Construction method for building external connecting passages in shield tunnels with overlapping sections

Abstract

This invention relates to a construction method for building an external connecting passage in a shield tunnel with overlapping sections. The specific steps are: 1) determining the main structure, retaining structure form, and related parameters of the shaft to ensure its safety and reliability; 2) drilling freezing holes and analyzing the hole formation after the lower shield tunnel is completed; 3) freezing construction of the lower connecting passage; 4) drilling freezing holes for the upper connecting passage during the freezing period and analyzing the freezing effect; 5) construction of the lower connecting passage and grouting based on monitoring data, while paying attention to deformation coordination and waterproofing; 6) freezing construction of the upper connecting passage; 7) excavation, construction, and grouting of the upper connecting passage. This invention enables the smooth completion of the construction of an external connecting passage in a shield tunnel with overlapping sections, reducing the potential risk of structural damage during construction and providing protection for subway maintenance and disaster prevention.

Description

Technical Field

[0001] This invention relates to a method for constructing a connecting passage, and more particularly to a method for constructing an external connecting passage in a shield tunnel with overlapping tunnels. Background Technology

[0002] With the continuous development of urban underground space, available underground space is becoming increasingly scarce, reducing the options for subway line selection. Under these circumstances, newly built subway lines inevitably tend to be arranged in an overlapping manner. To meet the emergency evacuation needs of subway sections, connecting passages need to be constructed between tunnels, with a spacing of no more than 600 meters. When the overlapping section is long, the connecting passage may be located in the overlapping section. Currently, the technology for constructing external connecting passages in overlapping tunnels in China is still immature, and construction experience is limited. The difficulties and characteristics of this type of construction compared to conventional connecting passages, and the specific measures required, all urgently need to be analyzed, studied, and verified in actual construction.

[0003] During the construction of a subway line in China, an external connecting passage was built at a certain location. A continuous underground wall structure was used for the shaft retaining structure, while the main body of the shaft pit was a cast-in-place concrete frame structure. The external connecting passage was located where the left and right tunnels overlapped vertically, with the left tunnel below and the right tunnel above. The left tunnel traversed strata primarily composed of clay and silt, while the right tunnel traversed strata primarily composed of silty clay. As a high-risk underground project, the connecting passage could easily lead to groundwater and soil erosion if not handled carefully during construction, potentially causing water and sand inrushes, ground collapses, and tunnel damage. Therefore, how to deploy freezing holes to freeze the ground and construct the connecting passage was a crucial issue that required careful consideration.

[0004] The construction of externally mounted overlapping connecting passages involves multiple construction processes, including shafts, tunnels, and connecting passages. During construction, it is necessary to address the mutual disturbance between tunnel and shaft construction, the mutual influence between connecting passages between upper and lower tunnels, and the feasibility and risk accumulation of each spatially integrated process. Determining measures to minimize the mutual influence between these processes is also a key area requiring further research.

[0005] In the case of overlapping tunnels, the external connecting passage is blocked by the upper connecting passage, so it is impossible to analyze the impact of its construction on the soil through surface monitoring. Moreover, the mutual influence of frost heave and thaw settlement between the upper and lower connecting passages cannot be reflected through surface monitoring. Therefore, the monitoring methods and thaw settlement grouting measures to be adopted for the external connecting passage are also a very critical research topic. Summary of the Invention

[0006] The present invention provides a construction method for building an external connecting passage in a shield tunnel with overlapping sections, so as to ensure the smooth construction of the external connecting passage.

[0007] To achieve the above objectives, the technical solution of the present invention is: a construction method for building an external connecting passage in a shield tunnel with overlapping sections, comprising:

[0008] (1) Determine the main structure, enclosure structure form and related parameters of the shaft to ensure its safety and reliability.

[0009] The main structure, retaining structure and related parameters of the shaft are determined according to the construction requirements and relevant specifications to ensure the safety of the shaft during subsequent drilling, freezing and connecting passage construction, while facilitating subsequent construction.

[0010] (2) After the lower shield tunnel is completed, the drilling of freezing holes and hole formation analysis will be carried out.

[0011] The connecting passage uses a two-stage drilling process for freezing hole construction. By adjusting the spacing and pitch angle of the freezing holes, the initial hole position changes but the final hole position remains the same. After the freezing hole construction of the lower tunnel connecting passage is completed, the completed freezing holes are analyzed. If they are not up to standard, supplementary holes should be drilled at the corresponding locations. Only after they are up to standard can subsequent construction be carried out.

[0012] (3) Construction of the underground connecting passage is frozen.

[0013] Starting from the freezing station, brine pipelines are laid to supply liquid to the freezing holes, and freezing construction is carried out on the connecting passage to the lower tunnel.

[0014] (4) Drilling of freezing holes in the upper tunnel connecting passage during the freezing period and analysis of the freezing effect.

[0015] To avoid damage to the frozen wall caused by the mutual influence of frost heave forces between the upper and lower passages, freezing hole drilling will only be carried out on the upper passage connecting the lower passage during the freezing period. After the lower passage connecting the passage has been frozen for the required number of days, the freezing effect will be analyzed to ensure the smooth progress of the subsequent excavation of the connecting passage.

[0016] (5) Construction of the connecting passage to the lower tunnel and grouting

[0017] During the excavation of the connecting passage between the upper and lower tunnels, attention should be paid to deformation coordination and waterproofing. When grouting for thawing settlement, multi-point and layered micro-disturbance grouting should be carried out according to the soil settlement between the upper and lower tunnels and the changes in ground pressure. This will compensate for the thawing settlement of the frozen soil while reducing the disturbance to the surrounding strata. The grouting principle follows the principle of "small amount and multiple times".

[0018] (6) Construction of the upper tunnel connecting passage is frozen.

[0019] Under the premise that the frozen wall of the lower tunnel has been formed to effectively protect the lower tunnel connecting tunnel and ensure construction safety, the upper tunnel connecting tunnel will begin freezing construction during the excavation of the lower tunnel. After the upper tunnel connecting tunnel has been frozen for a certain number of days, the freezing effect will be analyzed.

[0020] (7) Excavation, construction and grouting of the connecting passage to the upper tunnel

[0021] After the excavation and construction of the upper tunnel connecting passage were completed, grouting was carried out on the upper and lower tunnel connecting passages according to the monitoring data.

[0022] Furthermore, in step (1) above, the shaft construction is carried out first. After the main structure of the shaft is completed, the tunnel side-passing shaft construction is carried out to reduce the impact of soil displacement and groundwater seepage that may be caused by the shaft construction.

[0023] Furthermore, in step (1) above, during the construction of the main structure of the connecting passage shaft, in order to facilitate subsequent construction, a reserved opening with the same size as the permanent structure of the connecting passage is set at the location of the connecting passage on the left and right sides of the inner lining wall. This avoids damage to the main structure of the shaft caused by later excavation, protects the integrity of the structure, and relatively reduces the amount of excavation work, thus achieving the goal of saving construction time.

[0024] Furthermore, in step (4) above, the freezing holes are arranged in a divergent pattern toward the tunnel side, and the main side holes are arranged as close as possible to the freezing station and the excavation face.

[0025] Furthermore, in step (5) above, attention should be paid to deformation coordination during construction. The problem of deformation incoordination during construction can be further addressed by setting up expansion joints at the interface and reserved connectors in the shaft.

[0026] Furthermore, in step (5) above, the construction process adopts the method of steel pipe segments plus waterstop plates to ensure the water tightness requirements at the connection between the connecting passage and the tunnel.

[0027] Furthermore, in step (5) above, multi-point, layered micro-disturbance grouting is carried out based on the soil settlement and changes in ground pressure. Since the lower tunnel connecting passage is blocked by the upper tunnel connecting passage, it is impossible to analyze the impact of its construction on the soil through surface monitoring. Therefore, in addition to conventional surface, tunnel, and passage monitoring, soil settlement monitoring is also required between the upper and lower tunnels.

[0028] Furthermore, in step (5) above, the excavation of the connecting passage adopts the method of reducing the excavation step distance. Every 0.5m of excavation advance, steel grid is immediately erected for initial lining concrete spraying, and the process connection is well done. Ultra-early strength and fast hard concrete is used to form the initial support strength as soon as possible. While ensuring the safety of the passage excavation, the disturbance of the excavation construction to the overlapping connecting passage is reduced.

[0029] Furthermore, in step (5) above, during the excavation of the lower tunnel, earth pressure sensors are installed above the lower tunnel to monitor the compression of the soil by frost heave, thaw settlement grouting, etc., and thus control the thaw settlement grouting.

[0030] The beneficial effects of this invention are:

[0031] The method of this invention ensures the safety and reliability of the shaft by determining its structural form, thus guaranteeing the smooth progress of subsequent drilling and tunnel excavation. It also ensures the construction quality of the freezing holes through borehole analysis. The freezing construction of the lower tunnel connecting passage stabilizes the surrounding strata. Drilling of the upper tunnel during the freezing of the lower tunnel and analyzing the freezing effect prevents the mutual influence of frost heave forces between the two passages from causing damage to the frozen walls, while further ensuring the stability of the strata during the excavation of the connecting passage. Melting and settling grouting reduces the impact of early construction on the tunnel structure and strata. Freezing the upper tunnel during the excavation of the lower tunnel reduces the mutual influence between construction procedures and saves time. A second melting and settling grouting after the excavation of the lower tunnel connecting passage further ensures the safety of the entire structure and reduces the potential risks associated with the connecting passage.

[0032] The construction method involved in this invention enables the smooth construction of external connecting passages in shield tunnels with overlapping tunnels, reduces the potential risk of structural damage during construction, and provides a guarantee for subway maintenance and disaster prevention. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the layout of overlapping tunnels, overlapping connecting passages, and vertical shafts;

[0034] Figure 2 This is a schematic cross-sectional view of the layout of overlapping tunnels, overlapping connecting passages, and vertical shafts.

[0035] Figure 3 This is a plan view of the freezing holes in the connecting passage;

[0036] Figure 4 This is a perspective view of the freezing holes in the left and right connecting passages.

[0037] Figure 5 This is a schematic diagram of the structural form of the connection between the connecting passage and the vertical shaft;

[0038] Figure 6 This is a schematic diagram showing the waterproofing at the connection between the connecting passage and the tunnel;

[0039] Figure 7 This is a schematic diagram of the waterproofing at the connection between the connecting passage and the shaft;

[0040] Figure 8 This is a schematic diagram of the layout of deep monitoring holes on both sides of the connecting channel;

[0041] Figure 9 This is a schematic diagram of the layout of deep monitoring points on both sides of the connecting channel;

[0042] In the diagram: 1-Shaft; 2-Upper tunnel connecting passage; 3-Lower tunnel connecting passage; 4-Diaphragm wall; 5-Concrete frame structure; 6-Freezing hole; 7-Connector; 8-Connecting passage structural layer; 9-Shaft inner lining wall; 10-Expansion joint; 11-Steel edge waterstop; 12-Self-adhesive membrane; 13-Steel pipe segment; 14-Waterstop steel plate; 15-Water-swellable caulking adhesive; 16-Water-swellable rubber strip; 17-Connecting passage support layer; 18-Grouting pipe; 19-Monitoring hole; 20-Deep monitoring point. Detailed Implementation

[0043] The invention will be further illustrated below with specific implementation examples.

[0044] A section of the Tianjin subway line initially started from the starting station with parallel shield tunnel sections. The right-line section then ascended, while the left-line section descended, gradually creating an overlapping relationship between the shield tunnel sections. At a point where the shield tunnels overlapped, an external connecting passage was constructed—a connecting passage excavated to one side of the tunnel, connecting to the surface via a vertical shaft. The shaft's retaining structure uses diaphragm walls, with the main body being a cast-in-place concrete frame structure.

[0045] The external connecting passage is located where the left and right tunnels overlap vertically, with the left tunnel below and the right tunnel above. The strata traversed by the left connecting passage are mainly clay and silt, while the strata traversed by the right connecting passage are mainly silty clay.

[0046] like Figures 1-9 As shown, the construction method of the present invention can meet the construction requirements for building external connecting passages in shield tunnels with overlapping tunnels.

[0047] This invention mainly includes the following aspects:

[0048] (1) Construct the main structure of the vertical shaft

[0049] like Figures 1-2 As shown, the main structure, retaining structure form and related parameters of shaft 1 are determined according to the construction requirements and relevant specifications to ensure the safety of shaft 1 during subsequent drilling and freezing, construction of upper tunnel connecting passage 2 and lower tunnel connecting passage 3, and to facilitate subsequent construction.

[0050] The shaft retaining structure adopts underground continuous wall 4, and the main body of the shaft pit is a cast-in-place concrete frame structure 5.

[0051] (2) Drilling construction and hole formation analysis of frozen holes

[0052] The lower tunnel connecting passage 3 employs a two-stage drilling process for the drilling of freezing holes 6. By adjusting the spacing and elevation angle of the freezing holes, the initial position of the freezing holes changes while the final position remains constant. After the freezing hole construction of the lower tunnel connecting passage 3 is completed, the drilled freezing holes 6 are analyzed. If they are found to be substandard, supplementary holes should be drilled at the corresponding locations. Only after passing the analysis can subsequent construction proceed.

[0053] like Figures 3-4 As shown, the freezing holes 6 are arranged at three angles: upward, horizontal, and downward. Multiple through holes are provided for use by the freezing holes 6 on the opposite side of the tunnel and the freezing pipes. In addition, freezing pipes are laid along the freezing wall of the tunnel at the freezing station to enhance the insulation effect at the tunnel segments.

[0054] (3) Construction of the underground connecting passage is frozen.

[0055] Starting from the freezing station, a brine pipeline is laid to supply liquid to the freezing hole 6, and freezing construction is carried out on the lower tunnel connecting passage 3.

[0056] Before the lower tunnel is completed, the freezing station will be installed at the site of the shaft 1 opening. Two brine pipelines will be laid from the ground to supply liquid to the left and right channels respectively. This will not only facilitate the daily maintenance of the freezing station and save project costs, but also achieve the goal of saving construction time.

[0057] (4) Drilling of freezing holes in the upper tunnel connecting passage during the freezing period and analysis of the freezing effect on the lower tunnel connecting passage.

[0058] To avoid damage to the frozen walls caused by the mutual influence of frost heave forces between the upper and lower passages, only the upper passage will be drilled for freezing hole 6 during the freezing period of the lower passage connecting the tunnel. After the freezing period of the lower passage connecting the tunnel 3 is completed, the freezing effect will be analyzed to ensure the smooth progress of the subsequent excavation of the lower passage connecting the tunnel.

[0059] (5) Construction of the connecting passage to the lower tunnel and grouting

[0060] Reasonable construction techniques were adopted for the excavation of the lower tunnel connecting passage 3. During construction, attention was paid to deformation monitoring, deformation coordination, and waterproofing. During thawing grouting, multi-point, layered micro-disturbance grouting was carried out according to the soil settlement between the upper and lower tunnels and the changes in ground pressure. This compensated for the thawing settlement of the frozen soil while reducing the disturbance to the surrounding strata. The grouting principle followed the principle of "small amount, multiple times".

[0061] like Figure 5As shown, the primary lining reinforcement of the connecting passage is connected to the diaphragm wall of the shaft via a pre-installed connector 7 on the diaphragm wall. The reinforcement of the structural layer 8 of the connecting passage is connected to the inner lining wall 9 of the shaft via a pre-installed connector 7 on the inner lining. A vertical expansion joint 10 is provided in the middle of the diaphragm wall 4 in the structural layer 8 of the connecting passage. At the expansion joint 10, the longitudinal main reinforcement of the secondary lining 8 of the connecting passage is broken, and a steel edge waterstop 11 is set in the middle with M-shaped reinforcement on both sides. The expansion joint 10 is set at the connection between the connecting passage and the shaft, mainly to address the potential problem of structural cracking of the connecting passage caused by the incoordination of settlement deformation between the shaft 1 and the tunnel. It provides a place for stress and deformation release in the connecting passage. The deformation is set within the range of the diaphragm wall, which can also constrain the amount of deformation and prevent excessive deformation from damaging the connecting passage structure.

[0062] like Figure 6 As shown, the external connecting passage uses self-adhesive waterproof membrane 12. To prevent leakage, a water-stop steel plate 14 is welded to the back of the steel pipe segment 13 adjacent to the opening at the connection between the connecting passage and the tunnel, forming a closed ring. Simultaneously, water-swellable sealant 15 is added to both sides of the weld joint at the junction of the steel pipe segment 13 and the water-stop steel plate 14. The water-stop steel plate 14 is fabricated on-site according to the design drawings to ensure the watertightness of the weld joint.

[0063] Secondly, as Figure 7 As shown, there is a construction cold joint at the connection between the passage and the inner lining wall of the shaft. To prevent leakage, during construction, a water-stop steel plate 14 is welded and sealed into a ring within the secondary lining area of ​​the inner lining wall 9 using a rebar anchoring method. The water-stop steel plate 14 is made of galvanized steel plate and is fabricated on-site according to the design drawings. To ensure the water-stopping effect, water-swellable sealant 15 is applied to the joint between the water-stop steel plate 14 and the inner lining wall 9, and a mortar chamfer is made. A ring of water-swellable rubber strips 16 is placed on each side of the water-stop steel plate 14, and a ring of full-section grouting pipes 18 is placed between the water-stop steel plate 14 and the water-swellable rubber strips 16 on the side near the support layer 17 of the connecting passage. The waterproof membrane 12 of the passage section overlaps with the waterproof membrane of the inner lining wall 9.

[0064] like Figures 8-9 As shown, a deep monitoring borehole 19 is set on each side of the connecting passage (outside the frozen curtain area). Each borehole uses a vibrating wire sensor with three vertically arranged measuring points 20, located at areas of soil significantly affected by the construction of the upper connecting passage 2, areas significantly affected by the construction of the lower connecting passage 3, and areas affected by both connecting passages. This allows for a more intuitive analysis of the impact of freezing, excavation, thawing, and grouting processes on the soil layer.

[0065] (6) Construction of the upper tunnel connecting passage is frozen.

[0066] With the frozen wall of the lower tunnel connecting passage 3 already formed, effectively protecting it and ensuring construction safety, the upper tunnel connecting passage 2 began freezing construction during the excavation of the lower tunnel connecting passage 3. After the required number of days of freezing for the upper tunnel connecting passage 2 were reached, the freezing effect was analyzed.

[0067] (7) Excavation, construction and grouting of the connecting passage to the upper tunnel

[0068] After the excavation and construction of the upper tunnel connecting passage 2 were completed, grouting was carried out on the upper tunnel connecting passage 2 and the lower tunnel connecting passage 3 according to the monitoring data.

Claims

1. A construction method for building an external connecting passage in a shield tunnel with overlapping sections, characterized in that, The specific steps are as follows: (1) Determine the main structure, enclosure structure form and related parameters of the shaft to ensure the safety and reliability of the shaft. The main structure, retaining structure and related parameters of the shaft are determined according to the construction requirements and relevant specifications to ensure the safety of the shaft during subsequent drilling, freezing and connecting passage construction, while facilitating subsequent construction. (2) After the lower shield tunnel is completed, the drilling of freezing holes and hole formation analysis are carried out. The connecting passage adopts a two-stage drilling process for freezing hole construction. By adjusting the spacing and pitch angle of the freezing holes, the initial hole position of the freezing hole changes but the final hole position remains unchanged. After the freezing hole construction of the lower tunnel connecting passage is completed, the completed freezing holes are analyzed. If they are not up to standard, supplementary holes should be drilled at the corresponding locations. Only after they are up to standard can subsequent construction be carried out. (3) Construction of the underground connecting passage is frozen. Starting from the freezing station, a brine pipeline is laid to supply liquid to the freezing holes, and freezing construction is carried out on the connecting passage to the lower tunnel. (4) Drilling of freezing holes in the tunnel connecting passage during the freezing period and analysis of the freezing effect. To avoid damage to the frozen wall caused by the mutual influence of frost heave forces between the upper and lower passages, freezing hole drilling will only be carried out on the upper passage during the freezing period of the lower passage. After the lower passage has been frozen for the required number of days, the freezing effect will be analyzed to ensure the smooth progress of the subsequent excavation of the connecting passage. (5) Construction of the connecting passage to the lower tunnel and grouting for settling During the excavation of the connecting passage between the upper and lower tunnels, attention should be paid to deformation monitoring, deformation coordination, and waterproofing. During thaw settlement grouting, multi-point, layered micro-disturbance thaw settlement grouting should be carried out according to the soil settlement and ground pressure changes between the upper and lower tunnels to compensate for the thawing settlement of frozen soil while reducing the disturbance to the surrounding strata. The grouting principle follows the principle of "small amount, multiple times". During the construction process, attention should be paid to deformation coordination. The problem of deformation incoordination during construction is further addressed by setting up expansion joints at the interface and reserved connectors in the vertical shaft. During the excavation of the lower tunnel, earth pressure sensors are installed above the lower tunnel to monitor the compression of the soil by frost heave and thaw settlement grouting, thereby controlling the thaw settlement grouting. (6) Construction of the connecting passage between the upper tunnels is underway. The frozen wall of the lower tunnel has been formed, which can effectively protect the lower tunnel connecting tunnel. Under the premise of ensuring construction safety, the upper tunnel connecting tunnel will begin freezing construction during the excavation of the lower tunnel. After the upper tunnel connecting tunnel has been frozen for a certain number of days, the freezing effect will be analyzed. (7) Excavation, construction and grouting of the connecting passage to the upper tunnel After the excavation and construction of the upper tunnel connecting passage were completed, grouting was carried out on the upper and lower tunnel connecting passages according to the monitoring data.

2. The construction method for constructing an external connecting passage in a shield tunnel with overlapping sections according to claim 1, characterized in that: In step (1) above, the shaft construction is carried out first. After the main structure of the shaft is completed, the tunnel side-passing shaft construction is carried out to reduce the impact of soil displacement and groundwater seepage that may be caused by the shaft construction.

3. The construction method for constructing an external connecting passage in a shield tunnel with overlapping sections according to claim 1, characterized in that: In step (1) above, during the construction of the main structure of the connecting passage shaft, in order to facilitate subsequent construction, a reserved opening with the same size as the permanent structure of the connecting passage is set at the location of the connecting passage on the left and right sides of the inner lining wall. This avoids damage to the main structure of the shaft caused by later excavation, protects the integrity of the structure, and relatively reduces the amount of excavation work, thus achieving the goal of saving construction time.

4. The construction method for constructing an external connecting passage in a shield tunnel with overlapping sections according to claim 1, characterized in that: In step (4) above, the freezing holes are arranged in a divergent pattern toward the tunnel side, and the main side holes are arranged as close as possible to the freezing station and the excavation face.

5. The construction method for constructing an external connecting passage in a shield tunnel with overlapping sections according to claim 1, characterized in that: In step (5) above, the construction process adopts the method of steel pipe segments plus waterstop plates to ensure the water tightness requirements of the connection between the connecting passage and the tunnel.

6. The construction method for constructing an external connecting passage in a shield tunnel with overlapping sections according to claim 1, characterized in that: In step (5) above, multi-point, layered micro-disturbance grouting is carried out based on the soil settlement and changes in ground pressure. Since the lower tunnel connecting passage is blocked by the upper tunnel connecting passage, it is impossible to analyze the impact of its construction on the soil through surface monitoring. Therefore, in addition to conventional surface, tunnel, and passage monitoring, soil settlement monitoring is also required between the upper and lower tunnels.

7. The construction method for constructing an external connecting passage in a shield tunnel with overlapping sections according to claim 1, characterized in that: In step (5) above, the excavation of the connecting passage adopts the method of reducing the excavation step distance. Steel grid is immediately erected for initial lining concrete spraying after every 0.5m of excavation. The process is well connected, and ultra-early strength and fast hard concrete is used to form the initial support strength as soon as possible. While ensuring the safety of the passage excavation, the disturbance of the excavation construction to the overlapping connecting passage is reduced.

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