【作者】 宋焕宇；

【导师】 朱宏平；

【作者基本信息】 华中科技大学 ， 结构工程， 2007， 博士

【摘要】 由于地形、地貌条件复杂,高填方成为山区公路一种常见的结构型式。为了避免高填方路基过度沉降变形甚至失稳滑塌等地质灾害发生,急需对设计和施工中的相关技术难题开展研究。依托实际工程,对粗粒土的变形特性和强度特性、高填方填筑体沉降计算方法、高边坡与陡斜坡路堤稳定性计算方法、高路堤变形控制与边坡稳定成套技术等问题进行研究,具有重要的理论意义和工程实用价值。本文依托实际工程,针对粗粒土工程特性、本构模型和粗粒土高路堤的变形特性与稳定性及其处治措施开展了系统的研究,重点研究粗粒土斜坡高路堤的变形特性与稳定性,为粗粒土高填方路基的合理设计提供科学依据,直接指导工程实践,同时为进一步推动粗粒土土力学学科的发展做出学术上的贡献。主要研究内容和成果如下:以实际工程为依托,开展了室内大型三轴试验,对粗粒土的压缩特性和剪切特性进行了研究。结果表明,水对巨粒土的压缩特性和剪切特性有重要影响;应力-应变曲线表现为弱应变软化型或应变硬化型,其形态主要决定于围压的大小;粗粒土具有明显的剪胀和剪缩特性,抗剪强度随着应力水平变化,表现出非线性特性。对Naylor的K-G模型进行了修正,建立了能综合反映粗粒土剪胀性、应变软化性及应力水平影响的非线性本构模型。该模型采用分段函数分别描述粗粒土应变硬化和应变软化阶段,推导的剪切模量G t和体变模量K t是应力状态、应力比和应力增量比的函数,可以反映材料的剪胀性和应变软化特性。通过数值模拟与试验研究验证了本模型有效性和可靠性。采用建立的粗粒土改进K-G模型进行数值模拟分析,得到了不同填方高度和坡比下斜坡高路堤变形规律、地基坡度对斜坡高路堤变形的影响规律、地基覆盖层厚度及强度参数对斜坡高路堤变形的影响规律。探讨了分级填筑条件下粗粒土路堤压缩变形的实用计算方法,提出了考虑土层因压实所承受的前期固结压力的高填方沉降简化计算方法,并采用现场压实试验和路基沉降监测,验证所提出的计算方法。采用极限平衡法,开展粗粒土高填方路堤稳定性研究,得到了不同填方高度与坡比对平坦地基上高路堤斜坡稳定性的影响规律,原地基坡度和覆盖层对斜坡高路堤稳定性的影响规律,坡脚码砌和挡土墙对斜坡高路堤稳定性的影响规律。通过对坡脚码砌、坡脚挡土墙等侧向变形限制技术的数值模拟分析,得到了粗粒土高填方斜坡路堤侧向变形限制方法的实际效果及其影响因素。更多还原

【Abstract】 High embankment has become to a common structural style of roads in mountainous areas due to the complex topography conditions. In order to avoid geologic disasters resulting from excessive deformation or unstable landslide of the high filled foundations, it is urgent to study the related technical problems existing in design and construction of the high embankment. Therefore, depending on the practical projects, this dissertation carried out studies mainly about deformation and strength characteristics of the coarse grained soils, calculation method for settlement of the high filled body and stability of the high slopes and steep slants, deformation control of the high embankment and complete set of technique for slope stabilization. And these studies have very important theoretical and practical values.Depending on the practical projects, engineering characteristics and constitutive model of the coarse grained soils, deformation characteristics and stability of the high embankment filled by coarse grains soils as well as treatment method of the stability were all systemically studied. And the studies of the deformation characteristics and stability of the high embankment filled by coarse grained soils on sloping ground were especially focused on. Therefore, the studies of this dissertation provide scientific references for reasonable design of the high embankment and useful guides for engineering practice. Furthermore, the studies also contribute to further development of science of the coarse grained soil mechanics.The main contents and results of this dissertation include:Depending on the practical projects, large-sized triaxial tests were carried out in lab in order to study the compression and shear characteristics of the coarse grained soils. According to the test results, firstly, water has important influence to the compression and shear characteristics of massive grain soils. Secondly, the pattern of stress-strain curve is mainly weak strain-softening or strain-hardening style. And the patterns were determined by the around confining press. Finally, the coarse grained soils possess characteristics of shearing expand and shearing compression. And the shearing strength has nonlinear characteristics and varies with the strain level.The nonlinear constitutive model of coarse grained soils considering effects of characteristics of shearing expand, characteristics of strain softening and strain level was created by modifying the Naylor’s K-G model. The modified model describes the strain hardening and softening phases using sectional-function. The deduced shearing modulus Gt and volume change modulus Kt are functions of variables of stress state, stress ratio and incremental ratio of stress. And the modulus can also reflect the characteristics of shearing expand and strain softening. Validity and reliability of the modified model were verified by numerical modeling and test study.According to the numerical modeling and analysis using the modified K-G model, deformation rules of the high embankment on sloping ground with different filled heights and slope ratios, as well as effecting rules of slope gradient, cover thickness of foundation and strength parameter to the deformation of the high embankment on sloping ground were obtained.Practical calculation method of compression deformation of the high embankment step filled by coarse grained soils was discussed. Then, considering the consolidation pressure resulted from the soil compacting in the earlier stage, the simplified calculation method for settlement of the high embankment was put forward. And the method was verified by carrying out field compacting test and settlement monitoring of roadbeds.Stability of the high embankment filled by coarse grained soils was studied using limiting equilibrium method. Thus, effecting rules of the different filled heights and slope ratios to the stability of high embankment slope on plane foundations as well as effecting rules of slope gradient, cover thickness of foundation, toe blocks and retaining wall to the high embankment on sloping ground were all obtained.Via the numerical modeling and analysis for restriction technique of lateral deformation of the toe blocks, toe retaining wall, etc., actual effects and influencing factors of the restriction technique were obtained.更多还原