Effect of Lubricant Young’s Modulus on Surface Settlement Control During Pipe-Roof Construction Using Pipe-Jacking Method

During pipe-roof construction using pipe-jacking technology, lubricants are injected into the tail void to reduce pipe–soil friction and minimize soil loss. However, research on ground settlement caused by multiple adjacent pipe jackings remains limited, and the influence of lubricant Young’s modulus on ground settlement control is not clear. To address these gaps, this study conducts a comprehensive investigation using a Fast Lagrangian Analysis of Continua in 3 Dimensions (FLAC3D). Initially, the research model is validated against a pipe-roof case in Japan. Subsequently, ground response characteristics are simulated under lubricants with different Young’s moduli, considering four burial depths, two pipe-roof arrangements (“gate-shaped” and “horseshoe-shaped”), and two tail voids. The results indicate that low-stiffness lubricants mobilize greater surface settlement, while increasing the lubricant Young’s modulus more markedly optimizes the interaction among adjacent pipelines, thereby greatly alleviating the settlement. Nonetheless, the control effectiveness of lubricant on the settlement is influenced by other factors. Increasing burial depths and tail voids weaken the lubricant’s capacity to mitigate surface settlement. In contrast, the horseshoe-type arrangement is more conducive to the lubricant’s control effect on surface settlement than the gate-type system. Moreover, under these three cases, an increase in the lubricant Young’s modulus can more substantially reduce surface settlement. These findings provide valuable insights for controlling ground settlement during pipe-roof construction.