A method and system for predicting the force of a soft ground immersed tunnel dry dock foundation pit anchor cable

Abstract

The present application belongs to the technical field of immersed tunnel engineering, and particularly relates to a soft stratum immersed tunnel dry dock foundation pit anchor cable force prediction method and system, comprising the following steps: S1: collecting relevant data of dry dock soft stratum, anchor cable and pumping and storage water circulation effect; S2: deriving a soft stratum creep model based on a nonlinear generalized Kelvin body model; S3: simulating and establishing an anchor cable axial force relaxation model according to the coupling effect of the anchor cable and the soft stratum; S4: constructing an anchor cable axial force evolution calculation equation according to the anchor cable axial force change under the pumping and storage water circulation effect; and S5: fitting and optimizing inherent coefficients in the axial force relaxation model according to test monitoring data. Through the anchor cable axial force change under the pumping and storage water circulation effect, an anchor cable axial force curve of the pumping and storage water disturbance process is established, which more truly reflects the actual stress condition of the anchor cable; and then the inherent coefficients in the axial force relaxation model are fitted and optimized through the monitoring data under the pumping and storage water circulation effect.

Description

Technical Field

[0001] This invention belongs to the field of immersed tunnel engineering technology, specifically, it relates to a method and system for predicting the anchor cable force in the dry dock foundation pit of an immersed tunnel in soft strata. Background Technology

[0002] With the development of urban transportation construction, a large number of immersed tunnels are emerging to improve urban road traffic efficiency and optimize traffic layout. Dry docks, as prefabrication yards for immersed tunnels, undergo key tunnel construction processes such as segment prefabrication and floating transport. Considering the clearance requirements for segment prefabrication and the dense surrounding buildings and high environmental protection requirements, the use of anchor cables for dry dock foundation pit support has gradually become a common practice. Immersed tunnel dry docks are often built near rivers or the sea, frequently situated in deep soft soil strata. Furthermore, the anchor bodies of the dry dock support anchor cables typically penetrate into the soft soil layer. Over long-term use, the creep deformation of the coupling system between the anchor cables and the soft soil layer, as well as the phenomenon of soft rock mudification, cannot be ignored. This can easily lead to significant relaxation of the anchor cable axial force, affecting the safety of the overall dry dock foundation pit support structure.

[0003] Existing anchor cable health monitoring methods mostly focus on the simple calculation of anchor cable axial force, ignoring the effects of relaxation effect and the easy mudification of soft rock, which in turn affects the stability of the foundation pit.

[0004] Furthermore, the dry dock foundation pit requires multiple water storage and dewatering operations due to the floating and prefabrication of pipe sections, resulting in a certain degree of unloading and loading effects on the anchor cable axial force, which also affects the evolution of the anchor cable axial force. Therefore, the impact of the water storage and dewatering cycle effect needs to be considered in the health monitoring and performance evaluation of anchor cables to more accurately assess the anchor cable performance and propose targeted optimization modeling methods. Summary of the Invention

[0005] To address the technical problems of existing anchor cable health monitoring methods neglecting the relaxation effect and the impact of pumping and water storage circulation effects, this invention provides a method and system for predicting anchor cable force in dry dock foundation pits of immersed tunnels in soft strata.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A method for predicting the anchor cable force in the dry dock foundation pit of an immersed tunnel in weak strata includes the following steps:

[0008] S1: Based on the survey data and design plan, collect relevant data on the weak strata of the dry dock, anchor cables, and the pumping and storage water circulation effect;

[0009] S2: Based on the nonlinear generalized Kelvin model, considering creep deformation and soft rock mudification, a creep model for weak strata is derived. The nonlinear generalized Kelvin is a composite model formed by connecting a spring and a nonlinear Kelvin in series; the nonlinear Kelvin is a composite model formed by connecting a spring and a nonlinear mud pot in parallel.

[0010] S3: Based on the coupling effect between the anchor cable and the weak stratum, a simulation model of the axial force relaxation of the anchor cable is established. The coupling effect between the anchor cable and the weak stratum is equivalent to a parallel structure of a nonlinear generalized Kelvin body and the anchor cable. The anchor cable is equivalent to a linear elastic body. Thus, the constitutive equation of the coupling effect between the anchor cable and the weak stratum is obtained.

[0011] S4: Based on the change of anchor cable axial force under the effect of pumping and water storage in the dock, adjust the boundary conditions of the anchor cable axial force relaxation model, that is, the strain caused by the change of anchor cable axial force is the sum of the strain of the initial tension and the strain caused by the increased or decreased axial force, and construct the calculation equation of anchor cable axial force evolution.

[0012] S5: Fit and optimize the inherent coefficients in the axial force relaxation model based on the monitoring data of the experiment; the experiment is a pumped water storage cycle effect.

[0013] Furthermore, in step S2, in order to take into account the effects of soft soil creep and the easy mudification of soft rock after the anchor cable anchor body enters the soft rock, the correlation coefficient of the model will be further corrected based on the field survey data.

[0014] For the soft strata where the dry dock pit of the immersed tunnel is located, considering the evolution of its damping, the viscosity coefficient that varies with time is defined as follows:

[0015] ;

[0016] In the formula, To account for the attenuation coefficient of anchor cable axial force during relaxation under the influence of soft soil creep and soft rock mudification; To consider the viscosity coefficient under relaxation conditions under the influence of soft soil creep and soft rock mudification;

[0017] Based on this, a nonlinear creep model of the soft strata where the dry dock pit of the immersed tunnel is located is constructed, and its constitutive equation is:

[0018] ;

[0019] In the formula, For stress, Stress rate; In response, Strain rate; The elastic modulus of the soft strata. The formation elastic modulus is calculated to account for the effects of soft soil creep and soft rock mudification when simulating creep.

[0020] Furthermore, in step S3, the constitutive equation for the coupling effect between the anchor cable and the weak strata is:

[0021] ;

[0022] In the formula, To determine the equivalent elastic modulus of the anchor cable considering the effects of soft soil creep and soft rock mudification, it can be achieved through... Calculation, where The area of ​​the soil and rock mass within the anchorage range of the anchor cable. The elastic modulus of the steel strand. This represents the cross-sectional area of ​​the steel strand.

[0023] Furthermore, in step S3, the process of establishing the axial force relaxation model of the anchor cable and the weak stratum includes: for the constitutive equation of the coupling effect between the anchor cable and the weak stratum, when relaxation occurs, and Then we get:

[0024] ;

[0025] Based on the solution approach for first-order non-homogeneous ordinary differential equations and combined with relaxation conditions, the relaxation model for anchor cable axial force is obtained as follows:

[0026] ;

[0027] In the formula, Let be the strain of the weak strata under relaxed conditions undergoing elastic deformation; C is the stress relaxation constant during the relaxation process.

[0028] After the initial tensioning, the instantaneous stress is: The expression for obtaining parameter C is:

[0029] ;

[0030] Based on this, the equation for the variation of anchor cable axial force is obtained.

[0031] ;

[0032] Based on this, let and This yields the simplified expression:

[0033] ;

[0034] Thus, based on the monitoring data from the experiment, , , The parameters are fitted, and the modulus of creep is calculated back based on other known parameters when considering soft soil creep and soft rock mudification in the weak strata. .

[0035] Furthermore, the specific steps of step S4 include: adjusting the boundary conditions of the anchor cable axial force relaxation model based on the strain of the weak strata caused by pumping or impounding water in the dock; that is, the strain caused by the change in anchor cable axial force is the sum of the strain under tension in the initial state and the strain caused by the increased or decreased axial force, expressed by the following formula:

[0036] ;

[0037] In the formula, This refers to the strain after pumping or storing water. These are the stress monitoring values ​​after the disturbance. This represents the actual stress during the disturbance.

[0038] The formula for calculating the axial force curve of the anchor cable after disturbance is as follows:

[0039] ;

[0040] In the formula, The axial force of the anchor cable after disturbance; The time when the disturbance occurs during pumping or storage;

[0041] Using the adjusted boundary conditions, the change in anchor cable axial force under the effect of water pumping and storage in the dock is calculated.

[0042] Furthermore, in step S5, the inherent coefficients in the axial force relaxation model are optimized by fitting the least squares method or genetic algorithm to improve the consistency between the anchor cable axial force predicted by the model and the measured data.

[0043] The present invention also provides a system for predicting the anchor cable force of a dry dock foundation pit for immersed tunnels in soft strata, including a data acquisition module, a model building module, an axial force prediction module, and a health assessment module;

[0044] The data acquisition module is used to collect monitoring data on anchor cable axial force and stress and strain in weak strata;

[0045] The model building module is used to build a model of the coupling effect between anchor cables and weak strata, and to fit and optimize the inherent coefficients of the axial force relaxation model.

[0046] The axial force prediction module is used to calculate the change in anchor cable axial force under the pumped water circulation effect;

[0047] The health assessment module is used to assess the health status of the anchor cable based on changes in the anchor cable axial force and to issue early warning signals.

[0048] The beneficial effects of this invention are:

[0049] 1. Considering the effects of time-dependent viscosity coefficient, soft soil creep, and the tendency of soft rock to become muddy on the anchor cable-weak stratum composite model, an anchor cable-weak stratum coupling effect model based on nonlinear viscous pots was established. By constructing a generalized nonlinear Kelvin model, the creep relaxation behavior of the stratum was accurately simulated, thereby improving the accuracy of anchor cable axial force prediction in the dry dock foundation pit of immersed tunnel.

[0050] 2. By considering the impact of water pumping and storage in the dry dock of the immersed tunnel on the axial force of the anchor cables, an axial force curve of the anchor cables during the water pumping and storage disturbance process is established, which can more realistically reflect the actual stress situation of the anchor cables; then, the inherent coefficients in the axial force relaxation model are optimized by fitting the monitoring data under the water pumping and storage cycle effect.

[0051] 3. This system, through modular integration of data acquisition, model building, axial force prediction, and health assessment, has achieved informatization of the performance monitoring and maintenance of recyclable anchor cables in dry dock foundation pits, thereby improving the overall project efficiency and safety. Attached Figure Description

[0052] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0053] Figure 1 This is a graph of the axial force relaxation model under the pumping and storage cycle effect in the anchor cable force prediction method for the dry dock foundation pit of the immersed tunnel in soft strata of the present invention.

[0054] Figure 2 This is a schematic diagram of the nonlinear generalized Kelvin model in the method for predicting anchor cable force in the dry dock foundation pit of an immersed tunnel in soft strata according to the present invention.

[0055] Figure 3 This is a structural diagram of the coupling effect between anchor cables and soft strata in the anchor cable force prediction method for the dry dock foundation pit of a immersed tunnel in soft strata according to the present invention.

[0056] Figure 4 This is a flowchart illustrating the steps of a method for predicting anchor cable force in a dry dock foundation pit of an immersed tunnel in soft strata, as described in this invention.

[0057] Figure 5 This is a structural framework diagram of a system for predicting anchor cable force in a dry dock foundation pit of an immersed tunnel in soft strata, according to the present invention. Detailed Implementation

[0058] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0059] Please see Figures 1-5 As shown, a method for predicting the anchor cable force in a dry dock foundation pit of an immersed tunnel in weak strata includes the following steps:

[0060] S1: Based on the survey data and design plan, collect relevant data on the weak strata of the dry dock, anchor cables, and the pumping and storage water circulation effect;

[0061] S2: Based on the nonlinear generalized Kelvin model, considering creep deformation and soft rock mudification, a creep model for weak strata is derived. The nonlinear generalized Kelvin is a composite model formed by connecting a spring and a nonlinear Kelvin in series; the nonlinear Kelvin is a composite model formed by connecting a spring and a nonlinear mud pot in parallel.

[0062] S3: Based on the coupling effect between the anchor cable and the weak stratum, a simulation model of the axial force relaxation of the anchor cable is established. The coupling effect between the anchor cable and the weak stratum is equivalent to a parallel structure of a nonlinear generalized Kelvin body and the anchor cable. The anchor cable is equivalent to a linear elastic body. Thus, the constitutive equation of the coupling effect between the anchor cable and the weak stratum is obtained.

[0063] S4: Based on the change of anchor cable axial force under the effect of pumping and water storage in the dock, adjust the boundary conditions of the anchor cable axial force relaxation model, that is, the strain caused by the change of anchor cable axial force is the sum of the strain of the initial tension and the strain caused by the increased or decreased axial force, and construct the calculation equation of anchor cable axial force evolution.

[0064] S5: Fit and optimize the inherent coefficients in the axial force relaxation model based on the monitoring data of the experiment; the experiment is a pumped water storage cycle effect.

[0065] It should be noted that, since weak strata are a complex mixture of viscoelastic and plastic properties, their mechanical properties are extremely complex. Their elastic and rheological deformation characteristics vary depending on the stress state. When the stress state of a rock changes, it may exhibit elastic or viscoelastic deformation characteristics. The constitutive relation of weak strata can be constructed using a reasonable combination of these ideal models. Commonly used rheological calculation models for weak strata include the nonlinear Kelvin model and the nonlinear generalized Kelvin model. The nonlinear Kelvin model consists of a spring and a nonlinear sticky pot connected in parallel. This model can describe the creep phenomenon of strain changing with time under stress; as time approaches infinity, the strain will approach a finite value. However, this model cannot reflect instantaneous stress relaxation and elastic deformation phenomena.

[0066] The nonlinear generalized Kelvin body is a composite model formed by connecting a spring (Hoek body) and a nonlinear Kelvin body in series. This model can fully reflect the viscoelastic properties. Like the Kelvin model, the strain changes with time. When time approaches infinity, the strain tends to a certain finite value.

[0067] Furthermore, in step S2, the nonlinear generalized Kelvin body is a composite model formed by connecting a spring (Hoek body) and a nonlinear Kelvin body in series; the nonlinear Kelvin body is a composite model formed by connecting a spring (Hoek body) and a nonlinear clay pot (Newton body) in parallel. At the same time, in order to consider the influence of soft soil creep and the easy mudification of soft rock after the anchor body of the anchor cable enters the soft rock, the correlation coefficient of the model will be further corrected based on the field survey data.

[0068] For the soft strata where the dry dock pit of the immersed tunnel is located, considering the evolution of its damping, the viscosity coefficient that varies with time is defined as follows:

[0069] ;

[0070] In the formula, To account for the attenuation coefficient of anchor cable axial force during relaxation under the influence of soft soil creep and soft rock mudification; To consider the viscosity coefficient under relaxation conditions under the influence of soft soil creep and soft rock mudification;

[0071] Based on this, a nonlinear creep model of the soft strata where the dry dock pit of the immersed tunnel is located is constructed, and its constitutive equation is:

[0072] ;

[0073] In the formula, For stress, Stress rate; In response, Strain rate; The elastic modulus of the soft strata. The formation elastic modulus is calculated to account for the effects of soft soil creep and soft rock mudification when simulating creep.

[0074] Specifically, such as Figure 2 As shown, in this model, the constitutive model of the nonlinear Kelvin body can be obtained by leveraging the property that the strain between the spring and the nonlinear sticky pot is equal to the strain of the nonlinear Kelvin body, and the stress superposition forms the stress of the nonlinear Kelvin body. Based on the nonlinear Kelvin body, a nonlinear generalized Kelvin body can be constructed, which is to connect a spring in series on the nonlinear Kelvin body shown in the figure below. It consists of a spring and a nonlinear sticky pot connected in parallel and then connected in series with another spring. The spring simulates the elastic behavior of the stratum, the nonlinear sticky pot simulates the viscous behavior of the stratum, and the other spring simulates the long-term creep behavior of the stratum, which can be equivalent to the nonlinear generalized Kelvin model. Combining the constitutive model of the nonlinear Kelvin body and the series spring, the overall stress is equal, and the strain is added to obtain the relationship of the overall strain. The constitutive equation of the creep model of the weak stratum can be obtained. At the same time, in order to consider the influence of soft soil creep and the soft stratum after the anchor body of the anchor cable enters the soft rock mud, the correlation coefficient of the model will be further corrected based on the field survey data.

[0075] Furthermore, in step S3, the coupling effect between the anchor cable and the weak stratum is equivalent to a parallel structure of a nonlinear generalized Kelvin body and the anchor cable, wherein the anchor cable is equivalent to a linear elastic body, thus obtaining the constitutive equation for the coupling effect between the anchor cable and the weak stratum:

[0076] ;

[0077] In the formula, To determine the equivalent elastic modulus of the anchor cable considering the effects of soft soil creep and soft rock mudification, it can be achieved through... Calculation, where The area of ​​the soil and rock mass within the anchorage range of the anchor cable. The elastic modulus of the steel strand. This represents the cross-sectional area of ​​the steel strand.

[0078] Specifically, such as Figure 3 As shown, the nonlinear generalized Kelvin body, assuming the anchor cable is a linear elastic body, has an equivalent elastic modulus of... Anchor cables can be connected in parallel with the soil and rock mass. Combining the properties of parallel nonlinear generalized Kelvin bodies and linear spring bodies where strain is equal and stress is additive, the constitutive equation for the coupling effect between anchor cables and weak strata is obtained.

[0079] Furthermore, in step S3, the process of establishing the axial force relaxation model of the anchor cable and the weak stratum includes: for the constitutive equation of the coupling effect between the anchor cable and the weak stratum, when relaxation occurs, and Then we get:

[0080] ;

[0081] Based on the solution approach for first-order non-homogeneous ordinary differential equations and combined with relaxation conditions, the relaxation model for anchor cable axial force is obtained as follows:

[0082] ;

[0083] In the formula, Let be the strain of the weak strata under relaxed conditions undergoing elastic deformation; C is the stress relaxation constant during the relaxation process.

[0084] After the initial tensioning, the instantaneous stress is: The expression for obtaining parameter C is:

[0085] ;

[0086] Based on this, the equation for the variation of anchor cable axial force can be obtained.

[0087] ;

[0088] Based on this, let and This yields a simplified expression.

[0089] ;

[0090] Thus, based on the monitoring data from the experiment, , , The parameters are fitted, and the modulus of the soft strata during simulated creep is calculated based on other known parameters. .

[0091] In practical implementation, the relaxation phenomenon in the anchor cable axial force relaxation model manifests as follows: after anchor cable tensioning, due to the creep and viscosity characteristics of weak strata, the axial force of the anchor cable gradually relaxes, resulting in stress attenuation. Therefore, a relaxation constant C and an attenuation coefficient λ during the relaxation process are needed to describe the stress change. Furthermore, based on the mechanical properties of the material, the relaxation process of the anchor cable axial force can be described by a first-order non-homogeneous ordinary differential equation.

[0092] For the relaxation constant C, after initial tensioning, the stress in the anchor cable will gradually relax over a certain period of time, eventually reaching a stable state, called the "final stress". The relaxation constant C is determined by the difference between the initial stress and the final stress.

[0093] The equation for the variation of anchor cable axial force describes the decay process of anchor cable axial force over time. Based on an axial force relaxation model and incorporating the creep characteristics of weak strata and the linear elastic properties of the anchor cable, the equation derives the variation law of anchor cable axial force over time. This equation considers the coupling effect between the anchor cable and the weak strata, as well as the influence of the relaxation process.

[0094] Finally, based on the monitoring data from the experiment (pumped-storage water circulation effect), the least squares method or other optimization algorithms were used to analyze... , , The model is fitted with parameters to ensure a good match between the model and the measured data.

[0095] Furthermore, such as Figure 1 As shown, the specific steps of step S4 include: adjusting the boundary conditions of the anchor cable axial force relaxation model based on the strain of the weak strata caused by pumping or impounding water in the dock; that is, the strain caused by the change in anchor cable axial force is the sum of the strain under tension in the initial state and the strain caused by the increased or decreased axial force, expressed by the following formula:

[0096] ;

[0097] In the formula, This refers to the strain after pumping or storing water. These are the stress monitoring values ​​after the disturbance. This represents the actual stress during the disturbance.

[0098] The formula for calculating the axial force curve of the anchor cable after disturbance is as follows:

[0099] ;

[0100] In the formula, The axial force of the anchor cable after disturbance; The time when the disturbance occurs during pumping or storage;

[0101] Using the adjusted boundary conditions, the change in anchor cable axial force under the effect of water pumping and storage in the dock is calculated.

[0102] In practical implementation, the dry dock foundation pit of immersed tunnels requires multiple water storage and dewatering operations due to the floating and prefabrication of tunnel sections, resulting in a certain degree of unloading and loading effects on the anchor cable axial force. Changes in water level have a significant impact on the stability of the foundation pit and the changes in anchor cable axial force. During water storage, the free surface of the foundation pit is subjected to water pressure, significantly reducing the anchor cable axial force; however, after dewatering, the anchor cable axial force will increase significantly due to the disappearance of water pressure. Currently, most existing technologies fail to consider the impact of the water storage and dewatering cycle effect on the anchor cable axial force of the dry dock foundation pit of immersed tunnels. Although some methods may consider hydrological effects, most schemes fail to accurately model the water level change process and do not fully reflect the disturbance caused by water level changes when calculating the anchor cable axial force.

[0103] Based on the stress formula and axial force variation equation after water level change disturbance, this invention can calculate the axial force of anchor cables in dry dock foundation pits of immersed tunnels under different conditions, thereby more realistically reflecting the actual stress situation of the anchor cables; and further optimize the inherent coefficients of the axial force relaxation model by fitting the monitoring data of this experiment (pumping and storage water circulation effect).

[0104] Furthermore, in step S5, the inherent coefficients in the axial force relaxation model are optimized by fitting the least squares method or genetic algorithm to improve the consistency between the anchor cable axial force predicted by the model and the measured data.

[0105] Specifically, the least squares method optimizes the model (i.e., the axial force relaxation model) by minimizing the error between the model's predicted values ​​and the actual measured values. The genetic algorithm (GA) is an optimization algorithm that simulates the natural selection process and is often used to solve complex optimization problems. In step S5, the genetic algorithm is used to find the optimal intrinsic coefficients (including the elastic modulus, viscosity coefficient, relaxation constant, etc. of weak strata) in the possible parameter space. Both methods can effectively improve the accuracy of the axial force relaxation model prediction, thus providing reliable support for anchor cable health monitoring in engineering.

[0106] like Figure 5 As shown, the present invention also provides a system for predicting the anchor cable force of a dry dock foundation pit for immersed tunnels that couples weak creep and water pumping, including a data acquisition module, a model building module, an axial force prediction module and a health assessment module.

[0107] The data acquisition module is used to collect monitoring data on anchor cable axial force and stress and strain in weak strata;

[0108] The model building module is used to build a model of the coupling effect between anchor cables and weak strata, and to fit and optimize the inherent coefficients of the axial force relaxation model.

[0109] The axial force prediction module is used to calculate the change in anchor cable axial force under the pumped water circulation effect;

[0110] The health assessment module is used to assess the health status of the anchor cable based on changes in the anchor cable axial force and to issue early warning signals.

[0111] In the specific implementation process, the data acquisition module is responsible for collecting real-time monitoring data such as anchor cable axial force, soil and rock layer stress, and strain in the dry dock pit of the immersed tunnel. This data provides crucial input for subsequent model building, axial force prediction, and health assessment. Specifically, anchor cable axial force monitoring involves real-time acquisition of axial force data using monitoring equipment such as strain gauges and stress sensors installed on the anchor cables. Soil and rock layer stress and strain monitoring involves monitoring the stress, strain, and soil deformation of weak strata using pressure sensors, displacement gauges, and strain gauges deployed in the soil layer. The elastic modulus, viscosity coefficient, and other inherent coefficients of the weak strata are obtained through indirect model fitting.

[0112] The model building module is responsible for establishing a model of the coupling effect between anchor cables and weak strata based on the collected data. The axial force prediction module is responsible for calculating the axial force changes of anchor cables in the dry dock foundation pit of the immersed tunnel, considering the pumping and storage cycle effect. Next, the model building module uses the monitoring data from the experiment (pumping and storage cycle effect) to calculate the strain changes of the soil layer during the pumping and storage process, and inputs these changes into the axial force relaxation model; it then combines the data under various different conditions to optimize the inherent coefficients in the axial force relaxation model, thereby completing the model optimization.

[0113] The health assessment module evaluates the health status of the anchor cables based on real-time changes in axial force in the dry dock pit of the immersed tunnel, and issues early warning signals based on the assessment results. Standards and thresholds for the health assessment are set, such as whether the anchor cable axial force is within the design range and whether the rate of axial force change is abnormal. Common assessment standards include:

[0114] Is the anchor cable axial force below the warning threshold?

[0115] Does the rate of change of axial force exceed the set threshold?

[0116] Does the axial force exhibit sudden changes or abnormal fluctuations?

[0117] Based on real-time monitoring of the axial force changes in the anchor cables of the immersed tunnel dry dock, the system calculates the deviation from the design value and detects whether there is excessive relaxation or sudden increase in axial force. If an anomaly is detected, the assessment module will issue an early warning signal to notify engineers or maintenance personnel to inspect and intervene. This modular system not only improves the accuracy of predictions but also ensures the system's adaptability and reliability under different working conditions, providing a guarantee for the long-term safety of the foundation pit.

[0118] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A method for predicting the anchor cable force in the dry dock foundation pit of an immersed tunnel in soft strata, characterized in that: Includes the following steps: S1: Based on the survey data and design plan, collect relevant data on the weak strata of the dry dock, anchor cables, and the pumping and storage water circulation effect; S2: Based on the nonlinear generalized Kelvin model, considering creep deformation and soft rock mudification, a creep model for weak strata is derived. The nonlinear generalized Kelvin model is a composite model formed by connecting a spring and a nonlinear Kelvin model in series; the nonlinear Kelvin model is a composite model formed by connecting a spring and a nonlinear mud pot in parallel. S3: Based on the coupling effect between the anchor cable and the weak stratum, a simulation model of the axial force relaxation of the anchor cable is established. The coupling effect between the anchor cable and the weak stratum is equivalent to a parallel structure of a nonlinear generalized Kelvin body and the anchor cable. The anchor cable is equivalent to a linear elastic body. Thus, the constitutive equation of the coupling effect between the anchor cable and the weak stratum is obtained. S4: Based on the change of anchor cable axial force under the effect of pumping and water storage in the dock, adjust the boundary conditions of the anchor cable axial force relaxation model, that is, the strain caused by the change of anchor cable axial force is the sum of the strain of the initial tension and the strain caused by the increased or decreased axial force, and construct the calculation equation of anchor cable axial force evolution. S5: Fit and optimize the inherent coefficients in the axial force relaxation model based on the monitoring data of the experiment; the experiment is a pumped water storage cycle effect; In step S2, to take into account the effects of soft soil creep and the easy mudification of soft rock after the anchor cable anchor body enters the soft rock, the correlation coefficient of the model will be further corrected based on the field survey data. For the soft strata where the dry dock pit of the immersed tunnel is located, considering the evolution of its damping, the viscosity coefficient changing with time is: ； In the formula, To account for the attenuation coefficient of anchor cable axial force during relaxation under the influence of soft soil creep and soft rock mudification; To account for the viscosity coefficient under the influence of soft soil creep and soft rock mudification; Based on this, a nonlinear creep model of the soft strata where the dry dock pit of the immersed tunnel is located is constructed, and its constitutive equation is: ； In the formula, For stress, Stress rate; In response, Strain rate; The elastic modulus of the soft strata. The formation elastic modulus considering the effects of soft soil creep and soft rock mudification when simulating creep; In step S3, the constitutive equation for the coupling effect between the anchor cable and the weak strata is: ； In the formula, To consider the equivalent elastic modulus of anchor cables under the influence of soft soil creep and soft rock mudification, through Calculation, where The area of ​​the soil and rock mass within the anchorage range of the anchor cable. The elastic modulus of the steel strand. This is the cross-sectional area of ​​the steel strand; In step S3, the process of establishing the axial force relaxation model of the anchor cable and the weak stratum includes: for the constitutive equation of the coupling effect between the anchor cable and the weak stratum, when relaxation occurs, and Then we get: ； Based on the solution approach for first-order non-homogeneous ordinary differential equations and combined with relaxation conditions, the relaxation model for anchor cable axial force is obtained as follows: ； In the formula, Let be the strain of the weak strata under relaxed conditions undergoing elastic deformation; C is the stress relaxation constant during the relaxation process. After the initial tensioning, the instantaneous stress is: The expression for obtaining parameter C is: ； Based on this, the equation for the variation of anchor cable axial force is obtained. ； Based on this, let and This yields the simplified expression: ； Thus, based on the monitoring data from the experiment, , , The parameters are fitted, and the modulus of creep is calculated back based on other known parameters when considering soft soil creep and soft rock mudification in the weak strata. ; Step S4 includes the following steps: adjusting the boundary conditions of the anchor cable axial force relaxation model based on the strain of the weak strata caused by pumping or impounding water in the dock; that is, the strain caused by the change in anchor cable axial force is the sum of the strain under initial tension and the strain caused by the increased or decreased axial force, expressed by the following formula: ； In the formula, This refers to the strain after pumping or storing water. These are the stress monitoring values ​​after the disturbance. This represents the actual stress during the disturbance. The formula for calculating the axial force curve of the anchor cable after disturbance is as follows: ； In the formula, The axial force of the anchor cable after disturbance; The time when the disturbance occurs during pumping or storage; Using the adjusted boundary conditions, the change in anchor cable axial force under the effect of water pumping and storage in the dock is calculated.

2. The method for predicting anchor cable force in a dry dock foundation pit of an immersed tunnel in weak strata according to claim 1, characterized in that: In step S5, the inherent coefficients in the axial force relaxation model are optimized by fitting the least squares method or genetic algorithm to improve the consistency between the anchor cable axial force predicted by the model and the measured data.

3. A system for predicting the anchor cable force in a dry dock pit of an immersed tunnel in weak strata, used to execute the method for predicting the anchor cable force in a dry dock pit of an immersed tunnel in weak strata as described in any one of claims 1-2, characterized in that: It includes a data acquisition module, a model building module, an axial force prediction module, and a health assessment module; The data acquisition module is used to collect monitoring data on anchor cable axial force and stress and strain in weak strata; The model building module is used to build a model of the coupling effect between anchor cables and weak strata, and to fit and optimize the inherent coefficients of the axial force relaxation model. The axial force prediction module is used to calculate the change in anchor cable axial force under the pumped water circulation effect; The health assessment module is used to assess the health status of the anchor cable based on changes in the anchor cable axial force and to issue early warning signals.

Images