Abstract: In engineering projects of cold regions, the salt-freezing coupling effect often exacerbates the strength degradation of saline soil. We aim to investigate the variations in compressive performance of lime-and-flyash-solidified carbonate soil under freezing conditions. With curing agent dosage, temperature, and loading rate as influencing parameters, we conducted unconfined compression tests on lime-and-flyash-solidified carbonate saline soil and subsequently proposed a damage constitutive model considering temperature and loading rate. Results indicate that lime and fly ash significantly enhance the compressive strength of carbonate soil, altering its stress-strain curve from weak strain softening to distinct strain softening. Optimal curing occurs with the addition of 3% lime and 12% fly ash. Temperature and loading rate markedly affect the compressive strength and elastic modulus of the solidified carbonate soil, with their relationship being expressed as a nonlinear function. Temperature exerts far more larger influence on compressive strength than curing agent dosage and loading rate. The established damage model effectively captures the stress-strain relationship and the variation trend of soil damage variables.

Key words: frozen saline soil, lime-flyash improvment, unconfined compressive strength, loading rate, damage constitutive model