防岩溶塌陷加筋垫层大比例模型试验及设计理论研究

Large-scale experimental study of multi-layered reinforcement to prevent underneath sinkhole in karst terrain and the design method

采用多层加筋垫层防治路基下部岩溶塌陷可降低工程造价、确保运营安全,其承载机制和设计方法仍有待深入研究。设计1∶5的大比例室内模型试验,通过实测塌陷过程中单层、三层及四层土工格栅加筋垫层应力–应变及变形量,分析路基中各层加筋体的变形特征,土拱效应与各层荷载分担比例,以及路基顶面沉降和底层加筋体挠度间的相关关系,结合测试成果,探讨多层加筋垫层设计中的关键问题及相关计算理论,试验结果与数据分析表明：采用多层加筋时,路基土拱拱脚将上移至顶层加筋体附近,出现＂双层土拱效应＂现象;多层加筋垫层中顶层加筋体所分担的荷载最大,而底层加筋体所承担的荷载较小,各层格栅荷载分布不均匀;路基顶面沉降变形与底层挠度间关系可采用不计入剪胀特性的方法简化计算;底层加筋体挠度控制路基表面的沉降发展,而顶层加筋体由于荷载分担比例较大,对承载力起控制作用。在试验成果基础上提出多层加筋垫层的设计流程,并进行工程实例分析,可供实际工程参考。

To prevent the underneath collapse induced hazard in road transportation,the multi-layer geotextile reinforcement is a cost-effective and promising technology,although its bearing mechanism and design method remain to be further studied. The embankment models of 1∶5 in scaling,with the single-layer,three-layer and four-layer geotextile reinforcements installed respectively,were designed and tested in laboratory. In order to study the load distribution and displacement characteristics,the vertical pressure on each geotextile and the relevant displacement were measured with the load cells and deformeters installed in the model. The key issues in design and the relevant calculation theory were discussed based on the measured data. The test results revealed that,in multi-layered geotextile reinforcement,the foot of soil arch might rise to around the top-layer reinforcement,and the dual-soil-arch emerged. The upper load distributed non-uniformly among the reinforcements. The surface depression could be related to the bottom deflection with a simplified method ignoring the dilation effect. The bottom-layer reinforcement is the key to control the surface depression while the top-layer is of the most importance to control the limit state. Based on the measured data and further analysis,a flow chart of design was proposed for practical engineering application.