干湿循环条件下裂缝对土体吸力影响的机制研究

Study on the Effect of Cracks on Soil Suction under Dry-wet Cycle Conditions

受干旱影响,土体会出现干缩裂缝,基质吸力的变化是分析裂缝开展的关键点,而裂缝的产生影响着基质吸力的变化,因此基于室内模型研究了干湿循环条件下不同位置土体开裂情况及对应部位基质吸力的时空演化规律。结果表明,斜坡中部裂缝更易发育,受旱过程中当裂缝存在时顶部土体的基质吸力增长滞后于坝坡中部土体的基质吸力增长;降雨后再干燥时段除底部外土体各处基质吸力受裂隙影响在较短时间快速增大,多次干湿循环后土体裂缝发展形态基本保持不变,此时同一部位基质吸力变化趋势基本相同,而不同部位因裂缝开展差异吸力变化有所不同。根据吸力变化情况绘制出的土水特征曲线反映出不同形态的裂缝存在对周边土体的影响(渗透系数)。研究成果可为维护坝坡稳定提供指导。

Under the influence of drought,shrinkage cracks will appear in the soil.The change of matrix suction is the key point to analyze the development of cracks,and the generation of cracks affects the change of matrix suction.Therefore,the indoor soil model is used to study the spatio-temporal evolution of cracks and matrix suction at different locations of the soil under dry-wet cycling.The results show that the cracks in the middle of the soil slope are more likely to develop,and the suction changes obviously with time.In the dry period,the matrix suction in the upper part of the soil lags behind that in the middle part of the soil in the presence of cracks.During the period of drying after rainfall,the matrix suction at all parts of the soil except at the bottom of the soil increases rapidly under the influence of cracks in a short time.After several dry-wet cycles,the development pattern of cracks remains are basically unchanged.At this time,the change trend of matrix suction in the same part is basically the same,but the change of matrix suction in different parts is different because of the difference of crack development.The soil-water characteristic curves is drawn according to suction variation,which reflects the influence of cracks on surrounding soils(permeability coefficient).The research study can provide guidance for maintenance of dam slope stability.