“微生物固化加筋垫层-刚性桩”路基结构承载性能与变形控制特性

In view of the problem that the expensive pile-plate subgrade structure and the imperfect deformation control effect in the traditional geogrid-reinforced and pile-supported embankment, this project aims to develop an environmentally friendly subgrade structure consisting of Bio-cemented Fiber-Geogrid Reinforced cushion and Rigid Piles (termed as Bio-FGR-RP subgrade structure) to economically and efficiently control the deformation of subgrade. However, the load-transfer and deformation controlling characteristics of the Bio-FGR-RP subgrade structure are unclear due to the extremely complex multiple coupling effect involved in this new subgrade structure. A series of experimental tests in macro and micro perspectives will be conducted in this project to investigate the engineering mechanical properties of Bio-cemented Fiber Sand (Bio-FS), optimize the parameters regarding to fiber and microbial induced calcite precipitation and establish the material constitutive model of Bio-FS. Afterwards, the bending strength tests and numerical simulations will be carried out to reveal the performance evolution and the coordination working mechanisms of all the parts of Bio-cemented Fiber-Geogrid Reinforced (Bio-FGR) cushion. Finally, the laboratory model experiments and numerical simulations will also be conducted to deeply investigate the load transfer mechanism and deformation controlling characteristics of Bio-FGR-RP subgrade structure and refine the useful design theory of the Bio-FGR-RP subgrade structure. The research findings of this project will give new ways for subgrade treatment in soft soil area, and meanwhile, establish theoretical and experimental supports for the comprehensive popularization and application of this new subgrade structure in actual engineering.

针对桩板式路基结构价格昂贵和传统桩承式加筋路堤变形控制效果不佳等问题，本项目旨在研发一种环境友好的“微生物固化纤维-格栅加筋垫层-刚性桩”（Bio-FGR-RP）路基结构，达到经济高效地控制路基变形的目的。该新型路基结构涉及极为复杂的多元耦联作用，其承载性能和变形控制特性尚不明确。本项目将开展系列宏细观试验，明确微生物固化纤维加筋砂土（Bio-FS）的工程力学特性，优化纤维加筋及微生物固化参数，建立Bio-FS材料本构模型；然后基于抗弯强度试验及数值模拟，全面揭示微生物固化纤维-格栅加筋（Bio-FGR）垫层性能演化规律及各部分协同工作机制；最后通过室内模型试验及数值建模，深入探究Bio-FGR-RP路基结构的荷载传递机理与变形控制特性，凝练实用的Bio-FGR-RP路基设计理论。项目研究成果将为软土地区路基处理提供新途径，为Bio-FGR-RP路基结构的全面推广与应用奠定理论及试验基础。

微生物固化（Microbially Induced Carbonate Precipitation，以下简称MICP）技术是近年来岩土工程领域新兴起的一种高效、绿色、低成本的新型环保地基处理技术。该技术主要是利用产脲酶菌水解尿素，并在引入钙离子的条件下诱导产生具有胶结及填充作用的碳酸钙晶体，胶结松散的土体颗粒并填充颗粒间孔隙，达到改善土体工程力学特性的目的。本项目针对桩板式路基结构造价高、而传统桩承式加筋路堤变形控制效果不佳等问题，提出利用微生物固化技术将传统桩承式加筋路堤的褥垫层固化成“类岩土”，以形成类似于桩板式路基结构中的钢筋混凝土承载板，研发一种环境友好的“微生物固化加筋垫层-刚性桩”路基结构。本项目通过开展无侧限抗压强度试验、固结排水三轴试验、扫描电镜测试、室内模型试验及离散元数值模拟，对该新型路基结构所衍生的岩土材料性质及该结构的承载变形特性进行了研究，并主要得到以下结论：1）胶结液浓度对MICP过程存在抑制作用，该抑制作用主要源于溶液中的钙离子，且随胶结浓度的增大而逐渐显著，当胶结浓度高于2.5 M时MICP过程终止；2）格栅加筋能够有效提高微生物固化碎石的抗剪强度，并在一定程度上能够避免微生物固化碎石脆性破坏的发生；3）“微生物固化加筋垫层-刚性桩”路基结构能够显著提高路堤荷载传递效率、减小路堤变形及桩间土沉降，并一定程度上可避免路堤中“土拱结构”的劣化，提高路堤整体及“土拱结构”的稳定性。