By: Weihua Liu, Li Luo, Yangyu Zhang, Feng Wang, Qi Chen, Shuang Huang
As the structurally weaker component of a pipe-jacking system, the bell and spigot joint is subjected to considerable axial jacking forces during construction and is prone to damage once an offset occurs. In this study, a three-dimensional refined numerical model was developed based on the Wuhan Road pipe-jacking project. First, the influence of offset on the stress distribution of the pipe joint during jacking operations was investigated in detail, followed by an analysis of the effect of different jacking force magnitudes on the joint stress. Finally, recommended control limits for joint offsets under different jacking forces were proposed. The results indicate that, when a downward offset occurs between pipes, the compressive stresses at the bell crown and spigot invert become significantly higher than those in other regions, and the stress at the crown of the steel ring also increases markedly. When the offset is below 5 mm, the increase in joint stress remains relatively small; however, once the offset exceeds 5 mm, both the concrete stress and the von Mises stress in the steel ring begins to increase rapidly. Under offset conditions, increasing the jacking force markedly amplifies the stress in the joint concrete but exerts minimal influence on the stress in the steel ring. At an offset of 25 mm, the maximum compressive stress in the bell concrete under an 8000 kN jacking force reaches 32.90 MPa, approaching the concrete's compressive strength. When the offset further increases to 30 mm, compressive failure of the joint concrete occurs under all jacking forces in the range of 4000–8000 kN. Therefore, it is recommended that the offset be limited to no more than 25 mm for jacking forces of 4000–6000 kN, and no more than 20 mm for jacking forces of 6000–8000 kN, in order to ensure construction safety.
