【摘要】：電滲加固技術(shù)可以對(duì)高含水量、低滲透性的軟粘土進(jìn)行高效快速的排水固結(jié),具有廣泛的應(yīng)用前景。本文總結(jié)了電滲加固技術(shù)的研究現(xiàn)狀,開(kāi)展電滲固結(jié)模型試驗(yàn),深入了解軟土地基電滲固結(jié)的宏觀規(guī)律和微觀特性;完善電滲固結(jié)理論模型,發(fā)展數(shù)值計(jì)算方法,促進(jìn)電滲固結(jié)技術(shù)的推廣應(yīng)用。建立一套電滲加固模型試驗(yàn)系統(tǒng),實(shí)時(shí)監(jiān)測(cè)土體電滲加固過(guò)程中的宏觀物理量時(shí)空變化,對(duì)電滲前后的土樣測(cè)量分析其物理化學(xué)性質(zhì)、測(cè)試其微觀結(jié)構(gòu)和礦物成分變化特性。實(shí)時(shí)監(jiān)測(cè)的物理量包括出水量、電勢(shì)、電流、土體位移、p H值等;測(cè)試分析的土體特性包括含水量、液塑限、自由膨脹率、zeta電位、陽(yáng)離子交換量,以及微觀結(jié)構(gòu)、化學(xué)成分和礦物成分。電滲加固模型試驗(yàn)表明初始含水量和電極材料影響電滲排水過(guò)程,電滲作用會(huì)改變土體物理化學(xué)性質(zhì)。高嶺土的電滲試驗(yàn)結(jié)果說(shuō)明,初始含水量越高,最終排水比例越大,間歇通電效果越明顯。鈉基膨潤(rùn)土的試驗(yàn)結(jié)果表明,活性電極的電滲排水效果比惰性電極好,電滲作用使得陽(yáng)極處膨潤(rùn)土的塑性指數(shù)和自由膨脹率減小,可以有效抑制膨潤(rùn)土的脹縮特性。微觀測(cè)試表明電滲過(guò)程導(dǎo)致膨潤(rùn)土微觀結(jié)構(gòu)和礦物成分發(fā)生顯著變化,是其物理化學(xué)性質(zhì)改變的根本原因。電滲后,陽(yáng)極附近膨潤(rùn)土樣的微觀結(jié)構(gòu)從絮狀結(jié)構(gòu)變?yōu)轭w粒堆積結(jié)構(gòu),孔隙比減小,土樣更加密實(shí);粘土顆粒表面雙電層中和晶層內(nèi)的鈉離子被替換,導(dǎo)致雙電層厚度減小,晶層間聯(lián)結(jié)力增強(qiáng)。這些微觀特性的改變進(jìn)一步導(dǎo)致粘土顆粒吸水能力減弱,因此塑性指數(shù)和自由膨脹率減小。試驗(yàn)結(jié)果同時(shí)說(shuō)明,鈉離子是鈉基膨潤(rùn)土電滲排水過(guò)程中最主要的微觀作用離子。發(fā)展和完善考慮土體參數(shù)非線性變化的多場(chǎng)耦合理論,反映土體電滲固結(jié)過(guò)程中滲流場(chǎng)、應(yīng)力位移場(chǎng)和電場(chǎng)的時(shí)空變化特征。研究簡(jiǎn)化模型的解析理論,推導(dǎo)得到孔壓和固結(jié)度的解析表達(dá)式,提出沉降計(jì)算公式,繪制電極間距、沉降和土體電滲參數(shù)之間的關(guān)系圖,可用于指導(dǎo)工程設(shè)計(jì)。發(fā)展數(shù)值計(jì)算模型,與解析理論和試驗(yàn)結(jié)果對(duì)比驗(yàn)證其合理性;利用該數(shù)值模型,針對(duì)復(fù)雜工況問(wèn)題和工程實(shí)例進(jìn)行計(jì)算分析,結(jié)果表明該模型能合理描述土體電滲固結(jié)過(guò)程中位移、孔壓、應(yīng)力等物理量的發(fā)展變化過(guò)程。
[Abstract]:Electroosmotic reinforcement technology can be used for high water content and low permeability soft clay for high efficiency and fast drainage consolidation, which has a wide application prospect. In this paper, the research status of electroosmotic consolidation technology is summarized, the electroosmotic consolidation model test is carried out, the macroscopic and microscopic characteristics of electroosmotic consolidation of soft soil are deeply understood, the theoretical model of electroosmotic consolidation is improved, and the numerical calculation method is developed. To promote the popularization and application of electroosmotic consolidation technology. A set of electroosmotic reinforcement model test system was set up to monitor the time and space change of macroscopic physical quantity in the process of soil electroosmotic reinforcement in real time. The physical and chemical properties of soil samples before and after electroosmosis were measured and their microstructure and mineral composition characteristics were tested. The physical parameters of real-time monitoring include water output, electric potential, current, soil displacement and pH value, etc. The soil properties measured and analyzed include water content, liquid plastic limit, free expansion rate and Zeta potential, cation exchange capacity, and microstructure. Chemical and mineral composition. The model test of electroosmotic reinforcement shows that the initial water content and electrode material affect the process of electroosmotic drainage and the electroosmotic effect will change the physical and chemical properties of soil. The results of electroosmotic test of kaolin show that the higher the initial water content, the larger the final drainage ratio, and the more obvious the intermittent electrification effect is. The experimental results of sodium bentonite show that the electroosmotic drainage effect of the active electrode is better than that of the inert electrode, and the plastic index and the free expansion rate of the bentonite at the anode can be reduced by the electroosmotic action, which can effectively inhibit the swelling and shrinkage characteristics of the bentonite. Microscopic tests show that the electroosmotic process leads to significant changes in microstructure and mineral composition of bentonite, which is the fundamental reason for the change of physical and chemical properties of bentonite. After electroosmosis, the microstructure of bentonite samples near the anode changed from flocculent structure to granular stacking structure, the porosity ratio decreased and the soil sample became more dense, and the sodium ions in the double electric layer and the crystal layer on the surface of clay particles were replaced, which resulted in the decrease of the thickness of the double electric layer. The intergranular bonding force is enhanced. The changes of these microscopic properties further weaken the water absorption ability of clay particles, so the plasticity index and free expansion ratio decrease. The results also show that sodium ion is the most important microcosmic ion in the electroosmotic drainage process of sodium bentonite. The multi-field coupling theory, which takes into account the nonlinear variation of soil parameters, is developed and perfected to reflect the space-time variation characteristics of seepage field, stress-displacement field and electric field in the process of soil electroosmotic consolidation. The analytical theory of the simplified model is studied and the analytical expressions of pore pressure and degree of consolidation are derived. The calculation formula of settlement is put forward, and the relationship diagram between electrode spacing, settlement and electroosmotic parameters of soil is drawn, which can be used to guide engineering design. The numerical calculation model is developed and compared with the analytical theory and experimental results to verify its rationality, and the numerical model is used to calculate and analyze the complex working conditions and engineering examples. The results show that the model can reasonably describe the development of displacement, pore pressure and stress in the process of soil electroosmotic consolidation.
【學(xué)位授予單位】：清華大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU472

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