A method for preventing blockage of a long-distance hard rock shield construction mud circulating system pipeline

Abstract

The application provides a long-distance hard rock shield construction mud circulating system pipeline anti-blocking method, which is suitable for the field of slurry shield construction. The application comprises the following steps: establishing a characteristic particle size relationship formula, selecting a blocking risk model, pouring a joint construction section, dynamically monitoring and adjusting, and recording and feeding back, establishing a mathematical model capable of reflecting the relationship between the indirect tensile strength of rocks, the cutter head rotating speed, the total thrust of the cutter head and the characteristic particle size of rock debris, collecting key parameters in the shield machine operation process in real time, combining the physical properties of the on-site rocks, dynamically adjusting the flow rate of the mud, and ensuring that the flow rate of the mud is always maintained in an optimal state capable of effectively carrying the rock debris and preventing pipeline blocking. The method not only improves the adaptability and flexibility of the mud circulating system, but also significantly reduces the shutdown risk caused by pipeline blocking, and has important significance for improving the efficiency and safety of long-distance hard rock tunnel construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of slurry shield construction, and particularly relates to a method for preventing blockage of a slurry circulation system pipeline in long-distance hard rock shield construction. BACKGROUND

[0002] In the process of slurry shield construction, the slurry circulation system is mainly responsible for transporting the rock debris cut by the shield machine from the working face to the ground treatment station, and transporting the treated slurry back to the shield machine for recycling. For the blockage problem of the slurry circulation system pipeline, the conventional method is to calculate a certain value as the minimum value of the slurry input flow rate in advance through various critical deposition flow rate calculation models. In long-distance hard rock conditions, the critical deposition flow rate calculated by the Fei Xiangjun model considering the influence of solid particles and pipe 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 different rock characteristics. In high-strength hard rock areas, low speed and high torque are used for slow advancement, and the rock debris size generated at this time is relatively large. In lower strength hard rock areas, high speed and low torque are used for rapid advancement to speed up construction efficiency, and the rock debris size generated at this time is relatively small. When the cutter head thrust is not enough, the thrust is also adjusted to increase the cutter cutting force.

[0003] These adjustments directly make it difficult for the traditional critical deposition flow rate calculated based on fixed conditions to effectively respond to complex working condition changes, which can easily cause blockage of the slurry circulation system pipeline. SUMMARY

[0004] The purpose of the present application is to solve the problem of blockage of the slurry circulation system pipeline when the traditional critical deposition flow rate calculation method cannot respond to changes in the cutter head speed, torque and thrust working conditions in the process of long-distance hard rock cement shield construction. A method for preventing blockage of the slurry circulation system pipeline in long-distance hard rock shield construction is proposed, which can be widely applied in the field of slurry shield construction.

[0005] To achieve the above purpose, the present application provides the following technical scheme:

[0006] S101, a characteristic particle size relationship is established;

[0007] The establishment of the characteristic particle size relationship includes obtaining the crushed rock debris grading data through sieve analysis test according to the crushed rock debris of the existing hard rock slurry shield construction project, and the characteristic particle size corresponding to 90% of the cumulative mass of the undersize is denoted as d 90 Then, a relationship is established according to the value of the characteristic particle size d 90

[0008]

[0009] ​

[0010] wherein k, n are empirical coefficients; σ t - indirect tensile strength, Pa; p - depth of cut, m; v - tool advance speed, m / s; N - cutterhead rotation speed, rps; F c - cutting force of a single tool, N, estimated from the total thrust of the cutterhead F divided by the number of tools m;

[0011] S102, selecting a plugging risk model;

[0012] The selecting a plugging risk model comprises obtaining the indirect tensile strength of the rock of the current project through a splitting test, selecting a plugging risk model of the mud circulation system pipeline, and calculating a critical deposition flow rate,

[0013]

[0014] wherein v L - critical deposition flow rate, m / s; f - resistance coefficient; g - gravitational acceleration, taken as 9.8 m / s 2 ; D - pipeline diameter, m; p s - formation solid density, t / m 3 ; p - mud density of the discharge pipeline; S v - volume fraction of solid particles of the mud;

[0015] S103, dynamically monitoring and adjusting;

[0016] The dynamically monitoring and adjusting comprises obtaining a real-time cutterhead rotation speed N through a rotation speed sensor of a main drive system of the slurry balance shield machine, obtaining a real-time total thrust of the cutterhead through a pressure sensor of a hydraulic system, and obtaining a displacement AS in each time T through a displacement sensor of a propulsion system, so as to indirectly obtain a real-time tool advance speed v,

[0017]

[0018] The real-time cutterhead rotation speed, the real-time total thrust of the cutterhead, and the real-time tool advance speed are substituted into formulas (1), (2), and (3) to obtain a current critical deposition flow rate v L The discharge amount AV of the mud circulation system discharge pipeline in each time T is obtained to obtain a real-time discharge flow rate v t ,

[0019]

[0020] wherein A - cross-sectional area of the discharge pipeline; if the real-time discharge flow rate v t is less than the current critical deposition flow rate v L , the mud input flow rate of the inlet pipeline is increased, and the increment value of the mud input flow rate is AV,

[0021] Δv=η(v L -v t (6)

[0022] In the formula, η is the velocity compensation coefficient; if the mud input velocity increases by Δv and exceeds the maximum design velocity, then the mud input flow rate is limited to the maximum design velocity.

[0023] S104. Recording and Feedback;

[0024] The recording and feedback includes recording the data of crushed rock slag gradation, real-time cutterhead rotation speed, real-time cutterhead total thrust, real-time cutter advance speed, critical sedimentation velocity and incremental value of mud input velocity during the current project construction process. Based on the actual blockage situation of the current project, the empirical coefficient in the characteristic particle size relationship formula (1) is further adjusted.

[0025] Furthermore, in step S102 above, the drag 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 the slurry on turbulence suppression, which is taken as 1.0; δ is the pipe wall roughness, which is taken according to the wear degree of the pipe wall, and is taken in the range of 0.05 to 0.5 mm; Re is the Reynolds number of the mud fluid;

[0028] Furthermore, in step S102 above, the volume fraction S of the slurry solid particles is... v The following formula must be satisfied:

[0029]

[0030] In the formula, ρ l - Prepare the liquid density of the mud, t / m³ 3 .

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

[0032]

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

[0034] The beneficial effects of the present application are: a mathematical model capable of reflecting the relationship between the indirect tensile strength between rocks, the cutter head rotating speed and the total thrust of the cutter head and the characteristic particle size of the rock debris is established, the key parameters in the operation process of the shield machine are collected in real time, and the flow rate of the mud is dynamically adjusted in combination with the physical properties of the rock on site, so that the mud can always maintain an optimal state which can effectively carry the rock debris and prevent pipeline blockage. This method not only improves the adaptability and flexibility of the mud circulating system, but also significantly reduces the shutdown risk caused by pipeline blockage, which is of great significance to improve the efficiency and safety of long-distance hard rock tunnel construction. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 is a flow chart of the long-distance hard rock shield construction mud circulating system pipeline anti-blocking method of the present application. DETAILED DESCRIPTION

[0036] The specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments given here are only for illustration and explanation of the present application and cannot be used to limit the present application. It should be noted that in the following description, many specific details are set forth in order to provide a thorough understanding of the present application, however, the present application can also have other embodiments and variations, therefore, the protection scope of the present application is not limited by the specific embodiments disclosed below.

[0037] Example one relies on a nuclear power drainage tunnel shield construction project, the total length of the tunnel is 5200.2m, the shield tunnel length is 5002.296m respectively, the overburden thickness is 9.07m-22.4m, and a slurry balance shield machine with an excavation diameter of 7620mm is used for construction. The cutter head opening rate is 30%, the maximum stone particle size entering the cutting cabin is not greater than 0.2m, and the rock blocks with a particle size greater than 0.2m are left in front of the cutter head and crushed by the cutter or the cutter head and then enter the mud cabin. The inner diameters of the slurry inlet and outlet pipelines are both 387mm, the liquid density of the mud is 1.0t / m 3 , the slurry density of the slurry inlet pipeline is 1.1t / m 3 , and the slurry density of the slurry outlet pipeline is 1.3t / m 3 . The long-distance hard rock shield construction mud circulating system pipeline anti-blocking method is as follows:

[0038] S101, a characteristic particle size relationship is established;

[0039] According to the broken rock debris of the existing hard rock slurry shield construction project, the broken rock debris grading data is obtained after sieve analysis test, the characteristic particle size corresponding to the cumulative mass of 90% of the sieve under is recorded as d 90 , and then a relationship is established according to the value of the characteristic particle size d 90 under different construction conditions,

[0040]

[0041] wherein k, n-empirical coefficients; σ t -Indirect tensile strength, Pa; p-depth of cut, m; v-advance speed of the tool, m / s; N-rotational speed of the tool holder, rps; F c -Cutting force of a single tool, N, estimated according to the total thrust force of the tool holder F divided by the number of tools m;

[0042] S102, selecting a plugging risk model;

[0043] The existing data show that the most suitable calculation model for the current field test is the Fe Xiangjun model, which fully considers the influence of solid particles and pipeline resistance; the indirect tensile strength of the rock is obtained through a splitting test, a mud circulating system pipeline plugging risk model is selected, and the critical deposition flow rate is calculated according to the following formula,

[0044]

[0045] wherein v L -Critical deposition flow rate, m / s; f-resistance coefficient; g-gravitational acceleration, taken as 9.8 m / s 2 ; D-pipeline diameter, m; p s -Formation solid density, 2.7 t / m in the embodiment; 3 ; p-discharge pipeline mud density; S v -Mud solid particle volume fraction; wherein the resistance coefficient is obtained according to the following formula,

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

[0047] wherein a-impact coefficient of the slurry on turbulence suppression, taken as 1.0; δ-pipe wall roughness, taken in the range of 0.05-0.5 mm according to the degree of pipe wall wear, 0.1 mm in the embodiment; Re-mud fluid Reynolds number, 3420 in the embodiment; the mud solid particle volume fraction S v is obtained according to the following formula,

[0048]

[0049] wherein p l -Density of the liquid of the configured mud, t / m 3 ;

[0050] S103, dynamically monitoring and adjusting;

[0051] The real-time cutterhead rotating speed N is obtained through the rotating speed sensor of the main driving system of the slurry balance shield machine, the real-time cutterhead total thrust is obtained through the pressure sensor of the hydraulic system, and the displacement AS in each time T is obtained through the displacement sensor of the propulsion system, so that the real-time cutter advancing speed v is indirectly obtained,

[0052]

[0053] The real-time cutterhead rotating speed, the real-time cutterhead total thrust, and the real-time cutter advancing speed are substituted into formulas (1), (2), and (3) to obtain the current critical sedimentation flow rate v L The real-time discharge flow rate v is obtained through the discharge amount AV of the slurry discharge pipeline of the slurry circulation system in each time T, t ,

[0054]

[0055] In the formula, A is the cross-sectional area of the discharge pipeline; if the real-time discharge flow rate v t is less than the current critical sedimentation flow rate v L , the slurry input flow rate is increased, and the increment value of the slurry input flow rate is Δv,

[0056] Δv = η (v L -v t ) (8)

[0057] In the formula, η is a flow rate compensation coefficient; in order to ensure that there is enough slurry support in front of the shield machine, the slurry input flow rate is usually slightly higher than the slurry output flow rate, when the slurry input flow Q in and the slurry discharge flow Q out are stable, they are equal, the inner diameter of the slurry discharge pipeline is slightly larger than the inner diameter of the slurry input pipeline, so that the slurry input flow rate is greater than the slurry output flow rate, that is, the slurry input flow rate is reduced when it is transmitted to the slurry discharge pipeline due to the change in the inner diameter of the pipeline, therefore, when the slurry output flow rate is increased by Δv, the slurry input flow rate needs to be increased by ηΔv.

[0058]

[0059] In the formula, r out is the inner diameter of the slurry discharge pipeline, m; r in is the inner diameter of the slurry input pipeline, m; in this embodiment, the inner diameter of the slurry discharge pipeline is the same as the inner diameter of the slurry input pipeline, that is, the flow rate compensation coefficient is 1; at the same time, it needs to be considered that too large flow rate will accelerate the wear of the pipeline, therefore, the maximum design flow rate is regulated in the slurry shield construction, if the slurry input flow rate is increased 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 record and feedback include recording the broken rock slag grading data in the current project construction process, the real-time cutter disc rotating speed, the real-time cutter disc total thrust, the real-time cutter advancing speed, the critical sedimentation flow rate and the increment value of the mud input flow rate, according to the actual plugging condition of the current project, further adjusting the empirical coefficient in the characteristic particle size relationship formula (1), increasing the value of the characteristic particle size d 90 , further increasing the critical sedimentation flow rate, avoiding the deposition of rock slag in the pipeline and causing the pipeline to be blocked.

[0062] In summary, the anti-blocking method of the long-distance hard rock shield construction mud circulating system pipeline of the application improves the adaptability and flexibility of the mud circulating 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 embodiments are one or more embodiments of the application, and there are many other embodiments and variations based on the application; the deformation and modification of the application by ordinary skilled persons in the industry without making pioneering innovation all belong to the protection scope of the application.

Claims

1. A method for preventing clogging of the slurry circulation system pipeline in long-distance hard rock shield tunneling, characterized in that... Specifically, the following steps are included: S101. Establish the characteristic particle size relationship formula; The establishment of the characteristic particle size relationship includes obtaining the gradation data of crushed rock debris from existing hard rock slurry shield tunneling projects through sieve analysis tests. The characteristic particle size corresponding to 90% of the cumulative mass under sieve is denoted as d. 90 Then, based on the characteristic particle size d under different construction conditions 90 Establish a relational expression based on the values. In the formula, k and n are empirical coefficients; σ t - Indirect tensile strength, Pa; p - Depth of cut, m; v - Tool feed rate, m / s; N - Tool head speed, rps; F c - The cutting force of a single tool, N, is estimated by dividing the total thrust of the cutter head F by the number of tools m; S102. Select a congestion risk model; The selection of the clogging risk model includes obtaining the indirect tensile strength of the rock in the current project through a splitting test, selecting a clogging risk model for the mud circulation system pipeline, and calculating the critical sedimentation velocity. In the formula: v L - Critical settling velocity, m / s; f - Drag coefficient; g - Gravitational acceleration, taken as 9.8 m / s² 2 D - Pipe diameter, m; ρ s -Solid density of the formation, t / m³ 3 ρ - Slurry density in the slurry discharge pipeline; S v - Volume fraction of solid particles in mud; S103. Dynamic monitoring and adjustment; The dynamic monitoring and adjustment include obtaining the real-time cutterhead rotation speed N through the rotation speed sensor of the slurry balance shield machine's main drive system, obtaining the real-time total thrust of the cutterhead 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, thus indirectly obtaining the real-time cutterhead propulsion speed v. Substituting the real-time cutter head rotation speed, real-time cutter head total thrust, and real-time cutter feed speed into equations (1), (2), and (3) yields the current critical sedimentation velocity v. L The real-time slurry discharge velocity v is obtained by measuring the slurry discharge volume ΔV within each time period T in the slurry circulation system's slurry discharge pipeline. t , In the formula, A represents the cross-sectional area of ​​the slurry discharge pipe; if the real-time slurry discharge velocity v t Less than the current critical precipitation flow rate v L If the mud input velocity in the slurry inlet pipe is increased, the increment value of the mud input velocity is Δv. Δv=η(v L -v t ) (6) In the formula, η is the velocity compensation coefficient; if the mud input velocity increases by Δv and exceeds the maximum design velocity, then the mud input flow rate is limited to the maximum design velocity. S104. Recording and Feedback; The recording and feedback includes recording the data of crushed rock slag gradation, real-time cutterhead rotation speed, real-time cutterhead total thrust, real-time cutter advance speed, critical sedimentation velocity and incremental value of mud input velocity during the current project construction process. Based on the actual blockage situation of the current project, the empirical coefficient in the characteristic particle size relationship formula (1) is further adjusted.

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

3. The method for preventing blockage of the slurry circulation system pipeline in long-distance hard rock shield tunneling as described in claim 1, characterized in that: In step S102, the volume fraction S of the slurry solid particles is... v The following formula must be satisfied: In the formula, ρ l - Prepare the liquid density of the mud, t / m³ 3 .

4. The method for preventing blockage of the slurry circulation system pipeline in long-distance hard rock shield tunneling as described in claim 1, characterized in that: In step S103, the velocity loss compensation coefficient η satisfies the following formula: In the formula, r out -Inner diameter of slurry discharge pipe, m; r in -Inner diameter of the slurry inlet pipe, in meters.

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