强风化千枚岩填筑路基水-力耦合及长期变形特性研究

In the weathered phyllite region, the highway construction comes into two obstacles. One is the shortage of the land resources. The other is lack of the subgrade filling material. Sometimes the highly-weathered phyllite has to be chosen as the filling material. The strength of the weathered phyllite is very low. Once it is inundated in the water, it will become argillaceous and disintegrated. As a result, the non-uniform settlement of the subgrade will be induced. The project aims to study the moisture-stress coupling mechanism and the long term deformation characteristics of the phyllite filling subgrade. Three methods are carried out, which includes the indoor sample experiments, the large scale model experiments and the numerical calculation analysis. Based on the study of the mineral composition, compaction fragment and water disintegration, to analyze the mechanism and characteristics of the second disintegration of the highly-weathered phyllite. By introducing the fractal theory ,the triaxial test and CT scan analysis, it develops the function between the fractal dimensions and the empty volume ratio and the strength of the filling material. It develops the stress and moisture coupling model by thinking about the moisture migration mechanism and the creep characteristic of the phyllite. Through the large scale subgrade imitation experiments under the cyclic loading, combining the numerical simulation, it analyzes the timeliness of the subgrade deformation and forecast the long-term deformation of the subgrade. Then the measures to control the deformation will be put forward. This project is valued to release the shortage of filling material in the phyllite region, further protect the agriculture farmland from the discharged soil and protect the environment.

强风化千枚岩分布区域土地资源匮乏和路基填料难于选材的矛盾十分突出，不可避免地采用该类材料填筑路基。强风化千枚岩强度较低，遇水发生泥化、崩解，填筑路基易发生不均匀变形。拟采取室内试件试验、大型模型试验、数值计算与理论分析的方法，对千枚岩填筑路基水-力耦合和长期变形特性进行研究：从千枚岩的矿物构成、压实破碎、遇水崩解等方面，分析千枚岩填料的压实-破碎、崩解-泥化机理，揭示千枚岩填料的二次崩解特性；引入分形理论，基于三轴试验及CT扫描分析，构建分形维数与填料孔隙率及强度之间的函数关系；考虑千枚岩填料的水分迁移机理和蠕变特性，建立水-力耦合模型；进行循环加载下路基变形试验，结合数值模拟结果，分析强风化千枚岩填筑路基变形的时效性，预测路基的长期变形特性，提出控制强风化千枚岩路基变形的工程措施。该项目对解决强风化千枚岩地区路堤填料缺乏、弃土占用农田问题，保护环境有重大的社会意义。

强风化千枚岩填料强度低，遇水易发生泥化、崩解，在长期荷载的作用下填筑路基易发生不均匀变形。然而，在千枚岩分布区高填方路基填方选材困难，而深挖路堑、隧道弃方又要占用农田，不可避免地需要采用此类材料填筑路基。项目借助室内试验、数值模拟、现场试验以及实体工程验证的手段，系统研究了风化千枚岩作为路基填料时在水-荷载作用下的变形特性。主要成果如下：针对行车荷载、自然环境条件作用下千枚岩填料的二次破碎问题，提出了不同工况下千枚岩填料的崩解破碎试验方案，构建了填料粒径分布的Menger分形模型，结合破碎过程和能量转换原理揭示了千枚岩填料的崩解破碎机制，进一步建立了填料力学性能与级配分形维数之间的函数关系。借助研发的土体水分迁移装置，模拟了真实工况下水分的迁移过程，结合土水特征曲线确定了千枚岩填料的水分运动参数；进行了蠕变试验，应用指数衰减型蠕变曲线构建了不同含水率下填料的蠕变变形随着时间和应力水平的函数表达式，对千枚岩填料路基的水-力耦合特性进行了研究。研制了室内试槽路基湿化变形测试系统，结合室内及现场试验，测试分析了内、外部因素对千枚岩填料路基湿化变形的影响机理，基于现场湿化变形测试建立了路基变形的预测模型，考虑最不利因素预测了风化千枚岩填筑路基可能发生的塑性变形。结合现场试验路的修筑，从改善千枚岩填料力学性能角度，提出了千枚岩填筑路基结构组合的设计和施工方案；从防排水的角度，提出了路基防排水的原则和措施。针对大量弃方形成的弃渣场，建立了弃渣场边坡稳定性分析模型，提出了弃渣场边坡稳定性评估内容及流程。项目成果特色鲜明，理论和工程意义突出，可直接用于指导强风化千枚岩地区公路路基的修筑，也可指导岩性相似软岩地区公路路基的修筑。研究成果对解决软岩分布区路基填料缺乏、弃土占用农田问题乃至环境保护都具有重大意义。