Study on the Unconfined Compressive Strength Property and Mechanism of Soda Residue Soil

To broaden the sources of earthwork and the utilization of soda residue (SR) and fly ash (FA), SR, FA, and clay were mixed to form a soda-residue soil (SRS) by adding externally moderate content of lime or/and cement for further stabilization. Through the orthogonal scheme, 9 groups of proportions were designed. Subsequently, the unconfined compressive strength (UCS) at different curing ages was conducted. Afterward, the stress–strain pattern, the UCS and water absorption, the sensitivity of factors and levels to UCS, and the deformation modulus were analyzed. Finally, the enhancement mechanism of SRS from physicochemical reactions was explored by analyzing gradation and microstructure. The results show that the patterns of stress–strain curves on SRS at different curing ages are similar; all have obvious stress peaks, and the specimens of SRS present a brittle failure. With the extension of curing ages, the UCS of all proportions increased; the UCS of the G2 group increased the most, reaching 85.44