Rapid construction method for excavating single-track railway tunnel into large-span double-track tunnel

Abstract

The invention discloses a rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel, the construction method is implemented in multi-track tunnel construction close to an existing tunnel, and a multi-track tunnel group comprises an existing first tunnel, an existing second tunnel, a third tunnel, a fourth tunnel and a fifth tunnel, the construction position of the construction method is the doubling position of a fifth tunnel and a second tunnel. The construction method comprises the following steps that S1, a construction channel is constructed; s2, excavation of an expanded excavation section; and S3, secondary lining construction of the expanding excavation section is conducted. The inclined shaft of the fourth tunnel is used for achieving ventilation during tunnel expanding excavation construction operation, the ventilation and construction on the side close to a tunnel portal can be conducted synchronously, and therefore the shutdown time of an existing tunnel can be shortened; the four sections with different spans are arranged, segmented excavation is carried out, disturbance of stress changes caused by too large fracture surface changes to a rock stratum is reduced, therefore, arrangement of long-time-consuming supports such as anchor cables can be effectively reduced, and expanding excavation construction time can be shortened conveniently.

Description

Technical Field

[0001] The invention belongs to the technical field of parallel construction in a railway tunnel group, and particularly relates to a rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel. Background Art

[0002] In order to meet the demand of traffic flow, the original single-track tunnel will be enlarged for increasing the traffic lanes and improving travel. At present, in the tunnel enlargement, the original tunnel will not be abandoned, so the overall enlargement is relatively convenient and the process is relatively simple. However, in a tunnel group with a newly-built tunnel and an existing tunnel, not only does the existing tunnel overlap with the newly-built tunnel, but one end of the existing tunnel near the tunnel entrance needs to be abandoned, and a new section of tunnel is built at one end to connect with the end of the abandoned tunnel far from the tunnel entrance. There is also a situation where the newly-built tunnel needs to be merged into the end of the abandoned tunnel far from the tunnel entrance. Therefore, the excavation situation at the merging position is complex. Currently, it is necessary to wait for the new section of the abandoned tunnel to be connected with the original section before carrying out the excavation. This construction method takes a long time as a whole, resulting in a long shutdown time of the existing tunnel, thus affecting travel. Summary of the Invention

[0003] The invention intends to propose a rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel, which can realize the synchronous construction of the enlarged section and the section near the tunnel entrance, so as to quickly realize the opening to traffic after the reconstruction of the existing tunnel, reduce the shutdown time of the existing tunnel, and ensure travel.

[0004] For this reason, the technical solution adopted by the invention is as follows: A rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel, the construction method is implemented in the construction of a multi-track tunnel adjacent to an existing tunnel. The multi-track tunnel group includes the existing First Tunnel, Second Tunnel and the Third Tunnel, Fourth Tunnel, Fifth Tunnel to be constructed. Among them, the Third Tunnel is the new traffic tunnel after one end of the Second Tunnel near the tunnel entrance is abandoned. The Fourth Tunnel overlaps with the Second Tunnel at one end near the tunnel entrance. The First Tunnel, Third Tunnel, and Fourth Tunnel are arranged side by side. The tunnel entrance of the Fifth Tunnel is located on the side of the Fourth Tunnel far from the Third Tunnel, and one end of the Fifth Tunnel far from the tunnel entrance is merged into the Second Tunnel. The tunnel entrance of the Second Tunnel is located between the Third Tunnel and the Fourth Tunnel. The construction position of the construction method is the merging position of the Fifth Tunnel and the Second Tunnel;

[0005] The construction method includes the following steps:

[0006] S1: Construction of the construction passage. A sixth construction passage communicating with the Second Tunnel is provided at the construction inclined shaft on the side closest to the entrance end of the Fourth Tunnel, and a ventilation component is arranged in the sixth construction passage and the Second Tunnel to enable ventilation of the excavation working face;

[0007] S2: Excavation of the enlarged section is carried out in sequence of the bifurcation section, the second largest span section, the large span section, the through section, and the switch machine section. Among them, the switch machine section is the section where turnouts are installed. The bifurcation section, the second largest span section, and the large span section are sections with different cross-sections in the direction of the turnout towards the tunnel entrance. And the spans of the switch machine section, the bifurcation section, the second largest span section, and the large span section increase in sequence. The through section is the section connected to the third tunnel. During the excavation of each section, advanced support is required.

[0008] S3: Secondary lining construction of the enlarged section. After a period of time when the excavation of the bifurcation section, the second largest span section, the large span section, and the through section is completed, the secondary lining and the trench are constructed in sequence. After a period of time when the excavation of the switch machine section is completed, the secondary lining and the trench of the switch machine section are constructed. And the secondary lining of the switch machine section and the through section is completed synchronously.

[0009] As an optimization in the above solution, in S2, the excavation of the switch machine section, the bifurcation section, and the second largest span section includes the following steps:

[0010] The first step: Under the condition of completing the advanced support, demolish the existing tunnel arch lining of the upper bench, and then excavate the upper bench on both the left and right sides and construct the initial support of the upper bench.

[0011] The second step: Demolish the existing tunnel side wall and invert of the lower part, and then excavate the middle and lower benches on both the left and right sides and construct the initial support of the middle and lower benches.

[0012] The third step: Excavate the invert part on both the left and right sides and construct the initial support of the invert. Then, when constructing the secondary lining, it is carried out in the order of the invert, the side wall, and the arch.

[0013] Further optimization, in S2, the excavation of the large span section includes the following steps:

[0014] The first step: Install advanced support conduits within the arch range of the existing tunnel, and then excavate the upper right bench. Meanwhile, set up upper bench vertical braces at the position on the left side close to the enlarged upper bench.

[0015] The second step: Excavate the upper left bench. Excavate the upper left bench in sections of 2 - 3m, and the upper left bench lags behind the upper right bench by 15m.

[0016] The third step: Excavate the middle bench. The right middle bench is excavated after lagging behind the upper left bench by 15m. Meanwhile, set up middle bench vertical braces and cross braces at the position on the left side close to the enlarged right middle bench. The left middle bench is carried out after the upper left bench is excavated by 15m.

[0017] The fourth step: Excavate the lower bench. Before excavation, remove the vertical braces and cross braces in sections of 2 - 3m. The lower right bench is excavated after lagging behind the right middle bench by 15m. The lower left bench is excavated after lagging behind the left middle bench by 15m.

[0018] Step 5: Construct the inverted arch. The initial support of the inverted arch is completed 2 - 3 days after the initial support of the lower left bench.

[0019] Further preferably, except for the inverted arch, additional locking foot anchor pipes are reinstalled on each steel frame after the excavation of each part is completed. At the same time, large arch feet are also added to each steel frame on the upper bench.

[0020] Further preferably, non - explosive excavation is adopted during the excavation process.

[0021] Further preferably, during the excavation of the second tunnel, the construction of the third tunnel, the fourth tunnel, and the fifth tunnel is carried out synchronously at one end close to the tunnel entrance.

[0022] Advantages of the present invention: By using the inclined shaft of the fourth tunnel, ventilation during the excavation operation of the expanded tunnel is realized, enabling it to be synchronized with the construction on the side close to the tunnel entrance. Thus, the opening to traffic after the reconstruction of the existing tunnel can be quickly achieved, reducing the outage time of the existing tunnel and ensuring travel. There are four paragraphs with different spans, and the excavation is carried out in sections, reducing the disturbance of the rock formation caused by the stress change due to excessive cross - section change. Therefore, the setting of supports with long construction times such as anchor cables can be effectively reduced, facilitating the reduction of the excavation construction time. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the multi - line tunnel in the present invention.

[0024] Figure 2 is Figure 1 a schematic diagram of each cross - section in

[0025] Figure 3 It is a construction schematic diagram of the present invention.

[0026] Figure 4 It is a schematic diagram of the air duct in the first stage.

[0027] Figure 5 It is a schematic diagram of the air duct in the second stage.

[0028] Figure 6 It is a schematic diagram of the air duct in the third stage.

[0029] Figure 7 It is a schematic diagram of the air duct when the construction of the third tunnel is completed.

[0030] Figure 8 It is a construction schematic diagram of the large - span section.

[0031] Reference numerals: First Tunnel - 1, Second Tunnel - 2, Third Tunnel - 3, Fourth Tunnel - 4, Fifth Tunnel - 5, First Construction Passage - 6, Second Construction Passage - 7, Third Construction Passage - 8, Fourth Construction Passage - 9, Fifth Construction Passage - 10, Sixth Construction Passage - 11, First Air Duct - 12, Second Air Duct - 13, Third Air Duct - 14, Fourth Air Duct - 15, Fifth Air Duct - 16, Sixth Air Duct - 17, Seventh Air Duct - 18, Ninth Air Duct - 20, Tenth Air Duct - 21, Eleventh Air Duct - 22, Twelfth Air Duct - 23. Detailed implementation manner

[0032] The present invention will be further described below through embodiments in conjunction with the accompanying drawings:

[0033] As Figure 1-8 shown, a rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel is implemented in the construction of a multi-track tunnel adjacent to an existing tunnel. As Figure 1 and Figure 2 shown, the multi-track tunnel is composed of the existing First Tunnel 1, Second Tunnel 2 and the Third Tunnel 3, Fourth Tunnel 4, Fifth Tunnel 5 to be constructed. Among them, the First Tunnel, Third Tunnel, and Fourth Tunnel are arranged side by side. The tunnel entrance of the Second Tunnel is located between the Third Tunnel and the Fourth Tunnel. The tunnel entrance of the Fifth Tunnel 4 is located on the side of the Fourth Tunnel away from the Third Tunnel. The end of the Fifth Tunnel far from the tunnel entrance merges into the merging point of the Second Tunnel and the Third Tunnel, that is, the main tunnel of the Fifth Tunnel merges with the Second Tunnel, and the adjacent distance between the two is small. The Fourth Tunnel and the Second Tunnel overlap at one end near the tunnel entrance. The Third Tunnel is a new traffic tunnel after the abandonment of the entrance section of the Second Tunnel near the tunnel entrance, that is, there is partial overlap between the entrance section of the Second Tunnel and the entrance section of the Fourth Tunnel. Therefore, the entrance section of the Second Tunnel needs to be abandoned. The construction position of the construction method is at the merging position of the Fifth Tunnel 5 and the Second Tunnel 2.

[0034] The specific construction method includes the following steps:

[0035] The first step: Construction of the construction passage. A Sixth Construction Passage communicating with the Second Tunnel is provided at the construction inclined shaft on the side closest to the entrance end of the Fourth Tunnel, and ventilation components are arranged in the Sixth Construction Passage and the Second Construction Passage to enable ventilation of the excavation working face.

[0036] The second step: Excavation of the excavation section. Excavation and primary support are carried out in sequence according to the bifurcation section, sub-large-span section, large-span section, through section, and switch machine section. The switch machine section is the section where the turnout is set. The bifurcation section, sub-large-span section, and large-span section are sections with different cross-sections in the direction of the turnout towards the tunnel entrance, and the spans of the switch machine section, bifurcation section, sub-large-span section, and large-span section increase in sequence. The through section is the section communicating with the Third Tunnel. During the excavation of each section, advanced support is required. AsFigure 3 As shown in the figure, the bifurcation section, the second-largest span section, the largest span section, and the through section are respectively marked as the Vb double-track turnout section, the second-largest span VK1 section, the largest span VK2 section, and the Vb-D single-track turnout.

[0037] Step 3: Construction of the secondary lining for the excavation expansion section. After a certain period of time has passed since the excavation of the bifurcation section, the second-largest span section, the largest span section, and the through section are completed, the construction of the secondary lining and the trench is carried out in sequence. After a certain period of time has passed since the excavation of the switch machine section is completed, the secondary lining and the trench of the switch machine section are constructed, and the secondary lining of the switch machine section and the through section is completed synchronously.

[0038] Among them, the switch machine section, the Vb double-track turnout section, the second-largest span VK1 section, and the Vb-D single-track turnout are all constructed by the bench cut method. The largest span VK2 section is constructed by the center diaphragm CD method. The secondary lining of the second-largest span VK1 section and the largest span VK2 section is constructed using a mobile full hall formwork combination. The Vb double-track turnout section is constructed using a secondary lining formwork trolley. The switch machine section and the Vb-D single-track turnout are constructed using a secondary lining formwork trolley with a set of trolley skeletons.

[0039] Among them, the excavation expansion of the Vb double-track turnout section, the second-largest span VK1 section, and the switch machine section includes the following steps:

[0040] Step 1: Under the advanced support of the previous cycle, demolish the existing tunnel arch lining of the upper bench, and then excavate and expand the upper bench on both the left and right sides, and construct the initial support for the upper bench.

[0041] Step 2: Demolish the existing tunnel side wall and invert of the lower part, and then excavate and expand the middle and lower benches on both the left and right sides, and construct the initial support for the middle and lower benches.

[0042] Step 3: Excavate and expand the invert part on both the left and right sides, construct the initial support for the invert, and then sequentially construct the invert lining, side wall, and arch lining.

[0043] During the construction process, the footage per cycle of the upper bench is not greater than two sets of arch frames, the footage per cycle of the middle and lower benches is not greater than three sets of arch frames, the excavation on both the left and right sides is staggered by three sets of arch frames, and the footage per cycle of the invert is not greater than five sets of arch frames.

[0044] As Figure 8 shown in the figure, the circled numbers in the figure are the excavation expansion sequence. The excavation expansion of the largest span VK2 section includes the following steps:

[0045] Step 1: Install advanced support conduits within the arch range of the existing tunnel, and then excavate the upper right bench. Synchronously, set up upper bench vertical struts at the position on the left side close to the excavation expansion of the upper bench. The vertical struts are steel rigid frames, and concrete is sprayed on the vertical struts to use them as the center diaphragm. When excavating and expanding the upper right bench, it is carried out in sections of 2 - 3 m until the excavation expansion of the entire upper right bench is completed.

[0046] Step 2: Excavation of the upper left bench. The upper left bench is excavated section by section at intervals of 2 - 3 m, and the upper left bench lags behind the upper right bench by 15 m.

[0047] Step 3: Excavation of the middle bench. The right middle bench is excavated after lagging behind the upper left bench by 15 m. Meanwhile, vertical struts and horizontal struts are set at the left side position of the excavation of the right middle bench. The left middle bench is excavated after the upper left bench has been excavated for 15 m.

[0048] Step 4: Excavation of the lower bench. Before excavation, the vertical struts and horizontal struts are removed section by section at intervals of 2 - 3 m. The lower right bench is excavated after lagging behind the right middle bench by 15 m, and the lower left bench is excavated after lagging behind the left middle bench by 15 m.

[0049] Step 5: Construction of the inverted arch. The initial support of the inverted arch is completed 2 - 3 days after the initial support of the lower left bench.

[0050] To ensure the overall support, except for the inverted arch, lock foot anchor pipes are added to each steel frame after the excavation of each part is completed. At the same time, large arch feet for preventing settlement are also added to each steel frame of the upper bench. The support of the cable bolts is cancelled during the excavation process, which can effectively reduce the construction time.

[0051] During the tunnel excavation process, it is necessary to monitor and measure the newly built tunnel and the existing tunnel, and adjust the corresponding construction according to the measurement results. When necessary, a temporary support of a steel section steel frame is set within 10 m of the existing lining near the excavation.

[0052] The ventilation components include a fan frame, a damper and a air isolation curtain set in the second tunnel. A forced draft fan is equipped outside the damper, and the other end of the forced draft fan is connected to the outside through the sixth construction passage 11 and the construction inclined shaft on the side closest to the tunnel entrance of the fourth tunnel.

[0053] To speed up the construction, ensure the construction progress and at the same time reduce the shutdown time, the construction of the third tunnel, the fourth tunnel and the fifth tunnel is carried out simultaneously at one end close to the tunnel entrance. As Figure 3 shown, the construction methods of the third tunnel, the fourth tunnel and the fifth tunnel are as follows:

[0054] Step 1: Construction of the construction passages. The first construction passage 6, the second construction passage 7, the third construction passage 8 and the fourth construction passage 9 are constructed synchronously along the tunnel entrance using the second tunnel. The first construction passage, the second construction passage and the third construction passage are all within the overlapping section of the fourth tunnel and the second tunnel. Among them, the first construction passage, the second construction passage and the third construction passage are all synchronously connected to the second tunnel, the third tunnel, the fourth tunnel and the fifth tunnel, and the fourth construction passage is connected to the second tunnel and the fourth tunnel. When constructing the construction passages, the fifth tunnel is simultaneously constructed inward from the tunnel entrance. At this time, the entry and exit of vehicles are all realized through the second tunnel.

[0055] The second step is to construct the third tunnel and the fifth tunnel. After the construction of the fifth tunnel from the point where it is connected to the first construction channel to the tunnel entrance is completed, the second tunnel from the point where it is connected to the first construction channel to the tunnel entrance is backfilled, and after the construction of the second construction channel is completed, the fifth tunnel is constructed toward the tunnel entrance through the second construction channel, so that the intersection of the fifth tunnel and the second construction channel to the tunnel entrance is completed first, so that after the tunnel entrance section of the second tunnel is backfilled, each construction channel can be passed through the fifth tunnel.

[0056] At the same time, after the construction of the fourth construction channel is completed, the fourth tunnel is constructed in the direction away from the tunnel entrance through the fourth construction channel, that is, construction is carried out inwards through the fourth construction channel until it is connected with the main tunnel.

[0057] At the same time, after the construction of the first construction channel, the second construction channel and the third construction channel is completed, the third tunnel is constructed inward through the first construction channel, the second construction channel and the third construction channel respectively, and the opening of the third tunnel is accelerated through the construction of multiple working surfaces.

[0058] The third step is the construction of the third tunnel, the fourth tunnel and the fifth tunnel. When the third tunnel is connected to the second tunnel through the third construction channel, backfill the second tunnel from the point where it is connected to the third tunnel to the point where it is connected to the fourth construction channel.

[0059] After the backfilling of the tunnel entrance section of the second tunnel is completed, that is, after the backfilling between the intersection with the first construction channel and the tunnel entrance is completed, the third tunnel is constructed inward from the tunnel entrance to complete the penetration of the third tunnel. After the third tunnel is penetrated, the rest of the entrance section of the second tunnel is backfilled.

[0060] After the backfilling of the tunnel entrance section of the second tunnel is completed, that is, after the backfilling between the intersection with the first construction channel and the tunnel entrance in the second tunnel is completed, construction is carried out from the tunnel entrance of the fourth tunnel inward until the construction of the fourth tunnel is completed, that is, it is connected with the main tunnel of the fourth tunnel.

[0061] After the construction between the second construction channel position and the tunnel entrance in the fifth tunnel is completed, the fifth tunnel continues to be constructed inward until it reaches the junction with the third tunnel and the second tunnel.

[0062] To further accelerate the construction progress, the fifth construction access 10 is also under simultaneous construction. The fifth construction access connects the second tunnel and the far end of the fourth tunnel away from the tunnel entrance, and the fifth construction access is located in the non-abandoned section of the second access. After the construction of the fifth construction access is completed, the fourth tunnel is constructed towards the tunnel entrance through the fifth construction access. To quickly reach the side of the second tunnel away from the tunnel entrance, a sixth construction access 11 connecting to the second tunnel is provided at the construction inclined shaft on the side closest to the inlet end of the fourth tunnel. To quickly achieve the breakthrough of the fifth tunnel, when constructing the inner side of the second construction access in the fifth tunnel, the fifth tunnel is simultaneously constructed towards the merging position of the fifth tunnel and the third tunnel through the third construction access.

[0063] In the construction of the new tunnels, mechanical excavation is adopted for the excavation and advancement of the third tunnel, the fourth tunnel, and the fifth tunnel. Meanwhile, when constructing the third tunnel, the invert and filling follow the excavation and advancement of the heading face. Except for the section between the connection with the first construction access and the tunnel entrance, the secondary lining construction of the rest is carried out after the third tunnel is connected to the second tunnel at the tunnel entrance. When constructing the fifth tunnel, except for the section between the connection with the first construction access and the tunnel entrance, the secondary lining construction of the rest is carried out with multiple working faces after the secondary lining of the third tunnel is completed. When constructing the fourth tunnel, except for the section between the connection with the first construction access and the tunnel entrance, the secondary lining construction of the rest is carried out after the fourth tunnel is connected to the main tunnel.

[0064] Since the second tunnel is a single-track tunnel and the fourth tunnel is a double-track tunnel, there will be a section of the second tunnel completely located inside the fourth tunnel. When the second tunnel is completely within the contour of the fourth tunnel, no backfilling is required, and the rest of the parts need to be backfilled. In the backfilling of the second tunnel, for the part outside the contour of the third tunnel at the overlapping part of the second tunnel and the third tunnel, concrete is used for backfilling, and for the part inside the contour of the third tunnel, foamed lightweight soil is used for backfilling. From the position where the second tunnel and the third tunnel start to overlap to the position where the second tunnel completely leaves the fourth tunnel, a concrete retaining wall + foamed lightweight soil is used for backfilling. From the position where the second tunnel completely leaves the fourth tunnel to the position where the second tunnel is completely within the fourth tunnel, foamed lightweight soil is used for backfilling outside the contour of the fourth tunnel or the fourth construction access, and earth and stone are used for backfilling inside the contour. From the position where the second tunnel starts to be completely within the fourth tunnel to the tunnel entrance of the second tunnel, concrete is used for backfilling outside the contour of the fourth tunnel, and earth and stone are used for backfilling inside the contour.

[0065] During the entire construction process, since the first tunnel is adjacent to the third tunnel and the first tunnel is an existing tunnel, to reduce the impact on the first tunnel during the construction of the third tunnel, before the construction of the third tunnel, it is necessary to use the non-traffic time of the first tunnel to carry out corrugated plate lining and disease treatment for the third tunnel.

[0066] This construction method has been specifically implemented. At the tunnel entrance, the distance between the first tunnel and the third tunnel is 5.94 m, the distance between the third tunnel and the second tunnel is 0.54 m, the distance between the second tunnel and the fourth tunnel is 0.75 m, and the distance between the fourth tunnel and the fifth tunnel is 2.14 m. The distances between adjacent tunnel entrances, the first construction passage, the second construction passage, and the third construction passage are between 200 and 300 m. The overall construction length of the third tunnel is 1245 m, of which 966 m on the side close to the tunnel entrance is constructed from the tunnel entrance inward, and the other 264 m is the excavation-expanded section in this application.

[0067] When the first tunnel is excavated first and then the second tunnel is realigned and incorporated into the first tunnel, the first tunnel needs to be out of service for 12 months in the early stage, and the second tunnel needs to be out of service for 21 months in the later stage, with a total outage of 33 months. After adopting this construction method, the first tunnel does not need to be modified, and only the second tunnel needs to be out of service for 9.4 months. When the third tunnel is completed, although the new tunnel is not fully completed, the third tunnel can be opened to traffic, that is, the existing line can be opened to traffic. Therefore, the overall outage time is short, reducing the impact on travel.

[0068] During the entire construction process, multiple working faces will be set up in the tunnel group, specifically: the tenth working face facing the third tunnel is set at one end of the second tunnel far from the tunnel entrance. Inside the third tunnel, the fifth working face, the first working face, the second working face, and the third working face are successively arranged from the tunnel entrance inward. Inside the fourth tunnel, the seventh working face and the fourth working face are successively arranged from the tunnel entrance inward. At the same time, the ninth working face constructed through the fifth construction passage is set in the fourth tunnel. The sixth working face is arranged in the fifth tunnel from the tunnel entrance inward. The first working face is connected to the first construction passage, the second working face is connected to the second construction passage, the third working face is connected to the third construction passage, and the fourth working face is connected to the fourth construction passage.

[0069] To accelerate the penetration of the fifth tunnel, the eighth working face is also set in the fifth tunnel to construct towards the merging position of the fifth tunnel and the third tunnel through the third construction tunnel. The fifth construction passage 10 connecting the second tunnel and the fourth tunnel is set at one end of the second tunnel far from the tunnel entrance. Correspondingly, the ninth working face constructed through the fifth construction passage is set in the fourth tunnel. The tenth working face facing the third tunnel is set at one end of the second tunnel far from the tunnel entrance. The ventilation of the ninth working face and the tenth working face is realized through the ventilation components arranged in the second tunnel. The first working face to the tenth working face are the circled numbers as shown in Figure 3 the figure, and the numbers are the corresponding working faces.

[0070] To ensure the ventilation of each working face, the ventilation layout structure during the entire construction stage includes a number of forced draft fans, a number of jet fans, and a number of air isolation curtains. The forced draft fans achieve the ventilation of the corresponding working face through the corresponding air ducts. The jet fans are arranged at the intersections or turning parts between the tunnels, and the distance between adjacent jet fans is between 400 - 500 m. The air isolation curtains are arranged at the intersection positions between the second tunnel and the other tunnels. Through the forced draft fans and the air ducts corresponding to each working face, and the air ducts change with the construction progress, the ventilation of each working face is achieved, thus ensuring the overall ventilation effect; jet fans are arranged at the intersections or turning parts of the tunnels to ensure the discharge of the polluted air in the tunnels. At the same time, air isolation curtains are arranged to block the polluted air and prevent it from affecting the ventilation effect by cross - flow.

[0071] Among them, the air ducts are set according to the specific construction segments. Specifically, the air ducts include air ducts in four stages. Among them, the air ducts in the first stage are as Figure 4 shown, and are used to achieve the ventilation during the construction of the third tunnel, the fourth tunnel, and the fifth tunnel after the construction of each construction passage is completed. It includes the first air duct 12, the second air duct 13, and the third air duct 14 that are respectively connected to the forced draft fans. The first air duct is set as an air pipe extending along the fifth tunnel to the sixth working face. At the same time, the first air duct is paralleled with an air pipe that extends to the first working face after passing through the first construction passage at the first construction passage. The second air duct is set as an air pipe that passes through the fourth construction passage from the tunnel entrance of the second tunnel and then extends to the fourth working face. At the same time, the second air duct is paralleled with an air pipe that extends to the third working face after passing through the third construction passage at the third construction passage. The third air duct is set as an air pipe that extends from the tunnel entrance of the second tunnel to the second working face. At the same time, to accelerate the penetration of the fifth tunnel from the tunnel entrance to the second construction passage, the third air duct is paralleled with an air pipe that extends to the opposite side of the sixth working face after passing through the second construction passage at the second construction passage.

[0072] As Figure 5As shown in the figure, the air ducts in the second stage are used to achieve ventilation during the construction of the third, fourth, and fifth tunnels after the backfilling of the side of the second tunnel near the tunnel entrance and the completion of the connection of the section from the tunnel entrance of the fifth tunnel to the first construction passageway. The air ducts include the fourth air duct 15, the fifth air duct 16, the sixth air duct 17, the seventh air duct 18, and the eighth air duct 19, which are respectively connected to the forced draft fans. The fourth air duct 15 is an air duct extending along the fifth tunnel 5 to the sixth working face. At the same time, the fourth air duct 15 is paralleled at the first construction passageway 6 by an air duct that extends to the first working face after passing through the first construction passageway 6. The fifth air duct 16 is an air duct that passes through the first construction passageway 6 and the fourth construction passageway 9 from the tunnel entrance of the fifth tunnel 5 and then extends to the fourth working face. At the same time, the fifth air duct 16 is paralleled at the third construction passageway 8 by an air duct that extends to the third working face after passing through the third construction passageway 8. The seventh air duct 18 is an air duct extending from the tunnel entrance of the fourth tunnel 4 to the seventh working face. The eighth air duct 19 is an air duct extending from the tunnel entrance of the third tunnel 3 to the fifth working face. The sixth air duct 17 is an air duct that passes through the first construction passageway 6 from the tunnel entrance of the fifth tunnel and extends to the second working face. At the same time, to accelerate the connection of the fifth tunnel from the tunnel entrance to the second construction passageway, the sixth air duct 17 is paralleled at the second construction passageway 7 by an air duct that extends to the opposite side of the sixth working face after passing through the second construction passageway 7.

[0073] As Figure 6 shown in the figure, the air ducts in the third stage are used to achieve the connection of multiple working faces on the third tunnel and the ventilation during the construction of the fourth and fifth tunnels after the completion of the connection of the section from the tunnel entrance of the fifth tunnel to the second construction passageway. The air ducts include the ninth air duct 20, the tenth air duct 21, and the eleventh air duct 22, which are respectively connected to the forced draft fans. The ninth air duct 20 is an air duct extending along the fifth tunnel 5 to the sixth working face. The tenth air duct 21 is an air duct that passes through the second construction passageway 7 and the fourth construction passageway 9 from the tunnel entrance of the fifth tunnel 5 and then extends to the fourth working face. The eleventh air duct 22 is an air duct extending along the fourth tunnel 4 to the seventh working face. To accelerate the connection of the fifth tunnel, it also includes the fourteenth air duct 25, which is an air duct that passes through the second construction passageway 7 and the third construction passageway 8 from the tunnel entrance of the fifth tunnel 5 and then extends to the eighth working face.

[0074] As Figure 7 shown in the figure, the fourth stage is for ventilation during the construction of the fourth tunnel after the fifth tunnel is connected. The air ducts include the twelfth air duct 23 and the thirteenth air duct 24, which are respectively connected to the forced draft fans during the pressing process. Among them, the forced draft fan of the twelfth air duct 23 is set at the span position of the fifth tunnel. The twelfth air duct 23 is an air duct connected to the corresponding forced draft fan and extending to the fourth working face after passing through the third construction passageway 8 and the fourth construction passageway 9. The thirteenth air duct 24 is an air duct extending along the fourth tunnel 4 to the seventh working face.

[0075] The forced draft fans in different stages can be reused, that is, the same forced draft fan can be connected to the air ducts in different stages. For example, the first air duct, the fourth air duct, and the ninth air duct are all supplied with air by the same forced draft fan. For the convenience of management, the forced draft fans located outside the tunnel are arranged adjacent to each other. Preferably, they are all arranged near the fifth tunnel.

[0076] Due to the existence of multiple working faces, the amount of muck discharged is large. To reduce the muck discharging pressure and prevent the construction progress from being affected by muck discharging, reverse construction surfaces are carried out on the working surfaces of each construction passage so that they can serve as temporary muck storage points. Positioning monitoring equipment and traffic lights for ensuring smooth transportation are installed in the tunnel group.

[0077] To ensure dust removal and temperature reduction in the tunnel group, a water spray dust reduction device is configured on the excavation equipment, and fog guns can be set at reasonable positions near the heading face for secondary dust reduction by spraying. At the same time, a bag filter is installed for thorough dust reduction, and temporary intercepting and drainage ditches are arranged to collect and timely drain the construction water.

[0078] In summer, the operating environment temperature in the tunnel is high. The construction machinery and equipment have large power and long operating hours, generating a large amount of heat. Coupled with the limited space and poor air circulation in the tunnel, it is difficult to meet the requirements of a suitable internal environment in the tunnel only by ventilation and cooling, which is not conducive to construction such as personnel and equipment. A special tunnel skid-mounted water-cooled unit TSWCC-630H is equipped on-site for cooling.

Claims

1. A rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel, characterized in that, The described construction method is implemented in the construction of a multi-line tunnel adjacent to an existing tunnel. The multi-line tunnel group includes the existing First Tunnel (1), Second Tunnel (2), and the Third Tunnel (3), Fourth Tunnel (4), and Fifth Tunnel (5) to be constructed. Among them, the Third Tunnel (3) is a new traffic tunnel after one end of the Second Tunnel (2) near the tunnel entrance is abandoned. The Fourth Tunnel (4) overlaps with the Second Tunnel (2) at one end near the tunnel entrance. The First Tunnel (1), Third Tunnel (3), and Fourth Tunnel (4) are arranged side by side. The tunnel entrance of the Fifth Tunnel (5) is located on the side of the Fourth Tunnel (4) away from the Third Tunnel (3), and one end of the Fifth Tunnel (5) away from the tunnel entrance merges into the Second Tunnel (2). The tunnel entrance of the Second Tunnel (2) is located between the Third Tunnel (3) and the Fourth Tunnel (4). The construction position of the described construction method is at the merging position of the Fifth Tunnel (5) and the Second Tunnel (2); The described construction method includes the following steps: S1: Construction of the construction access. At the construction inclined shaft on the side closest to the entrance end of the Fourth Tunnel (4), there is a Sixth Construction Access (11) connected to the Second Tunnel (2), and ventilation components are provided in the Sixth Construction Access (11) and the Second Tunnel (2) to enable ventilation of the excavation working face; S2: Excavation of the enlarged section. Excavation and primary support are carried out in sequence according to the bifurcation section, sub-large-span section, large-span section, through section, and switch machine section. Among them, the switch machine section is the section where turnouts are set. The bifurcation section, sub-large-span section, and large-span section are sections with different cross-sections in the direction of the turnout towards the tunnel entrance, and the spans of the switch machine section, bifurcation section, sub-large-span section, and large-span section increase in sequence. The through section is the section connected to the Third Tunnel (3). During the excavation of each section, advanced support is required; S3: Secondary lining construction of the enlarged section. After a period of time after the excavation of the bifurcation section, sub-large-span section, large-span section, and through section is completed, secondary lining and trench construction are carried out in sequence. After a period of time after the excavation of the switch machine section is completed, secondary lining and trench construction are carried out on the switch machine section, and the secondary lining of the switch machine section and the through section are completed synchronously.

2. The rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel as described in claim 1, wherein: In S2, the excavation of the switch machine section, bifurcation section, and sub-large-span section includes the following steps: The first step: Under the condition of completing advanced support, demolish the lining of the arch part of the existing tunnel in the upper bench, and then excavate the upper bench on the left and right sides and construct the primary support of the upper bench; The second step: Demolish the side wall and inverted arch of the existing tunnel in the lower part, and then excavate the middle and lower benches on the left and right sides and construct the primary support of the middle and lower benches; The third step: Excavate the inverted arch part on the left and right sides and construct the primary support of the inverted arch. Then, when constructing the secondary lining, it is carried out in the order of the inverted arch, side wall, and arch part.

3. The rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel according to claim 1, wherein: In S2, the excavation of the large-span section includes the following steps: The first step: Install advanced support conduits within the arch range of the existing tunnel, and then excavate the upper right bench. At the same time, set up upper bench vertical struts at the position on the left side of the enlarged upper bench; The second step: Excavation of the upper left bench. Excavate the upper left bench section by section at 2 - 3m, and the upper left bench lags behind the upper right bench by 15m; Step 3: Excavate the middle bench. The right middle bench is excavated 15 m behind the left upper bench, and vertical struts and horizontal struts are arranged at the left side of the enlarged excavation of the right middle bench. The left middle bench is excavated 15 m after the excavation of the left upper bench. Step 4: Excavate the lower bench. Before excavation, the vertical struts and horizontal struts are removed section by section at intervals of 2 - 3 m. The right lower bench is excavated 15 m behind the right middle bench, and the left lower bench is excavated 15 m behind the left middle bench. Step 5: Construct the inverted arch. The initial support of the inverted arch is completed 2 - 3 days after the initial support of the left lower bench.

4. The rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel according to claim 3, characterized in that: Except for the inverted arch, additional locking foot anchor pipes are added to each steel frame after the enlarged excavation of each part. At the same time, large arch feet are also added to each steel frame of the upper bench.

5. The rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel as described in claim 1, characterized in that: During the enlarged excavation process, non-explosive excavation is adopted.

6. The rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel according to claim 1, characterized in that: During the enlarged excavation of the second tunnel, the construction of the third tunnel, the fourth tunnel, and the fifth tunnel is carried out synchronously at one end close to the tunnel entrance.

7. The rapid construction method for excavating a single-track railway tunnel into a large-span double-track tunnel according to claim 1, characterized in that: The ventilation assembly includes a fan frame, a damper, and an air separation curtain arranged in the second tunnel. A forced draft fan is equipped outside the damper, and the other end of the forced draft fan is communicated with the outside through the sixth construction passage (11) and the construction inclined shaft on the side closest to the tunnel entrance of the fourth tunnel.

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