应力与干湿循环耦合作用下易崩解软岩填料工程特性弱化规律及变形分析方法

Some soft rocks such as argillaceous shale easily tend to slake under mechanical loadings and wetting-drying cycles. With such soft rock fill materials, problems of excessive settlements of the highway subgrade arise after construction with time due to slake of the rock-fill materials. During this process, the initial dual-pore micro-structure of the compacted coarse-grained fill materials progressively evolves into a final uni-modal pore micro-structure. This would result in deterioration in the engineering properties such as hydraulic behavior and compressibility, and thus excessive settlements of the highway subgrade. In this study, the technique for measuring the unsaturated permeability coefficients of the soil is first developed based on GDS system. Experimental tests are performed to investigate the effect of disintegration and softening of the rock-fill materials on the soil-water character curves, unsaturated permeability coefficients and compressibility under both mechanical loadings and wetting-drying cycles. The mathematical expressions to describe the evolution of the soil-water character curves and unsaturated permeability coefficients are then proposed. One dimension compression model considering the strain increment induced by the increments of both mechanical loadings and wetting-drying cycles is also developed. The model is verified by the experimental results and it is further used to study the long-term compression behavior of the highway subgrade. The effect of each model parameter on the model performance is finally discussed and determined. Research of this project will provide technical support for the design of the new highway subgrade with the soft rock-fill materials easily tending to slake.

易崩解软岩作为路基等构筑物填料往往会产生较大沉降等病害。压实填料中粗颗粒在应力和干湿循环耦合作用下易发生崩解，微观孔隙结构由双孔隙群结构向单孔隙群结构发展，导致填料水力学特性和压缩性等工程特性弱化，路基沉降持续发展。针对应力与干湿循环耦合作用下易崩解软岩填料水力学特性及压缩性变化规律，提出基于非饱和土三轴试验系统的非饱和渗透系数测试方法，试验研究不同应力水平、不同干湿循环次数下土水特征曲线、非饱和渗透系数以及压缩性的变化规律。在此基础上，提出考虑填料崩解的水土特征曲线、非饱和渗透系数表达式以及一维固结压缩模型。通过室内试验验证模型的合理性，研究软岩填料路基长期变形发展规律，提出变形分析方法。本项目研究将为易崩解软岩类填料路基设计施工提供技术支撑。

本项目以易崩解软岩路基填料为研究对象，针对其在荷载和水作用下会产生持续较大沉降变形的病害问题，展开相关研究。在试验方面，开展了易崩解软岩填料路基SEM，MIP和DLS等微观结构试验，揭示了易崩解软岩填料微观结构特征，研究了在荷载和干湿循环耦合作用下路基土的压缩特性；同时开展了不同压实度、粉粒含量、最大粒径以及干湿循环对路基土持水特性的影响，获得了易崩解软岩填料双进气值土水特征曲线特性随压实度和粉粒含量变化的规律，并从微观孔隙结构角度揭示了变化机理。在理论上，提出了考虑土体压实度的双进气值土水特征曲线模型，并运用试验结果对模型的合理性进行了验证。