Ili loess is susceptible to substantial collapsible deformation due to water infiltration

leading to various engineering failures. To investigate the characteristics of water infiltration and the mechanisms of collapsible deformation

a field immersion test was conducted in the collapsible loess region of Ili. The changes in water content

water diffusion form

infiltration water volume

and surface collapsible deformation during immersion were analyzed. Numerical simulations explored surface collapsible deformation characteristics under varying saturation infiltration ranges. The results showed that the average vertical diffusion rate in the experimental area was 0.38 m/d

while the average radial diffusion rate was 0.17 m/d. Over time

the water diffusion pattern transitioned from elliptical to conical

with a wet front angle of 41° and a saturated front angle of 20°. The quantitative analysis of the vertical and radial water diffusion rates and infiltration water volume of Ili loess over time was conducted. A mathematical relationship between infiltration range and cumulative infiltration volume per unit area was derived. The correction coefficient for collapsible in the experimental area was determined to be 0.74

exceeding the recommended value of 0.5 in the specifications. The surface collapsible deformation correlates with water infiltration and can be divided into four stages: stable immersion

severe collapse

slow collapse

and consolidation settlement. As the saturation front angle increases

the surface collapsible deformation value maintains good consistency with the calculation results of the subsidence trough formula. The variation in the width of the subsidence trough aligns with the influence range of surface collapsibility

both following an exponential increase.