In response to the frequent water and sand leakage disasters caused by water-rich sandy strata in foundation pit engineering, this study utilizes a discrete-element method (DEM)-computational fluid dynamics (CFD) coupling simulation method based on a leakage incident in a deep foundation pit of Hangzhou Metro. The study investigates the deformation behavior of the stratum caused by foundation pit leakage and sand loss and proposes an empirical formula for predicting surface settlement. The results show that, first, compared to the no-flow condition, the slip region of soil particles develops more rapidly under seepage conditions, and its final extent is larger. Second, following soil particle loss, deep-layer displacement isovalues form elliptical surfaces of varying sizes. The effect of different water and sand leakage conditions on the extent of soil deformation is relatively minor. The two short semiaxes of the loosening ellipsoid are b = 0.69-0.77H and c = 0.6-0.68H. Furthermore, both water and sand leakage conditions, as well as sand loss-only conditions, exhibit a settlement trough in the surface settlement curves. At the same time step, the maximum surface settlement value Smax under water and sand leakage conditions is approximately 2-4 times that under sand-only leakage conditions. In addition, the surface settlement curve is fitted based on the Peck formula, and a simplified two-dimensional theoretical model is proposed. This model is then extended into three-dimensional space, resulting in an empirical formula that can effectively predict surface settlement. The theoretical value of the soil loss volume calculated using the formula shows a relative error of 6.5% compared to the actual value. The findings provide crucial theoretical guidance for emergency responses to water and sand leakage in foundation pits and for subsequent soil backfilling and layer compensation grouting.

PurposeThis study aims to investigate the axial force coherence phenomenon in servo steel struts used in deep foundation pits, where changes in the axial force of one strut affect adjacent struts. The research seeks to quantify the axial force loss in neighboring struts due to such coherence and propose predictive models to support better engineering control strategies.Design/methodology/approachModel tests were conducted to analyze the axial force changes in servo steel struts under various loading conditions. Numerical simulations were then performed to validate the experimental results. The influence of strut spacing and initial axial force on coherence effects was examined, and an empirical formula for axial force loss rate was derived.FindingsThe axial force in struts increases with excavation depth, with the growth rate accelerating deeper down. Loading a single strut causes axial force loss in adjacent struts, negatively correlated with distance and positively correlated with initial axial force. The loss rate decays exponentially with horizontal distance. Synchronous loading of nearby high-force struts is recommended to mitigate coherence-induced losses.Originality/valueThis study provides the first comprehensive model test and numerical analysis of axial force coherence in servo steel struts, considering both vertical and horizontal interactions. It introduces an original empirical formula that quantifies axial force loss as an exponential function of horizontal distance and initial strut force. The findings offer practical value by proposing a synchronous loading strategy to compensate for coherence-induced force loss, enhancing the safety and precision of support systems in deep excavation projects.

To control the deformation of adjacent tunnels caused by foundation pit excavation, a combined active control approach using servo steel struts and capsule grouting (hereafter referred to as grouting for brevity) was investigated for its control mechanism on tunnel and diaphragm wall deformation. Model tests were performed to analyze how grouting parameters (grouting pressure, grouting length, grouting diameter, clear distance to the tunnel, and central burial depth of grouting) affect the stress and deformation of tunnels and diaphragm walls under the same servo steel strut conditions. Numerical simulations were further carried out to investigate the influence of the length-to-diameter (L/D) ratio of the grouting body on the deformation of both structures. The results show that grouting can effectively reduce the horizontal displacement and convergence of the tunnel but will exacerbate tunnel settlement. In the model test, grouting increases the deformation of the diaphragm wall, and the grouting-induced incremental deformation reaches its maximum at the pit bottom. The right haunch of the tunnel is the most affected position by grouting, with a deformation magnitude far greater than that of other sections. The horizontal displacement of the tunnel is most sensitive to changes in grouting diameter, while the deformation of the diaphragm wall is most sensitive to changes in the clear distance to the tunnel, and the impact of grouting pressure on the deformation of both is the smallest. Under the same total grouting volume, the length-to-diameter ratio of the grouting body shows an increasing-then-decreasing trend for both diaphragm wall deformation and tunnel deformation, with both reaching their peak values simultaneously. Considering the control of tunnel deformation and diaphragm wall deformation, a Length-to-Diameter ratio slightly larger than the peak value is recommended as the preferred shape for the grouting body.

To investigate the influence of groundwater on the dynamic response of heavy-haul railway tunnel structures, a self-developed three-dimensional (3D) dynamic testing apparatus was utilized to conduct laboratory-scale model tests. Swept-frequency vibration loads and train vibration loads were applied. The Frequency Response Function (FRF) and coherence coefficient were introduced to validate the reliability of the test results. By combining time-domain and frequency-domain analysis methods, the dynamic response characteristics of the tunnel structure under water-free and saturated strata conditions were studied. The results indicate that the average coherence coefficient reached 0.85 in the 50 similar to 100 Hz frequency band and approached 1 when the frequency exceeded 100 Hz, confirming the reliability of the test results. The acceleration response of the tunnel structure exhibited periodicity; its peak value increased with the train axle load and decayed exponentially with increasing distance from the vibration source. In the time domain, the presence of groundwater increased the system damping, resulting in a significantly lower acceleration response of the tunnel structure in the saturated stratum compared to the water-free stratum. The peak acceleration in the saturated stratum was attenuated by approximately 40.1%similar to 41.1% compared to that in the water-free stratum, demonstrating the buffering, energy absorption, and water pressure effects of the water body. In the frequency domain, the structural dynamic response exhibited a fluctuating upward trend with increasing frequency, and the response amplitude in the saturated stratum was notably lower than that in the water-free stratum. Specifically, the acceleration level at the tunnel measurement points in the water-free stratum was on average 7.55 similar to 9.49 dB higher than that in the saturated stratum, indicating that groundwater significantly increases system damping and accelerates the dissipation of vibration energy.

The clogging-column effect severely impedes the efficiency of vacuum preloading with prefabricated vertical drains (PVDs) in treating ultra-soft dredged slurries. Existing equivalent smear-based models are useful for overall prediction, but they generally do not explicity distinguish the different physical processes involved in clogging development. In this study, a large-strain radial vertical consolidation model is developed in which the clogging effect is represented by two components: (1) permeability deterioration associated with soil fabric reorganization, described by the parameter α, and (2) rapid local densification near the drain under high hydraulic gradients, described by the parameter η. The model also considers time-dependent decay of drain discharge capacity through β, together with spatially varying radial permeability. An implicit finite difference scheme is used to solve the governing equations. Parametric analyses indicate that η mainly affects the early stage development of clogging, α is more closely related to the long-term low-permeability state, and β mainly influences drainage efficiency during the middle and late stages of consolidation. Comparison with a field case in Wenzhou, China shows that the proposed model gives reasonable agreement with the measured settlement. For the case considered, the MAE and RMSE are reduced by 15.5% and 18.5%, respectively, relative to an existing large-strain solution with time-dependent well resistance, while the coefficient of determination R 2 increases from 0.881 to 0.921. The proposed formulation may provide a useful basis for interpreting clogging affected vacuum consolidation of dredged slurry.

Frictional energy piles are a more desirable form of shallow geothermal energy utilization. A pure friction pile condition cannot be achieved in field tests. In this study, foam was placed beneath the model pile tip to weaken the end-bearing resistance. The effects of different cyclic temperature patterns (including cyclic path, external load, and variable temperature duration) on the bearing characteristics of pure friction energy piles are investigated by conducting model tests in a self-designed model box, and the variation patterns of pile stress–strain and pile-top displacement are measured. The results show the following: (1) Under no load, the displacement of the pile top changes with temperature; each round of temperature change produces a partial irrecoverable displacement, and the pile maintains a raised state at the end of both rounds with no stress accumulation. (2) Under the combined action of working load and cyclic temperature, the pile strain reaches its peak and then partially rebounds. Thermal stress accumulates progressively with increasing cycle numbers, and after the cycling ends, an irrecoverable settlement displacement (0.52% D) remains at the pile top and continues to increase. (3) The temperature cycle caused the soil volume to shrink and decreased the shear strength of the pile–soil interface, resulting in a decrease in the ultimate bearing capacity of the test pile compared to the initial state.

Landfills are commonly employed for the disposal of solid waste; however, they pose a significant risk of groundwater contamination due to leachate. To address this concern, traditional impermeable systems composed of bentonite-sand composites are employed as liners at the base of landfills. This study investigates an alternative impermeable system featuring a composite material made from quarry stone chips and bentonite aimed at enhancing leachate containment. The primary objective is to assess the effects of varying bentonite dosage and various dry densities on the permeability performance of the stone chips-bentonite mixture. GDS permeation tests are conducted to assess the permeability performance of the soil mixture comprising stone chips and bentonite. Various dosages of bentonite (ranging from 3

To evaluate the coupled deformation of existing shield tunnels induced by multi-segment excavations with isolation piles, this study develops an integrated analytical framework combining a Kerr three-parameter foundation-plate model with a three-dimensional image-source solution. A closed-form expression for the soil displacement field is first derived by incorporating layered soil conditions, staged excavation, and associated spatial effects. The soil-pile interaction of isolation piles is then modeled using the Kerr foundation, and the flexural response is obtained through variational formulation and finite-difference discretization. These responses are sequentially propagated through the excavation stages, enabling the superposition of multi-pit effects on the final retaining-wall deformation. The image-source method and a volume-equivalent transformation are further used to convert wall deformation into an additional stress field acting on the tunnel, which is ultimately coupled with a tunnel-soil deformation-coordination model to compute horizontal tunnel displacements. This unified workflow establishes a continuous mechanical transfer chain-from excavation-induced soil loss to isolation-pile bending and finally tunnel deformation. Parametric analyses show that lateral displacement of the retaining structure is jointly governed by wall bending and pit-bottom uplift, producing a right-skewed "S-shaped" profile. The bending-moment peak shifts toward earlier-excavated zones, indicating a memory effect of excavation sequencing. Two engineering cases verify that the proposed method accurately reproduces the magnitude and depth of measured wall deflections, while predicted tunnel displacements show a near-Gaussian pattern with high accuracy near the peak. The analytical framework provides a robust theoretical basis for optimizing pit segmentation and excavation sequencing adjacent to shield tunnels.

Theoretical research is conducted on the soil deformation caused by the construction of overlapping tunnels under composite geological conditions.Based on the theoretical method of combining analogous considering the shielding effect of the stochastic medium theory and the three-dimensional unified solution,a computational model was established considering the shielding effect of the underground tunnel on the deformation of the upper tunnel is taken into account.The calculation formula for soil deformation was derived.The theoretical method in this article was applied to multiple sets of measured cases for verification.Research indicates that:The calculation results have a good degree of fit,proving the feasibility of this method.Through single factor analysis,it is found that the soil conditions near the upper tunnel in overlapping tunnels have a significant impact on the deformation of surface soil.Compared to single line construction,the soil deformation caused by the upper tunnel in the overlapping tunnel from bottom to top is shallower and narrower due to the influence of the lower line shielding effect.The shielding effect coefficient proposed in this article can better reflect the influence of the lower line tunnel on the soil deformation of the upper tunnel.The magnitude of the shielding effect coefficient is inversely proportional to the distance between the tunnel axes,and the smaller the tunnel spacing,the greater the shielding effect coefficient.

The deep foundation pit excavation of subway will cause horizontal displacement, uneven settlement and other adverse effects on the adjacent shield. The use of servo steel strut has a certain effect on deflection correction, but the current understanding of the influencing factors of deflection correction is not comprehensive. Based on structural and spatial symmetry, the influence of tunnel depth, tunnel and foundation pit clear distance and deformation control quantity of enclosure structure on deflection correction quantity was studied by symmetrically designed model test and numerical simulation, and the prediction formula of deflection correction quantity considering tunnel and foundation pit clear distance and deformation control quantity of enclosure structure was proposed. The results show that with an increase in the tunnel's burial depth, deflection correction decreases significantly. When the tunnel is near the foundation pit bottom, there is no significant correction effect, and the control law of the tunnel ground pressure under the servo steel strut loading is consistent with the correction law. Deflection correction is negatively correlated with the tunnel and foundation pit clear distance, and positively correlated with the deformation control of the diaphragm wall. The curve of the deformation control of the enclosure structure and the deflection correction is parabolic. The deflection correction is an exponential function of the ratio of the deformation control of the enclosure structure to the clear distance between the tunnel and the foundation pit, and the servo deflection correction follows a normal distribution along the longitudinal axis of the tunnel, showing obvious symmetry characteristics in the foundation pit influence zone.

This study investigates staged surcharge preloading at a coastal test section by integrating field monitoring (pore-water pressure, settlement/settlement rate, and layer-by-layer deformation) with laboratory consolidation tests and field vane shear measurements. Responses at the surcharge center and slope-toe margin are compared to quantify spatial non-uniformity and pore-pressure-deformation coupling. Pronounced heterogeneity is observed (this field response represents three-dimensional deformation behavior that cannot be reproduced by 1D consolidation tests), with an empirical transition depth of similar to 24 m for this Wenzhou coastal soft soil site: above this depth, strains concentrate near the margin, whereas below it, compression at the center becomes dominant. The pore-pressure-settlement relationship is stage-dependent: during loading, pore pressure fluctuates markedly and settlement lags; during maintained consolidation, pore pressure dissipates, effective stress develops, and settlement is governed mainly by consolidation compression. After surcharging, water content decreases, and soil sensitivity reduces from 4.0 to 3.0 and stabilizes, indicating post-disturbance structural re-stabilization. These findings inform surcharge scheme design, monitoring layouts, and subsequent model calibration.

PurposeThis study aims to develop an analytical framework for evaluating longitudinal deformation of shield tunnels subjected to discrete surface loads, explicitly incorporating the stiffness effect of pavement-hardened layers. The model introduces a synergistic deformation mechanism that couples segmental rotation and misalignment, enabling more accurate prediction compared to traditional continuous-load assumptions. Validation through PLAXIS 3D simulations and field monitoring demonstrates its reliability. The framework provides practical guidance for optimizing temporary support layouts and controlling tunnel deformation during surface construction, ensuring the structural safety and serviceability of shield tunnels in complex urban environments.Design/methodology/approachAn analytical model was developed to evaluate shield tunnel deformation under discrete surface loads, incorporating the stiffness equivalence of pavement-hardened layers. The model integrates a synergistic mechanism coupling segmental rotation and misalignment, formulated using enhanced elasticity theory for granular soils and solved via a Fourier-series-based variational method. PLAXIS 3D finite element simulations were conducted to replicate staged construction loading and validate model predictions. Field monitoring data from a metro tunnel in Ningbo, China, were used for comparison, confirming the model's accuracy and practical applicability in optimizing temporary support layouts for tunnel deformation control.FindingsThe proposed model accurately predicts shield tunnel deformation under discrete surface loads, with displacement errors within 7% compared to field measurements. Considering the pavement-hardened layer reduces predicted tunnel displacement by up to 52% and decreases misalignment, rotation, and shear forces by about 30%. Temporary support layout significantly influences deformation patterns; optimized arrangements yield more uniform and reduced displacements. The relationship between surface surcharge and tunnel deformation is nearly linear within typical load ranges, with excessive concentrated loads quickly exceeding settlement warning thresholds. The model offers a practical basis for safe construction planning above operational shield tunnels.Research limitations/implicationsThe proposed model assumes linear elastic soil behavior and does not account for complex nonlinear, dynamic, or time-dependent effects such as creep and long-term consolidation. The hardened layer is represented through stiffness equivalence, neglecting potential cracking or degradation under repeated loading. Validation is based on one metro tunnel case, which may limit direct applicability to other geologies or structural configurations. Future research should extend the framework to incorporate nonlinear soil constitutive models, dynamic load scenarios, and broader field datasets to enhance predictive capability and applicability in more diverse urban tunneling environments.Practical implicationsThe developed analytical framework provides a practical tool for assessing shield tunnel performance under discrete surface loads in urban construction. Incorporating the stiffness effect of pavement-hardened layers, it enables more accurate deformation prediction, avoiding overly conservative designs. Engineers can use the model to determine allowable surface surcharge limits, optimize temporary support layouts, and minimize adverse impacts on operational tunnels. This approach supports safer construction planning, reduces maintenance risks, and ensures serviceability of existing tunnel infrastructure, offering a reliable basis for decision-making in projects involving heavy surface equipment or temporary structural supports.Social implicationsAccurate prediction and control of tunnel deformation under surface construction loads enhance the safety and reliability of urban transportation networks. By preventing excessive settlement and structural damage, the proposed approach helps avoid service interruptions, costly repairs, and potential safety hazards to the public. Optimizing temporary support layouts reduces environmental disturbance and minimizes disruption to surface traffic during construction. The method supports sustainable urban development by enabling efficient use of existing underground infrastructure while accommodating aboveground construction demands, contributing to safer cities and improved public confidence in large-scale infrastructure projects.Originality/valueThis study introduces an analytical framework that, for the first time, couples the effects of discrete surface loads with the stiffness contribution of pavement-hardened layers in predicting shield tunnel deformation. A synergistic deformation mechanism is proposed to simultaneously account for segmental rotation and misalignment, improving physical realism over conventional continuous-load models. The model is formulated using enhanced elasticity theory for granular soils and validated through PLAXIS 3D simulations and field monitoring. It offers a practical, validated tool for optimizing construction load arrangements above operational tunnels, addressing a critical gap in urban tunneling deformation prediction and safety assessment.

This study investigates the abnormal horizontal displacement response of existing tunnels adjacent to a deep excavation under non-uniform dewatering and partitioned excavation. A field case from Hangzhou, China, involving an operating metro tunnel and the Jiangnan Avenue underground tunnel, is presented. Field monitoring data and an interim lining-condition survey were used to examine groundwater-level variation outside the excavation, retaining-wall displacement, soil movement, tunnel deformation, and lining service condition. The results show that, despite the use of cut-off walls, partitioned excavation, internal dewatering, and servo-controlled struts, the maximum cumulative horizontal displacement of the downline metro tunnel reached approximately 6.2 mm, exceeding the control value of 5.0 mm, whereas track-bed settlement and horizontal convergence remained within the control limits. The abnormal response was therefore mainly manifested as overall horizontal tunnel displacement. The monitoring results further indicate that tunnel displacement was not governed solely by retaining-wall deformation, but was more closely associated with the non-uniform groundwater response and the overall movement of deep soil outside the excavation. Hydraulic head differences, pore-pressure dissipation, and effective stress changes may have promoted soil movement toward the excavation, thereby contributing to tunnel movement toward the excavation even when the local retaining wall moved in the opposite direction. The lining-condition survey showed increased wet traces, cracks, and joint dislocation, indicating that displacement exceedance was accompanied by local serviceability deterioration. The findings provide implications for deformation control and risk identification of operating rail transit tunnels subjected to adjacent excavation and dewatering.

Monitoring deformation in foundation pit enclosure structures is crucial, serving as the foundation for predicting deformations, issuing early warnings for exceedances, and implementing effective control measures. However, the collected monitoring data often contain noise, necessitating robust denoising techniques to ensure accuracy. Existing denoising methods for foundation pit monitoring data often struggle to effectively remove noise while preserving key features. To address these challenges, a novel method based on Wavelet transform (WT) and DenseNet-Attention (DANet) is proposed for denoising deformation data of foundation pit enclosure structures, complemented by a spatiotemporal adaptive fusion network (STAF) to optimize the results further. Initially, Wavelet transform is applied to decompose the deformation data across spatial and temporal dimensions at multiple scales, extracting detailed and approximation components at varying frequency levels. Subsequently, DANet is employed to denoise and reconstruct these decomposed components, yielding denoised data in both spatial and temporal dimensions. Finally, the spatiotemporal adaptive fusion network integrates the denoised outputs from spatial and temporal dimensions to generate high-quality results. The effectiveness of the proposed method is validated through experiments using data from a road improvement project in southern China. Comparisons with mainstream denoising techniques and evaluations via multiple metrics demonstrate the superior performance of the proposed approach in noise reduction.

Coal pillars are critical supporting structures between underground coal gasification gasifiers.Its bearing capacity and structural stability are severely threatened by high-temperature environments.To elucidate the high-temperature deterioration mechanism of coal pillars at multiple scales,coal strength features as a function of temperature were investigated via uniaxial compression and acoustic emission equipment.The pyrolysis reaction process and microstructure evolution were characterized via X-ray diffractometer（XRD）,scanning electron microscope （SEM）,thermogravimetric （TG）,Fourier transform infrared spectroscopy （FTIR）,and computed tomography （CT） tests.Experimental results reveal a critical temperature threshold of 500℃ for severe degradation of the coal bearing capacity.Specifically,both the strength and elastic modulus exhibit accelerated degradation above this temperature,with maximum reductions of 45.53% and 61.34%,respectively.Above 500℃,coal essentially undergoes a pyrolysis reaction under N 2 and CO 2 at mospheres.High temperatures decrease the quantity of O 2 -based functional groups,growing aromaticity and the degree of graphitization.These changes induce dislocation and slip inside the coal crystal nucleus and then lead to deformation of the coal molecular structural units and strain energy generation.This process results in a great increase in porosity.Consequently,the stress deformation of coal increases,transforming the type of failure from brittle to ductile failure.These findings are expected to provide scientific support for UCG rock strata control.

In deep foundation pit engineering, the rational arrangement of internal struts plays a crucial role in controlling diaphragm wall displacement and minimizing environmental impacts. This study investigates the effects of servo steel struts through model tests, analyzing diaphragm wall displacement, bending moment, surface settlement, and surrounding soil pressure during both excavation and active servo control phases. The results show that installing servo struts near the pit bottom significantly improves deformation control, whereas strut placement in shallow zones more effectively mitigates surface settlement. The servo system dynamically adjusts strut displacements, thereby inducing internal force redistribution in the diaphragm wall and modifying the stress field in surrounding soils. This mechanism leads to an increase in positive bending moments on the wall’s backside, which may necessitate the localized reinforcement of the diaphragm wall at servo strut connections to ensure structural integrity. The lateral wall and surrounding soil pressure exhibit further increase, effectively compensating for the pressure loss induced by excavation unloading. Notably, the influence on soil pressure demonstrates a dissipating trend with an increasing distance from the excavation.

To address the issue of inaccurate tunnel segmentation caused by solely relying on point cloud coordinates, this paper proposes two algorithms, GuSAC and TMatch, along with a ring-based cross-section extraction method to achieve high-precision tunnel lining segmentation and cross-section extraction. GuSAC, based on the RANSAC algorithm, introduces a minimum spanning tree to reconstruct the topological structure of the tunnel design axis. By using a sliding window, it effectively distinguishes between curved and straight sections of long tunnels while removing non-tunnel structural point clouds with normal vectors, thereby enhancing the lining boundary features and significantly improving the automation level of tunnel processing. At the same time, the TMatch algorithm, which combines cluster analysis and Gaussian Mixture Models (GMMs), achieves accurate segmentation of tunnel rings and inner ring areas and further determines the tunnel cross-section position based on this segmentation result to complete the cross-section extraction. Experimental results show that the proposed method achieves a segmentation accuracy of up to 95% on a standard tunnel point cloud dataset. Compared with traditional centerline extraction methods, the proposed cross-section extraction method does not require complex parameter settings, provides more stable positioning, and demonstrates high practicality and robustness.

Synchronous grouting slurry is widely used in shield tunnel construction to fill the gaps between stratum and shield tail segments. However, as grout is nearly liquid in the initial stages, the tunnel lining segments recently separated from the shield tail are easily affected by the upward buoyancy generated by grout, causing issues such as longitudinal misalignment and opening of ring joints. Therefore, studying the upward buoyancy characteristics of synchronous grout is crucial. In this study, floating characterisation parameters of grout were investigated using buoyancy model tests, orthogonal tests, and comprehensive tests. The floating characterisation parameters are affected by distribution ratio and types of each grout component. The relationship between the floating characterisation parameters of grout and buoyancy was established. The results show that density, flow index, and shear strength can be used as the floating characterisation parameters. Binder–sand and water–binder ratios have the largest impact on the density. The bentonite–water ratio exerts a primary influence on the flow index, while the water–binder ratio contributes a secondary effect. In addition, bentonite–water and binder–sand ratios have the greatest effect on the shear strength. Furthermore, the particle size of sand and type of bentonite considerably influence the flow index and shear strength. A high-shear grout using well-graded fine sand and a high mesh of sodium bentonite was considered in this study. When the content of bentonite exceeds 7% (P2.2), Archimedes’ law is not applicable for calculating the upward buoyancy of grout. Buoyancy supply rate exhibits gradual enhancement with flow index elevation, yet with diminishing growth rates.

The unloading effect induced by foundation pit excavation leads to soil deformation, which may adversely affect the underlying tunnel. Foundation pit excavation is a three-dimensional (3D) deformation process, whereas most existing methods are based on a two-dimensional (2D) plane assumption. To improve conventional 2D analysis methods, this study considers the influence of the actual construction sequence on tunnel deformation. A 3D analytical method for evaluating tunnel deformation and stress induced by foundation pit excavation is proposed, based on the image source method and the rotational dislocation-coordinated deformation model. The proposed method is validated through comparative analysis with other methods using monitoring data from three engineering cases. Furthermore, the study examines and discusses the impact of excavation sequences on the final longitudinal displacement of the tunnel. The results indicate that the proposed method provides more accurate predictions of tunnel deformation induced by foundation pit excavation in actual projects. Staged and segmented excavation reduces bottom heave of the foundation pit, thereby mitigating its impact on the underlying tunnel. When the segmentation efficiency is positive, increasing the number of excavation blocks contributes to better tunnel deformation control. However, when the segmentation efficiency is negative, an increase in excavation blocks has an insignificant effect on deformation control or leads to excessive construction workload.

With the rapid development of underground space utilization in China, urban tunnels and subsurface structures have formed complex "metro domains." Ensuring the safety and stability of existing structures during construction is a critical challenge. This study investigates the impact of open-cut tunnel excavation on existing metro tunnels, using the foundation pit project above Hangzhou Metro Lines 1 and 3 as a case study. Field monitoring was conducted to analyze the deformation response of the metro tunnel, and a predictive model was established. Additionally, numerical simulations using MIDAS GTS NX were performed to evaluate the effects of various reinforcement techniques. The effectiveness of the MJS (Mixing and Jetting System) reinforcement method combined with high-pressure jet grouting piles was verified. The findings indicate that: (1) The maximum tunnel uplift, horizontal displacement, convergence deformation, and differential settlement induced by excavation reached 8.5, 5.4, 4.6, and 2.8 mm, respectively, with deformation primarily concentrated in the middle section of the excavation area. (2) The numerical results closely matched the field monitoring data. Compared to high-pressure jet grouting alone, the combined MJS reinforcement reduced tunnel deformation by 20%-35%, demonstrating superior performance in complex underground environments. (3) A deformation prediction model was developed based on Mindlin's elastic solution and the Liffkin model, incorporating the "composite modulus method" and "layer-wise method" to account for reinforcement effects. The accuracy and effectiveness of this model were validated.