Without representative data of the whole family of subglacial sediments (EVANS et al., 2006) the rheological study of them is almost impossible, but some light can be found using in situ geotechnical tests. Pressuremeter tests that permit elements of consolidation history to be deduced have been obtained from glacial sediments in the Valley of Andorra in the South Eastern Pyrenees. Relatively coarse grained tills lie between well-defined aquifers in a relatively simple layered sequence. Data from tills that reflect several phases of glaciation of the Valley show systematic patterns of preconsolidation. These are interpreted to  reflect the geometry of the subglacial hydraulic system, in which the locations of major subglacial drainage channels and the pattern of groundwater flow are principal determinants of glacial consolidation history. The sediments were subjected to loading and unloading cycles associated with repetitive palaeo-hydraulic patterns, producing stiffening and kinematic hardening of the subglacial sediments. Three kind of stress/strain behaviours can be deduced: Elastoplastic, Hyperplastic and Hyperplastic-Hypoplastic. Hyperelastic and hypoplastic behaviour is superimposed on earlier hyperplastic states in Coulomb type sediments.

It is suggested that in along the centre line of the Valley, where there were subglacial streams that drew down groundwater pressures, subglacial effective pressures were high, with strong coupling between the glacier and its bed and ploughing through unconsolidated subglacial sediments. There were low subglacial effective pressures at the lateral valley floor. These conditions determined the production of failure structures and patterns of consolidation in the floors of glaciated valleys.

EVANS, D.J.A.; PHILLIPS, E.R.; HIEMSTRA, J.F. & AUTON, C.A. (2006) “Subglacial till: formation, sedimentary characteristics and classification”; Earth-Science Reviews, 78, 115-176