Dynamic numerical analysis of liquefiable silty fine sand reinforced by gravel pile

Silty fine sand is prone to liquefaction under the action of earthquake. The research on the reinforcement method of silty fine sand foundation is the key to earthquake prevention and disaster reduction. This paper takes the Zhulong river section of the main canal of Xixiayuan irrigation area as the research object, and the cross section model of the canal is established by FLAC 3D software. Considering the dynamic hydraulic coupling effect of soil, the mechanism and effect of anti-liquefaction reinforcement of gravel pile are explored. Research findings demonstrate that stone columns exert a significant influence on the displacement of the main water conveyance canal and its foundation. Under seismic loading, the unreinforced model exhibited pronounced plastic horizontal displacement and upward heave displacement at the toe of the canal embankment. In contrast, the reinforced model showed a marked reduction in plastic horizontal displacement and the complete elimination of upward heave. Significant pore pressure increases occurred at the base of the canal embankment and at the embankment toe in the unreinforced model, triggering initial liquefaction at the embankment toe. The liquefied zone rapidly expanded to within 3 m below the ground surface, exhibiting clear liquefaction phenomena. The installation of stone columns created effective drainage pathways, facilitating the downward drainage of pore water from the liquefiable silty fine sand layer. This resulted in substantially reduced pore pressures at the embankment base and toe, accompanied by a decrease in the pore pressure ratio. Only localized liquefaction zones were observed at the embankment toe and between the stone columns near the sand surface. These findings indicate that stone columns effectively mitigate the seismic-induced buildup of pore water pressure, thereby enhancing the liquefaction resistance of the engineering structure. The research findings hold significance for silt liquefaction prevention and control in the main canal project of the Xixiayuan Irrigation Area.