【摘要】：吹填土是一種特殊的人工土，其固結(jié)時(shí)間較長，具有十分明顯的流變特性。吹填土作為地基會(huì)出現(xiàn)后期沉降過大，承載力不足等問題，嚴(yán)重的會(huì)導(dǎo)致地基不均勻沉降，地面開裂，建（構(gòu)）筑物傾斜甚至倒塌等。學(xué)術(shù)界及工程界一直廣泛關(guān)注吹填軟土的長期變形問題，其中軟土的固結(jié)特性和蠕變特性是導(dǎo)致其變形具有時(shí)效性的根本原因。故研究吹填軟土的長期變形機(jī)理，探討其固結(jié)蠕變特性，并進(jìn)一步完善沉降計(jì)算模型，對(duì)建造在吹填土地基上的工程具有重要意義。 目前在室內(nèi)關(guān)于土體固結(jié)蠕變變形的研究大多假定其不產(chǎn)生側(cè)向變形，但是對(duì)于吹填土來說，滿足這一假設(shè)的區(qū)域是有限的，更多區(qū)域如大面積堆載的非中心地帶，路堤等工程的非中心區(qū)域等其側(cè)向變形常常不等于零。即使是中心區(qū)域，也不能忽視瞬時(shí)變形及其對(duì)后期變形的影響。本文針對(duì)汕頭東部新溪地區(qū)吹填軟土，基于室內(nèi)側(cè)限（剛性，柔性）試驗(yàn)，理論分析和相應(yīng)的數(shù)值計(jì)算，研究了軟土固結(jié)蠕變變形機(jī)理，分析了側(cè)向變形條件對(duì)軟土一維固結(jié)蠕變特性的影響。研究的主要內(nèi)容以及得到的結(jié)論如下： 1.吹填軟土的基本特性研究，，研究表明土層含有大量砂石貝殼等雜質(zhì)，物理性質(zhì)指標(biāo)均為高含水率，高孔隙比，低滲透性，和低抗剪強(qiáng)度。土層目前仍處于欠固結(jié)土階段，壓縮性較大。 2.剛性側(cè)限壓縮試驗(yàn)（側(cè)向變形等于0）結(jié)果表明，加荷比大于或等于1時(shí)土樣的主次固結(jié)分界最明顯，最適合用Casagrande方法確定主固結(jié)完成時(shí)間。次固結(jié)系數(shù)Ca均呈現(xiàn)先增大，在先期固結(jié)壓力附近達(dá)到峰值后逐漸減小最后趨于穩(wěn)定。土體物理參數(shù)如而含水率、孔隙比、及試驗(yàn)方法如加荷比等因素都會(huì)對(duì)次固結(jié)系數(shù)產(chǎn)生影響。另外，軟土的次固結(jié)呈非線性特征，應(yīng)力應(yīng)變等時(shí)曲線比較符合對(duì)數(shù)函數(shù)關(guān)系。 3．柔性側(cè)限壓縮（豎向應(yīng)力與水平應(yīng)力之比等于常數(shù)）試驗(yàn)結(jié)果表明，吹填土的固結(jié)性狀與上述剛性側(cè)限相似，表明其固結(jié)機(jī)理時(shí)相同的。但試樣產(chǎn)生了較大的瞬時(shí)變形，主固結(jié)完成的時(shí)間減少，次固結(jié)系數(shù)也相對(duì)減小。 4.基于三元件模型，建立了考慮瞬時(shí)變形的飽和土體的一維粘彈性固結(jié)方程，并推導(dǎo)出其相應(yīng)的解析解。針對(duì)具體算例對(duì)大面積堆載的一維粘彈性固結(jié)性狀進(jìn)行了分析。
[Abstract]:The backfill is a special artificial soil with long consolidation time and obvious rheological properties. As a foundation, the filling soil will have some problems such as excessive settlement, insufficient bearing capacity and so on, which will lead to uneven settlement of the foundation, cracking of the ground, tilt of the building (construction) and even collapse of the building, etc. The academic and engineering circles have been paying close attention to the long-term deformation of filled soft soil, among which the consolidation and creep characteristics of soft soil are the fundamental reasons leading to the timeliness of deformation. Therefore, it is of great significance to study the long-term deformation mechanism of drilled soft soil, to discuss its consolidation and creep characteristics, and to further improve the settlement calculation model. At present, most of the researches on consolidation creep deformation of soil are based on the assumption that it does not produce lateral deformation, but the area satisfying this assumption is limited, and more areas, such as the non-central zone with large area of heaped load, are satisfied with this assumption. The lateral deformation of the non-central area of embankment is often not equal to zero. Even in the central region, the instantaneous deformation and its influence on the later deformation can not be ignored. In this paper, the mechanism of consolidation creep deformation of soft soil in Xinxi area of eastern Shantou is studied on the basis of indoor lateral limit (rigidity, flexibility) test, theoretical analysis and corresponding numerical calculation. The effects of lateral deformation conditions on one dimensional consolidation creep properties of soft soil are analyzed. The main contents and conclusions are as follows: 1. The basic characteristics of soft soil are studied. The results show that the soil layer contains a lot of impurities such as sand and stone shells, and the physical properties are high water content, high porosity, low permeability and low shear strength. The soil layer is still in the stage of underconsolidation, and its compressibility is great. 2. The results of the rigid lateral compression test (lateral deformation = 0) show that the primary and secondary consolidation boundaries of soil samples with loading ratio greater than or equal to 1 are the most obvious, and the Casagrande method is most suitable to determine the completion time of the main consolidation. The secondary consolidation coefficient (Ca) increased at first, and then decreased gradually and finally stabilized after reaching the peak near the pre-consolidation pressure. Physical parameters such as moisture content porosity ratio and test method such as loading ratio will affect the secondary consolidation coefficient. In addition, the secondary consolidation of soft soil is nonlinear, and the stress-strain isochronous curve accords with the logarithmic function. 3. The experimental results of flexible lateral compression (the ratio of vertical stress to horizontal stress is constant) show that the consolidation behavior of the filled soil is similar to that of the rigid lateral limit mentioned above, which indicates that the consolidation mechanism is the same. However, the sample has a large instantaneous deformation, the time of completion of the main consolidation is reduced, and the secondary consolidation coefficient is also relatively reduced. 4. Based on the three-element model, the one-dimensional viscoelastic consolidation equation of saturated soil considering instantaneous deformation is established, and the corresponding analytical solution is derived. The one-dimensional viscoelastic consolidation behavior of large area surcharge is analyzed for a concrete example.
【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：TU449;TU43

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