A method for continuous shield tunneling under waterways

Abstract

This invention relates to a method for continuous shield tunneling under waterways, belonging to the field of shield tunneling technology for under-waterway tunneling. The method includes: constructing a three-dimensional finite element model based on geological survey data, dividing the geological formation into units and inputting parameters, and dynamically applying tidal water level loads; iteratively updating pore water pressure, effective stress, and formation deformation through a nonlinear adjustment mechanism of elastic modulus-water content function and permeability coefficient, combined with a seepage-stress fully coupled algorithm; embedding the shield tunneling process to simulate the interaction between construction disturbance and tidal loads, optimizing shield construction parameters and water-stopping measures; real-time acquisition of monitoring data, correction of model parameters, and dynamic adjustment of construction parameters; simulating the formation response during multiple tidal cycles, evaluating the long-term cumulative effect of tidal water pressure, and optimizing water-stopping strategies and construction plans.

Description

Technical Field

[0001] This invention relates to the field of shield tunneling technology for tunneling under waterways, and in particular to a method for continuous shield tunneling construction under waterways. Background Technology

[0002] Underwater shield tunnel construction faces the dual challenges of complex geological conditions and the aquatic environment. This field typically involves tunneling through riverbeds or seabeds using a tunnel boring machine (TBM), while simultaneously addressing key technical aspects such as controlling ground deformation, preventing water leakage, and ensuring tunnel structural stability. Common construction techniques include geological exploration, numerical simulation analysis, and optimization of tunneling parameters. Numerical simulation often utilizes methods such as the finite element method to simulate the construction process and guide on-site construction. However, tidal fluctuations in aquatic environments dynamically affect the stress and seepage fields of the strata. Traditional construction techniques require comprehensive consideration of factors such as stratum lithology, hydrological conditions, and TBM performance to ensure construction safety and project quality.

[0003] CN114718585A discloses a shield tunneling method suitable for tunneling under a tidal lake. The method includes: firstly, conducting an on-site survey to determine the extent of unfavorable geological conditions in the tidal lake area, and marking the strata within the range as grouting strata; secondly, setting up cofferdams in different areas of the grouting strata to lower the water level of the tidal lake, and inserting grouting pipes inside the cofferdams to inject grout to reinforce the unfavorable geological conditions in the tidal lake area; and thirdly, after grouting is completed, starting the shield tunneling machine for tunneling. During the tunneling process, setting up cofferdams again in different areas to reduce the impact of tidal water level changes on the tunneling process, and simultaneously adjusting the pressure in the tunnel chamber in front of the shield according to the tidal pattern, increasing the pressure in the tunnel chamber during high tide and decreasing the pressure in the tunnel chamber during low tide.

[0004] Current technologies face numerous challenges in addressing shield tunneling under waterways. Traditional finite element simulations often employ static water pressure loading, failing to couple tidal level fluctuations as dynamic loads with the tunneling progress in a spatiotemporal manner. This results in an inaccurate reflection of the interaction between the tidal cycle and the excavation process. Furthermore, formation material parameters are frequently treated as static constants, neglecting the dynamic impact of tidal water infiltration on parameters such as elastic modulus and permeability, making it difficult to simulate formation degradation. The analysis of seepage and stress fields often employs sequential coupling, hindering real-time interactive iteration and resulting in insufficient analysis of the instantaneous impact of tidal water pressure on formation stress. Moreover, existing technologies lack in-depth analysis of the synergistic effects of construction disturbances and tidal loads, lack quantitative assessment of the cumulative effects of long-term tidal cycles, and suffer from an imperfect dynamic fusion mechanism between monitoring data and simulation models, making it difficult to construct an effective risk warning and construction parameter optimization system.

[0005] Furthermore, on the one hand, there are differences in understanding among those skilled in the art; on the other hand, the applicant studied a large number of documents and patents when making this invention, but due to space limitations, not all details and contents were listed in detail. However, this does not mean that the present invention does not possess the features of these prior art. On the contrary, the present invention already possesses all the features of the prior art, and the applicant reserves the right to add relevant prior art to the background art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to provide a method for continuous shield tunneling under waterways. This method achieves precise quantification of the synergistic effect of tidal dynamic loads and construction disturbances through multidisciplinary coupled modeling. Furthermore, it introduces a dynamic material parameter adjustment mechanism for the first time to solve the problem of long-term ground weakening during long-distance construction.

[0007] This invention discloses a method for continuous shield tunneling construction under waterways, comprising:

[0008] Modeling and application of tidal load: A three-dimensional finite element model is constructed based on geological survey data, stratigraphic units are divided and parameters are input, and tidal water level load is dynamically applied;

[0009] Dynamic parameter adjustment and fully coupled simulation: By using the elastic modulus-water cut function and the nonlinear adjustment mechanism of permeability coefficient, combined with the seepage-stress fully coupled algorithm, the pore water pressure, effective stress and formation deformation are iteratively updated;

[0010] Co-operational analysis of construction disturbance and tidal load: Embedded in the shield tunneling process, the interaction between construction disturbance and tidal load is simulated to optimize shield construction parameters and water-stopping measures;

[0011] Monitoring data fusion and parameter optimization: Real-time acquisition of monitoring data, correction of model parameters, and dynamic adjustment of construction parameters;

[0012] Long-term effect analysis and iterative optimization: Simulate the formation response under multiple tidal cycles, evaluate the long-term cumulative effect of tidal water pressure, and optimize the water-stopping strategy and construction plan.

[0013] This invention proposes a continuous shield tunneling method for crossing waterways. By constructing a three-dimensional finite element model and dynamically applying tidal water level loads, it solves the problem of assessing the stability of strata caused by the superposition of tidal cycles and construction cycles in long-distance waterway engineering projects. Traditional static analysis methods only consider average water level or single tidal fluctuations, failing to capture the long-term weakening effect of multi-cycle tidal pressure on the strata. This invention, however, achieves real-time simulation of the degradation process of strata mechanical properties by dynamically applying tidal water level loads (e.g., using a sine function expression to define the water level change law), combined with an elastic modulus-water content function and a nonlinear adjustment mechanism for the permeability coefficient. For example, in semi-diurnal tidal waterways such as the Pearl River, tidal water level fluctuations may gradually reduce the elastic modulus of moderately weathered mudstone through seepage. This method quantifies this degradation trend through a dynamic parameter adjustment mechanism, thereby optimizing the location of the waterstop ring and the grouting pressure. Furthermore, the synergistic analysis of construction disturbances and tidal loads (such as stress release caused by shield tunneling) further enhances the model's ability to predict local instability at the excavation face, providing a scientific basis for the quantitative assessment of the cumulative tidal effect in long-distance construction.

[0014] According to a preferred embodiment, in the modeling and tidal load application steps, the scope of the three-dimensional finite element model extends to a certain distance outside the left and right lines of the tunnel, the longitudinal direction covers the width of the water area and the construction section, and the vertical direction extends from the ground surface to a predetermined depth below the bottom of the tunnel. The stratigraphic unit division combines the exploration data to distinguish different soil and rock types, and inputs physical and mechanical parameters such as unit weight, internal friction angle, cohesion and permeability coefficient.

[0015] Traditional models are typically limited to the area near the tunnel axis, making it difficult to reflect the impact of riverbed sediment layering characteristics (such as the permeability difference between sand-gravel mixed layers and clay layers) and levee structural stiffness differences (such as the difference in elastic modulus between concrete levees and natural earthen levees) on tidal pressure conduction. This invention, by dividing the land into stratigraphic units such as silty clay, sand, gravel, and weathered rock, and inputting physical and mechanical parameters such as unit weight, internal friction angle, cohesion, and permeability coefficient, can more accurately simulate the mechanical responses of different soil and rock types. For example, the high permeability of sand layers may become the main conduction path of tidal pressure, while the low permeability of clay layers restricts pressure diffusion. This heterogeneity is reflected in the model through stratigraphic unit division and parameter input, thus providing a foundation for analyzing the diffusion path of tidal pressure in the strata.

[0016] According to a preferred embodiment, in the modeling and tidal load application steps, the tidal water level is applied as a dynamic load to the top boundary of the model. The water level change law is defined by a sine function expression. Considering the stratification characteristics of riverbed sediments and the stiffness difference of the levee structure, a contact surface element with shear sliding characteristics is set between the riverbed and the top of the tunnel to simulate the shearing effect of tidal water pressure on the strata.

[0017] This invention solves the problem of dynamically matching tidal fluctuations with the stress transfer path of the strata in long-distance tunneling projects by applying tidal water level as a dynamic load to the top boundary of the model and defining the water level change law using a sine function expression. Traditional methods often use static water pressure loading, which cannot reflect the real-time impact of periodic changes in tidal water level on the pore water pressure distribution. This invention dynamically applies tidal water level loads (such as updating the water level every hour during a semi-diurnal tidal cycle), and combines the stratification characteristics of riverbed sediments and the stiffness differences of the levee structure to set up contact surface elements with shear sliding characteristics between the riverbed and the tunnel top, simulating the shearing effect of tidal water pressure on the strata. For example, during the peak tidal period (high tide), the small sliding of the contact surface elements can reflect the shear deformation of the strata caused by water pressure changes, thereby identifying potential local instability areas. This design is particularly suitable for analyzing the superimposed effects of tidal cycles and tunneling rhythms in long-distance construction, ensuring that the model can capture the dynamic response characteristics of the strata under tidal loads.

[0018] According to a preferred embodiment, in the dynamic parameter adjustment and fully coupled simulation steps, the model boundary conditions are set as follows: the top surface is a free surface bearing tidal water level load and dynamically updating pore water pressure; the bottom surface has a fixed water head; the side surfaces are selected with normal constraints or tangential free constraints according to geological conditions; the initial stress field is calculated through self-weight stress; and the pore water pressure field is initialized in conjunction with the groundwater level distribution.

[0019] This invention addresses the accuracy issue in simulating multi-boundary coupling effects in long-distance underwater engineering projects by setting the model's boundary conditions (the top surface is a free surface bearing tidal water level loads and dynamically updating pore water pressure; the bottom surface has a fixed head; and the side surfaces are subject to either normal or tangential free constraints based on geological conditions). Traditional models often use single boundary conditions (such as fixed head or free surface), which are insufficient to fully reflect the complexity of the actual geological environment. This invention, by dynamically loading tidal water level loads on the top surface (e.g., defining water level changes using a sine function expression), combined with a fixed head on the bottom surface (e.g., groundwater level at a depth of 5 meters) and side constraints (e.g., rigid constraints on riverbanks), more realistically simulates the seepage path of tidal water pressure in the strata. For example, in the Pearl River underwater section, the rigid side constraints reflect the limiting effect of the dike structure on stratum deformation, while the fixed head on the bottom surface ensures the stability of deep groundwater. Furthermore, the initial stress field is calculated using self-weight stress, and the pore water pressure field is initialized using survey data, further enhancing the model's ability to reproduce the initial state of the strata.

[0020] According to a preferred embodiment, in the dynamic parameter adjustment and fully coupled simulation step, a functional relationship between the elastic modulus and the water content is introduced, and the permeability coefficient is dynamically adjusted nonlinearly based on the change in water content to reflect the diffusion path of tidal water pressure in the formation.

[0021] This invention solves the problem of quantifying the long-term weakening effect of tidal water pressure on formation strength in long-distance underwater engineering projects by introducing a functional relationship between elastic modulus and water content, and by dynamically adjusting the permeability coefficient nonlinearly based on changes in water content. Traditional models typically assume that the elastic modulus and permeability coefficient are static constants, which cannot reflect the formation performance degradation process caused by tidal water infiltration. This invention quantifies the "softening upon contact with water" phenomenon of weathered mudstone and other soil materials through the elastic modulus-water content function, and combines it with a nonlinear adjustment mechanism of the permeability coefficient (e.g., the permeability coefficient of sand layers increases with increasing water content) to simulate the diffusion path of tidal water pressure in the formation. For example, under continuous tidal water pressure, the permeability coefficient of sand layers may significantly increase due to increased water content, forming efficient hydraulic channels, which in turn leads to an abnormal increase in pore water pressure in clay layers. This dynamic adjustment mechanism provides a scientific basis for optimizing construction parameters (such as grouting pressure and the location of water-stop rings), and is particularly suitable for analyzing the cumulative effect of formations exposed to tidal water pressure for a long time in long-distance construction.

[0022] According to a preferred embodiment, in the dynamic parameter adjustment and fully coupled simulation steps, a fully coupled algorithm is used to iteratively complete the following steps in each time step: update the top pore water pressure according to the tidal water level and solve the formation pore water pressure distribution, correct the formation effective stress field based on the effective stress principle, calculate the formation deformation and displacement, and simulate the stress release of shield tunneling.

[0023] This invention employs a fully coupled algorithm to iteratively update pore water pressure, correct effective stress, calculate ground deformation, and simulate excavation at each time step, solving the challenge of simulating the instantaneous impact of tidal level fluctuations on ground stress in long-distance underwater tunnel projects. Traditional sequential coupling methods (seepage first, then stress) cannot capture the real-time interaction between tidal pressure and ground stress, while this invention uses an adaptive iterative strategy to synchronously update the pore water pressure field and effective stress field at each time step (e.g., 1 hour / step). For example, during peak tidal periods (high tide), the model can accurately predict the fluctuation range of the soil pressure at the excavation face (e.g., increasing to 2.5 bar), whereas traditional methods, neglecting the matching of tidal phase and tunneling rhythm, cannot achieve such dynamic adjustments. Furthermore, the embedding of the shield tunneling process (e.g., excavation face advancement, grouting pressure application) further improves the model's simulation accuracy of the synergistic effects of construction disturbances and tidal loads.

[0024] According to a preferred embodiment, the process of tunneling face advancement, grouting pressure application, and soil chamber pressure adjustment is embedded in the collaborative analysis step of construction disturbance and tidal load to simulate the interaction between construction disturbance and tidal load, and to optimize the tunneling parameters, grouting pressure, and waterstop ring placement.

[0025] This invention addresses the risk of localized ground instability caused by the combined effects of construction disturbances and tidal loads in long-distance tunneling projects under waterways by embedding the processes of excavation face advancement, grouting pressure application, and soil chamber pressure adjustment during shield tunneling. Traditional methods often analyze construction disturbances (such as grouting pressure) or tidal loads (such as water level fluctuations) independently, making it difficult to comprehensively assess the impact of their interaction. This invention optimizes shield construction parameters (such as increasing the tidal peak pressure to 2.5 bar) and the placement of the waterstop rings (such as 10-15 rings behind the shield tail) by simulating the superimposed effect of excavation face stress release and tidal water pressure fluctuations during shield tunneling. For example, near the excavation face, tidal water pressure fluctuations may trigger localized soil flow or piping. The model calculates the real-time distribution of pore water pressure using a fully coupled seepage-stress algorithm and combines this with the shear strength of the strata to assess the risk of failure, thereby guiding the dynamic adjustment of construction parameters. This design is particularly suitable for analyzing the superposition effect of tidal cycles and tunneling cycles in long-distance construction, ensuring that the synergistic effect of construction disturbance and tidal load is scientifically quantified.

[0026] According to a preferred embodiment, in the monitoring data fusion and parameter optimization step, a multi-level early warning system is constructed based on simulation results and monitoring data, and critical conditions for stratum failure are set. When the pore water pressure gradient exceeds the critical value or the stratum shear strength is lower than the effective stress, an early warning is triggered, and an emergency response strategy corresponding to the risk level is preset. The monitoring data includes surface subsidence, pore water pressure, and shield tunnel subsidence.

[0027] This invention constructs a multi-level early warning system based on simulation results and monitoring data, solving the problem of real-time monitoring and emergency response to ground damage risks in long-distance tunneling projects. Traditional methods often rely on single monitoring indicators (such as surface subsidence), making it difficult to comprehensively assess the multi-dimensional impact of tidal pressure on the ground. This invention constructs a multi-level early warning system by setting critical conditions for ground damage (such as pore water pressure gradient and shear strength ratio) and combining monitoring data on surface subsidence, pore water pressure, and shield tunnel settlement. For example, when simulation results show that the pore water pressure gradient in a certain area is close to the critical value of Darcy's law, a "seepage failure early warning" is triggered, and an emergency response strategy is preset (such as increasing the frequency of double-liquid grout sealing ring application). In addition, the linkage between the model and field monitoring data (such as real-time data acquisition through pore water pressure gauges) further improves the accuracy of the early warning.

[0028] According to a preferred embodiment, in the long-term effect analysis and iterative optimization step, the formation performance degradation is simulated by the "time-water content-parameter" correlation function, and a function of the reduction coefficient changing with time is introduced to analyze the cumulative effect of pore water pressure in combination with the seepage-stress fully coupled algorithm.

[0029] This invention simulates formation performance degradation using a "time-moisture-parameter" correlation function, solving the problem of formation strength degradation caused by the long-term cumulative effect of tidal water pressure in long-distance underwater engineering projects. Traditional methods often focus on the instantaneous impact of a single tidal fluctuation, making it difficult to quantify the gradual damage to formation performance caused by long-term tidal cycles (e.g., 30 cycles). This invention simulates the long-term weakening trend of weathered mudstone and other soil materials using a function of the elastic modulus reduction coefficient over time, and combines this with a seepage-stress fully coupled algorithm to analyze the cumulative effect of pore water pressure. For example, under continuous tidal water pressure, the elastic modulus of the formation may gradually decrease to below 50% of its initial value. The model quantifies this degradation process by dynamically adjusting the reduction coefficient, thereby optimizing water-stopping strategies (e.g., adjusting the grouting material ratio) and construction schemes (e.g., reducing tunneling speed).

[0030] According to a preferred embodiment, in the long-term effect analysis and iterative optimization step, the influence of stratum heterogeneity on tidal seepage path is considered. By adjusting the permeability coefficient distribution of different strata in the model, high-risk areas of tidal water pressure transmission are identified, and water-stopping strategies and construction plans are optimized.

[0031] This invention addresses the challenge of analyzing the impact of stratigraphic heterogeneity on tidal seepage paths in long-distance underwater engineering projects by adjusting the permeability coefficient distribution of different strata in the model to identify high-risk areas for tidal pressure conduction. Traditional methods often assume homogeneous constant permeability coefficients, failing to reflect the permeability differences between sand layers, clay layers, and weathered rock masses in actual geological conditions. This invention simulates the conduction patterns of tidal pressure in heterogeneous strata by dynamically adjusting the permeability coefficients of different strata (e.g., increasing the permeability coefficient of sand layers and decreasing the permeability coefficient of clay layers). For example, in the Pearl River underwater section, the mixed sand and gravel layer at the riverbed may become the main conduction path for tidal pressure. The model can identify such high-risk areas by adjusting the permeability coefficients and optimize water-stopping strategies (e.g., increasing the placement of double-liquid grout sealing rings). Attached Figure Description

[0032] Figure 1 This is a flowchart of the steps of the continuous shield tunneling construction method for crossing waterways provided by the present invention;

[0033] Figure 2 This is a schematic diagram of continuous shield tunneling construction under waterways provided by the present invention;

[0034] Figure 3 This is a schematic diagram of a three-dimensional finite element model constructed based on geological exploration data in a preferred embodiment of the present invention;

[0035] Figure 4 This is a schematic diagram of riverbed and ground settlement after tunnel construction, shown by simulation results provided by the present invention. Detailed Implementation

[0036] The following is a detailed explanation with reference to the accompanying drawings.

[0037] like Figure 1 As shown, this invention discloses a method for continuous shield tunneling construction under waterways, which includes:

[0038] Modeling and application of tidal load: A three-dimensional finite element model is constructed based on geological survey data, stratigraphic units are divided and parameters are input, and tidal water level load is dynamically applied;

[0039] Dynamic parameter adjustment and fully coupled simulation: By using the elastic modulus-water cut function and the nonlinear adjustment mechanism of permeability coefficient, combined with the seepage-stress fully coupled algorithm, the pore water pressure, effective stress and formation deformation are iteratively updated;

[0040] Co-operational analysis of construction disturbance and tidal load: Embedded in the shield tunneling process, the interaction between construction disturbance and tidal load is simulated to optimize shield construction parameters and water-stopping measures;

[0041] Monitoring data fusion and parameter optimization: Real-time acquisition of monitoring data (pore water pressure, settlement, etc.), correction of model parameters, and dynamic adjustment of construction parameters (tunneling speed, grouting volume, etc.);

[0042] Long-term effect analysis and iterative optimization: Simulate the formation response under multiple tidal cycles, evaluate the long-term cumulative effect of tidal water pressure, and optimize the water-stopping strategy and construction plan.

[0043] In long-distance shield tunneling under waterways, the impact of tidal level fluctuations on ground stability is one of the core challenges to project safety. To address this unique construction environment, a high-precision numerical model can be constructed before construction using a three-dimensional finite element dynamic simulation method under tidal influences. This model comprehensively analyzes the dynamic interaction between tidal level changes and ground stress, providing a scientific basis for subsequent optimization of construction parameters. This simulation process comprehensively considers the complexity of the water geology, the long-term nature of the tidal cycle, and the continuity of shield tunneling, ensuring that the model accurately reflects the coupling effect of tidal loads and ground response during construction.

[0044] Preferably, such as Figure 2 and Figure 3As shown, the tidal dynamic simulation before construction requires a detailed geological survey report to establish a three-dimensional geological model covering the tunnel axis and surrounding affected areas. The model range needs to extend to a certain distance on both sides of the tunnel (e.g., 50 meters each), with the longitudinal length determined by the width of the water area and the construction section (e.g., the transverse width of the Pearl River underpass can reach 150 meters). The vertical direction needs to cover the strata from the surface to below the bottom of the tunnel (e.g., 20 meters). Stratigraphic division can be combined with survey data to accurately distinguish different soil and rock units such as silty clay, sand, gravel, and weathered rock. The physical and mechanical parameters of each stratum (e.g., unit weight, internal friction angle, cohesion, permeability coefficient, etc.) can be input into the model based on laboratory tests or field test results. For (long-distance) underpass projects, special attention needs to be paid to the stratification characteristics of riverbed sediments (e.g., silt and gravel mixed layers) and the stiffness differences of the embankment structure (e.g., the difference in elastic modulus between concrete embankments and natural earthen embankments). These characteristics will directly affect the stress transmission path of tidal fluctuations to the strata.

[0045] Preferably, the parameter settings can focus on addressing the dynamic impact of tidal level fluctuations on the formation. For example, in tidal waters such as the Pearl River, the tidal cycle is typically semi-diurnal (approximately 12 hours), and the water level amplitude can reach 2 meters. In the model, the tidal level can be applied as a dynamic load to the top boundary, rather than the traditional static water pressure loading. To simulate the periodicity of tidal fluctuations, a sine function expression can be used to define the water level change law, as shown in the formula:

[0046] .

[0047] Where h0 is the average water level, A is the tidal amplitude, T is the tidal period, and t is the time variable.

[0048] This dynamic load can be synchronized with the tunnel boring machine's (TBM) progress. The time step (e.g., 1 hour / step) is determined by the number of rings the TBM excavates daily (e.g., 10 rings / day, 15 meters / day), ensuring that the excavation face's advance speed matches the phase change of the tidal cycle in the simulation. This spatiotemporal coupling modeling method can reflect the real-time impact of tidal fluctuations on ground stress, and is particularly suitable for analyzing the superimposed effects of tidal cycles and tunneling rhythm in long-distance construction.

[0049] Preferably, the boundary conditions of the model can be specifically set based on the particularities of water engineering. The top boundary can be set as a free surface, directly bearing the tidal water level load, and simulating the seepage effect of water level fluctuations on the strata through dynamic updates of pore water pressure; the bottom boundary can have a fixed water head (e.g., a groundwater level depth of 5 meters) to reflect the stable state of deep groundwater; the lateral boundaries are selected based on actual geological conditions, choosing between normal constraints or tangential free constraints. For example, in long-distance water crossings, the lateral boundaries may need to consider the rigid constraints of riverbanks or levees. Furthermore, the model can preset an initial stress field and a pore water pressure field as the starting point for dynamic simulation. The initial stress field can be obtained through self-weight stress calculation, while the pore water pressure field needs to be initialized in conjunction with the groundwater level distribution in the exploration data.

[0050] Preferably, for (long-distance) underwater tunnel projects, the boundary treatment of the contact surface between the riverbed and the tunnel roof should also be considered when setting boundary conditions and initial site settings. Since tidal fluctuations may infiltrate the surrounding strata through riverbed sediments, the contact surface units need to be designed with shear-slip characteristics to simulate the shearing effect of tidal pressure on the strata. For example, the friction coefficient of the contact surface can be set to 0.3, allowing for slight relative sliding during tidal rises, thereby reflecting the dynamic deformation characteristics of the strata under tidal loads.

[0051] Preferably, in tidal dynamic simulation, the dynamic adjustment of formation material parameters is key to improving model accuracy. In traditional finite element simulations, formation parameters (such as elastic modulus and permeability coefficient) are usually treated as static constants. However, in (long-distance) underwater engineering projects, tidal level fluctuations can cause periodic changes in formation water content, thus affecting its mechanical properties. For example, moderately weathered mudstone may experience "softening upon contact with water" under tidal water infiltration, and its elastic modulus will significantly decrease with increasing water content. Therefore, a dynamic material parameter adjustment mechanism can be introduced into the model, setting a functional relationship between elastic modulus and water content:

[0052] .

[0053] Where E0 is the initial elastic modulus, k is the reduction factor, and Δw is the moisture content increment.

[0054] The reduction factor is a coefficient that describes the change of formation mechanical parameters (such as elastic modulus and cohesion) with environmental conditions (such as water content and temperature). It reflects the degree of performance degradation of materials under specific environmental conditions and can be obtained by combining laboratory tests, field tests, and empirical formulas. For example, the elastic modulus of moderately weathered mudstone may decrease significantly due to an increase in water content, and the reduction factor k represents the proportion of elastic modulus loss corresponding to each unit change in water content.

[0055] This mechanism can simulate the formation strength weakening process caused by tidal water infiltration, and is especially suitable for the analysis of the cumulative effect of formations being exposed to tidal water pressure for a long time during long-distance construction.

[0056] Furthermore, this invention allows for dynamic adjustment of the permeability coefficient during tidal dynamic simulation. The dynamic adjustment of the permeability coefficient directly affects the calculation accuracy of the seepage field. For example, under tidal level fluctuations, a higher permeability coefficient leads to rapid diffusion of pore water pressure, thereby reducing the effective stress of the formation; conversely, a lower permeability coefficient restricts the transmission of water pressure, resulting in localized stress concentration. By dynamically adjusting the permeability coefficient, the model can more realistically reflect the influence of tidal water pressure on the seepage path and deformation mode of the formation, thus providing a basis for optimizing construction parameters (such as grouting pressure).

[0057] Under tidal fluctuations, the permeability coefficient of a formation adjusts nonlinearly with changes in water cut. For example, the permeability coefficient of a certain sand layer increases from 0.1 m / d to 0.2 m / d as the water cut increases from 20% to 30%. This change can be reflected in the model through fitting experimental data or empirical formulas. Setting a dynamic permeability coefficient can more realistically reflect the diffusion path of tidal pressure in the formation, providing a foundation for subsequent fully coupled seepage-stress analysis.

[0058] The core of tidal dynamic simulation lies in achieving real-time interaction between the seepage field and the stress field. In traditional finite element analysis, seepage calculation and stress calculation are usually sequentially coupled (seepage first, then stress). However, in (long-distance) underwater engineering projects, the instantaneous impact of tidal level fluctuations on formation stress needs to be realized through a fully coupled algorithm. Specifically, the model needs to complete the following iterative process within each time step (e.g., 1 hour):

[0059] Pore ​​water pressure update: Calculate the top pore water pressure based on the current tidal level, and solve the pore water pressure distribution inside the formation through seepage analysis;

[0060] Effective stress correction: Based on Darcy's law and the effective stress principle (σ′=σ-u), update the effective stress field of the formation;

[0061] Stress-strain response: Calculate the deformation and displacement of the formation using the corrected effective stress field;

[0062] Excavation Simulation: Activate or deactivate elements near the excavation face to simulate stress release caused by tunnel boring.

[0063] To improve computational efficiency, adaptive iterative algorithms can be employed in the model. For example, the number of iterations can be increased near the excavation face (e.g., 20 iterations / step), while the number of iterations can be reduced in stable strata far from the excavation area (e.g., 10 iterations / step). This dynamically adjusted iterative strategy can balance computational accuracy and resource consumption, and is particularly suitable for efficiently solving large-scale models in long-distance construction.

[0064] Preferably, after completing the dynamic simulation, the results can be verified in multiple dimensions to ensure the reliability of the model. First, the simulated ground deformation (such as riverbed settlement and levee horizontal displacement) can be compared with the field monitoring data. If the error is controlled within 3%, it indicates that the model accuracy meets the requirements. Second, the pore water pressure distribution can be analyzed to determine whether potential hydraulic channels or seepage damage risks have formed. For example, in the Pearl River underpass section, if the simulation results show that the pore water pressure gradient around the tunnel is close to the critical value, it is necessary to suggest strengthening water-stopping measures during construction (such as increasing the density of double-liquid grouting). Figure 4 The diagram shows the riverbed and ground settlement after tunnel construction, as demonstrated by simulation results.

[0065] Furthermore, the simulation results can be used to predict key risk points during construction. For example, in (long-distance) underwater tunnel projects, tidal fluctuations can lead to local instability at the tunnel excavation face. Simulations can identify the range of soil pressure fluctuations at the excavation face during peak tidal periods (such as high tide), thus guiding adjustments to shield tunneling parameters during construction (e.g., increasing soil pressure to 2.5 bar during peak tidal periods). Simultaneously, the simulation can also predict the optimal location for installing water-stop rings (e.g., 10-15 rings behind the shield tail) to block the seepage path of tidal water pressure into the underlying strata.

[0066] Preferably, before construction, the tidal dynamic simulation can undergo multiple rounds of iterative optimization to adapt to adjustments in the construction plan. For example, if the preliminary simulation shows that the settlement control value of a certain section of the stratum is close to the limit (e.g., 20 mm), it can be recalculated by modifying the model parameters (e.g., increasing grouting pressure, adjusting tunneling speed) until the safety requirements are met. In addition, the model can also be used for construction pre-simulation, that is, by simulating the impact of different construction strategies (e.g., pre-reinforcing dikes, optimizing cutterhead penetration) on stratum deformation, it can assist in formulating the optimal construction plan.

[0067] Because construction periods typically last for months or even longer, the strata may undergo complex physicochemical changes under repeated tidal loads, leading to a gradual degradation of their mechanical properties. For (long-distance) underwater engineering projects, iterative optimization of the model can also consider the long-term cumulative effect of tidal cycles. For example, when construction lasts for several months, the model can simulate the strata response over multiple tidal cycles (e.g., 30 cycles, corresponding to approximately 30 days) to assess the long-term weakening effect of tidal pressure on strata strength. This weakening effect is not only related to the instantaneous impact of a single tidal fluctuation but also closely related to the long-term cumulative effect of tidal cycles. Therefore, iterative optimization of the model can utilize dynamic simulation methods, combined with laboratory tests and field monitoring data, to systematically analyze the gradual destructive mechanism of tidal pressure on the strata.

[0068] Preferably, in (long-distance) underwater engineering projects, the long-term cumulative effect of tidal pressure mainly manifests as a three-stage evolution process of the strata: softening, infiltration, and failure. First, the periodic fluctuations of tidal levels gradually increase the water content of the strata through infiltration, leading to a decrease in mechanical parameters such as the elastic modulus and cohesion of the soil and rock materials (i.e., the "softening effect"). For example, in tidal waters such as the Pearl River, the elastic modulus of moderately weathered mudstone may gradually decrease to below 50% of its initial value under continuous tidal pressure for several months, significantly affecting the long-term stability of the tunnel structure. Second, with the continuous increase in water content, the permeability coefficient of the strata may increase non-linearly, forming more efficient hydraulic channels (i.e., the "infiltration enhancement effect"), accelerating the diffusion of pore water pressure. For example, the gravel-sand mixture in the riverbed sediments may become the main transmission path of tidal pressure, leading to an abnormal increase in pore water pressure in the deep clay layer, which in turn triggers local shear failure or overall instability (i.e., the "structural failure effect"). This multi-stage, progressive deformation risk is difficult to capture with traditional static analysis. This invention uses dynamic simulation combined with long-term observation data for quantitative assessment.

[0069] Furthermore, in the model, the long-term cumulative effect of tidal cycles can be realized through multi-cycle dynamic simulation, dynamic parameter adjustment mechanisms, and coupled analysis of construction disturbances. For tidal fluctuations within a construction cycle (e.g., 30 half-diurnal tidal cycles), the model needs to set a time step (e.g., 1 hour / step) and update formation parameters within each cycle. For example, the elastic modulus of moderately weathered mudstone can be dynamically adjusted using a "water content-time" function (i.e., the aforementioned functional relationship between elastic modulus and water content). This parameter adjustment mechanism can simulate the performance degradation trend of the formation under long-term tidal pressure. Simultaneously, the distribution changes of pore water pressure within each tidal cycle are calculated using a fully coupled seepage-stress algorithm. For example, during the peak tidal period (high tide), pore water pressure may locally increase due to enhanced permeability, leading to a decrease in effective stress; while during the trough tidal period (low tide), pore water pressure may slowly recover due to limited drainage. By continuously simulating multiple cycles, the cumulative effect of pore water pressure and its impact on formation stability can be identified. In addition, based on laboratory test data, the model needs to set critical conditions for formation failure (such as pore water pressure gradient, shear strength ratio, etc.). For example, if the simulation finds that the pore water pressure gradient in a certain area exceeds the critical value of Darcy's law, it indicates that there is a risk of seepage failure in that area; if the formation shear strength is lower than the effective stress, it indicates that shear instability may occur.

[0070] The unique characteristics of long-distance tunneling projects under waterways lie in the superimposed effects of the construction cycle and tidal cycle, the heterogeneity of the strata and the complexity of tidal infiltration paths, and the synergistic effect of construction disturbances and tidal loads. First, the construction cycle may cover dozens of tidal cycles, and the strata may undergo an evolution from "short-term softening" to "long-term weakening." For example, under continuous tidal pressure, the elastic modulus of moderately weathered mudstone may gradually decrease to below 50% of its initial value, significantly affecting the long-term stability of the tunnel structure. Second, the strata under the tunnel typically contain multiple layers of sand, clay, and weathered rock. Tidal pressure may rapidly infiltrate deeper strata through weak layers (such as sand layers), forming a chain reaction of "infiltration-weakening-damage." For example, in the Pearl River tunnel section, the sand-gravel mixture layer in the riverbed sediments may become the main transmission path of tidal pressure, leading to an abnormal increase in pore water pressure in the deep clay layer. Third, excavation disturbances during shield tunneling (such as stress release and grouting pressure) may exacerbate the damage of tidal pressure to the strata. For example, near the excavation face, tidal water pressure fluctuations may cause local soil flow or piping, and if the location of the water-stop ring does not fully consider the tidal phase, it may fail due to insufficient grouting pressure.

[0071] To address the aforementioned issues, the model of this invention can be optimized through a dynamic parameter update mechanism, permeability path sensitivity analysis, and coupled simulation of construction disturbances. A triple correlation function of "time-water content-parameter" is introduced into the simulation. This involves adding a specified parameter (such as the reduction coefficient k of the elastic modulus) over time to the "water content-time" function to reflect the long-term degradation trend of the formation performance. The reduction coefficient k of the elastic modulus can increase over time, e.g., k(t) = k0 + a·t, where k(t) is the reduction coefficient at time t; k0 is the initial reduction coefficient; a is the time influence coefficient; and t is the time variable. Simultaneously, this invention can simulate tidal water pressure transmission patterns under different formation combinations and identify high-risk areas by changing the spatial distribution of the permeability coefficient in the model (e.g., increasing the permeability coefficient of sand layers and decreasing the permeability coefficient of clay layers). Furthermore, the shield tunneling process (e.g., excavation face advancement and grouting pressure application) is embedded in the dynamic simulation to analyze the interaction between construction disturbances and tidal loads. For example, in the simulation, the grouting pressure can be set to automatically adjust with the fluctuation of the tidal water level (such as increasing the grouting pressure to 2.5 bar at the peak of the tide) to block the penetration of tidal water pressure into the strata behind.

[0072] Preferably, this invention can closely integrate the tidal dynamic simulation model established before construction with actual construction progress, ground response, and risk monitoring data. By updating model parameters in real time, dynamically adjusting construction strategies, and combining risk warning and emergency response mechanisms, a closed-loop management process of "simulation-monitoring-optimization-feedback" is formed. This invention is particularly suitable for the complexities of (long-distance) water crossing projects, such as the long-term superposition effect of tidal cycles, the heterogeneity of ground strata and the uncertainty of seepage paths, and the synergistic effect of construction disturbance and tidal loads. It ensures that the model can truly reflect the dynamic interaction between the ground strata and the structure during construction and provides a scientific basis for real-time adjustment of construction parameters.

[0073] Preferably, during the tunnel boring process, the model is iteratively corrected based on the three-dimensional finite element model established before construction, combined with real-time monitoring data (such as surface settlement, pore water pressure, and tunnel settlement), and the simulation results guide the dynamic adjustment of construction parameters.

[0074] Preferably, the periodic fluctuation of tidal water level is the core influencing factor in the construction of tunnels under waterways, and its dynamic load needs to be synchronized with the tunnel boring machine's (TBM) progress. During construction, the tidal load on the top surface of the model can be dynamically updated based on on-site tidal observation data (such as water level curves collected in real time by water level sensors). For example, the Pearl River tidal cycle is a semi-diurnal tide (approximately 12 hours), with a water level amplitude of up to 2 meters. The model can load the tidal water level step by step according to a sine function expression to ensure that the excavation face's advancement speed matches the tidal phase changes in the simulation. At the same time, the model can divide the time step (e.g., 1 hour / step) according to the actual TBM tunneling progress (e.g., 1.5 meters per ring, 10 rings per day), achieving spatiotemporal coupling of "excavation progress - tidal cycle". In addition, construction disturbances (such as soil chamber pressure, grouting pressure, tunneling speed, etc.) can be embedded into the model as dynamic boundary conditions. For example, the TBM soil chamber pressure can be automatically adjusted with the fluctuation of tidal water level (e.g., increased to 2.5 bar at the peak of the tide) to block the penetration of tidal water pressure into the subsequent strata.

[0075] Preferably, in dynamic simulations, formation material parameters (such as elastic modulus and permeability coefficient) can be dynamically adjusted based on real-time monitoring data. For example, the elastic modulus of moderately weathered mudstone can be dynamically reduced using a "water content-time" function, where the water content increment comes from real-time monitoring data from pore water pressure gauges. Simultaneously, the adjustment of the permeability coefficient needs to be combined with changes in formation water content (e.g., the permeability coefficient of sand layers increases with increasing water content), achieved through experimental data fitting or empirical formulas.

[0076] Preferably, in addition to predicting formation deformation, the dynamic simulation results can be combined with risk threshold determination to construct a multi-level early warning system. For example, the model can set critical conditions for formation failure (such as pore water pressure gradient and shear strength ratio). When the simulation results show that the pore water pressure gradient in a certain area exceeds the critical value of Darcy's law, a "permeability failure early warning" is triggered. If the formation shear strength is lower than the effective stress, it indicates that shear instability may occur. In addition, the model can be linked with field monitoring data. For example, the temperature of the excavated soil can be monitored by a laser thermometer (controlled to ≤28℃). If the temperature rises abnormally (such as the excavated soil temperature exceeding 30℃), it indicates the risk of mud cake formation and initiates the foaming agent injection procedure. In terms of emergency response, the model can preset response strategies for different risk levels. Among them, the response strategies for low-risk warnings may include optimizing shield construction parameters by adjusting tunneling speed or grouting pressure; the response strategies for medium-risk warnings may include increasing the frequency of double-liquid grout sealing rings (e.g., from every 15 rings to every 10 rings) and adjusting the grouting material ratio (e.g., increasing the proportion of water glass to shorten the solidification time); the response strategies for high-risk warnings may include initiating secondary grouting (pressure 0.3~0.4 MPa, multiple small amounts) or deep hole grouting to cut off the water supply channel from the rear.

[0077] Preferably, in (long-distance) underwater tunneling projects, the combined effect of excavation disturbances (such as stress release and grouting pressure) and tidal loads during shield tunneling can lead to localized soil flow or piping. Dynamic simulation can be embedded in the shield tunneling process (such as excavation face advancement and grouting pressure application) to analyze the impact of construction disturbances on stratum stability. For example, near the excavation face, tidal water pressure fluctuations may trigger localized soil flow. The model can calculate the real-time distribution of pore water pressure using a seepage-stress fully coupled algorithm and combine this with the stratum shear strength to determine whether there is a risk of failure. If the simulation results show that the pore water pressure gradient in a certain area is close to the critical value, it indicates that the grouting pressure needs to be adjusted or a waterstop ring needs to be installed in advance. In addition, the model can consider the disturbance of the stratum stress field caused by changes in the shield machine's attitude (such as cutterhead rotation and jack hydraulic pressure adjustment). For example, in strongly weathered strata, the cutterhead penetration is controlled at 30~35 mm / r, and the tunneling speed is 50~60 mm / min to reduce disturbance to the strata and reduce the risk of blowouts.

[0078] Preferably, dynamic simulation needs to be integrated with on-site monitoring data in real time to correct model parameters and improve prediction accuracy, thereby enabling real-time adjustment of tunneling parameters. For example, in long-distance tunnels under the Pearl River, pore water pressure gauges, settlement sensors, and ground strain gauges can be deployed to collect ground response data in real time during construction. Comparing these data with simulation results can correct model parameters (such as reduction coefficient k and permeability coefficient) and optimize simulation accuracy. For example, if there is a deviation between the measured horizontal displacement of the embankment (such as a maximum of 0.25 mm in the Dongsha Station-Yajisha Island section) and the simulation results, the elastic modulus of the embankment concrete or the contact surface friction coefficient in the model needs to be adjusted. In addition, the model needs to verify the rationality of construction parameters through a closed-loop system of "simulation-monitoring-optimization". For example, if the settlement rate of a certain section of the stratum is found to exceed the control standard (such as 20 mm / month) in the simulation, it will indicate that the tunneling speed needs to be reduced or the synchronous grouting volume needs to be increased to compensate for the ground loss caused by tidal water pressure.

[0079] It should be noted that the specific embodiments described above are exemplary. Those skilled in the art can devise various solutions inspired by the disclosure of this invention, and these solutions all fall within the scope of this invention and its protection. Those skilled in the art should understand that this specification and its accompanying drawings are illustrative and do not constitute a limitation on the claims. The scope of protection of this invention is defined by the claims and their equivalents. This specification contains multiple inventive concepts; phrases such as "preferred" or "according to a preferred embodiment" indicate that the corresponding paragraph discloses an independent concept. The applicant reserves the right to file divisional applications based on each inventive concept. Throughout the text, the feature introduced by "preferred" is only an optional mode and should not be construed as mandatory. Therefore, the applicant reserves the right to abandon or delete relevant preferred features at any time.

Claims

1. A shield tunneling method for under-crossing a water area, characterized by, It includes: Modeling and application of tidal load: A three-dimensional finite element model is constructed based on geological survey data, stratigraphic units are divided and parameters are input, and tidal water level load is dynamically applied; Dynamic parameter adjustment and fully coupled simulation: By using the elastic modulus-water cut function and the nonlinear adjustment mechanism of permeability coefficient, combined with the seepage-stress fully coupled algorithm, the pore water pressure, effective stress and formation deformation are iteratively updated; Co-operational analysis of construction disturbance and tidal load: Embedded in the shield tunneling process, the interaction between construction disturbance and tidal load is simulated to optimize shield construction parameters and water-stopping measures; Monitoring data fusion and parameter optimization: Real-time acquisition of monitoring data, correction of model parameters, and dynamic adjustment of construction parameters; Long-term effect analysis and iterative optimization: Simulate the formation response under multiple tidal cycles, evaluate the long-term cumulative effect of tidal water pressure, and optimize the water-stopping strategy and construction plan.

2. The method of claim 1, wherein, In the modeling and tidal load application steps, the scope of the three-dimensional finite element model extends to a certain distance outside the left and right lines of the tunnel, the longitudinal influences the width of the water area and the construction section, and the vertical direction extends from the ground surface to a predetermined depth below the bottom of the tunnel. The stratigraphic unit division combines the exploration data to distinguish different soil and rock types, and inputs physical and mechanical parameters such as unit weight, internal friction angle, cohesion and permeability coefficient.

3. The method of claim 2, wherein, In the modeling and tidal load application steps, the tidal water level is applied as a dynamic load to the top boundary of the model. The water level change law is defined by a sine function expression. Considering the stratification characteristics of riverbed sediments and the stiffness difference of the embankment structure, a contact surface element with shear sliding characteristics is set between the riverbed and the top of the tunnel to simulate the shearing effect of tidal water pressure on the strata.

4. The method of claim 1, wherein, In the dynamic parameter adjustment and fully coupled simulation steps, the model boundary conditions are set as follows: the top surface is a free surface bearing tidal water level load and dynamically updating pore water pressure; the bottom surface has a fixed water head; the side surfaces are selected according to geological conditions, using normal constraints or tangential free constraints; the initial stress field is calculated through self-weight stress; and the pore water pressure field is initialized in conjunction with the groundwater level distribution.

5. The method of claim 4, wherein, In the dynamic parameter adjustment and fully coupled simulation steps, a functional relationship between the elastic modulus and the water content is introduced, and the permeability coefficient is dynamically adjusted nonlinearly based on the change in water content to reflect the diffusion path of tidal water pressure in the formation.

6. The method of claim 5, wherein, In the dynamic parameter adjustment and fully coupled simulation steps, the fully coupled algorithm is used to iterate in each time step: update the top pore water pressure according to the tidal water level and solve the pore water pressure distribution of the formation, correct the effective stress field of the formation based on the effective stress principle, calculate the formation deformation and displacement, and simulate the stress release of shield tunneling.

7. The method of claim 1, wherein, The collaborative analysis steps of construction disturbance and tidal load are embedded in the process of shield tunneling, including the advancement of the excavation face, the application of grouting pressure, and the adjustment of soil chamber pressure. This simulates the interaction between construction disturbance and tidal load, and optimizes shield tunneling parameters and grouting pressure.

8. The method of claim 1, wherein, In the monitoring data fusion and parameter optimization step, a multi-level early warning system is constructed based on simulation results and monitoring data. Critical conditions for stratum failure are set. When the pore water pressure gradient exceeds the critical value or the stratum shear strength is lower than the effective stress, an early warning is triggered. Emergency response strategies corresponding to the risk level are preset. The monitoring data includes surface subsidence, pore water pressure, and shield tunnel subsidence.

9. The method of claim 1, wherein, In the long-term effect analysis and iterative optimization steps, the formation performance degradation is simulated by the "time-water cut-parameter" correlation function, and a function of the reduction coefficient changing with time is introduced to analyze the cumulative effect of pore water pressure in combination with the seepage-stress fully coupled algorithm.

10. The method according to claim 9, characterized in that, In the long-term effect analysis and iterative optimization steps, the influence of formation heterogeneity on tidal seepage path is considered. By adjusting the permeability coefficient distribution of different formations in the model, high-risk areas of tidal water pressure transmission are identified, and water-stopping strategies and construction plans are optimized.

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