This paper introduces an advanced method for calculating the deformation of immersed tunnels when accounting for the impact of repeated siltation loads during maintenance. Based on the insights into the force and deformation characteristics of segmental immersed tunnels, the Timoshenko beam model, which considers bending and shear deformation and is based on the Kerr foundation model (KTM), is used to accurately simulate tunnel-foundation interactions, which simulates the continuity between foundation spring elements and more adequately represents the connection and distinction between the easily compressible soil layer and the less compressible soil layer of the foundation. By its application to the Yongjiang immersed tunnel, this method demonstrates significant improvements in predictive accuracy compared to the two-dimensional settlement (TDM), Euler-Bernoulli (WEM), and Timoshenko model based on the Winkler foundation (WTM). Of note, settlements that result from siltation loads display exponential growth over time, with dredging frequency exerting a discernible influence. These findings have substantial implications for the design and operational management of immersed tunnels, which offer advanced insights to enhance their structural integrity and operational longevity.

The pile foundation construction adjacent to an operational subway tunnel can induce the creep effects of the surrounding soil of the tunnel, resulting in the deformation of the existing tunnel lining and potentially compromising the safe operation of the tunnel. Therefore, the Mindlin solution and the generalized Kelvin viscoelasticity constitutive model were employed to establish the theoretical calculation model for the deformation of the adjacent subway tunnel caused by the pile construction. Then, the effect of pile construction on the deformation of adjacent tunnels under different pile-tunnel spacing was analyzed via three-dimensional numerical simulation and theoretical calculation methods and compared with the field monitoring data. The results showed that the theoretical and numerical data are in agreement with the field monitoring data. The theoretical model provides closer predictions to the field-measured values than the numerical simulation. As the distance between the pile and the tunnel increases, both the vertical settlement and the horizontal displacement of the subway tunnel lining exhibit a gradual reduction. In the hard plastic clay region of Hefei City (China), pile foundation construction near an operational subway tunnel can be classified into three distinct zones based on proximity to the tunnel: the high-impact zone (3.0 D). The pile foundation in high-, moderate-, and low-impact zones should be monitored for 7 days, 3 days, and 1 day, respectively, to ensure the stable deformation of the lining.

Understanding the rheological behavior of marine clay is crucial to analyzing submarine landslides and their impact on marine resource exploitation. Dispersed bubbles in marine clay (gassy clay) and electrolytes in seawater (e.g., NaCl concentration of 0.47 M) significantly impacts rheological properties. Under low ionic strength and low pore water pressure conditions, dispersed bubbles have a strengthening effect on the yield stress and the viscosity of clays. This effect turns into a weakening effect when the pore water pressure reaches 300 kPa or the ionic strength exceeds 0.18 M. It was proposed that the effect of bubbles, whether strengthening or weakening, was determined by the size of bubbles with respect to the characteristic size of the particle structure formed by clay particles. A theoretical model was developed, which reasonably captures rheological behaviors of gassy clays.

The screw conveyor gushing may cause a sudden drop in pressure in the earth chamber, leading to excessive settlement of the surface and nearby buildings or structures, and even catastrophic accidents such as tunnel collapse. This paper presents a comprehensive investigation into slagging failures associated with earth pressure balance shield screw conveyors, categorizing them into rheological failure and permeability failure. Further, a permeability failure theoretical model and a Bingham fluid-based rheological failure model are developed. The above models can describe the conditions and mechanism of screw conveyor spurt taking into account shield parameters, formation characteristics, chamber pressure, and conditioned soil properties. In addition, a sensitivity analysis is conducted on the critical permeability coefficient and critical shear strength of the discharged soil, with a focus on a specific case project. The results underscore the significant impact of the screw conveyor pitch, water head at the entrance, and chamber pressure on the critical permeability coefficient and shear strength. Building on these findings, this paper proposes an anti-surge control index and strategy for shield screw conveyors, taking into account the ratio of shield covering soil thickness to shield diameter. It is recommended that when the shield soil covering layer thickness exceeds twice the shield diameter, real-time modification of the soil parameters, based on the shield tunneling depth, especially the shear strength, is essential for anti-surge control. This study provides engineers with valuable insights into conditioned soil and implements effective surge management strategies for screw conveyors.

Ensuring construction safety and promoting environmental conservation, necessitate the determination of the optimal jacking force for rectangular pipe jacking projects. However, reliance on empirical calculations for estimating jacking force often resulted in overly conservative results. This study proposed a modified Protodyakonov ' s arch model to calculate the soil pressure around the jacked pipe considering the critical damage boundary. A three-dimensional log-spiral prism model, based on limit equilibrium method was applied to analyze the resistance on the shield face. The determination of jacking force integrated factors such as soil pressure around jacked pipes, friction coefficient between pipe and soil, and shield face resistance. By utilizing Suzhou ' s jacking-pipe engineering as a practical context, the accuracy was validated against field monitoring data and existing jacking force calculation models of varying specifications. Parametric analysis indicated the jacking force is linearly correlated with the soil unit weight and pipe-soil friction coefficient. However, the jacking force decreases significantly with increasing internal friction angle. As the internal friction angle rose from 25 degrees to 50 degrees , the soil arch height gradually diminished from 8.91 to 2.59 m. Notably, a complete arch structure failed to form above the jacked pipe when the cover depth ratio was less than 0.5. The heightened predictive precision of the proposed model enhanced its suitability for practical shallow buried tunnel jacking force predictions.

Tunnels subjected to reverse fault dislocation undergo severe structural damage, and their mechanical response and failure characteristics play a key role in seismic fortification efforts. This paper investigates the mechanical responses and failure characteristics exhibited by tunnels subjected to reverse faulting using theoretical analysis and numerical simulations. A theoretical model is established for analysing the bending moment, shear force, and safety factor of the tunnels under reverse fault dislocation. The nonuniform fault displacement, fault zone width, and nonlinear soil-tunnel interaction is applied in the proposed theoretical model, significantly improving the analysis accuracy and range of applicability. The corresponding numerical simulation based on the XFEM (extended finite element method) is carried out, and the proposed theoretical model is verified by the numerical results. The theoretical results demonstrate excellent agreement with the numerical results when nonuniform fault displacement is considered. A parametric analysis is presented in which the effects of the maximum fault displacement, fault zone width, and ratio of the maximum fault displacement of the footwall to the hanging wall are investigated. The results show that the ultimate fault displacement for compression-bending failure of the tunnel subjected to reverse fault dislocation is estimated to be approximately 30 cm, while the ultimate displacement for shear failure stands at 20 cm. Variations in the fault displacement ratio yield alterations in the distribution pattern and peak values of internal forces, together with shifts in the potential failure ranges of the footwall and hanging wall. Additionally, an initial crack emerged on the tunnel crown near the fault plane, followed by a second crack on the tunnel invert. Upon reaching a fault displacement of approximately 40 cm, the crack fully traverses the entire tunnel lining.