A method for evaluating and optimizing slurry support quality of a slurry shield

Abstract

This invention relates to a method for evaluating and optimizing the quality of slurry support in slurry shield tunneling. The method includes the following steps: 1) Establishing a program to determine whether the slurry can form a mud film; 2) Inputting parameters into the mud film formation determination program; 3) Setting boundary conditions for the slurry infiltration process; establishing a slurry infiltration evaluation index calculation program using MATLAB, inputting slurry parameters and formation parameters that can form a mud film into the program for iterative calculation, obtaining the variation patterns of multiple indicators during the slurry infiltration process in the corresponding sandy soil strata, and calculating the pressure drop; 4) Determining whether the slurry infiltration distance, sandy soil porosity, and pressure drop meet the three evaluation criteria for slurry support quality; 5) Optimizing parameters by changing the mechanical parameters of the slurry or the grouting pressure until good slurry support quality is achieved; 6) Outputting the evaluation result of good slurry support quality. This invention can more realistically reflect the grouting support mechanism and comprehensively evaluate the quality of slurry support.

Description

Technical Field

[0001] This invention belongs to the field of slurry shield tunneling slurry support, specifically relating to a method for evaluating and optimizing the quality of slurry shield tunneling slurry support. Background Technology

[0002] During tunnel construction, shield tunneling operates underground, thus not affecting surface traffic. Furthermore, even if a support failure occurs during shield tunneling, it will not significantly impact surface structures, making it widely used in tunnel construction. The unique excavation and support mode of slurry shield tunneling is increasingly being applied in tunnel construction in water-rich environments such as those crossing rivers and seas. However, during slurry shield tunneling in deep, highly permeable areas, the slurry often struggles to form a mud film, or even fails to form one at all, failing to provide effective support to the tunnel face and leading to active instability and failure. Therefore, to avoid disasters, it is necessary to predict and evaluate whether the slurry can form a mud film and the quality of its support.

[0003] Considering the infeasibility of on-site simulation and the complexity of laboratory sampling simulation, using theoretical models to study the support mechanism of mud infiltration effectively solves the above problems. However, existing mud support mechanisms lack detailed analysis of the interaction between mud particles and soil at the microscale. Most theoretical models, which consider the obstruction of fluid flow by porous media, often only consider a single variable, and the infiltration distance obtained by simple calculation models has a large error. Therefore, there is a lack of an accurate method that considers multiple variables to determine whether a mud film can form and to evaluate the support quality after grouting.

[0004] Currently, there are several methods for evaluating mud film quality. Patent CN202010220082, through indoor testing, employs a hypothetical ideal mud film concept, testing the infiltration volume of a formation under both the ideal and actual mud films, and using the ratio of these two values ​​to evaluate the quality of the mud film. However, this method is overly idealistic, and the evaluation criteria for mud film quality are relatively simplistic. Patent CN201610209931 describes a detachable mud film formation and mud film airtightness testing device. This device evaluates mud film quality by obtaining the airtightness and filtration volume through a permeation airtightness test. However, this device can detect fewer variables and cannot fully reflect the mechanism of the mud infiltration process. Summary of the Invention

[0005] This invention provides a method for evaluating and optimizing the quality of slurry support in slurry shield tunneling, which can more realistically reflect the grouting support mechanism, consider the characteristics of various variables changing with infiltration time and infiltration distance, comprehensively evaluate the quality of slurry support, and output a high-quality support evaluation result.

[0006] The technical solution of the present invention is as follows:

[0007] A method for evaluating and optimizing the quality of slurry support in slurry shield tunneling includes the following steps:

[0008] 1) Use MATLAB to establish a program to determine whether mud can form a mud film. Based on the mud particle size distribution and the average pore size of the formation, determine whether this type of mud can form a mud film in the formation.

[0009] 2) Input the mud parameters and formation parameters into the mud film formation determination program. If a mud film cannot be formed, change the mud particle size distribution or add additives to the mud to optimize it until the mud can form a mud film.

[0010] 3) Set boundary conditions for the mud infiltration process; based on Darcy's law, derive a one-dimensional deep mud infiltration theory system, which includes a calculation model for infiltration distance, a calculation model for porosity of sandy soil, a calculation model for permeability coefficient of sandy soil, a calculation model for mud infiltration velocity, a calculation model for volume fraction, a calculation model for stagnation rate of mud particles, and a calculation model for pore water pressure of sandy soil. The above calculation models are used to establish a mud infiltration evaluation index calculation program in MATLAB. The mud parameters and formation parameters that can form a mud film are input into the mud infiltration evaluation index calculation program for iterative calculation to obtain the variation law of multiple indicators during the mud infiltration process in the corresponding sandy soil, and the pressure drop is calculated.

[0011] 4) Determine whether the mud penetration distance, porosity of sandy soil layers, and pressure drop meet the three evaluation criteria for mud support quality. If they meet the criteria, the mud support quality is good; if they do not meet the criteria, the mud support quality is poor.

[0012] 5) When the quality of mud support is poor, change the mechanical parameters of the mud or the grouting pressure to optimize the parameters, and repeat the above steps 1)-4) until the quality of mud support is good.

[0013] 6) Output evaluation results showing good quality of mud support.

[0014] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry support for slurry shield tunneling, the formula for the judgment procedure in step 1) is as follows:

[0015]

[0016] In the formula, d 85 D represents the size of sand particles that make up more than 85% of the total particles. p This represents the average pore size of the soil; if the formula is met, the mud can form a mud film; if the formula is not met, the mud cannot form a mud film.

[0017] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry support in slurry shield tunneling, step 3) includes a permeability distance calculation model comprising a formula for calculating the maximum slurry permeability distance and a formula for calculating the permeability distance over time; the formula for calculating the maximum permeability distance is as follows:

[0018]

[0019] In the formula, L max Indicates the maximum penetration distance of the mud; Δp represents the difference between mud pressure and hydrostatic pressure; d 10 The particle size represents the cumulative distribution of sand particles at 10%; α represents the fitting coefficient range α∈(2,4); τ represents the mud yield stress;

[0020] The formula for calculating the change in penetration distance over time is as follows:

[0021]

[0022] In the formula, x represents the mud penetration distance; t represents the mud penetration time; k′ w L represents the permeability coefficient of saturated sandy soil; n represents the porosity of sandy soil; L s Indicates the thickness of the sand sample; Indicates the difference in water head between the surface and bottom of the sand layer via the piezometer; k b This represents the permeability coefficient of mud in sandy soil layers.

[0023] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry support for slurry shield tunneling, the formula for calculating the porosity of sandy soil strata in step 3) is as follows:

[0024] n = n0 - C r

[0025] In the formula, n represents the porosity of the sandy soil layer; n0 represents the initial porosity of the sandy soil layer before the start of mud infiltration; C r This represents the stagnation rate of bentonite particles within a micro-element, that is, the volume of bentonite particles stagnating in a unit volume of mud.

[0026] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry shield tunneling support, the formula for calculating the permeability of sandy soil strata in step 3) is as follows:

[0027]

[0028] In the formula, k represents the permeability coefficient of the sandy soil layer; w μ represents the permeability coefficient of sandy soil to water. w μ and μ represent the dynamic viscosity coefficients of water and mud, respectively;

[0029] The formula for calculating mud permeability is as follows:

[0030]

[0031] In the formula, f sg The stagnation gradient of the mud (kPa / m); ρ w denoted by ρ, where ρ represents the density of water inside the porous media element; g represents the acceleration due to gravity; x represents the mud penetration distance; p represents the pore water pressure within the porous media element; and v is the macroscopic penetration velocity of the mud suspension inside the porous media element.

[0032] The formula for calculating volume fraction is as follows:

[0033]

[0034] In the formula, C s λ represents the volume fraction of liquid in the mud suspension inside the porous media micro-element; λ represents the filtration coefficient of the porous media infiltration zone; t represents the mud infiltration time.

[0035] The formula for calculating the stagnation rate of mud particles is as follows:

[0036]

[0037] In the formula, C r This indicates the retention rate of mud particles, which is the volume of bentonite particles that remain in a unit volume of mud.

[0038] The formula for calculating pore water pressure in sandy soil strata is as follows:

[0039]

[0040] In the formula, μ s C represents the water storage coefficient of porous media. w =1-C s .

[0041] Furthermore, the evaluation and optimization method for the quality of slurry support in slurry shield tunneling includes three evaluation criteria for slurry support quality:

[0042]

[0043] n<0.3

[0044] Δp′>80%p0

[0045] In the formula, D represents the diameter of the tunnel; The internal friction angle of the sandy soil layer is represented by Δp′; the pressure drop is represented by p0; and the grouting pressure is represented by p0.

[0046] The formula for calculating pressure drop is as follows:

[0047] Δp′=p1-p0

[0048] In the formula, p1 represents the pore water pressure 1 cm behind the working face.

[0049] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry support for slurry shield tunneling, the slurry parameters include: slurry gradation, slurry yield strength, slurry particle density, slurry mass concentration, and slurry viscosity; the formation parameters include: porosity of sandy soil formations, permeability coefficient of formations, filtration coefficient of formations, and water storage coefficient of formations; and the mechanical parameters of the slurry include: viscosity, consistency, and concentration.

[0050] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry support for slurry shield tunneling, the boundary conditions include: grouting pressure, infiltration time, and initial volume fraction of the slurry.

[0051] Furthermore, in the method for evaluating and optimizing the quality of slurry support for slurry shield tunneling, the additives include: CMC, PA, PAC, or PHPA.

[0052] Furthermore, in the aforementioned method for evaluating and optimizing the quality of slurry support in slurry shield tunneling, the results of the iterative calculations include: slurry penetration distance, pore water pressure in sandy soil layers, slurry penetration velocity, porosity of sandy soil layers, permeability coefficient of sandy soil layers, volume fraction of slurry particles, and stagnation rate of slurry particles; the evaluation results for good slurry support quality include: the law of change of slurry penetration distance over time; and the laws of change of pore water pressure, slurry penetration velocity, porosity, permeability coefficient, volume fraction of slurry particles, and stagnation rate of slurry particles over time and penetration distance in sandy soil layers.

[0053] The beneficial effects of this invention are as follows:

[0054] 1. Currently, the main methods for evaluating mud film quality are through indoor permeation column tests and mud film air tightness tests. This invention is a theoretical calculation method, which is more convenient and faster.

[0055] 2. The theory used takes into account a variety of variables, which can more accurately reflect the real process of mud infiltration and can detect parameters that cannot be detected in laboratory tests in real time, such as mud retention rate and mud permeability coefficient.

[0056] 3. By comprehensively considering the three evaluation criteria for the quality of mud support, the quality evaluation is more rigorous and precise.

[0057] 4. You can optimize the mud parameters based on the returned prompts. Attached Figure Description

[0058] Figure 1A flowchart for evaluating and optimizing the quality of mud support in slurry shield tunneling.

[0059] Figure 2 This is the Lt curve diagram of the mud infiltration process;

[0060] Figure 3 The PT curve of the mud infiltration process;

[0061] Figure 4 This is an NT curve diagram of the mud infiltration process. Detailed Implementation

[0062] A method for evaluating and optimizing the quality of slurry support in slurry shield tunneling includes the following steps:

[0063] 1) Develop a MATLAB program to determine whether mud can form a mud film. Based on the mud particle size distribution and the average pore size of the formation, determine whether this type of mud can form a mud film in the formation. The formula for the determination program is as follows:

[0064]

[0065] In the formula, d 85 D represents the size of sand particles that make up more than 85% of the total particles. p This represents the average pore size of the soil; if the formula is met, the mud can form a mud film; if the formula is not met, the mud cannot form a mud film.

[0066] 2) Input the mud parameters and formation parameters into the mud film formation determination program. The mud parameters include: mud gradation, mud yield strength, mud particle density, mud slurry mass concentration, and mud viscosity. The formation parameters include: sandy soil porosity, formation permeability coefficient, formation filtration coefficient, and formation water storage coefficient. If a mud film cannot be formed, the mud particle gradation is changed or additives are added to the mud to optimize it until a mud film can be formed. The additives include: CMC, PA, PAC, or PHPA.

[0067] 3) Set boundary conditions for the mud infiltration process, including: mud injection pressure, infiltration time, and initial volume fraction; based on Darcy's law, derive a one-dimensional deep mud infiltration theory system, which includes calculation models for infiltration distance, sandy soil porosity, sandy soil permeability coefficient, mud infiltration velocity, volume fraction, mud particle stagnation rate, and sandy soil pore water pressure. Establish a mud infiltration evaluation index calculation program using MATLAB. Input the mud parameters and formation parameters that can form a mud film into the mud infiltration evaluation index calculation program for iterative calculation. The results of the iterative calculation include: mud infiltration distance, sandy soil pore water pressure, mud infiltration velocity, sandy soil porosity, sandy soil permeability coefficient, mud particle volume fraction, and mud particle stagnation rate; derive the variation law of multiple indicators during the mud infiltration process in the corresponding sandy soil layer, and calculate the pressure drop;

[0068] The permeability distance calculation model includes formulas for calculating the maximum permeability distance of mud and formulas for calculating the permeability distance over time; the formula for calculating the maximum permeability distance is as follows:

[0069]

[0070] In the formula, L max Indicates the maximum penetration distance of the mud; Δp represents the difference between mud pressure and hydrostatic pressure; d 10 The particle size represents the cumulative distribution of sand particles at 10%; α represents the fitting coefficient range α∈(2,4); τ represents the mud yield stress;

[0071] The formula for calculating the change in penetration distance over time is as follows:

[0072]

[0073] In the formula, x represents the mud penetration distance; t represents the mud penetration time; k w L represents the permeability coefficient of saturated sandy soil; n represents the porosity of sandy soil; L s Indicates the thickness of the sand sample; Indicates the difference in water head between the surface and bottom of the sand layer via the piezometer; k b This represents the permeability coefficient of mud in sandy soil layers;

[0074] The formula for calculating the porosity of sandy soil strata is as follows:

[0075] n = n0 - C r

[0076] In the formula, n represents the porosity of the sandy soil layer; n0 represents the initial porosity of the sandy soil layer before the start of mud infiltration; C rIt represents the stagnation rate of bentonite particles within a micro-element, that is, the volume of bentonite particles stagnating in a unit volume of mud.

[0077] The formula for calculating the permeability of sandy soil layers is as follows:

[0078]

[0079] In the formula, k represents the permeability coefficient of the sandy soil layer; w μ represents the permeability coefficient of sandy soil to water. w μ and μ represent the dynamic viscosity coefficients of water and mud, respectively;

[0080] The formula for calculating mud permeability is as follows:

[0081]

[0082] In the formula, f sg The stagnation gradient of the mud (kPa / m); ρ w denoted by ρ, where ρ represents the density of water inside the porous media element; g represents the acceleration due to gravity; x represents the mud penetration distance; p represents the pore water pressure within the porous media element; and v is the macroscopic penetration velocity of the mud suspension inside the porous media element.

[0083] The formula for calculating volume fraction is as follows:

[0084]

[0085] In the formula, C s λ represents the volume fraction of liquid in the mud suspension inside the porous media micro-element; λ represents the filtration coefficient of the porous media infiltration zone; t represents the mud infiltration time.

[0086] The formula for calculating the stagnation rate of mud particles is as follows:

[0087]

[0088] In the formula, C r This indicates the retention rate of mud particles, which is the volume of bentonite particles that remain in a unit volume of mud.

[0089] The formula for calculating pore water pressure in sandy soil strata is as follows:

[0090]

[0091] In the formula, μ s C represents the water storage coefficient of porous media. w =1-C s ;

[0092] 4) Determine whether the mud penetration distance, porosity of sandy soil layers, and pressure drop meet the three evaluation criteria for mud support quality. If they meet the criteria, the mud support quality is good; if they do not meet the criteria, the mud support quality is poor.

[0093] The three evaluation criteria for mud support quality are:

[0094]

[0095] n<0.3

[0096] Δp′>80%p0

[0097] In the formula, D represents the diameter of the tunnel; The internal friction angle of the sandy soil layer is represented by Δp′; the pressure drop is represented by p0; and the grouting pressure is represented by p0.

[0098] The formula for calculating pressure drop is as follows:

[0099] Δp′=p1-p0

[0100] In the formula, p1 represents the pore water pressure 1 cm behind the working face;

[0101] 5) When the quality of mud support is poor, optimize the parameters by changing the mechanical parameters of the mud or the grouting pressure. The mechanical parameters of the mud include: viscosity, consistency, and concentration. Repeat steps 1)-4) above until the quality of mud support is good.

[0102] 6) Output evaluation results showing good mud support quality; such as Figure 2-4 As shown, the evaluation results of good mud support quality include: the law of change of mud penetration distance over time; the law of change of pore water pressure, mud penetration velocity, porosity, permeability coefficient, volume fraction of mud particles, and stagnation rate of mud particles over time and penetration distance in sandy soil strata.

Claims

1. A method for evaluating and optimizing the quality of slurry support in slurry shield tunneling, characterized in that, Includes the following steps: 1) Use MATLAB to establish a program to determine whether mud can form a mud film. Based on the mud particle size distribution and the average pore size of the formation, determine whether this type of mud can form a mud film in the formation. 2) Input the mud parameters and formation parameters into the mud film formation determination program. If a mud film cannot be formed, change the mud particle size distribution or add additives to the mud to optimize it until the mud can form a mud film. 3) Set boundary conditions for the mud infiltration process; based on Darcy's law, derive a one-dimensional deep mud infiltration theory system. This system includes models for calculating infiltration distance, porosity of sandy soil layers, permeability coefficient of sandy soil layers, mud infiltration velocity, volume fraction, stagnation rate of mud particles, and pore water pressure in sandy soil layers. These models are used to establish a mud infiltration evaluation index calculation program in MATLAB. Mud parameters and formation parameters that can form a mud film are input into the program for iterative calculation to obtain the variation patterns of multiple indicators during mud infiltration in the corresponding sandy soil layers, and the pressure drop is calculated. The infiltration distance calculation model includes formulas for calculating the maximum infiltration distance and the infiltration distance over time. The formula for calculating the maximum infiltration distance is as follows: In the formula, Indicates the maximum penetration distance of the mud; This indicates the difference between mud pressure and hydrostatic pressure; This indicates the particle size at which 10% of the sand particles are cumulatively distributed. Indicates the range of values ​​for the fitting coefficients. ; Indicates the yield stress of the mud; The formula for calculating the change in penetration distance over time is as follows: In the formula, x represents the mud penetration distance; Indicates mud infiltration time; Indicates the permeability coefficient of saturated sandy soil layers; Indicates the porosity of sandy soil layers; Indicates the thickness of the sand sample; This indicates the difference in water head between the surface and bottom of the sand layer via the piezometer. This represents the permeability coefficient of mud in sandy soil layers; 4) Determine whether the mud penetration distance, porosity of the sandy soil layer, and pressure drop meet the three evaluation criteria for mud support quality. If they meet the criteria, the mud support quality is good; otherwise, the mud support quality is poor. The three evaluation criteria for mud support quality are: In the formula, Indicates the diameter of the tunnel; Indicates the internal friction angle of sandy soil layers; This indicates a decrease in pressure; Indicates the grouting pressure; The formula for calculating pressure drop is as follows: In the formula, This indicates the pore water pressure 1 cm behind the working face; 5) When the quality of mud support is poor, change the mechanical parameters of the mud or the grouting pressure to optimize the parameters, and repeat the above steps 1)-4) until the quality of mud support is good. 6) Output evaluation results showing good quality of mud support.

2. The method for evaluating and optimizing the quality of slurry support for slurry shield tunneling as described in claim 1, characterized in that, In step 1), the formula for determining the program is as follows: In the formula, This indicates the size of sand particles that make up more than 85% of the total particles. This represents the average pore size of the soil; if the formula is met, the mud can form a mud film; if the formula is not met, the mud cannot form a mud film.

3. The method for evaluating and optimizing the quality of slurry support in slurry shield tunneling according to claim 1, characterized in that, In step 3), the formula for calculating the porosity of sandy soil strata is as follows: In the formula, Indicates the porosity of sandy soil layers; This indicates the initial porosity of the sandy soil layer before mud infiltration begins; This represents the stagnation rate of bentonite particles within a micro-element, that is, the volume of bentonite particles stagnating in a unit volume of mud.

4. The method for evaluating and optimizing the quality of slurry support in slurry shield tunneling according to claim 3, characterized in that, In step 3), the formula for calculating the permeability of sandy soil strata is as follows: In the formula, Indicates the permeability coefficient of sandy soil layers; This represents the permeability coefficient of sandy soil to water. and These represent the dynamic viscosity coefficients of water and mud, respectively. The formula for calculating mud permeability is as follows: In the formula, This represents the stagnation gradient of the mud (kPa / m); This represents the density of water inside a porous medium element; Represents gravitational acceleration; Indicates the mud penetration distance; Represents the pore water pressure within a porous media micro-element; It is the macroscopic permeation rate of the mud suspension inside the porous medium micro-element; The formula for calculating volume fraction is as follows: In the formula, This indicates the volume fraction of liquid in the mud suspension inside a porous media micro-element. λ represents the filtration coefficient of the porous media permeation zone; Indicates mud infiltration time; The formula for calculating the stagnation rate of mud particles is as follows: In the formula, This indicates the retention rate of mud particles, which is the volume of bentonite particles that remain in a unit volume of mud. The formula for calculating pore water pressure in sandy soil strata is as follows: In the formula, C represents the water storage coefficient of porous media. w =1-C s .

5. The method for evaluating and optimizing the quality of slurry support for slurry shield tunneling as described in claim 1, characterized in that, The mud parameters include: mud gradation, mud yield strength, mud particle density, mud slurry mass concentration, and mud viscosity; the formation parameters include: sandy soil porosity, formation permeability coefficient, formation filtration coefficient, and formation water storage coefficient; the mud mechanical parameters include: viscosity, consistency, and concentration.

6. The method for evaluating and optimizing the quality of slurry support for slurry shield tunneling as described in claim 1, characterized in that, The boundary conditions to be set include: grouting pressure, infiltration time, and initial volume fraction of the mud.

7. The method for evaluating and optimizing the quality of slurry support in slurry shield tunneling according to claim 1, characterized in that, The additives include: CMC, PA, PAC or PHPA.

8. The method for evaluating and optimizing the quality of slurry support in slurry shield tunneling according to claim 1, characterized in that, The results of the iterative calculations include: mud penetration distance, pore water pressure in sandy soil layers, mud penetration velocity, porosity of sandy soil layers, permeability coefficient of sandy soil layers, volume fraction of mud particles, and stagnation rate of mud particles; the evaluation results of good mud support quality include: the law of change of mud penetration distance over time; the law of change of pore water pressure, mud penetration velocity, porosity, permeability coefficient, volume fraction of mud particles, and stagnation rate of mud particles over time and penetration distance in sandy soil layers.

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