抗土洞塌陷的低填方加筋路基荷载传递机制及设计方法
Load transfer mechanisms and design method of low geosynthetic-reinforced embankments subjected to localized sinkholes
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摘要: 低填方加筋路基对地基承载力要求较低,同时利用水平加筋法跨越尺寸较小的土洞能有效预防路堤出现突发式局部沉陷,提高路堤抗工后沉降和失稳的安全系数,正被逐步应用于岩溶土洞地区道路工程;但其作用机理复杂,现存设计方法大都偏于保守,考虑抗土洞塌陷的低填方加筋路基荷载传递机制的设计方法亟待提出。通过揭示受土洞塌陷影响的低填方加筋路基荷载传递机制,推导了考虑路基差异沉降引起土体应力偏转的竖向应力计算方法,假定塌陷区上方加筋体作用抛物线荷载,从而明晰了加筋体应力-应变状态;应对岩溶区不同形态的土洞塌陷,同时考虑设计需要满足的正常使用极限状态与承载能力极限状态,提出了抗土洞塌陷的低填方加筋路基加筋体及路堤填方高度设计方法,通过与现有设计方法的对比进行了合理性及准确性验证,可为空洞上方低填方加筋路基设计提供参考。Abstract: Low geosynthetic-reinforced embankments have a higher bearing capacity. In addition, the horizontal geosynthetics can prevent embankment from collapsing suddenly, which plays a warning role. The design of geosynthetic-reinforced platforms based on the load transfer mechanisms of low embankment in karstic regions should be proposed, for which the existing design methods are not recommended because of the complex mechanisms. By analyzing the stress-strain relations of the platform, the design considering the principal stress rotation due to differential settlements is improved and optimized under the assumption that there is a parabolic overload distribution perpendicular to the sheet overlying the void. The design method for the tensile stiffness of geosynthetic-reinforced sheet and the embankment height based on the load transfer mechanisms of low reinforced embankment spanning the sinkholes is proposed, containing different forms of surface subsidence and can be applied to the serviceability limit state design and the ultimate limit state design simultaneously. The accuracy and rationality of the proposed method are verified by comparisons of the current design methods so as to provide a reference for such structures.