A model for grain-crushing-induced landslides—Application to Nikawa, Kobe 1995

Abstract

A novel method is developed, motivated by one of the mysteries of the Hyogoken-Nambu (Kobe): the Nikawa landslide. To this end, prompted by the hypothesis of “sliding-surface liquefaction” advocated by Sassa [Development of a new cyclic loading ring shear apparatus to study earthquake-induced-landslides. Report for grant-in-aid for development of scientific research by the Ministry on Education, Science and Culture, Japan (project no. 03556021), 1994, p. 1–106; Keynote lecture: access to the dynamics of landslides during earthquakes by a new cyclic loading high-speed ring shear apparatus. In: Proceedings of the sixth international symposium on landslides, 1992. In: Landslides, vol. 3. Balkema: Rotterdam; 1995. p. 1919–39], a dynamic analysis of the early stages of an earth slide is presented considering two mechanically coupled sub-structures: (a) the rapidly deforming shear band at the base of the slide and (b) the accelerating sliding mass modeled as a rigid body. The proposed model for sliding is based on: (i) the concept of high pore-water pressure generation by grain crushing along the sliding surface (proposed by Sassa et al. in 1995), (ii) an experimental model developed by Hardin [Crushing of soil particles. J Geotech Eng 1985;111(10):1177–92] for crushing of soil particles under compression and shear, expressed with a set of developed equations governing the mechanism of breakage, and (iii) the hysteretic stress–strain Bouc–Wen-type constitutive model coupled with the Coulomb friction law. An attempt is made to adjust the model parameters to Sassa's experimental data in ring-shear tests. The method leads to a reasonable prediction of the large displacement of the Nikawa landslide. A sensitivity analysis is also carried out for the influence of key model parameters (e.g. shape, crushing hardness, void ratio, grain size distribution, effective normal stress) on the pore-pressure rise due to particle breakage.