炭质泥岩崩解机理及路基长期变形预测方法研究

The carbonaceous mudstone is the most commonly occurring sedimentary rock in South-West China, especially in Guangxi province. As one of the soft mudstones, the carbonaceous mudstone has relative low mechanical resistance and bad durability due to its easy slack properties. As consequence, the carbonaceous mudstone has been considered as the undesirable filling material in the embankment construction. However, from the point of view of both economic efficiency and environment protection, the use of carbonaceous mudstone as filling material is unavoidable in South-West China. With the infiltration of pore water and the confining pressure, the aggregate of carbonaceous mudstone will continuous to slack. This will result into great deformation and settlement in the embankment and even will induce the instability problem of the embankment. In the current proposed project, the slack mechanism of the carbonaceous mudstone should be investigated through a series laboratory experiments, in situ measurements and long-term monitoring. And the main slacking factors, such as the pore pressure, the confining pressure, the initial aggregate distribution, will be characterized and compared by the mechanical analysis. By using the fracture mechanics and in the framework of unsaturated porous medium, an effective stress based criteria will be proposed for the slack process in carbonaceous mudstone. With the application of multiscale homogenization method, based on the microscope analysis, a macroscopic constitutive model will be proposed for the compacted carbonaceous mudstone, which will taking the slack process into consideration and can be applied in the unsaturated porous medium framework. In addition of the interaction between the aggregate redistribution and hydraulic properties, the variation of the porosity and hydraulic conductivities will be formulated by taking the slacking process into consideration. In the framework of Coussy, a numerical model will be programed via the finite element method. The numerical model will then be used to relate the engineering control parameters and the embankment long-term deformation. As results, a kit of practical parameters will be proposed for the design, construction and maintain of the embankment.

在炭质泥岩广泛分布地区，将这种强度低、易崩解的软岩用于路堤填筑势在必行。但在应力和孔隙水的作用下，炭质泥岩填料压实颗粒的持续崩解及强度劣化，将导致路基变形超限，甚至引发路堤失稳，危害行车安全。本项目首先通过系统的室内试验和现场监测资料分析，深入揭示炭质泥岩吸湿崩解机理及其主要影响因素，重点分析孔隙水、应力对崩解的影响；其次针对炭质泥岩填筑路基中水分迁移特征及颗粒崩解机理，提出炭质泥岩崩解的有效应力判别准则，建立炭质泥岩吸湿崩解的宏细观力学模型；在明确炭质泥岩吸湿崩解过程中孔隙率及渗透系数变化的基础上，采用非饱和孔隙介质理论及有限元方法建立可以充分考虑路基水分迁移及炭质泥岩颗粒崩解的路基长期变形预测方法；综合试验和数值仿真手段，分析现有路基工程指标对炭质泥岩路基长期变形的影响，提出适合炭质泥岩路基填筑简便适用的工程指标，对炭质泥岩分布地区的公路设计、建设、维护提出有效合理建议。

炭质泥岩在我国西南地区广泛分布，为降低工程造价、避免因换填导致的次生灾害及环境污染等问题，炭质泥岩作为路堤填料已在西南地区公路建设中广泛应用。然而，由于含大量亲水性强的高岭石等粘土矿物，炭质泥岩具有遇水易崩解、强度低、变形大等特点，如何保证荷载与干湿循环作用下炭质泥岩路堤施工、运营安全已成我国西南地区交通建设者最关心的问题之一，因此，本项目针对荷载与干湿循环作用下炭质泥岩崩解特性及路堤湿化变形从一下几个方面开展系统研究。.(1)开展了不同荷载与干湿循环作用下炭质泥岩的崩解特征试验，分析了炭质泥岩崩解过程中的宏观、微观形态、颗粒级配特征及崩解参数的变化规律，最后于溶解、膨胀及能量学角度探究了干湿循环及荷载作用下炭质泥岩崩解机理；.(2)针对炭质泥岩是否可用于路堤填筑的关键问题，明确了高速公路对炭质泥岩路堤填料的基本要求，论证了炭质泥岩用于路堤填筑的可行性，并探讨了炭质泥岩路堤填料的应用标准；.(3)采用正交分析方法研究了压实度、含水率、竖向荷载、浸水时间及循环次数等因素对预崩解炭质泥岩变形的影响，研究了湿化变形后的预崩解炭质泥岩抗剪强度特性变化规律；.(4)通过对不同干湿循环次数后的预崩解炭质泥岩试样开展三轴剪切试验，建立了基于双曲线函数的湿化变形弹性模型，并分析了不同干湿循环条件下预崩解炭质泥岩的微观孔隙特征，最终构建了考虑干湿循环损伤的预崩解炭质泥岩湿化变形模型；.(5)基于可考虑干湿循环损伤作用的预崩解炭质泥岩湿化变形模型，提出了炭质泥岩路堤湿化变形计算方法，进而利用自定义本构模型研究了炭质泥岩路堤的湿化变形规律。.本项目的研究成果可以为复杂条件下炭质泥岩路堤的设计、施工及运营过程中的变形控制提供试验及理论依据，研究成果具有重要的学术价值和工程应用前景。