Strength Model of Soda Residue Soil Considering Consolidation Stress and Structural Influence

Soda residue (SR) is a type of industrial waste produced in the soda process with the ammonia-soda method. Applying SR to backfilling solves the land occupation and environmental pollution problems in coastal areas and saves material costs for foundation engineering. The strength characteristics of soda residue soil (SRS) under different consolidation conditions are the key points to be solved in the engineering application of SRS. Triaxial compression tests were performed on the undisturbed SRS of Tianjin Port. The shear properties of SRS under different consolidation conditions were then discussed. Meanwhile, a structural strength model (SSM) based on Mohr-Coulomb theory was proposed. SSM reflects the influence of soil structure on undrained strength (Cu) and divides the Cu into the following two parts: friction strength (Cuf) and original structural strength (Cu0). Cuf characterizes the magnitude of friction between soil particles, which is related to the consolidation stress. Meanwhile, Cu0 represents the structural effect on soil strength, which is related to the soil deposition and consolidation processes. SSM was validated by the test data of undisturbed soils. Results reveal that the undisturbed soil generally had a certain Cu0. Therefore, the SRS strength model was established by combining the experimental law of SRS with SSM. Error analysis shows that the SRS strength model can effectively predict the Cu of undisturbed SRS in Tianjin Port under different consolidation conditions.