Soft stratum immersed tunnel dry dock foundation pit anchor cable force prediction method and system

Abstract

The invention 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, and the method comprises the following steps: S1, collecting related data of a dry dock soft stratum, an anchor cable and a water pumping and storage circulation effect; s2, deriving a creep model of the soft stratum based on a nonlinear generalized Kelvin body model; s3, simulating and establishing an axial force relaxation model of the anchor cable according to the coupling effect of the anchor cable and the soft stratum; s4, an anchor cable axial force evolution calculation equation is constructed according to anchor cable axial force changes under the in-dock water pumping and storage circulation effect; and S5, fitting and optimizing an inherent coefficient in the axial force relaxation model according to the monitoring data of the test. An anchor cable axial force curve in the water pumping and storage disturbance process is established through anchor cable axial force changes under the water pumping and storage circulation effect, and the actual stress condition of the anchor cable is reflected more truly; and fitting and optimizing an inherent coefficient in the axial force relaxation model through monitoring data under the water pumping and storage circulation effect.

Description

Technical Field

[0001] The present invention belongs to the technical field of immersed tube tunnel engineering, and in particular relates to a method and system for predicting anchor cable forces in a dry dock foundation pit of an immersed tube tunnel in soft strata. Background Art

[0002] With the development of urban transportation construction, a large number of immersed tube tunnels have emerged to improve the efficiency of urban road traffic and optimize the traffic layout. As the prefabrication site for immersed tube tunnels, the dry dock needs to undergo key tunnel construction processes such as pipe segment prefabrication and floating out of the dock. Taking into account the clearance requirements for pipe segment prefabrication and the dense buildings around the dry dock and high environmental protection requirements, the use of anchor cables for dry dock foundation pit support has gradually become a common method. Immersed tube tunnel dry docks are often built near rivers and seas, often in deep soft soil strata, and the anchor bodies of the dry dock support anchor cables usually enter the soft strata. During long-term use, the creep deformation of the coupling system of the anchor cables and the soft strata, as well as the soft rock mudification phenomenon cannot be ignored, which can easily cause a significant relaxation of the anchor cable axial force, affecting the safety of the overall dry dock foundation pit support structure.

[0003] Most existing anchor cable health monitoring methods focus on the simple calculation of the anchor cable axial force, ignoring the influence of relaxation effect and the susceptibility of soft rock to mudification, which in turn affects the stability of the foundation pit.

[0004] Furthermore, the dry dock foundation pit requires multiple water storage and pumping operations for pipe segment floating and prefabrication, which results in a certain degree of unloading and loading of the anchor cable axial force, which also affects the evolution of the anchor cable axial force. Therefore, the influence of the pumping and storage cycle effect needs to be considered in the health monitoring and performance evaluation of anchor cables to more accurately evaluate their performance and propose targeted optimization modeling methods. Summary of the Invention

[0005] In order to solve the technical problems that the existing anchor cable health monitoring method ignores the relaxation effect and the influence of the pumped water circulation effect, the present invention provides a method and system for predicting the anchor cable force of the dry dock foundation pit of an immersed tube tunnel in soft strata.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A method for predicting anchor cable forces in a dry dock foundation pit of an immersed tube tunnel in soft strata comprises the following steps:

[0008] S1: Based on the survey data and design plan, collect relevant data on the dry dock's weak strata, anchor cables, and pumped water circulation effects;

[0009] S2: Based on the nonlinear generalized Kelvin body model, creep deformation and soft rock shale phenomenon are considered to derive the creep model of weak formations;

[0010] S3: Establish an axial force relaxation model of the cable anchor according to the coupling effect between the cable anchor and the soft formation.

[0011] S4: Adjust the boundary conditions of the axial force relaxation model of the cable anchor according to the change of the axial force of the cable anchor under the pumping and storage water circulation effect in the dry dock, and construct the calculation equation of the axial force evolution of the cable anchor.

[0012] S5: Fit and optimize the inherent coefficients in the axial force relaxation model according to the monitoring data of the test; the test is the pumping and storage water circulation effect.

[0013] Furthermore, in step S2, the non-linear generalized Kelvin body is a composite model formed by connecting a spring (Hoek body) and a non-linear Kelvin body in series; the non-linear Kelvin body is a composite model formed by connecting a spring (Hoek body) and a non-linear dashpot (Newton body) in parallel. At the same time, considering the creep of soft soil and the influence of soft rock slaking after the cable anchor's anchorage body enters the soft rock, the relevant coefficients of the model will be further corrected according to the on-site survey data.

[0014] For the soft formation where the dry dock foundation pit of the immersed tunnel is located, considering the evolution of its damping, the viscosity coefficient varying with time is:

[0015] η(t) = η0e -λt ;

[0016] In the formula, e -λt is the attenuation coefficient of the axial force of the cable anchor during the relaxation process considering the creep of soft soil and the slaking of soft rock; η0 is the viscosity coefficient under the relaxation condition considering the creep of soft soil and the slaking of soft rock.

[0017] On this basis, a non-linear creep model of the soft formation where the dry dock foundation pit of the immersed tunnel is located is constructed, and its constitutive equation is:

[0018]

[0019] In the formula, σ is the stress, is the stress rate; ε is the strain, is the strain rate; E s1 is the elastic modulus of the soft formation, E s2 is the elastic modulus of the formation considering the creep of soft soil and the slaking of soft rock when simulating creep.

[0020] Furthermore, in step S3, the coupling effect between the cable anchor and the soft formation is equivalent to a parallel structure of a non-linear generalized Kelvin body and the cable anchor. Among them, the cable anchor is equivalent to a linear elastic body, and then the constitutive equation of the coupling effect between the cable anchor and the soft formation is obtained:

[0021]

[0022] In the formula, Ec For the equivalent elastic modulus of the anchor cable considering the influence of soft soil creep and soft rock slaking, it can be calculated by E c = EA / A r where A r is the area of the rock and soil within the anchorage range of the anchor cable, E is the elastic modulus of the steel strand, and A is 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 soft stratum includes: for the constitutive equation of the coupling effect between the anchor cable and the soft stratum, when relaxation occurs, and ε = ε0 = const, then we get:

[0024]

[0025] According to the solution idea of the first-order non-homogeneous ordinary differential equation and combining with the relaxation condition, the axial force relaxation model of the anchor cable is obtained as:

[0026]

[0027] In the formula, ε0 is the strain of the soft stratum undergoing elastic deformation under the relaxation condition; C is the stress relaxation constant during the relaxation process;

[0028] After the initial tensioning, the instantaneous stress is σ0 = E c ε0 + E s1 ε0, and the expression of parameter C is obtained as,

[0029]

[0030] On this basis, the axial force change equation of the anchor cable is obtained,

[0031]

[0032] On this basis, let U = E s1 E s2 + E s1 E c + E s2 E c and V = E s1 + E s2 to obtain a simplified expression:

[0033]

[0034] In this way, according to the monitoring data of the test, the parameters U, V, and η(t) are fitted, and the modulus E s2 .

[0035] Further, the specific steps of step S4 include: adjusting the boundary conditions of the anchor cable axial force relaxation model according to the strain of the soft stratum caused by pumping or storing water in the dry dock; that is, the strain caused by the change of the anchor cable axial force is the sum of the strain tightened in the initial state and the strain caused by the increased or decreased axial force, and its expression formula is:

[0036]

[0037] In the formula, ε′0 is the strain after pumping or storing water disturbance, σ t is the stress monitoring value after disturbance, and σ(t) is the actual stress during disturbance;

[0038] Calculate the anchor cable axial force curve after disturbance, and its calculation formula is:

[0039]

[0040] In the formula, P′(t) is the anchor cable axial force after disturbance; t T is the time when pumping or storing water disturbance occurs;

[0041] Using the adjusted boundary conditions, calculate the change of the anchor cable axial force under the pumping and storing water cycle effect in the dry dock.

[0042] Further, in step S5, the inherent coefficients in the axial force relaxation model are fitted and optimized by the least square method or genetic algorithm to improve the coincidence degree between the predicted anchor cable axial force of the model and the measured data.

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

[0044] The data acquisition module is used to collect the monitoring data of the anchor cable axial force and the stress and strain of the soft stratum;

[0045] The model establishment module is used to establish a coupling effect model between the anchor cable and the soft stratum, and fit and optimize the inherent coefficients of the axial force relaxation model;

[0046] The axial force prediction module is used to calculate the change of the anchor cable axial force under the pumping and storing water cycle effect;

[0047] The health assessment module is used to evaluate the health state of the anchor cable according to the change of the anchor cable axial force and issue a warning signal.

[0048] The beneficial effects of the present invention:

[0049] 1. The time effect of the viscosity coefficient, the creep of soft soil, and the slime phenomenon prone to occur in soft rock are considered, which have an impact on the composite model of the anchor cable - soft formation. A coupling effect model of the anchor cable - soft formation based on a nonlinear viscous pot is established. By constructing a generalized nonlinear Kelvin model, the creep relaxation behavior of the formation is accurately simulated, and the accuracy of predicting the axial force of the anchor cable in the dry dock foundation pit of the immersed tunnel is improved.

[0050] 2. By considering the influence of pumping and storing water in the dry dock foundation pit of the immersed tunnel on the axial force of the anchor cable, an axial force curve of the anchor cable during the pumping and storing water disturbance process is established, which can more truly reflect the actual stress condition of the anchor cable; furthermore, the inherent coefficients in the axial force relaxation model are optimized by fitting the monitoring data under the cyclic effect of pumping and storing water.

[0051] 3. Through the modular integration of data acquisition, model establishment, axial force prediction, and health assessment, this system realizes the informatization of the performance monitoring and maintenance of the recoverable anchor cable in the dry dock foundation pit, improving the work efficiency and safety of the overall project. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0053] Figure 1 It is a curve graph of the axial force relaxation model under the cyclic effect of pumping and storing water in the method for predicting the anchor cable force in the dry dock foundation pit of the immersed tunnel in soft formation of the present invention.

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

[0055] Figure 3 It is a structural diagram of the coupling effect between the anchor cable and the soft formation in the method for predicting the anchor cable force in the dry dock foundation pit of the immersed tunnel in soft formation of the present invention.

[0056] Figure 4 It is a flowchart of the steps of the method for predicting the anchor cable force in the dry dock foundation pit of the immersed tunnel in soft formation of the present invention.

[0057] Figure 5 It is a structural framework diagram of the system for predicting the anchor cable force in the dry dock foundation pit of the immersed tunnel in soft formation of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0058] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

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

[0060] S1: According to the exploration data and design scheme, collect the relevant data of the soft strata of the dry dock, the anchor cables, and the pumping and water storage cycle effect;

[0061] S2: Based on the non-linear generalized Kelvin body model, considering the creep deformation and soft rock sludging phenomenon, deduce the creep model of the soft strata;

[0062] S3: According to the coupling effect between the anchor cables and the soft strata, simulate and establish the axial force relaxation model of the anchor cables;

[0063] S4: According to the change of the axial force of the anchor cables under the pumping and water storage cycle effect in the dry dock, adjust the boundary conditions of the axial force relaxation model of the anchor cables, and construct the calculation equation for the evolution of the axial force of the anchor cables;

[0064] S5: Fit and optimize the inherent coefficients in the axial force relaxation model according to the monitoring data of the test; the test is the pumping and water storage cycle effect.

[0065] It should be noted that since the soft strata is a viscoelastic-plastic complex, its mechanical properties are very complex, and its elastic deformation characteristics and rheological deformation characteristics have different manifestation characteristics due to different stress states. When the stress state of a rock changes, it may exhibit elastic or viscoelastic deformation characteristics. The constitutive relationship of the soft strata can be composed of a reasonable combination of these ideal models. The commonly used rheological calculation models for soft strata are the non-linear Kelvin body and the non-linear generalized Kelvin body; among them, the non-linear Kelvin body model is composed of a spring and a non-linear viscous pot in parallel; this model can describe the creep phenomenon of strain changing with time under stress. When time approaches infinity, the strain will tend to a certain finite value; this model cannot reflect the instantaneous stress relaxation phenomenon and the elastic deformation phenomenon.

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

[0067] Further, in step S2, the non-linear generalized Kelvin body is a composite model formed by connecting a spring (Hooke body) and a non-linear Kelvin body in series; the non-linear Kelvin body is a composite model formed by connecting a spring (Hooke body) and a non-linear dashpot (Newton body) in parallel. Meanwhile, to consider the creep of soft soil and the influence of the soft rock's tendency to become muddy after the anchor cable's anchoring body enters the soft rock, the relevant coefficients of the model will be further corrected according to the on-site survey data.

[0068] For the soft stratum where the dry dock foundation pit of the immersed tunnel is located, considering the evolution of its damping, the viscosity coefficient varying with time is defined as:

[0069] η(t) = η0e -λt ;

[0070] In the formula, e -λt is the attenuation coefficient of the anchor cable axial force during the relaxation process considering the creep of soft soil and the influence of the soft rock becoming muddy; η0 is the viscosity coefficient under the relaxation condition considering the creep of soft soil and the influence of the soft rock becoming muddy.

[0071] On this basis, a non-linear creep model of the soft stratum where the dry dock foundation pit of the immersed tunnel is located is constructed, and its constitutive equation is:

[0072]

[0073] In the formula, σ is the stress, is the stress rate; ε is the strain, is the strain rate; E s1 is the elastic modulus of the soft stratum, and E s2 is the elastic modulus of the stratum considering the creep of soft soil and the influence of the soft rock becoming muddy when simulating creep.

[0074] Specifically, such as Figure 2As shown, in this model, based on the property that the stress of the nonlinear Kelvin body is formed by stress superposition through the equal strain between the spring and the nonlinear dashpot and equal to the strain of the nonlinear Kelvin body, the constitutive model of the nonlinear Kelvin body can be obtained. Based on the nonlinear Kelvin body, a nonlinear generalized Kelvin body can be constructed, that is, on the basis of the nonlinear Kelvin body in the following figure, a spring is connected in series. It is composed of a spring and a nonlinear dashpot in parallel and then a spring in series. Among them, the spring simulates the elastic behavior of the formation, the nonlinear dashpot simulates the viscous behavior of the formation, and the other spring simulates the long-term creep behavior of the formation, which can be equivalent to the nonlinear generalized Kelvin model. Combining the constitutive model of the nonlinear Kelvin body and the series spring, with the overall stress being equal and the strains being added to obtain the relationship of the total strain, the constitutive equation of the creep model of the soft formation can be obtained. At the same time, to consider the influence of soft soil creep and the soft formation after the anchor cable anchor body enters the soft rock and becomes muddy, the relevant coefficients of the model will be further corrected according to the on-site survey data.

[0075] Furthermore, in step S3, the coupling effect between the anchor cable and the soft formation is equivalent to a parallel structure of a nonlinear generalized Kelvin body and the anchor cable. Among them, the anchor cable is equivalent to a linear elastic body, and then the constitutive equation of the coupling effect between the anchor cable and the soft formation is obtained:

[0076]

[0077] In the formula, E c is the equivalent elastic modulus of the anchor cable considering the influence of soft soil creep and soft rock muddification, which can be calculated by E c = EA / A r where A r is the area of the rock and soil body within the anchorage range of the anchor cable, E is the elastic modulus of the steel strand, and A is the cross-sectional area of the steel strand.

[0078] Specifically, as Figure 3 shown, for the nonlinear generalized Kelvin body, assuming that the anchor cable is a linear elastic body with an equivalent elastic modulus of E c , the anchor cable can be connected in parallel with the rock and soil body. Combining the property that the strains of the parallel nonlinear generalized Kelvin body and the linear spring body are equal and the stresses are added, the constitutive equation of the coupling effect between the anchor cable and the soft formation is obtained.

[0079] Furthermore, in step S3, the process of establishing the axial force relaxation model of the anchor cable and the soft formation includes: for the constitutive equation of the coupling effect between the anchor cable and the soft formation, when relaxation occurs, and ε = ε0 = const, then we get:

[0080]

[0081] According to the solution idea of the first-order non-homogeneous ordinary differential equation and combined with the relaxation condition, the anchor cable axial force relaxation model is obtained as follows:

[0082]

[0083] In the formula, ε0 is the strain of the soft stratum undergoing elastic deformation under the relaxation condition; C is the stress relaxation constant during the relaxation process;

[0084] After the initial tensioning, the instantaneous stress is σ0 = E c ε0 + E s1 ε0, and the expression of parameter C is obtained as

[0085]

[0086] On this basis, the equation of the change in the anchor cable axial force can be obtained.

[0087]

[0088] On this basis, let U = E s1 E s2 + E s1 E c + E s2 E c and V = E s1 + E s2 , and a simplified expression is obtained.

[0089]

[0090] In this way, according to the monitoring data of the test, the parameters U, V, and η(t) are fitted, and the modulus E of the soft stratum during simulated creep is back-calculated based on other known parameters. s2 .

[0091] In the specific implementation process, in the anchor cable axial force relaxation model, the relaxation phenomenon is manifested as follows: after the anchor cable is tensioned, due to the creep and viscous characteristics of the soft stratum, the axial force of the anchor cable will gradually relax, manifested as the attenuation of stress. Therefore, it is necessary to introduce the relaxation constant C and the attenuation coefficient λ during the relaxation process to describe the stress change. At the same time, 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 the initial tensioning, the stress of the anchor cable will gradually relax within a certain period of time and finally reach 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 describing the change in the axial force of the anchor cable depicts the attenuation process of the axial force of the anchor cable over time. Based on the axial force relaxation model, combined with the creep characteristics of the soft stratum and the linear elastic characteristics of the anchor cable, the variation law of the axial force of the anchor cable during the time process is derived. This change equation takes into account the coupling effect between the anchor cable and the soft stratum as well as the influence of the relaxation process.

[0094] Finally, through the monitoring data of the test (pumping and water storage cycle effect), parameters such as U, V, η(t), etc. are fitted using the least squares method or other optimization algorithms to ensure the consistency between the model and the measured data.

[0095] Furthermore, as Figure 1 shown, the specific steps of step S4 include: adjusting the boundary conditions of the anchor cable axial force relaxation model according to the strain of the soft stratum caused by pumping or water storage in the dry dock; that is, the strain caused by the change in the anchor cable axial force is the sum of the strain tightened in the initial state and the strain caused by the increased or decreased axial force, and its expression formula is:

[0096]

[0097] In the formula, ε′0 is the strain after pumping or water storage disturbance, σ t is the measured value of the stress after disturbance, and σ(t) is the actual stress at the time of disturbance;

[0098] Calculate the axial force curve of the anchor cable after disturbance, and its calculation formula is:

[0099]

[0100] In the formula, P′(t) is the axial force of the anchor cable after disturbance; t T is the time when the pumping or water storage disturbance occurs;

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

[0102] In the specific implementation process, due to the processes of pipe section floating transportation, prefabrication, etc. in the immersed tube tunnel dry dock foundation pit, multiple water storage and pumping operations are required, resulting in a certain degree of unloading and loading effects on the axial force of the anchor cable. The change in water level has an important impact on the stability of the foundation pit and the change in the axial force of the anchor cable. When water is stored, the water pressure on the exposed surface of the foundation pit significantly reduces the axial force of the anchor cable; after pumping, due to the disappearance of the water pressure, the axial force of the anchor cable will increase significantly. Currently, most of the existing technologies fail to consider the influence of the pumping and water storage cycle effect in the immersed tube tunnel dry dock foundation pit on the axial force of the anchor cable. Although some methods may consider the hydrological effect, most of the solutions fail to accurately model the process of water level change and do not fully reflect the disturbance caused by the water level change when calculating the axial force of the anchor cable.

[0103] Based on the stress formula after disturbance by water level changes and the equation of axial force change after disturbance by water level changes, the present invention can calculate the axial force of the anchor cable in the dry dock foundation pit of the immersed tunnel under different conditions, so as to more realistically reflect the actual stress condition of the anchor cable; furthermore, the inherent coefficient of the axial force relaxation model is optimized by fitting the monitoring data of this experiment (pumping and water storage cycle effect).

[0104] Further, in step S5, the least squares method or the genetic algorithm is used to fit and optimize the inherent coefficient in the axial force relaxation model, so as to improve the coincidence degree between the predicted axial force of the anchor cable 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 predicted value of the model and the actual measured value. The genetic algorithm (GA) is an optimization algorithm that simulates the process of natural selection and is often used to solve complex optimization problems. In step S5, the genetic algorithm is used to find the optimal inherent coefficient (including the elastic modulus, viscosity coefficient, relaxation constant, etc. of the soft stratum) in the possible parameter space. Both of these methods can effectively improve the accuracy of the axial force relaxation model prediction, thus providing reliable support for the health monitoring of the anchor cable in the project.

[0106] As Figure 5 shown, the present invention also provides a prediction system for the anchor cable force in the dry dock foundation pit of the immersed tunnel coupling soft creep and pumping and water storage effects, including a data acquisition module, a model establishment module, an axial force prediction module, and a health assessment module;

[0107] The data acquisition module is used to collect the monitoring data of the axial force of the anchor cable and the stress and strain of the soft stratum;

[0108] The model establishment module is used to establish a coupling effect model between the anchor cable and the soft stratum, and fit and optimize the inherent coefficient of the axial force relaxation model;

[0109] The axial force prediction module is used to calculate the change of the axial force of the anchor cable under the pumping and water storage cycle effect;

[0110] The health assessment module is used to evaluate the health state of the anchor cable according to the change of the axial force of the anchor cable and issue a warning signal.

[0111] In the specific implementation process, the data acquisition module is responsible for collecting in real time the monitoring data such as the axial force of the anchor cable, the stress and strain of the rock and soil layer in the dry dock foundation pit of the immersed tunnel. These data provide key inputs for subsequent model establishment, axial force prediction and health assessment. Among them, the monitoring of the axial force of the anchor cable: the axial force data of the anchor cable are collected in real time through monitoring devices such as strain gauges and stress sensors installed on the anchor cable. Monitoring of the stress and strain of the rock and soil layer: through devices such as pressure sensors, displacement gauges and strain gauges arranged in the soil layer, the stress, strain and soil body deformation of the soft stratum are monitored. The inherent coefficients such as the elastic modulus and viscosity coefficient of the soft stratum are obtained by indirect fitting of the model.

[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 changes in the axial force of the anchor cables in the immersed tube tunnel dry dock foundation pit under the effects of pumping and storage water circulation. Next, the model building module uses monitoring data from the test (the effects of pumping and storage water circulation) to calculate the strain changes in the soil layer during the pumping and storage process and inputs these changes into the axial force relaxation model. The module then optimizes the inherent coefficients of the axial force relaxation model by fitting the data from various different scenarios, thereby completing the model optimization.

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

[0114] Whether the anchor cable axial force is lower than the warning threshold;

[0115] Whether the axial force change rate exceeds the set threshold;

[0116] Whether there is a sudden change or abnormal fluctuation in the axial force;

[0117] Based on real-time monitoring of the axial forces of anchor cables in the immersed tube tunnel dry dock foundation pit, the system calculates deviations from the design values and detects any signs of excessive slack or sudden increases in axial forces. If an anomaly is detected, the assessment module issues an early warning signal, notifying engineers or maintenance personnel for inspection and intervention. This modular system not only improves prediction accuracy but also ensures adaptability and reliability under diverse operating conditions, safeguarding the long-term safety of the foundation pit.

[0118] The above content is merely an example and explanation of the structure of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the structure of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A prediction method for the anchor cable force of a dry dock foundation pit of a immersed tube tunnel in soft strata, characterized in that: It includes the following steps: S1: According to the exploration data and design scheme, collect relevant data on the soft formation of the dry dock, anchor cables, and the effect of pumping and water storage cycle. S2: Based on the non-linear generalized Kelvin body model, considering creep deformation and soft rock slaking phenomenon, derive the creep model of the soft formation. S3: According to the coupling effect between the anchor cable and the soft formation, simulate and establish the axial force relaxation model of the anchor cable. S4: According to the change of the axial force of the anchor cable under the effect of pumping and water storage cycle in the dry dock, adjust the boundary conditions of the axial force relaxation model of the anchor cable, and construct the calculation equation of the axial force evolution of the anchor cable. S5: Fit and optimize the inherent coefficient in the axial force relaxation model according to the monitoring data of the test; the test is the effect of pumping and water storage cycle.

2. The prediction method for the anchor cable force of the dry dock foundation pit of a immersed tube tunnel in soft strata according to claim 1, wherein: In step S2, the non-linear generalized Kelvin body is a composite model formed by connecting a spring and a non-linear Kelvin body in series; the non-linear Kelvin body is a composite model formed by connecting a spring and a non-linear dashpot in parallel. At the same time, to consider the creep of soft soil and the influence of soft rock slaking after the anchor body of the anchor cable enters the soft rock, the relevant coefficients of the model will be further corrected according to the on-site survey data. For the soft formation where the caisson tunnel dry dock foundation pit is located, considering the evolution of its damping, the viscosity coefficient changing with time is: η(t) = η0e -λt ; where e -λt is the attenuation coefficient of the axial force of the cable anchor during the relaxation process considering the creep of soft soil and the slaking of soft rock; η0 is the viscosity coefficient considering the creep of soft soil and the slaking of soft rock. On this basis, construct the non-linear creep model of the soft formation where the caisson tunnel dry dock foundation pit is located, and its constitutive equation is: where σ is the stress, is the stress rate; ε is the strain, is the strain rate; E s1 is the elastic modulus of the soft formation, and E s2 is the elastic modulus of the formation considering the creep of soft soil and the slaking of soft rock when simulating creep.

3. A prediction method for the anchor cable force of a dry dock foundation pit of a immersed tube tunnel in soft strata according to claim 1, characterized in that: In step S3, the coupling effect between the anchor cable and the soft formation is equivalent to a parallel structure of a non-linear generalized Kelvin body and the anchor cable. Among them, the anchor cable is equivalent to a linear elastic body, and then the constitutive equation of the coupling effect between the anchor cable and the soft formation is obtained: Wherein, E c is the equivalent elastic modulus of the anchor cable considering the influence of soft soil creep and soft rock slaking, and is calculated by E c = EA / A r where A r is the area of the rock and soil mass within the anchorage range of the anchor cable, E is the elastic modulus of the steel strand, and A is the cross-sectional area of the steel strand.

4. A prediction method for the anchor cable force of a dry dock foundation pit of a immersed tube tunnel in soft strata according to claim 1, characterized in that: In step S3, the process of establishing the axial force relaxation model of the anchor cable and the soft stratum includes: for the constitutive equation of the coupling effect between the anchor cable and the soft stratum, when relaxation occurs, and ε = ε0 = const, then we get: According to the solution idea of the first-order non-homogeneous ordinary differential equation and combining with the relaxation condition, the axial force relaxation model of the anchor cable is obtained: In the formula, ε0 is the strain of the soft formation undergoing elastic deformation under the relaxation condition; C is the stress relaxation constant during the relaxation process. After the initial tensioning, the instantaneous stress is σ0 = E c ε0 + E s1 ε0, and the expression for the parameter C is obtained as On this basis, the axial force change equation of the anchor cable is obtained. On this basis, let U = E s1 E s2 +E s1 E c +E s2 E c and V = E s1 +E s2 , to obtain the simplified expression: Thus, based on the monitoring data of the test, the parameters of U, V, and η(t) are fitted, and the modulus E during creep simulation considering soft soil creep and soft rock slaking is back-calculated according to other known parameters s2 .

5. A prediction method for the anchor cable force of a dry dock foundation pit of a immersed tube tunnel in soft strata according to claim 1, characterized in that: The specific steps of step S4 include: adjusting the boundary conditions of the axial force relaxation model of the anchor cable according to the strain of the soft formation caused by pumping or water storage in the dry dock; that is, the strain caused by the change of the axial force of the anchor cable is the sum of the strain tightened in the initial state and the strain caused by the increased or decreased axial force, and its expression formula is: where ε′0 is the strain after pumping or impounding disturbance, and σ t is the stress monitoring value after disturbance, and σ(t) is the actual stress during disturbance; Calculate the axial force curve of the anchor cable after perturbation, and its calculation formula is: Wherein, P′(t) is the axial force of the cable bolt after perturbation; t T is the time when the pumping or impounding perturbation occurs; Using the adjusted boundary conditions, calculate the change of the axial force of the anchor cable under the effect of pumping and water storage cycle in the dry dock.

6. A prediction method for the anchor cable force of a dry dock foundation pit of a immersed tube tunnel in soft strata according to claim 1, characterized in that: In step S5, fit and optimize the inherent coefficient in the axial force relaxation model by the least square method or genetic algorithm to improve the coincidence degree between the predicted axial force of the model and the measured data.

7. A prediction system for the anchor cable force of a dry dock foundation pit of a immersed tube tunnel in soft stratum, which is used to execute a prediction method for the anchor cable force of a dry dock foundation pit of an immersed tube tunnel in soft stratum according to any one of claims 1-6, characterized in that: It includes a data acquisition module, a model establishment module, an axial force prediction module, and a health assessment module; The data acquisition module is used to collect the monitoring data of the axial force of the anchor cable and the stress and strain of the soft formation. The model establishment module is used to establish the coupling effect model between the anchor cable and the soft formation, and fit and optimize the inherent coefficient of the axial force relaxation model. The axial force prediction module is used to calculate the change of the axial force of the anchor cable under the effect of pumping and water storage cycle. The health assessment module is used to evaluate the health state of the anchor cable according to the change of the axial force of the anchor cable and issue a warning signal.

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