Physical characteristics of subglacial tills

Abstract

A regional database of the physical properties of glacial tills has been interrogated to produce characteristic design values and baseline construction values. Glacioterrestrial glacial till, one of the most distributed deposits in the world, is typically a heterogeneous mixture of clays, silts, sands, gravels and cobbles, which can contain remnants of earlier till including glaciolacustrine and fluvioglacial deposits that have been gravitationally compacted and sheared. This results in a complex deposit, which is spatially variable both in composition and fabric to the extent that the selection of design profiles is challenging. A study of the intrinsic properties of the tills in the North East of England together with a statistical analysis has led to the identification of two distinctly different, heavily overconsolidated tills that have profiles of strength, water content and density that lead to characteristic values based on the regional database and baseline values based on the local database that provide a priori knowledge for future investigations. This a priori knowledge has been used to determine the characteristic and baseline values for a new dataset from the region after demonstrating that the data fit with the regional database.