Air cushion type mud balance shield tunnel face mud film air tightness detection method

Abstract

The application discloses a kind of air cushion type mud balance shield face mud film air tightness detection method, comprising: calculating and determining the incision pressure value of shield machine;Air cushion bin liquid level is gradually raised, air cushion bin air pressure is adjusted, and the pressure in air cushion bin is close to incision pressure value;Slurry is gradually discharged to reduce the liquid level of air cushion bin and excavation bin, air cushion system is used for air supplement and pressure maintenance test in process, slurry discharge speed and air supplement amount of pressure maintenance system are balanced, and the pressure in slurry bin and air cushion bin is always maintained as incision pressure value of shield machine;After slurry is discharged from air cushion bin, maintain air pressure working state for a period of time, whether incision surface is stable is judged by observing the change of air pressure, the situation of residual earth before and after pressure maintenance test and whether surface / river surface is stable, to determine whether it has the condition of entering bin under pressure.

Description

Technical Field

[0001] The invention relates to the technical field of slurry shield construction, and in particular to a method for detecting air tightness of mud film on a tunnel face of an air cushion type slurry shield. Background Art

[0002] When the shield machine is excavating in composite strata, due to problems such as cutter head tool wear, circulation blockage, and accumulation of mud and water bins, it is necessary to enter the bin under pressure to inspect and replace the tools and clear the mud and water bins.

[0003] Cooperate Figure 1 As shown, the air cushion silo of an air-cushion slurry shield is generally in the neutral position (circular cross-section, positive at the top, negative at the bottom, and zero position in the middle). Mud silo 1 is full of slurry, and is connected by a slurry door 3 at the bottom. The pressure in silo 1 is controlled by adjusting the pressure-maintaining system. The pressure from the air pressure above silo 1 stabilizes the slurry at the neutral position (zero position), ensuring that silo 1 is filled with slurry. Therefore, when the liquid level in air cushion silo 2 is at zero, the pressure in air cushion silo 2 is greater than the pressure in the silo (shield radius * 0.01). The larger the shield diameter, the greater the pressure differential.

[0004] There is a connecting ball valve 7 between the mud and water bin 1 and the air cushion bin 2 in the shield body, which is opened to connect the mud and water bin 1 and the air cushion bin 2.

[0005] The conventional mud film air tightness test method involves directly opening the connecting valve after the pressure in the mud and water silos stabilizes. Once the top is connected, air enters the mud and water silo 1 based on the connecting valve principle, and the mud level is balanced between the two silos through the bottom mud gate 3. During this process, the pressure in the air cushion silo 2 is relatively high, and this quickly enters the mud and water silo 1, increasing the pressure in the air cushion silo 2 and disturbing the tunnel face mud film. The pressure maintenance system must be adjusted to control the pressure during this process. However, rapid connection also generates large pressure fluctuations, which are detrimental to the stability of the tunnel face mud film. Once the tunnel face mud film is established, a more stable pressure is more beneficial to its protection. Summary of the Invention

[0006] In order to solve the shortcomings of the existing technology, the present invention provides an air cushion type slurry shield tunnel face mud film air tightness detection method, which is beneficial to deal with the problems of difficult shield opening, difficult tool changing and high construction risk under harsh geological conditions under high water pressure environment.

[0007] The purpose of the present invention is achieved through the following technical solutions:

[0008] According to the present invention, a method for detecting the air tightness of the mud film on the tunnel face of an air cushion type slurry shield comprises the following steps:

[0009] The shield machine stops, mud film forms, and the shield machine's cut pressure value is calculated and determined;

[0010] Gradually increase the liquid level of the air cushion chamber and adjust the air pressure of the air cushion chamber until the pressure inside the air cushion chamber is close to the incision pressure value;

[0011] Open the connecting valves of the mud and water tank and the air cushion tank, gradually drain the slurry to lower the liquid level of the air cushion tank and the mud and water tank. During the slurry discharge process, use the pressure maintaining system to perform air supply and pressure maintenance tests. The slurry discharge speed is balanced with the air supply volume of the pressure maintaining system, and the pressure in the mud and water tank and the air cushion tank is always maintained at the shield machine's cut pressure value.

[0012] After the air cushion bin is discharged, the air pressure working state is maintained for a period of time. By observing the changes in air pressure, the conditions of the slag before and after the pressure holding test, and the stability of the ground / river surface, it is judged whether the incision surface is stable, thereby determining whether the conditions for entering the bin under pressure are met.

[0013] Furthermore, in the process of gradually increasing the liquid level in the air cushion tank, the pressure is reduced by 0.1 bar for every 1 meter increase in the liquid level until the air cushion tank liquid level reaches the upper limit. The air cushion tank pressure is 0.02 bar to 0.03 bar higher than the mud and water tank pressure.

[0014] Furthermore, in the process of gradually draining the slurry to lower the liquid level of the air cushion bin and the mud and water bin, the liquid level is lowered to the bin heights of 2 / 3, 1 / 2, and 1 / 3 respectively.

[0015] Furthermore, by recording the air supply volume of the pressure maintaining system, if the loading frequency of the pressure maintaining system is less than 10 times within 5 hours and the pressure maintaining effect of the mud film on the support surface is good, it is judged that the conditions for pressurized entry into the warehouse are met.

[0016] Furthermore, the pressure maintaining system includes an air compressor, through which the air cushion bin and the mud and water bin are replenished with air.

[0017] Furthermore, the pressure holding test includes the following steps:

[0018] Set the holding pressure to the shield machine's cut pressure value;

[0019] While the air cushion bin and mud-water bin are discharging slurry, the air compressor replenishes air to replace the mud with gas;

[0020] Record pressure holding test data;

[0021] Inject mud into the air cushion tank and mud-water tank to maintain pressure, and record the working status of the air compressor;

[0022] Run circulation;

[0023] Check the slag discharge situation.

[0024] The positive and progressive effect of this invention lies in: The air cushion chamber pressure is higher than the mud and water chamber pressure. By pre-raising the air cushion chamber liquid level, lowering the air cushion chamber pressure, and reducing the pressure differential between the air cushion chamber and the mud chamber, the air cushion chamber pressure is brought close to the mud and water chamber pressure. The connecting valve is then opened to connect the mud and water chamber with the air cushion chamber. Slurry is slowly discharged, with the discharge speed matching the air supply volume between the two chambers. Ultimately, the pressure differential micro-perturbs the mud film on the tunnel face, resulting in a more stable mud film on the tunnel face, longer air-holding tests, and a safer pressurized working environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0026] Figure 1 Schematic diagram of the internal structure of the air cushion slurry shield.

[0027] Figures 2-4 A schematic diagram of the process of a method for detecting air tightness of mud film on the tunnel face of an air cushion slurry shield provided in an embodiment of the present invention.

[0028] Figure 5 A flow chart of a pressure-maintaining test for a method for detecting air tightness of mud film on the tunnel face of an air-cushion slurry shield provided in an embodiment of the present invention.

[0029] The corresponding relationship of the labels in the figure is as follows:

[0030] 1-mud and water bin; 2-air cushion bin; 3-mud door; 4-crusher; 5-slurry discharge pipe; 6-knife gate valve; 7-hydraulic ball valve; 8-mud membrane; 9-knife disc; 10-partition; 11-bentonite. DETAILED DESCRIPTION

[0031] The following is a further description of specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0032] An embodiment of the present invention provides a method for detecting the air tightness of the mud film on the tunnel face of an air-cushion slurry shield. The method mainly solves the problem of controlling the pressure of the air cushion chamber during the air-tightness (pressure-maintaining) test to make it infinitely close to the pressure of the mud-water chamber, thereby reducing the disturbance to the mud film on the tunnel face, enabling it to have a good air-tightness effect for a longer period of time, and providing a long-term pressurized chamber operation environment.

[0033] When the shield machine has to enter the chamber under pressure to inspect and replace the cutters and clear the mud and water bunker due to problems such as cutter head wear, circulation blockage, and mud and water bunker accumulation, bentonite, shield slurrying agent and other materials are injected into the mud and water bunker to establish a mud film on the tunnel face. The mud and water bunker pressure is slightly higher than the stratum water and soil pressure of 0.4 bar. When the mud and water bunker pressure shows a slight upward trend or the pressure drops within 0.05 bar within 5 hours, a closed air test is carried out.

[0034] Step 1: Stop the shield machine, form a mud film, and calculate and determine the shield machine's incision pressure value

[0035] 1. After the shield machine stops, the mud film is well formed. Calculate and determine the shield machine's incision pressure value. Take the case where the liquid level drops to 1 / 2 of the height of the mud tank 1 as an example. Figure 2 shown.

[0036] 2. According to the formula: P empty = P cut + P △ h

[0037] The liquid pressure per meter in the mud and water tank 1 is 0.1 bar / m, and the shield excavation diameter is 12m. Therefore, the air pressure in the shield machine air cushion tank 2 is: P air = p + 0.6 = (p + 0.6) bar.

[0038] Step 2: Slowly increase the air cushion tank liquid level to the upper limit, and slowly reduce the pressure of the pressure maintaining system during the process. When the mud and water tank liquid level reaches the upper limit, it is slightly higher than the mud and water tank pressure by 0.03 bar;

[0039] Furthermore, the air cushion tank liquid level is slowly increased. During this process, the pressure of the pressure maintaining system is reduced by 0.1 bar for every meter increase until the air cushion tank liquid level reaches the upper limit. At this time, the air cushion tank liquid level is slightly higher than the mud and water tank pressure by 0.02 to 0.03 bar.

[0040] Specifically, slowly increase the liquid level of the air cushion chamber 2. After each 1m increase in the liquid level, adjust (lower) the air pressure of the air cushion chamber 2, observe the liquid level for 30 minutes, and after the liquid level and pressure are stable, raise the liquid level by another 1m, and adjust (lower) the pressure value of the bubble chamber again. Until the pressure in the bubble chamber is slightly greater than the incision pressure, at this time the bentonite liquid level of the air cushion chamber 2 is almost equal to the liquid level of the mud and water chamber 1, that is, P air ≈ P cut = (p+0.6) bar. (The liquid level height cannot exceed the height of the air inlet of the pressure maintaining system and the height of the manhole. The pressure maintaining system can adopt the SAMSON system, which is a prior art. The Chinese patent CN 113202486A discloses the auxiliary pressure maintaining propulsion method of the water-rich rock formation SAMSON system). Figure 3 shown.

[0041] Step 3: Open the connecting valve between the mud and water tank and the air cushion tank to balance the pressure of the air cushion tank and the mud and water tank;

[0042] Step 4: Slowly lower the liquid level in the two tanks to 2 / 3, observe the liquid level, pressure, and record the air pressure loading frequency for 30 minutes. If the loading frequency is less than 10 times, drain the liquid level to 1 / 2 and 1 / 3 again;

[0043] Furthermore, the slurry pump slowly discharges the slurry, and the slurry discharge speed is balanced with the air supply volume of the pressure maintaining system, and the pressure of the two chambers is always maintained at the pressure required when the chamber is opened; slowly reduce the liquid level of the two chambers to 2 / 3, observe the liquid level, pressure, and record the air pressure loading frequency for 30 minutes. If the loading frequency is less than 10 times, then discharge the liquid level to 1 / 2 and 1 / 3 again. Figure 4 As shown;

[0044] Specifically, the slurry discharge pipe at the bottom of the shield machine is opened, and the liquid level is first lowered to 2 / 3 of the height of the mud and water tank 1. The pressure changes are observed. If there is no significant change within 2 hours, the liquid level is further lowered to 1 / 2 below the height of the mud and water tank 1. The pressure changes are observed. If there is no significant change within 2 hours, personnel can open the tank to pressurize it. The pressure maintaining pressure of the SAMSON system is ultimately set to the shield machine cutout pressure value, and the SAMSON system automatically adjusts it to maintain stable pressure in the air cushion tank 2 and mud and water tank 1.

[0045] Step 5: Record the air supply volume of the pressure-maintaining system. The air compressor loading frequency is less than 10 times within 5 hours. The mud film on the tunnel face has a good air-tightness effect and is ready for pressurized entry.

[0046] Specifically, after the air cushion bin 2 is discharged, the air pressure working state shall be maintained for a working time of not less than 5 hours. If necessary, the test time shall be delayed. By observing the changes in air pressure, the conditions of the slag before and after the pressure holding test, and the stability of the ground / river surface, the stability of the incision surface can be judged, thereby determining whether the conditions for entering the bin are met. The specific process is as follows: Figure 5 As shown, the pressure maintaining system includes an air compressor, through which the air cushion tank and the mud and water tank are replenished with air.

[0047] The specific process of the pressure holding test is as follows:

[0048] S1: Air pressure setting

[0049] Set the holding pressure to the shield machine's cut pressure value;

[0050] S2: Gas displacement mud

[0051] While the air cushion bin and mud-water bin are discharging slurry, the air compressor replenishes air to replace the mud with gas;

[0052] S3: Air pressure test record

[0053] Record pressure holding test data;

[0054] S4: Inject slurry to maintain pressure

[0055] Inject mud into the air cushion tank and mud-water tank to maintain pressure, and record the working status of the air compressor;

[0056] S5: running circulation;

[0057] S6: Check the slag discharge situation.

[0058] During the pressure maintenance process, record the time of each air compressor loading start-up, and then calculate the interval between the two air filling starts. The change in the time interval between each air compressor filling can be used to determine whether there is gas leakage in the air cushion chamber.

[0059] When the mud door is open, slowly increase the air cushion layer level to the upper limit. At this time, the air cushion layer pressure is close to the mud and water tank pressure. Open the connecting valve to connect the mud and water tank with the air cushion tank, and then discharge the slurry through the slurry pump. The slurry discharge speed must match the air supply volume of the pressure maintaining system. When the liquid level drops to 2 / 3 of the tank, observe the change in the mud and water tank level and the air compressor loading frequency for 30 minutes. If there is no change in the liquid level and the air compressor loading frequency is less than 10 times, continue to lower the liquid level to 1 / 2. Continue to observe for 30 minutes. If there is no change in the liquid level and the air compressor loading frequency is less than 10 times, continue to lower the liquid level to 1 / 3. Continue to observe for 5 hours. If there is no change in the liquid level and the air compressor loading frequency is less than 10 times, the air tightness is good and the conditions for pressure entry are met. If the conditions are not met, it is necessary to re-establish the mud film for air sealing (pressure maintaining) test.

[0060] The present invention provides a method for testing the air tightness of the mud film on the tunnel face of an air-cushion slurry shield. The air cushion chamber pressure is higher than the mud and water chamber pressure, with a pressure differential of 0.1 bar per meter. This method pre-increases the air cushion chamber pressure level, lowers the air cushion chamber pressure, and reduces the pressure differential between the air cushion chamber and the mud chamber, bringing the air cushion chamber pressure close to that of the mud and water chamber. The connecting valve is then opened to connect the mud and water chamber with the air cushion chamber. Slurry is slowly discharged, with the discharge speed matching the air supply volume between the two chambers. Ultimately, pressure differential micro-perturbation of the tunnel face mud film is achieved, resulting in a more stable tunnel face mud film, a longer air-holding test, and a safer pressurized working environment.

[0061] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations to these embodiments may be made without departing from the principles and spirit of the present invention, and these changes and modifications still fall within the scope of protection of the present invention.

Claims

1. A method for detecting the air tightness of mud film on the tunnel face of an air cushion slurry shield, characterized in that: Including steps: The shield machine stops, mud film forms, and the shield machine's cut pressure value is calculated and determined; Gradually increase the liquid level of the air cushion chamber and adjust the air pressure of the air cushion chamber until the pressure inside the air cushion chamber is close to the incision pressure value; Open the connecting valves of the mud and water tank and the air cushion tank, gradually drain the slurry to lower the liquid level of the air cushion tank and the mud and water tank. During the slurry discharge process, use the pressure maintaining system to perform air supply and pressure maintenance tests. The slurry discharge speed is balanced with the air supply volume of the pressure maintaining system, and the pressure in the mud and water tank and the air cushion tank is always maintained at the shield machine's cut pressure value. After the air cushion bin is discharged, the air pressure working state is maintained for a period of time. By observing the changes in air pressure, the conditions of the slag before and after the pressure holding test, and the stability of the ground / river surface, it is judged whether the incision surface is stable, thereby determining whether the conditions for entering the bin under pressure are met.

2. The method for detecting air tightness of mud film on the tunnel face of an air cushion slurry shield according to claim 1 is characterized in that: In the process of gradually increasing the liquid level in the air cushion tank, the pressure is reduced by 0.1 bar for every 1 meter increase in the liquid level until the air cushion tank liquid level reaches the upper limit. The air cushion tank pressure is 0.02 bar to 0.03 bar higher than the mud and water tank pressure.

3. The method for detecting air tightness of mud film on the tunnel face of an air cushion slurry shield according to claim 1, characterized in that: In the process of gradually discharging the slurry to lower the liquid level of the air cushion bin and the mud water bin, the liquid level is reduced to the bin heights of 2 / 3, 1 / 2, and 1 / 3 respectively.

4. The method for detecting air tightness of mud film on the tunnel face of an air cushion slurry shield according to claim 1, characterized in that: By recording the air supply volume of the pressure-maintaining system, if the loading frequency of the pressure-maintaining system is less than 10 times within 5 hours and the pressure-maintaining effect of the mud film on the support surface is good, it is judged that the conditions for pressurized entry are met.

5. The method for detecting air tightness of mud film on the tunnel face of an air cushion slurry shield according to claim 1, characterized in that: The pressure maintaining system includes an air compressor, through which air is replenished in the air cushion bin and the mud and water bin.

6. The method for detecting air tightness of mud film on the tunnel face of an air cushion slurry shield according to claim 5, characterized in that: The pressure holding test includes the following steps: Set the holding pressure to the shield machine's cut pressure value; While the air cushion bin and mud-water bin are discharging slurry, the air compressor replenishes air to replace the mud with gas; Record pressure holding test data; Inject mud into the air cushion tank and mud water tank to maintain pressure, record the working status of the air compressor; operate the circulation; Check the slag discharge situation.

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