A method for maintaining mud film on the tunnel face during pressure opening operation of a large-diameter slurry shield

Abstract

The present invention relates to the technical field of urban underground engineering construction, and specifically to a method for maintaining the mud film on the face of a large-diameter slurry shield during a pressurized opening operation: after the pressurized opening operation, a high-pressure spray gun is used to spray high-viscosity bentonite on the cracks of the mud film on the face of the face, so that the high-viscosity bentonite penetrates into the cracks to fill and seal the cracks, and the number of spraying is at least one; the high-viscosity bentonite is prepared by a grouting agent, bentonite, and water in a ratio of 1:15-20:35-40. The present invention can greatly improve the maintenance efficiency of the mud film on the face of a large slurry shield during a pressurized opening operation, and at the same time, there is no need to repeatedly pressurize and depressurize during the opening operation, thereby reducing the health risks to operators caused by pressure changes.

Description

Technical Field

[0001] The invention relates to the technical field of urban underground engineering construction, and in particular to a method for maintaining a mud film on a tunnel face during a pressure-opening operation of a large-diameter slurry shield. Background Art

[0002] When shield machines are excavating in complex and changeable strata, abnormal wear of the cutters often occurs, and it is necessary to open the cabin for inspection and replacement of the cutters. In recent years, with the development of shield manufacturing technology, shield machines have developed in the direction of large diameter and large burial depth, and large-diameter normal pressure cutterheads have been developed. When the cutters are abnormally worn, they only need to be replaced under the normal pressure environment of the cutterhead radial arm, thereby improving construction efficiency. Although the normal pressure cutterhead solves the problem of opening the cabin under pressure to change the cutter, the shield machine will still face problems such as damage to the crusher, mud cake on the cutterhead, and failure of the main drive seal. At this time, it is still necessary to enter the cabin for inspection in time and deal with the fault phenomenon. However, due to the high difficulty and high risk of shield cabin opening operations under high water pressure, high permeability and complex geological conditions, improper handling often leads to adverse consequences such as collapse of the excavation face and groundwater breakthrough. Therefore, the stability of the mud film on the face is the key to the success of the cabin opening. Pressurized hatch opening is a method of using mud to form a closed mud film on the excavation surface, and then using air pressure to balance the corresponding water and soil pressure, and opening the hatch under air pressure support (CN104121023A: Testing device and method for the air-tightness value of the mud film on the excavation surface during pressurized hatch opening of a slurry shield). At present, pressurized hatch opening requires a pressurization and decompression process, which consumes a lot of time. Frequent pressurization and decompression have a certain impact on the health of the personnel entering the cabin. Therefore, how to continuously maintain the stability of the mud film on the face, avoid cracks and perforations in the mud film under pressure when the pressurized hatch opening time is long, and provide a stable and safe working environment for the personnel entering the cabin, has become a problem that the shield industry has always been concerned about. The current practice is that during the hatch opening operation, the pressure in the excavation chamber gradually decreases and cannot be maintained, which means that cracks may appear in the mud film, and personnel need to evacuate and re-grout the excavation chamber to form a new mud film. This method is time-consuming and increases costs. On this basis, researchers developed a new method (CN111042825 A: Repair method for deterioration of mud film on excavation surface during pressure balance shield tunneling under pressure - breathable), which is to evenly apply mud to the cracks of mud film with a brush, increase the pressure of the excavation chamber, maintain it for a period of time to allow mud to penetrate into the cracks, and through repeated operations, a new mud film is formed, and then the pressure is reduced for cabin construction. Compared with traditional methods, this method is more efficient, but it still requires repeated pressurization and decompression. The personnel entering the cabin use a brush to apply the mud, which has a small effective area and low operating efficiency. Summary of the invention

[0003] In view of the technical problems in the prior art such as low efficiency of mud film maintenance on the tunnel face of large shield machines and the need for repeated pressurization and decompression of the pressure cabin, the present invention provides a method for maintaining the mud film on the tunnel face when a large-diameter slurry shield machine is opened under pressure, which greatly improves the maintenance efficiency of the mud film on the tunnel face when a large slurry balance shield machine is opened under pressure. At the same time, there is no need for repeated pressurization and decompression during the cabin opening operation, thereby reducing the health risks to operators caused by pressure changes.

[0004] The present invention provides a method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield: after the pressure opening, a high-pressure spray gun is used to spray high-viscosity bentonite on the cracks of the mud film on the tunnel face, so that the high-viscosity bentonite penetrates into the cracks to fill and seal the cracks, and the number of spraying is at least one;

[0005] The high viscosity bentonite is prepared by grouting agent, montmorillonite and water in a weight ratio of 1:15-20:35-40. The grouting agent is a conventional grouting agent used in the prior art, and the grouting agent is a grouting agent refined by high-performance plasticizer, surfactant, silicon calcium micro-expansion agent, hydration heat inhibitor, migration type rust inhibitor, nano-scale mineral silicon aluminum calcium iron powder, stabilizer or a grouting material refined and compounded with low alkali and low heat silicate cement.

[0006] Furthermore, before opening the cabin under pressure, the cabin entry pressure is determined through theoretical calculations and pressure-maintaining and pressure-reducing tests. It is necessary to ensure that the cabin entry pressure can be reduced as much as possible while ensuring good quality of the mud film, so as to extend the cabin entry working time.

[0007] Furthermore, the viscosity of the prepared high-viscosity bentonite is 40-60s, and the viscosity is the Marsh funnel viscosity.

[0008] Furthermore, the injection flow rate is adjusted according to the size and position of the mud film cracks on the face. If the cracks are large, the injection flow rate is increased; if the cracks are small, the injection flow rate is reduced. The standard is that high-viscosity bentonite completely fills the cracks. The purpose is to spray mud in an amount suitable for the size of the cracks and fill the cracks more fully.

[0009] Furthermore, the sprayed high-viscosity bentonite is in a spray form, making the spraying more uniform.

[0010] Furthermore, when opening the cabin, observe the mud film on the face and the pressure fluctuations in the pressure cabin. If cracks or pressure fluctuations appear, spray high-viscosity bentonite again until no cracks are observed with the naked eye or the pressure stabilizes.

[0011] Furthermore, after crack spraying is completed, if the air pressure in the pressure chamber is unstable, high-viscosity bentonite is sprayed all over the mud film on the face until the pressure in the pressure chamber is stable, thereby reducing adverse effects caused by mud film cracks that cannot be observed by the naked eye.

[0012] Furthermore, the high-pressure spray gun is handheld and adopts pneumatic pressure control, and the air pressure control range is: 11-12bar.

[0013] Furthermore, the density of high viscosity bentonite is 0.2-0.4 g / cm2 less than that of the hatch mud. 3 On the one hand, its function is that its low density ensures a better spray effect during the mud film maintenance process, making it easier for the high-viscosity bentonite to be evenly distributed and penetrate into the cracks of the mud film; on the other hand, when the high-viscosity bentonite fills the cracks in the face, it further absorbs water, causing the liquid to swell when it comes into contact with water, thereby effectively filling the cracks.

[0014] As a preferred technical solution:

[0015] The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to the present invention specifically comprises the following steps:

[0016] (1) Before opening the tank under pressure, confirm the required tank entry pressure based on calculation and test;

[0017] (2) Mix the grouting agent for hatch opening, montmorillonite and water to prepare high-viscosity bentonite, and place the prepared high-viscosity bentonite in a high-pressure spray gun;

[0018] (3) After entering the cabin, the personnel shall observe the surface condition of the mud film on the tunnel face, determine the size and position of the mud film cracks, adjust the corresponding operating parameters, and use a high-pressure spray gun to spray high-viscosity bentonite on the cracks, with the standard being that the high-viscosity bentonite completely covers the cracks;

[0019] (4) During the opening operation, observe the surface condition of the tunnel face. If new cracks appear, repeat the injection of high-viscosity bentonite to dynamically maintain the mud film on the tunnel face;

[0020] (5) After the injection operation is completed, if there are no cracks on the mud film on the tunnel face and / or the pressure in the pressure chamber fluctuates, no other operations are required on the mud film on the tunnel face. If there are cracks on the mud film on the tunnel face and / or the pressure in the pressure chamber fluctuates, high-viscosity bentonite should be fully injected on the mud film on the tunnel face.

[0021] The principle of the present invention is as follows: the present invention adopts high-viscosity bentonite to fill the cracks of mud film, and the montmorillonite in the high-viscosity bentonite can make the high-viscosity bentonite expand after infiltrating into the cracks, so as to fill the cracks; the grouting agent can make the prepared slurry have higher strength and elastic modulus, expansion without shrinkage and adhesion after hardening, and can make the slurry in the cracks full and dense; the purpose of water in the raw materials is to make the high-viscosity bentonite maintain a certain fluidity, which is convenient for spraying with a spray gun; the high-viscosity bentonite with the ratio of the above raw materials has the best performance; at the same time, the present invention adopts a high-pressure spray gun to fill the cracks appearing on the mud film of the face, which is efficient and easy to operate, and is suitable for the maintenance of the mud film of the face during the pressure opening operation of a large-diameter mud-water shield.

[0022] The beneficial effects of the present invention are:

[0023] The method for maintaining the mud film on the face of a large-diameter mud-water shield during pressurized cabin opening operation provided by the present invention adopts high-viscosity bentonite prepared by mixing a grouting agent, bentonite and water in proportion as the mud film maintenance mud, which has the characteristics of high viscosity, light weight and easy expansion, and is easy to form a uniform spray; a high-pressure spray gun is used to fill cracks on the mud film on the face of the tunnel, and the moistening of the face of the tunnel is maintained, so that the air tightness and stability of the mud film can be effectively guaranteed; the operation is simple and convenient; the high-pressure spray gun device is used to have a large spraying area and a short spraying time; and there is no need to repeatedly pressurize the air pressure cabin, thereby reducing the health risks of construction personnel, and rapid dynamic maintenance of the mud film on the face of a large diameter tunnel can be achieved.

[0024] After the mud film cracks on the tunnel face are treated by the present invention, no additional treatment is required, which is convenient and efficient. DETAILED DESCRIPTION

[0025] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention are described clearly and completely below. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0026] Example 1

[0027] The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to the present invention specifically comprises the following steps:

[0028] (1) Before opening the tank under pressure, theoretical calculation and pressure maintenance and pressure reduction test shall be conducted to determine that the pressure of the tank under pressure should be reduced as much as possible while ensuring good mud film quality, so as to extend the working time of the tank under pressure;

[0029] (2) Mix and stir grouting agent, bentonite and water to prepare mud membrane maintenance mud. The mass ratio of grouting agent, bentonite and water is 1:18:38. The viscosity of the bentonite mixture mud is maintained at 50s. The density of high-viscosity bentonite is 0.3g / cm2 less than that of the hatch opening mud. 3 ;

[0030] (3) When entering the cabin, the staff shall carry high-viscosity bentonite and a high-pressure spray gun. Observe the size and position of the cracks on the face mud film and spray high-viscosity bentonite. If the cracks are large, adjust the spray flow rate and increase the spraying amount. At the same time, adjust the air pressure of the high-pressure spray gun. The high-pressure spray gun is handheld and uses pneumatic pressure control. The air pressure control range is: 11-12bar, so that the sprayed high-viscosity bentonite is in a spray state, which is easy to distribute evenly. After the spraying work is completed, check the pressure fluctuation of the air pressure chamber. If the air pressure is unstable, there are still cracks on the surface of the mud film that cannot be observed by the naked eye. In this case, spray the face mud film with high-viscosity bentonite slurry all over until the pressure fluctuation of the air pressure chamber stabilizes.

[0031] (4) During the opening operation, observe the mud film on the tunnel face and the pressure fluctuations in the air pressure chamber. If cracks and / or pressure instability occur, spray high-viscosity bentonite again to achieve dynamic maintenance of the mud film on the tunnel face.

[0032] (5) After the tunnel face mud film is sprayed with high-viscosity bentonite, if no cracks and / or pressure instability occur, no additional treatment of the mud film is required.

[0033] Example 2

[0034] The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to the present invention specifically comprises the following steps:

[0035] (1) Before opening the tank under pressure, theoretical calculation and pressure maintenance and pressure reduction test shall be conducted to determine that the pressure of the tank under pressure should be reduced as much as possible while ensuring good mud film quality, so as to extend the working time of the tank under pressure;

[0036] (2) Mix and stir grouting agent, bentonite and water to prepare mud membrane maintenance mud. The mass ratio of grouting agent, bentonite and water is 1:15:40. The viscosity of the bentonite mixture mud is maintained for 40 seconds. The density of high-viscosity bentonite is 0.2 g / cm2 less than that of the hatch opening mud. 3 ;

[0037] (3) When entering the cabin, the staff shall carry high-viscosity bentonite and a high-pressure spray gun. Observe the size and position of the cracks on the face mud film and spray high-viscosity bentonite. If the cracks are large, adjust the spray flow rate and increase the spraying amount. At the same time, adjust the air pressure of the high-pressure spray gun. The high-pressure spray gun is handheld and uses pneumatic pressure control. The air pressure control range is: 11-12bar, so that the sprayed high-viscosity bentonite is in a spray state, which is easy to distribute evenly. After the spraying work is completed, check the pressure fluctuation of the air pressure chamber. If the air pressure is unstable, there are still cracks on the surface of the mud film that cannot be observed by the naked eye. In this case, spray the face mud film with high-viscosity bentonite slurry all over until the pressure fluctuation of the air pressure chamber stabilizes.

[0038] (4) During the opening operation, observe the mud film on the tunnel face and the pressure fluctuations in the air pressure chamber. If cracks and / or pressure instability occur, spray high-viscosity bentonite again to achieve dynamic maintenance of the mud film on the tunnel face.

[0039] (5) After the tunnel face mud film is sprayed with high-viscosity bentonite, if no cracks and / or pressure instability occur, no additional treatment of the mud film is required.

[0040] Example 3

[0041] The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to the present invention specifically comprises the following steps:

[0042] (1) Before opening the tank under pressure, theoretical calculation and pressure maintenance and pressure reduction test shall be conducted to determine that the pressure of the tank under pressure should be reduced as much as possible while ensuring good mud film quality, so as to extend the working time of the tank under pressure;

[0043] (2) Mix and stir grouting agent, bentonite and water to prepare mud membrane maintenance mud. The mass ratio of grouting agent, bentonite and water is 1:20:35. The viscosity of the bentonite mixture mud is maintained for 60 seconds. The density of high-viscosity bentonite is 0.4 g / cm2 less than that of the hatch opening mud. 3 ;

[0044] (3) When entering the cabin, the staff shall carry high-viscosity bentonite and a high-pressure spray gun. Observe the size and position of the cracks on the face mud film and spray high-viscosity bentonite. If the cracks are large, adjust the spray flow rate and increase the spraying amount. At the same time, adjust the air pressure of the high-pressure spray gun. The high-pressure spray gun is handheld and uses pneumatic pressure control. The air pressure control range is: 11-12bar, so that the sprayed high-viscosity bentonite is in a spray state, which is easy to distribute evenly. After the spraying work is completed, check the pressure fluctuation of the air pressure chamber. If the air pressure is unstable, there are still cracks on the surface of the mud film that cannot be observed by the naked eye. In this case, spray the face mud film with high-viscosity bentonite slurry all over until the pressure fluctuation of the air pressure chamber stabilizes.

[0045] (4) During the opening operation, observe the mud film on the tunnel face and the pressure fluctuations in the air pressure chamber. If cracks and / or pressure instability occur, spray high-viscosity bentonite again to achieve dynamic maintenance of the mud film on the tunnel face.

[0046] (5) After the tunnel face mud film is sprayed with high-viscosity bentonite, if no cracks and / or pressure instability occur, no additional treatment of the mud film is required.

[0047] The present invention adopts high-viscosity bentonite prepared by mixing grouting agent, bentonite and water in proportion as mud film maintenance mud, which has the characteristics of high viscosity, light weight, easy expansion, and easy to form a uniform spray; a high-pressure spray gun is used to fill cracks on the mud film of the face and keep the face moist, which can effectively ensure the air tightness and stability of the mud film. The operation is simple and convenient. The high-pressure spray gun device has a large spraying area, and can perform rapid dynamic maintenance on the mud film of a large diameter face. At the same time, there is no need to repeatedly pressurize the air pressure cabin, thereby reducing the health risks of construction personnel.

[0048] For example, in a certain section of the Jinan Yellow River Tunnel Project, cracks appeared on the mud film on the face and the surface was dry. By adopting the method described in Example 1 of the present invention, the maintenance period can be controlled within 2 hours. The current conventional mud film repair method (repeated pressurization and decompression, and the cabin personnel using a brush to apply the mud film) usually takes 1-2 days to repair, which greatly improves the construction efficiency.

[0049] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and such modifications or substitutions shall be within the scope of the present invention. Any person of ordinary skill in the art may easily conceive of changes or substitutions within the technical scope disclosed by the present invention, and such changes or substitutions shall be within the scope of protection of the present invention.

Claims

1. A method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield, characterized in that: After the cabin is opened under pressure, high-viscosity bentonite is sprayed on the cracks of the mud film on the tunnel face with a high-pressure spray gun, so that the high-viscosity bentonite penetrates into the cracks to fill and seal the cracks. The number of spraying times is at least once; High viscosity bentonite is prepared by grouting agent, montmorillonite and water in a weight ratio of 1:15-20:35-40. The density of high viscosity bentonite is 0.2-0.4g / cm2 less than that of hatch mud. 3 The viscosity of high viscosity bentonite is 40 to 60s.

2. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to claim 1 is characterized in that: Before opening the cabin under pressure, the cabin entry pressure is determined through theoretical calculations and pressure maintenance and pressure reduction tests.

3. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to claim 1 is characterized in that: The injection flow rate is adjusted according to the size and position of the mud film cracks on the tunnel face, with the standard being that the high-viscosity bentonite completely fills the cracks.

4. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to claim 1 is characterized in that: The high viscosity bentonite is sprayed in the form of a spray.

5. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to claim 1 is characterized in that: When opening the cabin, observe the mud film on the face and the pressure fluctuations in the pressure cabin. If cracks or pressure fluctuations appear, spray high-viscosity bentonite again until no cracks are observed or the pressure stabilizes.

6. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to claim 1 is characterized in that: After the crack spraying is completed, if the air pressure in the pressure chamber is unstable, high-viscosity bentonite should be fully sprayed on the mud film on the face until the pressure in the pressure chamber is stable.

7. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to claim 1 is characterized in that: The high-pressure spray gun is handheld and uses pneumatic pressure control. The air pressure control range is: 11-12bar.

8. The method for maintaining the mud film on the tunnel face during the pressure opening operation of a large-diameter slurry shield according to any one of claims 1 to 7, characterized in that: The specific steps include: (1) Before opening the tank under pressure, confirm the required tank entry pressure based on calculation and test; (2) Mix the grouting agent for hatch opening, montmorillonite and water to prepare high-viscosity bentonite, and place the prepared high-viscosity bentonite in a high-pressure spray gun; (3) After entering the cabin, the personnel shall observe the surface condition of the mud film on the tunnel face, determine the size and position of the mud film cracks, adjust the corresponding operating parameters, and use a high-pressure spray gun to spray high-viscosity bentonite to fill the cracks. The standard is that the high-viscosity bentonite completely fills the cracks; (4) During the opening operation, observe the surface condition of the tunnel face. If new cracks appear, repeat the injection of high-viscosity bentonite to dynamically maintain the mud film on the tunnel face; (5) After the blasting operation is completed, if there are no cracks on the mud film on the tunnel face and / or no pressure fluctuations in the air pressure chamber, no other operations are required on the mud film on the tunnel face; If cracks appear on the tunnel face mud film and / or the pressure in the pressure chamber fluctuates, high-viscosity bentonite shall be fully sprayed on the tunnel face mud film.