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Controllability of wetting-induced compaction

Compaction processes caused by wetting have been a topic of interest since the early developments of unsaturated soil mechanics. These events are often referred to as “collapses” because they take place at constant applied stress and may have detrimental consequences for field-scale engineering applications. While wetting-induced compaction has been widely studied in the past literature, the controllability of such deformation processes has been rarely considered [1]. Recent evaluation of the second-order energy input in unsaturated soils [2], along with controllability criteria offers the opportunity to assess the mechanics of such processes from a hydro-mechanical standpoint. In this contribution, we use such mathematical tools to interpret classic oedometric wetting experiments on unsaturated soil specimens. For this purpose, we consider two distinct scenarios of saturation: (i) suction-controlled wetting; and (ii) inundation via water-volume injection. The potential loss of control associated with these two scenarios has been assessed by calibrating an elastoplastic model for unsaturated soils to capture the macroscopic compression/wetting response measured in experiments from the literature. In all cases, the saturation processes were found to be controllable under all the considered modes of wetting, suggesting that wetting-collapse events are in fact fully controllable deformation mechanisms. Furthermore, the conditions associated with the loss of control have been inspected mathematically through parametric studies. Such analysis has pointed out that wetting-compaction can be affected by a loss of control only in presence of highly water-sensitive materials subjected to sharp inundation, i.e. only under very particular circumstances able to mobilize a non-controllable deformation response.

References:

1. Mihalache, Constance, and Giuseppe Buscarnera. "Is Wetting Collapse an Unstable Compaction Process?." Journal of Geotechnical and Geoenvironmental Engineering (2014).

2. Buscarnera, Giuseppe, and Claudio di Prisco. "Discussing the definition of the second‐order work for unsaturated soils." International Journal for Numerical and Analytical Methods in Geomechanics 36.1 (2012): 36-49.

Author(s):

Constance Mihalache    
Northwestern University
United States

Giuseppe Buscarnera    
Northwestern University
United States