The time-dependent interfacial adhesion between rock and fresh mortar is key for printing concrete linings in mountain tunnels. However, a scientific deficit exists in the time-dependent evolution of the interfacial adhesion, which can cause adhesion failure when printing tunnel lining. Nanoclay has the potential to increase the interfacial adhesion and eliminate the adhesion failure. Before the actual printing of tunnel linings, the time-dependent interfacial adhesion between artificial rock and fresh mortar modified by nanoclay should be understood. This paper studied the time-dependent interfacial adhesion based on fast tack tests, fast shear tests, and isothermal calorimetry tests. With the addition of nanoclay, the maximum tensile stress and the maximum shear stress increased. Compared with a reference series, the maximum interfacial tensile stress in a 0.3% nanoclay series increased by 106% (resting time 1 min) and increased by 209% (resting time 32 min). A two-stage evolution of the interfacial adhesion was found with the addition of nanoclay. In the first stage, the time-dependent interfacial adhesion increased rapidly. A 0.3% NC series showed an increase rate six times higher than that of the reference series. As the matrices aged, the increase rate slowed down and followed a linear pattern of increase, still higher than that of the reference series. The stiffening of fresh matrices resulted in the interface failure mode transition from a ductile failure to a brittle failure. The effect of nanoclay on flocculation and on accelerating the hydration contributed to the time-dependent interfacial adhesion between artificial rock and fresh mortar.

A large number of experimental studies have demonstrated that the permeability and damage of rock are not constant but rather functionally dependent on stresses or stress-induced deformation. Neglecting the influence of damage and permeability evolution on rock mechanics and sealing properties can result in an overestimation of the safety and stability of underground engineering, leading to an incomplete assessment of the risks associated with surrounding rock failure. To address this, the damage and permeability evolution functions of rock under compression were derived through a combination of experimental results and theoretical analysis, unifying the relationship between porosity and permeability in both porous media flow and fractured flow. Based on this, a fluid–solid coupled seepage model considering rock damage and permeability evolution was proposed. More importantly, this model was utilized to investigate the behavior of deformation, damage, and permeability, as well as their coupled effects. The model’s validity was verified by comparing its numerical results with experimental data. The analysis results show that the evolution of permeability and porosity resulted from a competitive interaction between effective mean stress and stress-induced damage. When the effective mean stress was dominant, the permeability tended to decrease; otherwise, it followed an increasing trend. The damage evolution was primarily related to stress- and pressure-induced crack growth and irreversible deformation. Additionally, the influence of the seepage pressure on the strength, damage, and permeability of the investigated rock was evaluated. The model results reveal the damage and permeability evolution of the rock under compression, which has a certain guiding significance for the stability and safety analysis of rock in underground engineering.

This paper presents an analytical solution for near-field cylindrical P-wave scattering by a circular tunnel. A comprehensive elastic–slip interface model is incorporated to capture localized discontinuous deformations and frictional sliding. Employing the wave function expansion method and Graf’s addition theorem, the dynamic stress concentration factor (DSCF) of both soft and stiff linings is systematically investigated. The results reveal that near-field wavefront curvature severely amplifies stress concentration on the illuminated side, degenerating into a plane-wave response only when the dimensionless source distance exceeds 50. Furthermore, within the parameter range considered, the imperfect interface exhibits a dual “flexible barrier” effect heavily influenced by impedance matching: it tends to act as a seismic isolator that reduces the DSCF for stiff linings, but can weaken boundary confinement and exacerbate stress concentration for soft linings. These findings provide crucial theoretical insights for the blast-resistant design of underground structures.

To meet the demand for simulative materials exhibiting suitable hydraulic characteristics in geomechanical model tests, this research developed a type of simulative material using iron powder, quartz sand, and barite powder as aggregates, white cement as binder, and silicone oil as additive. An orthogonal experimental design L₁₆(4⁴) was employed to prepare 16 distinct mix proportions. Advanced statistical methods, including range analysis, residual analysis, Pearson correlation analysis, and multiple regression performed with SPSS 27.0.1, were applied to analyze the influence of four factors—aggregate-to-cement ratio (A), water–cement ratio (B), silicone oil content (C), and moisture content (D)—on physical and mechanical parameters such as density, uniaxial compressive strength, elastic modulus, angle of internal friction, and permeability coefficient. Range analysis results indicate that the aggregate-to-cement ratio serves as the primary controlling factor for density and elastic modulus; moisture content exerts the most significant effect on compressive strength and permeability; while the water–cement ratio is the dominant factor influencing the internal friction angle. Empirical formulas were established through multiple regression to quantitatively correlate mix proportions with material properties. The resulting similitude materials cover a wide range of mechanical and hydraulic parameters, satisfying the requirements of large-scale physical modeling with high similitude ratios. The proposed equations allow efficient inverse design of mixture ratios based on target properties, thereby supporting the rapid preparation of simulative materials for advanced model testing.

This study presents an analytical elastic solution using the complex variable approach to determine the soil disturbance surrounding a shallow rectangular tunnel, taking into account the effect of gravity and considering the influence of grouting pressure applied at the tunnel boundary. A theoretical calculation model is first established by applying stress boundary conditions along the tunnel boundary. To handle the geometric complexity of the rectangular cavity, a conformal mapping function suitable for non-circular opening is adopted. This function maps the original half-infinite region with a rectangular cavity onto an annulus in the transformed plane, thereby converting the irregular cavity problem into a more tractable configuration. The boundary conditions at the ground surface and the tunnel interface are then addressed using Fourier series expansion. By solving these series-expanded equations, all unknown coefficients of the analytical functions are determined, leading to an analytical elastic solution for soil disturbance. Numerical verification validates the accuracy of the proposed approach. Moreover, parametric studies are conducted to evaluate the effects of soil mechanical properties and tunnel geometry on the soil disturbance. The findings offer a valuable reference for future investigations into construction-related issues associated with rectangular tunnels.

Grounded in the principles of wave dynamics, this study employs the wave function expansion approach to mathematically describe how plane P- and SV-waves scatter around a composite tunnel lining embedded in an unbounded medium. To establish the transient analytical framework for the dual-layer structure subjected to blast excitations, we integrate Fourier integral transforms alongside the Heaviside step and Dirac delta functions. We systematically analyze how the tunnel’s transient dynamic stress concentration factor (DSCF) responds to variations in the shear modulus ratio, as well as the specific characteristics of the incoming waves (i.e., wave type and dimensionless pulse duration). Furthermore, a seismic mitigation strategy featuring a “soft-exterior, rigid-interior” configuration is theoretically explored. The analytical outcomes theoretically indicate that short-duration transient waves provoke severe dynamic stress concentrations within the lining, with SV-waves posing a markedly greater threat to structural integrity than P-waves. Analyses reveal that the peak dynamic stress concentration (DSCFmax) primarily localizes at the tunnel’s crown and invert. Interestingly, altering the pulse duration does not significantly shift this spatial distribution pattern. Ultimately, analytical results suggest that adopting the “soft-exterior, rigid-interior” design and optimizing the thickness of the primary support can substantially alleviate these stress concentrations, providing preliminary theoretical guidance for vibration attenuation.