改良合肥膨胀土非饱和特性试验研究

发布时间：2018-01-12 11:35

本文关键词：改良合肥膨胀土非饱和特性试验研究　出处：《合肥工业大学》2017年硕士论文　论文类型：学位论文

【摘要】：目前我国的工程建设正处于高速发展时期,许多重大工程正在紧张施工与预备当中,然而工程中经常遇到由于土体含水量变化而导致的膨胀土问题。因此,本文对合肥膨胀土的非饱和性质进行了研究。非饱和土与饱和土之间最主要的不同源于基质吸力的存在,非饱和土强度中涵盖着吸力的重大贡献。因而,研究含水量与基质吸力之间关系,进而分析对非饱和土强度是极其有意义的研究课题。本文首先对合肥膨胀土的基本力学特性进行试验研究,试验包括对合肥膨胀土进行不固结不排水三轴试验、界限含水率试验以及自由膨胀率和滤纸法试验。在各项试验结论的基础上,对合肥膨胀土性质有基本的了解,为后续的改良合肥膨胀土提供研究基础。其次,本文通过国内外研究现状分析进一步通过在石灰及建筑渣土在不同掺量下的滤纸法试验研究了其土水特征曲线。最后本文通过非饱和直剪仪对合肥膨胀土进行了石灰改良以及建筑渣土在不同掺量的情况下非饱和直剪试验,研究了改良合肥膨胀土在不同吸力控制下的强度变化规律,作出了净法向应力-基质吸力-剪应力的三维包络面,进而讨论改良后的合肥膨胀土强度与吸力之间的关系。最后得到如下结论:(1)6%掺量的石灰对合肥膨胀土的膨胀性有很好的抑制效果;在建筑渣土改良试验中,随着建筑渣土的掺量增加,合肥膨胀土的膨胀性逐渐下降,故而在单纯考虑膨胀性的工程应用中,可较多掺加建筑渣土;(2)土水特征试验及拟合分析中,4%石灰掺量的系数是一个突变点,在建筑渣土由10%到12%再到15%的过程当中,基质吸力的拟合曲线截距和斜率都是呈现先减小再增大的趋势,本论文试验配比中建筑渣土的截距明显大于掺加石灰的改良合肥膨胀土且斜率明显小于石灰改良合肥膨胀土;(3)非饱和直剪试验获得了不同掺量的建筑渣土改良合肥膨胀土基质吸力-法向应力-剪切强度关系,分析得到掺加12%建筑渣土的合肥膨胀土在建筑渣土改良合肥膨胀土的研究中试较为理想的掺量。
[Abstract]:At present, the engineering construction of our country is in the period of high speed development, and many important projects are under intensive construction and preparation. However, the problems of expansive soil caused by the change of soil water content are often encountered in the engineering. In this paper, the unsaturated properties of expansive soils in Hefei are studied. The main difference between unsaturated soils and saturated soils is due to the existence of matrix suction, and the strength of unsaturated soils covers the important contribution of suction. It is very important to study the relationship between water content and matrix suction, and to analyze the strength of unsaturated soil. Firstly, the basic mechanical properties of expansive soil in Hefei are studied experimentally in this paper. The test includes unconsolidated and undrained triaxial test, limit water content test, free expansion rate and filter paper test. There is a basic understanding of the properties of expansive soil in Hefei, which provides a research basis for the subsequent improvement of expansive soil in Hefei. Secondly. In this paper, the soil water characteristic curves were studied by filter paper method with different content of lime and building residue. Finally, the unsaturated direct shear apparatus was used to study the expansive soil in Hefei. Lime improvement and unsaturated direct shear tests of building residuals with different contents. The change law of strength of improved expansive soil under different suction was studied, and the three dimensional envelope surface of net normal stress-matrix suction and shear stress was made. The relationship between the strength and suction of the improved expansive soil is discussed. In the improvement test of building residue, with the increase of the content of building residue, the expansive property of Hefei expansive soil decreases gradually, so in the engineering application of simple consideration of dilatability, the construction residue can be added more. (2) the coefficient of 4% lime content in soil-water characteristic test and fitting analysis is a abrupt point, in the process of building residue from 10% to 12% to 15%. The fitting curve intercept and slope of matrix suction showed the trend of decreasing first and then increasing. In this paper, the intercept of building residue is obviously larger than that of improved Hefei expansive soil mixed with lime, and the slope is obviously smaller than that of lime modified Hefei expansive soil. (3) unsaturated direct shear test has obtained the relationship between the matrix suction and normal stress-shear strength of the modified Hefei expansive soil with different contents of building residuum. The optimal amount of Hefei expansive soil mixed with 12% building residuum in the study of improving Hefei expansive soil by building residuum was obtained in this paper.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU443

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