The strength recovery (healing) of the shear zone soil of a landslide during the dormant phase after the sliding affects the
reactivation of the landslide, and may play a key role in determining the stability of the landslide. In this paper, we report the
laboratory measurements of frictional strengthening characteristics of a red-bed landslide soil. Slide-hold-slide (SHS) experiments
and ultrasonic tests are performed on soil samples under natural moisture content and saturated conditions. The roles of
holding time, normal stress, and drainage conditions in friction enhancement are evaluated. All the experiments are performed
under room temperature. The saturated soil samples show the lowest recovery value of shear strength. It is found that red-bed
landslides have obvious healing properties. The recovery value log-linear depends on the holding time and proportional to the
normal stress, and the better the drainage condition is, the more obvious the recovery. Ultrasonic tests show that the wave speed
difference of soil sample before and after holding is proportional to the holding time.