Abstract: To study the strength and deformation of municipal solidified sludge after different freeze-thaw cycles, the sludge solidified by CJYT-1 solidifying agent was tested through true triaxial tests. The stress-strain relationship and the strength and deformation characteristics after freeze-thaw cycles number of 0, 1, 3, 5, 8, 10 are obtained, and the influence of intermediate principal stress ratio b and the number of cycles N on the soil strength parameters (including cohesion c′ and internal friction angle ?′ ) are studied. The results of the freeze-thaw cycle test show that the unconfined compressive strength and density of the solidified sludge gradually decrease with the increase of the number of freeze-thaw cycles, and the change slows down and stabilizes after 8 cycles. The cohesion and the internal friction angle both increase with the increase of b. Compared with b=0, when b=1, the growth rate of and can reach 16.77% and 12.3%, respectively. As the number of cycles N increases, the failure strength of the soil gradually decreases, and the failure stress ratio Mb generally decreases. The dilatancy of the specimen does not change significantly. The cohesion and internal friction angle decrease with the increase of freeze-thaw cycles N. Based on the two commonly used, Lade-Duncan and Matsuoka-Nakai failure criteria, combined with the true triaxial test data of solidified sludge, a failure criterion suitable for solidified sludge is proposed, and the -b relationship curve of the criterion is analyzed. Comparing the failure criteria proposed in the article, Lade-Duncan and Matsuoka-Nakai failure criteria, the test results are closer to the failure criteria in the article.

Key words: freeze-thaw cycles, sludge solidification, three-dimensional mechanical properties, stress-strain relationship, failure criteria