A calculation model for the loess collapse coefficient considering progressive wetting dry density and applied vertical pressure

Predicting wetting-induced collapse of loess requires accounting for the coupled effects of applied pressure, moisture state, and pore structure. Laboratory collapse tests were conducted on remolded Ili loess at different water contents, dry densities, and applied vertical pressures. A three-factor coupled model was developed using dimensionless pressure, degree of saturation, and void ratio. The main contribution is a continuous parameterization that allows the collapse coefficient to be calculated across the investigated soil states without independently refitting each water-content–dry-density combination. The model describes the nonlinear pressure-dependent response and incorporates moisture and pore-structure effects through saturation- and void-ratio-dependent parameters. Evaluation against the laboratory data yielded an overall coefficient of determination of R 2 = 0.783. A dimensionless wetting parameter was introduced to evaluate changes in remaining collapse potential across independently prepared moisture states within the tested range. An engineering-scale application to a 30 m loess profile predicted a self-weight collapse settlement of 3330.71 mm, compared with a reported field measurement of 3520 mm, corresponding to a relative error of 5.38%. Because some field conditions exceeded the laboratory calibration range, this comparison indicates application potential rather than general validation. The proposed formulation links routinely measured soil properties with collapse-coefficient estimation and layerwise settlement assessment.