Investigation on strength characteristics of fly ash treated dredged marine clay with various pore water salinities

This study investigated the strength characteristics of dredged marine clays treated with fly ash with varying porewater salinities. A series of laboratory tests were conducted on fly ash-treated dredged marine clay specimens with various salinities and curing times. In the direct shear tests, observed patterns revealed a consistent initial rapid increase in shear stress with the increase of horizontal displacement, followed by either a gradual decline or stabilization after reaching the peak shear stress. The variation curve consistently positioned the lower salinity or longer curing time above the higher salinity or shorter curing time. Furthermore, the shear strength at a given vertical stress consistently decreases with increasing salinity while ascending with increasing curing time. This indicated that curing time positively influences shear strength development, while the presence of salt negatively affects it. Both strength parameters cohesion and friction angle exhibited growth trends with increased curing time but displayed a decline as salinity increased from 0% to 6%. Unconfined compressive strength test results showed a strain-softening behavior for all tested specimens. The compressive strength demonstrated a declining trend with rising salinity, with a more pronounced decrease observed within the initial 7d compared to the less significant change between 7d and 28d.