Abstract: The ShenzhenZhongshan link immersed tunnel first adopts steel shell concrete structure on a large scale in China. The new structural type is complex, voids easily form at the interface of steel plate and coagulation during selfcompacting concrete pouring, and the local void will lead to the reduction of compressive strength and further affects the overall safety of the structure. A case study is conducted on the ShenzhenZhongshan link immersed tunnel to realize the rapid and accurate detection of steel shell concrete void defects. Research on the steel shell concrete void quality detection method for a large immersed tunnel is conducted based on the impact imaging method. First, examining the variation law of nearsource wave field response characteristics, the steel shell concrete void detection technology, including equipment, software, and model, is developed. Second, the evaluation index of steel shell concrete void quality is proposed on this basis. Finally, the effect of the method is validated by a fullscale model test, and the detection result′s accuracy reaches 91%. The result shows that the impact imaging method can accurately describe the void distribution of steel shell concrete and quantitatively evaluate the void conditions, which can provide technical support for the highquality construction and structural optimization of the ShenzhenZhongshan link.

Key words: ShenzhenZhongshan link immersed tunnel, steel shell concrete, nondestructive test, impact imaging method, fullscale model test, void detection