非饱和粉砂抗拉强度特性研究

发布时间：2019-05-16 05:35

【摘要】：土体拉伸破坏是岩土工程领域中不可忽视的一个问题。但由于土体抗拉强度相对于抗剪强度而言,其值相对偏小,所以在实际工程应用中一般认为土体不能承受拉应力。另外,由于对抗拉强度的试验量测相对困难,国内外对其研究都较少,相关的研究文献也较为缺乏。近年来,随着我国经济的蓬勃发展,公路、机场、大坝、地铁的修建日益兴起,对建筑物或构筑物的抗拉和抗裂能力有了更高的要求,越来越多的工程问题牵涉到土体的抗拉强度,如地面开裂,土石坝心墙裂缝,水力劈裂等都是土体拉伸破坏的表现形式。因此,对于土体拉伸特性的深入研究不仅对完善土体的强度理论有着重要的理论意义,更是对解决复杂岩土工程问题有着重要的实际应用价值。本文以非饱和粉砂为研究对象,利用自主开发研制的土体抗拉强度试验装置,运用等速率单轴拉伸方法对非饱和粉砂的抗拉强度进行了系统的研究工作,开展了不同干密度和含水量条件下的非饱和土抗拉强度试验研究,在此基础上提出了非饱和土抗拉强度模型,并基于有限元程序对室内抗拉强度试验进行了数值模拟和分析。本文取得的主要研究成果如下： 1.自主开发研制了可对不同初始条件下非饱和土进行抗拉强度测试的非饱和土抗拉强度试验装置。利用该试验装置,开展了不同初始干密度和不同初始含水量条件下非饱和粉砂抗拉强度测试,通过试验得到了特定条件下非饱和粉砂在拉力作用下的拉伸作用力-时间曲线、位移-时间曲线、拉伸作用力-位移曲线和拉伸应力-应变曲线,并基于上述试验结果最终获得了不同初始干密度条件下上述非饱和粉砂抗拉强度-含水量关系曲线。 2.基于试验研究成果,揭示了非饱和粉砂抗拉强度随干密度和含水量的演化规律,并进一步基于土体内部微观结构的演化,分析得到了非饱和粉砂抗拉强度演化的微观机理。在此基础上提出了一个能考虑干密度和含水量影响的非饱和土抗拉强度预测模型,并利用试验数据对该模型的有效性和适用性进行了验证。 3.基于大型有限元分析软件ABAQUS,对上述非饱和土抗拉强度试验进行了有限元模拟分析,通过对上述室内抗拉强度试验进行建模,计算分析了试样在受力后的应力分布和拉伸变形,并将计算结果与试验结果进行对比,从而进一步对非饱和土抗拉强度演化规律与机理进行验证。
[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.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU441;TU411

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