Thixotropy of Clays with Various Index Properties-Paper

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This study examines thixotropic strength recovery in eight clays with varied index properties. Thixotropy is the time-dependent stiffening of remoulded clay at constant water content and volume. Researchers used fall-cone tests to track undrained shear-strength recovery, bender-element measurements in direct simple shear (DSS) apparatus to assess maximum shear modulus (Gmax), and DSS tests after reconsolidation to in-situ effective stress.<br /><br />After remoulding, both shear strength and Gmax increased with time, with broadly similar trends. The thixotropy strength ratio—the strength after resting divided by the immediate post-remoulding strength—generally increased with clay sensitivity, plasticity index, liquidity index, and water content. Mineralogy may also matter: prior work suggests greater smectite content can increase thixotropy, though this study’s samples showed no clear mineralogical trend. At water contents above 100%, the observed relationship may change, but the available data are limited.<br /><br />The strength recovery developed during rest was not evident in DSS tests after reconsolidation to in-situ effective stress. The authors suggest reconsolidation may destroy bonds formed during thixotropic recovery. This finding is relevant to offshore foundation design, where strength recovery after installation can affect soil resistance. Further testing is needed to clarify how thixotropy and reconsolidation interact under field conditions.

Keywords

thixotropy

clay strength recovery

remoulded clay

undrained shear strength

maximum shear modulus

direct simple shear

fall-cone test

clay sensitivity

plasticity index

reconsolidation