返包式加筋陡坡高路堤筋土相互作用机理及稳定性研究
发布时间：2018-12-15 11:50
【摘要】：近年来,随着加筋土技术越来越广泛的应用,国内外学者对加筋土结构特性已进行了大量研究。由于岩土体特性及工程实践的复杂性,虽然取得了一定进展,但仍无法满足工程实践的需求。目前关于返包式加筋结构的研究多集中于单级或多级(近)直立路肩式加筋土挡墙,其填料多为粘土或砂土,对于加筋陡坡高路堤结构以及碎石土填料的研究还很少。基于以上认识,论文以西南山区一段高达22m的返包式加筋陡坡高路堤工程为依托,采用大型直剪试验、现场监测、数值模拟和离心机模型试验相结合的方法系统研究了返包式加筋陡坡高路堤的结构荷载状态、筋土相互作用特性、稳定性影响因素、结构变形破坏模式等关键问题,研究成果可以为类似返包式加筋路堤结构的优化设计和施工提供理论依据,具有重要的工程应用价值。论文所做工作及取得的主要成果如下:(1)通过粗粒土填料和土工格栅的界面剪切试验,揭示了筋土界面相互作用关系特性。随着含水量的增加,筋土界面剪切的内摩擦角逐渐降低,而粘聚力则先增大后减小;填料中粗颗粒含量与筋土界面剪切的内摩擦角和粘聚力均呈正相关关系;粗粒土填料加筋可以明显提高土体的粘聚力,但其内摩擦角会降低。(2)对依托工程返包式加筋陡坡高路堤进行了现场监测试验,分析了结构荷载状态和加筋体潜在破裂面,主要成果包括:加筋土中的筋材可以有效改善土体中的应力分布,减小基底垂直土压力;加筋体内部的应力状态在后期会重新调整而导致格栅应变减小;对于这种柔性返包式加筋体结构,由于其坡面变形受限较小,工后很长一段时期坡面变形都将处于发展期。(3)采用FLAC3D建立了不同工况下的数值计算模型,探讨了返包式加筋陡坡高路堤的加筋机理、稳定性影响因素及变形破坏特征,研究得出:在路基中铺设土工格栅能够显著降低路基的侧向变形;加筋可以改善路基内部剪应力的分布;加筋路堤坡度对土工格栅受拉状态有显著影响。(4)结合现场监测和数值模拟的相关结果,建立了不同工况下的离心机模型,针对返包式加筋路堤结构的稳定性影响因素、应力应变分布特征、变形破坏过程等开展系统研究,进一步验证了相关结论的可靠性。研究得出:在稳定状态内,加筋土结构内部的潜在微裂缝并不是沿标准的圆弧、直线或折线发展,而是受加筋及筋土接触面的影响呈现出复杂的分布形式;极限状态时,加筋边坡内部潜在破裂面呈圆弧型;直立加筋路堤结构设计时,不能简单地按照无筋路基的方法仅根据墙高和填土内摩擦角来确定0.3H型破裂面的位置,而应考虑加筋的影响并结合数值模拟的分析结果综合确定最危险破裂面位置。
[Abstract]:In recent years, with the more and more extensive application of reinforced soil technology, scholars at home and abroad have done a lot of research on the structural characteristics of reinforced soil. Because of the characteristics of rock and soil and the complexity of engineering practice, although some progress has been made, it is still unable to meet the requirements of engineering practice. At present, the research of backpack reinforced structure is mainly focused on single or multi-stage (near) vertical shoulder reinforced earth retaining wall, and its fillers are mostly clay or sandy soil, but the research on reinforced steep slope height embankment structure and gravel soil filler is still rare. Based on the above understanding, based on a 22m backpack reinforced steep slope high embankment project in southwest mountainous area, a large-scale direct shear test is adopted, and field monitoring is carried out. Based on numerical simulation and centrifuge model test, the key problems such as structural load state, interaction between reinforcement and soil, influence factors of stability, structural deformation and failure mode of the embankment with backpack reinforcement and steep slope are systematically studied. The research results can provide a theoretical basis for the optimal design and construction of similar reinforced embankment structure, and have important engineering application value. The main achievements of this paper are as follows: (1) through the interface shear tests of coarse grained soil filler and geogrid, the characteristics of the interaction between reinforcement and soil interface are revealed. With the increase of water content, the internal friction angle of the interfacial shear decreases gradually, while the cohesive force increases first and then decreases, and the content of coarse particles in the filler is positively correlated with the internal friction angle and cohesive force of the interfacial shear of the reinforced soil. The reinforcement of coarse grained soil filler can obviously increase the cohesive force of soil, but its internal friction angle will be reduced. (2) the field monitoring test is carried out on the embankment of steep slope with backpack reinforcement, and the load state of the structure and the potential fracture surface of the reinforced body are analyzed. The main results are as follows: the reinforcement in reinforced soil can effectively improve the stress distribution in the soil and reduce the vertical soil pressure of the base; The stress state inside the stiffened body will be readjusted at the later stage, resulting in the reduction of the grid strain. For this flexible backpack reinforced body structure, the slope deformation will be in the development stage for a long time after construction because of the small limit of slope deformation. (3) the numerical calculation model under different working conditions is established by using FLAC3D. This paper discusses the reinforcement mechanism, stability influence factors and deformation and failure characteristics of backpack reinforced steep slope high embankment. It is concluded that laying geogrid in the subgrade can significantly reduce the lateral deformation of the embankment; Reinforcement can improve the distribution of shear stress in subgrade. The slope of reinforced embankment has a significant effect on the tensile state of geogrid. (4) combined with the related results of field monitoring and numerical simulation, the centrifuge model under different working conditions is established, and the factors affecting the stability of backpack reinforced embankment structure are discussed. The characteristics of stress and strain distribution and the process of deformation and failure are systematically studied, which further verifies the reliability of the relevant conclusions. The results show that the potential micro-cracks in the reinforced soil structure are not developed along the standard arc, straight line or broken line in the stable state, but show complex distribution form due to the influence of the reinforced and reinforced soil interface. In the limit state, the potential fracture surface of reinforced slope is circular. When the vertical reinforced embankment structure is designed, the location of the 0.3H fracture surface can not be determined simply according to the method of unreinforced roadbed only according to the height of the wall and the angle of internal friction of the fill. The influence of reinforcement should be considered and the location of the most dangerous fracture surface should be determined synthetically with the results of numerical simulation.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U416.12
本文编号：2380587
[Abstract]:In recent years, with the more and more extensive application of reinforced soil technology, scholars at home and abroad have done a lot of research on the structural characteristics of reinforced soil. Because of the characteristics of rock and soil and the complexity of engineering practice, although some progress has been made, it is still unable to meet the requirements of engineering practice. At present, the research of backpack reinforced structure is mainly focused on single or multi-stage (near) vertical shoulder reinforced earth retaining wall, and its fillers are mostly clay or sandy soil, but the research on reinforced steep slope height embankment structure and gravel soil filler is still rare. Based on the above understanding, based on a 22m backpack reinforced steep slope high embankment project in southwest mountainous area, a large-scale direct shear test is adopted, and field monitoring is carried out. Based on numerical simulation and centrifuge model test, the key problems such as structural load state, interaction between reinforcement and soil, influence factors of stability, structural deformation and failure mode of the embankment with backpack reinforcement and steep slope are systematically studied. The research results can provide a theoretical basis for the optimal design and construction of similar reinforced embankment structure, and have important engineering application value. The main achievements of this paper are as follows: (1) through the interface shear tests of coarse grained soil filler and geogrid, the characteristics of the interaction between reinforcement and soil interface are revealed. With the increase of water content, the internal friction angle of the interfacial shear decreases gradually, while the cohesive force increases first and then decreases, and the content of coarse particles in the filler is positively correlated with the internal friction angle and cohesive force of the interfacial shear of the reinforced soil. The reinforcement of coarse grained soil filler can obviously increase the cohesive force of soil, but its internal friction angle will be reduced. (2) the field monitoring test is carried out on the embankment of steep slope with backpack reinforcement, and the load state of the structure and the potential fracture surface of the reinforced body are analyzed. The main results are as follows: the reinforcement in reinforced soil can effectively improve the stress distribution in the soil and reduce the vertical soil pressure of the base; The stress state inside the stiffened body will be readjusted at the later stage, resulting in the reduction of the grid strain. For this flexible backpack reinforced body structure, the slope deformation will be in the development stage for a long time after construction because of the small limit of slope deformation. (3) the numerical calculation model under different working conditions is established by using FLAC3D. This paper discusses the reinforcement mechanism, stability influence factors and deformation and failure characteristics of backpack reinforced steep slope high embankment. It is concluded that laying geogrid in the subgrade can significantly reduce the lateral deformation of the embankment; Reinforcement can improve the distribution of shear stress in subgrade. The slope of reinforced embankment has a significant effect on the tensile state of geogrid. (4) combined with the related results of field monitoring and numerical simulation, the centrifuge model under different working conditions is established, and the factors affecting the stability of backpack reinforced embankment structure are discussed. The characteristics of stress and strain distribution and the process of deformation and failure are systematically studied, which further verifies the reliability of the relevant conclusions. The results show that the potential micro-cracks in the reinforced soil structure are not developed along the standard arc, straight line or broken line in the stable state, but show complex distribution form due to the influence of the reinforced and reinforced soil interface. In the limit state, the potential fracture surface of reinforced slope is circular. When the vertical reinforced embankment structure is designed, the location of the 0.3H fracture surface can not be determined simply according to the method of unreinforced roadbed only according to the height of the wall and the angle of internal friction of the fill. The influence of reinforcement should be considered and the location of the most dangerous fracture surface should be determined synthetically with the results of numerical simulation.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U416.12
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