本文選題：軟土 + 滲流特性��； 參考：《華南理工大學(xué)》2014年博士論文

【摘要】：軟土廣泛分布于沿海、河流中下游及湖泊的三角洲地區(qū),一般具有高含水量、大孔隙、低強(qiáng)度、高壓縮性、低滲透性、結(jié)構(gòu)性和流變性等特點(diǎn),其工程力學(xué)性狀復(fù)雜且工程性質(zhì)差,軟土的滲透固結(jié)特性是土工建設(shè)工程中不可回避的問題之一。土的力學(xué)性質(zhì)從本質(zhì)上來說是取決于其微結(jié)構(gòu),土的微孔隙特征是研究土體微結(jié)構(gòu)的重要內(nèi)容,土體孔隙的結(jié)構(gòu)形態(tài)特征與土的滲透固結(jié)特性關(guān)系密不可分。本文基于試驗(yàn)從微觀的角度研究了軟土的孔隙結(jié)構(gòu)特征及其與滲透固結(jié)特性的關(guān)系。本文研究的對(duì)象包括極細(xì)顆粒人工土和珠江三角洲地區(qū)的軟土。采用的宏觀試驗(yàn)方法有固結(jié)滲透試驗(yàn)、常水頭滲透試驗(yàn)和變水頭滲透試驗(yàn),微觀試驗(yàn)方法以壓汞試驗(yàn)(MIP)為主、還包括掃描電鏡試驗(yàn)(SEM)、X射線衍射(LD)、激光衍射法試驗(yàn)(XRD)、氣體吸附法(BET)、乙二醇乙醚吸附法(EGME)等。本文開展的研究工作和取得的成果有如下幾個(gè)方面:(1)研究了土體微觀試驗(yàn)脫水過程中冷凍干燥法、烘干法和風(fēng)干法對(duì)軟土孔隙結(jié)構(gòu)的影響,為微觀試驗(yàn)分析奠定了基礎(chǔ)。對(duì)于含水率大、高塑性的天然軟土應(yīng)使用冷凍干燥法干燥。(2)試驗(yàn)驗(yàn)證了用壓汞試驗(yàn)獲得軟土比表面積的可行性與可靠性,因此可以在獲得土體孔隙分布特征的同時(shí)獲得土體的比表面積,簡化了試驗(yàn)。(3)定量研究了軟土固結(jié)滲透過程中孔隙分布結(jié)構(gòu)的變化,發(fā)現(xiàn)在軟土固結(jié)滲透過程中孔隙直徑小于100nm的小孔隙含量與分布不變規(guī)律,滲透固結(jié)改變的主要是孔隙直徑在100nm和10000nm之間的中孔隙含量和分布,并從微觀孔隙的角度對(duì)這一現(xiàn)象進(jìn)行了機(jī)理分析與探討;(4)用壓汞試驗(yàn)測試分析了大量不同成分、孔隙比、含水率、飽和度的人工軟土以及珠江三角洲天然軟土孔隙分布特征。壓汞試驗(yàn)結(jié)果表明軟土孔隙特征的多樣性,因此工程中采用的表達(dá)土的孔隙含量的宏觀參數(shù)孔隙比并不能完整描述軟土的孔隙特征,需要引入其他微觀參數(shù)對(duì)軟土的孔隙特征進(jìn)行描述。(5)統(tǒng)計(jì)分析了人工土和天然軟土的孔隙結(jié)構(gòu)特征參數(shù)和滲透系數(shù)的關(guān)系。根據(jù)試驗(yàn)結(jié)果和理論分析把土中孔隙分類為小孔隙(D≤100nm)、中孔隙(100nmD≤10000nm)和大孔隙(D10000nm)。統(tǒng)計(jì)分析表明,滲透系數(shù)與壓汞孔隙比、中孔隙體積絕對(duì)含量沒有相關(guān)性或弱相關(guān),與小孔隙體積絕對(duì)含量呈現(xiàn)中等相關(guān),與比表面積呈現(xiàn)中等相關(guān)或強(qiáng)相關(guān),與平均孔徑和大孔隙體積絕對(duì)含量強(qiáng)相關(guān)。(6)從微觀孔隙結(jié)構(gòu)的角度探討了滲透固結(jié)的機(jī)理,提出小孔隙孔隙比、中孔隙孔隙比、大孔隙孔隙比和有效孔隙比概念與假設(shè)。基于K-C模型,根據(jù)有效孔隙比假設(shè)重新推導(dǎo)了考慮微觀孔隙特征的修正的K-C模型。經(jīng)過試驗(yàn)驗(yàn)證,相對(duì)于傳統(tǒng)的K-C模型,修正的K-C模型更加適合珠江三角洲地區(qū)軟土。
[Abstract]:Soft soil is widely distributed in coastal, middle and lower reaches of rivers and deltas of lakes. It is generally characterized by high water content, large porosity, low strength, high compressibility, low permeability, structural and rheological properties, etc. The engineering mechanical properties are complex and the engineering properties are poor. The permeability and consolidation of soft soil is one of the unavoidable problems in geotechnical engineering. The mechanical properties of soil are essentially determined by its microstructure. The characteristics of soil micropores are an important part of the study of soil microstructures. The structural and morphological characteristics of soil pores are closely related to the permeability and consolidation characteristics of soil. Based on the experiments, the pore structure characteristics of soft soil and its relationship with permeability and consolidation characteristics are studied from the microscopic point of view. The objects of study in this paper include very fine grained artificial soil and soft soil in the Pearl River Delta region. The macroscopical test methods are consolidation permeation test, constant head permeation test and variable head permeation test, and the microcosmic test methods are mercury injection test (MIP). It also includes scanning electron microscopy (SEM), X-ray diffraction (LDN), laser diffraction (XRDX), gas adsorption (et), ethylene glycol (EG) adsorption, and so on. The research work and the results obtained in this paper are as follows: 1) the effects of freeze-drying, drying and air-drying on the pore structure of soft soil are studied in the process of soil micro-test dehydration, which lays a foundation for micro-test analysis. For the natural soft soil with high moisture content and high plasticity, the freeze-drying method should be used to dry. 2) the feasibility and reliability of using mercury injection test to obtain the specific surface area of soft soil are verified. Therefore, the pore distribution characteristics of soil can be obtained, and the specific surface area of soil can be obtained, and the change of pore distribution structure during consolidation and permeation of soft soil can be quantitatively studied by simplified test. It is found that in the process of consolidation and permeability of soft soil, the pore content and distribution of the pore diameter is smaller than that of 100nm, and the change of pore diameter between 100nm and 10000nm is the main change of pore content and distribution. The mechanism of this phenomenon is analyzed and discussed from the point of view of micro-porosity. The pore distribution characteristics of a large number of artificial soft soil with different components, void ratio, water content, saturation and natural soft soil in the Pearl River Delta are analyzed by mercury injection test. The results of mercury injection test show that the diversity of pore characteristics of soft soil, so the macro parameter porosity ratio, which is used to express the pore content of soft soil, can not describe the pore characteristics of soft soil completely. The relationship between pore structure characteristic parameters and permeability coefficient of artificial soil and natural soft soil is analyzed statistically. According to the experimental results and theoretical analysis, the pores in the soil are classified as small porosity D 鈮，

本文編號(hào)：1963126