Abstract: As for an immersed tunnel that was constructed using cast-in-place concrete in two layers, vertical and diagonal cracks were regularly found on the sidewall above the horizontal cast-in-place interface with height of 2 m.In order to analyze the cause of this sidewall cracking, vibrating wire strain sensors were embedded in the bottom plate and sidewall of the immersed tunnel. The results show that: 1) shrinkage strains were found at each monitoring point; 2) shrinkage strains gradually increased from the middle to the end of the sidewall in the horizontal direction;and 3) the shrinkage strains gradually increased from the bottom to the top of the sidewall in the vertical direction.Based on the horizontal tensile stress and shear stress of some of the monitoring points, the plane stress state analytical method was introduced to calculate the maximum principal stress and principal stress angle and to compare them with the development of cracks near the monitoring points. This analysis shows that the maximum principal stress angle is identical to the development direction of the cracks