既有的土体内部稳定性判定准则,对宽级配砂砾土非稳定渗流中的内部稳定状态难以准确刻画。从细粒迁移显微观测的试验设计中,通过测算试样流速与累计侵蚀率的突变特征,引入孔隙率n修正Istonima准则。研究结果表明:①细粒活跃状态随不均匀系数Cu及孔隙率n的增加而增加,根据其运动特征可划分为稳定、过渡和不稳定3个阶段。②流速发展为存在渗流突变点的随水力梯度先减后增的非线性过程,渗流突变点是渗流压密—渗流侵蚀的转化临界点;试验中各因素对质量侵蚀率敏感性大小为:水力梯度、级配不均匀度、孔隙率,在Cu=20.47、n=0.40时质量侵蚀率最大。③通过对比以试样内部细粒稳定程度及宏观参数特征所划分的内部稳定性判定结果与各判定准则结果,将相对准确的Istonima准则进行修正,提高了对宽级配砂砾土内部稳定性的判定准确性。
Abstract
The current internal stability criterion of existing soil fails to accurately describe the phenomenon of unsteady seepage in widely-graded gravel soil in both laboratory tests and engineering practice. This paper proposes a modified Istonima criterion by using porosity (n) based on the abrupt variations in sample flow velocity and cumulative erosion rate measured from experimental design of microscopic observation on fine particle movement. The results demonstrate the following: (1) The active state of fine particles increases with a higher uneven coefficient (Cu) and porosity (n), exhibiting three distinct stages of stability, transition, and instability based on their motion characteristics. (2) The flow velocity undergoes a nonlinear process as the hydraulic gradient decreases initially and then increases. The abrupt change point of seepage is identified as the critical point of seepage compaction and seepage erosion. The sensitivity of each factor to the cumulative erosion rate follows the descending order of hydraulic gradient, gradation unevenness, and porosity. The combination of Cu=20.47 and n=0.40 yields the highest cumulative erosion rate. (3) By comparing the result of internal stability obtained through the fine particles’ stability degree and the macroscopic parameter characteristics with those derived from various criteria, the Istonima criterion is found to offer relatively accurate results. In addition, modifications to the Istonima criterion are proposed to enhance the accuracy of determining the internal stability of widely-graded gravel soil.
关键词
宽级配砂砾土 /
圆柱入渗试验 /
细粒迁移 /
渗流突变点 /
内部稳定性
Key words
widely-graded gravel soil /
cylindrical infiltration test /
fine particle movement /
abrupt change point of seepage /
internal stability
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基金
国家自然科学基金项目(42272304);湖南省自然资源厅科技计划项目(202218)
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