复杂入渗边界下非饱和渗流过程的解析计算OA

To address the unsaturated seepage problem in surface soil layers under complex boundary conditions,linearized theoretical models for unsaturated seepage during two distinct infiltration stages,pre-ponding and post-ponding,are established using mathematical techniques such as dimensionless linearization and the principle of equation homogenization.Analytical expressions for hydraulic conduc-tivity,matric suction head,and volumetric water content during the corresponding unsaturated seepage processes are derived.Additionally,a method for calculating surface ponding time is pro-posed,and the reliability of this analytical approach is verified numerically.The results indicate that under periodic surface boundary conditions,both the volumetric water content and matric suction head at characteristic points exhibit periodic variations consistent with the surface boundary.Compared to surface conditions,characteristic points near the surface display a distinct phase lag.Furthermore,the peaks and troughs of the periodic evolution curves for volumetric water content and matric suction head increase over time.The period of the seepage rate evolution curve matches that of the surface bound-ary,but its amplitude is significantly reduced,indicating that the soil layer exerts an attenuation or"peak-clipping"effect on the periodic fluctuations of the seepage rate,an effect that becomes more pro-nounced with increasing depth.Under continuous infiltration conditions,prior to surface ponding,the upper portion of the soil layer is in an infiltration state,whereas the lower portion is in an evaporation state due to the influence of the groundwater table.Following surface ponding,the entire soil layer transitions to a state of sustained infiltration,ultimately approaching saturation.The evolution charac-teristics of volumetric water content and matric suction head within the soil layer under continuous infil-tration reflect the combined effects of the surface boundary and groundwater.This study offers signifi-cant theoretical and practical value for analyzing unsaturated seepage hydrological processes and for the prevention and mitigation of geological hazards.