To study the wetting deformation characteristics of undisturbed loess under true triaxial force-water path

the true triaxial apparatus with rigid-flexible-flexible loading boundary was used to carry out the true triaxial single-line humidification test of undisturbed loess in Xi’an under different spherical stresses

intermediate principal stress parameters and stress ratios. The influence of true triaxial force-water path on the humidification deformation characteristics of undisturbed loess was comprehensively analyzed. The test results show that the relationship curve between the wetting volumetric (deviatoric) strain and the spherical stress presents a three-stage of slow-steep-slow. When the spherical stress is in the second stage

the wetting collapsibility of the soil is the largest

and a large wetting deformation can occur. At a certain stress ratio

the wetting volumetric strain gradually increases with the spherical stress

and the increase of the wetting volumetric strain decreases when the spherical stress exceeds 200 kPa. Finally

the variation law between the intermediate principal stress and each humidification strain is analyzed

and the calculation expression of loess collapsible deformation considering the intermediate principal stress is given according to the test results.