Reactivation of an ancient landslide

This paper describes the reactivation of an ancient landslide during the construction of a fill buttress. Even though precautions were taken during construction of the buttress, such as excavating it in 30-m-long (100-ft-long) segments, the ancient landslide nevertheless was reactivated. The reactivated landslide moved laterally about 5–8 cm (2–3 in.), which resulted in significant damage, such as cracking to building foundations, walls, and ceilings, as well as distortion of door frames and windows. An interesting observation was that the ancient landslide, once activated, did not stop immediately after the buttress had been backfilled. The lateral movement continued for about 10 months, at a decreasing rate of movement. This movement was probably due to the slow closure of the ground cracks as well as the deformation of the landslide into the buttress. This case history illustrates the disadvantage of using a buttress to stabilize an ancient landslide, especially when the excavation is below the rupture...