受土洞坍塌影响的加筋路基渐进失稳演变特性与机理

As the economy develops significantly, many infrastructure projects including road engineering and railway constructions shall be carried out over voids caused by the active gypsum dissolution considering ever-increasing demands on land use in China.The collapse of sinkholes beneath or close to embankments which is a typical geologic disaster in karst area, always disrupts transportation route serviceability causing significant direct and indirect economic losses, also may lead to traffic accidents involving personal damages incluing injuries and deaths. Furthermore, nobody can calculate where the next subsidence occurrence will certainly arise. It is an economically practicable precaution to lay geogrids with different resistances to a variable number of road sections involving the road constructions in sinkhole-prone areas over long distances.The approach against karst collapse has been used considering the occurrence probability of sinkholes in different diameters in many areas.The use of geogrids alse can delay the deformation and collapse of embankments induced by sinkhole subsidence. Nevertheless, there is not a suitable theory for the design of geosynthetic-reinforced embankments over voids induced by karst. The goal of this proposed scientific research program is to investigate behaviour and the progressive failure mechanisms of geosynthetic- reinforced embankments spanning soil cavities. The coupling approach of finite element method and particle discrete element method will be used to simulate the interaction behaviours among geosynthetics-reinforced soil layers, embankments and sinkholes. Moreover,the failure modes of geosythetic-reinforced embankments due to subsidence problems will be studied by using rigid-plastic finite element method. The results from laboratory model experiments and from field investigation will be compared with those from numerical analysis. The effects of different factors, such as the soil layer parameters, the heights of embankments, the tension stiffness of geosynthetic materials, shinkhoe sizes,and so on, on subsidence-induced progressive failure and delayed deformations of geosynthetic-reinforced embankments are to be considered. Different mitigation measures that may be used to avoid or diminish sinkhole-related damages on transportation infrastructures will be detailedly interpreted. The design methodology, as well as a closed analytical solution, will be proposed for high-resistance geosynthetic-reinforced embankments as an effective measure against collapsed sinkholes on account of technical feasibilities and economic benefits.

因用地紧张和使国民经济持续增长需要,众多基础设施包括市政道路、公路和铁路需在浅埋岩溶土洞密布和发育的地基上修建。工程上可用加筋土的铺设来防止或延迟因受交通荷载和地下水等因素导致的土洞失稳坍塌而引发邻近道路的突发性破坏，起到破坏预警作用。针对受土洞坍塌影响的加筋路基渐进性破坏演变特性与设计理论研究落后于工程实践情况，通过物理模型试验、理论解析解、拉格朗日-欧拉大变形有限元与颗粒离散元耦合分析，研究土工加筋材料垫层、洞室、基础顶板和路基等相互作用机理和协调变形性状；研究洞室坍塌影响下加筋路基-路堤的荷载传递和加筋材料受力机理、土拱效应与应力重分布特性、剪切应变带扩展过程以及路基承载与破坏机制，揭示不同因素和工况对土洞坍塌时加筋路基渐进性破坏演变的影响特性和加筋材料所起作用的路基变形失稳延迟效应机理；提出抗土洞坍塌影响的加筋路基设计理论。项目的研究可为相关工程问题的解决提供合理的方法和理论依据。

随着我国基础建设的迅猛发展,在岩溶土洞发育地区修建的道路与铁路工程越来越多。岩溶土洞发育和引发的工后沉陷破坏难以预测，应用土工合成材料加筋可防止路基岩溶塌陷造成突然性的破坏，避免人员伤亡。当前岩溶土洞塌陷灾变影响下的加筋路堤渐进破坏机理和相应的设计方法研究滞后于工程实际需求。本项目以解析理论分析、数值模型试验分析为主要研究手段，辅以物理模型试验，揭示了加筋体和土工格栅加筋路基、岩溶土洞、上覆土层及路堤几部分协调变形与相互作用机制；揭示了岩溶土洞上方和邻近加筋路基-路堤荷载传递机理及其整体或局部破坏模式，剪切带的分布和发展规律；揭示不同影响因素和工况条件下受岩溶土洞塌陷灾变影响的加筋路基-路堤破坏演变和延迟失稳效应；考虑渐进破坏机理，提出了一系列完整的岩溶土洞塌陷灾变影响下加筋路基设计方法和经济有效的破坏控制措施和延迟失稳措施。对推动相关工程问题解决具有很好的理论意义和显著的经济与社会效益。