循环荷载作用下吸水土工布路基湿度及强度控制效果研究

道路结构的长期服役性能与路基湿化状态密切相关。本文针对循环荷载作用下的细粒土路基湿度控制及强度提升效果,选取我国黄河中下游流域典型路基填料,构建了级配碎石底基层-吸水土工布-粉质黏土路基物理模型,开展了不同循环荷载下路基填料的水分迁移试验研究,探究了最优含水率阶段、饱和阶段和排水稳定阶段下粉质黏土路基湿度、应力、变形以及回弹模量的演化规律。结果表明:循环荷载作用下吸水土工布使土层的基质吸力提高8.3~12 kPa,土工布附近土体水分受重力势和基质势共同驱动向吸水土工布内部迁移并通过微米级孔隙通道向外部进一步导排,排水稳定后土层含水率降低1.39%~3.81%,同时各应力幅值下粉质黏土路基层永久变形均显著降低约55%。在吸水土工布的水力和机械双重加固作用下,粉质黏土路基层动态回弹模量较饱和状态显著提升,各应力幅值下动态回弹模量分别为饱和状态的5.48倍、3.54倍、2.69倍、1.36倍。The long-term performance of road structures is closely related to the moisture conditions of the subgrade. This paper focuses on the effects of moisture control and strength improvement of fine-grained soil subgrade under cyclic loading. A physical model was constructed using typical subgrade fill materials from the middle and lower reaches of the Yellow River in China, which includes a graded gravel base layer, a wicking geotextile, and a silty clay subgrade. Experiments were conducted to study the moisture migration of the subgrade fill materials under different cyclic loads, exploring the evolution of moisture, stress, deformation, and rebound modulus of the silty clay subgrade during the optimal moisture content phase, saturation phase, and drainage stabilization phase. The results show that under cyclic loading, the wicking geotextile increases the matrix suction of the soil layer by 8.3~12 kPa. The moisture in the soil near the geotextile is driven by both gravitational potential and matrix suction toward the interior of the geotextile and is further drained through micron-sized pores. After drainage stabilization, the moisture content of the soil layer decreases by 1.39%~3.81%, and the permanent deformation of the silty clay subgrade under various stress amplitudes is significantly reduced by approximately 55%. Under the dual reinforcement effect of hydraulic and mechanical properties of the wicking geotextile, the dynamic rebound modulus of the silty clay subgrade is significantly improved compared to the saturated state, with dynamic rebound moduli being 5.48 times, 3.54 times, 2.69 times, and 1.36 times that of the saturated state under different stress amplitudes.

吸水土工布对路基湿度控制效果的数值模拟

针对我国典型的粉质黏土填料路基,提出采用新型吸水土工布来控制细粒土路基内部湿度,通过对比铺设吸水土工布前后路基内部体积含水率和基质吸力的空间分布,评价吸水土工布对路基湿度的控制效果。基于压力板仪等室内试验获得吸水土工布水力参数,通过COMSOL有限元软件建立路基水汽迁移分析模型,获得不同水位条件下(2、4、6、8 m)路基内部体积含水率和基质吸力的空间分布特征,分析路基内部水分迁移模式和吸水土工布的吸排水机理。结果表明:新型吸水土工布具有较强的亲水性、较低的持水性和较高的水平渗透性;吸水土工布对路基湿度具有较好的控制效果,土工布界面上下的含水率和基质吸力发生明显突变;相比于无土工布路基,4~8 m处地下水位吸水土工布上方土体体积含水率显著降低7.6%~9.6%,基质吸力增加2~2.3倍,路基动态回弹模量提高23.2%~43.6%;吸水土工布凭借形成的基质吸力差和自身的水平导水能力,可快速吸排出非饱和土中的弱结合水。水土工布可有效控制毛细水上升导致的路基湿化,并能提高路基的支撑能力。