HR: 1340h
AN: V43B-1423    [Abstracts]
TI: Geotechnical Analysis of the Chaos Jumbles Rockfall Avalanches at Lassen Volcanic Park, California
AU: * Ninivaggi, S
EM: ninivagg@unr.nevada.edu
AF: University of Nevada, Reno, Department of Geologic Sciences, M.S. 172, Reno, NV 89557 United States
AU: Watters, R J
EM: watters@mines.unr.edu
AF: University of Nevada, Reno, Department of Geologic Sciences, M.S. 172, Reno, NV 89557 United States
AB: The Chaos Jumbles rockfall avalanches are a series of three slope failures that occurred from the northwest side of the Chaos Crags approximately 300 years ago. Run out distances for the three rockfall avalanches range from 4.3km to 2.5km. Previous investigations have shown that the failure occurred from one of the six domes of the Chaos Crags. The cause of the failure has been investigated, but has not been determined (Crandell et al, 1974 and Eppler et al, 1987). This research uses geotechnical data obtained from field investigations, laboratory testing and computer modeling to determine the failure processes. Samples and discontinuity data were collected from the accessible areas along the base of the failure scarp. Samples included in situ rock discontinuities for shear strength analysis, rock cores for uniaxial and triaxial strength analyses and field measurement of discontinuity orientations. The data is used to model different failure scenarios along the existing scarp using limit equilibrium, finite difference and distinct element programs. The preliminary results of our analysis show that a set of discontinuities parallel to the failure surface along with there conjugate set perpendicular to the failure surface played a major role in the in the failure at the Chaos Jumbles rockfall avalanches. Research continues on modeling the failure and the run out distances of the avalanches.
DE: 8499 General or miscellaneous
DE: 5194 Instruments and techniques
DE: 5199 General or miscellaneous
DE: 5460 Physical properties of materials
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2004 AGU Fall Meeting