Analysis method and system for siltation stability of foundation trench slope of submarine immersed tube tunnel

Abstract

The present invention relates to a method and system for analyzing the stability of the silting of the slope of the trench of a submarine immersed tube tunnel. The method comprises the following steps: S1, setting numerical parameters of wave flow field to construct waves, and obtaining the dynamic water pressure acting on the seabed surface inside and outside the trench of the immersed tube tunnel; S2, setting geotechnical analysis parameters of the silting layer and the trench seabed, constructing a geotechnical model of the seabed near the trench, and applying the dynamic water pressure to the seabed geotechnical model; S3, based on the geotechnical model of the seabed near the trench, using the strength reduction method for the silting layer on the seabed and the upper part of the slope, and obtaining the safety factor FOS at the most dangerous moment. 清淤前 ; S4, set different values ​​of desilting slope rate, modify the geotechnical analysis parameters of the back silt layer in step S2 accordingly, use the strength reduction method for the back silt layer on the seabed and the upper slope, and obtain the safety factor FOS at the most dangerous moment 清淤后 The present invention can quantitatively evaluate the influence of silting and desilting on the stability of the foundation trench slope in a marine environment.

Description

Technical Field

[0001] The present invention belongs to the technical field of marine engineering disaster assessment, and in particular relates to a method and system for analyzing the silting stability of a foundation trench slope of a submarine immersed tube tunnel. Background Art

[0002] The stability analysis of the submarine foundation trench slope is an important part of the design and construction of submarine immersed tube tunnels, because it directly affects the amount of earthwork excavation for underwater engineering and the amount of backfill after the immersed tube is placed. With the construction of large-scale cross-sea tunnels such as the Hong Kong-Zhuhai-Macao Bridge and the Shenzhen-Zhongshan Channel in my country, the stability of the submarine foundation trench slope under complex geological and hydraulic conditions has received more and more attention. Generally speaking, under the premise of ensuring construction safety and quality, increasing the slope rate of the excavated slope can effectively reduce the excavation volume and reduce seabed disturbance, which is beneficial to the protection of the marine ecological environment. Therefore, it has important economic and ecological significance.

[0003] In offshore engineering, after the underwater foundation trench is excavated, the forces acting on the foundation trench slope include not only the gravity of the seabed itself, but also the hydrodynamic force in the complex marine environment. Therefore, a major difference between the submarine slope and the land slope is the influence of waves and currents, which is also the reason why the slope of the natural submarine slope is significantly gentler than that of the land slope. For example, the slope angle of the Storegga landslide in Norway is 0.55°~1.32°, and the slope angle of the northern continental slope of the South my country Sea (where many landslides are developed) is 3.0°. Generally speaking, the periodic movement of the fluid in the wave will cause a pressure difference under the crest and trough, further changing the size and distribution of the pore pressure in the soil. Most of the past studies have focused on the dynamic response and stability of the horizontal seabed under wave loads. Limited by the research and evaluation methods, there are not many studies on the stability of artificial submarine (foundation trench) slopes under wave loads. Most of the existing studies focus on the slope stability under static water conditions, and the research considering the influence of wave or sea flow loads in the marine environment is very limited.

[0004] At the same time, the siltation intensity of cross-sea immersed tube tunnels is high and the drying time is long. If the siltation collapses during the construction of the cushion layer or the sinking of the immersed tube structure, it will seriously threaten the safety of the immersed tube tunnel. How to set a reasonable slope to ensure the safety of the foundation trench slope before and after silting has become a key research topic for cross-sea immersed tube tunnels. Summary of the invention

[0005] The object of the present invention is to provide a method and system for analyzing the siltation stability of a foundation trench slope of a submarine immersed tube tunnel.

[0006] In one aspect, the present invention provides a method for analyzing the stability of the slope of a subsea immersed tube tunnel foundation trench, comprising the following steps:

[0007] S1, setting numerical parameters of wave flow field to construct waves, and performing fluid dynamic analysis to obtain the dynamic water pressure acting on the seabed surface inside the immersed tube tunnel foundation trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel foundation trench;

[0008] S2, setting geotechnical analysis parameters of the siltation layer and the foundation trench seabed, constructing a geotechnical model of the seabed near the foundation trench, and applying the hydrodynamic pressure calculated in step S1 to the seabed geotechnical model;

[0009] S3, based on the seabed geotechnical model near the foundation trench, the strength reduction method is used for the seabed and the upper siltation layer of the slope to analyze the stability of the tunnel foundation trench slope and the siltation on the slope before dredging at different times, and the safety factor FOS at the most dangerous moment is obtained. 清淤前 ;

[0010] S4, set different values ​​of silt removal slope rate, modify the geotechnical analysis parameters of the silt layer in step S2 accordingly, use the strength reduction method for the silt layer on the seabed and the upper part of the slope, analyze the stability of the tunnel foundation slope and the silt on the slope after silt removal at different times, and obtain the safety factor FOS at the most dangerous time 清淤后 .

[0011] Furthermore, the method further comprises step S5, wherein different FOS values ​​obtained under different dredging slopes are obtained. 清淤后 Find a FOS that meets the specification requirements 清淤后 , and the corresponding silt removal slope rate is taken as the optimal silt removal slope rate.

[0012] In another aspect, the present invention provides a system for analyzing the stability of a subsea immersed tube tunnel foundation trench slope siltation, comprising:

[0013] The wave and flow field numerical analysis construction module is used to set the wave and flow field numerical parameters to construct waves and perform fluid dynamic analysis to obtain the dynamic water pressure acting on the seabed surface inside the immersed tube tunnel foundation trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel foundation trench;

[0014] A seabed geotechnical model building module is used to set geotechnical analysis parameters of the siltation layer and the foundation trench seabed, build a seabed geotechnical model near the foundation trench, and apply the hydrodynamic pressure calculated in step S1 to the seabed geotechnical model;

[0015] The stability analysis module before desilting is used to analyze the stability of the tunnel foundation trench slope and the silt on the slope before desilting at different times based on the seabed geotechnical model near the foundation trench, and to obtain the safety factor FOS at the most dangerous moment. 清淤前 ;

[0016] The post-dredging stability analysis module is used to set different values ​​of the dredging slope rate, modify the geotechnical analysis parameters of the silt layer in step S2 accordingly, and use the strength reduction method for the silt layer on the seabed and the upper part of the slope to analyze the stability of the tunnel foundation slope and the silt on the slope after dredging at different times, and obtain the safety factor FOS at the most dangerous moment. 清淤后 .

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The prior art can usually only consider the self-weight stress of the seabed and the hydrostatic pressure of the seawater. In addition, the present invention can also quantitatively consider the influence of the wave and current loads of the seawater overlying the seabed on the stability of the slope of the foundation trench of the submarine immersed tube tunnel, as well as the influence of the overlying seawater pressure on the seepage pressure generated in the pores inside the seabed, so as to more accurately consider the characteristics of the real marine environment.

[0019] (2) The present invention can consider three potential failure modes of the submarine foundation trench slope covered with the siltation layer, namely, the failure surface only occurs in the siltation layer overlying the foundation trench slope, the failure surface only occurs inside the original seabed slope, and the failure surface occurs simultaneously in the original seabed slope and the overlying siltation layer, and determine the most likely mode (i.e., the minimum safety factor), and use the corresponding safety factor as the final evaluation index of the siltation stability of the foundation trench slope.

[0020] (3) The present invention can respectively calculate the stability index of the slope of the foundation trench of the submarine immersed tube tunnel after the siltation of the drying trough is completed (before silting) and after the siltation is completed (before the tunnel pipe section is ready to be sunk), and performs numerical simulation more in line with the actual situation, which has strong practicality.

[0021] For other advantages of the present invention, please refer to the relevant description in the embodiment section. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0023] Figure 1 It is a flowchart of a method for analyzing the stability of the slope of a subsea immersed tube tunnel foundation trench according to an embodiment of the present invention;

[0024] FIG. 2( a ) and FIG. 2( b ) are schematic diagrams of the geometric model of the foundation trench slope of the submarine immersed tube tunnel under the action of waves and currents before and after dredging, respectively, established in an embodiment of the present invention;

[0025] Figure 3 for Figure 1 A detailed flowchart of step 2 in FIG.

[0026] Figure 4 for Figure 1 A detailed flowchart of step 3 in FIG.

[0027] Figure 5 Schematic diagram of the change of slope safety factor with the relative distance (D) between the wave crest and the slope top when the average thickness of the silt layer is 2m in an embodiment of the present invention;

[0028] Figure 6 Schematic diagram of the change of safety factor with the thickness of the siltation layer (l) in three different instability modes in the embodiment of the present invention;

[0029] 7(a), (b), (c), and (d) are schematic diagrams of landslide displacement (unit: m) of the foundation trench slope under different back-silting thicknesses in an embodiment of the present invention;

[0030] Figure 8 for Figure 1 A detailed flowchart of step 4 in FIG.

[0031] Fig. 9 Schematic diagram of the change of safety factor with the thickness of the siltation layer (l) at different desilting slopes (1:m') in the embodiment of the present invention.

[0032] Fig.10 It is a block diagram of the composition of the submarine immersed tube tunnel foundation trench slope siltation stability analysis system in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] The specific implementation of the present invention is described in detail below in conjunction with specific embodiments:

[0035] like Figure 1 As shown, this embodiment provides a method for analyzing the stability of the slope silting of a submarine immersed tube tunnel foundation trench, including the following steps:

[0036] S1, set the numerical parameters of wave flow field, including water depth, wave height, wave period, flow velocity, trench slope, trench bottom width and trench depth, to construct waves, and perform fluid dynamic analysis to obtain the dynamic water pressure acting on the seabed surface inside the immersed tube tunnel trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel trench.

[0037] The parameters used in the wave flow field analysis in the test case are shown in Table 1 below.

[0038] Table 1

[0039] parameter Numeric unit water depth 15 m Wave cycle 6 s Wave height 4 m Foundation trench depth 20 m Grade 1:5 Flow rate 0 m / s Width of base trench bottom 34 m

[0040] It should be noted that the present invention is to analyze the stability of the siltation of the bottom trench slope of the submarine immersed tube tunnel and then obtain the optimal slope so that the optimal slope can be used in actual construction. Therefore, this step is to construct waves based on the actual collected data to simulate the real environment.

[0041] In this embodiment, Flow-3D finite element software is selected for fluid dynamic analysis. In Figure 2 (a) and (b), the seabed is located below the wave propagation area. The Reynolds-averaged Navier-Stoke sequences (RANS) of fluid motion is controlled, and the free surface motion of seawater is calculated using the VOF (Volume of Fluid) method. The Flow-3D finite element software can be used to easily and quickly calculate the dynamic water pressure on the seabed surface inside the immersed tube tunnel foundation trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel foundation trench.

[0042] S2, setting geotechnical analysis parameters of the siltation layer and the foundation trench seabed, constructing a geotechnical model of the seabed near the foundation trench, and applying the hydrodynamic pressure calculated in step S1 to the seabed geotechnical model.

[0043] S3, based on the seabed geotechnical model near the foundation trench, the strength reduction method is used for the seabed and the upper siltation layer of the slope to analyze the stability of the tunnel foundation trench slope and the siltation on the slope before dredging at different times, and the safety factor FOS at the most dangerous moment is obtained. 清淤前 .

[0044] It should be noted that because the waves propagate in one direction, the "different moments" here are expressed as "different distances from the wave crest to the top of the slope."

[0045] S4, set different values ​​of silt removal slope rate, modify the geotechnical analysis parameters of the silt layer in step S2 accordingly, use the strength reduction method for the silt layer on the seabed and the upper part of the slope, analyze the stability of the tunnel foundation slope and the silt on the slope after silt removal at different times, and obtain the safety factor FOS at the most dangerous time 清淤后 .

[0046] It should be noted that this step is to simulate and analyze the impact of dredging, so only the parameters of the siltation layer are modified. By setting different values ​​of dredging slope, the siltation layer on the upper part of the slope has changed, and part of the silt has been cleared. The purpose of dredging is to facilitate the subsequent tunnel construction, because the presence of silt is not conducive to construction, so this step needs to simulate and analyze the impact of dredging.

[0047] Set different values ​​of desilting slope, and then modify the backfill layer parameters under different desilting slopes accordingly. Then use the same method as step S3 to perform strength reduction calculation to obtain the safety factor FOS at the most dangerous moment. 清淤后 Different desilting slopes will result in different FOS 清淤后 , and then find a FOS that meets the specification requirements 清淤后 The corresponding optimal dredging slope rate can be used as a guide during actual construction to reduce the amount of excavation, save costs and avoid damaging the environment.

[0048] In this embodiment, Figure 3 As shown, step S2 is specifically implemented by the following detailed steps:

[0049] S21: This embodiment uses COMSOL Multiphysics finite element software to simulate and analyze the stability of seabed rock and soil, uses Mohr-Coulomb constitutive method to describe soil behavior, and sets the calculation domain seabed width, seabed thickness, soil parameters (mainly including shear modulus, Poisson's ratio, elastic modulus, permeability coefficient, buoyancy, effective cohesion, effective internal friction angle), average thickness of silt layer, etc. Among them, the calculation domain includes silt layer and foundation trench seabed, and the soil parameters are obtained from seabed soil samples obtained on site and then obtained through indoor soil mechanics tests.

[0050] The parameters used in the geotechnical analysis of the test case are shown in Table 2 below.

[0051] Table 2

[0052]

[0053]

[0054] S22: Through the consolidation theory of saturated soil, the stress redistribution state of the seabed after the excavation of the immersed tube tunnel foundation trench is established, and this is used as the initial state of the seabed for subsequent analysis.

[0055] S23: extracting the seabed surface dynamic water pressure within the tunnel foundation trench influence range calculated in step S1, and applying it to the corresponding seabed surface within the tunnel foundation trench influence range in steps at certain time intervals to ensure that the seawater dynamic water pressure is continuous with the pore water pressure in the seabed.

[0056] S24: Darcy's law is used to calculate the seepage pressure in the pores of the porous medium seabed, and this is used as the seabed internal force required for the analysis in step S3.

[0057] The traditional strength reduction method reduces the strength of the entire slope (including the soil on the upper part of the slope). The present invention makes an improvement by using three reduction methods, namely S3-01 to S3-03, and then taking the minimum value.

[0058] Specifically, Figure 4 As shown, step S3 specifically includes the following detailed steps:

[0059] S31: The seepage pressure in step S2 is set as the seabed internal force, and it is assumed that the strength index of the original seabed slope soil remains unchanged. The strength reduction method is used to reduce the shear strength index of the backfill layer soil on the upper part of the slope. The characteristic point displacement or strain inflection point of the seabed slope is used as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment. A series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, such as Figure 5 As shown in the figure, taking the minimum safety factor as the overall stability index FOS1, it can be seen that the wave load significantly reduces the stability of the submarine slope.

[0060] S32: The seepage pressure in step S2 is set as the seabed internal force, and it is assumed that the strength index of the backfill layer soil on the slope remains unchanged. The strength reduction method is used to reduce only the shear strength index of the original seabed slope soil. A series of safety factors of the tunnel foundation slope at different times and a series of safety factors of the backfill on the slope are calculated, and the minimum safety factor is used as the overall stability factor FOS2.

[0061] S33: The seepage pressure in step S2 is set as the seabed internal force, and the shear strength index of the backfill layer soil on the upper slope and the original seabed slope soil is reduced by the strength reduction method at the same time. A series of safety factors of the tunnel foundation slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability factor FOS3.

[0062] The reduction calculation method in steps S3-02 and S3-03 is the same as that in step S3-01.

[0063] S34: Take the minimum value min (FOS1, FOS2, FOS3) as the evaluation index FOS of the siltation stability of the foundation trench slope before dredging 清淤前 .

[0064] FOS is the abbreviation of Factor of Safety, which is the safety factor. General specifications require FOS> a value, such as 1.5.

[0065] like Figure 6 As shown in the figure, the changes of safety factor with the thickness of the siltation layer (l) in three different instability modes of steps S3-01, S3-02 and S3-03 are given. 清淤前Take the minimum value among FOS1, FOS2 and FOS3. As shown in Figure 7(a), Figure 7(b), Figure 7(c) and Figure 7(d), the displacement of the seabed slope soil of the foundation trench slope under different back siltation thicknesses in this embodiment is further given (unit: m).

[0066] In this embodiment, Figure 8 As shown, step S4 is implemented by the following detailed steps:

[0067] S41: Setting different values ​​of desilting slope rates, and modifying the geotechnical analysis parameters of the back-silting layer in step S2 accordingly. Each time a desilting slope rate is set, the geotechnical analysis parameters of the back-silting layer need to be modified accordingly.

[0068] S42: Assuming that the strength index of the original seabed slope soil remains unchanged, the strength reduction method is used to reduce only the shear strength index of the backfill layer soil above the foundation trench. The characteristic point displacement or strain inflection point of the seabed slope is used as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment. The overall stability coefficient FOS1' of the tunnel foundation trench slope and the backfill on the slope after dredging is analyzed at different moments.

[0069] In this step and the subsequent steps S4-03 and S4-04, after obtaining a series of safety factors of the tunnel foundation trench slope and the silt on the slope at different times, the minimum safety factor is used as the overall stability factor index.

[0070] S43: Assuming that the strength index of the backfill layer soil at the top of the foundation pit remains unchanged, the strength reduction method is used to reduce only the shear strength index of the original seabed slope soil to obtain the overall stability coefficient FOS2' after dredging.

[0071] S44: The strength reduction method is used to simultaneously reduce the shear strength index of the backfill layer soil at the top of the foundation pit and the original seabed slope soil to obtain the overall stability coefficient FOS3' after dredging.

[0072] S45: Take the minimum value min (FOS1', FOS2', FOS3') as the evaluation index FOS of the stability of the foundation trench slope after dredging 清淤后 .

[0073] Fig. 9 The results of the variation of the safety factor with the thickness of the backfill layer (l) when dredging is carried out with different dredging slopes (1:m') are given.

[0074] like Fig.10 As shown, based on the same inventive concept, this embodiment also provides a submarine immersed tube tunnel foundation trench slope siltation stability analysis system, including:

[0075] The wave and flow field numerical analysis construction module is used to set the wave and flow field numerical parameters to construct waves and perform fluid dynamic analysis to obtain the dynamic water pressure acting on the seabed surface inside the immersed tube tunnel foundation trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel foundation trench;

[0076] A seabed geotechnical model building module is used to set geotechnical analysis parameters of the siltation layer and the foundation trench seabed, build a seabed geotechnical model near the foundation trench, and apply the hydrodynamic pressure calculated in step S1 to the seabed geotechnical model;

[0077] The stability analysis module before desilting is used to analyze the stability of the tunnel foundation trench slope and the silt on the slope before desilting at different times based on the seabed geotechnical model near the foundation trench, and to obtain the safety factor FOS at the most dangerous moment. 清淤前 ;

[0078] The post-dredging stability analysis module is used to set different values ​​of the dredging slope rate, modify the geotechnical analysis parameters of the silt layer in step S2 accordingly, and use the strength reduction method for the silt layer on the seabed and the upper part of the slope to analyze the stability of the tunnel foundation slope and the silt on the slope after dredging at different times, and obtain the safety factor FOS at the most dangerous moment. 清淤后 .

[0079] More specifically, the seabed geotechnical model building module includes:

[0080] The parameter setting submodule is used to describe the soil behavior using the Mohr-Coulomb constitutive method and set the geotechnical analysis parameters of the silt layer and the foundation trench seabed, including the seabed width, seabed thickness, soil parameters, and the average thickness of the silt layer;

[0081] The seabed initial state analysis submodule is used to establish the stress redistribution state of the seabed after the excavation of the immersed tube tunnel foundation trench through the consolidation theory of saturated soil, and use this as the initial state of the seabed;

[0082] The hydrodynamic pressure application submodule is used to extract the hydrodynamic pressure on the seabed surface within the influence range of the tunnel foundation trench, and apply it step by step to the corresponding seabed surface within the influence range of the tunnel foundation trench at a certain time interval to ensure that the seawater hydrodynamic pressure and the pore water pressure in the seabed are continuous;

[0083] The seepage pressure analysis submodule is used to calculate the seepage pressure in the pores of the porous medium seabed using Darcy's law, and use this as the seabed internal force required for analysis in step S3.

[0084] More specifically, the pre-dredging stability analysis module includes:

[0085] The first reduction analysis submodule before dredging sets the seepage pressure in step S2 as the seabed internal force, and assumes that the strength index of the original seabed slope soil remains unchanged. The strength reduction method is used to reduce only the shear strength index of the backfill layer soil on the upper part of the slope. The characteristic point displacement or strain inflection point of the seabed slope is used as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment. A series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and the minimum safety factor is used as the overall stability index FOS1;

[0086] The second reduction analysis submodule before dredging sets the seepage pressure in step S2 as the internal force of the seabed, and assumes that the strength index of the backfill layer soil on the upper part of the slope remains unchanged. The strength reduction method is used to reduce only the shear strength index of the original seabed slope soil, and a series of safety factors of the tunnel foundation slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability factor FOS2;

[0087] The third reduction analysis submodule before dredging sets the seepage pressure in step S2 as the seabed internal force, and uses the strength reduction method to simultaneously reduce the shear strength index of the backfill layer soil on the slope and the original seabed slope soil, and calculates a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope, and then uses the minimum safety factor as the overall stability factor FOS3;

[0088] The stability value submodule before dredging is used to take the minimum value of FOS1, FOS2, and FOS3 as the evaluation index FOS of the stability of the foundation trench slope before dredging. 清淤前 .

[0089] More specifically, the post-dredging stability analysis module includes:

[0090] The parameter modification submodule is used to set the desilting slope with different values ​​and modify the geotechnical analysis parameters of the silting layer in step S2 accordingly;

[0091] The first reduction analysis submodule after dredging is used to assume that the strength index of the original seabed slope soil remains unchanged, and the strength reduction method is used to reduce the shear strength index of the backfill layer soil in the upper part of the foundation trench. The characteristic point displacement or strain inflection point of the seabed slope is used as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment. A series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability factor FOS1' after dredging;

[0092] The second reduction analysis submodule after dredging is used to assume that the strength index of the backfill layer soil at the top of the foundation trench remains unchanged, and the strength reduction method is used to reduce only the shear strength index of the original seabed slope soil. A series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability factor FOS2' after dredging;

[0093] The third reduction analysis submodule after dredging is used to reduce the shear strength index of the backfill layer soil in the upper part of the foundation trench and the original seabed slope soil by using the strength reduction method, and calculate a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope, and then take the minimum safety factor as the overall stability factor FOS3' after dredging;

[0094] The post-dredging stability value submodule is used to take the minimum value among FOS1', FOS2', and FOS3' as the evaluation index FOS of the stability of the foundation trench slope after dredging. 清淤后 .

[0095] It should be noted that this system is based on the same inventive concept as the aforementioned method. For the specific implementation methods and principles of each module in the system, please refer to the relevant contents in the aforementioned method and will not be repeated here.

[0096] The above-described embodiments are only specific implementations of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications, replacements and improvements within the technical scope disclosed by the present invention, and these modifications, replacements and improvements should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for analyzing the stability of the slope of a submarine immersed tube tunnel foundation trench, characterized in that: The following steps are involved: S1, setting numerical parameters of wave flow field to construct waves, and performing fluid dynamic analysis to obtain the dynamic water pressure acting on the seabed surface inside the immersed tube tunnel foundation trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel foundation trench; S2, setting geotechnical analysis parameters of the siltation layer and the foundation trench seabed, constructing a geotechnical model of the seabed near the foundation trench, and applying the hydrodynamic pressure calculated in step S1 to the seabed geotechnical model; step S2 includes: S2-01: Mohr-Coulomb constitutive method is used to describe soil behavior, and geotechnical analysis parameters of the silt layer and the trench seabed are set, including seabed width, seabed thickness, soil parameters, and average thickness of the silt layer; S2-02: Based on the consolidation theory of saturated soil, the stress redistribution state of the seabed after the excavation of the immersed tube tunnel foundation trench is established and this is taken as the initial state of the seabed; S2-03: extracting the seabed surface dynamic water pressure within the tunnel foundation trench influence range calculated in step S1, and applying it to the corresponding seabed surface within the tunnel foundation trench influence range in steps at certain time intervals, so as to ensure that the seawater dynamic water pressure is continuous with the pore water pressure in the seabed; S2-04: Calculate the seepage pressure in the pores of the porous medium seabed using Darcy's law, and use this as the seabed internal force required for analysis in step S3; S3, based on the seabed geotechnical model near the foundation trench, the strength reduction method is used for the seabed and the upper siltation layer of the slope to analyze the stability of the tunnel foundation trench slope and the siltation on the slope before dredging at different times, and the safety factor FOS at the most dangerous moment is obtained. 清淤前 ; Step S3 comprises: S3-01: Set the seepage pressure in step S2 as the seabed internal force, and assume that the strength index of the original seabed slope soil remains unchanged. Use the strength reduction method to reduce only the shear strength index of the backfill layer soil on the upper part of the slope. Use the characteristic point displacement or strain inflection point of the seabed slope as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment. Calculate a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope, and then use the minimum safety factor as the overall stability index FOS1; S3-02: Set the seepage pressure in step S2 as the seabed internal force, and assume that the strength index of the backfill layer soil on the slope remains unchanged. Use the strength reduction method to reduce only the shear strength index of the original seabed slope soil. Calculate a series of safety factors of the tunnel foundation slope at different times and a series of safety factors of the backfill on the slope, and then use the minimum safety factor as the overall stability factor FOS2; S3-03: The seepage pressure in step S2 is set as the seabed internal force, and the shear strength index of the backfill layer soil on the upper part of the slope and the original seabed slope soil is reduced by the strength reduction method, and a series of safety factors of the tunnel foundation slope and a series of safety factors of the backfill on the slope at different times are calculated, and then the minimum safety factor is used as the overall stability factor FOS3; S3-04: Take the minimum value among FOS1, FOS2 and FOS3 as the evaluation index FOS of the stability of the foundation trench slope before dredging 清淤前 ; S4, set different values ​​of silt removal slope rate, modify the geotechnical analysis parameters of the silt layer in step S2 accordingly, use the strength reduction method for the silt layer on the seabed and the upper part of the slope, analyze the stability of the tunnel foundation slope and the silt on the slope after silt removal at different times, and obtain the safety factor FOS at the most dangerous time 清淤后 ; Step S4 comprises: S4-01: Set different values ​​of desilting slope and modify the geotechnical analysis parameters of the silting layer in step S2 accordingly; S4-02: Assuming that the strength index of the original seabed slope soil remains unchanged, the strength reduction method is used to reduce the shear strength index of the soil in the upper part of the foundation trench. The characteristic point displacement or strain inflection point of the seabed slope is used as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment. A series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and the minimum safety factor is used as the overall stability factor FOS1' after dredging; S4-03: Assuming that the strength index of the soil in the upper part of the foundation trench remains unchanged, the strength reduction method is used to reduce only the shear strength index of the original seabed slope soil, and a series of safety factors of the tunnel foundation trench slope and the silt on the slope at different times are calculated. The minimum safety factor is then used as the overall stability factor FOS2' after dredging; S4-04: The shear strength index of the soil of the upper siltation layer and the original seabed slope is reduced by the strength reduction method. A series of safety factors of the tunnel foundation slope and a series of safety factors of the siltation on the slope are calculated at different times. The minimum safety factor is then used as the overall stability factor FOS3' after dredging. S4-05: Take the minimum value among FOS1', FOS2' and FOS3' as the evaluation index FOS of the stability of the foundation trench slope after dredging 清淤后 ; S5, different FOS obtained from different desilting slope rates 清淤后 Find a FOS that meets the specification requirements 清淤后 , and the corresponding silt removal slope rate is taken as the optimal silt removal slope rate.

2. The method for analyzing the stability of the slope of a submarine immersed tube tunnel according to claim 1 is characterized in that: In step S1, the wave and flow field numerical parameters include water depth, wave height, wave period, flow velocity, foundation trench slope, foundation trench bottom width and foundation trench depth.

3. A submarine immersed tube tunnel foundation trench slope siltation stability analysis system, characterized in that: include: The wave and flow field numerical analysis construction module is used to set the wave and flow field numerical parameters to construct waves and perform fluid dynamic analysis to obtain the dynamic water pressure acting on the seabed surface inside the immersed tube tunnel foundation trench and the dynamic water pressure on the seabed surface outside the immersed tube tunnel foundation trench; The seabed geotechnical model construction module is used to set the geotechnical analysis parameters of the siltation layer and the foundation trench seabed, construct the seabed geotechnical model near the foundation trench, and apply the dynamic water pressure calculated in the wave and flow field numerical analysis construction module to the seabed geotechnical model; The seabed geotechnical model construction module includes: a parameter setting submodule, which is used to describe the soil behavior by using the Mohr-Coulomb constitutive method, and set the geotechnical analysis parameters of the siltation layer and the foundation trench seabed, including the seabed width, seabed thickness, soil parameters, and average thickness of the siltation soil layer; a seabed initial state analysis submodule, which is used to establish the stress redistribution state of the seabed after the excavation of the immersed tube tunnel foundation trench through the consolidation theory of saturated soil, and use this as the initial state of the seabed; a hydrodynamic pressure application submodule, which is used to extract the hydrodynamic pressure of the seabed surface within the influence range of the tunnel foundation trench, and apply it to the corresponding seabed surface within the influence range of the tunnel foundation trench in steps at certain time intervals to meet the continuity of the seawater hydrodynamic pressure and the pore water pressure in the seabed; a seepage pressure analysis submodule, which is used to calculate the seepage pressure in the pores of the porous medium seabed by using Darcy's law, and use this as the seabed internal force required for analysis in the stability analysis module before dredging; The stability analysis module before desilting is used to analyze the stability of the tunnel foundation trench slope and the silt on the slope before desilting at different times based on the seabed geotechnical model near the foundation trench, and to obtain the safety factor FOS at the most dangerous moment. 清淤前 ; The stability analysis module before dredging includes: a first reduction analysis submodule before dredging, which is used to assume that the strength index of the original seabed slope soil remains unchanged, set the seepage pressure in the seabed rock and soil model construction module as the seabed internal force, and use the strength reduction method to reduce only the shear strength index of the backfill layer soil on the upper part of the slope, and use the characteristic point displacement or strain inflection point of the seabed slope as the basis for judging whether the slope is unstable. The safety factor at the moment of instability is the slope safety factor at that moment, and a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability index FOS1; the second reduction analysis submodule before dredging, which is used to assume that the strength index of the backfill layer soil on the upper part of the slope remains unchanged, set the seepage pressure in the seabed rock and soil model construction module as the seabed internal force, and use the strength reduction method to reduce the shear strength index of the backfill layer soil on the upper part of the slope. The subtraction method only reduces the shear strength index of the original seabed slope soil, and calculates a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope, and then takes the minimum safety factor as the overall stability factor FOS2; the third reduction analysis submodule before dredging is used to use the strength reduction method to simultaneously reduce the shear strength index of the backfill layer soil on the upper slope and the original seabed slope soil, set the seepage pressure in the seabed geotechnical model construction module as the seabed internal force, calculate a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope, and then take the minimum safety factor as the overall stability factor FOS3; the stability value submodule before dredging is used to take the minimum value of FOS1, FOS2, and FOS3 as the evaluation index FOS of the backfill stability of the foundation trench slope before dredging 清淤前 ; The post-dredging stability analysis module is used to set different values ​​of the dredging slope rate, modify the geotechnical analysis parameters of the silt layer in the seabed geotechnical model construction module accordingly, and use the strength reduction method for the silt layer on the seabed and the upper slope to analyze the stability of the tunnel foundation slope and the silt on the slope after dredging at different times, and obtain the safety factor FOS at the most dangerous moment. 清淤后 ; The post-dredging stability analysis module includes: a parameter modification submodule, which is used to set the dredging slope rate with different values, and to modify the geotechnical analysis parameters of the back-silting layer in the seabed geotechnical model construction module accordingly; the first reduction analysis submodule after dredging, which is used to assume that the strength index of the original seabed slope soil remains unchanged, and to use the strength reduction method to reduce only the shear strength index of the back-silting layer soil in the upper part of the foundation trench, and to use the characteristic point displacement or strain inflection point of the seabed slope as the basis for judging whether the slope is unstable, and the safety factor at the moment of instability is the slope safety factor at that moment, and to calculate a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the back-silting on the slope, and then use the minimum safety factor as the overall stability factor FOS1' after dredging; the second reduction analysis submodule after dredging, which is used to assume that the strength index of the back-silting layer soil in the upper part of the foundation trench is unchanged. The strength reduction method is used to reduce the shear strength index of the original seabed slope soil, and a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability factor FOS2' after dredging; the third reduction analysis submodule after dredging is used to use the strength reduction method to reduce the shear strength index of the backfill layer soil on the upper part of the foundation trench and the original seabed slope soil at the same time, and a series of safety factors of the tunnel foundation trench slope at different times and a series of safety factors of the backfill on the slope are calculated, and then the minimum safety factor is used as the overall stability factor FOS3' after dredging; the stability value submodule after dredging is used to take the minimum value of FOS1', FOS2', and FOS3' as the evaluation index FOS of the backfill stability of the foundation trench slope after dredging 清淤后 ; Different FOS obtained from different desilting slope rates 清淤后 Find a FOS that meets the specification requirements 清淤后 , and the corresponding silt removal slope rate is taken as the optimal silt removal slope rate.

Images