Tunneling-induced horizontal strains for buildings with discontinuous foundations are notable and may pose significant risks to the integrity of nearby structures. This paper presents results from a series of numerical models investigating the response of framed buildings on separated footings to tunnel construction in sand. The study examines a two-story, elastic frame with varying building transverse width, eccentricity, and first story height, subjected to tunneling-induced displacements; footing embedment depth and tunnel cover depth are also varied. Results show that tunneling-induced horizontal displacements for separated footings are significant, with greater footing horizontal displacements occurring at deeper footing embedment depths. Building width and eccentricity also influence soil-footing interaction, particularly in determining the values of footing displacements and the distribution of horizontal strains. An increase in footing embedment depth slightly increases shear distortion but significantly increases horizontal strains. The presented modification factors for angular distortion and horizontal strains align well with empirical envelopes, with the horizontal strain modification factor being sensitive to the relative soil-footing stiffness. This research highlights the importance of considering horizontal strains and realistic foundation embedment depth in the damage assessment for buildings with discontinuous foundations due to tunnel construction.

The subject of the current paper is the dynamic behaviour of anisotropic half-plane with surface relief containing a flexible or rigid foundation and two buried lined or unlined tunnels under time-harmonic waves radiated via embedded line source. The aim is to anticipate the influence of different model key factors such as (a) the soil topography; (b) the soil anisotropy; and (c) the soil-tunnels and soil-foundation-tunnels interaction. The computational tool is the direct boundary element method (BEM) based on the frequency-dependent fundamental solution for 2D general anisotropic solid derived by the Radon transform. The lined tunnels are implemented in the numerical model by the sub-structuring approach, which allows an efficient numerical processing of integrals along the interface boundaries. Numerical scheme verification and parametric studies are performed, and respective concluding remarks are summarized. The obtained results clearly illustrate the dynamic response sensitivity to the soil anisotropy, the soil topography and the complex soil-foundation-tunnels interaction.

The presence of underground structures within fault zones has the potential to alter deformation patterns on the ground surface, thereby placing existing structures-typically regarded as safe-at risk. This paper presents findings from four centrifuge model tests and 3D numerical simulations exploring the effects of tunneling in fault zones. This study investigated the values associated with foundation rotation, surface deformations, and the patterns of fault rupture propagation through various soil strata. The results demonstrate that the presence of a tunnel alters the interaction pattern between fault rupture and foundation systems, which can lead to an increase in foundation rotation. Notably, the findings indicate that a precise consideration of superstructure shape can enhance foundation rotation by up to 23%. Furthermore, the presence of a tunnel in the fault zone causes substructures to endure major damage from vertical fault displacements exceeding 0.6 m. In contrast, these substructures experienced similar levels of damage at vertical fault displacements of 1.7 m in the absence of tunnels.

This study analyzed seismic responses of shallow rectangular tunnels within the framework of soil-structure-soil interaction. The idealized soil profile and properties were derived from site-specific investigation reports. Racking curves, typically used in design, were reevaluated to reflect local soil conditions, nonlinear soil behavior, and seismic influences. Results differed significantly from traditional literature findings, emphasizing the importance of localized factors. Finite element methods enabled nonlinear soil parameter modeling and time-history analysis of soil-structure systems. Literature reviews and case studies identified potential damage states with discrete damage levels. The findings quantified probabilities of these damage states and established recurrence relationships for system damages. Fragility curve analyses, widely employed in structural engineering, were used to develop graphical representations of damage probabilities. This study's outcomes provide insights into the seismic behavior of tunnels under localized conditions and enhance reliability in geotechnical and structural engineering designs.

When tunnels in loess traverse sections of alternating soil and rock layers, variations in soil properties can induce an arching effect, potentially leading to the shear failure of the tunnel's structural components. Therefore, seismic design in these areas is particularly crucial. To address these challenges, this paper analyzes the mechanical behavior of damping joints under dynamic earthquake loads using a pseudo-static approach. Based on Bernoulli-Euler beam theory and Pasternak's dual-parameter elastic foundation beam theory, a closed-form solution is derived for the longitudinal response of tunnels in loess with damping joints under seismic loading. The solution is further validated through numerical modeling. Additionally, the study investigates the effects of filling materials (used in damping joints) and design schemes on the effectiveness of damping joints, supported by practical engineering cases. The findings indicate that installing damping joints can reduce the restraining forces on the tunnel lining, allowing the structure to better accommodate the deformation of the surrounding rock. Among the tested materials, rubber was identified as the optimal material for damping joints due to its excellent elasticity and energy absorption capacity. However, the exclusive use of damping joints may result in excessive localized deformation, potentially compromising the tunnel's normal operation. Therefore, careful design of these joints is essential. This research provides theoretical support for the seismic design of tunnels in loess in alternating soil-rock strata.

Deep excavation engineering often causes deformation and destruction of adjacent existing shield tunnels. In previous studies, the influence of deep excavation on tunnel was mainly concentrated on tunnel deformation caused by retaining structure deformation, and the maximum range of the influence zone was approximately 4 times the excavation depth (4He). However, there has been little research on tunnel deformation caused by groundwater drawdown when tunnels are located outside the traditional influence range (4He) of the excavation. In this study, the deformation and damage characteristics of tunnels caused by dewatering in a deep excavation project were analysed using field data, and control methods of tunnel deformation caused by excavation dewatering in leaky aquifers were proposed and discussed. In this project, the maximum settlement reached 8.23 mm for tunnel at the location far than 4He from the excavation, and the influence range of the dewatering on tunnel was nearly 8He. Furthermore, the higher stiffness of the station reduced the settlement and convergence but aggravated the dislocation of the tunnels within approximately 40 m from the station, causing many leakage points. To protect the tunnels, groundwater recharge and deep-shallow-well dewatering scheme (dewatering wells in phreatic aquifer and confined aquifer were set independently) were proposed and applied during subsequent construction, which effectively avoided further tunnel settlement. Groundwater recharge also induced slight uplift and horizontal deformation of the tunnels to the opposite side of the excavation. In addition, recharge should be started in advance and remain in operation until the groundwater level was fully restored. For deep excavations near important infrastructures in soft soil strata with leaky aquifers, the same dewatering and recharge system in this case study is suggested to adopted.

The excavation of the foundation pit impacts the safety, stability, and normal operational functionality of adjacent existing tunnels. With the increasing urban building density, it is becoming more common to conduct foundation pit excavation in close proximity to existing tunnels, which may result in deformation and damage to the tunnels. The impact of foundation pit excavation on adjacent existing tunnels was investigated using a transparent soil scale model and Particle Image Velocimetry technology. The horizontal and vertical distances between the foundation pit and tunnel, as well as the soil consolidation pressure, were individually examined to analyze their respective trends and magnitudes of impact on the maximum vertical deformation of adjacent existing tunnels. The findings suggest that as the excavation depth increases, the deformation of existing tunnels is increasingly impacted by the excavation of foundation pit. However, this impact decreases with greater horizontal or vertical distance between the foundation pit and tunnel. Furthermore, the impact of vertical distance between the tunnel and foundation pit on tunnel deformation is more significant. The pre-consolidation strength of the soil mass significantly impacts the deformation of the existing tunnel. In order to minimize tunnel deformation in practical engineering, constructive recommendations were proposed.

The aim of this study was to solve the problems of low retention rate and poor grouting effect caused by the strong slurry fluidity of traditional cement-based grouting materials in deep backfill strata. Metakaolin-cement-based materials were used as raw materials to examine the dispersion of nano-boron carbide (B4C) using a laser particle size distribution instrument. Nano-B4C was used as a modifier to perform rheological and macroscopic mechanical tests. The effect of nano-B4C dispersion on the performance of the cement-based composite grouting materials was analyzed. The modified materials were further characterized via microscopic tests, and the grouting modification mechanism was revealed. The results showed that the agglomeration of nano-B4C with poor dispersion resulted in an increase in the fluidity of the grouting material, a decrease in viscosity, and a decrease in early strength. The well-dispersed nano-B4C effectively improved the viscosity and early strength of the grouting material and decreased the fluidity, and the change range increased with increasing nano-B4C content. The performance of the modified grouting material was superior to that of the traditional grouting material. The results present new solutions to problems, such as poor grouting effects in deep backfill soil strata.

The demand for tunnels in densely populated urban areas is growing rapidly to address mobility challenges. Mechanized tunneling is widely adopted in urban environments due to its high productivity and the relatively small ground deformations it induces. However, urban tunneling is highly complex because of the typically shallow depths and interactions with aboveground structures. Therefore, accurately predicting ground deformations induced by mechanized tunneling at the design stage is crucial for assessing potential building damage. To investigate these deformations, a series of centrifuge tunnel tests have been conducted at academic institutions such as the Universities of Cambridge and Nottingham to study the behavior of shallow mechanized tunnels in cohesionless soil. These tests serve as excellent benchmarks for numerical model calibration. Once calibrated to replicate centrifuge test results, numerical models can efficiently analyze a wide range of scenarios at a fraction of the time and cost. This paper investigates ground deformations induced by shallow tunneling in cohesionless soil using numerical models calibrated against selected centrifuge tunnel tests, which encompass varying tunnel diameters, depths, and sand relative densities. The numerical modeling results presented in this paper provide extensive insights into tunnel behavior, illustrating how tunnels respond to different relative densities and depths under tunnel volume losses of up to 5%, approaching failure conditions. Additionally, a comprehensive analysis of ground deformations caused by shallow tunnels in sandy soils and their potential impact on buildings is presented.

As urbanization accelerates, the demand for efficient underground infrastructure has grown, with rectangular tunnels gaining prominence due to their enhanced space utilization and construction efficiency. However, ensuring the stability of shallow rectangular tunnel faces in undrained clays presents significant challenges due to complex soil behaviors, including anisotropy and non-homogeneity. This study addresses these challenges by developing a novel failure mechanism within the kinematic approach of limit analysis, integrating soil arching effects alongside anisotropic and non-homogeneous undrained shear strength. The mechanism's analytical solutions are rigorously validated against finite element simulations using PLAXIS 3D and existing models, demonstrating superior accuracy. Key findings show that the proposed model improves predictive performance for critical support pressure, with relative differences as low as 5% for wide rectangular tunnels compared to numerical simulations. Results reveal that limit support pressure decreases with increasing non-homogeneity ratios and rises with higher anisotropy factors. However, both effects diminish in wider tunnels, where increasing width in soils with high non-homogeneity and low anisotropy factors significantly enhances stability. Practical implications of this study are substantial, offering design formulas and dimensionless coefficients for estimating critical face pressures in shallow rectangular tunnels. These tools enable engineers to account for soil anisotropy and non-homogeneity, optimizing design and ensuring safety in urban environments. Furthermore, the proposed model's applicability extends to circular tunnels, where it offers comparable accuracy. This study bridges a critical gap in understanding the stability of rectangular tunnels, providing a robust framework for tackling the challenges of modern urban construction.