非飽和粉砂抗拉強度特性研究
發(fā)布時間：2019-05-16 05:35
【摘要】：土體拉伸破壞是巖土工程領(lǐng)域中不可忽視的一個問題。但由于土體抗拉強度相對于抗剪強度而言,其值相對偏小,所以在實際工程應用中一般認為土體不能承受拉應力。另外,由于對抗拉強度的試驗量測相對困難,國內(nèi)外對其研究都較少,相關(guān)的研究文獻也較為缺乏。近年來,隨著我國經(jīng)濟的蓬勃發(fā)展,公路、機場、大壩、地鐵的修建日益興起,對建筑物或構(gòu)筑物的抗拉和抗裂能力有了更高的要求,越來越多的工程問題牽涉到土體的抗拉強度,如地面開裂,土石壩心墻裂縫,水力劈裂等都是土體拉伸破壞的表現(xiàn)形式。因此,對于土體拉伸特性的深入研究不僅對完善土體的強度理論有著重要的理論意義,更是對解決復雜巖土工程問題有著重要的實際應用價值。 本文以非飽和粉砂為研究對象,利用自主開發(fā)研制的土體抗拉強度試驗裝置,運用等速率單軸拉伸方法對非飽和粉砂的抗拉強度進行了系統(tǒng)的研究工作,開展了不同干密度和含水量條件下的非飽和土抗拉強度試驗研究,在此基礎(chǔ)上提出了非飽和土抗拉強度模型,并基于有限元程序?qū)κ覂?nèi)抗拉強度試驗進行了數(shù)值模擬和分析。 本文取得的主要研究成果如下： 1.自主開發(fā)研制了可對不同初始條件下非飽和土進行抗拉強度測試的非飽和土抗拉強度試驗裝置。利用該試驗裝置,開展了不同初始干密度和不同初始含水量條件下非飽和粉砂抗拉強度測試,通過試驗得到了特定條件下非飽和粉砂在拉力作用下的拉伸作用力-時間曲線、位移-時間曲線、拉伸作用力-位移曲線和拉伸應力-應變曲線,并基于上述試驗結(jié)果最終獲得了不同初始干密度條件下上述非飽和粉砂抗拉強度-含水量關(guān)系曲線。 2.基于試驗研究成果,揭示了非飽和粉砂抗拉強度隨干密度和含水量的演化規(guī)律,并進一步基于土體內(nèi)部微觀結(jié)構(gòu)的演化,分析得到了非飽和粉砂抗拉強度演化的微觀機理。在此基礎(chǔ)上提出了一個能考慮干密度和含水量影響的非飽和土抗拉強度預測模型,并利用試驗數(shù)據(jù)對該模型的有效性和適用性進行了驗證。 3.基于大型有限元分析軟件ABAQUS,對上述非飽和土抗拉強度試驗進行了有限元模擬分析,通過對上述室內(nèi)抗拉強度試驗進行建模,計算分析了試樣在受力后的應力分布和拉伸變形,并將計算結(jié)果與試驗結(jié)果進行對比,從而進一步對非飽和土抗拉強度演化規(guī)律與機理進行驗證。
[Abstract]:Tensile failure of soil is a problem that can not be ignored in the field of geotechnical engineering. However, because the tensile strength of soil is relatively small compared with the shear strength, it is generally considered that the soil can not bear the tensile stress in practical engineering application. In addition, because the experimental measurement of tensile strength is relatively difficult, there is little research on it at home and abroad, and the related research literature is also relatively scarce. In recent years, with the vigorous development of economy in our country, the construction of roads, airports, dams and subways is rising day by day, which has higher requirements for the tensile and crack resistance of buildings or structures. More and more engineering problems involve the tensile strength of soil, such as ground cracking, cracks in the core wall of earth-rock dam, hydraulic fracturing and so on. Therefore, the in-depth study of tensile properties of soil not only has important theoretical significance for perfecting the strength theory of soil, but also has important practical application value for solving complex geotechnical engineering problems. In this paper, the tensile strength of saturated silt is systematically studied by using the tensile strength test device of soil developed by ourselves, and the tensile strength of saturated silt is systematically studied by using the uniaxial tensile method of equal rate. The tensile strength of unsaturated soil under different dry density and water content was studied. On this basis, the tensile strength model of unsaturated soil was put forward, and the indoor tensile strength test was simulated and analyzed based on the finite element program. The main research results of this paper are as follows: 1. A device for testing the tensile strength of unsaturated soils under different initial conditions has been developed. The tensile strength of unsaturated silt under different initial dry density and different initial water content was tested by using the test device, and the tensile force-time curve of unsaturated silt under specific conditions was obtained. Displacement-time curve, tensile force-displacement curve and tensile stress-strain curve, and based on the above test results, the relationship between tensile strength and water content of the above saturated silt under different initial dry density conditions was obtained. 2. Based on the experimental results, the evolution of tensile strength of unsaturated silt with dry density and water content is revealed, and the microscopic mechanism of tensile strength evolution of saturated silt is analyzed based on the evolution of internal microstructure of soil. On this basis, a prediction model of tensile strength of unsaturated soil considering the effects of dry density and water content is proposed, and the validity and applicability of the model are verified by the experimental data. 3. Based on the large-scale finite element analysis software ABAQUS, the finite element simulation analysis of the tensile strength test of the above saturated soil is carried out. Through the modeling of the indoor tensile strength test, the stress distribution and tensile deformation of the specimen after stress are calculated and analyzed. The calculated results are compared with the experimental results, and the evolution law and mechanism of tensile strength of unsaturated soils are further verified.
【學位授予單位】：北京交通大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU441;TU411
本文編號：2478055
[Abstract]:Tensile failure of soil is a problem that can not be ignored in the field of geotechnical engineering. However, because the tensile strength of soil is relatively small compared with the shear strength, it is generally considered that the soil can not bear the tensile stress in practical engineering application. In addition, because the experimental measurement of tensile strength is relatively difficult, there is little research on it at home and abroad, and the related research literature is also relatively scarce. In recent years, with the vigorous development of economy in our country, the construction of roads, airports, dams and subways is rising day by day, which has higher requirements for the tensile and crack resistance of buildings or structures. More and more engineering problems involve the tensile strength of soil, such as ground cracking, cracks in the core wall of earth-rock dam, hydraulic fracturing and so on. Therefore, the in-depth study of tensile properties of soil not only has important theoretical significance for perfecting the strength theory of soil, but also has important practical application value for solving complex geotechnical engineering problems. In this paper, the tensile strength of saturated silt is systematically studied by using the tensile strength test device of soil developed by ourselves, and the tensile strength of saturated silt is systematically studied by using the uniaxial tensile method of equal rate. The tensile strength of unsaturated soil under different dry density and water content was studied. On this basis, the tensile strength model of unsaturated soil was put forward, and the indoor tensile strength test was simulated and analyzed based on the finite element program. The main research results of this paper are as follows: 1. A device for testing the tensile strength of unsaturated soils under different initial conditions has been developed. The tensile strength of unsaturated silt under different initial dry density and different initial water content was tested by using the test device, and the tensile force-time curve of unsaturated silt under specific conditions was obtained. Displacement-time curve, tensile force-displacement curve and tensile stress-strain curve, and based on the above test results, the relationship between tensile strength and water content of the above saturated silt under different initial dry density conditions was obtained. 2. Based on the experimental results, the evolution of tensile strength of unsaturated silt with dry density and water content is revealed, and the microscopic mechanism of tensile strength evolution of saturated silt is analyzed based on the evolution of internal microstructure of soil. On this basis, a prediction model of tensile strength of unsaturated soil considering the effects of dry density and water content is proposed, and the validity and applicability of the model are verified by the experimental data. 3. Based on the large-scale finite element analysis software ABAQUS, the finite element simulation analysis of the tensile strength test of the above saturated soil is carried out. Through the modeling of the indoor tensile strength test, the stress distribution and tensile deformation of the specimen after stress are calculated and analyzed. The calculated results are compared with the experimental results, and the evolution law and mechanism of tensile strength of unsaturated soils are further verified.
【學位授予單位】：北京交通大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU441;TU411
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