轻质固化泥路堤-微生物胶结垫层-刚性桩路基结构作用机理及设计理论研究

At present, the construction of high-speed transportation subgrade has the deficiencies of high financial cost, high difficulty of settlement control, and high demand for construction materials. Aiming at solving these deficiencies, this project proposes a novel subgrade structure consisting of light-weight embankment using solidified dredged sediments, bio-cemented geogrid-reinforced cushion, and rigid piles. Solidifying dredged sediments into light-weight embankment fill not only reduces embankment load but also disposes of the traditionally unwanted dredged sediments as well as saves construction materials. The recycled aggregate cushion treated by the technique of Microbially-Induced Carbonate Precipitation (MICP) will have the advantages of improving the load transfer modes of the subgrade and reducing the subgrade settlement and financial cost. By utilizing the methods of laboratory tests, field tests, microcosmic observations, numerical simulations and analytical analyses, this project will investigate the engineering properties of light-weight solidified dredged sediments and bio-cemented recycled aggregate, optimize the addition proportion and amount and establish its corresponding constitutive models; study the load transfer mechanism and the synergistic effect of all parts of this new subgrade structure; investigate the variation of stress field during service life and long-term cumulative deformation behavior of the proposed subgrade structure; establish design theory and methods for the proposed subgrade structure with and without bridge transition section to apply to the highway and high-speed railway in soft ground areas. The outcomes of this research project will provide theoretical foundation and technical support for the acceptance and increased usage of the proposed subgrade structure in engineering practice. Meanwhile, these outcomes will also have important significance for building an environmentally friendly and resource-saving and sustainable society.

针对我国软土地区高速交通路基造价高、沉降控制难、建材资源消耗大的不足，本项目提出一种“轻质固化泥路堤-微生物胶结垫层-刚性桩”新型路基结构。该路基结构将疏浚泥固化成轻质路堤填料，既减小路堤荷载又处置废弃泥、节约建材资源；同时，基于微生物固化技术处理再生骨料垫层，可显著优化路基荷载传递模式，减小路基沉降与工程造价。本项目拟结合室内试验、现场试验、微观测试、数值模拟和理论分析等手段，研究轻质固化疏浚泥及微生物固化垫层再生骨料的工程特性、优选配比及掺入剂量并构建本构模型；揭示该新型路基结构的荷载传递机理及路基体系各部分之间的协同作用关系，探究路基体系服役期的应力场变化规律及长期累积变形；针对一般路段和路桥过渡段路基体系，建立该新型路基应用于软土地区高速公路和高速铁路的设计理论与方法。项目研究成果可为该新型路基的推广应用提供理论和技术支撑，对我国建立环境友好、资源节约型可持续发展社会具有重要意义。

微生物固化技术是岩土工程领域的一种新型环保的地基处理技术，本项目针对该技术在软土地区高速公路和高速铁路路基中的应用开展相关研究。通过开展一系列室内试验、微观测试，研究了微生物固化钙质砂的峰值强度、脆性指数、应力应变体变特性等的影响，探讨了微生物固化钙质砂强度增长的内在机理；在此基础上，为改善MICP固化土的脆性破坏，将其与纤维加筋技术相结合，并研究了纤维加筋与MICP相互作用机理；此外，针对大规模现场应用时固化土体均匀性差的问题，尝试在固化土体中引入脲酶抑制剂减缓反应速率，通过多种脲酶抑制剂的比选确定应用最广泛的脲酶抑制剂，以对比试验验证该类脲酶抑制剂在MICP反应过程中的作用效果，探讨了脲酶抑制剂应用于MICP反应中的可行性；同时，基于前期开展的MICP加固的作用机理研究，考虑注浆（包括菌液和胶结液的注入）过程中细菌的运移和附着、尿素水解速率、碳酸钙沉淀、孔隙填充和渗透率降低等特征，建立了适用于现场尺度的反应－运移模型，并模拟分析了注菌和注胶速率以及注浆方式对固化效果的影响。该项目所开展的研究获得了系列创新成果，可为微生物固化技术在岩土工程中的应用提供理论指导。