土石坝护坡冻胀破坏水-热-力耦合数值模拟研究

Numerical simulation of coupled water-heat-stress processes related to frost damage of earth rock dam protective structures

针对寒区土石坝护坡普遍存在的冻胀破坏问题,选取寒区某土石坝工程为研究对象,结合土石坝工程特点,建立考虑水-热-力耦合作用的有限元计算模型。研究护坡在库水位和坝体填土水分迁移作用下冻胀破坏全过程,分析土石坝温度场、水分场和位移场的变化规律,并将位移场有限元计算结果与实测冻胀变形资料进行对比,验证有限元计算结果。研究结果表明:冻胀作用对坝坡影响深度约为2 m,坝坡浅层0~2 m范围的温度变化受外界气温影响较大,坝体内部温度相对坝坡浅层变幅小,且有一定的滞后性;负温使坝坡浅层孔隙水相变成冰,宏观上表现为未冻水体积分数的降低,坝坡浅层土石混合体孔隙水相变、坝体填土内水分向坝坡迁移和冻结峰面向坝体内部移动是护坡冻胀破坏的主要因素;大坝坝坡计算冻胀量为20~30 cm,最大值为36 cm,计算结果与实测冻胀变形资料吻合;护坡冻胀破坏主要由砂砾料垫层、坝体填土等土石混合体冻胀及冰推力共同作用引起。研究结果可为寒区土石坝护坡设计提供参考。

This study focuses on the common problem of frost heave damage to slope protection structures of earth-rock dams in cold regions.An earth-rock dam project located in a cold climate zone is selected as the research subject.A finite element model is developed considering coupled water,heat,and stress processes based on the project characteristics.The full process of slope protection frost heave damage under the influence of reservoir water level variations and soil water migration within the dam is examined.The temperature field,moisture field,and displacement field variations in the earth-rock dam are analyzed.Finite element calculation displacement field results are compared to measured frost heave deformation data,verifying the calculation results.The findings show the frost heave impact range on the dam slope is approximately 2 meters.The dam slope temperature distribution depends mainly on freezing depth.The shallow dam slope temperature from 0 to 2 meters varies greatly with external air temperature.The internal temperature within the dam body exhibits smaller variation amplitude than the shallow slope,with some lag.Negative temperatures cause the shallow pore water phase in the dam slope to transform to ice,shown as decreasing unfrozen water content.Soil-rock mixture pore water phase change,fill water migration to the slope,and frozen peak movement towards the dam body are key factors in slope protection frost heave damage.Calculated dam slope frost heave volume is 20-30 cm,maximum 36 cm,consistent with measured deformation.Frost heave damage primarily results from combined effects of frost heave and ice thrust in soil-rock mixtures like sand and gravel cushion and dam fill.The research provides a basis for earth-rock dam slope protection design in cold regions.