Suffusion is a type of the internal erosion which involves in a selective erosion of the fine particles through the soil skeleton. To better understand the mechanism of the erosion in various soil types and evaluate the improvement of the fiber-reinforced soil under suffusion, a total number of 12 upward seepage tests on three grain size distributions (i.e., two uniform soils and one gap-graded soil) were conducted. The objectives of this study are to investigate the influence of fiber parameters, fiber content and length, on hydraulic behavior and failure modes in fiber-reinforced soil (FRS) and to establish a modified criterion to assess the internal stability of FRS. Experimental results indicates that the inclusion of the fiber can significantly decrease the permeability k and increase the Forchheimer coefficient β. Under the variation of the fiber content and length, the failure mode of suffusion, classified as internally unstable soil, changed to the failure mode of suffosion, classified as internally stable soil. With the increase in fiber content, the onset of the erosion in fines and the shift into transition flow zone were generally postponed, whereas the increase of the fiber length presented minor improvements. For suffusion, the critical hydraulic gradient of failure was increase majorly related with the fiber content; however, the which for the suffosion was increase with the fiber length. In addition, the results of modified criterion in unreinforced cases are in a good agreement with the experimental data in literatures and the which in reinforced cases owns a degree of conservatism.

Suffusion is a type of the internal erosion which involves in a selective erosion of the fine particles through the soil skeleton. To better understand the mechanism of the erosion in various soil types and evaluate the improvement of the fiber-reinforced soil under suffusion, a total number of 12 upward seepage tests on three grain size distributions (i.e., two uniform soils and one gap-graded soil) were conducted. The objectives of this study are to investigate the influence of fiber parameters, fiber content and length, on hydraulic behavior and failure modes in fiber-reinforced soil (FRS) and to establish a modified criterion to assess the internal stability of FRS. Experimental results indicates that the inclusion of the fiber can significantly decrease the permeability k and increase the Forchheimer coefficient β. Under the variation of the fiber content and length, the failure mode of suffusion, classified as internally unstable soil, changed to the failure mode of suffosion, classified as internally stable soil. With the increase in fiber content, the onset of the erosion in fines and the shift into transition flow zone were generally postponed, whereas the increase of the fiber length presented minor improvements. For suffusion, the critical hydraulic gradient of failure was increase majorly related with the fiber content; however, the which for the suffosion was increase with the fiber length. In addition, the results of modified criterion in unreinforced cases are in a good agreement with the experimental data in literatures and the which in reinforced cases owns a degree of conservatism.

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