本文選題：軟土地基 + 真空預壓��； 參考：《華南理工大學》2014年碩士論文

【摘要】：隨著我國經(jīng)濟的快速發(fā)展，工程建設活動也越來越多，特別是在沿海以及內(nèi)陸江河湖泊地區(qū)進行工程建設時經(jīng)常會遇到軟土工程地質(zhì)，給工程建設帶來麻煩，因此需要對軟土地基進行處理。 本文在前人調(diào)查研究工作以及工程實例的基礎(chǔ)上，對真空預壓法處理軟土地基的地基變形展開研究工作，探索真空預壓地基計算沉降的合理方法，并采用有限元進行模擬，主要內(nèi)容和研究成果如下： （1）歸納總結(jié)了我國軟土的成因類型、分布特點以及各種處理技術(shù)的優(yōu)缺點。我國軟土分布較廣，成因類型較多，從北到南，自東至西都有軟土的分布，我國軟土分布總體上呈現(xiàn)“北強南弱、依次變化”的特點。目前，現(xiàn)有的軟土地基的處理方法，從手段上可分為兩大類：一類是土質(zhì)改良法；另一類是復合地基法。土質(zhì)改良法是從改善原地基土體物質(zhì)性質(zhì)著手，提高土體強度、壓縮特性等等，主要手段有排水固結(jié)、換土墊層等。復合地基法是不改變原土體的性質(zhì)，在地基中構(gòu)筑復合地基，使土體和樁體共同承擔荷載。 （2）在前述內(nèi)容的基礎(chǔ)上，詳細介紹真空預壓法的設計、施工及監(jiān)測方案。以珠海某口岸工程案例為基礎(chǔ)，根據(jù)場地軟土的性質(zhì)，進行處理方案的比選，最終選擇了真空預壓法處理軟土地基，，并采用監(jiān)測手段獲得真空預壓過程中的地基的變形數(shù)據(jù)，以便于通過數(shù)據(jù)對真空預壓地基的變形規(guī)律進行研究。 （3）通過對觀測得到的大量數(shù)據(jù)進行分析，發(fā)現(xiàn)地基有較大的沉降量，前期沉降較快，后期較慢，大部分沉降發(fā)生在前三個月。其中淤泥層的壓縮量占總沉降量的70%~89.3%，其抗剪強度有較大幅度提高，在抽真空的過程中地基中不同深度的孔隙水壓力有不同程度的下降。地基加固區(qū)周圍出現(xiàn)了斷斷續(xù)續(xù)的環(huán)形裂縫，說明地基在真空預壓的過程中會產(chǎn)生向加固區(qū)內(nèi)的收縮變形。真空預壓法對塑料排水板深度范圍內(nèi)土體的性質(zhì)有較大的改善，特別是對淤泥層的改善較大。 （4）在實測數(shù)據(jù)的基礎(chǔ)上，采用等效堆載法、對數(shù)曲線法、負壓滲流場法、有效應力法、真空度差值法及有限元法進行了計算。將計算結(jié)果與實測對比發(fā)現(xiàn)：規(guī)范推薦的沉降計算方法仍是較實用的方法，但計算結(jié)果比實測要小。采用平面應變有限元法對真空預壓地基進行變形分析，有限元計算結(jié)果與實測較接近，有一定的可靠性，可作為一種計算方法之一。同時對影響真空預壓效果的影響因素進行了分析，分析結(jié)果表明：膜下真空度大小、塑料排水板深度、間距對工程有較大影響。采用雙曲線擬合沉降觀測數(shù)據(jù)，得到地基的最終沉降量，以此計算地基的固結(jié)度在80%以上，滿足設計的要求。因此塑料排水板要打設到設計處理軟土層的層底，間距不宜過大，但由于井阻的作用，真空度的影響深度有限，塑排深度過大會造成不必要的浪費。
[Abstract]:With the rapid development of China's economy, more and more engineering construction activities, especially in the coastal and inland river and lake areas, often encounter soft soil engineering geology, which brings trouble to the construction of the project, so it is necessary to deal with the soft soil foundation.
On the basis of previous research work and engineering examples, this paper studies the deformation of soft soil foundation treated by vacuum preloading method, and explores a reasonable method for calculating settlement of vacuum preloading foundation, and uses finite element method to simulate, the main contents and research results are as follows:
(1) the genetic types and distribution characteristics of soft soil in China and the advantages and disadvantages of various processing techniques are summed up. The distribution of soft soil in China is wide and the genetic types are more, from north to South and from the east to the west, the distribution of soft soil from the east to the west, the distribution of soft soil in China is characterized by the characteristics of "the weak north and the South weak, the second change" in China. At present, the existing soft soil foundation treatment Methods can be divided into two categories: one is the soil improvement method, the other is the composite ground method. The soil quality improvement method is to improve the physical properties of the original soil, improve the strength of the soil, the compression characteristics and so on. The main means are the consolidation of the soil and the soil cushion, etc. the composite foundation method is not changed the nature of the soil and is constructed in the foundation. The composite foundation is constructed to make the soil and pile share the load.
(2) on the basis of the foregoing content, the design, construction and monitoring scheme of vacuum preloading method are introduced in detail. Based on the case of a port engineering in Zhuhai, according to the nature of the soft soil of the site, the comparison and selection of the treatment scheme are carried out, and the vacuum preloading method is selected to deal with the soft soil foundation, and the change of the foundation in the vacuum preloading process is obtained by the monitoring method. Shape data are used to study the deformation rules of vacuum preloading foundation through data.
(3) through the analysis of the large amount of data obtained from the observation, it is found that the foundation has large settlement, the early settlement is faster and the latter is slower, most of the settlement occurs in the first three months. The compress of the silt layer accounts for 70%~89.3% of the total settlement, and its shear strength is greatly improved, and the holes of different depths in the foundation of vacuum extraction are in the process of vacuuming. The gap water pressure decreases in varying degrees. The intermittent ring cracks appear around the reinforcement area, which indicates that the foundation will produce contraction deformation in the reinforced zone during the vacuum preloading process. The vacuum preloading method has a great improvement in the soil properties in the depth range of the plastic drainage plate, especially the improvement of the silt layer.
(4) on the basis of the measured data, the equivalent loading method, logarithmic curve method, negative pressure seepage field method, effective stress method, vacuum difference method and finite element method are used to calculate. The calculation results are compared with the measured results, and it is found that the standard method of settlement calculation is still a more practical method, but the calculation results are smaller than the actual measurement. The finite element method is used to analyze the deformation of vacuum preloaded foundation. The result of finite element calculation is close to the measurement, and it has certain reliability. It can be used as one of the calculation methods. Meanwhile, the influence factors of vacuum preloading effect are analyzed. The results show that the vacuum degree under film, the depth and distance of plastic drain board are more than that of the engineering. A hyperbolic curve fitting settlement observation data is used to get the final settlement of the foundation, so as to calculate the consolidation degree of the foundation above 80% and meet the requirements of the design. Therefore, the plastic drain board should be set to the bottom of the soft soil layer designed to deal with the ground, but the spacing of the ground is not too large, but the depth of the vacuum degree is limited and the depth of the vacuum is limited and the depth of the plastic drainage is limited due to the effect of the well resistance. The meeting caused unnecessary waste.
【學位授予單位】：華南理工大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：TU472.33

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