Slurry shield anti-caking mud cake bin soaking method

Abstract

The invention discloses a slurry shield mud cake formation preventing and bin soaking method which comprises the following steps: S1, stratum analysis: performing stratum analysis of current section tunneling of a large-diameter slurry shield, and analyzing whether the stratum is a high-viscosity stratum or not; s2, starting tunneling, to be more specific, on the premise that excavation face stratums are basically consistent, water pressure fluctuation of a notch is within + / -0.1 bar range, and tunneling speed is stable, if propulsion thrust is increased by 10%, total telescopic thrust of a cutterhead is increased by 8%, in a second stage, and before tunneling parameters reach the second stage, stopping a machine to adopt a dispersing agent bubble bin; s3, dispersing agent injection, wherein an injection ball valve is installed in the section, before the center washing pipeline enters the muddy water bin, of the center washing pipeline to serve as an injection point of a dispersing agent; arranging a grouting pipeline for injecting a dispersing agent, wherein the grouting pipeline is communicated with a plurality of grouting ball valves; s4, washing the mud cake in the bubble bin: after the dispersing agent is injected, washing the central area of the cutterhead at high pressure by utilizing a central washing pipeline. The method solves the problem that mud cakes are difficult to eliminate when a traditional method is used for carrying out bin soaking treatment.

Description

Technical Field

[0001] The invention belongs to the technical field of shield construction, and in particular relates to a method for preventing mud cake from forming and bubbling in a slurry shield. Background Art

[0002] When a shield machine is excavating in clay strata, the debris is easily adhered to the cutterhead and soil compartment due to shear friction, extrusion consolidation, and high temperature. If not handled in time, the shield load will increase, the tool cutting efficiency will decrease, and the shield machine will have difficulty in removing debris, which will seriously affect the construction efficiency and safety of the shield machine.

[0003] When an ultra-large diameter slurry shield tunnels in viscous strata, mud cakes form on the cutterhead or slurry bin. Dispersants are generally used to soak the slurry bin. The traditional approach is to inject dispersants through a ball valve reserved in the slurry bin wall and eliminate the mud cakes by regularly rotating the cutterhead.

[0004] The following problems exist in using this method to eliminate mud cakes: first, signs of mud cake formation are not predicted in advance during shield construction, and only when the tunneling parameters deteriorate seriously do the foaming chambers take action to eliminate or soften the mud cakes, resulting in the dispersant foaming chamber effect not meeting the expected requirements; second, the dispersant is injected through the bulkhead ball valve, and the foaming chamber requires a large amount of dispersant to be injected, resulting in a large construction investment; finally, the dispersant cannot be used to its maximum effect simply by rotating the cutterhead. Summary of the Invention

[0005] The present invention provides a method for preventing mud cake from forming and bubbling the chamber of a slurry shield, so as to solve the problem that it is difficult to eliminate mud cakes when a super-large diameter slurry shield is excavating in a viscous stratum using traditional methods for bubbling the chamber.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for preventing mud cake from forming and soaking in a slurry shield comprises the following steps: S1, Stratum Analysis: Conduct stratigraphic analysis of the current section of the large-diameter slurry shield tunnel to determine whether the stratigraphic layer is highly viscous. If so, special attention should be paid to the possibility of mud cake formation on the cutterhead or slurry bin. S2, start of excavation: Under the premise that the excavation surface strata are basically consistent, the incision water pressure fluctuation is within the range of ±0.1bar, and the excavation speed is stable, if the thrust increases by 5% and the total thrust of the cutterhead extension increases by 4%, it is in the first stage; if the thrust increases by 10% and the total thrust of the cutterhead extension increases by 8%, it is in the second stage. Before the excavation parameters reach the second stage, it is necessary to stop the machine and use the dispersant soaking tank; S3, dispersant injection: Install an injection ball valve in the section before the central flushing pipeline enters the mud and water tank as the dispersant injection point; set up a grouting pipeline for dispersant injection, and the grouting pipeline is connected to multiple injection ball valves; S4, flushing the mud cake in the bubble chamber: After the dispersant is injected, close the injection ball valve and use the central flushing pipeline to flush the center area of ​​the cutter head at high pressure, and flush it multiple times at intervals.

[0007] Furthermore, in step S3, when using the dispersant foaming tank, the shield machine mud and water tank adopts the air pressure assistance mode, and the mud and water tank liquid level is controlled at 0.6 to 1.0 m above the center of the cutter head.

[0008] Furthermore, in step S3, 16 dispersant injection holes are set in the center area of ​​the cutter head, and the injection amount of each hole is controlled to be 0.2 to 0.3 m³.

[0009] Furthermore, in step S3, before injecting the dispersant, all the original ball valves installed in the flushing pipeline need to be closed so that all the dispersant can be injected into the mud and water tank.

[0010] Furthermore, in step S3, the ratio of the dispersant injection amount to the mud amount in the mud and water tank is not less than 0.02.

[0011] Furthermore, in step S4, the shield machine stops excavating and uses the central flushing pipeline to flush the center area of ​​the cutter head at high pressure. Each flushing time is 15 minutes, and the cutter head is rotated once every 2 hours.

[0012] Furthermore, in step S4, the time for flushing the mud cake in the soaking bin needs to reach 24 hours.

[0013] Furthermore, in step S4, firstly, all the injection ball valves are closed, and the flushing pipeline is switched to the backwashing pipeline, and then the central flushing pipeline is used for high-pressure flushing.

[0014] Furthermore, in step S4, after the flushing pipeline is switched to the backwashing pipeline, the flushing pipeline directly takes slurry from the mud and water tank, and then uses the taken-out slurry to flush the cutter head.

[0015] Furthermore, the grouting pipeline includes a dispersant storage tank, a high-pressure grouting machine and a high-pressure grouting pipe. The dispersant storage tank is connected to the high-pressure grouting machine, and the multiple injection ball valves are connected to the high-pressure grouting machine through the high-pressure grouting pipe.

[0016] The present invention can achieve the following beneficial effects: (1) Real-time monitoring and analysis of stratum type and tunneling parameters, such as total shield thrust and total cutterhead extension thrust, can effectively determine whether the cutterhead or mud-water tank is in the early stage of mud cake formation. In particular, implementing a soaking tank before the second stage, when the thrust increases by 10% and the cutterhead extension thrust increases by 8%, can significantly reduce the probability of entering the severe mud cake stage and avoid high-risk and high-cost methods such as pressurized chamber cleaning, thereby improving construction efficiency and control initiative from the source.

[0017] (2) A high-pressure explosion-proof injection ball valve is installed in the center of the cutterhead to inject dispersant at a fixed point. Compared with the traditional injection method through the bulkhead, this method is closer to the initial accumulation area of ​​the mud cake, effectively improving the targeting and local concentration of the dispersant, thereby significantly improving the dispersion and softening efficiency of the mud cake.

[0018] (3) Traditional pressure cleaning operations require manual entry into a high-pressure mud and water tank, which carries serious risks such as decompression sickness, personal entrapment, and local instability of the tunnel face. However, in this method, the dispersant injection and flushing operations are completed outside the shield machine body, and operators do not need to enter the cabin, greatly improving construction safety.

[0019] (4) During the soaking process, air pressure assistance is used to maintain the mud and water tank level at a height of 0.6 to 1.0 m above the center of the cutterhead. This helps the dispersant to be evenly distributed and floated in the mud and water, achieving more comprehensive coverage and dispersion of the mud cake area, effectively improving the use efficiency of the dispersant, and thus reducing the consumption of dispersant required per soaking tank. After the operation, the injected dispersant enters the shield's mud and water circulation system with the mud. After continuous dilution and discharge, it will not form solid residues or high-concentration pollution on site. It is more environmentally friendly than traditional mechanical cleaning methods and does not require additional waste liquid treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the accompanying drawings and examples: Figure 1 This is a schematic diagram of the present invention for illustrating the installation position of the injection ball valve; Figure 2 This is a schematic diagram of the present invention for illustrating the injection ball valve and the grouting pipeline; Figure 3 is a schematic diagram of the air pressure assist mode of the present invention; Figure 4 This is a schematic diagram of the mud flow path after the flushing pipeline is switched to the backwashing pipeline in the present invention. In the accompanying drawings, the components represented by the reference numerals are as follows: 1. Injection ball valve; 2. Original ball valve; 3. Dispersant storage tank; 4. High-pressure grouting machine; 5. High-pressure grouting pipe. DETAILED DESCRIPTION The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the present invention.

[0021] In addition, described feature, structure or characteristic can be combined in one or more embodiments in any suitable manner.In the following description, many specific details are provided so as to provide a full understanding of the embodiments of the present application. However, it will be appreciated by those skilled in the art that the technical scheme of the present application can be put into practice without one or more of the specific details, or other methods, components, devices, steps etc. can be adopted. In other cases, known methods, devices, implementations or operations are not shown or described in detail to avoid blurring the various aspects of the application.

[0022] This embodiment provides a method for preventing mud cake from forming and bubbling in a slurry shield, comprising the following steps: S1, Stratum analysis: Conduct stratigraphic analysis of the current section of the large-diameter slurry shield tunneling to analyze whether the stratigraphic layer is a high-viscosity stratigraphic layer. If it is a high-viscosity stratigraphic layer, that is, the content of fine particles less than 5μm in the soil layer accounts for 15% or more, special attention should be paid to the easy formation of mud cakes in the cutterhead or slurry bin.

[0023] S2: Start excavation. Under the premise that the excavation surface strata are basically consistent, the incision water pressure fluctuation is within the range of ±0.1 bar, and the excavation speed is stable: if the thrust increases by 5%, the total thrust of the cutterhead extension and retraction increases by 4%, it is in the first stage; if the thrust increases by 10% and the total thrust of the cutterhead extension and retraction increases by 8%, it is in the second stage. Before the excavation parameters reach the second stage, it is necessary to stop the machine and use the dispersant soaking tank; S3, dispersant injection: an injection ball valve (1) is installed in the section before the central flushing pipeline enters the mud and water tank as the dispersant injection point; a grouting pipeline for dispersant injection is provided, and the grouting pipeline is connected to a plurality of injection ball valves (1); S4, flushing the mud cake in the bubble chamber: After the dispersant is injected, close the injection ball valve 1, and use the central flushing pipeline to flush the center area of ​​the cutter head at high pressure, and flush it multiple times at intervals.

[0024] Among them, in step S2, when a large-diameter slurry shield is excavating in a viscous stratum, it is necessary to choose a suitable time to soak the dispersant tank according to the occurrence of mud cakes on the cutterhead or slurry tank. Since the occurrence of mud cakes on the cutterhead or slurry tank cannot be observed, it is necessary to judge based on other excavation parameters.

[0025] Based on experience with large-diameter shield tunneling, under normal excavation conditions, the total shield thrust and the total cutterhead extension thrust will vary with increasing tunnel depth and incision pressure and changes in the ground. In clayey soil formations prone to mud cake formation, the presence of mud cake on the cutterhead requires effective analysis using these two parameters.

[0026] Under the condition that the strata at the excavation face are basically consistent, the fluctuation of the incision water pressure is within the range of ±0.1bar, and the excavation speed is stable: if the total thrust of the shield machine increases by 5% and the total thrust of the cutterhead extension increases by 4%, it is in the first stage. In the first stage, it is necessary to pay attention to the slight cake formation in the cutterhead or mud water bin. If the total thrust of the shield machine increases by 10% and the total thrust of the cutterhead extension increases by 8%, it is in the second stage. In the second stage, it is necessary to pay attention to the beginning of cake formation on the cutterhead. If the total thrust of the shield machine increases by 15% and the total thrust of the cutterhead extension increases by 12% or more, it is in the third stage. In the third stage, the cutterhead is severely caked, and measures such as air pressure assistance and dispersant soaking are limited in effect. It is necessary to open the bin under pressure and manually clean the mud cake.

[0027] Therefore, the timing for using dispersant to soak the tank is before the start of the second stage, when the dispersant soaking effect is the best. This application uses stratigraphic research and tunneling parameter analysis to determine signs of mud cake formation on the cutterhead or mud water tank, thereby providing the best time to soak the tank with dispersant, avoiding the high risk, long construction period and high cost of using pressure to clean mud cake when the cutterhead is seriously caked.

[0028] Among them, in step S3, combined with the previous excavation conditions of small-diameter shield or large-diameter slurry shield, in the viscous stratum, the mud cake formed on the cutter head or slurry bin starts from the central area and then spreads to the surrounding areas. Therefore, the construction method of the present application injects a dispersant from the central area of ​​the cutter head or slurry bin to improve the efficiency of cleaning the mud cake.

[0029] For large-diameter slurry shields, the shield machine is equipped with a flushing pipeline at the cutterhead. The multiple flushing ports of the flushing pipeline pass through the slurry bin and extend into the cutterhead, and the internal space of the cutterhead is connected to the internal space of the slurry bin. The portion of the flushing pipeline in the center area of ​​the cutterhead is defined as the central flushing pipeline in this application. The multiple pipes of the central flushing pipeline are in the section before they extend into the slurry bin, and an injection ball valve 1 for injecting dispersant is reserved. The dispersant is injected into the flushing pipeline through the injection ball valve 1, and is injected into the cutterhead through the multiple flushing pipes of the flushing pipeline, so as to realize the bubbling of the dispersant, thereby improving the effect of the dispersant in eliminating mud cakes.

[0030] like Figure 1 As shown in the figure, based on the on-site construction conditions, the L01-L08 cutterhead center panels and the L09-L12 bullpup flushing lines correspond to the center area of ​​the cutterhead, also corresponding to the center flushing line. A 1-inch high-pressure explosion-proof ball valve, designated injection ball valve 1, is installed before the center flushing line enters the slurry tank. This serves as the dispersant injection point. Sixteen dispersant injection holes are located in the center of the cutterhead, with the injection volume per hole controlled at 0.2-0.3 m³. To improve dispersant dispersion efficiency, a ratio of dispersant injection volume / slurry volume in the slurry tank of ≥ 0.02 is used.

[0031] like Figure 2 As shown, a grouting pipeline for injecting dispersant is provided, and the grouting pipeline includes a high-pressure grouting machine 4 and a high-pressure grouting pipe 5. The high-pressure grouting machine 4 is connected to a plurality of injection ball valves 1 installed on the central flushing pipeline through the high-pressure grouting pipe 5. The dispersant storage tank 3 is connected to the high-pressure grouting machine 4, and the dispersant is injected into the mud and water tank through the grouting pipeline and the central flushing pipeline. It should be noted that before the central flushing pipeline is connected to the grouting pipeline, the original ball valve 2 installed on the original pipeline of the central flushing pipeline needs to be closed to ensure that all the dispersant is injected into the mud and water tank. The injection point of the dispersant bubble tank is selected at the center area of ​​the cutter head panel, and the dispersant directly enters the mud cake area to improve the efficiency of the dispersant in eliminating the mud cake.

[0032] like Figure 3 As shown in the figure, to improve the dispersing efficiency of the dispersant, the ratio of the dispersant injection volume to the mud volume in the mud and water tank should be no less than 0.02. At the same time, when the mud and water tank is started to be soaked, the air pressure-assisted mode is adopted in the mud and water tank, that is, the upper part of the mud and water tank is compressed air, and the lower part is mud. The mud is pressed to the lower half of the mud and water tank by compressed air, thereby increasing the concentration of the dispersant and the volume content of the dispersant in the mud. While ensuring the dispersant soaking effect, the use of dispersant can be further reduced. It should be noted that the mud level in the mud and water tank needs to be controlled at 0.6 to 1.0 m above the center point of the cutterhead.

[0033] Furthermore, in step S4, the mud cake is flushed by soaking the tank, as shown in FIG. Figure 4 As shown in the figure, after dispersant injection is completed, the injection ball valve 1 used for dispersant injection is first closed. Then, the existing ball valve 2 in the flushing line is opened, and the center flushing line is switched to backwashing mode, allowing slurry to be directly drawn from the mud and water tank. The P0.1 pump is started to flush the center area of ​​the cutterhead with high pressure. During this period, the cutterhead is rotated once every two hours for a flushing period of 15 minutes. The P0.1 pump is used to flush the center area of ​​the mud and water tank by central flushing. The slurry is drawn from the mud and water tank by high-pressure flushing. That is, the mud that has been washed with dispersant and flushed through the cutterhead is returned to the center flushing line and then injected into the mud and water tank again through the center flushing line for flushing. This dual operation of dispersant and high-pressure flushing maximizes the dispersant's ability to eliminate and soften the mud cake, improves the dispersant's effectiveness, and increases the efficiency of the tank soaking.

[0034] In addition, the recycling of mud in the mud and water tank can further bring out the effectiveness of the dispersant and save the amount of dispersant. It should be noted that the shield machine stops excavating during the process of cleaning the mud cake. In order to ensure the effect of the tank soaking, the tank soaking time generally takes 24 hours. This embodiment intervenes in the early stage of the mud cake, which can avoid the shield machine being shut down for cleaning due to severe consolidation of the mud cake in the later stage. Actual measurements show that in a large-diameter shield section, when the proportion of clay in the stratum exceeds 60%, it usually takes 70 days to use manual pressure cleaning to treat the mud cake. However, the use of this dispersant tank soaking method can shorten this time to 20 days, saving a total of about 50 days of construction time, significantly improving the efficiency of project advancement.

[0035] In summary, the present invention discloses a method for preventing mud cake from forming in a slurry shield. Relying on formation analysis and tunneling parameter monitoring, the risk of mud cake formation in the cutterhead and slurry bin can be predicted in advance, and by setting an injection point in the center area of ​​the cutterhead, combined with the injection of dispersant and the combined effects of air pressure assistance and high-pressure flushing, the mud cake can be effectively dispersed and removed. This method not only improves the efficiency of dispersant use and the effect of bunker bubbling, but also significantly reduces the frequency and risk of manual pressure cleaning operations, saving construction time and costs. In the construction of large-diameter slurry shields, the present invention provides a risk-controlled, more efficient, and safer means of mud cake control, which has important engineering application value and promotion significance for promoting the intelligent construction of tunnel boring equipment and improving adaptability to complex formations.

[0036] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of the different aspects of the present invention as described above. For the sake of simplicity, they are not provided in detail. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in this field should understand that it is still possible to modify the technical solutions described in the above embodiments, or to make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preventing mud cake from forming in a slurry shield, characterized in that: The following steps are involved: S1, Stratum Analysis: Conduct stratigraphic analysis of the current section of the large-diameter slurry shield tunnel to determine whether the stratigraphic layer is highly viscous. If so, special attention should be paid to the possibility of mud cake formation on the cutterhead or slurry bin. S2, start of excavation: Under the premise that the excavation surface strata are basically consistent, the incision water pressure fluctuation is within the range of ±0.1bar, and the excavation speed is stable, if the thrust increases by 5% and the total thrust of the cutterhead extension increases by 4%, it is in the first stage; if the thrust increases by 10% and the total thrust of the cutterhead extension increases by 8%, it is in the second stage. Before the excavation parameters reach the second stage, it is necessary to stop the machine and use the dispersant soaking tank; S3, dispersant injection: an injection ball valve (1) is installed in the section before the central flushing pipeline enters the mud and water tank as the dispersant injection point; a grouting pipeline for dispersant injection is provided, and the grouting pipeline is connected to a plurality of injection ball valves (1); S4, flushing the mud cake with the bubble chamber: After the dispersant is injected, close the injection ball valve (1) and use the central flushing pipeline to flush the center area of ​​the cutter head with high pressure for multiple times at intervals.

2. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: In step S3, when using the dispersant foaming tank, the shield machine mud and water tank adopts the air pressure assistance mode, and the mud and water tank liquid level is controlled at 0.6 to 1.0 m above the center of the cutter head.

3. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: In step S3, 16 dispersant injection holes are set in the center area of ​​the cutter head, and the injection volume of each hole is controlled at 0.2 to 0.3 m³.

4. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: In step S3, before injecting the dispersant, all the original ball valves (2) installed in the original pipeline of the flushing pipeline need to be closed to allow the dispersant to be fully injected into the mud and water tank.

5. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: In step S3, the ratio of the dispersant injection amount to the mud amount in the mud and water tank is not less than 0.

02.

6. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: In step S4, the shield machine stops excavating and uses the central flushing pipeline to flush the center area of ​​the cutter head at high pressure. Each flushing time is 15 minutes, and the cutter head is rotated once every 2 hours.

7. A method for preventing mud cake from forming in a slurry shield according to claim 6, characterized in that: In step S4, the time for flushing the mud cake in the soaking bin needs to reach 24 hours.

8. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: In step S4, firstly, all the injection ball valves (1) are closed, and the flushing pipeline is switched to the backwashing pipeline, and then the central flushing pipeline is used for high-pressure flushing.

9. A method for preventing mud cake from forming in a slurry shield according to claim 8, characterized in that: In step S4, after the flushing pipeline is switched to the backwashing pipeline, the flushing pipeline directly takes slurry from the mud and water tank, and then uses the taken-out slurry to flush the cutter head.

10. A method for preventing mud cake from forming in a slurry shield according to claim 1, characterized in that: The grouting pipeline comprises a dispersant storage tank (3), a high-pressure grouting machine (4) and a high-pressure grouting pipe (5); the dispersant storage tank (3) is connected to the high-pressure grouting machine (4); and a plurality of injection ball valves (1) are connected to the high-pressure grouting machine (4) via the high-pressure grouting pipe (5).

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