Dunvegan Landslide

All-weather transportation in the Peace River country of Alberta has proven to be an outstanding problem since the days of the voyageurs. This country, the most northerly productive land in Canada, yields large crops. In the early development of Alberta, the Peace River country and Dunvegan crossing played very important roles and persist in importance today.

The crossing of the Peace River at Dunvegan was originally made by canoe. As the population density increased, transportation capable of greater capacity and with a more predictable schedule became necessary, and a ferry system was initiated by the provincial government. Today, this is inadequate because of its limited capacity and due to the fact that in certain spring and fall months it is not possible to negotiate the crossing at all. The obvious solution to this was an all-weather bridge which is under construction at present.

The topography of the Peace River crossing is very rugged consisting of steep banks some 700 feet in height. Because of this topography, the approach roads to this bridge pose a serious problem. In solving the problem of maintaining gentle grades in the approach to the bridge, the Dunvegan Creek valley offered a natural route. Certain large fills were required along sections of the road. As the predominant valley-forming agency along these banks is landslide and slump the result of construction over this terrain was uncertain.

In the light of this investigation, it is reasonable to assume that the conventional methods of analysis, although indispensable, are not sufficient to adequately explain the phenomenon of loss in strength in detailed form. It has become increasingly apparent to the writer that basic research into the mineralogical and physico-chemical properties of these soils is required. The importance of this type of research has been demonstrated by Lambe, Warkentin, Grim and other prominent investigators. Certain procedures have already been established in this connection. The application of this form of research to our problems is felt to be of importance.

The stabilization of these overconsolidated soils has always presented a serious problem. The application of electro-osmotic methods has been thought of as one possible means. Research could be profitably directed towards this. Applied to preconsolidated materials, electro-osmotic stabilization is a virgin and challenging field. There is sufficient evidence to indicate that electro-osmosis would aid materially in stabilizing the Dunvegan slopes.

The following sections of this report will cover, in more detail, various aspects of the problem. It is concluded that the work carried out is of significance, but a great deal of research into detailedaspects is necessary before the general problem of stability of pre-consolidated clay slopes can be satisfactorily solved.