Dynamic Numerical Analysis of Seismic Liquefaction and Deformation Failure in Silty Fine Sand of the Main Canal of Xixiayuan Irrigation District

Sand liquefaction has long been one of the key topics in the fields of soil dynamics and geotechnical earthquake engineering. Based on the Zhulong river section project of the main canal in Xixiayuan irrigation district, dynamic parameters of soil and rock masses were obtained through field and laboratory tests. Using geotechnical numerical analysis with FLAC 3D software, the constitutive model of sand was selected as the Finn model, and appropriate horizontal natural seismic waves corresponding to engineering site conditions and seismic fortification intensity were input to conduct dynamic numerical analysis on earthquake liquefaction of silty fine sand in canal foundation and characteristics of canal deformation and failure. The results indicate that under seismic action, the maximum excess pore water pressure occurs in the silty fine sand layer at the bottom of the canal embankment. However, due to the high initial stress in this layer, the pore pressure ratio remains low, preventing liquefaction. In contrast, in the channel bottom and the localised areas from the outer slope platform to the toe of the canal embankment, although the excess pore water pressure is relatively low, the effective stress is small, resulting in a higher pore pressure ratio, leading to liquefaction of the silty fine sand layers. Seismic‐induced deformation primarily occurs in the embankment and shallow foundation soils and exhibits a symmetric pattern. The deformation and failure of the embankment slope are mainly characterised by seismic subsidence and tensile failure at the crest, as well as horizontal lateral flow deformation at the slope toe. During the calculation process, monitoring points were installed at various locations in the canal embankment and foundation, capturing the dynamic changes in excess pore water pressure, effective stress and displacement at different positions under seismic loading. Based on the analysis of shear strain increment, a continuous shear sliding surface was found to develop within the embankment and foundation under seismic forces, suggesting a risk of overall sliding failure. The research findings are significant for understanding and addressing sand liquefaction characteristics in the Xixiayuan irrigation district’s main canal project.