<p>This study presents the deformation characteristics of the passive soil arching effect in unsaturated compacted clay, including the displacement field and strain field. In this study, the displacement field and the strain field during passive soil arching effect were monitored by the DIC system under plane-strain condition. The testing results indicate that the distribution locations and ranges of the disturbed zone (defined in the displacement field), tensile and compressive zones (defined in the strain field) are influenced by the initial placement conditions of the fill. Among them, the pattern of the volumetric strain field reveals that the dilatancy of the fill is mainly caused by the development of the shear bands. The sample with a lower water content or a higher dry density exhibits a larger rigid zone (fill displacement increases at the same rate as the trapdoor). As the trapdoor displacement increases, the stress ratio first increases and then decreases to a stable value, while the shear strain gradually increases. By comparing testing results with those of the passive soil arching effect in sand, the evolutionary characteristics of strain fields of the passive soil arching effect in unsaturated compacted clay are summarized. The comparison results indicate that for samples on both the dry and the wet side, the tensile zones are covered by the shear bands. Meanwhile, the dilative zones are determined by the area where cracks are generated.</p>