Design Method for Foundation Soil Reinforcement Based on Post-Construction Settlement Control of Shield Tunnels

Abstract

This invention discloses a target design method for foundation soil reinforcement based on post-construction settlement control of shield tunnels, relating to the fields of tunnel engineering and geotechnical engineering. The method includes the following steps: considering the stress level decrease and structural damage of the surrounding strata during shield tunneling, and based on the quantitative evaluation method of soil disturbance during excavation and unloading, combined with the parameter values ​​obtained from the project overview and numerical simulation, the disturbance degree distribution of the tunnel foundation soil is obtained; based on the soil compression parameter weakening method of disturbance degree, combined with the tunnel foundation soil disturbance degree distribution and the initial soil compression parameters, the weakened soil compression parameters are obtained; the weakened soil compression parameters are substituted into the layered summation method, and it is set that the compression index and void ratio of the undisturbed soil and the remolded soil remain unchanged along the depth in the subsequent calculation process, to obtain the depth distribution of post-construction settlement of the tunnel considering shield tunneling disturbance, wherein the depth at the position where the post-construction settlement of the tunnel is 0 mm is the reinforcement depth.

Description

Technical Field

[0001] This invention relates to the fields of tunnel engineering and geotechnical engineering, particularly to a foundation soil reinforcement and control technology for shield tunnels in soft soil strata to address settlement. Specifically, it is a design method for foundation soil reinforcement targets that determines the reinforcement depth through settlement prediction. This technology is mainly applied to the construction and operation and maintenance of shield tunnels in soft soil strata, aiming to improve the stability and safety of tunnels in weak soil layers, and falls under the category of settlement control and foundation reinforcement in underground structure engineering technology. Background Technology

[0002] In soft soil strata, shield tunnels often face the challenge of excessive settlement due to their unique construction methods and the weak nature of the underlying strata. This settlement not only affects the safety of the tunnel structure but also increases long-term maintenance costs. Currently, tunnel foundation soil reinforcement typically employs methods such as sleeve valve pipe splitting grouting. However, this traditional method suffers from the problem of difficulty in precisely controlling the reinforcement range, often relying on engineering experience without theoretical guidance, leading to wasted reinforcement materials, excessive tunnel uplift, or insufficient reinforcement effect. Therefore, there is an urgent need for a precise reinforcement design method based on post-construction settlement prediction to better control the post-construction settlement of shield tunnels. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a method for designing the target reinforcement of the foundation soil based on post-construction settlement control of shield tunnels. This method comprehensively considers the different degrees of disturbance to the surrounding strata during shield tunneling and the weakening of the soil compression parameters after disturbance. The resulting target reinforcement depth of the soil beneath the tunnel has a stronger theoretical basis and higher accuracy, and has practical guiding significance for on-site construction.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for designing target reinforcement of foundation soil based on post-construction settlement control of shield tunnels includes the following steps:

[0006] Considering the decrease in stress level and structural damage of the surrounding strata during shield tunneling, the distribution of soil disturbance at the tunnel foundation is obtained based on the quantitative evaluation method of soil disturbance during excavation and unloading, combined with the project overview and the parameter values ​​obtained from numerical simulation.

[0007] Based on the soil compression parameter weakening method of disturbance degree, combined with the soil disturbance degree distribution of the tunnel foundation and the initial soil compression parameters, the weakened soil compression parameters are obtained.

[0008] Substituting the weakened soil compression parameters into the layered summation method, and assuming that the compression index and void ratio of the undisturbed soil and the remolded soil remain unchanged along the depth in the subsequent calculation process, the depth distribution of post-construction settlement of the tunnel considering the disturbance of shield tunneling is obtained, wherein the depth at the position where the post-construction settlement of the tunnel is 0 mm is the reinforcement depth.

[0009] The above-described design method for reinforcing the foundation soil based on post-construction settlement control of shield tunnels further specifies that the distribution of soil disturbance at the tunnel foundation is determined according to the following preset formula:

[0010]

[0011] In the formula, p0, p d γ represents the mean consolidation pressure of the soil before and after disturbance, respectively; η is a structural parameter; γ s For generalized shear strain; γ f The failure shear strain is μ; the Poisson's ratio of the soil is E. r1 E r2 E r3 γ represents the resilient modulus of the soil in the three principal stress directions; max ψ is the maximum shear strain; ψ is the shear dilatation angle; α is an empirical value.

[0012] The above-described design method for the reinforcement of foundation soil based on post-construction settlement control of shield tunnels further includes, in which the weakened soil compression parameter includes the apparent self-weight stress of the disturbed soil, which is determined according to the following preset formula:

[0013] p zd = (1-SDD)×p z0 ;

[0014] In the formula, SDD represents the perturbation degree; p zd p represents the apparent self-weight stress of the soil after disturbance. z0 This represents the effective self-weight stress of the soil.

[0015] The above-described design method for reinforcing the foundation soil based on post-construction settlement control of shield tunnels further includes, in which the weakened soil compression parameter includes the apparent yield stress of the disturbed soil, which is determined according to the following preset formula:

[0016] p yd = (1-SDD)×p y0 ;

[0017] In the formula, SDD represents the perturbation degree; p yd p represents the apparent yield stress of the soil after disturbance. y0 Let p be the yield stress of the soil before disturbance. y0 =1.30p z0 .

[0018] The design method for strengthening the foundation soil based on post-construction settlement control of shield tunnels, as described above, further includes the weakened soil compression parameters comprising the compression indices of the elastic segment and the remodeling segment of the disturbed soil, which are determined according to the following preset formula:

[0019] C sd = (1-SDD)×(C s -C cr )+C cr ;

[0020] C cd = (1-SDD)×(C c -C cr )+C cr ;

[0021] In the formula, SDD represents the perturbation degree; C sd C is the compression index of the elastic segment of the disturbed soil. cd C is the compression index of the plastic segment of the disturbed soil. s C is the compressibility index of the undisturbed soil elastic section. c C is the compression index of the undisturbed soil remolded section. cr To reshape the soil compression index.

[0022] The above-described design method for the reinforcement of foundation soil based on post-construction settlement control of shield tunnels further incorporates the weakened soil compression parameters into the layered summation method, and assumes that the compression index and void ratio of undisturbed soil and remolded soil remain constant along the depth during subsequent calculations. This yields the depth-based distribution of post-construction settlement considering shield tunneling disturbance, specifically:

[0023] When p z0i +Δp i ≤p ydi ,

[0024] When p z0i +Δp i >p ydi ,

[0025] In the formula, h i e 0i p z0i +Δp i and p ydi These represent the thickness, initial void ratio, post-construction effective vertical stress, and apparent yield stress of the i-th soil layer, respectively.

[0026] Compared with the prior art, the advantages of this invention are as follows:

[0027] This invention comprehensively considers the varying degrees of disturbance to the surrounding strata during tunnel boring and the weakening of soil compression parameters after disturbance. Then, based on the layered settlement method, it obtains the distribution of settlement along the depth direction of the underlying strata, thereby determining the reinforcement depth. The obtained target reinforcement depth of the underlying soil has stronger theoretical basis and higher accuracy, providing practical guidance for on-site construction.

[0028] Obviously, the present invention can achieve the following effects:

[0029] (1) Reduce the waste of reinforcement resources: By accurately predicting the settlement of the strata, the present invention can determine the reasonable depth and scope of reinforcement, ensuring that the reinforcement is limited to the area where it is actually needed, avoiding unnecessary reinforcement work, thereby reducing the waste of resources, improving construction efficiency, and reducing the overall construction cost.

[0030] (2) Effective and accurate settlement control: Based on a precise settlement prediction model and reinforcement effect assessment, this invention can effectively control the post-construction settlement of shield tunnels and ensure the accuracy of reinforcement measures. Through scientific assessment methods, the long-term stability and safety of the tunnel structure are guaranteed, the complexity and cost of later maintenance are reduced, and the service life of the tunnel is extended. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a calculation flowchart of the target design method for foundation soil reinforcement based on post-construction settlement control of shield tunnels in an embodiment of the present invention.

[0033] Figure 2 This is a schematic diagram illustrating the post-construction disturbance calculation values ​​of a shield tunnel in an embodiment of the present invention.

[0034] Figure 3 These are one-dimensional compression curves of structural soil with different degrees of disturbance in embodiments of the present invention;

[0035] Figure 4 This is a depth distribution diagram of post-construction settlement of a shield tunnel in an embodiment of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0037] Example:

[0038] It should be noted that the terms "comprising" and "having" and any variations thereof in the embodiments of the present invention are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such processes, methods, products, or devices.

[0039] Figure 1 This is a flowchart illustrating the calculation process of the target design method for foundation soil reinforcement based on post-construction settlement control of shield tunnels in this embodiment of the invention. Figure 1 As shown in the figure, the target design method for foundation soil reinforcement based on post-construction settlement control of shield tunnels according to an embodiment of the present invention may specifically include the following steps:

[0040] Step 1: Considering the decrease in stress level and structural damage of the surrounding strata during shield tunneling, based on the quantitative evaluation method of soil disturbance during excavation and unloading, and combined with the parameter values ​​obtained from the project overview and numerical simulation, the distribution of soil disturbance at the tunnel foundation is obtained.

[0041] When a tunnel boring machine (TBM) is excavating underground, it disturbs the surrounding strata. This disturbance disrupts the original structure of the soil, much like breaking up the tightly packed structure of soil particles. Once the soil structure is disrupted, its compressibility increases, meaning it is more easily compressed and deformed under pressure. This change causes consolidation settlement of the foundation beneath the tunnel after construction (post-construction settlement), which in turn leads to post-construction settlement of the tunnel structure, affecting the stability and safety of the tunnel.

[0042] A quantitative evaluation method for soil disturbance during excavation and unloading, considering stress level reduction and structural damage, is employed to calculate the degree of disturbance. In practice, it is necessary to consider specific engineering conditions, such as tunnel depth and soil characteristics, and then use numerical simulation to obtain various parameter values ​​required for the calculation, such as the soil's elastic modulus and Poisson's ratio. Using these parameters and specific calculation formulas, the distribution of soil disturbance at different locations in the tunnel foundation can be obtained.

[0043] The calculation process for the soil disturbance degree at the tunnel foundation is as follows:

[0044]

[0045] In the formula, p0, p d γ represents the average consolidation pressure of the soil before and after disturbance, respectively, which can be obtained through numerical simulation; η is a structural parameter, calculated from one-dimensional consolidation test curves; s The generalized shear strain is obtained through numerical simulation; γ f The failure shear strain is 5.3%, based on the magnitude of the failure shear strain of Ningbo clay; μ is the Poisson's ratio of the soil; E r1 E r2 E r3 γ represents the resilient modulus of the soil in the three principal stress directions, obtained through triaxial loading and unloading tests; max ψ is the maximum shear strain; ψ is the shear dilatation angle; α is an empirical value, taken as 65°.

[0046] Step 2: Based on the soil compression parameter weakening method of disturbance degree, combined with the soil disturbance degree distribution of the tunnel foundation and the initial soil compression parameters, the weakened soil compression parameters are obtained.

[0047] Tunnel boring machines (TBMs) cause soil disturbance, and the degree of disturbance (SDD) measures the extent of this disturbance. This method adjusts the original compression parameters of the soil based on the degree of disturbance, reflecting the changes in the soil's mechanical properties after disturbance. Step 1 has already obtained the distribution of soil disturbance at the tunnel foundation; the degree of disturbance varies at different locations. Simultaneously, the soil itself possesses initial compression parameters, such as the compressibility index of the undisturbed elastic segment, the compressibility index of the remolded segment, and the effective self-weight stress of the soil. Combining these two aspects of information allows for a more accurate determination of the mechanical parameters of the disturbed soil (weakened soil compression parameters).

[0048] For example, the weakened soil compression parameters include the apparent self-weight stress, apparent yield stress, and compression index of the elastic and remolded sections of the disturbed soil after disturbance.

[0049] The apparent self-weight stress of the soil after disturbance is determined according to the following preset formula:

[0050] p zd = (1-SDD)×p z0 ;

[0051] In the formula, SDD represents the perturbation degree; p zd p represents the apparent self-weight stress of the soil after disturbance. z0 This represents the effective self-weight stress of the soil.

[0052] The apparent yield stress of the soil after disturbance is determined according to the following preset formula:

[0053] p yd = (1-SDD)×p y0 ;

[0054] In the formula, SDD represents the perturbation degree; p yd p represents the apparent yield stress of the soil after disturbance. y0 Let p be the yield stress of the soil before disturbance, where p can be considered as the yield stress. y0 With effective self-weight stress p z0 It also has a linear relationship p y0 =1.30p z0 .

[0055] The compression indices of the elastic and remolded sections of the disturbed soil are determined according to the following preset formula:

[0056] C sd = (1-SDD)×(C s -C cr )+C cr ;

[0057] C cd = (1-SDD)×(C c -C cr )+C cr ;

[0058] In the formula, SDD represents the perturbation degree; C sd C is the compression index of the elastic segment of the disturbed soil. cd C is the compression index of the plastic segment of the disturbed soil. s C is the compressibility index of the undisturbed soil elastic section. c C is the compression index of the undisturbed soil remolded section. cr To reshape the soil compression index.

[0059] Step 3: Substitute the weakened soil compression parameters into the layered summation method, and set that the compression index and void ratio of the undisturbed soil and the remolded soil remain unchanged along the depth in the subsequent calculation process to obtain the depth distribution of the post-construction settlement of the tunnel considering the disturbance of shield tunneling, wherein the depth at the position where the post-construction settlement of the tunnel is 0mm is the reinforcement depth.

[0060] Substituting the weakened soil compression parameters obtained in step 2 into the layered summation method, and for simplification, assuming that the compression index and void ratio of undisturbed and remolded soil remain constant along depth in subsequent calculations, the post-construction settlement distribution along depth, considering shield tunneling disturbance, can be calculated. The depth at which the tunnel settlement reaches 0 mm is the reinforcement depth.

[0061] When p z0i +Δp i ≤p ydi ,

[0062] When p z0i +Δp i >pydi ,

[0063] In the formula, h i e 0i p z0i +Δp i and p ydi These represent the thickness, initial void ratio, post-construction effective vertical stress, and apparent yield stress of the i-th soil layer, respectively.

[0064] The target depth for soil reinforcement is the depth at which the settlement is 0 mm.

[0065] As a specific implementation example Figure 2 This is a schematic diagram illustrating the post-construction disturbance calculation values ​​of a shield tunnel in an embodiment of the present invention. Figure 3 These are one-dimensional compression curves of structural soil with different degrees of disturbance in embodiments of the present invention; Figure 4 This is a depth-based distribution diagram of post-construction settlement of a shield tunnel in an embodiment of the present invention. Figures 2 to 4 As shown.

[0066] A section of the main tunnel of a certain rail transit project was constructed using the shield tunneling method. This section is located in a weak silty soil stratum. The tunnel has an outer diameter of 8.3m, an inner diameter of 7.5m, and a total length of 111.215m. The tunnel depth is approximately 10-13m, and the underlying strata are mainly silty soil with a thickness of approximately 0-3m. The underlying soil layers can be divided into three layers: silty clay, residual sandy clay, and completely weathered granite. To accurately and quantitatively determine the reinforcement depth of the underlying strata and ensure the long-term operational safety of the shield tunnel, the "Target Design Method for Foundation Soil Reinforcement Based on Post-Construction Settlement Control of Shield Tunnels" described in this invention was adopted.

[0067] The disturbance caused to the surrounding strata by tunnel excavation is determined based on the aforementioned disturbance degree calculation method.

[0068] Based on the aforementioned method for calculating the weakening of soil compression parameters after disturbance, the weakened soil compression parameters after disturbance during shield tunnel excavation are calculated.

[0069] Based on the aforementioned layered settlement method, the cumulative settlement of the strata along the depth direction of the tunnel foundation is calculated.

[0070] Reference Figure 4 Based on the aforementioned calculation method, combined with the settlement distribution curve and the actual site conditions, the reinforcement height was determined to be 3m.

[0071] The innovation of the foundation soil reinforcement target design method based on post-construction settlement control of shield tunnels in this invention is as follows:

[0072] (1) Settlement prediction-guided reinforcement design: By predicting the settlement of the strata after the shield tunnel excavation, the optimal reinforcement depth is determined to ensure that the reinforcement area is completely consistent with the actual area that needs to be reinforced, thereby avoiding unnecessary reinforcement and reducing construction costs. Based on the accurate analysis of the disturbance range of the shield tunnel excavation, a settlement prediction model is established, which can effectively predict the possible post-construction settlement and settlement area of ​​the tunnel structure.

[0073] (2) Quantitative assessment of settlement range: An improved post-construction settlement calculation model for tunnels is adopted, taking into account the disturbance effect caused by shield tunneling, to accurately assess the settlement range and amount of the tunnel foundation. By quantitatively analyzing the changes in the compression parameters of the disturbed soil, the design of reinforcement depth is guided, making the reinforcement effect more targeted and accurate.

[0074] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0075] The above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made based on the essence of the content of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for designing target reinforcement of foundation soil based on post-construction settlement control of shield tunnels, characterized in that, Includes the following steps: Considering the stress level decrease and structural damage of the surrounding strata during shield tunneling, and based on the quantitative evaluation method of soil disturbance during excavation and unloading, combined with the parameter values ​​obtained from the project overview and numerical simulation, the soil disturbance distribution at the tunnel foundation is obtained. Specifically, the soil disturbance distribution at the tunnel foundation is determined according to the following preset formula: In the formula, p0, p d γ represents the mean consolidation pressure of the soil before and after disturbance, respectively; η is a structural parameter; γ s For generalized shear strain; γ f The failure shear strain is μ; the Poisson's ratio of the soil is E. r1 E r2 E r3 γ represents the resilient modulus of the soil in the three principal stress directions; max ψ is the maximum shear strain; α is the shear dilatation angle; α is an empirical value. Based on the soil compression parameter weakening method of disturbance degree, combined with the soil disturbance degree distribution of the tunnel foundation and the initial soil compression parameters, the weakened soil compression parameters are obtained. Substituting the weakened soil compression parameters into the layered summation method, and assuming that the compression index and void ratio of the undisturbed soil and the remolded soil remain unchanged along the depth in the subsequent calculation process, the depth distribution of post-construction settlement of the tunnel considering the disturbance of shield tunneling is obtained, wherein the depth at the position where the post-construction settlement of the tunnel is 0 mm is the reinforcement depth.

2. The method for designing the target soil reinforcement of the foundation soil based on post-construction settlement control of shield tunnels according to claim 1, characterized in that, The weakened soil compression parameters include the apparent self-weight stress of the disturbed soil, which is determined according to the following preset formula: p zd =(1-SDD)×p z0 ; In the formula, SDD represents the perturbation degree; p zd p represents the apparent self-weight stress of the soil after disturbance. z0 This represents the effective self-weight stress of the soil.

3. The method for designing the target soil reinforcement of the foundation soil based on post-construction settlement control of shield tunnels according to claim 2, characterized in that, The weakened soil compression parameters include the apparent yield stress of the disturbed soil, which is determined according to the following preset formula: p yd =(1-SDD)×p y0 ; In the formula, SDD represents the perturbation degree; p yd p represents the apparent yield stress of the soil after disturbance. y0 Let p be the yield stress of the soil before disturbance. y0 =1.30p z0 .

4. The method for designing the target soil reinforcement of the foundation soil based on post-construction settlement control of shield tunnels according to claim 3, characterized in that, The weakened soil compression parameters include the compression indices of the elastic segment and the remolded segment of the disturbed soil, which are determined according to the following preset formula: C sd =(1-SDD)×(C s -C cr )+C cr ; C cd =(1-SDD)×(C c -C cr )+C cr ; In the formula, SDD represents the perturbation degree; C sd C is the compression index of the elastic segment of the disturbed soil. cd C is the compression index of the plastic segment of the disturbed soil. s C is the compressibility index of the undisturbed soil elastic section. c C is the compression index of the undisturbed soil remolded section. cr To reshape the soil compression index.

5. The method for designing the target soil reinforcement of the foundation soil based on post-construction settlement control of shield tunnels according to claim 4, characterized in that, Substituting the weakened soil compression parameters into the layered summation method, and assuming that the compression index and void ratio of the undisturbed soil and the remolded soil remain constant along the depth in subsequent calculations, the depth-based distribution of post-construction settlement of the tunnel considering shield tunneling disturbance is obtained, specifically: When p z0i +Δp i ≤p ydi , When p z0i +Δp i >p ydi , In the formula, h i e 0i p z0i +Δp i and p ydi These represent the thickness, initial void ratio, post-construction effective vertical stress, and apparent yield stress of the i-th soil layer, respectively.

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