ANCIENT DRUMLIN HILLSLOPES AND MODERN EMBANKMENT DAMS / IMPLICATIONS FOR PREFERENTIAL SEEPAGE AND STABILITY IN ENGINEERING PRACTICE.

The scientific merit of the proposal rests on a novel comparison of new field data being acquired from two sites both with an extensive existing data set, one a recent large cutting in a drumlin in glacial till (at Loughbrickland, N. Ireland) and the other a large modern earth dam in Canada (the WAC Bennett Dam, British Columbia) where preferential flow has been found as part of a deficiency investigation following a sinkhole incident.Data from the measurement of the unusual groundwater regime of a large cutting in the lodgement till in N Ireland suggests that preferential seepage flow and internal erosion is occurring. Recent experience gained in a detailed analysis of field data from the till core of an earth dam in Canada and companion laboratory permeameter testing of soil samples also indicates that seepage induced internal erosion occurred. The objective of comparing an ancient till hillslope in the UK with a modern earth dam in Canada is to look for common features and spatial variations in the soil gradations and response to seepage that relate to the potential for internal instability. The benefit to the UK from examining in detail the Canadian data accrues by transferring the knowledge and insights obtained from this an invaluable long-term study of performance monitoring and laboratory testing of the reconstituted tills of a relatively young earth dam (approximately 35 years), and the implications of those finding, to aid the interpretation of a relatively short record of field observations in undisturbed tills of an ancient hillslope (over 10,000 years old). Accordingly, the proposal has a clear focus:To discern attributes of the long-term behaviour with respect to seepage, internal erosion and stability, of glacial tills, subject to groundwater seepage, that have implications for the behaviour of till cores in earth dams.It is expected that careful evaluation of the soils at the two sites, and consideration of the respective seepage regimes, will deliver a 'case-study' comparison of tremendous value to ongoing research efforts of each group, and a dissemination of significant university-industry research findings to the UK university sector.