A comprehensive drainage and expansion system suitable for a double-hole tunnel and a construction and operation method thereof

Abstract

The application discloses a kind of comprehensive drainage expansion system suitable for double-hole tunnel and its construction, operation method, belong to tunnel drainage system technical field.The system includes high elevation tunnel and low elevation tunnel, the high elevation tunnel is equipped with existing center circular pipe ditch A, the low elevation tunnel is communicated with high elevation tunnel by several horizontal passages, the low elevation tunnel is equipped with existing center circular pipe ditch B and newly-built drainage ditch, the newly-built drainage ditch is located between horizontal passage and existing center circular pipe ditch B, and newly-built drainage ditch is communicated with existing center circular pipe ditch B by drainage assembly, the lower side of several horizontal passages is equipped with horizontal drainage branch ditch, and one end of horizontal drainage branch ditch is communicated with newly-built drainage ditch, and the other end is communicated with existing center circular pipe ditch A by connecting well.By comprehensive drainage system, the drainage capacity of low elevation tunnel and high elevation tunnel can be significantly improved, to ensure the driving safety in tunnel and the reliability of tunnel structure.

Description

Technical Field

[0001] This invention relates to an integrated drainage expansion system suitable for twin-tunnel structures and its construction and operation methods, belonging to the field of tunnel drainage technology. Background Technology

[0002] Due to limitations of the era, design concepts, and insufficient understanding of the surrounding rock, early tunnel construction often employed two methods for longitudinal drainage trenches: a small-diameter central circular trench in the middle of the tunnel, or small-sized buried side trenches on both sides of the tunnel surface. Because these two methods have relatively limited drainage capacity, water accumulation behind the tunnel lining in karst or water-rich strata often cannot be efficiently drained. This leads to a series of water-related problems in operating tunnels, including water seepage or runoff on the tunnel surface, waterlogging and deformation of the tunnel invert, road surface cracking or bulging, cable trench distortion, and water leakage from the tunnel sidewalls. If the groundwater contains highly corrosive ions such as sulfate, it further erodes the tunnel lining structure, causing cracking, spalling, and strength degradation of the tunnel lining concrete. It is evident that tunnel lining in water-rich and corrosive environments faces severe challenges, and improper handling can create safety hazards for vehicle traffic and the reliability of the tunnel structure.

[0003] To address the numerous water hazards and structural defects that occur in tunnels under water-rich and corrosive environments, one effective measure in engineering is to drain water away from the tunnel, reducing groundwater accumulation around the tunnel. This, in turn, reduces the contact area and infiltration time between groundwater and the lining structure, effectively controlling the risk of corrosive groundwater seeping into the tunnel structure. Based on this technical approach, researching a comprehensive drainage and expansion system suitable for twin-tunnel structures, along with its construction and operation methods, is of significant practical importance. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides an integrated drainage and expansion system suitable for twin-tunnel structures, along with its construction and operation methods.

[0005] This invention is achieved through the following technical solution: A comprehensive drainage expansion system suitable for twin tunnels includes a high-elevation tunnel and a low-elevation tunnel. The high-elevation tunnel has an existing central circular pipe trench A. The low-elevation tunnel is connected to the high-elevation tunnel through several cross passages. The low-elevation tunnel has an existing central circular pipe trench B and a newly built drainage ditch. The newly built drainage ditch is located between the cross passages and the existing central circular pipe trench B, and the newly built drainage ditch is connected to the existing central circular pipe trench B through drainage components. Each of the cross passages has a transverse drainage branch ditch on its lower side, and one end of the transverse drainage branch ditch is connected to the newly built drainage ditch, and the other end is connected to the existing central circular pipe trench A through a connecting well. The existing central circular pipe trench B includes a circular pipe, and a gravel blind ditch is provided on the upper side of the circular pipe. Multiple drainage holes are opened on the side of the circular pipe facing the gravel blind ditch.

[0006] The newly constructed drainage ditch is a rectangular drainage ditch, including a drainage ditch channel and a ditch body located within the drainage ditch channel. Concrete backfill ditch sides are provided between the ditch body and the two side walls of the drainage ditch channel, and a precast reinforced concrete cover plate is provided on the top of the ditch body.

[0007] The drainage system includes a transverse drainage ditch and multiple pre-embedded drainage pipes. The transverse drainage ditch is located longitudinally along the low-elevation tunnel within the concrete backfill ditch between the ditch body and the existing central circular pipe ditch B. The transverse drainage ditch is filled with gravel wrapped in geotextile. One end of the transverse drainage ditch along the transverse direction of the low-elevation tunnel is connected to the gravel drainage ditch above the existing central circular pipe ditch B, and the other end extends to the outer wall of the ditch body. One end of the multiple pre-embedded drainage pipes extends into the ditch body, and the other end extends into the transverse drainage ditch.

[0008] The transverse drainage blind ditch has a downward slope of no less than 2% from the B side of the existing central circular pipe ditch to the side of the ditch body. Multiple pre-embedded drainage pipes are set at intervals of 2m to 5m in the longitudinal direction of the low-elevation tunnel. The diameter of the pre-embedded drainage pipes is 50mm to 110mm. The length of the pre-embedded drainage pipes extending into the transverse drainage blind ditch is 5cm to 10cm. Multiple drainage holes are opened on the side wall of the pre-embedded drainage pipes located in the transverse drainage blind ditch.

[0009] The transverse drainage ditch includes a main body, one end of which extends into the low-elevation tunnel and connects with the newly built drainage ditch, and the other end extends into the high-elevation tunnel and connects with the connecting well. The end of the main body of the ditch closer to the newly built drainage ditch is inclined downward relative to the other end. The bottom plate of the main body of the branch ditch is equipped with a sedimentation block, and the top of the main body of the branch ditch is provided with an inspection port that connects to the cross passage. An inspection cover is installed at the inspection port, and the inspection port is connected to the bottom plate of the main body of the branch ditch through an inspection ladder.

[0010] A fire-fighting water storage tank is provided in the middle of the bottom slab of the main branch ditch, and the depth of the fire-fighting water storage tank is less than 1.5m. The longitudinal slope of the bottom slab of the main branch ditch on both sides of the fire-fighting water storage tank is that the end closer to the fire-fighting water storage tank is lower than the other end.

[0011] The bottom plates of the branch ditches on both sides of the fire-fighting water storage tank are equipped with sand-collecting blocks, and the tops of the branch ditches on both sides of the fire-fighting water storage tank are equipped with inspection ports that connect to the cross passage.

[0012] The connecting well includes a well body and a well cover. The bottom elevation of the well body is lower than the bottom elevation of the existing central circular pipe trench A. The well cover is located at the well opening of the well body and contacts the bottom surface of the asphalt surface layer of the road structure inside the high-elevation tunnel.

[0013] Structural reinforcing beams are provided at the intersections of the transverse drainage ditch with the high-elevation tunnel lining structure and the low-elevation tunnel lining structure.

[0014] Corrosion-resistant steel ropes are installed between every two adjacent transverse drainage branches in the existing central circular pipe trench A, the existing central circular pipe trench B, and the newly built drainage ditch.

[0015] A construction method for an integrated drainage and expansion system suitable for twin-tunnel tunnels includes the following steps: Step 1: Implement traffic control for high-elevation tunnels and low-elevation tunnels, and conduct surveying and setting out. Mark the locations of the excavation pits for the new drainage ditch, the transverse drainage branch ditch, and the connecting well inside the tunnel. Step 2: Excavate and construct the new drainage ditch in sections, and reserve the connection points with the transverse drainage branch ditches during the construction process; Step 3: Excavate and construct the transverse drainage branch ditches in sections, and connect the transverse drainage branch ditches with the newly built drainage ditches; Step 4: Excavate and construct the connecting well, and connect the connecting well to the existing central circular pipe trench A and the transverse drainage branch trench; Step 5: After completing the construction of all new drainage ditches, transverse drainage branches and connecting wells, restore the road surface structure in the high-elevation tunnel, cross passage and low-elevation tunnel.

[0016] In step two, the excavation slope of the drainage ditch to be excavated on the side close to the existing central circular pipe trench B is determined based on its distance from the circular pipe trench. On the one hand, it is required that the distance from the excavation edge of the drainage ditch to be excavated to the circular pipe trench is not less than 30cm. On the other hand, it is required that the excavation edge of the drainage ditch to be excavated intersects with the gravel blind ditch, and the height of the intersection is not less than 20cm, so as to ensure that the depth of the transverse water guiding blind ditch is not less than 20cm.

[0017] An operation method for an integrated drainage expansion system suitable for twin tunnels, wherein the water flow in the existing central circular pipe trench A in the high-elevation tunnel flows into the transverse drainage branch ditch in sections through the connecting well, and the water flow after being treated by sedimentation in the transverse drainage branch ditch flows into the newly built drainage ditch, and then is discharged into the low-elevation tunnel along the newly built drainage ditch. When a fire-fighting water storage tank is installed in the transverse drainage branch ditch, the water in the existing central circular pipe ditch A and the water in the newly built drainage ditch will be collected in the fire-fighting water storage tank first. After the fire-fighting water storage tank is full, the water in the existing central circular pipe ditch A will flow into the newly built drainage ditch through the transverse drainage branch ditch and then be discharged into the low-elevation tunnel along the newly built drainage ditch. When the water level in the existing central circular pipe trench B is lower than that in the transverse drainage blind ditch, the water collected in the existing central circular pipe trench B continues to flow along the existing central circular pipe trench B; when the drainage capacity of the existing central circular pipe trench B is insufficient or there is a local blockage, the water level in the existing central circular pipe trench B rises, and then the water in its circular pipe is back-pressed into the gravel blind ditch through the drain hole set at the top of the circular pipe, and then flows into the newly built drainage ditch through the transverse drainage blind ditch and the pre-buried drainage pipe, and is discharged out of the low elevation tunnel along the newly built drainage ditch.

[0018] The beneficial effects of this invention are as follows: 1. The newly constructed drainage system within the low-elevation tunnel is connected to the existing central circular pipe trench B via drainage components, forming a combined drainage system that significantly improves the drainage capacity of the low-elevation tunnel. Compared to the conventional approach of demolishing and rebuilding the existing central circular pipe trench B, this method offers stronger overall drainage capacity, effectively reduces the scale of project scrapping, and is more economical.

[0019] In addition, during construction, only one side of the existing central circular pipe trench B needs to be excavated, and the existing central circular pipe trench B can be preserved. This can effectively ensure the drainage needs of the low-elevation tunnel during construction. Furthermore, since the construction excavation site is located on one side of the existing central circular pipe trench B, there is half-width traffic condition in the low-elevation tunnel, which is conducive to traffic organization during construction.

[0020] 2. By utilizing the transverse drainage branch ditch located on the lower side of the cross passage, the connecting well in the high-elevation tunnel that connects to the existing central circular pipe trench A is connected to the combined drainage system in the low-elevation tunnel, which is composed of newly built drainage ditches, drainage components, and the existing central circular pipe trench B. This forms a comprehensive drainage system, which significantly improves the drainage capacity of the high-elevation tunnel while effectively controlling the scale of the reconstruction of the high-elevation tunnel drainage system. Moreover, the construction is relatively quick and economical.

[0021] 3. The integrated drainage system can significantly improve the drainage capacity of both low-elevation and high-elevation tunnels, thereby enabling timely and efficient drainage of water from both tunnels. This avoids a series of problems that occur frequently after operation, such as water seepage or flow on the road surface, waterlogging and subsidence of the tunnel invert arch, road surface cracking or bulging, cable trench distortion, and water leakage in the tunnel sidewalls. It also reduces the risk of cracking, peeling, or strength degradation of the tunnel lining caused by groundwater erosion, effectively ensuring the driving safety and structural reliability of the tunnel.

[0022] 4. The longitudinal slope of the main bottom plate of the branch ditches on both sides of the fire water storage tank is lower at the end closer to the fire water storage tank than at the other end, so that the water in the existing central circular pipe trench A and the water in the newly built drainage ditch will preferentially converge to the fire water storage tank, providing a reliable water supply point for fire fighting in the tunnel.

[0023] 5. An inspection port connected to the cross passage is opened at the top of the main branch ditch. Personnel can enter the transverse drainage branch ditch through the inspection port, and then carry out inspection and dredging of the integrated drainage system without affecting the normal passage of vehicles in the tunnel, which is conducive to the subsequent maintenance of the tunnel drainage system. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the main structure of the present invention without a fire-fighting water storage tank; Figure 2 for Figure 1 A magnified view of a portion at point A; Figure 3 for Figure 1 A magnified view of the area at point B; Figure 4 This is a schematic diagram of the main structure of the present invention when a fire-fighting water storage tank is provided; Figure 5 This is a top view of the structure of the present invention; Figure 6 This is a schematic diagram of the assembly structure of the low-elevation tunnel, the existing central circular pipe trench B, the newly built drainage ditch, and the drainage components of the present invention. Figure 7 This is a schematic diagram of the assembly structure of the transverse channel and the transverse drainage branch ditch without a fire-fighting water storage tank according to the present invention. Figure 8 This is a schematic diagram of the assembly structure of the transverse channel and the transverse drainage branch ditch equipped with a fire-fighting water storage tank according to the present invention. Figure 9 This is a schematic diagram of the structure of the present invention, which involves excavating the existing central circular pipe trench B in a low-elevation tunnel and constructing a new drainage ditch at the location of the existing central circular pipe trench B.

[0025] In the diagram: 1-High-elevation tunnel, 11-Existing central circular pipe trench A, 2-Low-elevation tunnel, 21-Existing central circular pipe trench B, 211-Gravel blind ditch, 3-Cross passage, 4-Newly built drainage ditch, 41-Drainage ditch trench, 42-Ditch body, 43-Concrete backfill ditch side, 44-Precast reinforced concrete cover plate, 5-Drainage components, 51-Transverse water guiding blind ditch, 52-Embedded drainage pipe, 6-Transverse drainage branch ditch, 61-Branch ditch body, 62-Sedimentation block, 63-Inspection port, 64-Inspection cover plate, 65-Inspection ladder, 66-Fire water storage tank, 7-Connecting well, 71-Well body, 72-Well cover, 8-Structural reinforcing beam, 9-Transverse drainage pipe, 10-Corrosion resistant steel rope. Detailed Implementation

[0026] The technical solution of the present invention is further described below, but the scope of protection is not limited to what is described.

[0027] Example 1: like Figures 1 to 8 As shown, the present invention discloses a comprehensive drainage expansion system suitable for twin tunnels, comprising a high-elevation tunnel 1 and a low-elevation tunnel 2. The high-elevation tunnel 1 is equipped with an existing central circular pipe trench A11. The low-elevation tunnel 2 is connected to the high-elevation tunnel 1 through multiple transverse passages 3. The low-elevation tunnel 2 is equipped with an existing central circular pipe trench B21 and a newly constructed drainage ditch 4. The newly constructed drainage ditch 4 is located between the transverse passages 3 and the existing central circular pipe trench B21, and is connected to the existing central circular pipe trench B21 through a drainage component 5. Each of the multiple transverse passages 3 has a transverse drainage branch ditch 6 on its lower side, and one end of the transverse drainage branch ditch 6 is connected to the newly constructed drainage ditch 4, and the other end is connected to the existing central circular pipe trench A11 through a connecting well 7. The existing central circular pipe trench B21 includes a circular pipe, on the upper side of which is a gravel blind drain 211, and multiple drainage holes are opened on the side of the circular pipe facing the gravel blind drain 211. In use, the cross passage 3 is a tunnel vehicle cross passage or a tunnel pedestrian cross passage.

[0028] The newly constructed drainage ditch 4 within the low-elevation tunnel 2 is connected to the existing central circular pipe trench B21 via drainage components 5, thus forming a combined drainage system that significantly improves the drainage capacity of the low-elevation tunnel 2. Compared to the conventional approach of demolishing and rebuilding the existing central circular pipe trench B21, this method offers stronger overall drainage capacity, effectively reduces the scale of project scrapping, and is more economical.

[0029] In addition, during the construction period, only one side of the existing central circular pipe trench B21 needs to be excavated, and the existing central circular pipe trench B21 can be preserved. This can effectively ensure the drainage needs of the low-elevation tunnel 2 during the construction period. Furthermore, since the construction excavation site is located on one side of the existing central circular pipe trench B21, there are half-width traffic conditions in the low-elevation tunnel 2, which is conducive to traffic organization during the construction period.

[0030] By utilizing the transverse drainage branch ditch 6 located on the lower side of the transverse passage 3, the connecting well 7, which connects the high-elevation tunnel 1 to the existing central circular pipe trench A11, is connected to the combined drainage system in the low-elevation tunnel 2, which is composed of a newly built drainage ditch 4, drainage components 5, and the existing central circular pipe trench B21. This forms a comprehensive drainage system, which significantly improves the drainage capacity of the high-elevation tunnel 1 while effectively controlling the scale of the reconstruction of the drainage system of the high-elevation tunnel 1. Moreover, the construction is relatively quick and economical.

[0031] It is evident that the integrated drainage system can significantly improve the drainage capacity of both the low-elevation tunnel 2 and the high-elevation tunnel 1, thereby enabling timely and efficient drainage of water from both tunnels. This avoids a series of problems that occur frequently after operation, such as water seepage or flow on the road surface, waterlogging and subsidence deformation of the tunnel invert arch, road surface cracking or bulging, cable trench distortion, and water leakage in the tunnel sidewalls. It also reduces the risk of cracking, peeling, or strength degradation of the tunnel lining caused by groundwater erosion, effectively ensuring the driving safety and structural reliability of the tunnel.

[0032] The newly constructed drainage ditch 4 is a rectangular drainage ditch, including a drainage ditch channel 41 and a ditch body 42 located in the drainage ditch channel 41. Concrete backfill ditch sides 43 are provided between the ditch body 42 and the two side walls of the drainage ditch channel 41. A precast reinforced concrete cover plate 44 is provided on the top of the ditch body 42.

[0033] The drainage component 5 includes a transverse drainage blind ditch 51 and multiple pre-embedded drainage pipes 52. The transverse drainage blind ditch 51 is longitudinally located along the low-elevation tunnel 2 within the concrete backfill ditch sidewall 43 between the ditch body 42 and the existing central circular pipe ditch B21. The transverse drainage blind ditch 51 is filled with gravel wrapped in geotextile. One end of the transverse drainage blind ditch 51 along the transverse direction of the low-elevation tunnel 2 is connected to the gravel blind ditch 211 above the existing central circular pipe ditch B21, and the other end extends to the outer wall of the ditch body 42. One end of the multiple pre-embedded drainage pipes 52 extends into the ditch body 42, and the other end extends into the transverse drainage blind ditch 51.

[0034] The transverse drainage ditch 51 has a downward slope of no less than 2% from the existing central circular pipe trench B21 to the ditch body 42. Multiple pre-embedded drainage pipes 52 are spaced 2m to 5m apart along the longitudinal direction of the low-elevation tunnel 2. The diameter of the pre-embedded drainage pipes 52 is 50mm to 110mm, and the length extending from the pre-embedded drainage pipes 52 into the transverse drainage ditch 51 is 5cm to 10cm. Multiple drainage holes are provided on the sidewall of the pre-embedded drainage pipes 52 within the transverse drainage ditch 51. In use, the transverse drainage ditch 51 has a downward slope of no less than 2% from the existing central circular pipe trench B21 to the ditch body 42 to facilitate water flow from the transverse drainage ditch 51 to the newly constructed drainage ditch 4.

[0035] The transverse drainage branch ditch 6 includes a branch ditch body 61. One end of the branch ditch body 61 extends into the low elevation tunnel 2 and is connected to the newly built drainage ditch 4. The other end extends into the high elevation tunnel 1 and is connected to the connecting well 7. The branch ditch body 61 is inclined downward relative to the other end at the end closer to the newly built drainage ditch 4. The bottom plate of the main branch channel 61 is equipped with a sediment trap 62, and the top of the main branch channel 61 has an inspection port 63 that connects to the cross passage 3. An inspection cover 64 is installed at the inspection port 63, and the inspection port 63 is connected to the bottom plate of the main branch channel 61 via an inspection ladder 65. In use, the sediment trap 62 serves as a structure to intercept sediment in the water flow. The inspection port 63 serves as a passage for personnel to enter the main branch channel 61 via the cross passage 3 for routine maintenance and as a channel for transporting the sediment intercepted by the sediment trap 62.

[0036] The connecting well 7 includes a well body 71 and a well cover 72. The bottom elevation of the well body 71 is lower than the bottom elevation of the existing central circular pipe trench A11. The well cover 72 is located at the well opening of the well body 71 and contacts the bottom surface of the asphalt surface layer of the road structure inside the high-elevation tunnel 1. The lower bottom elevation of the well body 71 facilitates the efficient flow of water from the existing central circular pipe trench A11 into the transverse drainage branch ditch 6. The contact between the well cover 72 and the bottom surface of the asphalt surface layer of the road structure inside the high-elevation tunnel 1 facilitates the later removal of the asphalt surface layer and the opening of the well cover 72 for inspection and maintenance of the connecting well 7, etc.

[0037] Structural reinforcing beams 8 are provided at the intersections of the transverse drainage branch 6 with the lining structures of the high-elevation tunnel 1 and the low-elevation tunnel 2. The structural reinforcing beams 8 are made of reinforced concrete and ensure the structural reliability at the intersections of the transverse drainage branch 6 with the lining structures of the high-elevation tunnel 1 and the low-elevation tunnel 2.

[0038] Corrosion-resistant steel ropes 10 are installed between every two adjacent transverse drainage branches 6 in the existing central circular pipe trench A11, existing central circular pipe trench B21, and newly built drainage ditch 4. This facilitates the use of corrosion-resistant steel ropes 10 to drag pipe flushing equipment, maintenance equipment, etc., to carry out ditch maintenance work on the existing central circular pipe trench A11, existing central circular pipe trench B21, or newly built drainage ditch 4.

[0039] A construction method for an integrated drainage and expansion system suitable for twin-tunnel tunnels includes the following steps: Step 1: Implement traffic control for high-elevation tunnel 1 and low-elevation tunnel 2, and conduct surveying and marking. Mark the locations of the new drainage ditch 4 (to be excavated), the transverse drainage branch ditch 6 (to be excavated), and the connecting well 7 (to be excavated) within the tunnels.

[0040] Based on the location of the newly constructed drainage ditch 4 marked on the road surface inside the low-elevation tunnel 2, the asphalt surface layer is milled layer by layer, and the milling edge line on the transverse side of the low-elevation tunnel 2 extends outward by 60cm on one side relative to the edge line of the drainage ditch 41; the concrete pavement slab above the drainage ditch 41 is cut, and the cutting edge line on the transverse side of the low-elevation tunnel 2 extends outward by 30cm on one side relative to the edge line of the drainage ditch 41; the purpose of this staggered joint construction is to avoid serious cracking of the pavement structure at construction joints.

[0041] Step 2: Excavate and construct the new drainage ditch 4 in sections, and reserve the connection points with the transverse drainage branch ditch 6 during the construction process.

[0042] Step 3: Excavate and construct the transverse drainage branch ditch 6 in sections, and connect the transverse drainage branch ditch 6 to the newly built drainage ditch 4. The excavation pit for the transverse drainage branch ditch 6 is located in the center of the cross section of the transverse channel 3. One end of it is connected to the newly built drainage ditch 4, and the other end is connected to the existing central circular pipe trench A11. The cross-sectional dimensions of the excavation are determined according to the dimensions of the transverse drainage branch ditch 6.

[0043] Specifically, the construction sequence of the transverse drainage branch 6 proceeds in an orderly manner from the side of the low-elevation tunnel 2 to the side of the high-elevation tunnel 1. At the same time, the width of the road panel removal inside the transverse passage 3 is 30cm outward from the side lines of the excavation pit to be excavated for the transverse drainage branch 6.

[0044] To prevent water from the newly constructed drainage ditch 4 from flowing into the transverse drainage branch ditch 6 during construction, a temporary water-blocking plate can be installed at the connection between the two.

[0045] Step 4: Excavate and construct connecting well 7, and connect connecting well 7 to the existing central circular pipe trench A11 and the transverse drainage branch trench 6. The excavation pit for connecting well 7 is located at the connection point between the existing central circular pipe trench A11 and the transverse drainage branch trench 6. During construction, the water in the existing central circular pipe trench A11 needs to be temporarily pumped out. After the existing central circular pipe trench A11 is connected to the transverse drainage branch trench 6, the water in the existing central circular pipe trench A11 will flow into the transverse drainage branch trench 6.

[0046] Step 5: After completing the construction of the new drainage ditch 4, the transverse drainage branch ditch 6 and the connecting well 7, restore the road surface structure in the high-elevation tunnel 1, the cross passage 3 and the low-elevation tunnel 2.

[0047] In step two, the excavation slope of the drainage ditch 41 to be excavated, near the existing central circular pipe trench B21, is determined based on its distance from the circular pipe trench. On one hand, the distance from the excavation edge of the drainage ditch 41 to the circular pipe trench is required to be no less than 30cm (to avoid damage to the structure of the circular pipe trench during construction). On the other hand, the excavation edge of the drainage ditch 41 to be excavated is required to intersect with the gravel blind ditch 211, and the height of the intersection point is no less than 20cm, to ensure that the depth of the transverse water-guiding blind ditch 51 is no less than 20cm. The bottom width of the drainage ditch 41 to be excavated is consistent with the width of the ditch body 42.

[0048] In addition, during the excavation of the new drainage ditch 4, the broken horizontal drainage pipe 9 was connected to the new drainage ditch 4 using a socket connection method.

[0049] An operation method for an integrated drainage expansion system suitable for twin tunnels: in the high-elevation tunnel 1, the water flow in the existing central circular pipe trench A11 is divided into sections and flows into the transverse drainage branch 6 through the connecting well 7. After being treated by sedimentation in the transverse drainage branch 6, the water flow flows into the newly built drainage ditch 4 and then is discharged into the low-elevation tunnel 2 along the newly built drainage ditch 4. When the water level in the existing central circular pipe trench B21 is lower than that in the transverse drainage blind ditch 51, the water collected in the existing central circular pipe trench B21 continues to flow along the existing central circular pipe trench B21; when the drainage capacity of the existing central circular pipe trench B21 is insufficient or there is a partial blockage, the water level in the existing central circular pipe trench B21 rises, and then the water in its circular pipe is back-pressed into the gravel blind ditch 211 through the drain hole set at the top of the circular pipe, and then flows into the newly built drainage ditch 4 through the transverse drainage blind ditch 51 and the pre-embedded drainage pipe 52, and is discharged into the low-elevation tunnel 2 along the newly built drainage ditch 4.

[0050] Example 2: The difference between Embodiment 2 and Embodiment 1 is as follows: A fire-fighting water storage tank 66 is recessed in the middle of the bottom slab of the main branch ditch 61, and the depth of the fire-fighting water storage tank 66 is less than 1.5m. The longitudinal slope of the bottom slab of the main branch ditch 61 on both sides of the fire-fighting water storage tank 66 is such that the end closer to the fire-fighting water storage tank 66 is lower than the other end. During use, the depth of the fire-fighting water storage tank 66 is less than 1.5m to prevent people from accidentally falling into the fire-fighting water storage tank 66 and drowning. The longitudinal slope of the bottom slab of the main branch ditch 61 on both sides of the fire-fighting water storage tank 66 is such that the end closer to the fire-fighting water storage tank 66 is lower than the other end, so that water in the existing central circular pipe trench A11 and the newly built drainage ditch 4 preferentially converges into the fire-fighting water storage tank 66. After the fire-fighting water storage tank 66 is full, the water in the central circular pipe trench A11 then flows through the main branch ditch 61 to the newly built drainage ditch 4.

[0051] The bottom plates of the branch ditch bodies 61 on both sides of the fire-fighting water storage tank 66 are equipped with sedimentation blocks 62, and the tops of the branch ditch bodies 61 on both sides of the fire-fighting water storage tank 66 are provided with inspection ports 63 that connect to the cross passage 3. The sedimentation blocks 62 prevent sediment in the water flow from entering the fire-fighting water storage tank 66. The inspection ports 63 on both sides of the fire-fighting water storage tank 66 serve as daily maintenance channels, fire-fighting water intake channels, and channels for transporting sediment intercepted by the sedimentation blocks 62.

[0052] When a fire-fighting water storage tank 66 is installed in the transverse drainage branch ditch 6, the water in the existing central circular pipe ditch A11 and the water in the newly built drainage ditch 4 will be collected in the fire-fighting water storage tank 66 first. After the fire-fighting water storage tank 66 is full, the water in the existing central circular pipe ditch A11 will flow into the newly built drainage ditch 4 through the transverse drainage branch ditch 6, and then be discharged into the low-elevation tunnel 2 along the newly built drainage ditch 4.

[0053] Example 3: The difference between Example 3 and Example 1 is that the existing central circular pipe trench B21 in the low-elevation tunnel 2 is excavated, and a new drainage ditch 4 is constructed at the location of the existing central circular pipe trench B21. The transverse drainage pipe 9 in the low-elevation tunnel 2 is then connected to the new drainage ditch 4.

Claims

1. A comprehensive drainage and expansion system suitable for twin-tunnel construction, characterized in that: The tunnel includes a high-elevation tunnel (1) and a low-elevation tunnel (2). The high-elevation tunnel (1) is equipped with an existing central circular pipe trench A (11). The low-elevation tunnel (2) is connected to the high-elevation tunnel (1) through several cross passages (3). The low-elevation tunnel (2) is equipped with an existing central circular pipe trench B (21) and a newly built drainage ditch (4). The newly built drainage ditch (4) is located between the cross passage (3) and the existing central circular pipe trench B (21). The newly built drainage ditch (4) is connected to the existing central circular pipe trench B (21) through a drainage component (5). The lower side of several cross passages (3) is equipped with a transverse drainage branch ditch (6). One end of the transverse drainage branch ditch (6) is connected to the newly built drainage ditch (4), and the other end is connected to the existing central circular pipe trench A (11) through a connecting well (7). The existing central circular pipe trench B (21) includes a circular pipe, and a gravel blind ditch (211) is provided on the upper side of the circular pipe, and multiple drainage holes are provided on the side of the circular pipe facing the gravel blind ditch (211). The newly built drainage ditch (4) is a rectangular drainage ditch, including a drainage ditch channel (41) and a water ditch body (42) set in the drainage ditch channel (41). A concrete backfill ditch side (43) is provided between the water ditch body (42) and the two side walls of the drainage ditch channel (41). A precast reinforced concrete cover plate (44) is provided on the top of the water ditch body (42). The drainage component (5) includes a transverse water-guiding blind ditch (51) and multiple pre-embedded drainage pipes (52). The transverse water-guiding blind ditch (51) is set longitudinally along the low elevation tunnel (2) in the concrete backfill ditch side (43) between the ditch body (42) and the existing central circular pipe ditch B (21). The transverse water-guiding blind ditch (51) is filled with gravel wrapped with geotextile. One end of the transverse water-guiding blind ditch (51) along the transverse direction of the low elevation tunnel (2) is connected to the gravel blind ditch (211) above the existing central circular pipe ditch B (21), and the other end extends to the outer wall of the ditch body (42). One end of the multiple pre-embedded drainage pipes (52) extends into the ditch body (42), and the other end extends into the transverse water-guiding blind ditch (51).

2. The integrated drainage and expansion system for twin-tunnel tunnels as described in claim 1, characterized in that: The transverse drainage blind ditch (51) is set with a downward slope of not less than 2% from the side of the existing central circular pipe ditch B (21) to the side of the ditch body (42). Multiple pre-embedded drainage pipes (52) are set at a spacing of 2m to 5m in the longitudinal direction of the low elevation tunnel (2), and the diameter of the pre-embedded drainage pipes (52) is 50mm to 110mm. The length of the pre-embedded drainage pipes (52) extending into the transverse drainage blind ditch (51) is 5cm to 10cm, and multiple drainage holes are opened on the side wall of the pre-embedded drainage pipes (52) located in the transverse drainage blind ditch (51).

3. The integrated drainage and expansion system for twin-tunnel tunnels as described in claim 1, characterized in that: The transverse drainage branch ditch (6) includes a branch ditch body (61), one end of which extends into the low elevation tunnel (2) and is connected to the newly built drainage ditch (4), and the other end extends into the high elevation tunnel (1) and is connected to the connecting well (7). The branch ditch body (61) is inclined downward relative to the other end at the end closest to the newly built drainage ditch (4). The bottom plate of the main body of the branch ditch (61) is provided with a sand-collecting block (62). The top of the main body of the branch ditch (61) is provided with an inspection port (63) that is connected to the cross passage (3). An inspection cover plate (64) is installed at the inspection port (63), and the inspection port (63) is connected to the bottom plate of the main body of the branch ditch (61) through an inspection ladder (65).

4. The integrated drainage and expansion system for twin-tunnel tunnels as described in claim 3, characterized in that: A fire-fighting water storage tank (66) is provided in the middle of the bottom plate of the main body (61) of the branch ditch, and the depth of the fire-fighting water storage tank (66) is less than 1.5m. The longitudinal slope of the bottom plate of the main body (61) of the branch ditch on both sides of the fire-fighting water storage tank (66) is lower at the end closer to the fire-fighting water storage tank (66) than at the other end.

5. The integrated drainage and expansion system for twin-tunnel as described in claim 4, characterized in that: The bottom plate of the branch ditch body (61) on both sides of the fire water storage tank (66) is provided with sedimentation blocks (62), and the top of the branch ditch body (61) on both sides of the fire water storage tank (66) is provided with an inspection port (63) that communicates with the cross passage (3).

6. The integrated drainage and expansion system for twin-tunnel tunnels as described in claim 1, characterized in that: The connecting well (7) includes a well body (71) and a well cover (72). The bottom elevation of the well body (71) is lower than the bottom elevation of the existing central circular pipe trench A (11). The well cover (72) is located at the well opening of the well body (71) and contacts the bottom surface of the asphalt surface layer of the road structure inside the high-elevation tunnel (1).

7. The integrated drainage and expansion system for twin-tunnel tunnels as described in claim 1, characterized in that: Structural reinforcing beams (8) are provided at the intersections of the transverse drainage branch ditch (6) with the lining structures of the high-elevation tunnel (1) and the low-elevation tunnel (2).

8. The integrated drainage and expansion system for twin-tunnel tunnels as described in claim 1, characterized in that: Corrosion-resistant steel ropes (10) are installed between every two adjacent transverse drainage branches (6) in the existing central circular pipe trench A (11), the existing central circular pipe trench B (21) and the newly built drainage ditch (4).

9. A construction method for an integrated drainage and expansion system applicable to twin-tunnel as described in any one of claims 1 to 8, characterized in that: Includes the following steps: Step 1: Traffic control is implemented for the high-elevation tunnel (1) and the low-elevation tunnel (2), and the lines are measured and marked inside the tunnels. The locations of the newly built drainage ditch (4), the foundation pit to be excavated, the transverse drainage branch ditch (6), the foundation pit to be excavated, and the connecting well (7), the foundation pit to be excavated, are measured and marked. Step 2: Excavate and construct the new drainage ditch (4) in sections, and reserve the connection between it and the transverse drainage branch ditch (6) during the construction process; Step 3: Excavate and construct the transverse drainage branch ditch (6) in sections, and connect the transverse drainage branch ditch (6) with the newly built drainage ditch (4); Step 4: Excavate and construct the connecting well (7), and connect the connecting well (7) with the existing central circular pipe trench A (11) and the transverse drainage branch trench (6); Step 5: After completing the construction of the new drainage ditch (4), the transverse drainage branch ditch (6) and the connecting well (7), restore the road structure in the high-elevation tunnel (1), the cross passage (3) and the low-elevation tunnel (2).

10. The construction method of the integrated drainage and expansion system applicable to twin-tunnel as described in claim 9, characterized in that: In step two, the excavation slope of the drainage ditch (41) to be excavated on the side close to the existing central circular pipe ditch B (21) is determined according to the distance between it and the circular pipe ditch. On the one hand, it is required that the distance from the excavation edge of the drainage ditch (41) to the circular pipe ditch is not less than 30cm. On the other hand, it is required that the excavation edge of the drainage ditch (41) to be excavated intersects with the gravel blind ditch (211), and the height of the intersection is not less than 20cm, so as to ensure that the depth of the transverse water guiding blind ditch (51) is not less than 20cm.

11. An operation method for an integrated drainage and expansion system suitable for twin-tunnel as described in claim 4 or 5, characterized in that: In the high-elevation tunnel (1), the water flow in the existing central circular pipe trench A (11) is divided into sections and flows into the transverse drainage branch (6) through the connecting well (7). After being treated by sedimentation in the transverse drainage branch (6), the water flows into the newly built drainage ditch (4) and then is discharged into the low-elevation tunnel (2) along the newly built drainage ditch (4). When a fire-fighting water storage tank (66) is installed in the transverse drainage branch (6), the water in the existing central circular pipe trench A (11) and the newly built drainage ditch (4) will be collected in the fire-fighting water storage tank (66) first. After the fire-fighting water storage tank (66) is full of water, the water in the existing central circular pipe trench A (11) will flow into the newly built drainage ditch (4) through the transverse drainage branch (6) and then be discharged into the low-elevation tunnel (2) along the newly built drainage ditch (4). When the water level in the existing central circular pipe trench B (21) is lower than that in the transverse drainage blind ditch (51), the water that has been collected in the existing central circular pipe trench B (21) continues to flow along the existing central circular pipe trench B (21); when the drainage capacity of the existing central circular pipe trench B (21) is insufficient or there is a local blockage, the water level in the existing central circular pipe trench B (21) rises, and the water in its circular pipe is back-pressed into the gravel blind ditch (211) through the drainage hole set at the top of the circular pipe, and then flows into the newly built drainage ditch (4) through the transverse drainage blind ditch (51) and the pre-buried drainage pipe (52), and is discharged into the low elevation tunnel (2) along the newly built drainage ditch (4).

Images