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• Influence of joint deflection on the axial mechanical response of pipe jacking. • Distribution of eccentric strain of pipe wall induced by joint deflection. • Development of tensile stress and inelastic stress induced by joint deflection. The bell-and-spigot joints play a vital role in the axial mechanical response of pipe jacking. This paper investigates the influence of joint deflection on the axial stress distribution and jacking load transfer of concrete pipe jacking via full-scale tests and numerical simulation. The joint deflection contributes to the single-side eccentricity or diagonal eccentricity of the pipe segments. The increase in joint deflection influences the extension of axial stress concentration in the vertical direction near the joint, while the increase in jacking load enhances the maximum compressive stress of the pipe wall in the alignment direction. In addition, the nonlinear axial strain–stress property of the cushioning plank among the segments resulted in the nonlinear transfer of the jacking load. Moreover, the joint deflection also induces the visible tensile stress or inelastic stress of the pipe under diagonal loading mode, indicating a risk of structural damage. [ABSTRACT FROM AUTHOR]

• This paper presents a new method for evaluating rock excavation efficiency. • The new method uses the excavated surface to obtain the optimal cutting geometry. • Volumes of underbreaks and overbreaks vs s-p ratio yield a unique turning point. • The turning point represents the optimal cutting geometry of the tested geology. Efficient rock excavation requires an optimal s-p ratio, where adjacent cuts interact to completely plane the rock surface. Traditionally, the specific energy (SE) methodology has been used to determine this ratio, but its U-shaped curve is sometimes incomplete or absent, making it difficult to find the optimal s-p ratio. In this research, an alternative methodology is proposed. This methodology relies on the morphology of the excavated rock surface, specifically, the amounts of overbreaks. To evaluate the proposed methodology, full-scale rock cutting experiments were conducted in the laboratory. Numerical simulations were also conducted in 3D particle flow code (PFC3D) and the results were validated by the full-scale laboratory rock cutting experimental data. The study also involved conducting sensitivity analyses to evaluate the effectiveness of downscaling and upscaling the PFC3D-based model to obtain results for full-scale applications. Following the excavation, laser profilometry was employed to characterize the excavated rock surfaces, and the resulting profiles were used to calculate the volume of overbreaks. Plots of these volumes against the s-p ratio were generated to identify the optimal s-p ratio. The findings indicated the presence of a noticeable optimal s-p ratio in both the PFC3D-based simulations and full-scale laboratory experiments. This optimal s-p ratio was not evident when the specific energy methodology was employed. This proposed methodology exhibits considerable potential and can prove beneficial in determining cutting geometry that is optimal for site-specific and TBM-specific, as well as in the design and production of tunnel boring machines. [ABSTRACT FROM AUTHOR]