CN-120408766-B - Weak stratum immersed tunnel dry dock foundation pit anchor cable force prediction method and system

CN120408766BCN 120408766 BCN120408766 BCN 120408766BCN-120408766-B

Abstract

The invention belongs to the technical field of immersed tube tunnel engineering, and particularly relates to a method and a system for predicting anchor cable force of a foundation pit of a dry dock of an immersed tube tunnel in a weak stratum, comprising the following steps of S1, collecting relevant data of the soft stratum of the dry dock, anchor cables and pumping and retaining cyclic effect; the method comprises the steps of S2, deducing a creep model of a weak stratum based on a nonlinear generalized Kelvin model, S3, simulating and establishing an axial force relaxation model of an anchor cable according to the coupling effect of the anchor cable and the weak stratum, S4, constructing an anchor cable axial force evolution calculation equation according to the axial force change of the anchor cable under the water pumping and storage circulation effect in a dock, and S5, fitting and optimizing inherent coefficients in the axial force relaxation model according to experimental monitoring data. The method comprises the steps of establishing an anchor cable axial force curve in the water pumping and storage disturbance process through anchor cable axial force change under the water pumping and storage circulation effect, and more truly reflecting the actual stress condition of the anchor cable, and further optimizing the inherent coefficient in the axial force relaxation model through monitoring data fitting under the water pumping and storage circulation effect.

Inventors

YANG CHUNSHAN
LIU LIYING
XI YU
Liang Jiguan
LIN ZHIWEI
YE TINGTING
OU ZHENFENG

Assignees

广州市市政工程设计研究总院有限公司

Dates

Publication Date: 20260508
Application Date: 20250320

Claims (3)

1. A method for predicting anchor cable force of a foundation pit of a soft stratum immersed tunnel dry dock is characterized by comprising the following steps: s1, collecting relevant data of weak stratum, anchor cable and pumping and water storage circulation effect of a dry dock according to investigation data and design scheme; S2, deducing a creep model of a weak stratum based on a nonlinear generalized Kelvin model by considering creep deformation and soft rock mud phenomenon, wherein the nonlinear generalized Kelvin is a composite model formed by connecting a spring and a nonlinear Kelvin in series; S3, simulating and establishing an axial force relaxation model of the anchor cable according to the coupling effect of the anchor cable and the weak stratum, wherein the coupling effect of the anchor cable and the weak stratum is equivalent to a parallel structure of a nonlinear generalized Kelvin body and the anchor cable, and the anchor cable is equivalent to a linear elastomer so as to obtain a constitutive equation of the coupling effect of the anchor cable and the weak stratum; s4, according to the change of the axial force of the anchor cable under the circulating effect of water pumping and storage in the dock, adjusting the boundary condition of an anchor cable axial force relaxation model, namely, setting the strain caused by the change of the axial force of the anchor cable as the sum of the strain tightened in the initial state and the strain caused by the increased or decreased axial force, and constructing an anchor cable axial force evolution calculation equation; s5, fitting and optimizing inherent coefficients in an axial force relaxation model according to monitoring data of a test, wherein the test is a water pumping and storage circulation effect; In step S2, in order to consider the soft soil creep and the influence of easy mud formation of the soft rock after the anchor rope anchoring body enters the soft rock, the model correlation coefficient is further corrected according to the site survey data; regarding the weak stratum where the foundation pit of the immersed tunnel is located, considering the evolution of damping, the viscosity coefficient of the immersed tunnel along with time is as follows: ; in the formula, The attenuation coefficient of the axial force of the anchor cable in the relaxation process under the influence of soft soil creep and soft rock mud is considered; to consider the viscosity coefficient under the influence of soft soil creep and soft rock mud; on the basis, a nonlinear creep model of a weak stratum where a foundation pit of a immersed tube tunnel dry dock is located is constructed, and the constitutive equation is as follows: ; in the formula, In the event of a stress being applied to the substrate, Is the stress rate; in order to be strained the material is, Is the strain rate; Is the modulus of elasticity of the weak formation, In order to simulate creep, the stratum elastic modulus of the influence of soft soil creep and soft rock sliming is considered; in step S3, the constitutive equation of the anchor cable and weak stratum coupling effect is: ; in the formula, Considering the equivalent elastic modulus of the anchor cable under the influence of soft soil creep and soft rock mud, the anchor cable is manufactured by Calculation of wherein Is the area of the rock-soil body in the anchorage range of the anchor cable, Is the elastic modulus of the steel strand, Is the cross-sectional area of the steel strand; In step S3, the axial force relaxation model of the anchor cable and the weak stratum is established by adopting the constitutive equation of the coupling effect of the anchor cable and the weak stratum, And is also provided with Then the following steps are obtained: ; according to the solving thought of the first-order non-homogeneous ordinary differential equation and combining the relaxation condition, the anchor cable axial force relaxation model is obtained as follows: ; in the formula, The stress is the stress relaxation constant in the relaxation process; after initial stretching, the instantaneous stress is The expression for the parameter C is given as, ; On the basis, the change equation of the axial force of the anchor cable is obtained, ; On the basis, let And A simplified expression is obtained: ; thus, according to the monitoring data of the test, for 、、 Fitting parameters, and back calculating modulus of weak stratum considering soft soil creep and simulated creep when soft rock is slimed according to other known parameters ; The specific step of the step S4 comprises the step of adjusting boundary conditions of an anchor cable axial force relaxation model according to weak stratum strain caused by pumping water or accumulating water in a dock, wherein the strain caused by the change of the anchor cable axial force is the sum of the strain tightened in an initial state and the strain caused by the increased or decreased axial force, and the expression formula is as follows: ; in the formula, For the strain after the disturbance of pumping or water storage, As a stress monitoring value after the disturbance, Is the actual stress at the time of disturbance; The calculation formula of the cable shaft force curve after disturbance is calculated is as follows: ; in the formula, The axial force of the anchor cable after disturbance is; the time when the disturbance of pumping water or accumulating water occurs; And calculating the axial force change of the anchor cable under the circulating effect of water pumping and storage in the dock by using the adjusted boundary condition.
2. The method for predicting anchor cable force of the foundation pit of the immersed tunnel in the weak stratum and the foundation pit is characterized in that in the step S5, inherent coefficients in an axial force relaxation model are optimized through fitting of a least square method or a genetic algorithm, and the coincidence degree of the anchor cable axial force predicted by the model and measured data is improved.
3. A weak stratum immersed tube tunnel dry dock foundation pit anchor rope force prediction system for executing the weak stratum immersed tube tunnel dry dock foundation pit anchor rope force prediction method according to any one of claims 1-2, which is characterized by comprising a data acquisition module, a model building module, an axial force prediction module and a health evaluation module; the data acquisition module is used for acquiring monitoring data of the axial force of the anchor cable and the stress and strain of the weak stratum; the model building module is used for building an anchor cable and weak stratum coupling effect model and fitting and optimizing the inherent coefficient of the axial force relaxation model; the axial force prediction module is used for calculating the axial force change of the anchor cable under the pumping and water storage circulating effect; The health evaluation module is used for evaluating the health state of the anchor cable according to the axial force change of the anchor cable and sending out an early warning signal.

Description

Weak stratum immersed tunnel dry dock foundation pit anchor cable force prediction method and system Technical Field The invention belongs to the technical field of immersed tube tunnel engineering, and particularly relates to a method and a system for predicting anchor cable force of a foundation pit of a dry dock of an immersed tube tunnel in a weak stratum. Background Along with the development of urban traffic construction, a large number of immersed tube tunnels are continuously emerging so as to improve urban road traffic efficiency and optimize traffic layout. The dry dock is used as a prefabrication field of the immersed tube tunnel, and needs to be subjected to key working procedures of tunnel construction such as prefabrication of tube joints, floating and undocking. Considering the clearance requirement of pipe joint prefabrication and the dense building surrounding the dry dock and high environmental protection requirement, the dry dock foundation pit support by adopting the anchor cable gradually becomes a common mode. The immersed tunnel dry dock is usually built in the river and the sea and is often positioned in a deep soft soil stratum, an anchor body of the dry dock supporting anchor cable usually enters a soft stratum, and in the long-term use process, creep deformation of a coupling system of the anchor cable and the soft stratum and soft rock mud phenomenon are not negligible, so that obvious looseness of the axial force of the anchor cable is easily caused, and the safety of the foundation pit supporting structure of the whole dry dock is influenced. Most of the existing anchor cable health monitoring methods pay attention to simple calculation of the axial force of the anchor cable, neglect the influence of the relaxation effect and the phenomenon of easy mud formation of soft rock, and further influence the stability of a foundation pit. In addition, the dry dock foundation pit needs to carry out water storage and water pumping operations for many times due to the links of floating transportation, prefabrication and the like of the pipe joints, so that the anchor cable shaft force has a certain unloading and loading effect, and the evolution of the anchor cable shaft force can be influenced. Therefore, in the health monitoring and performance evaluation of the anchor cable, the influence of the pumping water circulation effect is considered, so that the performance of the anchor cable is evaluated more accurately, and an optimized modeling method is provided in a targeted manner. Disclosure of Invention The invention provides a method and a system for predicting anchor cable force of a foundation pit of a soft stratum immersed tunnel dry dock, which are used for solving the technical problems that the existing anchor cable health monitoring method ignores a relaxation effect and the pumping and water storage circulation effect causes influence. The aim of the invention can be achieved by the following technical scheme: A method for predicting anchor cable force of a foundation pit of a dry dock of a soft stratum immersed tunnel comprises the following steps: s1, collecting relevant data of weak stratum, anchor cable and pumping and water storage circulation effect of a dry dock according to investigation data and design scheme; S2, deducing a creep model of a weak stratum based on a nonlinear generalized Kelvin model by considering creep deformation and soft rock mud phenomenon, wherein the nonlinear generalized Kelvin is a composite model formed by connecting a spring and a nonlinear Kelvin in series; S3, simulating and establishing an axial force relaxation model of the anchor cable according to the coupling effect of the anchor cable and the weak stratum, wherein the coupling effect of the anchor cable and the weak stratum is equivalent to a parallel structure of nonlinear generalized Kelvin bodies and the anchor cable, and the anchor cable is equivalent to a linear elastomer so as to obtain a constitutive equation of the coupling effect of the anchor cable and the weak stratum; s4, according to the change of the axial force of the anchor cable under the circulating effect of water pumping and storage in the dock, adjusting the boundary condition of an anchor cable axial force relaxation model, namely, setting the strain caused by the change of the axial force of the anchor cable as the sum of the strain tightened in the initial state and the strain caused by the increased or decreased axial force, and constructing an anchor cable axial force evolution calculation equation; and S5, fitting and optimizing inherent coefficients in the axial force relaxation model according to monitoring data of a test, wherein the test is a water pumping and storage circulation effect. Further, in step S2, in order to consider the soft soil creep and the influence of easy mud formation of the soft rock after the anchor rope anchoring body enters the soft rock, the model correlation coefficient is fu