Shield tunnel portal ring freezing plugging structure and construction method thereof

Abstract

The invention discloses a shield tunnel portal ring freezing and blocking structure and a construction method thereof. The shield tunnel portal ring freezing and blocking structure is used for protecting a tunnel portal ring foundation pit to be stable, a permanent bearing structure is formed by a main body part, freezing pipes can be stably installed on a tunnel portal pre-buried ring plate and an enclosure part, a grouting pipe is connected with the freezing pipes, the freezing pipes are reused, space and cost are saved, and the construction efficiency is improved. According to the construction method of the shield tunnel portal ring freezing blocking structure, through combination of the two cooling media, the first cooling medium can be adjusted to achieve efficient freezing, the second cooling medium maintains freezing at low cost, cost is saved, the overall efficiency is higher, heat preservation is conducted on the exposed face of the frozen soil curtain, cold energy is prevented from being transmitted to the concrete ring beam, and frost heaving of the structure is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of shield tunnel construction enclosure structure, and particularly relates to a shield tunnel portal ring freezing plugging structure and a construction method thereof. BACKGROUND

[0002] During the process of shield tunnel entering and exiting a hole, a ring-shaped gap is formed between the hole and the shield shell. In order to prevent a large amount of slurry from leaking into the well through the gap during the process of shield tunnel entering and exiting a hole, a sealing device with good performance must be arranged at the hole. A commonly used method is a technology of one-way hinge plate plus "curtain rubber plate" and a steel sleeve balance starting and receiving technology. Since the outer diameter of the segment is smaller than the outer diameter of the shield tunnel, after the shield tunnel enters and exits the hole, the curtain rubber plate or the steel sleeve is removed, and a gap still exists between the tunnel portal ring and the segment. A pre-embedded grouting pipe is usually used to grout and plug the gap. However, when the underground water pressure of the soil side is too large, the injected slurry cannot be quickly solidified and is easily washed out by the seepage of underground water, so that the plugging effect cannot be achieved. SUMMARY

[0003] To solve at least one of the above technical problems, the present application provides a shield tunnel portal ring freezing plugging structure and a construction method thereof, and the technical solutions are as follows.

[0004] The shield tunnel portal ring freezing plugging structure provided by the present application is used for a tunnel portal ring. The tunnel portal ring is formed by a surrounding part installed on the outside of a hole soil body and a main body part installed on the side of the surrounding part away from the hole soil body. A shield segment is installed in the tunnel portal ring. A concrete ring beam is arranged outside the tunnel portal ring along the tunnel portal ring. The shield tunnel portal ring freezing plugging structure comprises a tunnel portal pre-embedded ring plate, a freezing pipe and a grouting pipe. The tunnel portal pre-embedded ring plate is installed on the main body part, and participates in forming the tunnel portal ring. The freezing pipe is arranged in the tunnel portal ring. The freezing pipe is used to be installed on the surrounding part or the tunnel portal pre-embedded ring plate. The freezing pipe is used to freeze the gap between the tunnel portal pre-embedded ring plate and the shield segment and form a frozen soil curtain. The grouting pipe is connected to the freezing pipe. The grouting pipe is used for input and output of the freezing pipe. The grouting pipe is pre-embedded in the tunnel portal pre-embedded ring plate.

[0005] In some embodiments of the present application, the shield tunnel portal ring freezing plugging structure further comprises a heat preservation and insulation part installed between the frozen soil curtain and the concrete ring beam.

[0006] In some embodiments of the present application, at least three temperature measuring points are arranged on the freezing pipe at intervals.

[0007] The application also provides a construction method of the shield tunnel portal ring freezing plugging structure, which is applied to a shield starting end or receiving end and comprises the following steps: S1. sequentially mounting a surrounding part, a main body part and a portal pre-buried ring plate, leading a grouting pipe out of a freezing pipe and pre-buried grouting pipes; S2. conveying a first cooling medium into the freezing pipe to freeze a gap between the portal pre-buried ring plate and a shield pipe piece to form a frozen soil curtain; S3. stopping conveying the first cooling medium, conveying a second cooling medium and maintaining freezing of the frozen soil curtain; S4. insulating an exposed surface of the frozen soil curtain; S5. pouring a concrete ring beam on a side far away from the frozen soil curtain; S6. stopping conveying the second cooling medium and thawing the frozen soil curtain; S7. after the frozen soil curtain is completely frozen, grouting into an area where the frozen soil curtain is completely frozen through the grouting pipe.

[0008] S7. after the frozen soil curtain is completely frozen, grouting into an area where the frozen soil curtain is completely frozen through the grouting pipe.

[0009] In some embodiments of the application, the first cooling medium is liquid nitrogen and the second cooling medium is brine.

[0010] In some embodiments of the application, for step S3, a temperature measuring point is arranged, conveying of the liquid nitrogen is stopped when it is observed that the temperature measuring point reaches a preset temperature and the temperature is stable and the frozen soil curtain is complete, and conveying of the brine is started when it is observed that the temperature is -30°C.

[0011] In some embodiments of the application, before conveying the first cooling medium or the second cooling medium into the freezing pipe, air flow is conveyed into the freezing pipe and air tightness is detected.

[0012] In some embodiments of the application, before step S4 is performed after step S3 is completed, the exposed surface of the frozen soil curtain is leveled when a temperature difference between an input end and an output end of the brine is less than 2°C.

[0013] In some embodiments of the application, after the freezing pipe is mounted to the surrounding part, surface protection treatment is performed by using double quick cement.

[0014] In some embodiments of the application, before the shield arrives and after step S2 is completed, a portal ring sealing device is mounted, wherein: when the portal ring sealing device is applied to a shield starting end, the portal ring sealing device is removed after the shield starting is completed and step S3 is performed again; When applied to the shield receiving end, after the concrete ring beam in the step S5 is cured, the hole portal ring sealing device is removed, and then the step S6 is performed.

[0015] The shield hole portal ring freezing plugging structure has at least the following beneficial effects: the shield hole portal ring freezing plugging structure is used for protecting the stability of the hole portal ring foundation pit, the main body part forms a permanent bearing structure, the hole portal pre-buried ring plate and the enclosure part can stably install the freezing pipe, the grouting pipe is connected with the freezing pipe, the freezing pipe is reused, space and cost are saved, the construction method of the shield hole portal ring freezing plugging structure can adjust the first cooling medium to realize efficient freezing, the second cooling medium can maintain freezing at low cost, cost is saved, and the overall efficiency is higher. The exposed surface of the frozen soil curtain is insulated to block the transfer of cold energy to the concrete ring beam, and structure frost heaving is avoided.

[0016] Additional aspects and advantages of the application will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following description and drawings. BRIEF DESCRIPTION OF DRAWINGS

[0017] The application will be further illustrated below in combination with the drawings and examples. It should be noted that the examples embodied in the following drawings are exemplary and are used to explain the application, and cannot be understood as a limitation on the application.

[0018] Figure 1 Figure 1 is a diagram of a shield hole portal ring freezing plugging structure; Figure 2 Figure 2 is a diagram of grouting to the first gap; Figure 3 Figure 3 is a diagram of a freezing process; Figure 4 Figure 4 is a diagram of a second hole position; Figure 5 Figure 5 is a diagram of a first hole position; Figure 6 Figure 6 is a transverse sectional view of a pre-buried grouting pipe; Figure 7 Figure 7 is a transverse sectional view of a freezing pipe installation; Figure 8 Figure 8 is a transverse sectional view of a freezing curtain formation; Figure 9 Figure 9 is a diagram of a shield hole portal ring freezing plugging structure; Figure 1 Figure 10 is an enlarged view of a in figure 9; Figure 10 Figure 11 is a diagram of a shield hole portal ring freezing plugging structure; Figure 2 Figure 12 is an enlarged view of b in figure 11.

[0019] Reference signs: hole soil body 100; enclosure part 110; first hole 111; Main body part 200; second hole 210; Hole portal pre-buried ring plate 300; Grouting pipe 400; connecting pipe 410; Freezing tube 500; First freezing tube 510; Second freezing tube 520; Freezing equipment 530; Temperature measuring point 600; segment 700; first gap 800; thermal insulation part 900; concrete ring beam 1000. Detailed Implementation

[0020] The following is combined with Figures 1 to 10 The embodiments of this application are described in detail below, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0021] In the description of this application, it should be understood that the terms "center", "middle", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are 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, and therefore should not be construed as a limitation of this application.

[0022] In the description of this application, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0023] In the description of this application, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] In the description of the present application, if the description of the terms "one embodiment", "some embodiments", "one example", "some examples", "some embodiments", "illustrative embodiments", "example", "specific example", "some examples" and the like appear, it means that the specific features, structures, materials or characteristics described in combination with the embodiment or example are included in at least one embodiment or example of the present application. In the present description, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0025] The present application provides a shield tunnel portal ring freezing plugging structure, which is described below.

[0026] The shield tunnel portal ring freezing plugging structure is used for a portal ring, the portal ring is formed by a surrounding part 110 installed outside a tunnel soil body 100 and a main body part 200 installed on the side of the surrounding part 110 away from the tunnel soil body 100, a shield segment 700 is installed in the portal ring, a concrete ring beam 1000 is arranged outside the portal ring along the portal ring, and the shield tunnel portal ring freezing plugging structure comprises a portal pre-buried ring plate 300, a freezing pipe 500 and a grouting pipe 400, wherein: The portal pre-buried ring plate 300 is installed on the main body part 200, and the portal pre-buried ring plate 300 participates in forming the portal ring; The freezing pipe 500 is arranged in the portal ring, the freezing pipe 500 is used for being installed on the surrounding part 110 or being installed on the portal pre-buried ring plate 300, and the freezing pipe 500 is used for freezing the gap between the portal pre-buried ring plate 300 and the shield segment 700 and forming a frozen soil curtain. The gap between the portal pre-buried ring plate 300 and the shield segment 700 is a first gap 800.

[0027] Specifically, as shown in Figures 1 to 8 The whole after installation of the shield tunnel portal ring freezing plugging structure includes the surrounding part 110, the main body part 200, the portal pre-buried ring plate 300, the freezing pipe 500, the grouting pipe 400, the first gap 800 and the concrete ring beam 1000.

[0028] For the surrounding part 110, the surrounding part 110 is installed outside the tunnel soil body 100, the surrounding part 110 is provided with a first hole 111, the first hole 111 communicates with the portal ring, and the inner wall of the first hole 111 in the radial direction is provided with a first annular groove, and the inner wall of the first hole 111 in the radial direction is also used for installing the shield segment 700; As shown in Figure 1 , Figure 4 For the main body part 200, the main body part 200 is installed on the side of the surrounding part 110 away from the tunnel soil body 100, and the main body part 200 is provided with a second hole 210, and the second hole 210 communicates with the portal ring; For the portal pre-embedded ring plate 300, installed on the inner wall of the second hole 210, the radial inner wall of the portal pre-embedded ring plate 300 is provided with a second annular groove; For the first gap 800, located between the portal pre-embedded ring plate 300 and the shield segment 700, and also located on the side of the enclosure part 110 away from the tunnel soil body 100; For the freezing pipe 500, which is annular, the freezing pipe 500 is used to form a frozen soil curtain in the first gap 800, and the freezing pipe 500 includes a first freezing pipe 510 and a second freezing pipe 520, the first freezing pipe 510 is pre-embedded in the first annular groove, and the second freezing pipe 520 is pre-embedded in the second annular groove; For the grouting pipe 400, connected to the freezing pipe 500, the grouting pipe 400 is used for input and output of the freezing pipe 500, and the grouting pipe 400 is pre-embedded in the main body part 200, and the grouting pipe 400 is used to form a grouting filling body in the first gap 800; The enclosure part 110 maintains soil stability when excavating the tunnel soil body 100, reduces the risk of collapse, and combines Figure 5 As shown, the enclosure part 110 is provided with a first hole 111, and the radial inner wall of the first hole 111 is also used to install the shield segment 700, and the shield machine works through the first hole 111. The enclosure part 110 also provides an installation path for the freezing pipe 500 and also has a certain effect on blocking the infiltration of underground water to the construction area.

[0029] The main body part 200 is installed on the side of the enclosure part 110 away from the tunnel soil body 100, and bears the ground pressure and water load, and the main body part 200 is provided with a second hole 210, which provides an installation path for the portal pre-embedded ring plate 300 and also provides an installation path for the grouting pipe 400.

[0030] The portal pre-embedded ring plate 300 is installed on the radial inner wall of the second hole 210, which can be used to install the portal sealing device, fix the rubber of the connecting part or can accommodate the water stop ring, form the portal waterproof interface, and the portal pre-embedded ring plate 300 is also provided with a second annular groove on the radial inner wall, which provides an installation path for the second freezing pipe 520.

[0031] Combined with Figure 1 As shown, the first gap 800 is located between the portal pre-embedded ring plate 300 and the shield segment 700, and also located on the side of the enclosure part 110 away from the tunnel soil body 100, and the first gap 800 is used to form a frozen soil curtain, and after the frozen soil curtain is frozen, a grouting filling body is formed by grouting to perform thawing sinking compensation.

[0032] The freezing pipe 500 is annular, the first freezing pipe 510 is embedded in the first annular groove, and the second freezing pipe 520 is embedded in the second annular groove. The annular grooves serve as a guide structure to ensure the construction accuracy of the spacing and angle of the freezing pipe 500. The first annular groove disperses the cold shrinkage stress of the first freezing pipe 510 to the enclosure part 110, and the second annular groove disperses the cold shrinkage stress of the second freezing pipe 520 to the portal embedded ring plate 300. The freezing pipe 500 can quickly form a frozen soil skeleton through liquid nitrogen, and then maintain low temperature through low-temperature brine, thereby achieving fast formation of a frozen soil curtain and saving costs. The temperature range of the low-temperature brine is -25°C to -30°C.

[0033] As shown in Figure 6 As shown in Figure 2 As shown in

[0034] As shown in Figure 1 As shown in

[0035] As shown in Figure 1 As shown in Figure 9 As shown in

[0036] Further, the heat preservation and insulation part 900 is a polyurethane plate, which blocks the transmission of frozen soil cold to the ring beam concrete. The polyurethane plate has ultra-low thermal conductivity, blocks the transmission of frozen soil cold to the concrete ring beam 1000, controls the temperature difference between the heat preservation and insulation part 900 and the concrete ring beam 1000 to be relatively low, avoids temperature cracks, reduces cold loss, and reduces the amount of cooling medium. It also has high strength and compression resistance, can withstand the pressure transmitted by the cast concrete ring beam 1000, avoid the collapse of the heat preservation layer, and has waterproof and moisture-proof performance to prevent groundwater penetration.

[0037] In some embodiments, at least three temperature measuring points 600 are arranged on the freezing pipe 500. As shown in Figure 1 and Figure 7 , the temperature measuring points 600 are arranged between the first freezing pipe 510 and the first annular groove, between the second freezing pipe 520 and the second annular groove, and in the first gap 800. At least three temperature measuring points 600 are arranged along the first annular groove and the second annular groove, which can measure temperature more accurately and with less error.

[0038] In some embodiments, the freezing pipe 500 is connected to a liquid supply pipe and a liquid return pipe, and the liquid supply pipe and the liquid return pipe are connected to the freezing device 530. As shown in Figure 3 , Figure 7 , Figure 10 , the freezing pipe 500 is connected to the grouting pipe 400, the grouting pipe 400 is connected to the freezing device 530 through the connecting pipe 410, and the connecting pipe 410 includes a liquid supply pipe and a liquid return pipe. One of them is a liquid supply pipe that provides frozen medium from the freezing device 530 to the freezing pipe 500, and the other is a liquid return pipe that recovers frozen medium to the freezing device 530, avoiding local retention and uneven freezing, and improving cold utilization rate.

[0039] In some embodiments, as shown in Figure 1 and Figure 4 , the first freezing pipe 510 extends 15-30 cm in the axial direction into the hole soil body. After the hole portal is drilled, the hole soil body 100 is prone to form a cold loss zone. The first freezing pipe 510 extending 15-30 cm can ensure that the frozen soil curtain is in close contact with the enclosure 110, avoiding the occurrence of unfrozen areas at the junction and causing water seepage. The deeply inserted first freezing pipe 510 can buffer the damage of vibration to the frozen soil curtain and reduce the risk of frozen soil cracking. The lower limit of 15 cm ensures that the first freezing pipe 510 does not collide with the inner wall of the first hole, meeting the thickness of the drilled reserved protection layer, and the upper limit of 30 cm ensures that the marginal benefit of cold is not too low, preventing the construction difficulty from increasing dramatically.

[0040] Further, the freezing pipe 500 is made of stainless steel pipe, which improves strength, corrosion resistance and toughness at extremely low temperature, prevents brittle fracture when liquid nitrogen is input, has high heat conduction efficiency and anti-frost heaving deformation ability, and has a longer service life.

[0041] This application also provides a construction method for the aforementioned shield tunnel portal freezing and sealing structure, which is described below.

[0042] The construction method for freezing and sealing the tunnel portal ring of a shield tunnel is applied to the launching or receiving end of the shield tunnel, including: S1. Install the retaining part 110, the main body 200, and the pre-embedded ring plate 300 of the tunnel portal in sequence. Lead out the grouting pipe 400 from the freezing pipe 500 and pre-embed the grouting pipe 400. S2. The first cooling medium is delivered into the freezing pipe 500 to freeze the gap between the pre-embedded ring plate 300 of the tunnel portal and the shield segment 700 to form a frozen soil curtain. S3. Stop supplying the first cooling medium and switch to supplying the second cooling medium to maintain the frozen soil curtain; S4. Insulate the exposed surface of the frozen soil curtain; S5. Construct a 1000mm concrete ring beam on the side furthest from the frozen soil curtain; S6. Stop supplying the second cooling medium and thaw the frozen soil curtain; S7. After the frozen soil curtain has completely thawed, grout is injected into the area where the frozen soil curtain has completely thawed through the grouting pipe 400.

[0043] For S1, combined Figure 4 As shown, the retaining part 110, the main body 200, and the portal embedded ring plate 300 are installed in sequence. First, the first freezing pipe 510 is installed into the first annular groove. Then, the second freezing pipe 520 is installed into the second annular groove. Subsequently, the grouting pipe 400 is led out from the first freezing pipe 510 and the second freezing pipe 520. The grouting pipe 400 is embedded in the portal embedded ring plate 300 and an airtightness test is performed to ensure the integrity of the freezing pipe 500 and the connection between the grouting pipe 400 and the freezing pipe 500.

[0044] Combination Figure 6 As shown, the grouting pipe 400 is arranged in a ring along the tunnel portal. After the airtightness test is completed and the airtightness is confirmed to be good, the grouting port of the pre-embedded grouting pipe 400 is protected.

[0045] For S2, combined Figure 3 and Figure 10 As shown, the grouting pipe 400 is connected to the refrigeration equipment 530 via a connecting pipe 410. One of the connecting pipes 410 is a supply pipe, providing the freezing medium from the refrigeration equipment 530 to the freezing pipe 500; the other is a return pipe, recovering the freezing medium back to the refrigeration equipment 530. This prevents uneven freezing caused by localized stagnation and improves the utilization rate of cooling capacity. A first cooling medium is supplied into the freezing pipe 500, causing the soil in the first gap 800 to freeze and form a frozen soil curtain, isolating the groundwater at the tunnel portal.

[0046] For S3, when the soil in the first gap 800 freezes to form a frozen soil curtain, and the frozen soil curtain is observed to be intact with no further water seepage, the supply of the first cooling medium to the freezing pipe 500 is stopped, and the supply of the second cooling medium is switched to maintain the freezing of the frozen soil curtain. The first and second cooling media are selected reasonably according to the engineering needs to appropriately adjust the freezing speed and freezing cost. For example, the first cooling medium can be used to quickly freeze and form a frozen soil curtain, and then the lower-cost second cooling medium can be used to maintain the freezing.

[0047] For S4, the exposed surface of the frozen soil curtain is insulated to prevent the loss of cold energy from the frozen soil curtain with the first gap of 800.

[0048] For S5, combined Figure 3 As shown, a concrete ring beam 1000 is poured on the side of the frozen soil curtain away from the frozen soil curtain. During the process, the supply and return of the second cooling medium are maintained. At the same time, the pouring of the concrete ring beam 1000 also seals the gap between the tunnel segment 700 and the pre-embedded ring plate 300 of the tunnel portal. The exposed surface of the frozen soil curtain is insulated to block the transfer of cold energy from the frozen soil to the concrete ring beam 1000, avoid structural frost heave, and shorten the final setting time of the concrete ring beam 1000.

[0049] For S6, after testing and confirming that the structural strength of the 1000mm concrete ring beam meets the standards, the supply of the second cooling medium is stopped, the flow rate of the second cooling medium is gradually reduced, the supply pipe is then closed, and the return pipe is kept emptied. The frozen soil curtain in the first gap of 800mm is then thawed.

[0050] The construction method of the frozen sealing structure of the tunnel portal ring uses a combination of dual cooling media. The first cooling medium can be adjusted to achieve efficient freezing, while the second cooling medium maintains freezing at low cost, saving costs and increasing overall efficiency. It also insulates the frozen soil curtain, blocks the transfer of cold energy to the concrete ring beam, and avoids structural frost heave.

[0051] In some embodiments, the first cooling medium is liquid nitrogen, and the second cooling medium is brine. The brine temperature range is -25°C to -30°C. After ensuring the pipeline is intact through an airtightness test, in step S2, liquid nitrogen is supplied to the freezing pipe 500 to freeze the first gap 800 between the tunnel portal embedded ring plate 300 and the shield segment 700, forming a frozen soil curtain. Liquid nitrogen can quickly form a frozen soil skeleton, shortening the construction period. When the frozen soil curtain meets the standard and there is no water seepage, the liquid supply pipe is stopped, while the return pipe remains open, and the residual liquid nitrogen in the pipeline is drained through a valve or pump. When the temperature of the freezing pipe 500 reaches the target temperature, low-temperature brine is supplied to maintain the freezing of the frozen soil curtain. After the concrete ring beam 1000 passes the inspection, the flow rate of the low-temperature brine is reduced in stages. The rapid formation of the frozen soil skeleton by liquid nitrogen, followed by maintenance of freezing by low-temperature brine, is highly efficient and economical.

[0052] Further, after stopping the input of low-temperature brine, antifreeze solution is injected to protect the pipeline, such as glycol solution.

[0053] Specifically, for step S3, temperature measuring points 600 are arranged in the first and second annular grooves, wherein the temperature measuring points 600 are arranged between the first freezing pipe 510 and the first annular groove, between the second freezing pipe 520 and the second annular groove, and in the first gap 800, which is used to monitor the temperature of the frozen soil curtain and the temperature of the grouting filling body formed after grouting, so as to control the timing of thawing and the timing of pouring the concrete ring beam 1000.

[0054] When it is observed that the temperature measuring points 600 reach the preset temperature and the temperature is stable, and the frozen soil curtain is complete, the delivery of liquid nitrogen is stopped, and when the temperature is observed to be -30°C, the delivery of low-temperature brine is switched. The liquid nitrogen supply flow is gradually reduced to avoid thermal stress impact. When the temperature of the temperature measuring points 600 reaches -30°C and the thickness of the frozen soil curtain meets the standard, the liquid nitrogen is emptied, and the delivery of low-temperature brine is switched.

[0055] For S7, thawing can be performed by natural thawing method or active thawing method. For the natural thawing method, the temperature measuring points 600 are kept to measure the first gap 800. When the average temperature of the temperature measuring points 600 in the first gap 800 is greater than or equal to -2°C, grouting is started. For the active thawing method, 40°C warm water is injected into the freezing pipe 500 to accelerate thawing, and the settlement of the first gap 800 is monitored. Figure 1 As shown, the liquid supply pipe and the liquid return pipe are removed, grouting is performed in the first gap 800 of the completely thawed frozen soil curtain through the grouting pipe 400 to form a grouting filling body, the grouting pipe 400 is connected to the freezing pipe 500, grouting is performed in the first freezing pipe 510 and the second freezing pipe 520 to seal, the first freezing pipe 510 and the second freezing pipe 520 are reused, and space and cost are saved.

[0056] In some embodiments, before the first cooling medium or the second cooling medium is delivered to the freezing pipe 500, a high-pressure gas flow is delivered to the freezing pipe 500 and air tightness detection is performed. In the process of removing residual liquid nitrogen, the high-pressure gas flow uses dry nitrogen at a pressure of 0.4-0.6 MPa, and in the process of removing residual brine, the high-pressure gas flow uses compressed air at a pressure of 0.8-1.2 MPa. After the freezing device 530 is connected, the high-pressure gas flow is delivered to the freezing pipe 500 to remove impurities in the pipe and perform air tightness detection. The delivery of the first cooling medium to the freezing pipe 500 is stopped, the high-pressure gas flow is delivered to remove impurities in the pipe, air tightness detection is performed, and then the delivery of the second cooling medium is switched to maintain the freezing of the frozen soil curtain. Further, after the liquid nitrogen is exhausted and the high-pressure gas flow is used to remove impurities in the pipe, hot brine is injected for cleaning to dissolve ice crystals in the pipe and prevent salt crystallization and blockage. After the hot brine is used for cleaning, low-temperature brine is delivered. The delivery of the high-pressure gas flow has the effect of removing impurities in the pipe and the effect of air tightness detection, which prevents the freezing pipe 500 from being contaminated or leaking.

[0057] Specifically, before the step S3 is completed and the step S4 is performed, when the temperature difference between the input end and the output end of the low-temperature brine is less than 2°C, the exposed surface of the frozen soil curtain is leveled, and the heat insulation part 900 is installed. The initial temperature of the output low-temperature brine and the temperature of the recovered low-temperature brine are monitored to maintain a temperature difference of less than or equal to 2°C, thereby preventing local stagnation and uneven freezing.

[0058] Further, a pressure relief valve is provided for the liquid return pipe to prevent overpressure when the liquid nitrogen gasifies.

[0059] In some embodiments, after the first freezing pipe 510 is installed in the first annular groove, a surface protection treatment is performed using double-quick cement. The double-quick cement mortar is filled into the bottom of the first annular groove to wrap 1 / 3 of the first freezing pipe 510, a steel mesh is then buried to enhance the crack resistance, and finally the double-quick cement is applied and leveled. The double-quick cement has the advantages of rapid solidification, strong anti-permeability, low cracking tendency, good sealing, protection of the first freezing pipe 510, and prolongation of the service life, which also makes the freezing of the frozen soil curtain more uniform.

[0060] In some embodiments, the hole portal ring sealing device is installed before the shield arrives and after step S2 is completed, wherein the construction method of the shield hole portal ring freezing plugging structure is applied to the shield starting end, after the shield starting is completed, the hole portal ring sealing device is removed, and then step S3 is implemented. If the curtain rubber sealing device is used, the curtain rubber sealing device is installed after the frozen soil curtain in S2 is accepted, the convex surface of the curtain rubber sealing device faces the outside of the hole soil body 100, the frozen soil curtain blocks groundwater, the curtain rubber sealing device prevents leakage during the advancement of the shield machine, avoids water and soil from flowing into the hole portal ring when the shield starts, and is more efficient to install under the frozen soil curtain. After the shield tail completely enters the hole soil body 100, the curtain rubber sealing device is removed, and the curtain rubber sealing device is a waterproof guarantee, after the removal, the freezing pipe 500 can be switched to low-temperature brine to maintain the frozen soil curtain freezing.

[0061] The construction method of the shield hole portal ring freezing plugging structure is applied to the shield receiving end, after the concrete ring beam in step S5 is finally cured, the hole portal ring sealing device is removed, and then step S6 is performed. When applied to the shield receiving end, the curtain rubber sealing device is installed after the frozen soil curtain in S2 is accepted, the frozen soil curtain and the curtain rubber sealing device realize double-barrier anti-penetration water inrush, prevent high water pressure from breaking the un-solidified concrete ring beam 1000. After the concrete ring beam 1000 is finally cured, it is removed to prevent the concrete ring beam 1000 from being broken by water pressure due to premature removal, wherein the low-temperature brine maintains freezing until the concrete ring beam 1000 hardens, avoids the first gap 800 from melting and sinking to cause settlement, and the frozen soil curtain and the curtain rubber sealing device cooperate to maintain stability.

[0062] The embodiments of the present application are described in detail above in combination with the drawings, but the present application is not limited to the above-described embodiments, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

Claims

1. A shield tunnel portal ring freezing and sealing structure, used for a portal ring, wherein the portal ring is formed in a retaining part installed on the outside of the tunnel soil and a main body installed on the side of the retaining part away from the tunnel soil, shield tunnel segments are installed inside the portal ring, and a concrete ring beam is arranged along the portal ring outside the portal ring, characterized in that, The shield tunnel portal freezing and sealing structure includes: An embedded ring plate for the tunnel portal is installed on the main body, and the embedded ring plate for the tunnel portal ring is used to form the tunnel portal ring. A freezing pipe is installed inside the portal ring. The freezing pipe is used to install on the retaining part or on the portal pre-embedded ring plate. The freezing pipe is used to freeze the gap between the portal pre-embedded ring plate and the shield segment and form a frozen soil curtain. The grouting pipe is connected to the freezing pipe and is used for the input and output of the freezing pipe. The grouting pipe is pre-embedded in the pre-embedded ring plate of the tunnel portal.

2. The shield tunnel portal freezing and sealing structure according to claim 1, characterized in that: The shield tunnel portal freezing and sealing structure also includes a thermal insulation part, which is installed between the frozen soil curtain and the concrete ring beam.

3. The shield tunnel portal freezing and sealing structure according to claim 1, characterized in that: At least three temperature measuring points are spaced apart on the freezing tube.

4. A construction method for a shield tunnel portal freezing and sealing structure as described in any one of claims 1 to 3, applied to the shield launching or receiving end, characterized in that, Includes the following steps: S1. Install the retaining structure, main structure, and pre-embedded ring plate at the tunnel entrance in sequence, and lead out the grouting pipe from the freezing pipe and pre-embed the grouting pipe; S2. The first cooling medium is delivered into the freezing pipe to freeze the gap between the pre-embedded ring plate of the tunnel portal and the shield segment to form a frozen soil curtain. S3. Stop supplying the first cooling medium and switch to supplying the second cooling medium to maintain the frozen soil curtain; S4. Insulate the exposed surface of the frozen soil curtain; S5. Construct a concrete ring beam on the side furthest from the frozen soil curtain; S6. Stop supplying the second cooling medium and thaw the frozen soil curtain; S7. After the frozen soil curtain has completely thawed, grout is injected into the area where the frozen soil curtain has completely thawed through the grouting pipe.

5. The construction method of the shield tunnel portal freezing and sealing structure according to claim 4, characterized in that: The first cooling medium is liquid nitrogen, and the second cooling medium is brine.

6. The construction method of the shield tunnel portal freezing and sealing structure according to claim 5, characterized in that: For step S3, set a temperature measuring point. When the temperature measuring point is observed to reach the preset temperature and the temperature is stable, and the frozen soil curtain is observed to be intact, stop supplying liquid nitrogen. When the temperature is observed to be -30°C, switch to supplying brine.

7. The construction method of the shield tunnel portal freezing and sealing structure according to claim 4, 5, or 6, characterized in that: Before supplying the first or second cooling medium to the freezing pipe, airflow is supplied to the freezing pipe and an airtightness test is performed.

8. The construction method of the shield tunnel portal freezing and sealing structure according to claim 6, characterized in that: Before proceeding to step S4 after completing step S3, when the temperature difference between the input and output ends of the brine is less than 2°C, the exposed surface of the frozen soil curtain should be leveled before installing the thermal insulation part.

9. The construction method of the shield tunnel portal freezing and sealing structure according to claim 4, characterized in that: After the freezing pipe is installed into the enclosure, its surface is protected with quick-setting cement.

10. The construction method of the shield tunnel portal freezing and sealing structure according to claim 4, characterized in that: Before the tunnel boring machine arrives and after step S2 is completed, the portal sealing device is installed, wherein: When applied to the starting end of a tunnel boring machine (TBM), after the TBM is launched, the portal ring sealing device is removed before proceeding to step S3. When applied to the shield receiving end, after the concrete ring beam in step S5 has set, the portal ring sealing device is removed, and then step S6 is performed.

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