【摘要】：隨著城市化進程的不斷加快,全國各地高樓大廈相繼拔地而起,城市軌道交通建設(shè)也迎來發(fā)展高峰,各地水利堤防工程也相繼建設(shè)完善,這些工程大多都涉及到復(fù)雜多變的粘性土地層。由于粘性土地層長期經(jīng)受地下水的滲透作用,粘性土的物理力學(xué)性能、結(jié)構(gòu)等都會發(fā)生緩慢劣化,大量巖土工程事故也都證明了土體滲透破壞產(chǎn)生的危害巨大。因此探究粘性土滲透破壞和長期滲透條件下?lián)p傷劣化實質(zhì)具有重要意義。本文主要開展了以下幾個方面研究:(1)針對粘性土進行了界限含水率、比重、顆粒分析、擊實、固結(jié)、直剪等一系列基本物理力學(xué)性質(zhì)試驗,重點闡述了粘性土的壓縮性能和抗剪強度。試驗得出粘性土變形量隨著含水率和豎向荷載的增大而增大;土樣粘聚力隨著干密度的增大而增大,隨著均值粒徑的增大而減小;內(nèi)摩擦角隨著干密度的增大而減小,隨著均值粒徑的增大而增大,但相關(guān)性和幅度均較小;粘聚力隨不均勻系數(shù)的增大而較小,內(nèi)摩擦角隨不均勻系數(shù)的增大而增大;粘聚力隨曲率系數(shù)的增大而減小,內(nèi)摩擦角隨曲率系數(shù)的增大基本不變;(2)利用自制的滲透破壞儀研究了各單一粒徑和混合粒徑土樣在各干密度下的滲透破壞臨界坡降大小。對于單一粒徑級土樣,干密度對土體滲透破壞臨界坡降影響最為顯著,均值粒徑次之,臨界坡降隨干密度三次方的增加而線性增加,隨均值粒徑的增加而線性減小;對于混合粒徑的粘性土,不均勻系數(shù)對土體滲透破壞臨界坡降影響較為顯著,曲率系數(shù)次之,臨界坡降隨不均勻系數(shù)、曲率系數(shù)的增加而線性減小;(3)采用變水頭滲透儀對不同干密度土樣在不同PH值滲透液下進行長期滲透試驗。試驗得到各干密度土樣在各PH值的滲透液長期滲透作用下,滲透系數(shù)均隨著滲透時間得增大而減小;以PH=7的蒸餾水為液滲透的土樣初始滲透系數(shù)總是大于以PH=3的鹽酸為滲透液土樣的初始滲透系數(shù);經(jīng)過長期滲透后,較小干密度土樣在酸性滲透液滲透后其滲透系數(shù)大于以蒸餾水為滲透液滲透后的土樣,較大干密度的土樣則相反;高壓實度土體在各PH值滲透液滲透后,其土體浸出液所含鈉、鉀、鈣、鎂離子濃度均小于低壓實度土體;且土體浸出液中鈣離子含量最高,鈉、鎂離子濃度次之,鉀離子濃度最低。
[Abstract]:With the continuous acceleration of the urbanization process, the high-rise buildings in various parts of the country have emerged one after another, the construction of urban rail transit has also ushered in the peak of development, and the water conservancy and levee projects in various places have been built and perfected one after another. Most of these projects involve complex and changeable clay layers. Because the viscous soil layer is subjected to the infiltration of groundwater for a long time, the physical and mechanical properties, structure and so on of clay soil will slowly deteriorate. A large number of geotechnical engineering accidents have also proved that the damage caused by soil seepage failure is great. Therefore, it is of great significance to explore the essence of permeability failure and damage deterioration of cohesive soil under long-term permeation conditions. In this paper, the following aspects have been studied: (1) A series of basic physical and mechanical properties such as limit moisture content, specific gravity, particle analysis, compaction, consolidation, direct shear and so on have been carried out for cohesive soils. The compressive properties and shear strength of clay are described in detail. The results show that the deformation of cohesive soil increases with the increase of moisture content and vertical load, the cohesive force increases with the increase of dry density and decreases with the increase of mean particle size, and the angle of internal friction decreases with the increase of dry density. With the increase of the mean particle size, the correlation and amplitude are smaller, the cohesion force is smaller with the increase of the non-uniform coefficient, the internal friction angle increases with the increase of the non-uniform coefficient, and the cohesion force decreases with the increase of the curvature coefficient. The angle of internal friction is almost unchanged with the increase of curvature coefficient. (2) the critical slope of permeation failure of soil samples with single particle size and mixed particle size at various dry densities is studied by using a self-made permeation failure instrument. For soil samples with single particle size, dry density has the most significant effect on the critical slope of soil permeability failure, the mean particle size is the second, the critical gradient increases linearly with the increase of dry density to the third power, and decreases linearly with the increase of mean particle size. For clayey soil with mixed particle size, the influence of inhomogeneous coefficient on the critical slope of soil seepage failure is significant, the curvature coefficient is the second, and the critical slope gradient is with the non-uniform coefficient. (3) soil samples with different dry densities were subjected to long-term permeation experiments with different PH values. (3) soil samples with different dry densities were subjected to long-term permeation tests with varying water head osmometers. The results showed that the permeability coefficient of soil samples with different PH values decreased with the increase of permeation time. The initial permeability coefficient of soil sample with distilled water of PH=7 is always higher than that with hydrochloric acid of PH=3. The permeability coefficient of soil samples with small dry density is larger than that of soil samples with distilled water as osmotic solution, but the soil sample with higher dry density has the opposite effect after permeation of acid osmotic solution, the sodium content of soil leachate of high pressure solid soil is higher than that of soil sample with higher dry density. The concentration of potassium, calcium and magnesium is lower than that of low compaction soil, and the content of calcium is the highest in the leachate, followed by the concentration of sodium and magnesium, and the concentration of potassium is the lowest.
【學(xué)位授予單位】：合肥工業(yè)大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU442

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