【摘要】：武漢市分布著大量由沖洪積形成的第四系網(wǎng)紋狀紅色黏土,其分布廣泛,被大量用作臨時(shí)公路,建筑場(chǎng)地,水利防滲工程等建筑材料和地基使用。其黏土礦物成分主要為高嶺石和伊利石,并含有少量綠泥石,非黏土礦物主要為石英、云母和長(zhǎng)石。這一類紅色黏土具有中等孔隙性、中等含水量、高塑性、中一低壓縮性,中一微弱膨脹性等特點(diǎn),但是其遇水易軟化,常地基不均勻下沉引起基礎(chǔ)結(jié)構(gòu)斷裂破壞、基坑及邊坡塌方、滑坡等許多工程病害。因此,對(duì)紅色黏土改性的深入研究就顯得十分必要和緊迫。本文采用離子土壤固化劑(ISS)對(duì)紅色黏土進(jìn)行化學(xué)改性,探討改性機(jī)理,指導(dǎo)工程實(shí)踐。ISS是一種復(fù)合型的陰離子表而活性劑,與紅色黏土充分接觸后,與土顆粒表而可交換性陽(yáng)離子和極性水分子進(jìn)行強(qiáng)烈的離子交換,從而土顆粒表面電荷降低,土擴(kuò)散層厚度減薄,水穩(wěn)性提高,強(qiáng)度增加。由此可見(jiàn),離子交換吸附變化是引起土體性質(zhì)改變的一個(gè)首要環(huán)節(jié),陽(yáng)離子交換容量,特別是各主要陽(yáng)離子交換過(guò)程的改變量,是研究ISS固化機(jī)理與評(píng)價(jià)固化效果的重要指標(biāo)。國(guó)內(nèi)外同行在此內(nèi)容的研究中,多針對(duì)紅色黏土擾動(dòng)樣固化的陽(yáng)離子交換前后總量變化與固化效果進(jìn)行比對(duì)分析,但是針對(duì)其原位靜態(tài)加固研究尚未深入的開(kāi)展。對(duì)紅色黏土分布地區(qū)實(shí)施未擾動(dòng)原位加固的研究,具有更為重要的工程實(shí)踐意義。本文通過(guò)自行研制一套基于激光擊穿光譜技術(shù)(LIBS)實(shí)時(shí)在線檢測(cè)的變水頭滲透土柱系統(tǒng),開(kāi)展蒸餾水滲透紅色黏土素土試驗(yàn),了解素土經(jīng)蒸餾水滲透后陽(yáng)離子的基本變化情況；ISS水溶液滲透紅色黏土素土試驗(yàn),對(duì)紅色黏土原位加固的實(shí)驗(yàn)室模擬；蒸餾水滲透ISS改性后的紅色黏土試驗(yàn),驗(yàn)證改性土保持強(qiáng)度的持久性,即ISS改性紅色黏土的不可逆性�！饕_(kāi)展了以下研究工作：(1)在不同交換條件下各主要陽(yáng)離子遷移過(guò)程的探索中,測(cè)試方法是探索研究首要和關(guān)鍵要解決的技術(shù)環(huán)節(jié)。本文首先詳細(xì)介紹了巖土工程常用實(shí)驗(yàn)室測(cè)定陽(yáng)離子交換總量的氯化鋇緩沖液法,但其技術(shù)操作人為干擾因素太多。然后介紹采用等離子體發(fā)射光譜儀(ICP—AES)測(cè)試主要陽(yáng)離子和DX一120型離子色譜儀測(cè)試陰離子的試樣制備,測(cè)定方法,發(fā)現(xiàn)該技術(shù)比傳統(tǒng)實(shí)驗(yàn)室化學(xué)滴定法有很大的改進(jìn),但是預(yù)處理復(fù)雜,而且滿足不了原位檢測(cè)的需求。本文選取國(guó)內(nèi)外先進(jìn)的激光擊穿光譜技術(shù)(LIBS)來(lái)探測(cè)陽(yáng)離子遷移過(guò)程,該技術(shù)可以實(shí)時(shí)、在線、多元素同時(shí)檢測(cè),滿足ISS固化機(jī)理研究中揭示陽(yáng)離子交換過(guò)程的需求,還可以實(shí)現(xiàn)原位檢測(cè),具有非常顯著的優(yōu)勢(shì)。(2)自行搭建一套基于LIBS技術(shù)的變水頭滲透土柱試驗(yàn)系統(tǒng)。①對(duì)試驗(yàn)用土紅色黏土的顆粒連結(jié)特征、粘土礦物的結(jié)晶結(jié)構(gòu)、基本物化性質(zhì),以及土樣制備進(jìn)行了詳細(xì)的介紹。②試驗(yàn)試劑是與水一定體積比的ISS水溶液,本文通過(guò)對(duì)其離子成分的測(cè)試,發(fā)現(xiàn)該ISS是高鈉含量的離子土壤固化劑。③采用較為常用的最大氣泡壓力法對(duì)不同配比下ISS水溶液的表而張力進(jìn)行測(cè)試,結(jié)果顯示ISS溶于水后能迅速降低水的表而張力。④采用FG2梅特勒-托利多便攜式pH計(jì)和FG3梅特勒-托利多便攜式電導(dǎo)率儀對(duì)不同配比下ISS水溶液的PH值與電導(dǎo)率進(jìn)行了測(cè)試,表明ISS水溶液偏酸性,原液具有高的電導(dǎo)性,并且隨ISS水溶液濃度的增加,其電導(dǎo)率也相應(yīng)增大。⑤從加入ISS后紅色黏土塑性指數(shù)的最小值來(lái)確定本文選取的ISS與水的最優(yōu)配比為1：150。(3)通過(guò)開(kāi)展蒸餾水滲透紅色黏土素土試驗(yàn)、ISS水溶液滲透紅色黏土素土試驗(yàn)和蒸餾水滲透ISS改性后的紅色黏土試驗(yàn),得出在不同時(shí)間節(jié)點(diǎn),滲出液中四種主要陽(yáng)離子K+、Na+、Ca2+、Mg2+的離子濃度,從而對(duì)不同滲透條件下陽(yáng)離子遷移過(guò)程進(jìn)行研究,同時(shí)用相應(yīng)滲出液電導(dǎo)率的變化情況來(lái)加以驗(yàn)證。①蒸餾水滲透紅色黏土素土過(guò)程中,黏土礦物孔隙水中的k+、Na+、Ca2+、Mg2+等,在蒸餾水的作用下,紛紛從土柱向滲出液遷移出來(lái),滲出液各陽(yáng)離子濃度逐漸達(dá)到峰值,隨著新的水化環(huán)境下土結(jié)構(gòu)趨于平衡,各離子的濃度逐漸減少,所以整體趨勢(shì)是先增大后減少。②ISS水溶液滲透紅色黏土素土過(guò)程中,首先ISS水溶液中的Na+離子以其濃度的絕對(duì)優(yōu)勢(shì),將黏土顆粒表而的可交換性高價(jià)陽(yáng)離子Ca2+、Mg2+交換出來(lái),其占據(jù)了土顆粒表而的位置,其滲出液中濃度很低,這一階段是外表面平衡階段,時(shí)間比較短；接著是內(nèi)表面平衡階段,時(shí)間比較長(zhǎng),ISS水溶液依靠“親水頭”與紅色黏土顆粒表面所形成的化學(xué)鏈作用,占據(jù)了顆粒表面上的陽(yáng)離子空位,并被吸附在粘土礦物的表面；ISS"疏水尾”圍繞著土顆粒表而形成了一個(gè)油性層,阻止水份進(jìn)入這個(gè)體系。此時(shí)離子交換漸漸緩慢,Ca2+、Mg2+離子濃度慢慢減少,而Na+離子隨著ISS水溶液的滲透濃度慢慢增加。最后,新的水化環(huán)境平衡穩(wěn)定后,黏土顆粒有了穩(wěn)定的滲流渠道,于是后期的各離子濃度將增減到與ISS水溶液中各離子濃度趨于一致。試驗(yàn)結(jié)果初步推斷,ISS水溶液與紅色黏土完全作用的時(shí)間在1-2天左右。③蒸餾水滲透經(jīng)ISS改性過(guò)的紅色黏土過(guò)程中,由于改性后的紅色黏土土表而發(fā)生離子交換的結(jié)合水量明顯減少,離子交換程度減小,交換能力減弱,水化、膨脹和分散能力變?nèi)?形成的結(jié)合水膜厚度減�。煌翆�(duì)新的水化環(huán)境的改變不敏感,土的性質(zhì)不發(fā)生明顯的變化,滲出液中Na+濃度先增加后減小,而K+、Ca2+、Mg2+濃度逐漸降低。④滲出液的電導(dǎo)率能反映其中溶質(zhì)含量的多少。三種滲透方式下,測(cè)得滲出液的電導(dǎo)率的變化趨勢(shì)均呈對(duì)數(shù)正態(tài)分布走勢(shì),先增大,后減少,最后趨于平穩(wěn)值,與各主要陽(yáng)離子濃度變化基本趨勢(shì)是一致的。(4)對(duì)紅色黏土滲透前后進(jìn)行了一系列物理力學(xué)指標(biāo)檢測(cè),檢測(cè)以滲透方式進(jìn)行靜態(tài)固化土強(qiáng)度的持久性,比對(duì)動(dòng)態(tài)固化土的各項(xiàng)指標(biāo),進(jìn)一步檢驗(yàn)固化效果和探索固化機(jī)理。①采用F-Sorb3400比表面積及孔徑測(cè)試儀,試驗(yàn)結(jié)果反映經(jīng)ISS處理后的土顆粒比表而積減小,顆粒粒徑增大。②采用快剪法進(jìn)行了一系列的直接剪切試驗(yàn),蒸餾水滲透經(jīng)ISS攪拌加固過(guò)的紅色黏土的抗剪強(qiáng)度指標(biāo)C較蒸餾水滲透紅色黏土素土和ISS滲透紅色黏土素土的小,而內(nèi)摩擦角大。說(shuō)明ISS水溶液滲透紅色黏土素土,可以有效的減小黏土弱結(jié)合水,降低土的粘性,增加土顆粒之間的接觸面積,增大咬合阻力,使其接觸摩擦力和咬合摩擦力增大,內(nèi)摩擦角增加,土體的抗剪強(qiáng)度有了較大的提高。③開(kāi)展ISS加固紅色黏土前后的脹縮性對(duì)比研究,可以看出,加入ISS后,紅色黏土的自由膨脹率明顯減小,線縮率、體縮、縮限也有不同程度地減小,表明土顆粒之間的連結(jié)力加強(qiáng),土收縮變形能力變小。④利用固結(jié)儀對(duì)蒸餾水滲透紅色黏土素土和ISS滲透紅色黏土素土的壓縮系數(shù)和壓縮模量進(jìn)行了高壓固結(jié)試驗(yàn),結(jié)果顯示經(jīng)過(guò)ISS處理后,紅色黏土的壓縮系數(shù)減小,壓縮模量增大,證明經(jīng)ISS處理后,紅色黏土的孔隙變小,土體變得更密實(shí),土體骨架的堅(jiān)硬性提高,承受外荷載的能力增強(qiáng),抵抗變形的能力提高。⑤開(kāi)展土—水特征曲線研究,發(fā)現(xiàn)紅色黏土素土和ISS改性土樣的基質(zhì)吸力都隨著含水量的降低而增大,并且在較高的基質(zhì)吸力范圍內(nèi),含水量對(duì)土—水特征曲線的影響作用有減小的趨勢(shì)。(5)掃描電鏡試驗(yàn)說(shuō)明ISS滲透作用后土體的礦物粒團(tuán)變大,顆粒之間的膠結(jié)更為緊密,并且排列較為整齊均勻,呈層疊狀,同時(shí)孔隙減少,原來(lái)的大孔隙也被填塞和重新膠結(jié),整個(gè)土體的結(jié)構(gòu)相對(duì)比較穩(wěn)定,土體顆粒吸附結(jié)合水的空間減少,孔隙減少,滲透性降低,力學(xué)性質(zhì)得到增強(qiáng)。(6)從土的微結(jié)構(gòu)變化、土中水的作用、各主要陽(yáng)離子運(yùn)動(dòng)擴(kuò)散方式,再談離子土固化劑的改性機(jī)理。本文通過(guò)實(shí)驗(yàn)室模擬ISS靜態(tài)原位固化紅色黏土的一系列試驗(yàn)研究,充分說(shuō)明紅色黏土是可以通過(guò)滲透這種靜態(tài)的方式進(jìn)行原位加固,加固后的土體具有持久的力學(xué)強(qiáng)度。本文的研究為ISS固化機(jī)理的研究,為ISS原位加固紅色黏土的工程實(shí)踐提供重要的實(shí)驗(yàn)室依據(jù)。
[Abstract]:There are a large number of Quaternary reticulated red clay formed in Wuhan City, which are widely used as temporary highways, building sites and water conservancy projects. The clay minerals are mainly kaolinite and illite, with a small amount of chlorite and non clay minerals mainly quartz, mica and This kind of red clay has the characteristics of medium pore, medium water content, high plasticity, low medium compressibility and medium expansibility, but it is easy to soften in water and often cause failure of foundation structure fracture, foundation pit and slope collapse, landslide and many other engineering diseases. Therefore, deep study on the modification of red clay It is very necessary and urgent. In this paper, the chemical modification of red clay with ionic soil solidifying agent (ISS) is used to study the mechanism of modification and to guide the engineering practice that.ISS is a kind of compound anion table and active agent, after full contact with red clay, strong ions are carried out with the exchangeable cations and polar water molecules with the soil particle surface. By exchange, the surface charge of soil particles is reduced, the thickness of soil diffusion layer is thinner, the stability of water is increased, and the strength of the soil is increased. Therefore, the change of ion exchange adsorption is a primary link in the change of soil properties. The cation exchange capacity, especially the change of the main cation exchange process, is the study of ISS curing mechanism and the evaluation of curing effect. The important index of fruit is the comparison and analysis of the total amount change and curing effect of the red clay disturbed sample before and after the cation exchange, but the research on the static reinforcement in situ has not been further carried out. For the important practical significance of engineering. In this paper, a variable water head permeable soil column system based on laser breakdown spectroscopy (LIBS) was developed in real time. The red clay soil test was carried out in distilled water to understand the basic transformation of the cationic soil after the infiltration of the distilled water. The ISS aqueous solution permeated the red clay soil test. Laboratory simulation of the in-situ reinforcement of red clay; the red clay test after ISS modified by distilled water to verify the durability of the modified soil, that is, the irreversibility of the ISS modified red clay. 'the following research work is carried out: (1) in the exploration of the main cation transfer process under different exchange conditions, the test side In this paper, the barium chloride buffer method for determining the total amount of cation exchange in the laboratory of geotechnical engineering is introduced in detail. However, there are too many human interference factors in its technical operation. Then, the main cation and DX 120 Type 120 type are tested by the plasma emission spectrometer (AES). The ion chromatograph is used to test the sample preparation and the method of determination of anions. It is found that the technology is much better than the traditional laboratory chemical titration, but the preprocessing is complex and can not meet the needs of the in-situ detection. This paper selects advanced laser breakdown spectroscopy (LIBS) to detect the cation transfer process. At the same time, at the same time, on-line and multi elements are simultaneously detected to meet the needs of the cation exchange process in the study of the ISS curing mechanism, and can also be found in situ. (2) a set of test system for the variable head permeable soil column based on LIBS technology is built by ourselves. The crystal structure, the basic physicochemical properties, and the preparation of soil samples are introduced in detail. (2) the test reagents are ISS aqueous solutions to a certain volume of water. Through the test of the ionic composition, this paper found that the ISS is a high sodium content of the ionic soil solidifying agent. (3) the use of the more commonly used maximum bubble pressure method to the ISS aqueous solution under different proportions The test results show that ISS can quickly reduce the water table and tension after water dissolves in water. (4) the pH value and conductivity of the ISS water solution under different proportions are tested by the portable pH meter of FG2 mettle Toledo and the FG3 mettel Toledo portable conductivity meter. It is shown that the ISS water solution is acidic and the original liquid has high conductivity. The conductivity of the ISS water solution increases with the increase of the concentration of water solution. (5) the optimum ratio of the plastic index of red clay after the addition of ISS to determine the optimum ratio of ISS and water is 1:150. (3) by carrying out the red clay soil test of distilled water, the ISS water solution permeates the red clay soil test and the distilled water penetrates IS The red clay test after S modification shows that the ion concentration of four main cations, K+, Na+, Ca2+ and Mg2+ in the exudation solution at different time nodes, is studied under different permeation conditions and verified by the change of the conductivity of the corresponding exudation solution. (1) the distillation water permeates the red clay soil process. K+, Na+, Ca2+, Mg2+ and so on in the pore water of clay minerals are migrated from the soil column to the exudate under the action of distilled water. The concentration of each cation in the exudate gradually reaches the peak. As the soil structure tends to balance in the new hydration environment, the concentration of each ion decreases gradually, so the overall trend is first increasing and then decreasing. (2) the permeability of ISS water solution is permeated. In the process of red clay soil, the Na+ ion in ISS aqueous solution, with its absolute superiority, exchange the exchangeable high valence cationic Ca2+ and Mg2+ of clay particles, which occupies the position of the soil particle surface, and the concentration is very low in the exudation liquid. This stage is the equilibrium phase of the outer surface, and the time is short; then the inner surface is the inner table. In the phase equilibrium phase, the time is long. The ISS water solution depends on the chemical chain of the surface of the red clay particles, which takes up the cation vacancy on the surface of the particles, and is adsorbed on the surface of the clay minerals. The ISS "hydrophobic tail" forms an oiliness layer around the surface of the soil, preventing the water from entering the system. At this time, the ion exchange gradually slows down, the concentration of Ca2+, Mg2+ ions decreases slowly, and the Na+ ion increases slowly with the permeability of the ISS water solution. Finally, after the new hydration environment is balanced and stable, the clay particles have a stable seepage channel, so the ion concentration in the later period will be increased to the same concentration in the ISS aqueous solution. The result preliminarily infer that the time of ISS water solution and red clay fully acts about 1-2 days. (3) when the distilled water permeates the red clay modified by ISS, the binding amount of ion exchange decreases obviously, the degree of ion exchange decreases, the exchange capacity is reduced, the hydration, swelling and dispersing ability of the modified red clay soil surface is reduced. The thickness of the combined water film is thinner and the soil is not sensitive to the change of the new hydration environment. The soil properties do not change obviously. The concentration of Na+ in the exudate is increased first and then decreased, while the concentration of K+, Ca2+ and Mg2+ decreases gradually. 4. The conductivity of the exudate can reflect the amount of the solute in the exudate. The exudation solution is measured under the three infiltration modes. The trend of electrical conductivity changes in the trend of logarithmic normal distribution, which first increases, then decreases, and finally tends to a stable value, which is consistent with the basic trend of the main cation concentration changes. (4) a series of physical and mechanical indexes were tested before and after the infiltration of red clay, and the durability of static solidified soil strength was detected by infiltration method, and the comparison movement was carried out. Various indexes of the solidified soil were used to further examine the curing effect and explore the curing mechanism. (1) using the F-Sorb3400 specific surface area and the pore size tester, the results reflect the decrease in the soil particle ratio after ISS treatment and the increase of particle size. Second, a series of direct shear tests are carried out by fast shear method, and the distilled water penetrates through ISS agitation. The shear strength index of the solid red clay is smaller than that of the distilled water infiltrating red clay soil and ISS infiltrating red clay soil, and the internal friction angle is large. It shows that the infiltration of red clay soil in ISS water solution can effectively reduce the weak cohesive water of clay, reduce the viscosity of the soil, increase the contact area between the soil particles and increase the resistance of the ISS. The contact friction force and the bite friction increase, the internal friction angle increases, the soil shear strength has a greater increase. Thirdly, the expansion and shrinkage comparison study of the red clay reinforced by ISS can be seen that the free expansion rate of the red clay decreases obviously, the line shrinkage, the shrinkage limit and the shrinkage limit decrease to some extent, indicating the soil particles. The compression coefficient and compression modulus of red clay soil in distilled water and the compression modulus of ISS permeated red clay soil were tested by high pressure consolidation test. The results showed that after ISS treatment, the compression coefficient of red clay decreased and the compression modulus increased, which proved to be treated by ISS. After that, the pore of red clay becomes smaller, the soil becomes more dense, the hardness of the soil skeleton is increased, the ability to withstand the external load and the ability to resist deformation increase. 5. The soil water characteristic curve is carried out. The matrix suction of the clay soil and the ISS modified soil samples increases with the decrease of water content and is in the high matrix. In the range of suction, the influence of water content on the soil water characteristic curve is reduced. (5) scanning electron microscope test shows that the mineral particle mass of the soil becomes larger after ISS infiltration, the cementation between particles is more compact, and the arrangement is more uniform, stacked, and the pores are reduced, and the original macropores are stuffed and cemented again. The structure of the whole soil is relatively stable, the space of Soil Particles Adsorbing and combining water decreases, the porosity decreases, the permeability is reduced and the mechanical properties are enhanced. (6) the change of soil microstructure, the effect of water in the soil, the main cation movement diffusion mode, and the modification mechanism of the ionic soil solidifying agent. This paper simulated the static state of ISS static in the laboratory. A series of experimental studies on the in-situ solidification of red clay fully indicate that the red clay can be reinforced in situ by permeating this static way. The soil after reinforcement has a lasting mechanical strength. This study provides an important laboratory basis for the engineering practice of the ISS in situ Reinforcement of red clay for the study of the mechanism of ISS curing.
【學(xué)位授予單位】：中國(guó)地質(zhì)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU446

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