The phenomenon of suffusion, commonly observed in gap-graded soils, involves the detachment and transport of the finest grains under internal fluid flow. This can lead to the significant loss of fines, potentially causing mechanical instabilities in the material and posing a risk of catastrophic failure in hydraulic structures, including static liquefaction. To mitigate this risk, a novel approach is being explored – reintroducing fines into the granular skeleton, predominantly composed of coarse sand grains. This technique is inspired by recent numerical studies suggesting that the inclusion of weakly loaded grains can significantly enhance the mechanical stability of granular materials. This work aims to investigate the infiltration of fine injection and then evaluate its mechanical remediation effectiveness on the suffused sample using both numerical and experimental methods. Utilizing coupled discrete element method (DEM) and Pore-scale Finite Volume (PFV), the process of spherical fine infiltration into a coarse sand column is analyzed under gravity and hydraulic forces. A probabilistic model based on pore-constriction size is proposed to interpret the decaying characteristics of the infiltration from both numerical and experimental observations. Complementary, the mechanical properties of pre- and post-injection soils are analyzed via drained and undrained tri-axial tests by DEM and laboratory experiment. The role of injected fines on the macroscopic material properties, like contractive behaviors and critical states, will be evaluated by comparison between the numerical and experimental results. Furthermore, the instability of the soil sample could be quantified using the second-order work criterion. The findings of this work reveal the non-homogeneous clogged fine content in the samples that depends on the microscopic structures. Also, the role of clogged fine is expected to prohibit the development of plastic strain of the coarse skeleton, thus enhancing the stability of suffused soil.

DEM,Suffusion,Soil remediation