本文選題：珠江三角洲軟土 + 滲流固結(jié)特性　； 參考：《華南理工大學(xué)》2013年博士論文

【摘要】：珠江三角洲地區(qū)廣泛分布著厚度幾米至幾十米的全新世海積形成的軟土層，主要為淤泥、粉砂質(zhì)淤泥和黏土，具有含水量高、孔隙比大、壓縮性高、強(qiáng)度低、滲透性差、結(jié)構(gòu)性和流變性顯著等特點(diǎn)而導(dǎo)致地基沉陷和失穩(wěn)等重大工程事故。為提高軟土地基的工程質(zhì)量，減少工程施工事故，需要深入研究軟土的工程特性，提高軟土地基的設(shè)計(jì)和施工水平。但長(zhǎng)期以來(lái)，人們主要從宏觀層次對(duì)軟土的工程特性進(jìn)行研究，難于抓住決定軟土性質(zhì)的本質(zhì)因素從而對(duì)其工程特性作出深刻研究。因此，從土體的微觀結(jié)構(gòu)分析入手研究軟土工程性質(zhì)是一種“尋根溯源”的方法，可以從本質(zhì)上深刻了解軟土的工程特性。 本文以珠江三角洲天然土(或重塑土)為研究對(duì)象，從統(tǒng)計(jì)學(xué)角度研究珠江三角洲軟土區(qū)域特征及工程性質(zhì)，并結(jié)合礦物成分試驗(yàn)、ESEM試驗(yàn)、壓汞試驗(yàn)研究軟土滲流固結(jié)過(guò)程中微觀結(jié)構(gòu)因素(如顆粒形狀、分布、排列和連結(jié)方式、微顆粒聚合體的形態(tài)、孔隙數(shù)量、孔隙形態(tài)、尺度及分布、連通性及曲折性等)的變化特征與分形特征，將軟土的微觀參數(shù)與宏觀工程性質(zhì)結(jié)合，解釋影響軟土特性的微觀機(jī)制。最后，提出了基于微觀試驗(yàn)的修正固結(jié)模型，通過(guò)實(shí)測(cè)結(jié)果證實(shí)了模型的合理性和有效性。 本文得到的主要研究成果和結(jié)論如下： (1)通過(guò)對(duì)珠江三角洲軟土成因的地質(zhì)與水文環(huán)境、礦物成分、顆粒特征、微觀特征等區(qū)域特性分析，發(fā)現(xiàn)其特殊的宏觀工程特性主要由微細(xì)觀因素決定。利用“偏度、峰度檢驗(yàn)法”研究了珠江三角洲軟土物理力學(xué)指標(biāo)的分布規(guī)律，為今后該地區(qū)開(kāi)展軟土工程提供借鑒。 (2)與全局閾值分割法相比，局部閾值分割法得到的孔隙比結(jié)果與實(shí)際更接近。將顯微結(jié)構(gòu)二值化定量分析的閥值選擇與微孔隙特征測(cè)試、三相圖計(jì)算相匹配的方法，解決目前微觀試驗(yàn)結(jié)果定量分析中的過(guò)渡離散性和人為干擾問(wèn)題，改善現(xiàn)有微觀試驗(yàn)的可靠性和準(zhǔn)確性。 (3)固結(jié)過(guò)程中，軟土微結(jié)構(gòu)類型逐步發(fā)生變化，由蜂窩結(jié)構(gòu)(海綿結(jié)構(gòu))逐漸向骨架結(jié)構(gòu)、紊流結(jié)構(gòu)、密實(shí)結(jié)構(gòu)轉(zhuǎn)化，其連接方式由邊-邊，邊-面連接向面-面連接轉(zhuǎn)化，結(jié)構(gòu)單元體面積明顯增加，孔隙減��；重塑土顆粒由于缺乏結(jié)構(gòu)性，揉合在一起，以聚合體為主，呈凝塊狀結(jié)構(gòu)，相對(duì)密實(shí)，隨著荷載的增加，顆粒單元體以面-面連接方式為主。 (4)結(jié)構(gòu)單元體及孔隙的微觀結(jié)構(gòu)定量化參數(shù)在固結(jié)的不同階段具有不同的規(guī)律。在固結(jié)前期，當(dāng)有效應(yīng)力較小時(shí)，由于淤泥土具有一定的結(jié)構(gòu)強(qiáng)度，微觀結(jié)構(gòu)處于穩(wěn)定調(diào)整階段，孔隙數(shù)量較少，孔隙比較大，以大、中孔隙為主，結(jié)構(gòu)單元體和孔隙的大小、形態(tài)和定向性等變化幅度均較小；當(dāng)有效應(yīng)力增至結(jié)構(gòu)屈服應(yīng)力時(shí)，結(jié)構(gòu)逐漸破壞，團(tuán)聚體破碎，微觀結(jié)構(gòu)處于再造劇烈調(diào)整階段，結(jié)構(gòu)單元體等效直徑明顯增大，，圓形度和平均形狀系數(shù)顯著減小，有變狹長(zhǎng)趨勢(shì)并在垂直于壓力方向形成明顯的定向排列。此時(shí)，孔隙數(shù)量明顯增加，等效孔徑不斷變小，形態(tài)變得更為復(fù)雜，孔隙分布由中、小孔隙向小、微孔隙甚至超微孔隙發(fā)展，但定向性變化不明顯；當(dāng)有效應(yīng)力繼續(xù)增大時(shí)，新的微觀結(jié)構(gòu)作適當(dāng)調(diào)整，結(jié)構(gòu)單元體與孔隙的定量化參數(shù)變化多趨于平緩。 (5)珠江三角洲天然軟土(或重塑土)的結(jié)構(gòu)單元體和孔隙均具有明顯的分形結(jié)構(gòu)特征。綜合反映孔隙大小、形態(tài)、分布、定向性四方面特征的孔隙結(jié)構(gòu)影響因子與荷載之間具有良好的相關(guān)性。研究表明，軟土的宏觀工程性質(zhì)與微觀參數(shù)之間存在緊密聯(lián)系，固結(jié)土的壓縮性、滲透性均可由天然部分和固結(jié)變化部分構(gòu)成。其中，天然部分與初始結(jié)構(gòu)性特征(主要是孔隙特征)相關(guān)，一般同時(shí)與多個(gè)結(jié)構(gòu)參數(shù)相關(guān)；而固結(jié)變化部分與固結(jié)引起的結(jié)構(gòu)性特征(主要是孔隙特征)的變化相關(guān)，最終可表達(dá)為與固結(jié)壓力的關(guān)系。 (6)建立基于微細(xì)觀試驗(yàn)(經(jīng)驗(yàn)公式)的修正固結(jié)模型，通過(guò)實(shí)測(cè)結(jié)果證實(shí)了模型的合理性和有效性。修正固結(jié)模型基于土體微細(xì)觀結(jié)構(gòu)特別是微細(xì)孔隙結(jié)構(gòu)特征的物理機(jī)制，反映土體固結(jié)與荷載的非線性關(guān)系。
[Abstract]:The Pearl River Delta region is widely distributed in the soft soil layers formed by the Holocene sea of a few meters to dozens of meters, mainly silt, silt silt and clay, with high water content, large pore ratio, high compressibility, low strength, poor permeability, and significant structural and rheological properties, which lead to ground subsidence and instability. In order to improve the quality of the soft soil foundation and reduce the construction accidents, it is necessary to study the engineering characteristics of soft soil and improve the design and construction level of soft soil foundation. However, for a long time, people mainly study the engineering characteristics of soft soil from the macro level, so it is difficult to grasp the essential factors determining the soft soil properties so as to make the engineering characteristics of the soft soil. Therefore, it is a kind of "root search and traceability" method to study the engineering properties of soft soil from the analysis of soil microstructure, which can deeply understand the engineering characteristics of soft soil in essence.
In this paper, the natural soil (or remolded soil) in the Pearl River Delta is taken as the research object. The characteristics and engineering properties of the soft soil in the Pearl River Delta are studied from a statistical point of view. The microstructure factors (such as particle shape, distribution, arrangement and connection mode, micro particle polymerization) in the process of seepage consolidation in soft soil are studied with mineral composition test, ESEM test and mercury injection test. The change characteristics and fractal characteristics of body shape, pore number, pore shape, scale and distribution, connectedness and zigzag, combine the micro parameters of soft soil with the macroscopic engineering properties, and explain the micro mechanism affecting the soft soil properties. Finally, a modified consolidation model based on the microscopic test is proposed, which confirms the combination of the model through the measured results. Rationality and effectiveness.
The main findings and conclusions obtained in this paper are as follows:
(1) through the analysis of the geological and hydrological environment, mineral composition, particle characteristics and microscopic characteristics of the soft soil in the Pearl River Delta, it is found that the special macroscopic engineering characteristics are mainly determined by the microcosmic factors. The distribution of the physical and mechanical indexes of the soft soil in the Pearl River delta is studied by using the "skewness and kurtosis test". The soft soil engineering in this area can be used for reference.
(2) compared with the global threshold segmentation method, the porosity ratio obtained by the local threshold segmentation method is closer to the actual results. The method of matching the threshold selection of the two value quantitative analysis of the microscopic structure with the micropore gap characteristics and the three-phase diagram calculation can solve the problem of the transition dispersion and the human interference in the quantitative analysis of the present microscopic test results. The reliability and accuracy of the existing microtest.
(3) during the consolidation process, the type of the soft soil microstructure gradually changes, and the honeycomb structure (sponge structure) is gradually transformed into the skeleton structure, the turbulence structure and the dense structure, and the connection mode is transformed from side to side, side to surface connection to surface to surface, the area of the structure unit increases obviously and the pore decreases, and the remolded soil particles are knead due to lack of structure. Together, the polymer is mainly clot structure and relatively dense. With the increase of load, the particle element is mainly composed of surface to surface connection.
(4) the quantitative parameters of structural unit and pore microstructure have different regularities at different stages of consolidation. In the early consolidation period, when the effective stress is small, the microstructure is in the stable adjustment stage because the mud soil has a certain structural strength, the number of pores is less, the pore is larger, the main pore is the main pore, and the structure unit is the main body. When the effective stress increases to the structural yield stress, when the effective stress increases to the structural yield stress, the structure gradually destroys, the aggregate is broken, the microstructure is in the stage of drastic adjustment, the equivalent diameter of the structural unit increases obviously, the circle degree and the mean shape coefficient decrease significantly, and have a trend of changing and perpendicular to the vertical. In the direction of pressure, there is a clear directional arrangement in the direction of pressure. At this time, the number of pores increases obviously, the equivalent pore size becomes smaller and the shape becomes more complex. The pore distribution is from medium, small pore to small, micropore and even ultramicro pore, but the directional change is not obvious. When the effective stress continues to increase, the new microstructure is properly adjusted, structure single The variation of quantitative parameters of the element and pore tends to be gentle.
(5) the structural elements and pores of the natural soft soil (or remolded soil) in the Pearl River Delta have obvious fractal structure characteristics. The influence factors of pore structure, which reflect the four aspects of pore size, morphology, distribution and orientation, have good correlation with the load. The research shows that the macroscopic engineering properties of soft soil and the micro parameters are between the parameters. The compressibility of the consolidated soil, the compressibility of the consolidated soil, and the permeability can be made up of the natural and consolidation parts. The natural part is related to the initial structural characteristics (mainly pore characteristics), generally related to the structural parameters, and the structural characteristics (mainly pore characteristics) caused by the consolidation change part and the solid junction. Chemical correlation can eventually be expressed as the relationship between consolidation pressure.
(6) to establish a modified consolidation model based on the micro observation test (empirical formula), and verify the rationality and effectiveness of the model through the measured results. The modified consolidation model is based on the physical mechanism of the micropore structure, especially the characteristics of the micro pore structure, reflecting the nonlinear relationship between the consolidation and load of the soil.
【學(xué)位授予單位】：華南理工大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2013
【分類號(hào)】：TU447

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 孔令榮;黃宏偉;張冬梅;P.-Y.Hicher;;不同固結(jié)壓力下飽和軟粘土孔隙分布試驗(yàn)研究[J];地下空間與工程學(xué)報(bào);2007年06期

2 張延軍,張延詰;海積軟土彈粘塑性Biot固結(jié)的數(shù)值分析[J];吉林大學(xué)學(xué)報(bào)(地球科學(xué)版);2003年01期

3 袁俊平,殷宗澤,包承綱;膨脹土裂隙的量化手段與度量指標(biāo)研究[J];長(zhǎng)江科學(xué)院院報(bào);2003年06期

4 劉云華,黃同興,劉成東;X射線衍射增量法在三水鋁石定量分析中的應(yīng)用——以桂西堆積型鋁土礦中的紅土為例[J];地質(zhì)科技情報(bào);2004年02期

5 施斌;粘性土微觀結(jié)構(gòu)研究回顧與展望[J];工程地質(zhì)學(xué)報(bào);1996年01期

6 趙維炳;錢家歡;;設(shè)置砂井的軟粘土地基動(dòng)力固結(jié)[J];港口工程;1985年03期

7 馬馴;;固結(jié)系數(shù)與固結(jié)壓力關(guān)系的統(tǒng)計(jì)分析及研究[J];港口工程;1993年01期

8 趙維炳;施建勇;;軟土流變理論及其在排水預(yù)壓加固分析中的應(yīng)用[J];水利水電科技進(jìn)展;1996年03期

9 沈珠江;;用有限單元法計(jì)算軟土地基的固結(jié)變形[J];水利水運(yùn)科技情報(bào);1977年01期

10 張誠(chéng)厚;;兩種結(jié)構(gòu)性粘土的土工特性[J];水利水運(yùn)科學(xué)研究;1983年04期

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