Shield tail sealing failure risk evaluation method based on numerical simulation

Abstract

The invention discloses a shield tail sealing failure risk evaluation method based on numerical simulation, which comprises the following steps: identifying failure influence factors including an external load resultant force influence factor and an internal pressure influence factor; obtaining to-be-evaluated external load resultant force and internal pressure of the shield tail sealing device; the external load resultant force to be evaluated and the internal pressure are input into a numerical simulation model, a numerical simulation result is output, and the numerical simulation model is composed of a shield tail brush and a sealing grease cavity; and analyzing the numerical simulation result in combination with the influence factors to obtain the risk level of the shield tail sealing device. According to the method, the influence factors of the external load resultant force of the shield tail sealing device and the internal pressure of the shield tail sealing system are determined, the shield tail sealing possibility judgment standard is determined based on the numerical simulation model, corresponding countermeasures are given, and monitoring and reasonable early warning of the shield tail sealing state are effectively guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of shield construction, and in particular relates to a shield tail seal failure risk assessment method based on numerical simulation. Background Art

[0002] With the vigorous development of urban rail transit networks, tunnel construction has entered a stage of rapid development, among which the shield method has been widely used due to its advantages of fast excavation speed and high construction efficiency. However, the geological conditions are complex, ranging from silty water-rich strata, water-rich fine sand strata to granular gravel strata.

[0003] When the shield is excavating, it is necessary to inject grease between the wire brushes at the tail of the shield, and use the extrusion force of the grease to fill the gaps inside the sealing wire brushes and between the wire brushes to enhance the sealing performance of the wire brushes, so that a solid sealing layer is formed at the tail of the shield to prevent the infiltration of mud, water, soil and sand. When encountering water-rich strata, the huge water and soil pressure can easily cause the shield tail seal to fail, causing water and soil to squeeze into the shield through the shield tail, endangering construction safety. Therefore, it is necessary to pay attention to the problem of shield tail seal failure during shield excavation.

[0004] The various means adopted in the existing technology mainly study the shield tail sealing grease and the shield tail sealing effect. There is less analysis on the failure process of the shield tail seal. There is no quantitative shield tail seal failure risk assessment yet. Therefore, a shield tail seal failure risk assessment method based on numerical simulation is urgently needed. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a shield tail seal failure risk assessment method based on numerical simulation, which can effectively ensure the monitoring and reasonable early warning of the shield tail seal status.

[0006] The present invention provides a shield tail seal failure risk assessment method based on numerical simulation, comprising:

[0007] Identify failure influencing factors, including external load combined force influencing factors and internal pressure influencing factors

[0008] Obtain the external load resultant force and internal pressure to be evaluated of the shield tail sealing device;

[0009] Input the external load resultant force and internal pressure to be evaluated into a numerical simulation model, and output a numerical simulation result, wherein the numerical simulation model is composed of a shield tail brush and a sealing grease cavity;

[0010] The numerical simulation results are analyzed in combination with the influencing factors to obtain the risk level of the shield tail sealing device.

[0011] Optionally, the external load resultant force includes: water and soil pressure resultant force and synchronous grouting pressure.

[0012] Optionally, the calculation method of the water-soil pressure is:

[0013] q w =γ·h0

[0014] h0=0.45×2 s-1 ·ω

[0015] ω=1+i(B+5)

[0016] Among them, q w is the resultant of water and soil pressure, γ is the bulk density of the surrounding rock, h0 is the average height of the construction collapse, S is the surrounding rock grade of the surrounding strata, ω is the width influence coefficient, B is the tunnel width, and i is the rate of increase or decrease of surrounding rock pressure when the tunnel width B increases or decreases by 1m.

[0017] Optionally, the influencing factors of the internal pressure include: linkage integrity of the shield tail sealing device and durability of the wire brush of the shield tail sealing device;

[0018] The linkage integrity of the shield tail sealing device is related to the grease pressure in the sealing grease cavity and the amount of sealing grease injected;

[0019] The durability of the wire brush of the shield tail sealing device is related to the assembly quality of the segments and the working posture quality of the shield machine.

[0020] Optionally, the method for obtaining the internal pressure is:

[0021] q2=μ·q d

[0022]

[0023] Where q2 is the internal pressure, μ is the attenuation coefficient, and q d is the grease pressure of the shield tail sealing device, a is the linkage integrity coefficient of the shield tail sealing device, and b is the durability coefficient of the shield tail sealing wire brush.

[0024] Optionally, the numerical simulation model is simulated using FLUENT.

[0025] Optionally, analyzing the numerical simulation results to obtain the risk level of the shield tail sealing device includes:

[0026] When the numerical simulation result shows that there is no leakage, it is determined to be a first-level risk;

[0027] When the numerical simulation result shows a small amount of slurry leakage, it is determined to be a secondary risk;

[0028] When the numerical simulation result shows that there is a certain amount of slurry leakage at the shield tail, it is determined to be a level 3 risk;

[0029] When the numerical simulation result shows that the leakage amount at the shield tail is large, but the leakage rate is slow, it is determined to be a level 4 risk;

[0030] When the numerical simulation result shows that there is a large amount of slurry leakage at the shield tail and the leakage speed is very fast, it is determined to be a level five risk.

[0031] Optionally, the method further includes: performing prevention and control according to the risk level.

[0032] Optionally, according to the risk level, prevention and control may include:

[0033] When the risk level is the first-level risk or the second-level risk, no prevention and control is required;

[0034] When the risk level is the third level risk, increase the high-quality sealing pressure and injection volume;

[0035] When the risk level is level 4 or level 5, the shield machine should stop excavating, increase the shield tail sealing force, and increase the shield tail sealing grease pumping speed.

[0036] Compared with the prior art, the present invention has the following advantages and technical effects:

[0037] The present invention analyzes various risk sources of shield tail seal failure. After studying the influencing mechanism of shield tail seal failure, the influencing factors of the combined force of external loads of the shield tail seal device and the internal pressure of the shield tail seal system are determined. Based on the numerical simulation model, the shield tail seal possibility evaluation standard is established, and corresponding countermeasures are given, which effectively ensures the monitoring and reasonable early warning of the shield tail seal status. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0039] Figure 1 It is a flow chart of a method for evaluating the risk of shield tail seal failure based on numerical simulation according to an embodiment of the present invention;

[0040] Figure 2 It is a numerical simulation model diagram of an embodiment of the present invention. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0042] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0043] The present invention proposes a method for evaluating the failure risk of shield tail seal based on numerical simulation. Figure 1 As shown, the specific steps include:

[0044] Identify failure influencing factors, including external load combined force influencing factors and internal pressure influencing factors;

[0045] Obtain the external load resultant force and internal pressure to be evaluated of the shield tail sealing device;

[0046] The resultant external load and internal pressure to be evaluated are input into the numerical simulation model, and the numerical simulation results are output. The numerical simulation model consists of a shield tail brush and a sealing grease cavity. The numerical model is simplified by simulating the actual shield tail sealing device using numerical software (fluent);

[0047] The numerical simulation results are analyzed in combination with the influencing factors to obtain the risk level of the shield tail sealing device.

[0048] Specifically, step S1: identifying the influencing factors of the external load resultant force q1 of the shield tail sealing device of the corresponding stratum of the shield tunneling.

[0049] Step S2: Identify factors affecting the internal pressure q2 of the shield tail sealing system;

[0050] Step S3: constructing a numerical simulation model according to the actual engineering of the shield tail sealing system;

[0051] Step S4: inputting the internal load q2 and the external load resultant force q1 into the numerical simulation model to reproduce the failure behavior of the shield tail seal;

[0052] Step S5: Analyze the numerical simulation results to evaluate the risk level of shield tail seal failure.

[0053] Furthermore, the resultant force of external loads includes: the resultant force of water and soil pressure and the synchronous grouting pressure.

[0054] Specifically, the synchronous grouting pressure is measured by on-site grouting pressure monitoring equipment.

[0055] Furthermore, the calculation method of the water-soil pressure is:

[0056] q w =γ·h0

[0057] h0=0.45×2 s-1 ·ω

[0058] ω=1+i(B+5)

[0059] Among them, q w is the resultant of water and soil pressure, γ is the bulk density of the surrounding rock, h0 is the average height of the construction collapse, S is the surrounding rock grade of the surrounding strata, ω is the width influence coefficient, B is the tunnel width, and i is the rate of increase or decrease of surrounding rock pressure when the tunnel width B increases or decreases by 1m.

[0060] Furthermore, the factors affecting the combined force of external loads include: geological environment, the geological environment in which the shield machine is located, and synchronous grouting pressure.

[0061] Furthermore, the factors affecting the internal pressure include: the linkage integrity of the shield tail seal device and the durability of the wire brush of the shield tail seal device;

[0062] The linkage integrity of the shield tail sealing device is related to the grease pressure in the sealing grease cavity and the amount of sealing grease injected. The greater the grease pressure and the amount of injection, the better the linkage integrity.

[0063] The durability of the wire brush of the shield tail sealing device is related to the assembly quality of the segments and the working posture quality of the shield machine. The worse the assembly quality of the segments and the working posture quality of the shield machine, the worse the durability of the wire brush.

[0064] Further, the method for obtaining the internal pressure is:

[0065] q2=μ·q d

[0066]

[0067] Where q2 is the internal pressure, μ is the attenuation coefficient, and q d is the grease pressure of the shield tail sealing device, a is the linkage integrity coefficient of the shield tail sealing device, and b is the durability coefficient of the shield tail sealing wire brush.

[0068] Specifically, the linkage integrity coefficient a of the shield tail sealing device is used to describe and evaluate the force transmission linkage and water-proof integrity of the shield tail sealing device, and is related to the grease pressure in the sealing grease cavity and the amount of sealing grease injected. The value is taken according to Table 1.

[0069] Table 1

[0070]

[0071] The quality grade of grease is determined by its water tightness, volatility, oil retention, consistency, and pumpability, as shown in Table 2 below:

[0072] Table 2

[0073]

[0074] The durability coefficient b of the shield tail sealing wire brush is mainly related to the assembly quality of the segment and the working posture quality of the shield machine. Among them, the assembly quality of the segment is related to factors such as the flatness of the outer arc surface of the segment, the ovality of the segment, and the deviation between the center of the segment and the center of the shield tail. The working posture quality level is related to the horizontal and vertical deviation of the shield tail, the elevation difference of the shield machine, and the minimum shield tail gap. The minimum shield tail gap is the difference between the inner diameter of the shield tail shell of the shield machine and the outer diameter of the segment, as shown in Table 3-5 below.

[0075] Table 3

[0076]

[0077]

[0078] Table 4

[0079]

[0080] Table 5

[0081] Shield tail seal wire brush durability grade Segment assembly quality level Shield machine working posture quality level Durability coefficient β value range I I I 0.8～1.0 II II II 0.6～0.8 III III III 0.4～0.6 IV IV IV 0.2～0.4 V V V 0～0.2

[0082] Furthermore, the numerical simulation model is simulated using FLUENT.

[0083] Specifically, the numerical simulation model is simulated using FLUENT. The model consists of three shield tail brushes and two sealing grease chambers. The right side of the model flow domain is the resultant force of the external load of the shield tail sealing device, which is set to size q1, and the size of the internal load of the model is set to q2.

[0084] Furthermore, the numerical simulation results are analyzed to obtain the risk level of the shield tail sealing device, including:

[0085] When the numerical simulation results show no leakage, it is judged as a level 1 risk;

[0086] When the numerical simulation result shows a small amount of slurry leakage, it is judged as a secondary risk;

[0087] When the numerical simulation results show that there is a certain amount of slurry leakage at the shield tail, it is judged as level 3 risk;

[0088] When the numerical simulation results show that the leakage amount at the shield tail is large, but the leakage rate is slow, it is judged as level 4 risk;

[0089] When the numerical simulation results show that there is a large amount of leakage at the shield tail and the leakage speed is very fast, it is judged as a level 5 risk.

[0090] Specifically, the risk of shield tail seal failure is determined based on the numerical simulation results, and the accident probability level is calculated. As shown in Table 6:

[0091] Table 6

[0092]

[0093] Furthermore, according to the risk level, prevention and control measures include:

[0094] When the risk level is level one or level two, no prevention and control is required;

[0095] When the risk level is level 3, increase the high-quality sealing pressure and injection volume;

[0096] When the risk level is level four or level five, the shield machine should stop excavating, increase the shield tail sealing strength, and increase the shield tail sealing grease pumping speed.

[0097] Specifically, when the accident probability level is R1 or R2, the possibility of shield tail failure is relatively low, and the shield can proceed normally without corrective measures;

[0098] When the accident level is R3, there may be a certain amount of leakage at the shield tail. Increase the grease sealing pressure and injection volume until the leakage is completely blocked.

[0099] When the accident level is R4 or R5, the shield should stop excavation immediately, increase the shield tail sealing strength, increase the shield tail sealing grease pumping speed, and enhance the sealing effect. If the sealing work is still unable to work, the personnel should be organized to evacuate the construction site quickly.

[0100] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for evaluating the risk of shield tail seal failure based on numerical simulation, characterized in that: include: Identify failure influencing factors, including external load combined force influencing factors and internal pressure influencing factors Obtain the external load resultant force and internal pressure to be evaluated of the shield tail sealing device; Input the external load resultant force and internal pressure to be evaluated into a numerical simulation model, and output a numerical simulation result, wherein the numerical simulation model is composed of a shield tail brush and a sealing grease cavity; The numerical simulation results are analyzed in combination with the influencing factors to obtain the risk level of the shield tail sealing device.

2. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 1 is characterized in that: The external load resultant force includes: water and soil pressure resultant force and synchronous grouting pressure.

3. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 2 is characterized in that: The calculation method of the water-soil pressure is: q w =γ·h0 h0=0.45×2 s-1 ·oh ω=1+i(B+5) Among them, q w is the resultant of water and soil pressure, γ is the bulk density of the surrounding rock, h0 is the average height of the construction collapse, S is the surrounding rock grade of the surrounding strata, ω is the width influence coefficient, B is the tunnel width, and i is the rate of increase or decrease of surrounding rock pressure when the tunnel width B increases or decreases by 1m.

4. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 1 is characterized in that: The influencing factors of the internal pressure include: linkage integrity of the shield tail seal device and durability of the wire brush of the shield tail seal device; The linkage integrity of the shield tail sealing device is related to the grease pressure in the sealing grease cavity and the amount of sealing grease injected; The durability of the wire brush of the shield tail sealing device is related to the assembly quality of the segments and the working posture quality of the shield machine.

5. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 1 is characterized in that: The method for obtaining the internal pressure is: q2=μ·q d Where q2 is the internal pressure, μ is the attenuation coefficient, and q d is the grease pressure of the shield tail sealing device, a is the linkage integrity coefficient of the shield tail sealing device, and b is the durability coefficient of the shield tail sealing wire brush.

6. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 1 is characterized in that: The numerical simulation model is simulated using FLUENT.

7. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 1 is characterized in that: The numerical simulation results are analyzed to obtain the risk level of the shield tail sealing device, including: When the numerical simulation result shows that there is no leakage, it is determined to be a first-level risk; When the numerical simulation result shows a small amount of slurry leakage, it is determined to be a secondary risk; When the numerical simulation result shows that there is a certain amount of slurry leakage at the shield tail, it is determined to be a level 3 risk; When the numerical simulation result shows that the leakage amount at the shield tail is large, but the leakage rate is slow, it is determined to be a level 4 risk; When the numerical simulation result shows that there is a large amount of slurry leakage at the shield tail and the leakage speed is very fast, it is determined to be a level five risk.

8. A method for evaluating the risk of shield tail seal failure based on numerical simulation according to any one of claims 1 to 7, characterized in that: The method also includes: performing prevention and control according to the risk level.

9. The method for evaluating the risk of shield tail seal failure based on numerical simulation according to claim 8 is characterized in that: According to the risk level, prevention and control measures include: When the risk level is the first-level risk or the second-level risk, no prevention and control is required; When the risk level is the third level risk, increase the high-quality sealing pressure and injection volume; When the risk level is the fourth or fifth risk, the shield machine should stop excavating, increase the shield tail sealing force, and increase the shield tail sealing grease pumping speed.

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