LANDSLIDE HAZARDS RESEARCH
Modelling
the dynamic behaviour of rapid landslides
Design
of debris flow/avalanche protective structures
Brittle
and ductile toppling of large rock slopes
Landslides are one of the costliest natural hazards. The direct annual cost of landslide damage has been estimated at $2 billion in the United States and $124 million in Canada (Geological Survey of Canada, unpublished). Indirect costs are probably comparable. While North America has its share of landslide problems, other parts of the world have even greater need to deal with these hazards. It is a matter of serious concern that many developing nations face particularly great degree of landslide hazards, while having few resources to cope with them. Recent examples from Venezuela and Nicaragua, involving life loss in the tens of thousands, have been well exposed in the media. However, countries such as China, India, Pakistan, Nepal, Chile, Ecuador, Brazil and many others suffer continuing losses, year after year, to the detriment of their national economies. Landslide losses in all parts of the world are likely to continue increasing, as growing population, combined with the need to protect natural and agricultural areas, presses human developments ever closer to unstable slopes. The only way to reduce such losses is to develop better understanding of landslide processes and more reliable techniques of predicting their potential effects and designing remedial or protective measures.
The long-term objective of the engineering geology research group at UBC is to provide methods for reliable, quantitative assessment of landslide hazards and for the derivation of parameters needed for design and rational decision-making.
The Frank Slide, Alberta
Modelling of the dynamic
behaviour of rapid landslides. Top
Rapid landslides include debris flows, debris avalanches and rock avalanches. The dynamic model, “DAN” (Hungr, 1995) has introduced several novel features, which are essential for realistic prediction of landslide behaviour. It has also been calibrated by back-analysis of more varied case histories than any other existing model. However, further improvements and calibration are needed. Ultimately, the goal is to provide firm guidelines for selection of model configuration and parameters such that a prediction of the likely range of runout behaviour can be made for any type of landslide under given circumstances.
A flow slide of approximately 60000 m3 of waste in a coal mine
in north-eastern British Columbia, Canada. The slide debris traveled for 2 km.
A dynamic analysis of
a rock slide-debris avalanche that occurred at Nomash River, Vancouver Island
in May, 1999. The event began with a
rock slide of approximately 300,000 m3 (see below) but incorporated
several times as much volume by entraining saturated soil from the path during
motion.
Design of
debris flow/avalanche protective structures:
Top
A series of physical experiments involving flow of frictional materials on a sloping surface against oblique dykes and in a curving channel have been completed. The results provide a design method suitable for estimating the required height and angle of a deflecting dyke, to prevent overtopping. An analysis of an actual case of a dyke subjected to a debris flow (at Portia on the Coquihalla Highway) has also been carried out.
A video record of a laboratory experiment investigating
the deflection of a
flowing sand slide by an oblique dyke.
Brittle and ductile toppling
of large rock slopes: Top
Slow, ductile toppling of rock masses commonly creates large-scale mountain slope deformations. In some cases, toppling can initiate a brittle catastrophic rockslide. A theoretical and field-based study has been aimed at distinguishing these two alternative modes of toppling. The results indicated two distinct types of behaviour: ductile, self-stabilizing flexural toppling in weak rock with a single dominant joint set; and brittle, catastrophic block toppling in strong rock containing persistent, down-slope oriented or horizontal cross-joints. The two mechanisms exhibit very different patterns of pre-failure stress (Nichol and Hungr, in press).
A numerical model of a large flexural topple in weak, schistose rock
Failure behaviour of landslides in clay and silt: Top
Two large landslides in overconsolidated glacio-lacustrine clay and silt deposits of British Columbia river valleys have been examined. Both cases are quite similar in their main aspects. However, their failure behaviour was very different. One continues to exhibit intermittent, manly ductile deformations with limited mobility, which are typical of compound landslides in stiff clay. The other suddenly developed into a catastrophic, extremely rapid flow slide of 6.4 Mm3, damming a large river in the course of a few minutes and projecting a wave onto the opposite bank. A comparison of the two cases has been made and possible mechanisms for brittle flow slide formation have been proposed (Fletcher et al., in review).
A rapid flow slide on the Peace River,
north-eastern B.C., involving 7 million m3
of overconsolidated clay and silt. The deposit is approximately 1 km long
(Fletcher et al., 2001, in review).
A Post-Doctoral Fellow, Dr. A.Mellal recently developed a new method of
analysis and software to calculate rock fall trajectories for use on
transportation routes.
Boulder trajectories calculated with the
program “PIERRE” for comparison
with full scale experiments carried out in a
quarry near Hope, B.C.
Rock fall risk assessment: Top
Records of rock fall occurrence have been collected from highways and railways of south-western B.C. Magnitude-frequency curves have been constructed and a new method of estimating rosk to traffic has been proposed (Hungr et al., 1998).
A typical Cumulative Frequency-Magnitude (CFM) relationship for rock falls
along a highway in British Columbia, Canada (Hungr et al., 1998).
A new method of rating rock slopes along transportation routes has been developed under a research grant from CP Rail (Jakob and Hungr, 2000). This method is based on accepted principles of rock mechanics and provides more objective description of rock mass properties than any existing technique.
The engineering geology research group takes every opportunity to collect descriptive and quantitative data concerning landslide case histories. We examine landslide sites shortly after occurrence, whenever possible.
A rock slide-debris avalanche at Nomash
River, Vancouver Island, May, 1999
The following topics may be addressed in the near future, given the availability of personnel and funding:
1) Relationship between climate and occurrence of landslides in B.C., studied using a high resolution climatic model
2) Mechanism of natural seepage erosion of slopes. The seepage erosion process is capable of eroding gullies several hundreds of metres long within a period of several hours (e.g. Hungr and Smith, 1985). Several buildings of the University of British Columbia are potentially subject to seepage erosion hazards.
3) Use of satelite-based radar imaging and interferometry for identification and monitoring of large scale slope deformations in the Coast Ranges, B.C.
4) Significance of natural soil cementing for shallow instability on forested slopes.
Hungr, O., Evans, S.G., Bovis, M., and Hutchinson, J.N., Review of the classification of landslides of the flow type. Accepted
for publication in Environmental and Engineering Geoscience, December, 2000 (20 msp, 18 figs., 3 tabs.)
Nichol, S., and Hungr, O. Brittle and ductile toppling of large rock slopes. Accepted for publication by the Canadian
Geotechical Jounal, November, 2000 (23 msp., 12 figs., 2 tabs.).
Hungr, O., 2000. Analysis of debris flow surges using the theory of uniformly progressive flow. Earth Surface Processes and
Landforms 25:1-13.
Hungr, O., Dawson, R., Kent, A., Campbell, D. and Morgenstern, N.R., 2000. Rapid flow slides of coal mine waste in British
Columbia, Canada. In "Catastrophic Landslides" Geological Society of America Reviews in Engineering Geology 14 (in press, 17 msp., 22 figures).
Jakob,M., Anderson, D., Fuller,T., Hungr,O. and Ayotte, D., 2000. An Unusually Large Debris Flow at Hummingbird Creek,
Mara Lake, British Columbia. Canadian Geotechnical Journal Vol. 38 (20msp, 10 figs, in press)
Evans, S.G., Hungr, O., and Clague, 2000. The 1984 rock avalanche from the western flank of Mt. Cayley, Garibaldi
Volcanic Belt, British Columbia: description and dynamic analysis. Engineering Geology. (17 msp, 20 figs., in press.)
Hungr, O., Evans, S.G., and Hazzard, J., 1998. Magnitude and frequency of rock falls and rock slides along the main
transportation corridors of south-western British Columbia. Canadian Geotechnical Journal , 36:224-238.
Hungr, O., and Beckie, R.D., 1998. Assessment of the hazard from rock fall on a highway, Discussion of a paper by
C.M.Bunce, D.M.Cruden and N.R.Morgenstern, Canadian Geotechnical Journal, 35/3: 409.
Hungr, O., 1997. Analysis of the motion of a debris avalanche event. Chikyu (“Earth”) magazine, Japan, special issue focused
on debris flow hazards, H.Fukuoka, Ed., 19:661-665 (translated into Japanese).
Hungr, O., 1995. A model for the runout analysis of rapid flow slides, debris flows and avalanches. Canadian Geotechnical
Journal, 32(4):610-623.
Evans, S.G., Hungr, O. and Enegren, E.G., 1994. The Avalanche Lake rock avalanche, Northwest Territories, Canada:
description, dating and dynamics. Canadian Geotechnical Journal, 31: 749-768.
Hungr O.,1994. A general limit equilibrium model for three-dimensional slope stability analysis. Discussion of an article by
L.Lam and D.G. Fredlund. Canadian Geotechnical Journal, 31: 793-795.
Evans, S.G., and Hungr, O., 1993. The assessment of rockfall hazards at the base of talus slopes. Canadian Geotechnical
Journal, 30: 620-636.
Hungr, O., 1990. Mobility of rock avalanches. Reports of the National Research Institute for Earth Science and Disaster
Prevention, Tsukuba, Japan, 46: 11-20.
Jackson, L.E., Hungr, O., Gardner, J., and MacKay, K., 1990. The Cathedral Mountain Debris Flows. Bull. Int. Association
of Engineering Geology, 40: 35-54
Hungr, O., Morgan, G.C., Van Dine, D.F. and Lister, D.R., 1987. Debris flow defences in British Columbia. In J.E. Costa
and E. Wieczorek, Eds., Debris Flow: Process, Description and Mitigation. GSA Reviews in Eng. Geology VII, 201-222.
Cruden, D.M. and Hungr, O., 1986. The debris of the Frank Slide and theories of rockslide-avalanche mobility. Canadian
Journal of Earth Sciences, 23: 425-432.
Hungr, O., and Evans, S.G., 1984. An example of a peat flow near Prince Rupert, British Columbia. Canadian Geotechnical
Journal, 22: 246-249.
Hungr, O. and Morgenstern, N.R.,1984. Experiments in high velocity open channel flow of granular materials. Géotechnique,
34: 405-413. Discussion and Reply, 35: 383-385.
Hungr, O., and Morgenstern, N.R., 1984. High velocity ring shear tests on sand. Géotechnique, 34: 415-421.
Hungr, O., Morgan, G.C. and Kellerhals, R., 1984. Quantitative analysis of debris torrent hazards for design of remedial
measures. Canadian Geotechnical Journal, 21: 663-667.
Gerath, R.F. and Hungr, O., 1983. Landslide terrain, Scatter River valley, north-eastern British Columbia. Geoscience
Canada, 10: 30-32.
Fell, R., Hungr, O., Leroueil, S. and Reimer, W., 2000. Keynote Paper, - Geotechnical engineering of the stability of natural
slopes and cuts and fills in soil. Procs., GeoEng2000, International Conference on Geotechnical and Geological Engineering in Melbourne, Australia, November, 2000, 104pp.
Ayotte, D. and Hungr, O., 2000. Calibration of a runout prediction model for debris flows and avalanches. Procs., 2nd.
International Conference on Debris Flows, Taipei, Wieczorek, G.F. and Naeser, N.D., Eds., 505-514, Balkema, Rotterdam.
Ayotte, D., Evans, N. and Hungr, O., 1999. Runout analysis of debris flows and avalanches in Hong Kong. Proceedings,
Slope Stability and Landslides, Vancouver Geotechnical Society Symposium May, 1999, 39-46.
Fletcher, L., Hungr, O., Watson, A. and Thomson, B., 1999. Failure mechanism and behaviour of a large landslide in glacio-
lacustrine silt and clay, Chilliwack River Valley, B.C. Proceedings, Slope Stability and Landslides, Vancouver Geotechnical Society Symposium May, 1999, 55-62.
Hungr, O., Yau, H.W., Tse, C.M., Cheng, L.F. and Hardingham, A.D.,1998. Natural slope hazard and risk assessment
framework. Procs., Inst. of Civil Engs., International Conference on Urban Ground Engineering, Hong Kong.
Hungr, O., 1997. Some methods of landslide hazard intensity mapping. Invited paper, Procs., Landslide Risk Workshop,
R.Fell and D.M. Cruden, Eds., Balkema, Rotterdam , pp. 215-226.
Hungr, O., and Evans, S.G., 1997. A dynamic model for landslides with changing mass. In Marinos, P.G., Koukis, G.C.,
Tsiambaos, G.C. and Stournaras, G.C., Eds., Procs., IAEG International symposium on engineering geology and the environment, Athens, June, 1997, 1:719-724.
Jakob, M., Hungr, O., and Thomson, B., 1997. Two debris flows with anomalously high magnitude. Debris Flow Hazards
Mitigation, Mechanics, Prediction and Assessment. Procs., The First International Conference on Debris Flow Hazards ASCE, C.L.Chen, Ed., San Francisco, pp. 382-394.
VanDine, D.F., Hungr, O., Lister, D.R. and Chatwin, S.C., 1997. Chanellized debris flow mitigative structures in British
Columbia, Canada. Debris Flow Hazards Mitigation, Mechanics, Prediction and Assessment. Procs., The First International Conference on Debris Flow Hazards ASCE, San Francisco, In Chen, C., Ed., pp. 606-615
Hungr, O., Gerath, R.F. and VanDine, D.F., 1995. Landslide hazard mapping in British Columbia: a review and suggested
methodology. Published by the Resource Inventory Committee, Government of BC, Victoria, 35 pp.
Tse, C.M., Chu, T., Wu, R., Hungr, O. and Li, F.H., 1999. A risk-based approach to landslide hazard mitigation design.
Procs., Hong Kong Institution of Engineers, Geotechnical Division Annual Seminar, May 1999, 35-42.
Hungr, O., 1997. Slope stability analysis. Keynote paper, Procs., 2nd. Panamerican Symposium on Landslides, Rio de
Janeiro, Int. Society for Soil Mechanics and Geotechnical Engineering, 3: 123-136.
Hungr, O., 1997. Recognition of the potential for catastrophic failure in large rockslides. Invited paper, In Sassa, K., Ed., Procs., International Symposium on Landslide Hazard Assessment, Xian, China, pp. 65-80.
Hungr, O. and Evans, S.G., 1996. Rock avalanche runout prediction using a dynamic model. Procs., 7th. International Symposium on Landslides, Trondheim, Norway, 1:233-238.