Tunnel water and sand gushing working condition liquid nitrogen freezing plugging test device and test method

Abstract

The application discloses a liquid nitrogen freezing plugging test device and test method under the condition of tunnel water and sand inrush, and the device comprises a freezing pipe, a drilling sharp head, a liquid nitrogen pipeline, a liquid nitrogen tank and a hand wheel, wherein the drilling sharp head is conical; the end of the freezing pipe close to the drilling sharp head forms a liquid nitrogen outlet and / or a pressure relief exhaust passage in the pipe cavity, the liquid nitrogen entering the freezing pipe is discharged from the liquid nitrogen outlet to the water and sand inrush area and / or is discharged from the pressure relief exhaust passage, and the flowing liquid nitrogen directly or indirectly freezes the water and sand inrush area to form plugging. The application directly inserts the liquid nitrogen to directly and / or indirectly implement rapid freezing under the condition of different pressures and different soil layers with water and sand inrush danger, thereby simply, rapidly and effectively plugging the leakage passage, avoiding the disturbance of the drilling to the surrounding soil, and reducing the risk; on the other hand, the liquid nitrogen can be rotatably inserted, the operation is convenient, and the application also provides a technical basis for the practical application of the liquid nitrogen rapid freezing in engineering.

Description

Technical Field

[0001] This invention belongs to the field of shield tunnel construction technology, specifically relating to a liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions, and also relating to a liquid nitrogen freezing and sealing test method simulating tunnel water and sand inrush conditions. Background Technology

[0002] In recent years, the presence of abundant groundwater during underwater tunnel construction has greatly increased the risk of water and sand inrush at the tunnel excavation face. To address this challenge, the application of liquid nitrogen freezing for sealing in tunnel emergency situations has become increasingly widespread, including in practical projects such as shield tunneling entry and exit, shield tunneling chamber opening, and secondary water sealing of tunnel working shafts. Liquid nitrogen freezing, as a novel freezing method, features a simple system, rapid freezing speed, no pollution, and minimal frost heave and thawing settlement. Its principle utilizes the direct vaporization of liquid nitrogen as a cold source, exchanging heat with the surrounding medium, causing water to freeze rapidly. Currently, engineering applications require drilling holes in the surrounding soil and rock layers to lay freezing pipes, for example: Chinese Patent Application No.: 202310124676.0; Invention Title: A Mining Liquid Nitrogen Rapid Freezing Water Sealing Emergency Device and Implementation Method. This invention is a mining liquid nitrogen rapid sealing device and practical construction method, which combines liquid nitrogen freezing and grouting reinforcement to seal water-hazardous areas in coal mines. In short, current liquid nitrogen emergency sealing methods require drilling, installation of frozen pipes, and freezing to seal leaks. However, in certain special projects, such as those where the frozen walls are poorly connected and leak channels appear, drilling can cause the surrounding frozen walls to melt rapidly, causing the seepage channels to expand continuously, increasing the flow rate and velocity of water and sand, and drastically increasing the risk. Therefore, in the face of sudden high water pressure leaks, it is necessary to seal the leaks in the fastest and most direct way to reduce construction risks. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a novel test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions.

[0004] Meanwhile, the present invention also relates to a liquid nitrogen freezing and sealing test method under simulated tunnel water and sand inrush conditions.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions includes a freezing tube forming an internal cavity, a drilling tip sealed at one end of the freezing tube with its tip facing outward, a liquid nitrogen pipeline and a liquid nitrogen tank connected to the other end of the freezing tube, and a handwheel coaxially installed on the outer periphery of the freezing tube. The drilling tip is conical, with its center line coinciding with the center line of the freezing tube, and the outer diameter of the cone base is larger than the outer diameter of the freezing tube. A liquid nitrogen outlet is formed at the end of the freezing tube near the drilling tip, and a pressure relief and exhaust channel is formed inside the cavity. Liquid nitrogen entering the freezing tube is discharged from the liquid nitrogen outlet to the water and sand inrush area and discharged from the pressure relief and exhaust channel. The flowing liquid nitrogen directly or indirectly freezes the water and sand inrush area to form a seal.

[0007] According to a specific embodiment and preferred aspect of the invention, a plurality of liquid nitrogen outlets are distributed at the end of the cryotube near the drilling tip, wherein the plurality of liquid nitrogen outlets are divided into a plurality of liquid nitrogen outlet rows evenly distributed around the circumference of the cryotube, and each liquid nitrogen outlet row includes a plurality of liquid nitrogen outlets spaced apart along the length of the cryotube. This facilitates rapid and relatively uniform leakage of liquid nitrogen to achieve optimal stepwise freezing effect, while employing a direct contact freezing method.

[0008] According to another specific embodiment and preferred aspect of the present invention, the liquid nitrogen pipeline includes a liquid nitrogen transfer pipe inserted into a tube sheet at the other end of the cryogenic pipe, with its internal port near the liquid nitrogen outlet; a flexible hose connecting the liquid nitrogen transfer pipe to the liquid nitrogen tank; wherein the portion between the liquid nitrogen transfer pipe and the cryogenic pipe forms a liquid nitrogen chamber; and the cryogenic pipe is also provided with a vent branch communicating with the liquid nitrogen chamber, a pressure relief valve disposed on the vent branch, and an exhaust pipe, wherein the liquid nitrogen chamber, the vent branch, and the exhaust pipe are interconnected to form a pressure relief and exhaust channel. In short, the cryogenic pipe is a perforated pipe type. After liquid nitrogen enters the cryogenic pipe, it is transported through a seamless stainless steel pipe to the liquid nitrogen outlet at the front end. The gas then enters the soil layer to achieve heat exchange. Due to the formation pressure, most of the gas is discharged through the formation gaps, while a small portion remains in the cryogenic pipe and is discharged to the outside through the pressure relief and exhaust channel. Therefore, by combining direct contact freezing with venting, and with the insertion of a liquid nitrogen transfer pipe, not only can liquid nitrogen be accurately delivered to the liquid nitrogen outlet, but energy consumption of liquid nitrogen can also be reduced, and the designated area can be frozen with the best effect.

[0009] In some specific embodiments, the cross-sectional area formed by the liquid nitrogen transfer pipe in the cryotube is larger than that formed by the liquid nitrogen chamber. Generally, the difference in inner diameter between the cryotube and the liquid nitrogen transfer pipe is within 25 mm, allowing sufficient space for nitrogen retention. Simultaneously, the inner diameter of the drain branch is larger than that of the liquid nitrogen transfer pipe, while the inner diameter of the drain branch is smaller than that of the cryotube. This facilitates the more effective discharge of gases that have undergone heat exchange, improving the liquid nitrogen freezing efficiency.

[0010] Furthermore, one or more layers of plastic film are wrapped around the outer periphery of the sections corresponding to the multiple liquid nitrogen outlets for sealing. Before drilling, the liquid nitrogen outlets of the perforated pipe need to be sealed with plastic film, with approximately 2-6 turns (generally 4 turns). At the same time, the film is wrapped and fixed to the freezing pipe at both ends with tape. The advantage of this setup is that after the freezing pipe is inserted into the soil layer or other filling layer where water and sand are flowing, the inside of the freezing pipe is in a dry state, preventing the inside of the freezing pipe from freezing after nitrogen supply, which would affect the freezing efficiency and effect of the water and sand inflow area.

[0011] According to another specific embodiment and preferred aspect of the invention, a first tube and a second tube, respectively fixed to the inner wall of the freezing tube, are further provided inside the freezing tube. The outer ends of the first tube and the second tube extend out of the freezing tube, and the length of the second tube extending into the freezing tube is less than the length of the first tube extending into the freezing tube. A liquid nitrogen pipeline is connected to the outer end of the first tube, and the outer end of the second tube is connected to an exhaust pipe. Liquid nitrogen entering the freezing tube indirectly contacts the water and sand inrush area and is then discharged from the second tube and the exhaust pipe to form a circulation. Therefore, freezing of the water and sand inrush area can also be implemented in the circulation mode.

[0012] In some specific embodiments, the inner end of the first tube is positioned near the drilling tip; the inner end of the second tube is positioned near the middle of the cryotube. This arrangement not only enables rapid circulation of liquid nitrogen but also delivers optimal freezing performance. Furthermore, the inner diameter of the first tube is larger than that of the second tube, effectively increasing the indirect contact time between the liquid nitrogen and the cryotube, thus improving freezing efficiency.

[0013] Furthermore, the cone angle formed by the drilling tip is acute and solid internally; the outer diameter of the cone bottom is D1, and the outer diameter of the freezing pipe is D2, with D1-D2 ≥ 5mm. The drilling tip design facilitates drilling into the soil layer, and its tail diameter is approximately 5mm larger than the freezing pipe diameter, preventing damage to the plastic film during drilling. Simultaneously, the liquid nitrogen freezing rapid sealing device also includes a limiting baffle concentrically mounted on the freezing pipe, a ball valve communicating with the liquid nitrogen chamber inside the freezing pipe, and a pressure gauge. The limiting baffle, handwheel, ball valve, and pressure gauge are spaced apart from the middle of the freezing pipe to the other end, with the baffle position representing the drilling limit position to conform to the surface of gushing water and sand, reducing water and sand flow and providing a certain sealing effect. The rotating wheel facilitates drilling into the soil layer; the ball valve is the main control hub for liquid nitrogen entering the freezing pipe, using a low-temperature, high-pressure resistant stainless steel ball valve that is initially closed; the pressure gauge is used to read the pressure inside the freezing pipe and promptly determine its pressure status.

[0014] Another technical solution of the present invention is: a liquid nitrogen freezing and sealing test method for simulating tunnel water and sand inrush conditions, which adopts the above-mentioned liquid nitrogen freezing rapid sealing device, and the liquid nitrogen freezing rapid sealing device further includes a limiting baffle concentrically arranged on the freezing tube, a ball valve and a pressure gauge communicating with the liquid nitrogen chamber inside the freezing tube, the limiting baffle, handwheel, ball valve and pressure gauge being distributed at intervals from the middle to the other end of the freezing tube, the simulated tunnel water and sand inrush conditions also having a test chamber simulating different pressures and different filling material layers, a test ball valve and a test temperature measuring sleeve located on the test chamber, and includes the following steps:

[0015] S1. Preparations before sealing:

[0016] (1) Wrap the outer periphery of the cryogenic tube where the liquid nitrogen outlet is located with plastic film to seal it tightly. The number of wrapping turns is 2 to 6. Use tape to wrap and fix the plastic film to the cryogenic tube.

[0017] (2) Adjust the ball valve and the pressure relief and exhaust passage to the closed state;

[0018] (3) Connect the liquid nitrogen pipeline to the cryogenic pipeline and tighten it by threading the bolts on the flange;

[0019] (4) Insert the temperature measuring tube into the test temperature measuring sleeve, and at the same time prepare an ice-water mixture as the temperature reference temperature. Then connect the temperature measuring series circuit and test it to check whether the reading is normal.

[0020] (5) Fill the lower space of the test chamber with the material to be tested, and form a water pressure layer with adjustable pressure above the material to be tested, so as to simulate the actual water and sand inrush conditions in the tunnel.

[0021] S2. Blocking Phase:

[0022] (1) Fully open the test ball valve on the test chamber that causes water and sand to gush out;

[0023] (2) After the water and sand flow out, use a freezing pipe that matches the diameter of the ball valve to be tested, operate the handwheel and rotate from the drilling tip to drill into the water and sand leakage area, where the drilling depth is 25~30cm.

[0024] (3) After insertion, secure the freezer tube with wire, and then open the ball valve on the freezer tube;

[0025] (4) The liquid nitrogen outlet is then opened, and the liquid nitrogen outlet pressure is adjusted to 1.0±0.1MPa. Then the pressurized supply is started. The liquid nitrogen entering the freezing tube is discharged from the liquid nitrogen outlet to the water and sand inrush area and / or discharged from the opened pressure relief and exhaust channel. The flowing liquid nitrogen directly or indirectly freezes and seals the water and sand inrush area.

[0026] (5) After the liquid nitrogen supply begins, synchronize timing and temperature measurement are performed;

[0027] (6) Observe the state of water and sand inflow during the freezing process;

[0028] (7) When the pressure count value on the test chamber is greater than the set value, the pressure relief safety valve on the test chamber will automatically open to release pressure, simulating freezing under the required water pressure;

[0029] (8) After the water flow has completely stopped, close the ball valve on the refrigeration pipe to complete the sealing.

[0030] Therefore, this invention utilizes liquid nitrogen to directly or indirectly and rapidly freeze and seal leaks, further verifying the feasibility of directly freezing leaks with liquid nitrogen under different pressures and geological conditions without drilling. Furthermore, by changing the outer diameter of the freezing pipe and conducting configuration experiments on the channel size, a numerical model relationship between the difference in diameter between the channel and the freezing pipe and the sealing time can be obtained, providing feasibility for actual construction.

[0031] Due to the implementation of the above technical solutions, the present invention has the following advantages compared with the prior art:

[0032] Existing liquid nitrogen freezing rapid sealing devices require drilling, installation of freezing pipes, and freezing to seal leaks. However, in certain special projects, such as those with poorly sealed frozen walls leading to seepage channels, drilling can cause rapid melting of the surrounding frozen walls, resulting in the expansion of the seepage channel, increased flow rate and velocity of water and sand, and a sharp increase in risk. This invention cleverly solves these shortcomings of existing structures through a comprehensive structural design of the liquid nitrogen freezing rapid sealing device. Using this device, based on direct or indirect liquid nitrogen freezing of the seepage point via freezing pipe insertion, it fully utilizes the energy of liquid nitrogen vaporization to achieve rapid freezing of liquid water to solid in areas with water and sand inflow. Therefore, this invention addresses the challenges of water and sand inflow under different pressures and soil layers by directly inserting liquid nitrogen for rapid freezing, providing a simple, fast, and effective way to seal seepage channels while avoiding disturbance to the surrounding soil and reducing risk. Furthermore, the device can be rotated for easy operation and provides a technical foundation for the practical application of liquid nitrogen rapid freezing in engineering projects. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in Example 1;

[0034] Figure 2 This is a schematic diagram of the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in Example 2 (liquid nitrogen pipeline and liquid nitrogen tank omitted).

[0035] Figure 3 This is a schematic diagram of the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in Example 3 (liquid nitrogen pipeline and liquid nitrogen tank omitted).

[0036] Figure 4 This is a schematic diagram of the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in Example 4 (liquid nitrogen pipeline and liquid nitrogen tank omitted).

[0037] Figure 5 This is a schematic diagram of the structure for rapid sealing with liquid nitrogen under simulated tunnel water and sand inrush conditions in Example 5;

[0038] The components are as follows: 1. Freezing pipe; 10. Liquid nitrogen outlet; 2. Drilling tip; 3. Liquid nitrogen pipeline; 30. Liquid nitrogen transfer pipe; 31. Hose; 4. Liquid nitrogen tank; 5. Handwheel; 6. Limiting baffle; 7. Ball valve; 8. Pressure gauge; x1. Drainage branch; x2. Pressure relief valve; x3. Exhaust pipe; a1. First pipe body; a2. Second pipe body; A. Test chamber; B. Test ball valve; C. Test temperature measuring sleeve; D. Soil layer; E. Water pressure layer; F. Manhole; G. Pressure relief safety valve; H. Pressure gauge; J. Water supply pipeline. Detailed Implementation

[0039] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the application will be described in detail below with reference to the accompanying drawings and specific embodiments. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0040] In the description of this application, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0041] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0042] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0043] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0044] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation. Example 1

[0045] like Figure 1 As shown, the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in this embodiment includes a freezing tube 1 forming an internal cavity, a drilling tip 2 encapsulated at the left end of the freezing tube 1 with its tip facing outward, a liquid nitrogen pipeline 3 and a liquid nitrogen tank 4 connected to the right end of the freezing tube 1, a handwheel 5 coaxially installed on the outer periphery of the freezing tube 1, a limiting baffle 6 coaxially set on the freezing tube 1, a ball valve 7 and a pressure gauge 8 connected to the inside of the freezing tube 1, wherein the limiting baffle 6, handwheel 5, ball valve 7 and pressure gauge 8 are distributed at intervals from the middle to the right end of the freezing tube 1.

[0046] In some specific embodiments, the cryogenic tube 1 is a straight tube, and multiple liquid nitrogen outlets 10 are distributed at the end of the cryogenic tube 1 near the drilling tip 2. The multiple liquid nitrogen outlets 10 are divided into multiple liquid nitrogen outlet rows evenly distributed around the circumference of the cryogenic tube 1. Each liquid nitrogen outlet row includes multiple liquid nitrogen outlets 10 spaced apart along the length direction of the cryogenic tube 1 (forming an ellipse with the major axis direction consistent with the length direction of the cryogenic tube, resulting in good drainage effect). The drilling tip 2 is conical, with the center line of the cone coinciding with the center line of the cryogenic tube 1, and the outer diameter of the cone bottom (right end) is larger than the outer diameter of the cryogenic tube 1. Specifically, the cone angle formed by the drilling tip is an acute angle, and the interior is solid. The outer diameter of the cone bottom is D1, and the outer diameter of the cryogenic tube is D2, where D1-D2=5mm.

[0047] Furthermore, one or more layers of plastic film sealing layer are wrapped around the outer periphery of the sections corresponding to the multiple liquid nitrogen outlets 10. Before drilling, the liquid nitrogen outlets of the perforated pipe need to be sealed with plastic film, with approximately 2-6 turns (generally 4 turns). At the same time, the film is wrapped and fixed to the freezing pipe with tape at both ends. The advantage of this setting is that after the freezing pipe is inserted into the soil layer or other filling layer where water and sand are flowing, the inside of the freezing pipe is in a dry state, preventing the inside of the freezing pipe from freezing after nitrogen supply, which would affect the freezing efficiency and effect of the water and sand inflow area.

[0048] In addition, the aforementioned baffle 6 position is the drilling limit position, which can reduce the water and sand flow by fitting against the surface of the water and sand inflow, and play a certain role in sealing; the impeller 5 is to facilitate drilling into the soil layer; the ball valve 7 is the main control hub for liquid nitrogen to enter the refrigeration pipe 1, and adopts a low temperature and high pressure resistant stainless steel ball valve, which is initially kept closed; the pressure gauge 8 is used to read the pressure in the refrigeration pipe and to judge the pressure status in the refrigeration pipe in a timely manner.

[0049] Therefore, the implementation process of this embodiment is as follows:

[0050] S1. Preparations before sealing:

[0051] (1) Wrap the outer periphery of the cryogenic tube where the liquid nitrogen outlet is located with plastic film to seal it tightly. The number of wrapping turns is 2 to 6. Use tape to wrap and fix the plastic film to the cryogenic tube.

[0052] (2) Adjust the ball valve and the pressure relief and exhaust passage to the closed state;

[0053] (3) Connect the liquid nitrogen pipeline to the cryogenic pipeline and tighten it by threading the bolts on the flange;

[0054] S2. Blocking Phase:

[0055] (1) After the water and sand flow out, use a freezing pipe, operate the handwheel and rotate the drill tip to drill into the water and sand seepage area, where the drilling depth is 25~30cm.

[0056] (2) After insertion, secure the freezer tube with wire, and then open the ball valve on the freezer tube;

[0057] (3) As the internal pressure of the cryogenic tube increases, the plastic film sealing layer is gradually opened or destroyed, and liquid nitrogen flows out from the liquid nitrogen outlet. At the same time, the liquid nitrogen outlet pressure is adjusted to 1.0±0.1MPa, and then pressurized supply is applied. At this time, the liquid nitrogen entering the cryogenic tube is discharged from the liquid nitrogen outlet to the water and sand inrush area, and the flowing liquid nitrogen directly freezes the water and sand inrush area to seal it.

[0058] (4) After the water flow has completely stopped, close the valves on the liquid nitrogen pipeline and the ball valve on the refrigeration pipe in sequence to complete the sealing. Example 2

[0059] like Figure 2 As shown, the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in this embodiment has a structure that is basically the same as that in Example 1, with the following specific differences.

[0060] In this example, the liquid nitrogen pipeline 3 includes a liquid nitrogen transfer pipe 30 inserted from the tube sheet at the other end of the cryogenic tube 1 with its internal port close to the liquid nitrogen outlet 10, and a flexible hose 31 connecting the liquid nitrogen transfer pipe 30 to the liquid nitrogen tank. The portion between the liquid nitrogen transfer pipe 30 and the cryogenic tube 1 forms a liquid nitrogen chamber. The cryogenic tube 1 is also provided with a vent branch x1 connected to the liquid nitrogen chamber, a pressure relief valve x2 provided on the vent branch x1, and an exhaust pipe x3. The liquid nitrogen chamber, the vent branch x1, and the exhaust pipe x3 are connected to form a pressure relief and exhaust channel.

[0061] In some specific embodiments, the cross-sectional area formed by the liquid nitrogen transfer pipe 30 in the cryogenic tube 1 is larger than the cross-sectional area formed by the liquid nitrogen chamber. Generally, the difference in inner diameter between the cryogenic tube 1 and the liquid nitrogen transfer pipe 30 is 25 mm, leaving a certain space for nitrogen retention. At the same time, the inner diameter of the drain branch is larger than the inner diameter of the liquid nitrogen transfer pipe, and the inner diameter of the drain branch is smaller than the inner diameter of the cryogenic tube.

[0062] The venting branch x1 is located near the outer end of the cryogenic tube 1. The limiting baffle 6 and handwheel 5 are located on the outer periphery of the cryogenic tube 1. The ball valve 7 and pressure gauge 8 are located on the liquid nitrogen transmission tube 30. The venting branch x1 is located between the handwheel 5 and the ball valve 7.

[0063] Furthermore, the process for rapid sealing with liquid nitrogen freezing under conditions of water and sand inrush in tunnels is basically the same as in Example 1, except that the freezing pipe is a perforated pipe. After liquid nitrogen enters the freezing pipe, it is transported to the liquid nitrogen outlet at the front end through a seamless stainless steel pipe. The pressure relief valve x2 is in the closed state. After the pressure drops significantly, it proves that the membrane at the front has been broken. Only then can the pressure relief valve x2 be opened, and the gas enters the soil layer to achieve heat exchange. Due to the action of the formation pressure, most of the gas is discharged through the formation gaps, and a small amount of gas remains in the freezing pipe and is discharged to the outside through the pressure relief and exhaust channel. Therefore, freezing is implemented by combining direct contact freezing and exhaust. Example 3

[0064] like Figure 3 As shown, the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in this embodiment has a structure that is basically the same as that in Example 2, with the following specific differences.

[0065] In this example, the difference in inner diameter between the cryotube 1 and the liquid nitrogen transfer tube 30 is about 12 mm. At the same time, the liquid nitrogen transfer tube 30 is directly inserted into the right end of the cryotube 1, and the drain branch x1 is located on the right side of the middle part of the cryotube 1. Example 4

[0066] like Figure 4 As shown, the liquid nitrogen freezing and sealing test device under tunnel water and sand inrush conditions in this embodiment has a structure that is basically the same as that in Example 2, with the following specific differences.

[0067] In some specific embodiments, the end of the cryogenic tube 1 near the drilling tip 2 is not provided with a liquid nitrogen outlet. At the same time, a first tube body a1 and a second tube body a2 are respectively fixed to the inner wall inside the cryogenic tube 1. The right ends of the first tube body a1 and the second tube body a2 respectively extend out of the cryogenic tube 1. The length of the second tube body a2 extending into the cryogenic tube 1 is less than the length of the first tube body a1 extending into the cryogenic tube 1. The liquid nitrogen pipeline 3 is connected to the right end of the first tube body a1, and the right end of the second tube body a2 is connected to the exhaust pipe x3.

[0068] In this example, the inner end of the first tube a1 is located near the drill tip 2; the inner end of the second tube a2 is located near the middle of the freezing tube 1. At the same time, the inner diameter of the first tube a1 is larger than the inner diameter of the second tube a2.

[0069] In addition, the process of rapid sealing by liquid nitrogen freezing under the condition of water and sand inrush in the tunnel is basically the same as the embodiment. The difference is that the liquid nitrogen entering the freezing pipe 1 indirectly comes into contact with the water and sand inrush area and is discharged from the second pipe a2 and the exhaust pipe x3 to form a circulation. Example 5

[0070] like Figure 5As shown, the liquid nitrogen freezing rapid sealing device for simulating tunnel water and sand inrush conditions involved in this embodiment has a structure that is basically the same as that in Example 1, with the following differences.

[0071] In this example, it is necessary to simulate the tunnel water and sand inrush conditions. Therefore, the simulated tunnel water and sand inrush conditions also include a test chamber A simulating different pressures and different filling layers, a test ball valve B located on test chamber A, and a test temperature measuring sleeve C. Specifically, the lower layer of test chamber A is filled with soil layer D (or rock layer) in the water and sand inrush conditions, and the upper layer is a water pressure layer E. The liquid level of the water pressure layer is adjustable according to the pressure. Therefore, it meets the emergency operation requirements under different pressures, different soil layers, and different discharge diameters formed by the test ball valve. At the same time, the top of test chamber A is equipped with a manhole F, a pressure relief safety valve G, a pressure gauge H, and a water supply pipeline J. When the pressure gauge H on test chamber A exceeds the set value, the pressure relief safety valve G on test chamber A automatically opens to release pressure, simulating freezing under the required water pressure (at the same time, if the water pressure is insufficient, water is directly added from the water supply pipeline J to the middle of the water pressure layer E, and the water supply pipeline J is a right-angle pipe, so that the water entering the water pressure layer E spreads horizontally in all directions).

[0072] In some specific embodiments, it includes the following steps:

[0073] S1. Preparations before sealing:

[0074] (1) Wrap the outer periphery of the cryogenic tube where the liquid nitrogen outlet is located with plastic film to seal it tightly. The number of wrapping turns is 2 to 6. Use tape to wrap and fix the plastic film to the cryogenic tube.

[0075] (2) Adjust the ball valve and the pressure relief and exhaust passage to the closed state;

[0076] (3) Connect the liquid nitrogen pipeline to the cryogenic pipeline and tighten it by threading the bolts on the flange;

[0077] (4) Insert the temperature measuring tube into the test temperature measuring sleeve, and at the same time prepare an ice-water mixture as the temperature reference temperature. Then connect the temperature measuring series circuit and test it to check whether the reading is normal.

[0078] (5) Fill the lower space of the test chamber with the material to be tested, and form a water pressure layer with adjustable pressure above the material to be tested, so as to simulate the actual water and sand inrush conditions in the tunnel.

[0079] S2. Blocking Phase:

[0080] (1) Fully open the test ball valve on the test chamber that causes water and sand to gush out;

[0081] (2) After the water and sand flow out, use a freezing pipe that matches the diameter of the ball valve to be tested, operate the handwheel and rotate from the drilling tip to drill into the water and sand leakage area, where the drilling depth is 25~30cm.

[0082] (3) After insertion, secure the freezer tube with wire, and then open the ball valve on the freezer tube;

[0083] (4) The liquid nitrogen outlet is then opened, and the liquid nitrogen outlet pressure is adjusted to 1.0±0.1MPa. Then the pressurized supply begins, and the liquid nitrogen entering the freezing tube is discharged from the liquid nitrogen outlet to the water and sand inrush area and / or discharged from the opened pressure relief and exhaust channel. The flowing liquid nitrogen directly or indirectly freezes and seals the water and sand inrush area.

[0084] (5) After the liquid nitrogen supply begins, synchronize timing and temperature measurement are performed;

[0085] (6) Observe the state of water and sand inflow during the freezing process;

[0086] (7) When the pressure count value on the test chamber is greater than the set value, the pressure relief safety valve on the test chamber will automatically open to release pressure, simulating freezing under the required water pressure;

[0087] (8) After the water flow has completely stopped, close the ball valve on the refrigeration pipe to complete the sealing.

[0088] After adopting this device and freezing mode, the leakage point is directly or indirectly frozen with liquid nitrogen through the insertion of the freezing pipe. This fully utilizes the energy of liquid nitrogen vaporization to achieve rapid freezing of liquid water to solid state in areas with water and sand inrush. Therefore, this invention addresses several issues: First, under different pressures and soil layers, it provides multiple modes of direct and indirect liquid nitrogen freezing for rapid freezing, effectively and simply sealing leakage channels while avoiding disturbance to the surrounding soil from drilling and reducing risks. Second, the device allows for rotatable insertion, making operation convenient and providing a technical basis for the practical application of rapid liquid nitrogen freezing in engineering. Third, the use of liquid nitrogen for direct or indirect rapid freezing and sealing of leakage points further verifies the feasibility of directly freezing leakage points with liquid nitrogen under different pressures and geological conditions without drilling. Furthermore, by changing the outer diameter of the freezing pipe, configuration tests can be conducted to obtain a numerical model relationship between the difference in diameter between the channel and the freezing pipe and the sealing time, providing feasibility for actual construction. Fourth, after the freezing pipe is inserted into the soil layer… The freezing tube is kept dry to prevent freezing inside after nitrogen supply, which would affect freezing efficiency and effectiveness. Fifthly, the drilling tip facilitates drilling into the soil, and its tail diameter is approximately 5mm larger than the freezing tube diameter, especially important for freezing systems with a liquid nitrogen outlet, ensuring no damage to the plastic film during drilling. Sixthly, the baffle position marks the limit of the freezing tube's drilling, reducing water and sand flow and providing a sealing effect. The impeller facilitates drilling into the soil. The ball valve is the main control hub for liquid nitrogen entering the freezing tube, using a low-temperature, high-pressure resistant stainless steel ball valve that is initially closed. The pressure gauge reads the pressure inside the freezing tube, allowing for timely assessment of the pressure status. Seventhly, the direct contact mode, with the insertion of the liquid nitrogen transfer tube, accurately delivers liquid nitrogen to the outlet, reducing energy consumption and achieving optimal freezing of the designated area. The use of a circulating mold, with its front and rear distribution of the orifice and ports, ensures sufficient heat exchange, increasing freezing efficiency and effectiveness.

[0089] The present invention has been described in detail above, with the aim of enabling those skilled in the art to understand and implement the invention. However, this description should not be construed as limiting the scope of protection of the invention. All equivalent changes or modifications made in accordance with the spirit and essence of the invention should be included within the scope of protection of the invention.

Claims

1. A test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions, characterized in that: It includes a cryogenic tube forming an internal cavity, a drill tip sealed at one end of the cryogenic tube with its tip facing outward, a liquid nitrogen pipeline and a liquid nitrogen tank connected to the other end of the cryogenic tube, and a handwheel concentrically mounted on the outer periphery of the cryogenic tube. The drill tip is conical, with its center line coinciding with the center line of the cryogenic tube, and the outer diameter of the cone base is larger than the outer diameter of the cryogenic tube. Multiple liquid nitrogen outlets are formed at the end of the cryogenic tube near the drill tip, and a pressure relief and exhaust channel is formed inside the cavity. One or more layers of plastic film sealing layer are wrapped around the outer periphery of the sections corresponding to the multiple liquid nitrogen outlets. As the internal pressure of the cryogenic tube increases, the plastic film sealing layer is opened, and the liquid nitrogen entering the cryogenic tube is discharged from the liquid nitrogen outlet to the water and sand inrush area and discharged from the pressure relief and exhaust channel. The flowing liquid nitrogen directly or indirectly freezes the water and sand inrush area to form a blockage.

2. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 1, characterized in that: The plurality of liquid nitrogen outlets are divided into a plurality of liquid nitrogen outlet rows evenly distributed around the circumference of the cryogenic tube, and each of the liquid nitrogen outlet rows includes a plurality of liquid nitrogen outlets spaced apart along the length of the cryogenic tube.

3. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 2, characterized in that: The liquid nitrogen pipeline includes a liquid nitrogen transfer pipe inserted into a tube sheet at the other end of the cryogenic tube with its internal port near the liquid nitrogen outlet, and a flexible tube connecting the liquid nitrogen transfer pipe to the liquid nitrogen tank. The portion between the liquid nitrogen transfer pipe and the cryogenic tube forms a liquid nitrogen chamber. The cryogenic tube is also provided with a vent branch communicating with the liquid nitrogen chamber, a pressure relief valve disposed on the vent branch, and an exhaust pipe. The liquid nitrogen chamber, the vent branch, and the exhaust pipe are connected to form the pressure relief and exhaust channel.

4. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 3, characterized in that: In the cross-section of the cryogenic tube, the cross-sectional area formed by the liquid nitrogen transfer tube is larger than the cross-sectional area formed by the liquid nitrogen cavity.

5. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 3, characterized in that: The inner diameter of the drain branch is larger than the inner diameter of the liquid nitrogen transfer pipe, and the inner diameter of the drain branch is smaller than the inner diameter of the freezing pipe.

6. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 1, characterized in that: The cryogenic tube is further provided with a first tube and a second tube fixed to the inner wall, wherein the outer ends of the first tube and the second tube extend out of the cryogenic tube, and the length of the second tube extending into the cryogenic tube is less than the length of the first tube extending into the cryogenic tube; the liquid nitrogen pipeline is connected to the outer end of the first tube, and the outer end of the second tube is connected to the exhaust pipe. The liquid nitrogen entering the cryogenic tube indirectly contacts the water and sand inrush area and is discharged from the second tube and the exhaust pipe to form a circulation.

7. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 6, characterized in that: The inner end of the first tube is located near the drilling tip; the inner end of the second tube is located near the middle of the freezing tube.

8. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 6, characterized in that: The inner diameter of the first tube is larger than the inner diameter of the second tube.

9. The test device for liquid nitrogen freezing and sealing under tunnel water and sand inrush conditions according to claim 1, characterized in that: The cone angle formed by the drilling tip is an acute angle and is solid inside; and / or, the outer diameter of the cone bottom is D1, the outer diameter of the freezing tube is D2, and D1-D2≥5mm.

10. A method for liquid nitrogen freezing and sealing under simulated tunnel water and sand inrush conditions, characterized in that: It employs the liquid nitrogen freezing and sealing test device for tunnel water and sand inrush conditions as described in any one of claims 1 to 9. The test device further includes a limiting baffle concentrically mounted on the freezing tube, a ball valve communicating with the liquid nitrogen chamber inside the freezing tube, and a pressure gauge. The limiting baffle, the handwheel, the ball valve, and the pressure gauge are distributed at intervals from the middle of the freezing tube to the other end. The simulated tunnel water and sand inrush conditions also include a test chamber simulating different pressures and different filling material layers, a test ball valve located on the test chamber, and a test temperature measuring sleeve. The test device includes the following steps: S1. Preparations before sealing: (1) Wrap the outer periphery of the cryogenic tube where the liquid nitrogen outlet is located with plastic film to seal it tightly. The number of wrapping turns is 2 to 6. Use tape to wrap and fix the plastic film to the cryogenic tube. (2) Adjust the ball valve and the pressure relief and exhaust passage to the closed state; (3) Connect the liquid nitrogen pipeline to the cryogenic pipeline and tighten it by threading the bolts on the flange; (4) Insert the temperature measuring tube into the test temperature measuring sleeve, and at the same time prepare an ice-water mixture as the temperature reference temperature. Then connect the temperature measuring series circuit and test it to check whether the reading is normal. (5) Fill the lower space of the test chamber with the material to be tested, and form a water pressure layer with adjustable pressure above the material to be tested, so as to simulate the actual water and sand inrush conditions in the tunnel. S2. Blocking Phase: (1) Fully open the test ball valve on the test chamber that causes water and sand to gush out; (2) After the water and sand flow out, use a freezing pipe that matches the diameter of the ball valve to be tested, operate the handwheel and rotate from the drilling tip to drill into the water and sand leakage area, where the drilling depth is 25~30cm. (3) After insertion, secure the freezer tube with wire, and then open the ball valve on the freezer tube; (4) The liquid nitrogen outlet is then opened, and the liquid nitrogen outlet pressure is adjusted to 1.0±0.1MPa. Then the pressurized supply begins, and the liquid nitrogen entering the freezing tube is discharged from the liquid nitrogen outlet to the water and sand inrush area and / or discharged from the opened pressure relief and exhaust channel. The flowing liquid nitrogen directly or indirectly freezes and seals the water and sand inrush area. (5) After the liquid nitrogen supply begins, synchronize timing and temperature measurement are performed; (6) Observe the state of water and sand inflow during the freezing process; (7) When the pressure count value on the test chamber is greater than the set value, the pressure relief safety valve on the test chamber will automatically open to release pressure, simulating freezing under the required water pressure; (8) After the water flow has completely stopped, close the ball valve on the refrigeration pipe to complete the sealing.

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