發(fā)布時間：2018-03-12 09:21

  本文選題：電極材料　切入點：電滲效果　出處：《浙江大學》2015年博士論文　論文類型：學位論文

【摘要】：我國廣泛分布有天然軟土地基,近年來蓬勃發(fā)展的疏浚工程和吹填工程產生了大量疏浚土和吹填土,這些軟土往往含水量高、壓縮性大、滲透性低,對其合理加固處理是相應工程成功的關鍵,傳統(tǒng)的基于重力式固結的地基處理方法往往難以達到預期目標。電滲法因其排水速率與土顆粒大小無關,被認為是處理高含水量、低滲透性軟土地基很有發(fā)展前途的方法,受到廣泛關注和研究,但能耗較大、合理設計計算方法的欠缺一直制約著電滲法的推廣應用。 本文從改善電滲效果、提高電滲效率出發(fā),基于已有文獻對于常見電極材料(鐵、銅、石墨和鋁)電滲效果報道的分歧,從電滲效果和離子遷移兩個方面系統(tǒng)地對比了四種電極材料的電滲過程,揭示了電極材料影響電滲過程的本質以及電滲中離子的運移規(guī)律；基于已有研究在電滲設計計算方面的欠缺,首次系統(tǒng)地研究了電滲排水速率與電流以及土壤電導率與含水量的關系,提出了基于電導率的電滲排水量計算方法。本文的主要工作及相應成果如下。 (1)分別采用鐵和銅電極開展室內試驗,比較了陽極和陰極材料影響電滲效果的程度,發(fā)現(xiàn)對電滲效果起主導作用的是陽極材料,陰極材料對電滲效果影響不大。 (2)在三種不同的電勢梯度下分別采用鐵、銅、石墨和鋁電極開展電滲試驗,分析了常規(guī)電極材料的電滲表現(xiàn)和電極材料的作用機制,得到：較高電勢梯度下石墨電極表現(xiàn)較好,而較低電勢梯度下石墨電極表現(xiàn)不如鐵或銅電極,銅電極存在陽極鈍化現(xiàn)象,而石墨電極易于分解；Fe2+/Fe3+和Cu2+遷移能力較差,陽極反應生成的Fe2+/Fe3+和Cu2+大多數聚集在陽極附近,少部分遷移到陰極的離子在堿性環(huán)境下生成沉淀；A13+遷移能力較強,陽極反應生成的A13+在電場作用下大多運移到陰極隨水排出,少量A13+因陰極堿性環(huán)境產生沉淀滯留在陰極附近；電極材料對電滲過程的主要作用在于通過電極腐蝕、陽極鈍化、分解以及電極與土體部分脫離引起電勢損失,其通過電極反應生成離子進入土壤隨電場遷移對電滲的促進甚小。 (3)采用鐵、銅、石墨和鋁電極開展電滲試驗,監(jiān)測了電滲排水和重力排水中多種元素含量(Na、K、Mg、Ca、Fe、Cu和Al)變化和土壤經電滲加固前后的元素含量變化,得出電滲過程中水分的轉移主要依賴Na+、K+、Mg2+、Ca2+和A13+等遷移能力較強的離子,低階、小原子量離子受約束力較小、遷移能力較強,其帶動水分子的遷移是決定電滲法效果的關鍵�；谠囼灲Y果分析了電滲運移量隨時間以及電導率隨含水量的變化情況,發(fā)現(xiàn)電滲運移量在主要電滲排水階段基本保持恒定,而電導率與含水量也存在近似線性關系。 (4)根據已有文獻資料中的大量試驗數據,首次系統(tǒng)揭示了土壤類型、含水量、電勢梯度和電極布置形式對電滲運移量的影響,發(fā)現(xiàn)不同土壤類型的排水速率與電流均呈現(xiàn)出較好的近似線性比例關系,但不同土壤類型的電滲運移量相差較大,對于同一種土壤類型,電滲運移量主要、含水量、含鹽量等內因影響,電極布置形式、電勢梯度等外因對電滲運移量直接影響較小。 (5)系統(tǒng)總結了已有研究中電導率與含水量的理論模型和經驗公式,提出了三種經驗關系,即線性關系、指數關系和二次函數關系。依據電滲排水速率與電流的發(fā)展規(guī)律以及電導率與含水量的經驗關系、考慮了電滲過程中土體性質的變化,提出了基于電導率的一維電滲排水量計算方法。根據室內試驗結果將該方法與傳統(tǒng)的基于Esrig的方法進行比較,結果表明該方法對電滲排水量的預測準確性遠高于已有的基于Esrig理論的方法。 (6)研究了堆載對電滲運移量和電導率的影響,得到堆載作用下電滲排水速率隨電流的發(fā)展規(guī)律以及電導率與含水量的經驗關系,進而推導堆載作用下基于電導率的一維電滲排水量計算方法；推導電極軸對稱布置時土壤的電導率公式,進而對軸對稱電滲排水量計算公式進行了理論推導和試驗驗證；將基于電導率的電滲排水量計算方法推廣到二維情況,得到堆載作用下基于電導率的二維電滲排水量計算公式。 (7)對基于電導率的電滲排水量計算方法的工程應用進行了研究。探討了電滲排水量與土體收縮量的關系,指出單獨采用電滲法加固軟土時,電滲排水量數值上比土體收縮量大,二者的差值可以通過施加外荷載予以減小,強調了電滲排水量數值預測土體收縮量的安全性。給出了計算中涉及到參數的合理設計意見,并提出了該方法的應用路線和適用條件,以期為具體工程應用提供指導。
[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.

【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU447

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