To investigate the strength and deformation behaviors of Shanghai deep sands under the effect of intermediate principal stress (σ₂), multiple sets of true triaxial tests are conducted on Shanghai deep sand layers 7, 9, and 11. The stress-strain and volumetric strain behaviors under different coefficients of intermediate principal stress (b) are analyzed, and the variation laws of friction angles and failure envelopes with b are clarified. Additionally, the parameter differences between these 3 sand layers are compared. The results indicate that σ₂ has a significant impact on the strength and deformation behaviors of Shanghai deep sands. The strength decreases with the increase of b, while dilatancy changes in the opposite direction. Layer 9 exhibits the most significant softening characteristics and dilatancy with the highest strength, while layer 11 almost exhibits hardening and contraction with the lowest strength. The behaviors of layer 7 are between the two and closer to those of layer 9. Compared to the L-D and M-C criteria, the SMP criterion is more suitable for predicting the strength index of Shanghai deep sands under the effect of σ₂.