Time-dependent behaviour of interactive marine and terrestrial deposit clay

A series of one-dimensional consolidation tests and triaxial creep tests were performed on Nansha clays, which are interactive marine and terrestrial deposits, to investigate their time-dependent behaviour. Based on experimental observations of oedometer tests, normally consolidated soils exhibit larger secondary compression than overconsolidated soils; the secondary consolidation coefficient (<i>C&#945;</i>) generally gets the maximum value as load approaches the preconsolidation pressure. The postsurcharge secondary consolidation coefficient (<i>C&#945;&#39;</i>) is significantly less than <i>C&#945;</i>. The observed secondary compression behaviour is consistent with the <i>C&#945;</i>/<i>C_c</i> concept, regardless of surcharging. The <i>C&#945;</i>/<i>C_c</i> ratio is a constant that is applicable to the recompression and compression ranges. Compared with the stage-loading test, the single-loading oedometer test can evaluate the entire process of secondary compression; <i>C&#945;</i> varies significantly with time and is larger than the <i>C&#945;</i> obtained from the stage-loading test. Based on experimental observations of triaxial creep tests, the creep for the drained state differs from the creep for the undrained state. The behaviour can be predicted by a characteristic relationship among axial strain rate, deviator stress level and time.