Abstract: This study examines the effects of siltyclay incorporation on the mechanical and durability performance of foamed lightweight soil. A series of laboratory tests—including unconfined compressive strength (UCS), splitting tensile strength, and flexural strength—were conducted on specimens prepared with varying siltyclay contents. Durability was further evaluated through dry-wet cycling and freeze-thaw cycling tests. The results show that increasing the siltyclay content leads to a progressive reduction in UCS, splitting tensile strength, and flexural strength. Based on the 28day UCS criterion, the siltyclay content should not exceed 30% for foamed lightweight soil used in subgrade beds and should remain below 50% for embankment applications. The incorporation of silty clay also impairs dry-wet cycling resistance and frost durability; higher siltyclay contents accelerate the decline in the dry-wet strength coefficient and increase compressivestrength loss after freeze-thaw cycling.

Key words: Foamed Lightweight Soils, Silty Clay, Mechanical Properties, Durability Performance