【作者】 吕大伟；

【导师】 徐林荣；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2009， 博士

【摘要】 我国西部高山高纬度地区广泛分布有第四纪冰水堆积地层,在冰水堆积物地区修建高速公路,工程经验较少,前期研究工作也未见相关报导。同时,西部地区地质条件复杂、地震活动频繁,在高速公路的修筑中必须考虑这些问题。因此,研究冰水堆积物这种新填料的工程特点,获取其路基工程性状具有重要的理论意义和应用价值。本文依托交通部科技示范工程—雅泸高速公路,采用现场调查、室内试验、现场试验、理论分析和数值模拟相结合的方法,对冰水堆积物粗粒土的岩土工程特性及其工程性状进行研究。主要工作及成果如下:1.在系统总结冰水堆积物分类及其成因、特点的基础上,基于现场调查及勘察,确定了雅泸高速公路全线冰水堆积物的主要成因;根据室内试验及现场动力触探结果,对雅泸路沿线冰水堆积物72个取样点的土体参数进行统计分析,获取了冰水堆积物基本物理力学性质及土类、天然状态、粗细料比例、颗粒大小/形状等对其影响规律。2.将分形理论引入冰水堆积物粗粒土级配分析中,采用随机—模糊线性回归方法确定其粒度分布分维,对其分形特征进行研究:确定了分维值范围及其与土类和埋深的关系;将冰水堆积物粗粒土分形结构分为直线型、V字型、N字型和∧字型,可据此对土样进行初步定名;得出冰水堆积物粗粒土是一种逐级套嵌的多重分形结构;结合Tailot理想压实级配曲线,提出其作为路基填料的理想分维值范围,便于指导填料的级配改良。3.针对冰水堆积物粗粒土的散粒体特征,应用散体力学理论对其本构关系进行研究;基于前述研究成果,使用分形理论体现其多重分形特征,引入粒状修正系数描述颗粒表面形状,基于虚功原理获取宏观应力张量与微观组构量的关系;建立了能够反映冰水堆积物粗粒土多重分形特征、颗粒特点及微观组构的三维条件下各向同性散体本构模型,并将其用于冰水堆积物粗粒土路堤沉降预测。4.针对所建立的散体本构模型,通过灰色关联度分析,获取了土体当量粒径、粒状修正系数、孔隙比、法向及切向接触刚度等对冰水堆积物粗粒土力学特性的影响规律;并据此分析了利用机械压实增强路基抵抗变形及破坏能力的机理。5.考虑含石率、含泥量、压实度、加筋层数4种因素,选用正交设计表L₉（3⁴）,进行了冰水堆积物粗粒土大型三轴剪切试验:1)基于雅泸高速全线72个冰水堆积物取样点的级配曲线,总结了9种代表性级配,确定了每种级配的最优含水量,并提出了施工中允许含水量误差控制标准;2)得出在试验条件下,摩尔强度包线接近直线,强度参数c值在67～102kPa范围内,应力应变曲线呈应变软化特征;3)获取了各因素对强度参数的影响规律,得出存在最优含泥量,使冰水堆积物粗粒土强度最高,据此提出了施工中应确保含泥量的建议。6.基于应力路径法及粘弹性理论,采用现场动力触探、三轴试验及散体本构关系等得到的变形参数,对冰水堆积物粗粒土路基进行沉降预测,并探讨了压实度对路堤工后沉降的影响;得到了路基沉降各组成部分大小及所占比例;提出可利用由本文散体本构模型得到的模量估算路堤自身压密沉降。7.采用有限差分软件FLAC^2D5.0分析冰水堆积物加筋陡坡路堤地震动力反应特性。讨论了网格尺寸及形状、边界设置、阻尼选择及参数确定、人工地震波合成、修正及输入等应特别注意的问题;对加筋前后路基的地震动力反应特性,包括水平位移、速度、加速度、危险区域及动剪应力分布等进行对比;获取了满足冰水堆积物加筋路基抗震要求的最优加筋间距等设计参数。更多还原

【Abstract】 The Quaternary fluvioglacial deposited stratum is widely distributed in the high mountain and high latitude area of Western China. The project experience of building highway in fluvioglacial deposits area is deficient, and relative research about this field is not found. Meanwhile, the geological condition is complicated and the seismic activity is frequent in Western China. These questions must be considered when building highways. So, it is very important for theory and application to study project characteristics of fluvioglacial deposits - the new embankment fill material, and obtain its behavior in subgrade engineering. Relyed on the scientific and technological demonstration project of the Ministry of Transport of P.R.China - Yalu highway, through field survey, laboratory experiments, in-situ tests, theoritical analysis and numerical simulation, the characteristics of fluvioglacial deposits and its engineering behavior in highway were researched. The main contents include followings:1. The main causes of fluvioglacial deposits in YaLu highway were confirmed based on field survey, investigation and systemically summarizing the classification, causes and characteristics of fluvioglacial deposits. On the basis of the results of laboratory experiments and in-situ DPT, the soil parameters of 72 soil samples along the YaLu highway were statistically analyzed, and furthermore, the basic physico-mechanical properties of fluvioglacial deposits and the influence of soil type, natural state, the content of coarse （fine） grain and particle size & shape, etc. on fluvioglacial deposits was obtained.2. The fractal theory was introduced to analyze the grain composition of fluvioglacial deposited coarse grained soil. The fractal dimensions were obtained by the random-fuzzy linear regression method. The range of fractal dimension values and the relation between the fractal dimensions and soil types and buried depth; the fractal structure of fluvioglacial deposited coarse grained soil was classified into beeline type, V style, N style and A style, and the soil can be named tentatively by this; it was obtained that fluvioglacial deposited coarse grained soil was a kind of multi-fractal structure; based on Tailot ideal grain composition curve, the ideal fractal dimension value range of fluvioglacial deposited coarse grained soil was suggested so as to instruct the improving of fill.3. According to the granular characteristic of fluvioglacial deposited coarse grained soil, granular material theory was employed to study the constitutive relation of this kind of material. Fractal theory was introduced to reflect the multi-fractal characteristic of influvioglacial deposits. The shape of particle surface of fluvioglacial deposited coarse grained soil was described through the shape correction coefficient. Based on the virtual work principle, the relationship between the macroscopic stress tensor and microscopic fabric was obtained. Finally, a three-dimensional isotropy granular constitutive model was proposed, which could reflect the multi-fractal characteristic, particle characteristic and microscopic fabric and of fluvioglacial deposited coarse grained soil. This model was used to predict the settlement of fluvioglacial deposited coarse grained soil embankment.4. According to the granular material constitutive model established above, through grey relational grade analysis, the influencing rules of some parameters （including the equivalent particle size, coefficient of graininess revising, void ratio, normal contact stiffness and tangential contact stiffness） on the mechanic characteristic of fluvioglacial deposited coarse grained soil were obtained. And then, the mechanism of enhancing embankment’s ability in resisting against deformation and failure by mechanical compaction was analyzed.5. Large-scale triaxial sheer tests of fluvioglacial deposited coarse grained soil were conducted based on the orthogonal design table L₉（3⁴） considering 4 factors, including content ratio of rock, content ratio of mud, compactness and reinforced layers.1) 9 kinds of representative grading curves were summed up from the grain composition curves of 72 soil samples of fluvioglacial deposits along the Yalu highway, the optimum water content were determined and the control standard on the permissible error of water content in construction being proposed.2) Under this experiment condition, the Mohr strength envelope of fluvioglacial deposited coarse grained soil was close to a straight line, the value of c in sheer strength would be in the range of 67-102kPa, and the stress-strain carve showed the characteristic of strain softening.3) The influencing rules of 4 factors on strength parameters were obtained and it was found out that there was a optimal mud content, which could make the strength of fluvioglacial deposited coarse grained soil reach the peak. So it was proposed that the mud content should be ensured during the construction.6. Based on stress path method and viscoelasticity theory, adopting the deformation parameters obtained by DPT, triaxial shear test and granular material constitutive model, the settlement of fluvioglacial deposited coarse grained soil embankment was predicted and the influence of compact degree on post-construction settlement was discussed. The amount and ratio of each portion of settlement were obtained. And it was suggested the modulus of granular constitute model of fluvioglacial deposited coarse grained soil be used to evaluate the self-compact settlement of embankment.7. Finite difference software FLAC^2D 5.0 was adopt to analyze the seismic dynamic response on reinforced fluvioglacial deposited coarse grained soil embankment on steep slope. Some key points about the option of numerical analysis were discussed, such as the size and shape of difference mesh, the setting of boundary, the determining of damp, and the producing, rectifying and input of manual shaking wave. Comparison analyses were conducted to discuss the characteristics of seismic dynamic response in embankment pre-and-post reinforcing, including horizontal displacement, velocity, accelerate, risk area and distribution of dynamic sheer stress. Finally, the design parameters such as the optimal distance between reinforced layers were obtained.更多还原