This study investigates the deformation characteristics and control measures for existing metro shield tunnels induced by large-section rectangular pipe jacking over-crossing, focusing on the Chengbei Road Comprehensive Utility Corridor project in Suzhou. A 9.1 m × 5.5 m pipe gallery was installed 73.6 m through clay strata over operational subway tunnels, with a minimum clearance of 4.356 m above the tunnel. Finite element simulations and field monitoring were employed to analyze the deformation of the existing tunnels, particularly the effectiveness of anti-uplift counterweights. The results revealed that excavation-induced unloading caused significant tunnel uplift, with maximum vertical displacements of 5.51 mm and 4.95 mm for the down line (DL) and up line (UL) tunnels, respectively. The addition of counterweights reduced these displacements by 30.3% and 37.1%, while also decreasing lateral displacements by up to 61.6% and bending moments by approximately 33%. The study demonstrates that counterweights, combined with slurry lubrication, real-time monitoring, and over-excavation control, effectively mitigate deformation and stress variations during large-section pipe jacking. The successful completion of the project without disrupting subway operations highlights the practical applicability of these measures.

Risk assessment in tunnel construction using the drilling and blasting method presents a complex multi-criteria decision-making challenge due to numerous interacting factors. This study develops an advanced risk assessment model integrating game theory-based combination weighting with nonlinear fuzzy analytic hierarchy process (FAHP). The methodology establishes a comprehensive risk evaluation system through the systematic coupling of a work breakdown structure (WBS) and a risk breakdown structure (RBS), effectively combining subjective weights from an analytic hierarchy process (AHP) with objective weights derived through principal component analysis (PCA). A specialized nonlinear operator addresses the inherent fuzziness in the risk evaluation processes. The model is applied to the Daliangshan No. 1 Tunnel flat guide entrance drilling and blasting construction section, with the risk level determined to be high. Detailed analysis further revealed that the detonation network reliability and ventilation system performance constituted the most significant secondary risk elements. Comparative validation demonstrates the model’s superior accuracy over conventional methods in both weight determination and risk classification. The results demonstrate the effectiveness of the proposed model in improving risk assessment accuracy and supporting decision-making in complex tunnel construction environments.

Laboratory triaxial tests are essential for studying sandy soil behavior but have limited ability to capture localized deformation and microstructural evolution. The discrete element method (DEM) overcomes these limitations by enabling particle-scale analysis, where boundary conditions can critically affect simulation results. This study employed DEM-based triaxial compression simulations to compare rigid wall and flexible membrane boundaries for sand specimens with initial porosities of 35.5%, 38.2%, 40.8%, and 41.5% under confining pressures of 50, 100, and 150 kPa. The analyses covered macroscopic stress–strain and volumetric responses, shear band morphology, local porosity evolution, and contact force fabric. The results indicate that rigid and flexible boundaries produce similar pre-peak responses, but differ markedly in post-peak behavior and volumetric strain. Rigid boundaries constrain lateral deformation, induce stress concentrations, and underestimate post-peak strength, while flexible membranes apply confining pressure more uniformly and reproduce realistic bulging and porosity evolution. Based on these findings, rigid boundaries are suitable for dense sands when post-peak strength is not a concern, and for loose sands at small strains, whereas flexible membranes are necessary to capture volumetric contraction and realistic post-peak responses. This work provides mechanistic insights into boundary effects and offers a basis for more efficient selection of boundary conditions in DEM triaxial simulations.

Reliable prediction of tunnelling-induced ground deformation is essential for assessing differential settlement of surface buildings and deformation of subsurface structures in densely built urban areas. This study establishes a multi-source engineering-evidence framework for parameter selection in the modified Peck model. An interval database containing 39 published correction-coefficient records is compiled to investigate the maximum-settlement correction coefficient α and settlement-trough-width correction coefficient β, while an independent dataset comprising 24 international shield-tunnelling cases and 84 surface and subsurface observations is used to evaluate depth-dependent settlement characteristics. Descriptive statistics, the Mann–Whitney U test, Cliff’s δ, bootstrap resampling, interval Monte Carlo simulation, and case-level trend analysis are employed. The median values α are 0.650 for soft soil and 0.550 for composite strata. Although the difference is not statistically significant (p=0.150,δ=0.302), interval Monte Carlo analysis gives a probability of 0.907 that the median α is higher in soft soil, indicating a directional ground-condition dependence. In contrast, β shows substantial between-group overlap and no robust ground-condition dependence. With increasing normalized observation depth z/T, i(z)/i(0) decreases strongly (ρ=-0.898), whereas S_max(z)/S_max(0) generally increases, with consistent within-case trends in 17/17 and 20/22 cases, respectively. The results support treating α as a ground-conditioned prior and β as an updateable project-specific parameter rather than prescribing either as a fixed constant. The proposed framework provides a transparent basis for settlement assessment of the built environment and highlights the need for depth-dependent corrections when subsurface structures are involved.