Shield launching construction method in water-rich soft soil stratum with confined water

Abstract

This invention discloses a method for shield tunneling launch in water-rich soft soil strata with confined water, comprising: designing ground freezing reinforcement to determine the range of the freezing curtain; constructing freezing holes and conducting pressure tests and deflection measurements; installing a freezing station for active freezing and controlling the brine temperature in stages; sequentially installing a first layer of curtain rubber sheet, an external steel box, and a second layer of curtain rubber sheet on the pre-embedded steel ring at the tunnel portal to form a double-layer curtain sealing structure; removing the tunnel portal after monitoring and verifying the freezing effect through temperature measuring holes; sealing the gaps using the double-layer curtain rubber sheet during shield launch, and further sealing by grouting the external steel box. By comprehensively utilizing horizontal freezing reinforcement, an external steel box, and double-layer curtain measures, a complete safety assurance system is formed, effectively blocking confined water and preventing mud and water leakage. This method is characterized by strong construction adaptability, economic efficiency, and suitability for the safe launch of shield tunnels in water-rich soft soil strata with high water pressure.

Description

Technical Field

[0001] This invention relates to the field of tunnel shield construction technology, specifically to a method for launching a shield tunnel at a location with confined water in water-rich soft soil strata. Background Technology

[0002] With the continuous advancement of urbanization, tunnel boring machine (TBM) construction plays an increasingly important role in urban underground construction. Water-rich soft soil strata, as a complex geological environment, are characterized by high water content, easy liquefaction, and high confined water head. In underground engineering projects such as subways and tunnels, the liquefaction and settlement of soft soil can seriously affect the safety and stability of the project. Traditional TBM launching methods typically employ cement mixing piles or high-pressure jet grouting piles for end reinforcement. However, under high confined water head conditions, single ground reinforcement measures are often insufficient to completely block the path of groundwater inflow, easily leading to water and sand inrush accidents during portal breaching, which can severely cause ground subsidence.

[0003] Existing technologies include cases of using horizontal freezing reinforcement for shield tunneling launches. However, simple freezing reinforcement still carries the risk of leakage during long-term shield tunneling as the frozen walls thaw. There are also methods using steel sleeves for sealed launches, but these are bulky, complex to install, and costly. Therefore, how to combine the advantages of multiple technologies to form a safe, economical, and efficient shield tunneling launch method for water-rich soft soil strata has become an urgent technical problem to be solved. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a method for shield tunneling initiation at locations with confined water in water-rich soft soil strata. This method involves forming a temporary support structure through horizontal freezing reinforcement, providing rigid support through an external steel box, and using double-layer curtain fabric for dynamic sealing, thereby comprehensively solving the risks of water and sand inrush during shield tunneling initiation in water-rich soft soil strata.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for shield tunneling initiation at confined water locations in water-rich soft soil strata includes the following steps:

[0007] Step 1, Ground freezing reinforcement design: Determine the design range of the freezing curtain, so that the cross-sectional outline of the freezing curtain exceeds the outer outline of the tunnel structure, and form a ring-shaped freezing reinforcement body around the tunnel structure. The freezing curtain extends the design length along the longitudinal direction of the tunnel.

[0008] Step 2, construction of freezing holes: Drill freezing holes at the starting portal. The freezing holes include an outer ring of freezing holes and an inner ring of freezing holes arranged around the tunnel outline. Place freezing pipes in the freezing holes, pressure test the freezing pipes for leaks, and then place liquid supply pipes in the freezing pipes.

[0009] Step 3, installation and active freezing of the refrigeration station: Install the refrigeration unit and connect the brine pipeline. Actively freeze the formation by supplying low-temperature brine through the freezing pipe until the thickness of the freezing curtain, the average temperature, and the temperature at the interface between the freezing curtain and the underground continuous wall reach the design specifications.

[0010] Step 4, installation of external steel box and double curtain: Install the first curtain rubber plate on the pre-embedded steel ring of the tunnel portal, then install the external steel box on the outside of the first curtain rubber plate, and seal the external steel box with the pre-embedded steel ring of the tunnel portal. Then install the second curtain rubber plate on the outside of the steel box to form a double-layer curtain sealing structure.

[0011] Step 5, verification of freezing effect and removal of tunnel portal: After confirming that the frozen curtain has reached the design strength by monitoring data through temperature measurement holes, exploratory holes are drilled within the tunnel portal area to further verify the sealing and strength of the frozen curtain. Then, the underground continuous wall within the tunnel portal area is removed.

[0012] Step Six, Shield Launch and Sealing Control: The shield machine cutterhead enters the tunnel portal and passes through the second curtain rubber plate, the external steel box, and the first curtain rubber plate in sequence. The double curtain rubber plates seal the gap between the shield machine and the tunnel portal to prevent mud and water from leaking out.

[0013] Furthermore, in step two, the freezing pipe is made of low-carbon seamless steel pipe. After the freezing pipe is lowered, the pressure for pressure testing and leak detection is not less than twice the working pressure of the brine, and the pressure drop during the stabilization time does not exceed the specified range.

[0014] Furthermore, in step three, the brine temperature is controlled in stages during the active freezing process. In the early stage of freezing, the brine temperature is reduced to below the first temperature threshold. In the middle stage of freezing, the brine temperature is reduced to below the second temperature threshold, which is lower than the first temperature threshold. Before the tunnel entrance is removed, the brine temperature is reduced to below the third temperature threshold, which is lower than the second temperature threshold.

[0015] Furthermore, in step four, the external steel box is assembled from multiple segmented steel boxes, with adjacent segmented steel boxes connected by bolts, and the contact surface between the external steel box and the pre-embedded steel ring of the tunnel entrance is sealed by welding.

[0016] Furthermore, the external steel box has a ring-shaped box structure with internal stiffening ribs and grouting holes for injecting filling grout into the steel box when necessary.

[0017] Furthermore, in step two, after the freezing hole construction is completed, the drilling deviation is measured, the final hole spacing of the freezing holes is controlled within the design range, and additional holes are made in areas where the spacing exceeds the standard.

[0018] Furthermore, in step five, after drilling the test hole, the test hole is sealed and the test hole location is insulated to prevent the frozen curtain from melting locally.

[0019] Furthermore, in step four, both the first and second curtain rubber sheets are fixed to the pre-embedded steel ring or external steel box of the tunnel entrance by means of hinge plates and bolts.

[0020] Furthermore, in step three, the brine flow rate of the freezing holes is monitored during the active freezing period, and the brine flow rate of a single hole is kept at no less than the design flow rate, while the temperature difference between the outgoing brine and the return brine is controlled within the design range.

[0021] Furthermore, in step six, during the tunnel boring machine's initial launch, sealing grease or filling slurry is injected into the steel box through the grouting holes on the external steel box to assist the double-layered curtain rubber plate in sealing.

[0022] The present invention, which adopts the above technical solution, has the following prominent features compared with the prior art:

[0023] Multiple technical safeguards: This method comprehensively utilizes horizontal freezing reinforcement, external steel boxes, and double-layer curtain fabric. Freezing reinforcement forms a temporary support structure to block groundwater, the external steel box provides rigid support to enhance stability, and the double-layer curtain fabric achieves dynamic sealing. These three elements work together to form a complete safety guarantee system. Enhanced waterproofing: The combined design of the external steel box and double-layer curtain fabric provides both rigid protection and flexible sealing. The double-layer curtain fabric tightly adheres to the shield machine's outer shell when the tunnel boring machine passes, effectively preventing mud and water leakage and solving the problem of easy failure of traditional single-seal structures. Strong construction adaptability: This method is suitable for high water pressure, water-rich soft soil strata, especially for locations with confined water. It eliminates the need for large-scale ground reinforcement and pipeline relocation, offering high construction flexibility and minimal impact on the surrounding environment. Economical and efficient: Compared to traditional mixing pile reinforcement or full-ring steel sleeve starting, this method has lower material costs, lower machinery costs, and higher operational efficiency, significantly saving on project costs. Attached Figure Description

[0024] Figure 1 This is a construction flowchart of an embodiment of the present invention.

[0025] Figure 2 This is a schematic cross-sectional view of the frozen curtain in an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the planar arrangement of freezing holes and temperature measuring holes in an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of the installation structure of the external steel box and double-layer curtain in an embodiment of the present invention.

[0028] Explanation of the attached diagram labels: 1. Freezing curtain; 2. Starting portal; 3. Freezing hole; 4. Temperature measuring hole; 5. Embedded steel ring; 6. First layer of curtain rubber sheet; 7. External steel box; 8. Second layer of curtain rubber sheet. Detailed Implementation

[0029] The present invention will be further illustrated below with reference to specific embodiments. The purpose of this illustration is solely to provide a better understanding of the invention. Therefore, the examples given do not limit the scope of protection of the present invention.

[0030] like Figures 1 to 4 As shown in the figure, this embodiment presents a shield tunneling initiation method at the location of confined water in water-rich soft soil strata, including the following steps:

[0031] Step 1, design of ground freezing reinforcement: determine the design range of freezing curtain 1, so that the cross-sectional outline of freezing curtain 1 exceeds the outer outline of the tunnel structure, and forms a ring-shaped freezing reinforcement body around the tunnel structure. Freezing curtain 1 extends the design length along the longitudinal direction of the tunnel.

[0032] Step 2, Construction of Freezing Holes: Freezing holes 3 are drilled at the starting portal 2. Freezing holes 3 include an outer ring and an inner ring of freezing holes arranged around the tunnel outline. Freezing pipes are lowered into freezing holes 3 and pressure tested for leaks. Then, a supply pipe is lowered into the freezing pipe. The freezing pipe is made of low-carbon seamless steel. After the freezing pipe is lowered, the pressure during the pressure test is no less than twice the working pressure of the brine, and the pressure drop during the stabilization time does not exceed the specified range. After the construction of freezing holes 3 is completed, borehole deviation is measured. The final spacing of freezing holes 3 is controlled within the design range; areas with excessive spacing are filled with additional holes.

[0033] Step 3, Installation and Active Freezing of the Cryogenic Station: Install the refrigeration unit and connect the brine pipeline. Actively freeze the formation by supplying low-temperature brine through the freezing pipe until the thickness, average temperature, and interface temperature between the frozen curtain 1 and the diaphragm wall reach the design specifications. During the active freezing process, the brine temperature is controlled in stages: in the early stage, the brine temperature decreases below the first temperature threshold; in the middle stage, it decreases below the second temperature threshold (below the first threshold); and before the tunnel portal is removed, the brine temperature decreases below the third temperature threshold (below the second threshold). During active freezing, the brine flow rate of freezing well 3 is monitored, ensuring that the single-well brine flow rate is not lower than the design flow rate, and the temperature difference between the outgoing brine and the return brine is controlled within the design range.

[0034] Step 4, Installation of external steel box and double-layer curtain cloth: Install the first curtain rubber sheet 6 on the embedded steel ring 5 of the portal, then install the external steel box 7 outside the first curtain rubber sheet 6. The external steel box 7 is hermetically connected to the embedded steel ring 5 of the portal. Then install the second curtain rubber sheet 8 outside the steel box to form a double-layer curtain seal structure. The external steel box 7 is assembled by multiple segmented steel boxes, and the adjacent segmented steel boxes are connected by bolts. The contact surface between the external steel box 7 and the embedded steel ring 5 of the portal is sealed by welding. The external steel box 7 can also be a ring-shaped box structure with stiffening ribs inside. The external steel box 7 is also provided with grouting holes for injecting filling slurry into the inside of the steel box when necessary. Both the first curtain rubber sheet 6 and the second curtain rubber sheet 8 are fixed on the embedded steel ring 5 of the portal or the external steel box 7 through hinge pressing plates and bolts.

[0035] Step 5, Verification of freezing effect and removal of portal: After confirming that the freezing curtain 1 has reached the design strength through the monitoring data of the temperature measuring holes 4, drill exploration holes within the portal range to further verify the sealing performance and strength of the freezing curtain 1, and then remove the diaphragm wall within the portal range. After drilling the exploration holes, seal the exploration holes and perform heat preservation treatment on the positions of the exploration holes to prevent partial melting of the freezing curtain 1.

[0036] Step 6, Shield starting and sealing control: The cutter head of the shield machine enters the portal, passes through the second curtain rubber sheet 8, the external steel box 7 and the first curtain rubber sheet 6 in sequence, and seals the gap between the shield machine and the portal through the double-layer curtain rubber sheet to prevent mud and water from leaking out. During the starting process of the shield machine, inject sealing grease or filling slurry into the inside of the steel box through the grouting holes on the external steel box 7 to assist the double-layer curtain rubber sheet for sealing.

[0037] A specific embodiment of the present invention: For the shield starting construction of a certain section in a certain project, the tunnel of this section passes through a water-rich soft soil stratum with a high confined water head, and the conventional reinforcement method is difficult to meet the safety starting requirements. The construction method provided by the present invention is adopted for shield starting.

[0038] First, conduct the design of ground freezing reinforcement. According to the tunnel structure size, determine that the cross-sectional range of the freezing curtain 1 is 2m outside the outer contour of the tunnel structure, and the longitudinal length along the line is 4m. The designed average temperature of the freezing curtain 1 is not higher than -10°C, and the average temperature at the junction of the freezing curtain 1 and the diaphragm wall is not higher than -5°C.

[0039] The construction of the freezing holes 3 is positioned strictly according to the design drawings. The freezing pipes are 20# low-carbon seamless steel pipes with a diameter of 89mm. After being lowered, pressure testing for leakage is carried out. The test pressure is not less than 0.8MPa, and it is qualified if the pressure drop does not exceed 0.05MPa after stabilizing for 30 minutes. After the construction of the freezing holes 3 is completed, the drilling deviation measurement is carried out to ensure that the final hole spacing is controlled within 1.2m.

[0040] The freezing station is located between the left and right lines, and is equipped with refrigeration units, brine pumps, cooling towers, and other equipment. The active freezing time is controlled to be more than 35 days, and the flow rate of freezing hole 3 is controlled at 5-7 m³ / h. After 7 days of active freezing, the brine temperature drops to below -18℃, after 15 days it drops to below -24℃, and before the tunnel entrance is removed, the brine temperature drops to below -28℃.

[0041] After the construction of the freezing hole 3 is completed, the external steel box 7 and the double-layer curtain are installed. First, the first layer of curtain rubber plate 6 is installed on the pre-embedded steel ring 5 at the tunnel entrance, and fixed with hinged pressure plates and M20 bolts. Then, the segmented external steel box 7 is hoisted into place, with adjacent segments connected by M20 bolts. The contact surface between the steel box and the pre-embedded steel ring 5 is completely sealed by welding. Finally, the second layer of curtain rubber plate 8 is installed on the outside of the steel box, and fixed with hinged pressure plates and bolts as well.

[0042] After confirming that the thickness of the frozen curtain 1 reaches more than 3m and the average temperature is below -10℃ based on the monitoring data from temperature measuring hole 4, 3-5 exploratory boreholes are drilled within the portal area to further verify the sealing and strength of the frozen curtain 1. After the exploratory boreholes pass verification, they are sealed and insulated, and then the underground diaphragm wall within the portal area is removed.

[0043] The tunnel boring machine (TBM) begins its operation, with the cutterhead entering the tunnel portal and passing sequentially through the second rubber curtain plate 8, the external steel box 7, and the first rubber curtain plate 6. The double rubber curtain plates are tightly fitted to the TBM's outer shell, effectively preventing mud and water leakage. After the TBM passes through, grout is injected into the steel box through grouting holes to ensure a long-term seal.

[0044] All four starting portals of the project successfully launched the tunnel boring machine safely and without any accidents, verifying the reliability and superiority of this construction method.

[0045] The method described in this invention comprehensively utilizes multiple measures, including horizontal freezing reinforcement, an external steel box 7, and double-layer curtain fabric. Freezing reinforcement forms a temporary support structure to block groundwater, the external steel box 7 provides rigid support to enhance stability, and the double-layer curtain fabric achieves dynamic sealing. These three elements work together to form a complete safety assurance system. Enhanced waterproofing: The combined design of the external steel box 7 and the double-layer curtain fabric provides both rigid protection and flexible sealing. The double-layer curtain fabric tightly adheres to the shield machine's outer shell when the tunnel boring machine passes, effectively preventing mud and water leakage and solving the problem of easy failure of traditional single-seal structures. Strong construction adaptability: This method is suitable for high water pressure, water-rich soft soil strata, especially for locations with confined water. It requires no large-scale ground reinforcement or pipeline relocation, offering high construction flexibility and minimal impact on the surrounding environment. Economical and efficient: Compared to traditional mixing pile reinforcement or full-ring steel sleeve starting, this method has lower material costs, lower machinery costs, and higher operational efficiency, significantly saving on project costs.

[0046] The above description is merely a preferred embodiment of the present invention and does not limit the scope of the present invention. All equivalent changes made based on the description and drawings of the present invention are included within the scope of the present invention.

Claims

1. A method for shield tunneling initiation at confined water locations in water-rich soft soil strata, characterized in that, Includes the following steps: S1. Design of ground freezing reinforcement: Determine the design range of the freezing curtain, so that the cross-sectional outline of the freezing curtain exceeds the outer outline of the tunnel structure, and form a ring-shaped freezing reinforcement body around the tunnel structure. The freezing curtain extends the design length along the longitudinal direction of the tunnel. S2. Construction of freezing holes: Drill freezing holes at the starting portal. The freezing holes include an outer ring of freezing holes and an inner ring of freezing holes arranged around the tunnel outline. Place freezing pipes in the freezing holes, pressure test the freezing pipes for leaks, and then place liquid supply pipes in the freezing pipes. S3. Installation of the refrigeration station and active freezing: Install the refrigeration unit and connect the brine pipeline. Transport low-temperature brine to the formation through the freezing pipe for active freezing until the thickness of the freezing curtain, the average temperature and the temperature of the interface between the freezing curtain and the underground continuous wall reach the design specifications. S4. Installation of external steel box and double curtain: Install the first curtain rubber plate on the pre-embedded steel ring of the tunnel portal, then install the external steel box on the outside of the first curtain rubber plate, seal the external steel box with the pre-embedded steel ring of the tunnel portal, and then install the second curtain rubber plate on the outside of the steel box to form a double-layer curtain sealing structure. S5. Verification of freezing effect and removal of tunnel portal: After confirming that the frozen curtain has reached the design strength by monitoring data through temperature measurement holes, exploratory holes are drilled within the tunnel portal area to further verify the sealing and strength of the frozen curtain. Subsequently, the underground continuous wall within the tunnel portal area is removed. S6. Shield Launch and Sealing Control: When the shield machine cutterhead enters the tunnel portal, it passes through the second curtain rubber plate, the external steel box, and the first curtain rubber plate in sequence. The double curtain rubber plates seal the gap between the shield machine and the tunnel portal to prevent mud and water from leaking out.

2. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S2, the freezing pipe is made of low-carbon seamless steel pipe. After the freezing pipe is lowered, the pressure for pressure testing and leak detection shall not be less than twice the working pressure of brine, and the pressure drop during the stabilization time shall not exceed the specified range.

3. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S3, the brine temperature is controlled in stages during the active freezing process. In the early stage of freezing, the brine temperature is reduced to below the first temperature threshold. In the middle stage of freezing, the brine temperature is reduced to below the second temperature threshold, which is lower than the first temperature threshold. Before the tunnel entrance is removed, the brine temperature is reduced to below the third temperature threshold, which is lower than the second temperature threshold.

4. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S4, the external steel box is assembled from multiple segmented steel boxes. Adjacent segmented steel boxes are connected by bolts, and the contact surface between the external steel box and the pre-embedded steel ring of the tunnel portal is sealed by welding.

5. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 4, characterized in that: The external steel box has a ring-shaped box structure with internal stiffening ribs. The external steel box is also equipped with grouting holes for injecting filling grout into the steel box when necessary.

6. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S2, after the construction of the freezing holes is completed, the drilling deviation is measured, the final spacing of the freezing holes is controlled within the design range, and additional holes are made in areas where the spacing exceeds the standard.

7. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S5, after drilling the exploratory borehole, the borehole is sealed and the borehole location is insulated to prevent local melting of the frozen curtain.

8. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S4, both the first and second curtain rubber sheets are fixed to the pre-embedded steel ring or external steel box of the tunnel entrance by folding pressure plates and bolts.

9. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to any one of claims 1 to 8, characterized in that: During active freezing, the brine flow rate of the freezing holes is monitored, and the brine flow rate of a single hole is kept at no less than the design flow rate. The temperature difference between the outgoing brine and the return brine is controlled within the design range.

10. The shield tunneling method for launching tunnels at the location of confined water in water-rich soft soil strata according to claim 1, characterized in that: In S6, during the initial launch of the tunnel boring machine, sealing grease or filling slurry is injected into the interior of the steel box through the grouting holes on the external steel box, which is then sealed with the help of double-layered curtain rubber plates.

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