重塑非飽和坡積黏土土水特征曲線及強度特性的試驗研究
發(fā)布時間：2018-08-26 19:14
【摘要】：非飽和坡積土的力學性能和強度特性是目前巖土工程界研究的熱點和難點,由于非飽和土的工程性質(zhì)復雜,以及對非飽和土的研究理論還不夠完善,由非飽和土引起的邊坡塌陷和泥石流等災(zāi)害問題不斷頻發(fā),這給人民的生命財產(chǎn)安全帶來了嚴重的威脅。針對這一問題,本文以湘潭北站附近某邊坡的坡積土為研究對象,開展了多組基質(zhì)吸力、飽和度和干密度的抗剪強度試驗及重塑非飽和坡積黏土的土水特征曲線試驗,對其力學性能和強度特性進行了系統(tǒng)而深入的研究,并建立了各自的強度理論公式,可為工程實踐提供參考,本文研究成果如下:(1)對所取的坡積土進行了基本的物理特性試驗,確定該土樣的比重、液限、塑限、最大干密度、最佳含水率、不均勻系數(shù)、曲率系數(shù)等基本物理指標,最終判定該坡積土為級配不良的含砂高液限黏土,代號為CHS。(2)建立了土水特征曲線數(shù)學模型,運用該模型預測出土水特征曲線的殘余段,并與具有代表性的Gardner模型、Van Genucheten模型、Mckee和Bumb模型擬合的土水特征曲線進行了比較分析,論證了本文所建數(shù)學模型的可靠性和合理性。(3)通過非飽和應(yīng)變控制式直剪儀試驗,發(fā)現(xiàn)重塑非飽和坡積黏土的固結(jié)量隨著荷載的施加而急劇增大,最終趨于穩(wěn)定。剪應(yīng)力應(yīng)變曲線在較低應(yīng)力下呈剪切軟化,在較高應(yīng)力下,先表現(xiàn)為剪切硬化,后表現(xiàn)為剪切塑性�？辜魪姸入S著基質(zhì)吸力的增大呈分段特性,在各階段呈線性增長。(4)在上述試驗基礎(chǔ)上,建立了重塑非飽和坡積黏土分段的抗剪強度破壞包絡(luò)面和分段的重塑非飽和坡積黏土抗剪強度公式。其中,干密度越大,重塑非飽和坡積黏土的總應(yīng)力抗剪強度越高。當飽和度從飽和狀態(tài)到殘余狀態(tài)時,重塑非飽和坡積黏土的抗剪強度表現(xiàn)為先增加,后減小,最終趨于穩(wěn)定。(5)重塑的坡積黏土的黏聚力從飽和狀態(tài)到殘余狀態(tài),也呈現(xiàn)增、減和穩(wěn)定三個階段,變化規(guī)律近似呈正態(tài)分布,內(nèi)摩擦角隨著飽和度的增大,呈現(xiàn)非線性減小。同時發(fā)現(xiàn),黏聚力隨著干密度的增大而增大,但是內(nèi)摩擦角隨干密度的增加,變化不大。
[Abstract]:The mechanical properties and strength characteristics of unsaturated slope soil are hot and difficult in geotechnical engineering field at present. Because of the complexity of engineering properties of unsaturated soil, and the research theory of unsaturated soil is not perfect enough, Slope collapse and debris flow caused by unsaturated soil are constantly occurring, which brings serious threat to the safety of people's life and property. In order to solve this problem, this paper takes the slope soil of a slope near Xiangtan North Station as the research object, and carries out the shear strength test of multiple groups of matrix suction, saturation and dry density, and the soil-water characteristic curve test of remolding unsaturated slope clay. The mechanical properties and strength properties of the soils are studied systematically and deeply, and their strength theoretical formulas are established, which can be used as reference for engineering practice. The research results are as follows: (1) the basic physical properties of the slope soil are tested. The specific gravity, liquid limit, plastic limit, maximum dry density, optimum moisture content, uneven coefficient, curvature coefficient and other basic physical indexes of the soil sample are determined. The mathematical model of soil-water characteristic curve was established by code name CHS. (2), and the residual section of soil-water characteristic curve was predicted by using this model. It was compared with the soil-water characteristic curve fitted by Gardner model Van Genucheten model and Bumb model. The reliability and reasonableness of the mathematical model established in this paper are demonstrated. (3) through the experiment of the unsaturated strain controlled direct shear instrument, it is found that the consolidation of the remolded unsaturated slope clay increases sharply with the application of the load, and finally tends to be stable. The shear stress-strain curve shows shear softening at lower stress and shear hardening at higher stress, then shear plasticity. The shear strength increases linearly with the increase of the matrix suction. (4) based on the above experiments, the shear strength increases linearly. The shear failure envelope surface of remolded unsaturated slope clay and the formula of shear strength of remolded unsaturated slope clay are established. The higher the dry density, the higher the total stress shear strength of remolded unsaturated slope clay. When saturation is from saturation state to residual state, the shear strength of remolded unsaturated slope clay increases first, then decreases, and finally tends to be stable. (5) the cohesive force of remolded slope clay increases from saturation state to residual state. In the three stages of subtraction and stabilization, the law of variation is approximately normal distribution, and the angle of internal friction decreases with the increase of saturation. It is also found that the cohesion increases with the increase of dry density, but the angle of internal friction does not change with the increase of dry density.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU43
本文編號：2205896
[Abstract]:The mechanical properties and strength characteristics of unsaturated slope soil are hot and difficult in geotechnical engineering field at present. Because of the complexity of engineering properties of unsaturated soil, and the research theory of unsaturated soil is not perfect enough, Slope collapse and debris flow caused by unsaturated soil are constantly occurring, which brings serious threat to the safety of people's life and property. In order to solve this problem, this paper takes the slope soil of a slope near Xiangtan North Station as the research object, and carries out the shear strength test of multiple groups of matrix suction, saturation and dry density, and the soil-water characteristic curve test of remolding unsaturated slope clay. The mechanical properties and strength properties of the soils are studied systematically and deeply, and their strength theoretical formulas are established, which can be used as reference for engineering practice. The research results are as follows: (1) the basic physical properties of the slope soil are tested. The specific gravity, liquid limit, plastic limit, maximum dry density, optimum moisture content, uneven coefficient, curvature coefficient and other basic physical indexes of the soil sample are determined. The mathematical model of soil-water characteristic curve was established by code name CHS. (2), and the residual section of soil-water characteristic curve was predicted by using this model. It was compared with the soil-water characteristic curve fitted by Gardner model Van Genucheten model and Bumb model. The reliability and reasonableness of the mathematical model established in this paper are demonstrated. (3) through the experiment of the unsaturated strain controlled direct shear instrument, it is found that the consolidation of the remolded unsaturated slope clay increases sharply with the application of the load, and finally tends to be stable. The shear stress-strain curve shows shear softening at lower stress and shear hardening at higher stress, then shear plasticity. The shear strength increases linearly with the increase of the matrix suction. (4) based on the above experiments, the shear strength increases linearly. The shear failure envelope surface of remolded unsaturated slope clay and the formula of shear strength of remolded unsaturated slope clay are established. The higher the dry density, the higher the total stress shear strength of remolded unsaturated slope clay. When saturation is from saturation state to residual state, the shear strength of remolded unsaturated slope clay increases first, then decreases, and finally tends to be stable. (5) the cohesive force of remolded slope clay increases from saturation state to residual state. In the three stages of subtraction and stabilization, the law of variation is approximately normal distribution, and the angle of internal friction decreases with the increase of saturation. It is also found that the cohesion increases with the increase of dry density, but the angle of internal friction does not change with the increase of dry density.
【學位授予單位】：湘潭大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU43
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