阶、小原子量离子受约束力较小、迁移能力较强,其带动水分子的迁移是决定电渗法效果的关键。基于试验结果分析了电渗运移量随时间以及电导率随含水量的变化情况,发现电渗运移量在主要电渗排水阶段基本保持恒定,而电导率与含水量也存在近似线性关系。 (4)根据已有文献资料中的大量试验数据,首次系统揭示了土壤类型、含水量、电势梯度和电极布置形式对电渗运移量的影响,发现不同土壤类型的排水速率与电流均呈现出较好的近似线性比例关系,但不同土壤类型的电渗运移量相差较大,对于同一种土壤类型,电渗运移量主要、含水量、含盐量等内因影响,电极布置形式、电势梯度等外因对电渗运移量直接影响较小。 (5)系统总结了已有研究中电导率与含水量的理论模型和经验公式,提出了三种经验关系,即线性关系、指数关系和二次函数关系。依据电渗排水速率与电流的发展规律以及电导率与含水量的经验关系、考虑了电渗过程中土体性质的变化,提出了基于电导率的一维电渗排水量计算方法。根据室内试验结果将该方法与传统的基于Esrig的方法进行比较,结果表明该方法对电渗排水量的预测准确性远高于已有的基于Esrig理论的方法。 (6)研究了堆载对电渗运移量和电导率的影响,得到堆载作用下电渗排水速率随电流的发展规律以及电导率与含水量的经验关系,进而推导堆载作用下基于电导率的一维电渗排水量计算方法；推导电极轴对称布置时土壤的电导率公式,进而对轴对称电渗排水量计算公式进行了理论推导和试验验证；将基于电导率的电渗排水量计算方法推广到二维情况,得到堆载作用下基于电导率的二维电渗排水量计算公式。 (7)对基于电导率的电渗排水量计算方法的工程应用进行了研究。探讨了电渗排水量与土体收缩量的关系,指出单独采用电渗法加固软土时,电渗排水量数值上比土体收缩量大,二者的差值可以通过施加外荷载予以减小,强调了电渗排水量数值预测土体收缩量的安全性。给出了计算中涉及到参数的合理设计意见,并提出了该方法的应用路线和适用条件,以期为具体工程应用提供指导。
[Abstract]:Our country wide distribution of natural soft soil foundation, with the rapid development of dredging and reclamation works to produce a lot of dredged soil and hydraulic fill, the soft soil usually high water content, high compressibility, low permeability, the reasonable reinforcement is the key to success of the corresponding project, the traditional method of foundation treatment based on gravity consolidation is often difficult to reach the expected goal. Because of the electroosmosis rate of drainage and soil particle size, is considered to be the treatment of high water content, low permeability of soft soil foundation is very promising, attracted widespread attention and research, but the energy consumption is large, the lack of reasonable design calculation method has been restricting promotion the application of electroosmosis method.
In order to improve the electro osmotic effect, improve the efficiency of the existing literature on electroosmosis, based on the common electrode materials (iron, copper, graphite and aluminum) electro osmotic effect reported differences from the electro osmotic effect and ion mobility two aspects systematically compared the electroosmosis process of four kinds of electrode material, electrode material reveals the nature of the process and effect of electroosmosis electroosmosis ions in migration; the lack of existing research in computational design based on electroosmosis, was studied systematically for the first time with the current rate of electroosmotic drainage and soil conductivity and water content, puts forward the calculation method based on the amount of electro conductivity. The main work of this paper and the corresponding results are as follows.
(1) using iron and copper electrodes to carry out indoor tests respectively, the effect of anode and cathode materials on electroosmosis is compared. It is found that anode materials play a leading role in electroosmosis, and cathode materials have little effect on electroosmosis.
(2) in three different potential gradient respectively by iron, copper, aluminum and graphite electrode in electro osmosis test, analysis of the mechanism of action, the conventional electrode material and electrode material by electroosmosis: high potential gradient of graphite electrode performed better, while the lower potential gradient as the performance of iron or graphite electrode the copper electrode, the copper electrode is the anode passivation phenomenon and graphite electrode easy decomposition; Fe2+/Fe3+ and Cu2+ migration ability is poor, the anode reaction of Fe2+/Fe3+ and Cu2+ most gathered in the vicinity of the anode to the cathode of the ion migration less precipitation in alkaline environment; A13+ migration ability, anodic reaction of A13+ under the electric field. Most of the migration to the cathode discharge with water, a small amount of A13+ for cathode deposition and retention in the alkaline environment near the cathode; the main effect of electrode materials on Electro osmotic process is through the electrode corrosion Erosion, anode passivation, decomposition and separation of electrode and soil lead to loss of electric potential. It generates ions into the soil through electrode reaction, and promotes the electroosmosis with the migration of electric field.
(3) the iron, copper, aluminum and graphite electrode in electro osmosis test, a variety of elements content in the electro osmotic drainage and gravity drainage monitoring (Na, K, Mg, Ca, Fe, Cu and Al) and the changes of soil by electroosmosis element content before and after reinforcement, the water transfer process mainly depends on the Na+ electroosmosis K+, Mg2+, Ca2+ and A13+, ion, strong ability of migration in low order, small atomic weight by ion binding is small, strong migration ability, drive the migration of water molecules is the key to determine the effect of electroosmosis method. The experimental results were analyzed with time and conductivity of electroosmotic transport changes with water content based on that the amount of migration in the main electroosmotic electroosmotic drainage stage is kept constant, while the electrical conductivity and water content are approximately linear.
(4) according to the existing experimental data in the literature for the first time, the system reveals the soil type, moisture content, and the effect of potential gradient electrode layout on the electroosmotic transport rate, drainage rate and current found in different soil types showed a good linear relationship with ratio, but the difference between different soil types electroosmotic transport rate the larger, for the same soil type, moisture migration quantity of main electro osmotic, salt content, internal factors, electrode arrangement, potential gradient and other external factors on the electroosmotic migration is directly related to the amount of small.
(5) summarizes the studies on the conductivity and water content of theoretical model and empirical formula, puts forward three kinds of empirical relations, namely linear, exponential relationship and quadratic function relationship. According to the rule of development rate and current electroosmotic drainage and conductivity and water content of experience, taking into account the change of properties of soil electroosmosis in the process of calculation is proposed based on one-dimensional electroosmotic drainage volume conductivity method. According to the test results of this method and the traditional Esrig based methods are compared, the results show that the prediction of the amount of electroosmotic drainage accuracy is much higher than the existing method based on Esrig theory.
(6) study the loading effect on electroosmotic migration capacity and electric conductivity, get loading rate variation with the current electroosmotic drainage and conductivity and water content of empirical relations, and then derive the loading displacement based on one-dimensional electroosmotic conductivity calculation method; soil conductivity formula derivation of electrode axis symmetric arrangement then, for the axisymmetric electro osmotic drainage calculation formula of theoretical derivation and experimental verification; the amount of electroosmotic drainage based on the conductivity calculation method is extended to two-dimensional case, obtained the bulk formula of two dimensional displacement electro osmotic conductance based on load.
(7) the engineering calculation method based on the amount of electro conductivity were studied. The relationship between electroosmotic drainage shrinkage and soil mass, pointed out separately using electroosmosis method to reinforce soft soil, numerical electroosmotic drainage quantity than the soil shrinkage, the difference between the two can be reduced by loading. Emphasize the safety prediction of soil shrinkage value. The rational design of electro osmotic drainage comments related to the calculation of parameters are given, and put forward the route of application of the method and the applicable conditions, in order to provide guidance for the engineering application.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU447

【参考文献】