基于土-结构相互作用的山区公路路基拓宽改建力学行为数值模拟

发布时间：2018-09-12 20:34

【摘要】：对于山区公路路基拓宽改建工程,控制新旧路基顶面差异沉降和保证路基稳定性至关重要。围绕着这一工程目的,本文开展了基于土-结构相互作用的山区公路路基拓宽改建力学行为的数值模拟及其工程处治对策研究。山区公路路基单侧拼接式拓宽改建多下设包括衡重式挡土墙在内的支挡建筑物于新路基外侧。运用Phase2有限元软件,引入Joint单元,构建描述土-墙相互作用的数值模型,采用两步走、墙面施加非零位移约束方式模拟挡土墙平动加绕墙趾转动(RBT)主动外倾变位,分析挡土墙不同主动外倾变位量对新旧路基顶面差异沉降的影响,并与土工离心模型试验成果进行验证比较。结果表明：下设的刚性挡土墙与新老路基相互作用,共同依存。数值模拟反映当主动外倾量与墙高之比为1%～3%时,由挡土墙主动外倾变位产生的附加差异沉降占总差异沉降的51%～67%。结合山区公路路基拓宽改建多下设刚性挡土墙的特殊性,运用Phase2有限元软件,采用强度折减法,引入joint, structural interface单元,对山区公路路基拓宽加筋稳定性开展数值模拟,探究填土、土工格栅、土-格栅相互作用三者动态演变规律及对路基稳定性的影响,并以土工离心模型试验成果进行验证。结果表明：铺设土工格栅可削减路基面沉降、限制墙体外倾,增强路基稳定性,并且填土、土工格栅、土-格栅界面对路基稳定性的影响权重动态变化。随着强度折减系数SRF的增加,填土-土工格栅界面单元虽然会滑移失效,但未决定路基稳定性,而衡重台外边缘上层位处土工格栅被拉断失效,轴向拉力骤降,直接导致拓宽路基失稳破坏。结合我国已完成的路基拓宽工程实践经验及相关领域研究,初步提出了山区公路路基拓宽改建工程对策的基本技术思路,总结了控制新旧路基顶面差异沉降及路基稳定性的工程处治措施。主要包括：路基内部加筋,新旧路基结合部台阶设置,路基填料选择与压实工艺控制,半路半桥结构设置,挡土墙设置,地基处理,拓宽路基边坡防护等工程处治对策。
[Abstract]:It is very important to control the differential settlement of new and old roadbed top surface and ensure the stability of roadbed for the widening and rebuilding of highway roadbed in mountainous area. Based on the soil-structure interaction, the numerical simulation of the mechanical behavior of roadbed widening and rebuilding in mountainous area and the countermeasures of engineering treatment are carried out in this paper. In the mountainous area highway roadbed, most of the retaining structures, including the counterweight retaining wall, are located on the outside of the new roadbed. Using Phase2 finite element software and introducing Joint element, a numerical model to describe the soil-wall interaction is constructed. Using two-step walk and non-zero displacement constraint on the wall surface, the lateral movement of retaining wall and the rotation of (RBT) active extraversion around the toe of the wall are simulated. The influence of different active extraversion of retaining wall on the differential settlement of new and old roadbed top surface is analyzed and compared with the results of geotechnical centrifuge model test. The results show that the rigid retaining wall interacts with the new and old subgrade and depends on each other. Numerical simulation shows that when the ratio of active extraversion to wall height is 1 ~ 3, the additional differential settlement caused by active extraversion of retaining wall accounts for 51% of the total differential settlement. Combined with the particularity of the rigid retaining wall under the widening and rebuilding of highway roadbed in mountainous area, using Phase2 finite element software, using strength reduction method and introducing joint, structural interface element, the stability of widening and reinforcement of highway roadbed in mountainous area is simulated numerically, and the fill soil is explored. The dynamic evolution law of geogrid and soil-grid interaction and its influence on the stability of roadbed are verified by the results of geotechnical centrifugal model test. The results show that laying geogrid can reduce the settlement of roadbed, limit the external inclination of wall, enhance the stability of roadbed, and dynamic change of the influence weight of soil, geogrid and soil-grid interface on the stability of roadbed. With the increase of strength reduction coefficient (SRF), the interfacial element of filling earth and geogrid will slip, but it will not determine the stability of roadbed, but the geogrid will be broken and the axial tensile force will drop sharply at the upper part of the outer edge of the counterbalance platform. It directly leads to the failure of widening roadbed. Based on the practical experience of roadbed widening project and the research on related fields, the basic technical thinking of roadbed widening and rebuilding engineering in mountainous area is put forward. The engineering treatment measures to control the differential settlement and stability of the new and old subgrade are summarized. It mainly includes: the interior reinforcement of the roadbed, the installation of steps in the new and old roadbed, the selection of subgrade filler and the control of compaction technology, the construction of half-bridge structure, the setting of retaining wall, the treatment of foundation, the widening of subgrade slope protection and so on.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U416.1

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