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Title: Till geotechnics and ice sheet dynamics
Author: Dobbie, Karen Elizabeth
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1992
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This thesis studies geotechnical properties of former subglacial sediments to establish the conditions found at the base of an ice sheet. Whilst many advances have been made in the theoretical analysis of ice sheet dynamics, little quantitative information exists about the physical processes that occur beneath an ice sheet. These processes depend on the type of surface over which the ice flows and on whether the base of the ice is melting. Until recently, most models of ice sheet flow have assumed that ice moves over a rigid surface as a result of deformation within the ice, or by sliding at its base. It has subsequently become clear that where ice overlies unlithified sediments they can deform, thus contributing to the forward motion of the ice. The basal boundary is difficult to observe directly, however information can be obtained directly by studying the sediments left behind when the ice has retreated. An advancing ice sheet loads the sediments over which it flows. Sediments consolidate in response to this additional load, providing that water can drain from the sediment pores. Sediments underlying a basally melting ice sheet must still allow melt water to drain through them and thus will not consolidate to the same extent as a non-glacial sediment under the same load. The sediments expand on retreat of the ice however they retain a record of the maximum pressure to which they were subjected, known as the preconsolidation pressure. The preconsolidation pressure is assumed to have occurred at the glacial maximum when the ice sheet was in a steady state, however the existence of a meltwater flux means that the preconsolidation pressure preserved is not a simple consequence of the overburden of ice and sediments. A one dimensional drainage model is adopted to investigate subglacial groundwater flow. Melt water is assumed to drain vertically through an upper layer of low permeability sediments into an aquifer. The theoretical distribution of pressure in the one dimensional model is derived and a relationship between the effective pressure gradient, potential pressure gradient and gravitational gradient established.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available