Connection air duct crossing three holes and construction method of connection air duct

Abstract

The invention relates to the technical field of underground engineering construction, in particular to an upward-crossing three-hole connection air duct and a construction method thereof. The three holes comprise a first driving tunnel, a second driving tunnel and a parallel guide which are parallel to one another; the elevation of the first driving tunnel is equal to that of the second driving tunnel, the connection air duct is horizontally arranged above the three holes, and the axial direction of the connection air duct is perpendicular to the axial direction of the first driving tunnel; the distance between the bottom surface of the connecting air duct and the axis of the first driving tunnel is smaller than the radius of the first driving tunnel; and the first driving tunnel and the second driving tunnel are both communicated with the connection air duct. By optimally designing the structure of the connecting air duct, the design longitudinal slope of the connecting air duct can be reduced, the construction difficulty of the connecting air duct is reduced, the construction length of the connecting air duct is shortened, and the construction cost is saved.

Description

Technical Field

[0001] The present invention relates to the technical field of underground engineering construction, and particularly relates to a connecting air duct spanning three tunnels and a construction method thereof. Background Art

[0002] In tunnel construction operations (especially highway tunnel construction), in order to avoid interference from vehicle intersections, generally, left and right separated tunnels are adopted, and the two tunnels are respectively used for vehicles in one driving direction. Before the construction of the two driving tunnels, for the purpose of understanding the geological conditions in advance and confirming the excavation direction of the driving tunnels, it is usually necessary to excavate a pilot tunnel prior to the driving tunnels. The two subsequent excavated driving tunnels are usually parallel to the pilot tunnel and are respectively located on both sides of the pilot tunnel (there is also a situation where both driving tunnels are located on the same side of the pilot tunnel). In this scenario, the connecting air duct for ventilating the two driving tunnels needs to be arranged to span three tunnels (i.e., span two driving tunnels and the pilot tunnel).

[0003] Currently, in order to ensure the safe construction of the connecting air duct (mainly to avoid the blasting shock wave endangering the driving tunnels and the pilot tunnel during the blasting process of the connecting air duct excavation), such a connecting air duct spanning three tunnels is usually constructed at a position 5 - 10 m higher than the elevation of the driving tunnels and is connected to each driving tunnel with a certain slope. However, such a connecting air duct has a large excavation volume, is time-consuming and laborious, and the designed longitudinal slope of the connecting air duct is large, resulting in high construction difficulty and high safety risks; in addition, it is also necessary to layout air duct construction equipment such as track transportation and carry out the air duct working face, and these will inevitably affect the construction speed of the main tunnel of the tunnel, making it difficult to quickly form the ventilation roadway of the driving tunnel, increasing the ventilation cost of long tunnels, causing waste of construction resources and delay of the construction progress, and further increasing the investment in project costs. Summary of the Invention

[0004] The purpose of the present invention is to provide a connecting air duct spanning three tunnels and a construction method thereof, which can at least partially overcome the above technical problems. By optimizing the design of the structure of the connecting air duct, the designed longitudinal slope of the connecting air duct can be reduced, the construction difficulty of the connecting air duct can be lowered, and the construction length of the connecting air duct can be shortened, while quickly forming the ventilation roadway of the driving tunnel, saving the project cost, and reducing the construction safety risk.

[0005] On the one hand, the present invention provides a connecting air duct spanning three tunnels, where the three tunnels include a first driving tunnel, a second driving tunnel, and a pilot tunnel that are parallel to each other; the elevations of the first driving tunnel and the second driving tunnel are equal, the connecting air duct is horizontally arranged above the three tunnels, and the axial direction of the connecting air duct is perpendicular to the axial direction of the first driving tunnel; the distance between the bottom surface of the connecting air duct and the axis of the first driving tunnel is less than the radius of the first driving tunnel; both the first driving tunnel and the second driving tunnel are communicated with the connecting air duct.

[0006] Furthermore, a blower house is provided on one side of the three tunnels, and a ventilation shaft is provided on the side of the blower house away from the three tunnels; the connecting air duct communicates with the blower house, and the blower house communicates with the ventilation shaft.

[0007] Furthermore, the distance between the bottom surface of the connecting air duct and the road surface of the first driving tunnel after completion is greater than the height required for driving in the first tunnel.

[0008] On the other hand, the present invention provides a construction method for a connecting air duct spanning over three tunnels, which is used to construct the connecting air duct spanning over three tunnels as described above. Specifically, the construction method includes: S1, after excavating the pilot tunnel to a preset depth, construct the connecting air duct above the pilot tunnel at the preset depth position to form a first node; S2, after excavating the first driving tunnel to the preset depth, construct the connecting air duct above the first driving tunnel at the preset depth position to form a second node; after excavating the second driving tunnel to the preset depth, construct the connecting air duct above the second driving tunnel at the preset depth position to form a third node; S3, construct the connecting air duct from the second node towards the first node to connect the first node and the second node; construct the connecting air duct from the third node towards the first node to connect the first node and the third node; S4, construct the connecting air duct from the blower house towards the third node to connect the third node and the blower house, and complete the excavation work of the connecting air duct; S5, perform secondary lining construction on the excavated connecting air duct to form the connecting air duct.

[0009] Furthermore, the pilot tunnel is excavated by an open TBM, and both the first driving tunnel and the second driving tunnel are excavated by the drill and blast method, and the pilot tunnel is excavated prior to the first driving tunnel and the second driving tunnel.

[0010] Furthermore, the construction of the connecting air duct above the flat guide is carried out by the three - step construction method, which includes: S11, after excavating the flat guide to a preset depth through the TBM, operate the TBM to stop and build a construction platform on the top of the main beam of the stopped TBM; S12, start the TBM to excavate forward by 1.8 m and then stop. Carry out the construction of the first step on the surrounding rock exposed by excavation in the 1.8 - m length direction on the construction platform; S13, repeat S12 until the construction of the first step is completed; S14, after the construction of the first step is completed, successively carry out the construction of the second step and the third step above the first step to complete the excavation work of the first node; S15, support the flat - guide section where the first node is located. Among them, the support for the flat - guide section where the first node is located includes: S151, set a steel arch frame at the opening position below the first node, and the steel arch frame covers the exposed opening below the first node; S152, lay a steel - plate layer between the opening below the first node and the steel arch frame, and support the steel - plate layer through the steel arch frame. The steel - plate layer is used to block the opening below the first node; S153, spray concrete in the area where the steel arch frame is set to form an initial support system, and carry out secondary lining with reinforced concrete below the initial support system.

[0011] Furthermore, both the first driving tunnel and the second driving tunnel are excavated by the manual drill - and - blast method, and the two - step construction method is adopted during the excavation process. The construction of the connecting air duct above the first driving tunnel includes: when excavating the first driving tunnel to a position 20 m away from the preset depth, switch to the three - step construction method and continue to excavate forward. Among them, the construction process of the top - most step is: first excavate forward to the position of the side - line of the connecting - air - duct excavation, and then carry out shallow - hole weak blasting backward to the position of the other side - line of the connecting air duct to form the face of the connecting air duct of the second node. The construction of the connecting air duct above the second driving tunnel includes: when excavating the second driving tunnel to a position 20 m away from the preset depth, switch to the three - step construction method and continue to excavate forward. Among them, the construction process of the top - most step is: first excavate forward to the position of the side - line of the connecting - air - duct excavation, and then carry out shallow - hole weak blasting backward to the position of the other side - line of the connecting air duct to form the face of the connecting air duct of the third node.

[0012] Further, the construction of the connecting air duct from the second node towards the first node includes: after constructing the connecting air duct above the first driving tunnel to form the second node, lofting the designed excavation contour line of the connecting air duct connecting the first node and the second node along the normal direction of the heading face of the connecting air duct at the second node, and excavating and supporting along this contour line; the construction of the connecting air duct from the third node towards the first node includes: after constructing the connecting air duct above the second driving tunnel to form the third node, lofting the designed excavation contour line of the connecting air duct connecting the first node and the third node along the normal direction of the heading face of the connecting air duct at the third node, and excavating and supporting along this contour line; the construction of the connecting air duct from the fan room towards the third node includes: determining the contour of the heading face for excavating the connecting air duct on one side wall of the fan room, lofting the designed excavation contour line of the connecting air duct connecting the fan room and the third node, and excavating and supporting along this contour line; Among them, during the process of excavating along the designed excavation contour line of the connecting air duct, full-section construction is adopted in the section with intact surrounding rock, and the two-bench method is adopted in the section with broken surrounding rock.

[0013] Further, the construction from the fan room towards the third node includes: after completion of excavation and support at the first node, the second node and the third node, an un-tracked stepping hydraulic trolley is used to carry out secondary lining construction from the fan room towards the third node.

[0014] Further, the secondary lining of the completed connecting air duct includes: adopting a Class III lining structure in the section with intact surrounding rock of the connecting air duct, and adopting a Class IV lining structure in the section with broken surrounding rock of the connecting air duct.

[0015] Compared with the prior art, the present invention has the following advantages and beneficial effects: 1. A connecting air duct straddling three tunnels and its construction method provided by the embodiments of the present disclosure horizontally straddle the connecting air duct above the three tunnels and lower the elevation position of the connecting air duct. On the one hand, it reduces the designed longitudinal slope of the connecting air duct, thereby reducing the construction difficulty and corresponding safety risks of the connecting air duct; on the other hand, there is no obvious slope section in this connecting air duct, thereby significantly reducing the excavation length of the connecting air duct, and thus the project cost can be saved; in addition, this connecting air duct is set straight. After it is connected to the fan room and the ventilation shaft, under the "chimney" effect of the ventilation shaft, the resistance to air flow in the connecting air duct is small, which is beneficial to improving the efficiency of the "self-priming" air circulation caused by the "chimney" effect. And when the traffic flow in the driving tunnel increases significantly, traffic accidents occur, fire accidents occur, etc., and a large amount of fresh air is required to enter, forced ventilation of the driving tunnel can be realized through the fan room; 2. A connecting air duct spanning three tunnels and its construction method provided by an embodiment of the present disclosure. This connecting air duct can make full use of the air-pushing effect on the air in the driving tunnel during the vehicle driving process, forcing the polluted air in the driving tunnel to enter the connecting air duct, and promoting the automatic circulation of air in the first driving tunnel and the second driving tunnel; by setting this connecting air duct spanning three tunnels on the three tunnels, it is possible to ventilate the driving tunnel mainly relying on the ventilation volume of the "chimney" effect and the ventilation volume pushed by the vehicle flow when the vehicles in the driving tunnel are passing normally, thereby effectively reducing the concentration of air pollutants in the driving tunnel, and thus effectively reducing the power of the fans configured in the fan room and reducing the startup duration of the fans; by setting a monitoring module, when the ventilation volume of the "chimney" effect + the ventilation volume pushed by the vehicle flow is not sufficient to reduce the concentration of air pollutants in the driving tunnel below the allowable concentration, the fans can be started in time to perform forced ventilation on the driving tunnel, thereby realizing reasonable control of the opening and closing of the fans, and further greatly reducing the power consumption and reducing the operation cost during the operation period after the tunnel is built. 3. A connecting air duct spanning three tunnels and its construction method provided by an embodiment of the present disclosure. By first constructing the first node, the second node, and the third node of the connecting air duct above the pilot tunnel, the first driving tunnel, and the second driving tunnel, then the pilot tunnel, the first driving tunnel, and the second driving tunnel can continue to be excavated forward, and at the same time, the construction work of the connecting air duct from the second node to the first node and from the third node to the first node can be carried out. Thus, the construction period can be greatly shortened, and the impact of the explosion shock wave of excavating the connecting air duct on the excavation work of the pilot tunnel, the first driving tunnel, and the second driving tunnel can be avoided when the connecting air duct is excavated after the excavation of the pilot tunnel, the first driving tunnel, and the second driving tunnel is completed; in addition, through the above construction method, the connecting air duct can be formed early, and during the excavation process of the pilot tunnel, the first driving tunnel, and the second driving tunnel, the connecting air duct can be used to realize ventilation and air change during the excavation process, thereby effectively improving the working environment of the working face during the excavation process of the pilot tunnel, the first driving tunnel, and the second driving tunnel, and reducing the harm of the polluted air in the tunnel to the construction personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings described herein are used to provide a further understanding of the embodiments of the present invention, form a part of this application, and do not constitute a limitation to the embodiments of the present invention. In the drawings: Figure 1 is a schematic diagram of a connecting air duct spanning three tunnels in the prior art; Figure 2 is a schematic diagram of a connecting air duct spanning three tunnels drawn according to an embodiment of the present invention; Figure 3 is a schematic diagram of the construction of the connecting air duct in the pilot tunnel drawn according to an embodiment of the present invention; Figure 4Schematic diagram of supporting the horizontal guide section where the first node is located, drawn according to an embodiment of the present invention; Figure 5 Drawn according to Figure 4 Partial enlarged view of area A; Figure 6 Schematic diagram of constructing a connecting air duct in a driving tunnel, drawn according to an embodiment of the present invention; Figure 7 Longitudinal sectional view of the driving tunnel, drawn according to an embodiment of the present invention.

[0017] Marks in the drawings and corresponding component names: 1 - ventilation shaft; 2 - fan room; 3 - connecting air duct; 4 - secondary lining; 5 - second driving tunnel; 6 - horizontal guide; 7 - first driving tunnel; 8 - third step; 9 - second step; 10 - first step; 11 - construction platform; 12 - steel plate layer; 13 - steel arch; 14 - shotcrete. Detailed implementation manners

[0018] To make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with embodiments and drawings. The illustrative embodiments and descriptions of the present invention are only used to explain the present invention and are not intended to limit the present invention. It should be noted that the present invention has been in the actual R & D and usage stage.

[0019] In tunnel construction operations (especially in highway tunnel construction), in order to avoid interference from vehicle intersections, usually a left - right separated tunnel is adopted, and the two tunnels are respectively used for vehicles in one driving direction. Before the construction of the two driving tunnels, for the purpose of understanding the geological conditions in advance and confirming the excavation direction of the driving tunnels, usually a horizontal guide needs to be excavated prior to the driving tunnels. The two subsequent excavated driving tunnels are usually parallel to the horizontal guide and are respectively located on both sides of the horizontal guide. In this scenario, the connecting air duct for ventilating the two driving tunnels needs to be set up across three tunnels (that is, across the two driving tunnels and the horizontal guide).

[0020] Currently, in order to ensure the safe construction of the connecting air duct (mainly to avoid the blasting shock wave endangering the driving tunnel and the horizontal guide during the blasting process of the connecting air duct excavation), this connecting air duct across three tunnels is usually constructed at a position 5 - 10 m higher than the elevation of the driving tunnel and is connected to each driving tunnel with a certain slope (such as Figure 1(as shown). However, the excavation volume of such a connecting air duct is relatively large, time-consuming and laborious, and the designed longitudinal slope of the connecting air duct is relatively large, resulting in high construction difficulty and great safety risks. In addition, it is necessary to layout air duct construction equipment such as track transportation and carry out the air duct working face, which will inevitably affect the construction speed of the main tunnel of the tunnel, making it difficult to quickly form a ventilation roadway for the running tunnel, increasing the ventilation cost of the long tunnel, causing waste of construction resources and delay of the construction progress, and further increasing the engineering cost investment.

[0021] For this reason, the present invention provides a connecting air duct spanning three tunnels and a construction method thereof. By optimizing the design of the structure of the connecting air duct, it is possible to achieve the purpose of reducing the designed longitudinal slope of the connecting air duct and reducing the construction difficulty of the connecting air duct, and it is also possible to shorten the construction length of the connecting air duct, save the project cost while quickly forming a ventilation roadway for the running tunnel, and reduce the construction safety risk.

[0022] Embodiment 1: As Figure 1 、 Figure 2 shown, this embodiment provides a connecting air duct spanning three tunnels. The three tunnels include a first running tunnel 7, a second running tunnel 5 and a parallel adit 6 that are parallel to each other; The elevations of the first running tunnel 7 and the second running tunnel 5 are equal. The connecting air duct 3 is horizontally arranged above the three tunnels, and the axis of the connecting air duct 3 is perpendicular to the axis of the first running tunnel 7; the distance between the bottom surface of the connecting air duct 3 and the axis of the first running tunnel 7 is less than the radius of the first running tunnel 7; Both the first running tunnel 7 and the second running tunnel 5 are communicated with the connecting air duct 3.

[0023] It should be understood that the cross-sectional sizes of the first running tunnel 7 and the second running tunnel 5 are equal; the aforementioned "the connecting air duct 3 is horizontally arranged" means that the connecting air duct is arranged roughly horizontally; in the schematic diagram of the connecting air duct spanning three tunnels in the prior art as Figure 1 shown, it can be seen that the existing connecting air duct 3 has a relatively large designed longitudinal slope, which is not convenient for slag transportation during the construction process of the connecting air duct 3 on the one hand, and also results in a relatively long length of the connecting air duct 3 on the other hand.

[0024] Preferably, a fan room 2 is also arranged on one side of the three tunnels, and a ventilation shaft 1 is arranged on the side of the fan room 2 away from the three tunnels; The connecting air duct 3 is communicated with the fan room 2, and the fan room 2 is communicated with the ventilation shaft 1.

[0025] Preferably, the fan room 2 can be switched between a blowing state and a suction state, that is, the fan room 2 can blow air towards the three tunnels and can also suck air from the three tunnels.

[0026] Accordingly, the connecting air duct spanning three tunnels provided in this embodiment reduces the elevation position of the connecting air duct 3 by horizontally spanning the connecting air duct 3 above the three tunnels. On the one hand, it reduces the designed longitudinal slope of the connecting air duct 3, thereby reducing the construction difficulty and corresponding safety risks of the connecting air duct 3. On the other hand, there is no obvious slope section in the connecting air duct 3, thus significantly reducing the excavation length of the connecting air duct 3, and thus saving the project cost. In addition, the connecting air duct 3 is set straight. After it is connected to the fan room 2 and the ventilation shaft 1, under the "chimney" effect of the ventilation shaft 1, the resistance to the air flow in the connecting air duct 3 is small, which is beneficial to improving the efficiency of the "self-priming" air circulation caused by the "chimney" effect. And when the traffic flow in the driving tunnel increases significantly, traffic accidents occur, or fire accidents occur, and a large amount of fresh air is required to enter, forced ventilation of the driving tunnel can be realized through the fan room 2 (the direction of the forced ventilation air flow can also be changed by adjusting the fan room 2 to switch between the blowing state and the suction state).

[0027] More preferably, the distance between the bottom surface of the connecting air duct 3 and the road surface of the first driving tunnel 7 after completion is greater than the height required for driving in the first tunnel. This can ensure the normal passage of vehicles in the first driving tunnel 7 and the second driving tunnel 5 while reducing the elevation of the connecting air duct 3 as much as possible.

[0028] More preferably, as Figure 7 shown, at the position where the connecting air duct 3 is connected to the first driving tunnel 7, the side wall of the connecting air duct 3 facing the oncoming direction of the vehicles in the first driving tunnel 7 is open; at the position where the connecting air duct 3 is connected to the second driving tunnel 5, the side wall of the connecting air duct 3 facing the oncoming direction of the vehicles in the second driving tunnel 5 is open. Thus, the connecting air duct 3 can make full use of the air-pushing effect of the vehicle flow during the driving process on the air in the driving tunnel, forcing the dirty air in the driving tunnel to enter the connecting air duct 3 and promoting the automatic circulation of the air in the first driving tunnel 7 and the second driving tunnel 5.

[0029] It should be noted that in the above tunnel structure, the dirty air in both the first driving tunnel 7 and the second driving tunnel 5 can be subject to the ventilation effect brought by the "chimney" effect of the ventilation shaft 1 and the ventilation effect brought by the air pushed by the vehicle flow during the driving process in the driving tunnel. That is to say, the total ventilation volume in the driving tunnel is the "chimney" effect ventilation volume + the vehicle flow pushing ventilation volume. Among them, the "chimney" effect ventilation volume is mainly affected by the effective cross-sectional area of the ventilation shaft 1, the height of the ventilation shaft 1, and the temperature difference between the inside and outside of the driving tunnel, and is a fixed value determined by the tunnel ventilation structure design; the vehicle flow pushing ventilation volume is mainly determined by the cross-sectional area of the driving tunnel, the cross-sectional area of the vehicle, the vehicle length, the vehicle traveling distance, and the driving speed. The vehicle flow pushing ventilation volume can be expressed as: , wherein,Q p is the ventilation volume driven by the vehicle flow, L v is the vehicle length, s is the vehicle traveling spacing, v is the driving speed, A t is the cross-sectional area of the driving tunnel, A v is the cross-sectional area of the vehicle.

[0030] Obviously, when the driving speed is low (such as traffic jams, car accidents), the ventilation volume driven by the vehicle flow can be ignored. At this time, a large number of vehicles are detained in the driving tunnel, resulting in a significant increase in the concentration of air pollutants in the driving tunnel. It is necessary to introduce a large amount of fresh air per unit time to reduce the concentration of air pollutants in the driving tunnel. It is difficult to achieve this only by relying on the ventilation volume of the "chimney" effect. It is necessary to forcibly ventilate the driving tunnel through the fan room 2; When the driving speed is high and the vehicle flow is small, the amount of polluting gas generated by the vehicle in the driving tunnel per unit time is small. Only a small amount of fresh air needs to be introduced per unit time to effectively reduce the concentration of air pollutants in the driving tunnel. At this time, the vehicle traveling spacing in the driving tunnel is large, and the corresponding ventilation volume driven by the vehicle flow is small. The total ventilation volume mainly relies on the ventilation volume of the "chimney" effect. In this case, it is only necessary that the ventilation volume of the "chimney" effect brought by the designed tunnel ventilation structure can dilute the polluting gas generated by the small vehicle flow to below the allowable concentration; When the driving speed is high and the vehicle flow is large, the amount of polluting gas generated by the vehicle in the driving tunnel per unit time is large. It is necessary to introduce more fresh air per unit time to effectively reduce the concentration of air pollutants in the driving tunnel. At this time, relying only on the ventilation volume of the "chimney" effect is not enough to reduce the concentration of air pollutants in the driving tunnel to below the allowable concentration. At this time, the vehicle traveling spacing is significantly shortened compared with when the vehicle flow is small, and the corresponding ventilation volume driven by the vehicle flow is significantly increased. The total ventilation volume relies on the combined action of the ventilation volume of the "chimney" effect and the ventilation volume driven by the vehicle flow. In this case, the concentration of air pollutants in the driving tunnel can also be effectively reduced to below the allowable concentration.

[0031] Preferably, a processor electrically connected to the fan is installed in the fan room, and a monitoring module electrically connected to the processor is also provided in the driving tunnel. The monitoring module can monitor the concentration of pollutants in the driving tunnel (the monitoring objects of the monitoring module at least include carbon monoxide, nitric oxide, nitrogen dioxide, PM2.5 and PM10. The monitoring module belongs to the prior art and will not be elaborated here). When the concentration of air pollutants in the driving tunnel is higher than the allowable concentration, the processor controls the fan to start and then forcibly ventilates the driving tunnel.

[0032] Accordingly, by arranging the connecting air duct 3 spanning over the three tunnels on the three tunnels, since the "chimney" effect of the ventilation shaft 1 and the pushing effect of the traffic flow on the air in the driving tunnel are fully utilized for ventilation, it is possible to ventilate the driving tunnel mainly relying on the ventilation volume of the "chimney" effect and the ventilation volume pushed by the traffic flow when the vehicles are passing through the driving tunnel normally, thereby effectively reducing the concentration of air pollutants in the driving tunnel. As a result, the power of the fans configured in the fan room 2 can be effectively reduced, and the startup duration of the fans can be reduced; by arranging the monitoring module, when the ventilation volume of the "chimney" effect + the ventilation volume pushed by the traffic flow is not sufficient to reduce the concentration of air pollutants in the driving tunnel below the allowable concentration, the fans can be started in time to perform forced ventilation on the driving tunnel, thereby realizing reasonable control of the opening and closing of the fans, and further greatly reducing the power consumption and the operation cost during the operation period after the tunnel is built.

[0033] Embodiment 2: As Figures 3 to 5 shown, this embodiment provides a construction method for the connecting air duct spanning over the three tunnels for constructing the aforementioned connecting air duct. The construction method for the connecting air duct includes: S1, after excavating the pilot tunnel 6 to a preset depth, construct the connecting air duct 3 above the pilot tunnel 6 at the preset depth position to form the first node; S2, after excavating the first driving tunnel 7 to the preset depth, construct the connecting air duct 3 above the first driving tunnel 7 at the preset depth position to form the second node; after excavating the second driving tunnel 5 to the preset depth, construct the connecting air duct 3 above the second driving tunnel 5 at the preset depth position to form the third node; S3, construct the connecting air duct 3 from the second node towards the first node to connect the first node and the second node; construct the connecting air duct 3 from the third node towards the first node to connect the first node and the third node; S4, construct the connecting air duct 3 from the fan room 2 towards the third node to connect the third node and the fan room 2, and complete the excavation work of the connecting air duct 3; S5, perform secondary lining construction on the excavated connecting air duct 3 to form the connecting air duct 3.

[0034] It should be understood that the above "preset depth" refers to the designed pile number position of the connecting air duct 3.

[0035] Therefore, in the construction method of the connecting air duct provided in this embodiment, by first constructing the first node, the second node, and the third node of the connecting air duct 3 above the pilot tunnel 6, the first driving tunnel 7, and the second driving tunnel 5, then the pilot tunnel 6, the first driving tunnel 7, and the second driving tunnel 5 can continue to be excavated forward, and at the same time, the construction operations of the connecting air duct 3 from the second node to the first node and from the third node to the first node can be carried out. Thus, the construction period can be significantly reduced, and the impact of the explosion shock wave during the excavation of the connecting air duct 3 on the excavation work of the pilot tunnel 6, the first driving tunnel 7, and the second driving tunnel 5 can be avoided when the excavation of the connecting air duct 3 is carried out after the excavation of the pilot tunnel 6, the first driving tunnel 7, and the second driving tunnel 5 is completed; in addition, through the above construction method, the connecting air duct 3 can be formed early, and then during the excavation of the pilot tunnel 6, the first driving tunnel 7, and the second driving tunnel 5, the connecting air duct 3 can be used to realize ventilation and air change during the excavation process, thereby effectively improving the working environment of the working face during the excavation of the pilot tunnel 6, the first driving tunnel 7, and the second driving tunnel 5, and reducing the harm of the dirty air in the tunnel to the construction workers.

[0036] Specifically, the pilot tunnel 6 is excavated by an open TBM, the first driving tunnel 7 and the second driving tunnel 5 are both excavated by the drill and blast method, and the pilot tunnel 6 is excavated prior to the first driving tunnel 7 and the second driving tunnel 5.

[0037] The construction of the connecting air duct 3 above the pilot tunnel 6 is carried out by the three - step construction method; it includes: S11, after the pilot tunnel 6 is excavated by the TBM to a preset depth, operate the TBM to stop and build a construction platform 11 on the top of the main beam of the stopped TBM. S12, start the TBM to excavate forward by 1.8 m and then stop. On the construction platform 11, carry out the construction of the first step 10 for the surrounding rock exposed in the 1.8 - m length direction. S13, repeat S12 until the construction of the first step 10 is completed. S14, after the construction of the first step 10 is completed, successively carry out the construction of the second step 9 and the third step 8 above the first step 10 to complete the excavation work of the first node. S15, support the section of the pilot tunnel 6 where the first node is located.

[0038] Preferably, after the TBM excavates the pilot tunnel 6 to a position 10 m away from the preset depth, during the process of continuing to excavate towards the preset depth, excavate a construction preparation area with an upward excavation slope of 1:5.

[0039] In the process of constructing the connecting air duct 3 above the pilot tunnel 6 by the three-step construction method as described above, the construction platform 11 erected on the top of the TBM main beam can, on the one hand, be used as a working platform for the three-step construction method, and on the other hand, also serve as a construction protection shed, which can effectively protect the TBM equipment below, especially the hydraulic equipment and electrical equipment in the TBML1 area below; excavating the construction preparation area with a slope of 1:5 can facilitate the roof excavation of the connecting air duct 3 above the pilot tunnel 6 and facilitate the rapid formation of the excavation working face of the three-step construction method.

[0040] It should be understood that during the implementation of the three-step construction method, in order to reduce the impact of blasting vibration on the TBM, the excavation of each step is preferably carried out using static blasting techniques such as splitting bars and wet diamond drills, supplemented by manual shallow-hole loosening blasting.

[0041] More specifically, the support for the section of the pilot tunnel 6 at the location of the first node includes: S151, a steel arch frame 13 is set at the opening position below the first node, and the steel arch frame 13 covers the exposed opening below the first node; preferably, there are multiple such steel arch frames 13, the steel section is HW175, and the spacing between two adjacent steel arch frames 13 is 45 cm; more preferably, between adjacent steel arch frames 13, they are also connected by HW125 steel sections to further increase the stiffness of the entire steel support layer; S152, a steel plate layer 12 is laid between the opening below the first node and the steel arch frame 13, and the steel plate layer 12 is supported by the steel arch frame 13, and the steel plate layer 12 is used to seal the opening below the first node; preferably, the steel plate layer 12 is formed by arranging multiple strip-shaped steel plates closely adjacent to each other; it should be understood that the steel plate layer completely covers and seals the opening below the first node; obviously, when setting the steel arch frame 13, a gap for accommodating the steel plate layer 12 is reserved between the opening below the first node and the steel arch frame 13; S153, shotcrete is sprayed in the area where the steel arch frame 13 is set to form an initial support system, and secondary lining is carried out with reinforced concrete below the initial support system; preferably, the thickness of the shotcrete 14 is 23.5 cm (referring to the distance between the surface of the shotcrete 14 and the steel plate layer 12, that is, the thickness of the initial support system is 23.5 cm); the thickness of the secondary lining 4 is 39 cm.

[0042] Accordingly, for the construction method of the connecting air duct provided in this embodiment, after the pilot tunnel 6 is excavated to the preset depth, the TBM for excavating the pilot tunnel 6 is used to assist in the construction of the connecting air duct 3 above the pilot tunnel 6, thereby forming the first node. The muck can be transported based on the muck transportation equipment and route of the TBM itself, so that additional transportation equipment and routes are not required for the construction of the connecting air duct 3 at this location; after the excavation of the connecting air duct 3 above the pilot tunnel 6 is completed, the section of the pilot tunnel 6 where the first node is located is used for support, which can seal and block the connection between the connecting air duct 3 and the pilot tunnel 6 at the first node and form a sufficiently reliable support structure. Subsequently, during the excavation of the connecting air ducts 3 between the second node and the first node and between the third node and the first node, the completed pilot tunnel 6 will not be affected (on the one hand, it is to prevent the excavated muck from entering the pilot tunnel 6, and on the other hand, it enables the pilot tunnel 6 to resist the blasting vibration during the excavation process at this location).

[0043] Embodiment 3: As Figure 6 shown, this embodiment is based on Embodiment 2, and the difference is that in this embodiment: Both the first driving tunnel 7 and the second driving tunnel 5 are excavated by the manual drill and blast method, and the two-bench construction method is adopted during the excavation process; The construction of the connecting air duct 3 above the first driving tunnel 7 includes: When the first driving tunnel 7 is excavated to a position 20 m away from the preset depth, the three-bench construction method is switched to continue the forward excavation. Among them, the construction process of the uppermost bench is as follows: First, excavate forward to the position of the excavation side line of the connecting air duct 3, and then conduct shallow-hole weak blasting backward to the position of the other side line of the connecting air duct 3 to form the heading face of the connecting air duct 3 at the second node. It should be understood that the above-mentioned "excavation side line" refers to the side line of the connecting air duct deeper at the second node; Preferably, after the first driving tunnel 7 is excavated to a position 10 m away from the preset depth, during the continuous excavation towards the preset depth, a construction preparation area with an upward excavation slope of 1:10 is excavated.

[0044] During the construction of the connecting air duct 3 above the first driving tunnel 7, by changing the original two-bench construction method to the three-bench construction method when excavating to a position 20 m away from the preset depth, the integrity of the surrounding rock of the first driving tunnel 7 at the second node can be ensured as much as possible, and thus the subsequent support requirements will not be increased, and it can be ensured that the cross-sectional size of the first driving tunnel 7 does not shrink at this position; excavating the above-mentioned construction preparation area with a slope of 1:10 facilitates the roof excavation of the connecting air duct 3 above the first driving tunnel 7, and facilitates the rapid formation of the excavation working face of the three-bench construction method, and is also convenient for the subsequent secondary lining concrete pouring in the arch crown range of the first driving tunnel 7 at this position.

[0045] Similarly, the construction of the connecting air duct 3 above the second vehicle tunnel 5 includes: When the second vehicle tunnel 5 is excavated to a position 20 m away from the preset depth, the three-step construction method is switched to continue the forward excavation. Among them, the construction process of the uppermost step is as follows: First, excavate forward to the position of the excavation side line of the connecting air duct 3, and then conduct shallow-hole weak blasting backward to the position of the other side line of the connecting air duct 3 to form the heading face of the third-node connecting air duct 3.

[0046] Preferably, after the second vehicle tunnel 5 is excavated to a position 10 m away from the preset depth, during the continuous excavation towards the preset depth, a construction preparation area with an upward excavation slope of 1:10 is excavated.

[0047] During the construction of the connecting air duct 3 above the second vehicle tunnel 5, by changing the original two-step construction method to the three-step construction method when excavating to a position 20 m away from the preset depth, the integrity of the surrounding rock of the second vehicle tunnel 5 at the third-node position can be ensured as much as possible. Furthermore, the subsequent support requirements will not be increased, and it can be ensured that the cross-sectional dimension of the second vehicle tunnel 5 does not shrink at this position; excavating the above-mentioned construction preparation area with a slope of 1:10 can facilitate the roof lifting of the connecting air duct 3 above the second vehicle tunnel 5, and facilitate the rapid formation of the excavation working face of the three-step construction method, and is also convenient for the subsequent secondary lining concrete pouring in the vault range of the second vehicle tunnel 5 at this position.

[0048] Preferably, the construction of the connecting air duct 3 from the second node towards the first node includes: After the connecting air duct 3 is constructed above the first vehicle tunnel 7 to form the second node, the designed excavation contour line of the connecting air duct 3 connecting the first node and the second node is lofted along the normal direction of the heading face of the connecting air duct 3 at the second node, and excavation and support are carried out along this contour line; Similarly, the construction of the connecting air duct 3 from the third node towards the first node includes: After the connecting air duct 3 is constructed above the second vehicle tunnel 5 to form the third node, the designed excavation contour line of the connecting air duct 3 connecting the first node and the third node is lofted along the normal direction of the heading face of the connecting air duct 3 at the third node, and excavation and support are carried out along this contour line; Similarly, the construction of the connecting air duct 3 from the fan room 2 towards the third node includes: Determine the contour of the heading face of the connecting air duct 3 on one side wall of the fan room 2, loft the designed excavation contour line of the connecting air duct 3 connecting the fan room 2 and the third node, and excavation and support are carried out along this contour line; obviously, the contour of the heading face of the connecting air duct 3 is determined on the side wall of the fan room 2 facing the third node; Among them, during the excavation along the excavation contour line designed for the connecting air duct 3, full-face construction is adopted in the section with intact surrounding rock, and the two-bench method is adopted in the section with broken surrounding rock.

[0049] Accordingly, during the construction of the connecting air duct 3 from the second node towards the first node, from the third node towards the first node, and from the fan room 2 towards the third node, by dynamically adjusting the excavation strategy (i.e., full-face construction and the two-bench method) based on the integrity of the surrounding rock, it is possible to shorten the construction period of the connecting air duct 3 operation as much as possible on the premise of ensuring the safety of the construction process, and thus realize the ventilation and air change of the first driving tunnel 7 and the second driving tunnel 5 earlier.

[0050] Preferably, the construction from the fan room 2 towards the third node includes: After the excavation and support are completed at the first node, the second node, and the third node, an un-tracked stepping hydraulic jumbo is used to carry out the secondary lining construction from the fan room 2 towards the third node.

[0051] Specifically, the secondary lining of the completed-excavation connecting air duct 3 includes: A Class III lining structure is adopted in the section with intact surrounding rock of the connecting air duct 3, and a Class IV lining structure is adopted in the section with broken surrounding rock of the connecting air duct 3.

[0052] It should be understood that the initial support during the excavation of the connecting air duct 3 should also refer to the degree of fragmentation of the surrounding rock, and a Class III lining structure is adopted in the section with intact surrounding rock, and a Class IV lining structure is adopted in the section with broken surrounding rock of the connecting air duct 3.

[0053] The above-mentioned specific implementation manners have further elaborated on the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above is only the specific implementation manners of the present invention and is not used to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A connecting air duct spanning three tunnels, the three tunnels comprising a first vehicle tunnel (7), a second vehicle tunnel (5) and a horizontal guide (6) which are parallel to each other; characterized in that: The first vehicle tunnel (7) and the second vehicle tunnel (5) have the same elevation, the connecting air duct (3) is horizontally arranged above the three tunnels, and the axial direction of the connecting air duct (3) is perpendicular to the axial direction of the first vehicle tunnel (7); the distance between the bottom surface of the connecting air duct (3) and the axis of the first vehicle tunnel (7) is less than the radius of the first vehicle tunnel (7); The first vehicle tunnel (7) and the second vehicle tunnel (5) are both connected to the connecting air duct (3).

2. The connecting air duct according to claim 1, characterized in that: A fan room (2) is also provided on one side of the three holes, and a ventilation shaft (1) is also provided on a side of the fan room (2) away from the three holes; The connecting air duct (3) is in communication with the fan room (2), and the fan room (2) is in communication with the ventilation shaft (1).

3. The connecting air duct according to claim 2, characterized in that: The distance between the bottom surface of the connecting air duct (3) and the road surface of the first driving tunnel (7) after completion is greater than the height required for driving in the first tunnel.

4. A construction method for a connecting air duct spanning three tunnels, used to construct the connecting air duct as claimed in claim 2 or 3, characterized in that: include: S1, after excavating the flat guide (6) to a preset depth, constructing a connecting air duct (3) above the flat guide (6) at the preset depth to form a first node; S2, after excavating the first vehicle tunnel (7) to the preset depth, constructing a communication air duct (3) above the first vehicle tunnel (7) at the preset depth position to form a second node; after excavating the second vehicle tunnel (5) to the preset depth, constructing a communication air duct (3) above the second vehicle tunnel (5) at the preset depth position to form a third node; S3, constructing a communication air duct (3) from the second node toward the first node, so that the first node and the second node are connected; constructing a communication air duct (3) from the third node toward the first node, so that the first node and the third node are connected; S4, constructing a connecting air duct (3) from the fan room (2) toward the third node, so that the third node and the fan room (2) are connected, and the excavation work of the connecting air duct (3) is completed; S5, performing secondary lining construction on the excavated connecting air duct (3) to form the connecting air duct (3).

5. The connecting air duct construction method according to claim 4, characterized in that: The horizontal guide (6) is excavated by an open TBM, the first vehicle tunnel (7) and the second vehicle tunnel (5) are both excavated by a drilling and blasting method, and the horizontal guide (6) is excavated before the first vehicle tunnel (7) and the second vehicle tunnel (5).

6. The connecting air duct construction method according to claim 5, characterized in that: The construction of the connecting air duct (3) above the flat guide (6) is carried out by adopting a three-step construction method; comprising: S11, after the horizontal guide (6) is excavated to a preset depth by the TBM, the TBM is stopped and a construction platform (11) is set up on top of the stopped TBM main beam; S12, starting the TBM to excavate forward 1.8 m and then stopping, and constructing the first step (10) on the surrounding rock in a 1.8 m length direction exposed by the excavation on the construction platform (11); S13, repeat S12 until the construction of the first step (10) is completed; S14, after the construction of the first step (10) is completed, the second step (9) and the third step (8) above the first step (10) are constructed in sequence to complete the excavation work of the first node; S15, supporting the flat guide (6) section at the location of the first node; Wherein, the supporting of the flat guide (6) section at the location of the first node comprises: S151, arranging a steel arch frame (13) at an opening position below the first node, wherein the steel arch frame (13) covers the exposed opening below the first node; S152, laying a steel plate layer (12) between the opening below the first node and the steel arch frame (13), supporting the steel plate layer (12) by the steel arch frame (13), the steel plate layer (12) being used to block the opening below the first node; S153, spraying concrete in the area where the steel arch frame (13) is set to form an initial support system, and performing secondary lining with reinforced concrete below the initial support system.

7. The connecting air duct construction method according to claim 4, characterized in that: The first vehicle tunnel (7) and the second vehicle tunnel (5) are both excavated by manual drilling and blasting methods, and the excavation process adopts a two-step construction method; The construction of the connecting air duct (3) above the first driving tunnel (7) comprises: After excavating the first vehicle tunnel (7) to a position 20 m away from the preset depth, the three-step construction method is switched to continue excavating forward, wherein the construction process of the top step is as follows: First, excavate forward to the position of the side line of the excavation of the connecting air duct (3), and then excavate backward to the position of the other side line of the connecting air duct (3) by shallow eye weak blasting, so as to form the second node connecting air duct (3) face; The construction of the connecting air duct (3) above the second driving tunnel (5) includes: When the second vehicle tunnel (5) is excavated to a position 20 m away from the preset depth, the three-step construction method is switched to continue excavating forward, wherein the construction process of the top step is as follows: First, excavate forward to the position of the side line of the connecting air duct (3), and then excavate backward to the position of the other side line of the connecting air duct (3) by shallow eye weak blasting, so as to form the third node connecting air duct (3) face.

8. The connecting air duct construction method according to claim 4, characterized in that: The construction of the communication air duct (3) from the second node toward the first node includes: After the connecting air duct (3) is constructed above the first driving tunnel (7) to form a second node, a connecting air duct (3) design excavation contour line connecting the first node and the second node is laid out along the normal direction of the connecting air duct (3) at the second node, and excavation and support are carried out along the contour line; The construction of the communication air duct (3) from the third node toward the first node includes: After the connecting air duct (3) is constructed above the second driving tunnel (5) to form a third node, a designed excavation contour line of the connecting air duct (3) connecting the first node and the third node is laid out along the normal direction of the connecting air duct (3) at the third node, and excavation and support are carried out along the contour line; The construction of the communication air duct (3) from the fan room (2) toward the third node comprises: Determining the excavation face contour of the connecting air duct (3) on a side wall of the fan room (2), laying out a designed excavation contour line of the connecting air duct (3) connecting the fan room (2) and the third node, and excavating and supporting along the contour line; In the process of excavating along the designed excavation contour line of the connecting air duct (3), full-section construction is adopted in the section with intact surrounding rock, and the two-step method is adopted in the section with broken surrounding rock.

9. The connecting air duct construction method according to claim 4, characterized in that: The construction from the fan room (2) towards the third node comprises: After excavation and support are completed at the first node, the second node and the third node, a trackless step-type hydraulic trolley is used to carry out secondary lining construction from the fan room (2) to the third node.

10. The connecting air duct construction method according to claim 4, characterized in that: The secondary lining of the excavated connecting air duct (3) comprises: In the section of the connecting air duct (3) where the surrounding rock is intact, a Class III lining structure is adopted, and in the section of the connecting air duct (3) where the surrounding rock is broken, a Class IV lining structure is adopted.

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