【作者】 雷红军；

【导师】 张丙印； 于玉贞；

【作者基本信息】 清华大学 ， 土木工程， 2010， 博士

【摘要】 高土石坝心墙粘性土中应力状态复杂、存在大剪切变形区,可能对其渗透性和大坝安全产生不利影响。本文通过室内试验、理论分析和数值模拟,对高土石坝粘性土大剪切变形条件下的渗透特性展开研究。主要工作和成果如下:(1)研制了三轴渗透试验装置,进行了系列的试验研究了不同条件下粘性土大剪切变形后的渗透性变化规律。结果表明:所研制的三轴渗透试验装置可应用于试样大剪切变形后不同方向的渗透试验;土体渗透性随应力变形状态发生变化;周围压力和剪切变形对土体渗透性的变化特征具有显著的影响;在很大渗透坡降范围内,土体中渗流仍遵循达西定律。(2)对粘性土大剪切变形条件下渗透性变化规律进行了机理分析,提出了相应的数学模型,并与试验结果进行了对比分析。结果表明:土体孔隙比和结构变化是导致土体渗透性变化的主要原因;所提出的数学模型可反映土体大剪切变形后孔隙比和结构变化的影响,在等向固结条件下退化为“等向固结k线”;与试验结果的对比分析表明该数学模型是实用有效的。(3)研制了剪切接触渗流联合试验装置,进行了系列的粘性土-结构接触面剪切渗流试验,并对试验结果及机理进行了分析。结果表明:研制的剪切接触渗流联合试验装置可有效应用于粘性土-结构接触面大剪切变形后的接触渗流试验;不同的应力变形、水力坡降、接触类型及粗糙程度等条件均会对粘性土的接触渗流特性产生影响;表面缺陷及粗粒土存在时,接触面渗透性增强;对粘性土-结构接触面,当发生大剪切变形时可在临近的粘性土中产生“大剪切变形区”,从而影响粘性土-结构接触面的渗流特性。(4)将所提出的数学模型与Biot固结理论相结合,建立了土石坝应力变形及渗流场相互作用的计算方法,并编入有限元计算程序。结合两河口高心墙堆石坝工程,进行了心墙及接触粘性土的应力变形及渗流固结分析,结果表明:所提出的数学模型和计算方法可有效地用于高心墙土石坝应力变形及渗流场相互作用的数值模拟。更多还原

【Abstract】 The seepage property of clayey soil under complex stress and large shear deformation is one of the key issues of earth-rockfill dams. By combining laboratory tests, theoretical analysis and numerical simulations, the seepage characteristics of the clayey soil with large shear deformations were studied. The main results are as follows.1. A new triaxial seepage device was developed and a series of seepage tests on clayey soil with large shear deformation were conducted. The tests results indicate that: (1) The triaxial seepage device can be used effectively to conduct seepage tests on soil in three directions with large shear deformations. (2) The permeability of soil changes with the stress and strain states. (3) The permeabilities in different directions are different slightly and the confining pressure affects the permeability of soil evidently. The seepage follows Darcy’s law in a large range of hydraulic gradients used in the tests.2. The mechanism of the change of permeability in the tests was analyzed and a mathematical model for the permeability was proposed to simulate the test results. The results show that: (1) Variations of the void ratio and structure are the main factors to affect the permeability of the soil. (2) The mathematical model for the permeability can reflect the effects of the void ratio and structure of the soil. A boundary of the equation is the isotropic consolidation permeability line. (3) Comparisons with the tests results indicate that the proposed equation is practicable and effective.3. Another test device was developed for seepage tests on clayey soil-structure interface. A series of tests were performed and the results were analyzed. Effects of some factors were investigated and the mechanism was discussed. The tests results indicate that: (1) The test device can be effectively used in contact seepage tests on soil interface. (2) The permeability of the soil-structure interface is affected by stress, strain, hydraulic gradient, style of the interface and the roughness of the interface. (3) When there are surface defects or coarse soil in the clayey soil, the permeability of the interface increases. (4) The large shear deformation zone of the soil near the interface is the main factor to affect the permeability of the soil-structure interface, and the geometry of the interface, the physical and mechanical characteristics of the soil can also affect the interface permeability.4. The mathematical model for the permeability was combined with Biot’s consolidation theory and a method was proposed to calculate the stress, strain and seepage fields of earth-rockfill dams. The simulating results of Lianghekou core wall rockfill dam indicate that the model can be used effectively and reasonably in calculating the stress, strain and seepage fields of earth-rockfill dams.更多还原