Anti-blocking method for long-distance hard rock shield construction slurry circulation system pipeline

Abstract

The invention provides an anti-blocking method for a long-distance hard rock shield construction slurry circulation system pipeline, and is suitable for the field of slurry shield construction. The method comprises the steps of establishing a characteristic particle size relational expression, selecting a blockage risk model, pouring a connecting seam construction section, dynamically monitoring and adjusting, recording and feeding back, and establishing a mathematical model capable of reflecting the relationship among the indirect tensile strength of rock, the rotating speed of a cutter head, the total thrust of the cutter head and the characteristic particle size of rock slag. Key parameters in the operation process of the shield tunneling machine are collected in real time, the physical characteristics of on-site rocks are combined, the flow speed of slurry is dynamically adjusted, it is ensured that the slurry is always kept in the optimal state capable of effectively carrying rock residues and preventing pipelines from being blocked, and by means of the method, the adaptability and flexibility of a slurry circulation system are improved; and the shutdown risk caused by pipeline blockage is remarkably reduced, and the method has important significance for improving the efficiency and safety of long-distance hard rock tunnel construction.

Description

Technical Field

[0001] The invention relates to the field of slurry shield construction, and in particular to an anti-blocking method for a pipeline of a slurry circulation system in long-distance hard rock shield construction. Background Art

[0002] During the construction of slurry shield, the mud circulation system is mainly responsible for transporting the rock slag cut by the shield machine from the face to the ground processing station, and then transporting the treated mud back to the shield machine for recycling. For the blockage problem of the mud circulation system pipeline, the current conventional method is to pre-calculate a certain value as the minimum value of the mud input flow rate through various critical sedimentation velocity calculation models. Under long-distance hard rock conditions, the critical sedimentation velocity calculated by Fei Xiangjun's model, which takes into account the influence of solid particles and pipeline resistance, is more accurate. However, the assumed construction conditions are relatively constant, and the cutter head speed and torque need to be adjusted according to the different characteristics of the rock. In the high-strength hard rock area, low speed and high torque are used for slow advancement, and the rock slag particle size generated at this time is relatively large, while in the low-strength hard rock area, high speed and low torque are used for rapid advancement to speed up the construction efficiency, and the rock slag particle size generated at this time is relatively small. When the thrust of the cutter head is insufficient, the thrust will also be adjusted to increase the cutting force of the tool.

[0003] These adjustments directly make it difficult for the traditional critical sedimentation velocity calculated based on fixed working conditions to effectively cope with complex changes in working conditions, which can easily cause blockage of the mud circulation system pipeline. Summary of the invention

[0004] The purpose of the present invention is to solve the problem that the traditional critical sedimentation velocity calculation method cannot cope with the blockage of the mud circulation system pipeline when the cutter head speed, torque and thrust conditions change during the construction of long-distance hard rock cement shield. A method for preventing the blockage of the mud circulation system pipeline in long-distance hard rock shield construction is proposed, which can be widely used in the field of slurry shield construction.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] S101, establishing a characteristic particle size relationship;

[0007] The characteristic particle size relationship is established by obtaining the crushed rock slag gradation data after sieving test based on the crushed rock slag of the existing hard rock slurry shield construction project, and the characteristic particle size corresponding to 90% of the cumulative mass under the sieve is recorded as d 90 , and then according to the characteristic particle size d under different construction conditions 90 The value of establishes the relationship,

[0008]

[0009]

[0010] Where, k, n-empirical coefficients; σ t - indirect tensile strength, Pa; p- cutting depth, m; v- tool advance speed, m / s; N- cutter head speed, rps; F c - The cutting force of a single tool, N, is estimated by dividing the total thrust force F of the cutter head by the number of tools m;

[0011] S102, selecting a congestion risk model;

[0012] The selection of the blockage risk model includes obtaining the indirect tensile strength of the rock of the current project through a splitting test, selecting a blockage risk model for the mud circulation system pipeline, and calculating the critical sedimentation velocity.

[0013]

[0014] Where: v L - critical sedimentation velocity, m / s; f- resistance coefficient; g- acceleration due to gravity, taken as 9.8 m / s 2 ; D-pipeline diameter, m; ρ s - Density of formation solids, t / m 3 ; ρ-slurry density in the slurry discharge pipeline; S v - Mud solid particle volume fraction;

[0015] S103, dynamic monitoring and adjustment;

[0016] The dynamic monitoring and adjustment includes obtaining the real-time cutter head speed N through the speed sensor of the main drive system of the slurry balance shield machine, obtaining the real-time cutter head total thrust through the pressure sensor of the hydraulic system, and obtaining the displacement ΔS within each time period T through the displacement sensor of the propulsion system, thereby indirectly obtaining the real-time tool propulsion speed v.

[0017]

[0018] Substitute the real-time cutter head speed, real-time cutter head total thrust, and real-time tool advancement speed into equations (1), (2), and (3) to obtain the current critical sedimentation velocity v L , the real-time discharge velocity v is obtained by the discharge volume ΔV of the mud circulation system discharge pipeline in each period T t ,

[0019]

[0020] Where A is the cross-sectional area of ​​the slurry discharge pipe; if the real-time slurry discharge velocity v t Less than the current critical sedimentation velocity v L , then the mud input flow rate of the slurry inlet pipeline is increased, and the incremental value of the mud input flow rate is Δv,

[0021] Δv=η(v L -v t ) (6)

[0022] Where η is the velocity compensation coefficient. If the mud input velocity increases by Δv and is greater than the maximum design velocity, the mud input flow rate is limited to the maximum design velocity.

[0023] S104, record and feedback;

[0024] The recording and feedback include recording the crushed rock slag grading data, real-time cutter head rotation speed, real-time cutter head total thrust, real-time tool advancement speed, critical sedimentation flow rate and the incremental value of the mud input flow rate during the construction process of the current project, and further adjusting the empirical coefficient in the characteristic particle size relationship (1) according to the actual blockage situation of the current project.

[0025] Furthermore, in the above step S102, the resistance coefficient f satisfies the following formula:

[0026] f=α×0.11(δ / D+68 / Re) 0.25 (7)

[0027] In the formula, α is the influence coefficient of slurry on turbulence suppression, which is 1.0; δ is the roughness of the pipe wall, which is determined according to the degree of wear of the pipe wall and is in the range of 0.05 to 0.5 mm; Re is the Reynolds number of the mud fluid;

[0028] Furthermore, in the above step S102, the slurry solid particle volume fraction S v Satisfies the following formula,

[0029]

[0030] In the formula, ρ l -Liquid density of the mud, t / m 3 .

[0031] Furthermore, in the above step S103, the velocity loss compensation coefficient η satisfies the following formula:

[0032]

[0033] In the formula, r out -Inner diameter of the slurry discharge pipe, m; r in -Inner diameter of slurry inlet pipe, m.

[0034] The beneficial effects of the present invention are: establishing a mathematical model that can reflect the relationship between the indirect tensile strength of rock, the rotation speed of the cutter disc, the total thrust of the cutter disc and the characteristic particle size of the rock slag, and dynamically adjusting the flow rate of the mud by real-time acquisition of key parameters during the operation of the shield machine and combining the physical properties of the on-site rock to ensure that it always maintains an optimal state that can effectively carry the rock slag and prevent pipeline blockage. This method not only improves the adaptability and flexibility of the mud circulation system, but also significantly reduces the risk of shutdown caused by pipeline blockage, which is of great significance for improving the efficiency and safety of long-distance hard rock tunnel construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 The present invention is a flow chart of a method for preventing clogging of a pipeline of a mud circulation system in long-distance hard rock shield construction. DETAILED DESCRIPTION

[0036] The specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments given here are only used to illustrate and explain the present invention and cannot be used to limit the present invention. It should be noted that many specific details are set forth in the following description to facilitate a full understanding of the present invention, but the present invention may also have other embodiments and variations thereof, and therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0037] Example 1 is based on a nuclear power drainage tunnel shield construction project. The total length of the tunnel is 5200.2m, the length of the shield tunnel is 5002.296m, the cover thickness is 9.07m~22.4m, and the slurry shield machine with an excavation diameter of 7620mm is used for construction. The cutterhead opening rate is 30%, and the cutterhead opening limits the maximum stone particle size entering the cutting chamber to no more than 0.2m. Rocks with a particle size greater than 0.2m are left in front of the cutterhead and are cut by the tool or crushed by the cutterhead before entering the mud water tank. The inner diameters of the slurry inlet and outlet pipelines are both 387mm, and the liquid density of the configured mud is 1.0t / m 3 The mud density of the slurry inlet pipeline is 1.1t / m 3 The mud density of the slurry discharge pipeline is 1.3t / m 3 The anti-blocking method of the mud circulation system pipeline in long-distance hard rock shield construction is as follows:

[0038] S101, establishing a characteristic particle size relationship;

[0039] According to the crushed rock slag of the existing hard rock slurry shield construction project, the crushed rock slag gradation data was obtained after the screening test, and the characteristic particle size corresponding to 90% of the cumulative mass under the sieve was recorded as d 90 , and then according to the characteristic particle size d under different construction conditions 90 The value of establishes the relationship,

[0040]

[0041] Where, k, n-empirical coefficients; σ t - indirect tensile strength, Pa; p- cutting depth, m; v- tool advance speed, m / s; N- cutter head speed, rps; F c - The cutting force of a single tool, N, is estimated by dividing the total thrust force F of the cutter head by the number of tools m;

[0042] S102, selecting a congestion risk model;

[0043] Existing data show that the most consistent calculation model with the field test is the Fei Xiangjun model, which fully considers the influence of solid particles and pipeline resistance; the indirect tensile strength of the rock of the current project is obtained through splitting test, and the pipeline blockage risk model of the mud circulation system is selected. The critical sedimentation velocity is calculated according to the following formula:

[0044]

[0045] Where: v L - critical sedimentation velocity, m / s; f- resistance coefficient; g- acceleration due to gravity, taken as 9.8 m / s 2 ; D-pipeline diameter, m; ρ s - Formation solid density, in this example it is 2.7t / m 3 ; ρ-slurry density in the slurry discharge pipeline; S v - Mud solid particle volume fraction; the resistance coefficient is calculated according to the following formula:

[0046] f=α×0.11(δ / D+68 / Re) 0.25 =0.041 (4)

[0047] Wherein, α-the influence coefficient of slurry on turbulence suppression is 1.0; δ-the roughness of the pipe wall is taken according to the degree of wear of the pipe wall, and is in the range of 0.05-0.5 mm, and is 0.1 mm in this embodiment; Re-the Reynolds number of the mud fluid, which is 3420 in this embodiment; the volume fraction of the mud solid particles S v According to the following formula,

[0048]

[0049] In the formula, ρ l -Liquid density of the mud, t / m 3 ;

[0050] S103, dynamic monitoring and adjustment;

[0051] The real-time cutter head speed N is obtained through the speed sensor of the main drive system of the slurry balance shield machine, the real-time cutter head total thrust is obtained through the pressure sensor of the hydraulic system, and the displacement ΔS within each time period T is obtained through the displacement sensor of the propulsion system, thus indirectly obtaining the real-time tool propulsion speed v.

[0052]

[0053] Substitute the real-time cutter head speed, real-time cutter head total thrust, and real-time tool advancement speed into equations (1), (2), and (3) to obtain the current critical sedimentation velocity v L , the real-time discharge velocity v is obtained by the discharge volume ΔV of the mud circulation system discharge pipeline in each period T t ,

[0054]

[0055] Where A is the cross-sectional area of ​​the slurry discharge pipe; if the real-time slurry discharge velocity v t Less than the current critical sedimentation velocity v L , then the mud input flow rate of the slurry inlet pipeline is increased, and the incremental value of the mud input flow rate is Δv,

[0056] Δv=η(v L -v t ) (8)

[0057] In the formula, η is the velocity compensation coefficient. In order to ensure sufficient slurry support in front of the shield machine, the slurry input velocity is usually slightly higher than the slurry output velocity. in and discharge flow Q out When stable, the two are equal, and the inner diameter of the slurry discharge pipeline will be slightly larger than the inner diameter of the slurry inlet pipeline, so that the mud input flow rate is greater than the mud output flow rate. That is, when the mud input flow rate is transmitted to the slurry discharge pipeline, it will be reduced due to the change in the inner diameter of the pipeline. Therefore, when the mud output flow rate increases by Δv, the mud input flow rate needs to increase by ηΔv;

[0058]

[0059] In the formula, r out -Inner diameter of the slurry discharge pipe, m; r in -Inner diameter of the slurry inlet pipeline, m; in this embodiment, the inner diameter of the slurry discharge pipeline is the same as the inner diameter of the slurry inlet pipeline, that is, the flow rate compensation coefficient is 1; at the same time, it should be considered that excessive flow rate will accelerate the wear of the pipeline, so the slurry shield construction stipulates a maximum design flow rate. If the slurry input flow rate increases by Δv and is greater than the maximum design flow rate, the slurry input flow rate is limited to the maximum design flow rate;

[0060] S104, record and feedback;

[0061] The recording and feedback include recording the crushed rock slag grading data, real-time cutter head speed, real-time cutter head total thrust, real-time tool advancement speed, critical sedimentation flow rate and the incremental value of mud input flow rate during the construction process of the current project. According to the actual blockage situation of the current project, the empirical coefficient in the characteristic particle size relationship (1) is further adjusted to increase the characteristic particle size d 90 value, further increasing the critical sedimentation velocity and preventing rock slag from settling in the pipeline and causing pipeline blockage.

[0062] In summary, the anti-blocking method of the mud circulation system pipeline of the long-distance hard rock shield construction of the present invention improves the adaptability and flexibility of the mud circulation system in the field of slurry shield construction, and significantly reduces the risk of shutdown caused by pipeline blockage.

[0063] It should be understood that the above-mentioned embodiments are one or more embodiments of the present invention, and there are many other embodiments and variations thereof based on the present invention; the variations and modifications made by ordinary technicians in this industry through the present invention without making pioneering innovations all fall within the scope of protection of the present invention.

Claims

1. A method for preventing clogging of the pipeline of the mud circulation system in long-distance hard rock shield construction, characterized in that The specific steps include: S101, establishing a characteristic particle size relationship; The characteristic particle size relationship is established by obtaining the crushed rock slag gradation data after sieving test based on the crushed rock slag of the existing hard rock slurry shield construction project, and the characteristic particle size corresponding to 90% of the cumulative mass under the sieve is recorded as d 90 , and then according to the characteristic particle size d under different construction conditions 90 The value of establishes the relationship, Where, k, n-empirical coefficients; σ t - indirect tensile strength, Pa; p- cutting depth, m; v- tool advance speed, m / s; N- cutter head speed, rps; F c - The cutting force of a single tool, N, is estimated by dividing the total thrust force F of the cutter head by the number of tools m; S102, selecting a congestion risk model; The selection of the blockage risk model includes obtaining the indirect tensile strength of the rock of the current project through a splitting test, selecting a blockage risk model for the mud circulation system pipeline, and calculating the critical sedimentation velocity. Where: v L - critical sedimentation velocity, m / s; f- resistance coefficient; g- acceleration due to gravity, taken as 9.8 m / s 2 ; D-pipeline diameter, m; ρ s - Density of formation solids, t / m 3 ; ρ-slurry density in the slurry discharge pipeline; S v - Mud solid particle volume fraction; S103, dynamic monitoring and adjustment; The dynamic monitoring and adjustment includes obtaining the real-time cutter head speed N through the speed sensor of the main drive system of the slurry balance shield machine, obtaining the real-time cutter head total thrust through the pressure sensor of the hydraulic system, and obtaining the displacement ΔS within each time period T through the displacement sensor of the propulsion system, thereby indirectly obtaining the real-time tool propulsion speed v. Substitute the real-time cutter head speed, real-time cutter head total thrust, and real-time tool advancement speed into equations (1), (2), and (3) to obtain the current critical sedimentation velocity v L , the real-time discharge velocity v is obtained by the discharge volume ΔV of the mud circulation system discharge pipeline in each period T t , Where A is the cross-sectional area of ​​the slurry discharge pipe; if the real-time slurry discharge velocity v t Less than the current critical sedimentation velocity v L , then the mud input flow rate of the slurry inlet pipeline is increased, and the incremental value of the mud input flow rate is Δv, Δv=η(v L -v t ) (6) Where η is the velocity compensation coefficient. If the mud input velocity increases by Δv and is greater than the maximum design velocity, the mud input flow rate is limited to the maximum design velocity. S104, record and feedback; The recording and feedback include recording the crushed rock slag grading data, real-time cutter head rotation speed, real-time cutter head total thrust, real-time tool advancement speed, critical sedimentation flow rate and the incremental value of the mud input flow rate during the construction process of the current project, and further adjusting the empirical coefficient in the characteristic particle size relationship (1) according to the actual blockage situation of the current project.

2. The anti-blocking method for the pipeline of the mud circulation system in the long-distance hard rock shield construction according to claim 1 is characterized by: In step S102, the drag coefficient f satisfies the following formula: f=α×0.11(δ / D+68 / Re) 0.25 (7) Wherein, α is the influence coefficient of slurry on turbulence suppression, which is taken as 1.0; δ is the roughness of the pipe wall, which is taken according to the degree of wear of the pipe wall and is in the range of 0.05 to 0.5 mm; Re is the Reynolds number of the mud fluid.

3. The anti-blocking method for the pipeline of the mud circulation system in the long-distance hard rock shield construction according to claim 1 is characterized by: In step S102, the slurry solid particle volume fraction S v Satisfies the following formula, In the formula, ρ l -Liquid density of the prepared mud, t / m 3 .

4. The anti-blocking method for the pipeline of the slurry circulation system in long-distance hard rock shield construction according to claim 1 is characterized by: In step S103, the velocity loss compensation coefficient η satisfies the following formula: In the formula, r out -Inner diameter of the slurry discharge pipe, m; r in -Inner diameter of slurry inlet pipe, m.

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