本文選題：珠海軟土 + 固結性質��； 參考：《華南理工大學》2013年博士論文

【摘要】：軟土是工程建設中常見的天然材料，其物理力學性質非常復雜，具有高含水量、大孔隙比、高壓縮性、低強度、且滲透性差、結構性顯著等特點，廣泛分布于沿海、河流中下游及湖泊的三角洲地區(qū)。在軟土中具有代表性的有淤泥和淤泥質土，主要是由極細的粘土顆粒、有機物、氧化物等固相物質和水組成。珠海軟土表現(xiàn)出典型的軟土性質，其地基土呈現(xiàn)出低承載力、大沉降量、沉降穩(wěn)定所需時間長等，這將會直接影響工程造價、進度以及安全性。大量的研究與實踐證明，軟土特定的歷史環(huán)境會影響其工程性質的形成，而且軟土的工程性質不僅與其礦物成分，顆粒大小、深度、外荷載狀態(tài)及排水條件有關外，還與其微觀顆粒及孔隙特征、顆粒的連結方式及組成排列、顆粒之間的膠結方式等微觀結構形態(tài)特征有關。目前階段而言，大量學者都主要從宏觀層面對軟土的工程特性進行研究，而這從根本上解釋不了軟土表現(xiàn)不良工程特性的本質規(guī)律。本文通過宏觀與微觀試驗，系統(tǒng)的介紹了研究珠海軟土工程性質的手段方法，分別從宏觀及微觀的角度分析了珠海軟土固結等工程特性及其固結過程變化的微觀機制。 本文主要開展的研究工作以及理論成果如下： （1）通過珠海原狀軟土不同深度的室內(nèi)基本物理力學性質試驗，得出珠海軟土顆粒土以細粒土為主，粘土礦物含量大。珠海軟土中顆粒以粘粒和粉粒等細粒土為主，且礦物成分中，粘土礦物以高嶺石為主，其次為伊利石，蒙脫石含量較少。比表面積較大，液塑限與其比表面積呈正相關關系；粘土礦物比表面積值及吸附性能強于非粘土礦物，結合水量高；比表面積與滲透系數(shù)呈現(xiàn)一定負相關性，表現(xiàn)出比表面積越大，滲透性越低的特征。 （2）通過珠海軟土的常規(guī)固結試驗及回彈試驗的成果數(shù)據(jù)，可以得出珠海軟深厚土層屬于欠固結土。軟土的固結特征與先期固結壓力相關，當固結壓力超過先期固結壓力時，土體的固結速率呈現(xiàn)增長趨勢。水平向固結系數(shù)在固結的初始階段與豎向固結有較大區(qū)別，隨著土樣深度的增加，最終的固結系數(shù)穩(wěn)定值呈現(xiàn)減小趨勢。珠海相軟土的結構性較強，當固結壓力超過上覆土體荷載時，土體處于回彈初始階段，回彈曲線特征較為平緩；當固結壓力卸載到小于上覆土體荷載時，土樣處于快速回彈階段，回彈曲線特征較陡，孔隙比增長迅速。 （3）運用環(huán)境掃描電子顯微鏡技術對珠海原狀不同深度及不同切面方向的軟土以及固結后的土樣進行觀測分析，得出珠海天然軟土的微觀結構主要有蜂窩狀結構、海綿狀結構及凝塊狀結構三種類型。土顆粒呈曲片絮凝狀疊聚體，微孔隙分布較多，深部比淺部土樣的微觀顆粒小，密實度大，且絮凝結構明顯，微孔隙分布多，定向概率熵較大。固結過程中大量的大孔隙被壓縮成小孔隙，土體變得更加密實，顆粒也無明顯定向性，顆粒單元體呈現(xiàn)出由原來邊-面、邊-邊組合轉化為面-面組合為主，無明顯曲片狀結構，顆粒凝聚成團，且相互之間接觸緊密。在荷載增加的過程中，孔隙中的水分減少，結合水膜變薄，顆粒凝聚成團狀形式。大孔隙面積和數(shù)量減少，小孔隙數(shù)量增多，等效孔徑相應減小，孔隙由粒間孔隙向團聚單元體內(nèi)部孔隙轉變。固結過程中垂直方向比水平方向的微觀性質變化明顯，長軸容易被切割破壞成小顆粒，土樣的微觀結構單元體特性主要在受壓方向發(fā)生相應的變化。 （4）通過壓汞試驗，研究珠海軟土的滲透作用對其微觀孔隙尺度分布的變化影響，及固結過程當中土樣的微觀孔隙變化規(guī)律進行分析。珠海原狀軟土的微觀孔隙都主要分布400nm-2500nm及30nm-400nm。滲透后土樣的微觀孔隙有所增大，滲透力的作用帶走了部分顆粒，且孔隙集中分布孔徑大于原狀樣的峰值孔徑值，同時軟土的孔隙面積有所減小，，且對微觀孔隙尺度的分布有均化的作用。在固結過程中土體較大的孔隙逐漸轉變?yōu)檩^小孔隙。軟土試樣在固結壓力100kPap200kPa時，孔隙比和平均孔徑都減小迅速；而當固結壓力p200kPa，孔隙比及平均孔徑仍在減小，但速度減緩。 （5）針對單向固結的普遍方程和太沙基單向固結理論，通過微觀參量比表面積S、等效孔徑D、顆粒的定向概率熵H m、顆粒的分形維數(shù)D p與土的固結系數(shù)的相應關系，給出了考慮微觀因素修正的固結系數(shù)方程，并通過微觀參量的范圍取值，給出了相應微觀參量的影響因子α、β、ζ、η數(shù)值。并通過實際的工程，真空聯(lián)合堆載預壓對珠海金灣軟土的現(xiàn)場取樣圖片、十字板剪切數(shù)據(jù)、及實際固結沉降量等結果的分析，驗證其分析值與室內(nèi)的宏觀與微觀試驗測試分析的數(shù)據(jù)及理論的正確性及可靠性。
[Abstract]:Soft soil is a common natural material in engineering construction, its physical and mechanical properties are very complex, with high water content, large pore ratio, high pressure shrinkage, low strength, poor permeability and significant structural characteristics, widely distributed in the coastal area, the middle and lower reaches of the river and the delta area of the lake. In the case of fine clay particles, organic matter, oxide and other solid substances and water, the soft soil in Zhuhai shows typical soft soil properties, and its foundation soil presents a low bearing capacity, large settlement, and a long settlement, which will directly affect the cost, progress and safety of the project. A large number of research and practice have proved that soft soil is specific. The historical environment will affect the formation of its engineering properties, and the engineering properties of the soft soil are not only related to its mineral composition, particle size, depth, external load state and drainage conditions, but also with the microscopic particle and pore characteristics, the connection mode and composition of particles, the cementation between particles and other microstructure features. In the previous stage, a large number of scholars mainly study the engineering characteristics of soft soil from the macro level, which can not fundamentally explain the essential law of the soft soil performance. This paper systematically introduces the methods and methods to study the engineering properties of Zhuhai soft soil through macroscopic and microscopic tests, respectively, from the macro and micro angles. The microstructural mechanism of consolidation and other engineering characteristics of soft soil in Zhuhai is analyzed.
The main research work and theoretical achievements in this paper are as follows:
(1) through the laboratory basic physical and mechanical properties test of different depth of Zhuhai soft soil, it is concluded that the soft clay in Zhuhai is mainly fine grained soil with large clay mineral content. The particles in Zhuhai soft soil are mainly fine clay particles such as clay particles and powder particles, and in the mineral composition, clay minerals are mainly high ridge, followed by illite, and the content of montmorillonite is less than that of illite. The surface area is larger, and the liquid plastic limit is positively related to the specific surface area; the clay mineral is stronger than the surface area and the adsorption property is stronger than the non clay mineral. The specific surface area and permeability coefficient show a certain negative correlation, which shows that the larger the surface area is, the lower the permeability is.
(2) through the data of conventional consolidation test and rebound test of Zhuhai soft soil, it can be concluded that soft deep soil in Zhuhai belongs to underconsolidated soil. The consolidation characteristics of soft soil are related to the pre consolidation pressure. When consolidation pressure exceeds the pre consolidation pressure, the consolidation rate of soil is increasing. The horizontal consolidation coefficient is in the initial order of consolidation. There is a great difference between the vertical consolidation and the vertical consolidation. With the increase of the soil sample depth, the final stability of the consolidation coefficient decreases. The structure of the Zhuhai phase soft soil is stronger. When the consolidation pressure exceeds the overlying soil load, the soil is in the initial stage of rebound, and the characteristic of the rebound curve is relatively gentle; when the consolidation pressure is less than the overburden soil load, the consolidation pressure is less than the overburden soil load. At the time of loading, the soil sample is in a rapid rebound stage, and the rebound curve is steeper and the void ratio increases rapidly.
(3) by observing and analyzing the soft soil with different depth and different tangent direction in Zhuhai with environmental scanning electron microscopy, it is found that the microstructure of Zhuhai natural soft soil mainly consists of honeycomb structure, spongy structure and three types of clot like structures. In the deep part, the depth is smaller than the shallow soil, the density is large, the flocculation structure is obvious, the distribution of the micropore is more and the directional probability entropy is larger. In the consolidation process, a large number of large pores are compressed into small pores, the soil becomes more dense and the particles have no obvious orientability, and the granular element body is transformed from the original side to side, side side combination transformation. In the process of the increase of load, the water in the pore is reduced, the water film becomes thinner and the particles are condensed into a mass form. The size and quantity of the macropores are reduced, the number of small pores increases, the equivalent pore size decreases, and the pores are from intergranular pores. The internal pore changes in the agglomeration unit. In the process of consolidation, the microscopic properties of the vertical direction change obviously than the horizontal direction. The long axis is easily cut into small particles, and the characteristics of the microstructural elements of the soil sample are mainly changed in the compression direction.
(4) through the mercury pressure test, the influence of the permeability of Zhuhai soft soil on the change of the micropore size distribution and the micropore change law of the soil samples during the consolidation process are analyzed. The micro pores of the original soft clay in Zhuhai are mainly distributed in the micro pores of 400nm-2500nm and 30nm-400nm. infiltration, and the permeability is increased. Some particles are taken away, and the pore size distribution is larger than the peak value of the original sample, while the pore size of the soft soil decreases, and the pore size distribution is homogenized. During the consolidation process, the larger pores of the soil gradually change to smaller pores. The pores of the soft soil specimen are at the consolidation pressure of 100kPap200kPa. The ratio and average pore diameter decrease rapidly, while the pore ratio and average pore diameter decrease while the consolidation pressure is p200kPa, but the speed decreases.
(5) in view of the universal equation of unidirectional consolidation and the unidirectional consolidation theory of Tai Sha foundation, the relation between the microscopic parameter specific surface area S, the equivalent aperture D, the directional probability entropy H m of the particle, the fractal dimension D P of the particle and the consolidation coefficient of the soil is given, and the equation of the fixing coefficient considering the correction of the microcosmic factors is given, and the value of the microscopic parameters is obtained. The results of field sampling pictures, cross plate shear data and actual consolidation settlement of Zhuhai Golden Bay soft soil were analyzed by the actual engineering, vacuum combined loading preloading, and the data and theory of the analysis value of the analysis value and the macro and micro test test in the room were verified. Correctness and reliability.
【學位授予單位】：華南理工大學
【學位級別】：博士
【學位授予年份】：2013
【分類號】：TU447

【參考文獻】

相關期刊論文 前10條

1 馮秀麗,林霖,莊振業(yè),潘樹春;現(xiàn)代黃河水下三角洲全新世以來土層巖土工程參數(shù)與沉積環(huán)境之間的關系[J];海岸工程;1999年04期

2 劉忠玉;楊榮根;;考慮起始水力梯度時雙層地基的一維固結[J];合肥工業(yè)大學學報(自然科學版);2006年05期

3 施建勇,楊立昂,趙維炳,劉永新;考慮土體非線性特性的一維固結理論研究[J];河海大學學報(自然科學版);2001年01期

4 劉小平;趙明華;陳安;;從飽和度再認識非飽和表層土吸力[J];湖南大學學報(自然科學版);2007年07期

5 陳平山;莫海鴻;;真空預壓加固地基等效固結度的簡化計算[J];華南理工大學學報(自然科學版);2008年01期

6 朱麗東;葉瑋;周尚哲;李風全;楊立輝;沈葉琴;;金衢盆地第四紀紅土沉積粒度組成特征[J];海洋地質與第四紀地質;2006年04期

7 陳勇;單紅仙;賈永剛;;黃河沉積粉土滲透系數(shù)變化研究[J];海洋湖沼通報;2005年04期

8 高國瑞;中國海相沉積土微結構研究和工程性質[J];中國科學(B輯 化學 生物學 農(nóng)學 醫(yī)學 地學);1984年09期

9 張季超;許勇;李伍平;朱立宏;易和;王良福;;基于微結構參數(shù)的飽和軟土工程性質的研究[J];建筑結構;2007年11期

10 孫宏偉;;北京新近沉積土基礎工程特性研究[J];建筑結構;2009年12期

本文編號：2074256