散体与黏结型变刚度复合加筋垫层－桩－土－路堤共同作用机理研究

The technique of pile-supported geogrid-reinforced granular cushion is currently used in embankment of highway and railway engineering.The new type of cementitious reinforced cushion is proposed.By field full-scale tests, laboratory model tests,DEM simulation and theoretical analysis, the cooperative work performance of granular geogrid-reinforced cushion or cementitious geogrid-reinforced cushion,pile, subsoil and embankment are studied. In field test,the effects of reducing settlement of the new triaxial geogrid with and without constrain are compared. In laboratory tests, by changing the rigidity of cementitious cushion, the influences of cementitious cushion on sharing embankment load by pile and soil and embankment settlement are investigated.Combined with field and laboratory tests results, DEM-FDM coulping method is applied to study the cooperative work performance of granular geogrid-reinforced cushion or cementitious geogrid-reinforced cushion,pile, subsoil and embankment.It is also theoretically analyzed and the settlement calculation method of this kind of embankment is proposed. The achievements in this research can perfect the design methodology of pile-supported and geogrid-reinforced embankment and applied in China's constrution of expressway and railway, they are of great significance in academic research and engineering practice.

针对桩承式加筋散体垫层法在高速公路和铁路工程中的应用，提出采用黏结体加筋复合垫层的新的结构型式。对桩承式格栅加筋散体复合垫层法和桩承式格栅加筋黏结体复合垫层法的作用机理进行现场足尺试验、室内模型试验以及离散元数值模拟和理论分析方法进行研究。现场试验中对新型格栅在有约束和无约束情况下散体复合垫层减少沉降的效果进行对比分析。室内模型试验中通过改变黏结体复合垫层的刚度，研究不同刚度半刚性黏结体复合垫层对桩、土分担路堤荷载的影响以及对路堤沉降的影响规律。结合现场和室内试验研究结果，采用离散元－有限差分耦合方法对其进行数值模拟，探讨散体与黏结体加筋复合垫层－桩－桩间土－路堤的共同作用机理。通过理论分析，探讨桩承式加筋散体复合垫层和黏结体复合垫层体系的各部分相互作用以及路堤的沉降计算方法。研究成果可完善桩承式加筋垫层法设计计算理论，指导其在我国目前工程建设中的应用，具有重要的学术价值和工程实际意义。

桩承式加筋路堤能够有效提高不良地基的承载力、减小地基沉降和不均匀沉降，在公路和铁路工程中得到广泛应用。然而，对于桩承式加筋路堤的荷载传递机理及其影响因素，包括筋土界面特性、土拱效应和张拉膜效应的研究还远落后于工程实践。通过开展土工格栅的室内直剪试验、拉拔试验和离散元数值模拟，探讨了土工格栅加筋土的拉拔力-拉拔位移关系、筋土界面剪切特性、强度参数、表观摩擦系数和破坏模式等，获得了筋土界面特性的系列创新成果，可为实际工程中加筋处治提供优化的设计方案。通过现场足尺试验，对桩承式加筋路堤的桩间土沉降、格栅上下表面土压力和格栅变形等进行了长期监测，获得了桩承式加筋路堤长期工作特性的系列创新成果。通过采用离散元数值模拟方法，基于路堤中应力偏转规律对土拱随桩土相对位移的形成规律进行了分析。针对桩承式加筋路堤应用于实际工程中存在的不足，包括路堤沉降、不均匀沉降和侧向位移过大，整体或局部路堤失稳以及筋材效率低等，研发出了一种新型地基处理技术——桩承式加筋路堤挂网技术。研究结果表明桩承式加筋路堤挂网技术可有效减小路堤沉降、差异沉降和侧向位移，提高桩体荷载传递效率。基于桩承式加筋路堤中桩基正常使用极限状态可靠度研究相对落后这一现状，针对桩基正常使用极限状态可靠度分析与设计的相关问题，开展了较为系统的研究工作。