Dilatancy Behavior of Normally Consolidated Reconstituted Clays: A Novel Constitutive Model Based on Bounding Compression Line

This study investigates the dilatancy behavior of normally consolidated reconstituted clays. Comprehensive laboratory tests were conducted on deep Shanghai clay to investigate its mechanical behavior. The test results were compared with test data from the literature on reconstituted Shanghai clays from shallow and middle deposits to assess variations in their dilatancy behavior. However, in contrast to classical critical state soil mechanics, the reconstituted Shanghai clays from different layers—despite being normally consolidated—show varying dilatancy behavior, ranging from shear-induced contraction to dilation. This distinctive response is linked to the consolidation confining stress (p′)–void ratio (e) states of the clays, relative to an asymptotic compression relation termed the bounding compression line (BCL), to which the compression behavior of the Shanghai clays from different layers converges at large stresses. Specifically, clays with the consolidation confining stress–void ratio states closer to the BCL tend to exhibit contractive behavior, while those with consolidation confining stress–void ratio states distant from the BCL show dilative behavior. A new constitutive model incorporating the BCL concept was proposed to capture the aforementioned effects of consolidation confining stress–void ratio states on clay dilatancy. Comparing the mode simulation with test data shows that the proposed model effectively represents the distinct dilatancy behavior of normally consolidated reconstituted clays.