Research on Formation Mechanism and Optimization Control of Segment Crack Damage under Combined Thrust

The damage of segment under the thrust of jacks during construction was studied. Based on the actual situation of a subway line in Suzhou, a multi-ring three-dimensional finite element model was established to analyze the formation, evolution and distribution of shield segment fracture under the combined action of excessive and uneven thrust of jacks, and the corresponding engineering control measures were put forward. The results show that the segment damage is mainly distributed uniformly along the bolt hole under different thrust, and the damage on the inner cambered surface is larger than that on the outer cambered surface. The maximum damage factor of the segment increases approximately linearly, and the damage area increases nonlinearly. When thrust is evenly distributed, segment damage is mainly concentrated in the first ring segment, while when thrust is not uniform, segment damage will transfer to the side with larger thrust, and gradually develop to the second and third ring segment. The uneven thrust forces advance the loading of segment cracks by about 11% under the same thrust. The formation of segment crack damage during shield construction can be reduced by adopting engineering control measures such as strictly controlling uneven thrust of jacks, optimizing segment design and implementing segment control.