Numerical Simulation on Stability Development of Geogrid Reinforced Widening Embankment with Rigid Retaining Wall
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摘要: 为阐释山区公路刚性挡土墙拓宽加筋路基稳定性的动态演变规律及机理，结合山区公路路基拓宽改建多外设刚性挡土墙的特殊性，运用Phase2有限元软件，考虑土-结构相互作用，建立数值模型，所获加筋效果相关结论经离心模型试验宏观验证，开展基于剪切强度折减法的山区公路拓宽加筋路基稳定性分析，探究填土、土工格栅和填土-土工格栅界面三者力学响应动态演变规律及其对路基稳定性的影响. 研究结果表明：铺设土工格栅后路基面差异沉降减小47.1%，墙体最大外倾减小65.4%，路基稳定安全系数提高12.8%；随着剪切强度折减系数增加，填土-土工格栅界面单元滑移失效，但未决定路基稳定性，上层位衡重台外边缘处土工格栅的拉断失效将导致轴向拉力骤降，诱发拓宽路基失稳破坏.Abstract: Rigid retaining walls are widely used in highway widening embankments in mountainous regions. To interpret the dynamic development law and mechanics of geogrid reinforced widening embankment with the rigid retaining wall in mountainous region, combined with the particularity of the rigid retaining wall, the finite element software Phase2 and strength reduction method were employed to analyse the stability of geogrid reinforced highway widening embankment in such regions. The interactions between soil and structure were introduced in the established numerical model. The dynamic development law of the mechanical response of the filling, geogrid and filling-geogrid interface, and their influences upon the embankment stability were also discussed. The findings regarding the reinforcement effect obtained from the numerical simulation were verified macroscopically using the geotechnical centrifuge model test results. The results showed that the embankment surface differential settlement was reduced by 47.1%, the maximum wall extraversion was reduced by 65.4%, and the embankment stability factor was increased by 12.8% with the geogrid reinforcement. With the increase in the shear reduction factor, the joint elements between the filling and the geogrid failed (slipped), but this slip was not responsible for the failure of the subgrade. Thus, the axial tension decreased suddenly owing to the failure of the geogrid in the upper layer, which was located outside the edge of the balancing platform. The tensile failure of the geogrid induced the instability and failure of widening embankment.
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图 2 有限元分析所获挡土墙墙面水平位移及路基面沉降分布
Figure 2. Retaining wall face horizontal displacement and embankment surface settlement distribution based on finite element analysis
图 4 离心模型试验所获路基面沉降分布
Figure 4. Embankment surface settlement distribution based on centrifuge model tests
图 5 强度折减系数SRF与路基最大总位移关系
Figure 5. Relationship of strength reduction factor SRF and the maximum total displacement of embankment
图 6 仅由强度折减产生的总位移矢量及云图
Figure 6. Vectors and contours of total displacement produced only by strength reduction
图 7 最大剪切应变分布云图及单元失效情况（1）
Figure 7. Maximum shear strain distribution and element failure（1）
图 8 最大剪切应变分布云图及单元失效情况（2）
Figure 8. Maximum shear strain distribution and element failure（2）
表 1 土体与挡土墙材料参数
Table 1. Soil and retaining wall material parameters
对象 弹性模量/MPa 泊松比 重度/（kN•m–3） 粘聚力（峰值、残余值）/kPa 内摩擦（峰值、残余值）/（°） 地基、旧路基 120 0.30 22 27、27 26.5、26.5 新路基 24 0.38 20 5、5 25.0、25.0 挡土墙 25 000 0.20 24 35、— 10.5、— 
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