Influence of soaking on stress-strain characteristics of fly ash

A series of confined uniaxial compression (oedometer) tests and triaxial compression tests were conducted to study the influence of soaking on the stress-strain characteristics of coal fly ash widely used in Mainland China. The focus was on the collapsibility of fly ash with porous structure under different conditions, such as different relative density, initial water content, stress state, stress level, consolidation stress ratio, and soaking history. Main results of the test program are presented in this paper. It is determined that soaking collapsibility of fly ash depends on the relative density, initial water content, stress state, stress level, consolidation stress ratio, and soaking history, which the fly ash has experienced. The larger the relative density, the initial water content, and the consolidation stress ratio σ3/σ1 are, the smaller the soaking collapsibility is. The soaking collapsibility increases with stress level, which has a strong influence on the stress-strain characteristics of the fly ash.