冻融循环对砼护坡界面抗剪强度影响试验研究

以混凝土铰接块+土工布+黏土护坡结构室内模型为研究对象, 分别讨论不同含水量及冻融循环次数下接触面间抗剪强度指标的变化规律. 分别测定常温下护坡结构含水量在15.7%~28%之间的黏聚力(C)和内摩擦角(φ)值, 含水量为18%以及饱和状态下经过10次冻融循环的C值和φ值, 采用多元回归法进行分析. 结果表明: 含水量对护坡结构的抗剪强度指标弱化十分明显, 斜面摩擦试验中黏聚力和内摩擦角均随含水量增加而降低; 含水量与内摩擦角呈线性相关关系, 与黏聚力呈乘幂关系. 冻融循环过程水分迁移导致砼护坡界面水分增大, 界面抗剪强度指标弱化. 随冻融循环次数的增加砼铰接块护坡界面的抗剪强度减小, 对于非饱和黏性土, 在5次冻融循环时减小幅度较大, 但10次冻融循环时减小幅度较小并基本趋于稳定; 而对于饱和黏性土, 其抗剪强度指标随冻融循环次数的增加减小幅度并不明显.

Experimental Study of the Influence of Freeze and Thaw Cycle on Shear Strength of Concrete Slope Protection

The indoor model of hinged concrete block, geotextile and clay slope structure was taken to study the interfacial shear strength with different soil moisture and different freeze-thaw cycles. The cohesion and internal friction angle values were measured with soil moisture between 15.7% and 28% at room temperature, and after 10 freeze and thaw cycles with soil moisture at 18% as well as with saturated water content. Finally, their relationships are obtained through multiple regression analysis. It is found that: 1) soil moisture has apparent effect on shear strength of slope protection structure, and the cohesion and internal friction angle decreases with soil moisture in the inclined plane friction test. There is a linear relation between the soil moisture and the internal friction angle. However, a power relation is found between the moisture content and the cohesion. 2) In the freeze and thaw process, soil water migration leads to an increase of interfacial water in concrete slope protection, with a decrease of interfacial shear strength. The shear strength of the concrete block revetment interface reduces with the number of freeze-thaw cycles. With regard to the unsaturated clay, the decreasing extent is relatively large at the fifth freeze-thaw cycle, while after 10 freeze-thaw cycles it is small and verges to a stationary state. However, for the saturated clay, the decreasing extent of the shear strength is not obvious with increase of the cycles.