Urban shallow-buried spiral tunnel

Abstract

The utility model relates to an urban shallow-buried spiral tunnel, and belongs to the field of tunnel engineering. The spiral tunnel is used for communicating the main channel tunnel and the functional tunnel on different horizontal planes; comprising a spiral double-arch tunnel, one end of the double-arch tunnel is a portal, and the other end of the double-arch tunnel is communicated with a main channel tunnel through a single-arch tunnel; the double-arch tunnel comprises an arc-shaped section and a linear section, and a construction channel communicated with the functional tunnel is arranged on the linear section; the double-arch tunnel comprises a front hole, a rear hole and a middle pilot tunnel, the front hole and the rear hole respectively comprise two pilot tunnels, one pilot tunnel is divided into an upper step and a lower step according to an excavation sequence, and the middle pilot tunnel comprises two pilot tunnels and a middle partition wall. According to the spiral tunnel, the problem that construction is inconvenient due to the complex geographical environment or urban planning space limitation is solved, and the spiral tunnel is safer and more reliable; and surrounding rock disturbance can be reduced to the maximum extent, the influence on the surrounding environment is reduced, and the safety of urban tunnel construction is improved.

Description

Technical Field

[0001] The utility model belongs to the field of tunnel engineering and relates to a shallow buried spiral tunnel in an urban area. Background Art

[0002] In the construction of tunnels in some cities, due to the dense surface buildings, the influence of tunnel construction on the settlement and deformation of the surface and buildings is more significant, which may cause greater disturbance to the strata and cause surface movement, which is easy to cause great impact and damage to the surface engineering structure and the surrounding environment. In order to reduce the impact on existing buildings and ensure construction safety and building stability, tunnel design may tend to choose a shallower burial depth to better control the stratum deformation during construction; secondly, the urban underground space planning is dense, the geological conditions are complex, and the bearing capacity of the strata varies greatly. The burial depth of the tunnel is limited by the existing underground facilities, and in order to ensure the stability of the tunnel and construction safety, a shallower burial depth has to be chosen. The urban groundwater level is high and the groundwater flow is active. The shallower burial depth may make the tunnel construction more susceptible to the influence of groundwater, such as seepage and water inrush. Therefore, the influence of the above factors needs to be considered in the design and construction. However, a shallower burial depth may increase the difficulty of construction and have high requirements for construction technology, such as more sophisticated excavation and support measures, stricter deformation control, etc.

[0003] In addition, in urban tunnel projects, due to the space limitations of urban planning, it is difficult for the main channel tunnel and other functional tunnels (such as power tunnels) to be on the same level, which brings great difficulties to the design, planning, and construction of the tunnel project.

[0004] In order to solve the above technical problems, it is urgent to propose a tunnel structure suitable for urban built-up areas to reduce the disturbance of the surrounding rock and reduce the impact on the surrounding environment. Utility Model Content

[0005] In view of this, the purpose of the utility model is to provide an urban shallow-buried spiral tunnel, which connects the main channel tunnel with other functional tunnels on different horizontal planes, and can reduce the disturbance of the surrounding rock and reduce the impact on the surrounding environment.

[0006] In order to achieve the above object, the utility model provides the following technical solutions:

[0007] A shallow urban spiral tunnel is used to connect a main channel tunnel and a functional tunnel at different levels; it comprises a spiral double-arch tunnel, one end of the double-arch tunnel is a cave entrance, and the other end is connected to the main channel tunnel through a single-arch tunnel; the double-arch tunnel comprises an arc segment and a straight segment, and a construction channel connected to the functional tunnel is arranged on the straight segment; the double-arch tunnel is wrapped with a supporting structure.

[0008] Optionally, the double-arch tunnel includes a leading tunnel and a rear tunnel arranged side by side, and a middle guide tunnel arranged between the leading tunnel and the rear tunnel; the leading tunnel is located on the outside of the spiral, and the rear tunnel is located on the inside of the spiral, and the two are arranged in mirror image.

[0009] Optionally, the leading tunnel includes a first guide pit and a second guide pit arranged side by side along the direction of the tunnel, wherein the second guide pit is arranged on a side close to the middle guide tunnel; the rear tunnel includes a third guide pit and a fourth guide pit arranged side by side along the direction of the tunnel, wherein the third guide pit is arranged on a side close to the middle guide tunnel.

[0010] Optionally, the middle guide tunnel includes a middle partition wall and a fifth guide pit and a sixth guide pit arranged on both sides of the middle partition wall, and the fifth guide pit and the sixth guide pit are respectively located in the overlapping parts of the middle guide tunnel and the leading tunnel and the rear tunnel; during the construction process, temporary supports are arranged in the fifth guide pit and the sixth guide pit.

[0011] Optionally, the temporary support is steel bars, and the setting direction of the steel bars is perpendicular to the direction of the tunnel.

[0012] Optionally, the temporary support is a steel pipe, the steel bars are arranged in a direction perpendicular to the direction of the tunnel, the diameter of the steel bars is 105 to 110 mm, and the interval between adjacent steel pipes is 48 cm to 52 cm.

[0013] Optionally, the temporary support is an alternating arrangement of concrete layers and crushed stone layers.

[0014] Optionally, the thickness of the concrete layer and the crushed stone layer are 48 cm to 52 cm respectively.

[0015] Optionally, the bottoms of the fifth guide pit and the sixth guide pit are respectively provided with resistance to backfilling.

[0016] Optionally, the middle partition wall is a curved wall with recessed sides.

[0017] The beneficial effects of the utility model are:

[0018] The shallowly buried spiral tunnel of the utility model connects the main channel tunnel and the functional tunnel on different horizontal planes, thus solving the problem of construction inconvenience caused by complex geographical environment or space limitation of urban planning. In addition, the double-arch tunnel is connected with the main channel through a single-arch tunnel, which can adapt to geographical environment with more complex geological conditions or more stringent space limitation, and is safer and more reliable.

[0019] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and will be apparent to those skilled in the art based on the following examination and research, or can be taught from the practice of the present invention to some extent. The objectives and other advantages of the present invention can be achieved and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be described in detail below in conjunction with the accompanying drawings, in which:

[0021] Figure 1 This is the plan view of the spiral tunnel;

[0022] Figure 2 This is a cross-sectional view of a double-arch tunnel;

[0023] Figure 3 This is the cross-section of the middle pilot tunnel;

[0024] Figure 4 This is a plan view of the construction process of the double-arch tunnel.

[0025] Reference numerals:

[0026] 1 Main channel tunnel, 2 Double-arch tunnel, 21 Tunnel entrance, 22 Arc section, 23 Straight section, 24 Lead tunnel, 241 First pilot pit, 242 Second pilot pit, 25 Rear tunnel, 251 Third pilot pit, 252 Fourth pilot pit, 253 Upper step, 254 Lower step, 26 Middle pilot tunnel, 261 Middle partition wall, 262 Fifth pilot pit, 263 Sixth pilot pit, 264 Temporary support, 2641 Steel pipe, 2642 Concrete layer, 2643 Gravel layer, 265 Resistance backfill, 3 Single-arch tunnel, 4 Construction channel, 5 Secondary lining, 6 Support structure. DETAILED DESCRIPTION

[0027] The following describes the implementation of the present invention through specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner. The following embodiments and the features in the embodiments can be combined with each other without conflict.

[0028] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present utility model. In order to better illustrate the embodiments of the present utility model, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0029] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0030] See also Figure 1 to Figure 4 , is a shallow urban spiral tunnel, used to connect the main channel tunnel 1 and the functional tunnel at different levels; including a spiral double-arch tunnel 2, one end of the double-arch tunnel 2 is a cave entrance 21, and the other end is connected to the main channel through a single-arch tunnel 3; the double-arch tunnel 2 includes an arc segment 22 and a straight segment 23, and the straight segment 23 is provided with a construction channel 4 connected to the functional tunnel, and the double-arch tunnel 2 is wrapped with a supporting structure 6. In some embodiments of the utility model, the functional tunnel is a power tunnel. Figure 1 The section from K0+60 to K0+700 is double-arch tunnel 2, and the section from K0+05 to K0+60 is single-arch tunnel 3.

[0031] The double-arch tunnel 2 includes two main tunnels arranged side by side, namely a leading tunnel 24 and a rear tunnel 25, and also includes a middle guide tunnel 26 arranged between the leading tunnel 24 and the rear tunnel 25; the leading tunnel 24 is located on the outside of the spiral, and the rear tunnel 25 is located on the inside of the spiral, and the two are arranged in mirror image.

[0032] The leading tunnel 24 includes a first guide pit 241 and a second guide pit 242 arranged side by side along the direction of the tunnel, wherein the second guide pit 242 is arranged on the side close to the middle guide tunnel 26; the rear tunnel 25 includes a third guide pit 251 and a fourth guide pit 252 arranged side by side along the direction of the tunnel, wherein the third guide pit 251 is arranged on the side close to the middle guide tunnel 26.

[0033] The middle guide tunnel 26 includes a middle partition wall 261 and a fifth guide pit 262 and a sixth guide pit 263 arranged on both sides of the middle partition wall 261. The middle partition wall 261 is a double-sided concave arc wall. The fifth guide pit 262 and the sixth guide pit 263 are respectively located at the overlapping part of the middle guide tunnel 26 and the leading tunnel 24 and the trailing tunnel 25. The bottom of the fifth guide pit 262 and the sixth guide pit 263 are respectively provided with a resistance backfill 265, and the backfill material is the excavated ballast soil. On the one hand, it is effectively utilized, and on the other hand, it also avoids the burden of the transportation of ballast soil on the surrounding road traffic during the construction of the urban tunnel. During the construction process, temporary supports 264 are arranged in the fifth guide pit 262 and the sixth guide pit 263. The temporary supports 264 can be removed after the corresponding guide pit's face is advanced by at least 15m.

[0034] Temporary support 264 includes two schemes. When implemented on site, the appropriate scheme is selected according to the actual situation. The first scheme is that temporary support 264 adopts steel pipe 2641 and / or steel bar, and the setting direction of steel pipe 2641 and steel bar is perpendicular to the direction of tunnel; the diameter of steel pipe 2641 is 105-110mm, and the interval between adjacent steel pipes 2641 is 48cm-52cm. In some embodiments of the utility model, the diameter of steel pipe 2641 is preferably 108mm, and the interval between adjacent steel pipes 2641 is 50cm. The second scheme is that temporary support 264 adopts the form of interlayer backfill of concrete layer 2642 and gravel layer 2643; the thickness of concrete layer 2642 and gravel layer 2643 are 48cm-52cm respectively. In some embodiments of the utility model, the thickness of concrete layer 2642 and gravel layer 2643 is preferably 50cm.

[0035] The utility model connects the double-arch tunnel 2 with the main channel through the single-arch tunnel 3, rather than directly connecting the double-arch tunnel 2 with the main channel, in order to adapt to complex geological conditions, especially due to urban planning and space restrictions. In areas with extremely complex geological conditions, gradually approaching the main channel through the single-arch tunnel 3 and adapting to geological changes may be safer and more reliable than directly excavating the double-arch tunnel 2 to connect with the main channel; and directly excavating the double-arch tunnel 2 may be subject to space restrictions, while connecting through the single-arch tunnel 3 can more effectively utilize space resources; it is also conducive to cost control. Although connecting through the single-arch tunnel 3 may increase some additional construction costs (such as the construction cost of the single-arch tunnel 3), in some cases, these costs may be controlled or reduced by optimizing the construction plan, reducing construction risks, etc. For example, geological exploration through the single-arch tunnel 3 can reduce the uncertainty of later construction, thereby reducing the additional costs caused by geological problems and improving the overall benefits of the project.

[0036] A construction method for an urban shallow buried spiral tunnel, used for constructing any of the above-mentioned urban shallow buried spiral tunnels, adopts a dark excavation method, and comprises the following steps:

[0037] S1, construction of double-arch tunnel 2;

[0038] S2, excavating a construction channel 4, and then constructing a functional tunnel (a power tunnel in some embodiments of the present invention) through the construction channel 4;

[0039] S3, after the functional tunnel is completed, the double sidewall pilot method is used to start the construction of the single arch tunnel 3, and the initial support and secondary lining 5 are completed in time;

[0040] Among them, in step S1, the double-arch tunnel 2 is excavated by the single side wall pilot pit method, and the excavation sequence is: start excavation from the end of the double-arch tunnel 2 far away from the single-arch tunnel 3, and excavate the middle guide tunnel 26 and the first pilot pit 241 simultaneously; after the middle guide tunnel 26 and the first pilot pit 241 are excavated for at least 15m, then excavate the fourth pilot pit 252 of the rear tunnel 25, and simultaneously advance the middle guide tunnel 26, the first pilot pit 241 and the fourth pilot pit 252 and apply initial support; construct a middle partition wall 261 from the inside of the middle guide tunnel 26 to the outside of the tunnel, and excavate from the first pilot pit 241 to the middle guide tunnel 26 until it is opened, and use the passage between the middle guide tunnel 26 and the first pilot pit 241 as a temporary passage 27 for excavating the middle guide tunnel 26; After the partition wall 261 is constructed, the second pilot pit 242 is excavated, and the third pilot pit 251 is excavated after a step interval of at least 15m, and then the second pilot pit 242 and the third pilot pit 251 are simultaneously advanced, and it is ensured that during the advancement process, the second pilot pit 242 and the third pilot pit 251 are always separated by a step interval of at least 15m; the second pilot pit 242 and the third pilot pit 251 are respectively divided into an upper step 253 and a lower step 254. When the tunnel is excavated, the upper step 253 is excavated first and then the lower step 254 is excavated, and the excavation sequence of the upper step 253 and the lower step 254 is at least 15m apart; after the excavation of the middle guide tunnel 26, each pilot pit and each step is completed, initial support is promptly applied, and then secondary lining 5 is applied after an interval of at least 90m.

[0041] Due to the influence of the environment in the tunnel, such as high dust content, narrow space and poor ventilation, the provision of a temporary passage 27 can increase the tunnel oxygen supply management to avoid serious harm to the health of the workers due to lack of oxygen.

[0042] The initial support adopts the form of anchor rods and steel arch frames, wherein the length of the side wall anchor rods is 3.0m to 1.5m, the length of the arch anchor rods is recommended to be 4.0 to 2.5m, and the spacing of the steel arch frames is 0.75m to 1.5m. According to simulation calculations, when the anchor rod length changes within this range, the surrounding rock displacement, the initial support internal force, and the axial force of the anchor rods and anchor cables change very little. In some embodiments of the utility model, the anchor rod length is preferably 1.5m, the anchor rod spacing is preferably 1.2m, and the steel arch frame spacing is preferably 0.8m.

[0043] When constructing the leading tunnel 24, it is necessary to backfill or reinforce the rear tunnel 25 on the side close to the middle partition wall 261 to prevent overturning.

[0044] During the construction process, real-time monitoring points are arranged on the surrounding rock to monitor the vertical and horizontal displacements of the surrounding rock and observe the impact of the construction step on the displacement release of the heading face during spiral tunnel construction, so as to adjust the excavation step in time according to the monitoring conditions and reduce the excavation risk.

[0045] The main difficulty of urban spiral tunnel engineering lies in the appropriate construction steps and excavation sequence. The construction sequence of the utility model is determined by establishing a model for simulation calculation, so as to suppress the influence between the successive tunnels to the greatest extent, control the deformation of the tunnel, and make the tunnel more stable.

[0046] The process of establishing a finite element model for simulation calculation is as follows:

[0047] First, four construction sequence conditions were determined: Condition 1 is "excavating the spiral tunnel first, then the power tunnel, and finally the main channel", Condition 2 is "excavating the power tunnel first, then the spiral tunnel, and finally the main channel", Condition 3 is "excavating the power tunnel first, then the main channel, and finally the spiral tunnel", and Condition 4 is "excavating the main channel first, then the power tunnel, and finally the spiral tunnel". Then, finite element models were established respectively, and numerical simulation methods were used to simulate and calculate the four excavation sequence conditions respectively, analyzing the settlement of the stratum and tunnel vault after the tunnel group was excavated, the surrounding rock stress and the initial support stress, and the displacement of the foundation of the surface buildings.

[0048] 1. Deformation comparison analysis

[0049] After the tunnel group was excavated, the maximum settlement and uplift values ​​of the strata were 9.67mm and 8.88mm under the construction sequence of working condition 1, 10.64mm and 9.82mm under working condition 2, 11.86mm and 10.91mm under working condition 3, and 11.46mm and 12.41mm under working condition 4. By comparison, it can be seen that working condition 1 is the best for controlling the vertical displacement of the strata.

[0050] The maximum horizontal displacement of the rock and soil around the tunnel group in working condition 1 is 3.88 mm, 2.30 mm in working condition 2, 2.76 mm in working condition 3, and 3.41 mm in working condition 4. Working condition 1 can better control the horizontal displacement of the stratum than other working conditions.

[0051] The maximum surface settlement in working condition 1 is 5.88 mm, that in working condition 2 is 6.43 mm, that in working condition 3 is 7.64 mm, and that in working condition 4 is 8.46 mm. By comparison, it can be seen that working condition 1 can better control the vertical displacement of the ground surface than other working conditions.

[0052] In working condition one, the maximum settlements of the main channel, spiral tunnel, power tunnel and primary support of the intersection are 6.48mm, 6.49mm, 1.10mm and 7.99mm respectively; in working condition two, they are 7.07mm, 6.83mm, 1.45mm and 8.75mm respectively; in working condition three, they are 7.78mm, 7.10mm, 1.41mm and 10.54mm respectively; in working condition four, they are 8.70mm, 8.15mm, 3.05mm and 11.74mm respectively. By comparison, it can be seen that working condition one can better control the vertical displacement of the main channel, spiral tunnel, power tunnel and primary support of the intersection than other working conditions.

[0053] 2. Stress comparison analysis

[0054] After the tunnel group was excavated, the maximum shear stress appeared on the right side of the lower spiral of the spiral tunnel. The maximum shear stress of working condition 1 was 1.277MPa, working condition 2 was 1.284MPa, working condition 3 was 1.310MPa, and working condition 4 was 1.311MPa. It can be seen that working condition 1 is the best, that is, working condition 1 is the least likely to cause shear failure of surrounding rock among the four working conditions.

[0055] The maximum first principal stress appears in the surrounding rock at the arch bottom where the main channel and the spiral tunnel intersect. The maximum first principal stress value is 0.117MPa in working condition 1, 0.197MPa in working condition 2, 0.198MPa in working condition 3, and 0.349MPa in working condition 4. Comparing the four working conditions, it can be seen that working condition 1 is more stable than other working conditions in terms of tensile failure of the surrounding rock.

[0056] The maximum third principal stress appears on the surrounding rock at the top of the spiral tunnel middle partition wall 261. The maximum compressive stress value is -2.376MPa in working condition 1, -2.404MPa in working condition 2, -2.429MPa in working condition 3, and -2.460MPa in working condition 4. Comparing the four working conditions, it can be seen that working condition 1 is relatively the most stable.

[0057] The maximum compressive stresses of the power tunnel, main channel and spiral tunnel in working condition one are -3.186MPa, -8.135MPa and -10.208MPa respectively; those in working condition two are 3.223MPa, -8.773MPa and -10.873MPa respectively; those in working condition three are -5.711MPa, -11.559MPa and -11.659MPa respectively; those in working condition four are -7.352MPa, -12.057MPa and -12.542MPa respectively. It can be seen that working condition one can better withstand the maximum compressive stress than other working conditions.

[0058] 3. Comparative analysis of plastic zones

[0059] After simulation analysis, the plastic zone volume of working condition one is the smallest, the proportion of surrounding rock reaching plastic yield is smaller, the stress on the tunnel is more reasonable, and it is more conducive to the stability of the tunnel. Therefore, working condition one is selected.

[0060] In summary, the construction sequence of working condition 1 is more advantageous in controlling the development of the plastic zone of the tunnel surrounding rock. It is more advantageous than other excavation sequences in controlling tunnel deformation, with more reasonable force and higher bearing capacity. At the same time, it can control the development of the plastic zone of the surrounding rock to the greatest extent, and the tunnel has higher stability; it can also suppress the influence between the successive tunnels to the greatest extent and control the deformation of the tunnel.

[0061] Through the analysis of displacement, surrounding rock and support structure 6 stress, the excavation sequence of "middle guide tunnel 26, leading tunnel 24, and rear tunnel 25" was selected. This excavation sequence is more conducive to reducing the deformation of the support structure 6 and the surrounding rock, and the stability of the surrounding rock, lining and middle partition wall 261 is higher.

[0062] The analysis process of excavation sequence is as follows:

[0063] The first scheme is defined as "after the excavation of the middle guide tunnel 26, the spiral outer guide tunnel is excavated first, and then the spiral inner guide tunnel is excavated", and the second scheme is "after the excavation of the middle guide tunnel 26, the spiral inner guide tunnel is excavated first, and then the spiral outer guide tunnel is excavated". Through the simulation research and analysis of the two schemes, if the second scheme is adopted, due to the disturbance of the stratum and the release of ground stress after excavation, a settlement trough is formed above the tunnel; under the influence of the grouting anchor reinforcement of the guide tunnels on both sides, the settlement trough is only formed above the middle guide tunnel 26 and biased towards the inner guide tunnel arch. The stratum between the entrance and exit sections of the tunnel is seriously disturbed. After the tunnel construction is completed, the maximum settlement of the arch is about 3.87mm, the maximum uplift of the invert is about 6.57mm, the maximum horizontal displacement of the arch waist is about 1.1mm, and the maximum horizontal displacement of the partition wall is about 0.32mm. If Scheme 1 is adopted, the maximum settlement of the arch after the tunnel construction is completed is about 1.72mm, the maximum uplift of the invert is about 6.43mm, the maximum horizontal displacement of the arch waist is about 1.07mm, and the maximum horizontal displacement of the partition wall is about 0.19mm. In terms of the stress of the surrounding rock and the supporting structure 6, the principal compressive stress of the surrounding rock after construction according to Scheme 1 is 0.14MPa less than that of Scheme 2. There is stress concentration at the top and bottom of the middle partition wall 261, and the stress concentration phenomenon is more obvious when constructing according to Scheme 2. Therefore, Scheme 1 is more conducive to the excavation of the 2nd section of the double-arch tunnel in the spiral tunnel of the utility model.

[0064] During the construction of the double-arch tunnel 2, the surrounding rock stress and lining load frequently transform into each other, which makes the construction very difficult, takes a long time, and has a high construction cost, and is likely to have an adverse effect on the stress of the tunnel structure. Therefore, the single-side wall pilot method is selected and the construction is carried out according to the above construction sequence, which can reduce the construction difficulty, shorten the construction period, and reduce the construction cost.

[0065] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the utility model.

Claims

1. An urban shallow buried spiral tunnel, characterized by: A main channel tunnel (1) and a functional tunnel for connecting different horizontal planes; comprising a spiral double-arch tunnel (2); one end of the double-arch tunnel (2) is a cave opening (21); the other end is connected to the main channel tunnel (1) through a single-arch tunnel (3); the double-arch tunnel (2) comprises an arc segment (22) and a straight segment (23); a construction channel (4) connected to the functional tunnel is arranged on the straight segment (23); and a supporting structure (6) is arranged on the outside of the double-arch tunnel (2).

2. The urban shallow buried spiral tunnel according to claim 1 is characterized by: The double-arch tunnel (2) comprises a leading tunnel (24) and a trailing tunnel (25) arranged side by side, and a middle guide tunnel (26) arranged between the leading tunnel (24) and the trailing tunnel (25); the leading tunnel (24) is located on the outer side of the spiral, and the trailing tunnel (25) is located on the inner side of the spiral, and the two are arranged in a mirror image.

3. The shallow urban spiral tunnel according to claim 2 is characterized by: The leading tunnel (24) comprises a first pilot pit (241) and a second pilot pit (242) arranged side by side along the tunnel direction, wherein the second pilot pit (242) is arranged on a side close to the middle pilot tunnel (26); the trailing tunnel (25) comprises a third pilot pit (251) and a fourth pilot pit (252) arranged side by side along the tunnel direction, wherein the third pilot pit (251) is arranged on a side close to the middle pilot tunnel (26).

4. The shallow urban spiral tunnel according to claim 2 is characterized by: The middle guide hole (26) comprises a middle partition wall (261) and a fifth guide pit (262) and a sixth guide pit (263) arranged on both sides of the middle partition wall (261); the fifth guide pit (262) and the sixth guide pit (263) are respectively located at the overlapping parts of the middle guide hole (26) and the leading hole (24) and the trailing hole (25); during the construction process, temporary supports (264) are arranged in the fifth guide pit (262) and the sixth guide pit (263).

5. The urban shallow buried spiral tunnel according to claim 4 is characterized by: The temporary support (264) is a steel bar, and the arrangement direction of the steel bar is perpendicular to the direction of the tunnel.

6. The urban shallow buried spiral tunnel according to claim 4 is characterized by: The temporary support (264) is a steel pipe (2641), the setting direction of the steel pipe (2641) is perpendicular to the direction of the tunnel, and the diameter of the steel pipe (2641) is 105-110 mm, and the interval between adjacent steel pipes (2641) is 48 cm-52 cm.

7. The urban shallow buried spiral tunnel according to claim 4 is characterized by: The temporary support (264) is composed of concrete layers (2642) and gravel layers (2643) arranged alternately.

8. The urban shallow buried spiral tunnel according to claim 7 is characterized by: The thickness of the concrete layer (2642) and the crushed stone layer (2643) are 48 cm to 52 cm respectively.

9. The urban shallow buried spiral tunnel according to claim 4, characterized in that: The bottoms of the fifth pilot pit (262) and the sixth pilot pit (263) are respectively provided with resistance backfill (265).

10. The urban shallow buried spiral tunnel according to claim 4, characterized in that: The middle partition wall (261) is a curved wall with recessed sides.

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