Investigation of Development of the Earth Pressure Coefficient at Rest in Clay During Creep in the Framework of Hyper-Viscoplasticity

Abstract

The in-situ earth pressure coefficient at rest (K0) for clay has been widely discussed in the literature. In engineering practice, empirical relationships between K0, the 20 overconsolidation ratio (OCR) and the normally consolidated value, K0 NC , is often used.Where, K0 NC is as a function of friction angle (φ). These relationships do not distinguish between an increase in OCR due to unloading or due to creep of the material. Although there is significant literature on measurements of the change in K0 during unloading, there is a lack of data on the evolution of K0 due to creep. The few existing in-situ measurements of K0 are highly uncertain and difficult to be use for the purposes of investigating the time evolution of K0. There is therefore no clear consensus on the time evolution of K0 within the geotechnical community. During the last 20 years several creep models for clay have been developed within the framework of elasto-viscoplasticity. One common feature in many of these models is that they only predict a minor change in K0 with time, as K0 is given by one unique position 30 on the potential surface. This contrasts with the unproven opinion of many practitioners who think that K0 increases with time (even towards unity). In order to broaden the perspective of the discussion, this paper addresses the time evolution of K0 in the framework of hyper-33 viscoplasticity. This framework offers a possibility for an increase in K0 (even towards unity under certain conditions).

Tay creep: a multi-mechanism model for rate-dependent deformation of soils

“…Appropriate characterization and modelling of these viscous behaviours have been shown to be critical for solving geotechnical engineering problems related to the long-term performance of infrastructure (Oldecop & Alonso, 2007;Karstunen & Yin, 2010;Kelly et al, 2018) and the prevention and mitigation of geohazards (Zhu & Randolph, 2011;Alonso et al, 2016). Accordingly, many rate-dependent constitutive models have been developed for soils (Adachi & Oka, 1982;di Prisco & Imposimato, 1996;Kutter & Sathialingam, 1992;Leoni et al, 2008;Yuan & Whittle, 2018;Borja et al, 2020;Wang et al, 2020;Grimstad et al, 2020Grimstad et al, , 2021, by means of overstress theory (Perzyna, 1963), isotache method (Suklje, 1957;Bjerrum, 1967), or based on thermodynamic principles (Houlsby & Puzrin, 2007) . These existing models have been found to be effective in replicating the observed viscous characteristics of soils under monotonic histories of stresses or strains.…”