Single line railway tunnel surrounding rock section center ditch construction method

Abstract

The application discloses a kind of single line railway tunnel surrounding rock section center ditch construction method, comprising the following steps: drilling and charging and center ditch deslagging are carried out;Inverted arch hydraulic trestle is retracted before approach bridge and does blasting protection;Face, inverted arch and center ditch are simultaneously blasted;Ventilation and smoke exhaust, inverted arch hydraulic trestle is lowered before approach bridge;Inverted arch and upper circulating center ditch excavator deslagging;Inverted arch initial spraying and center ditch construction;Face up and down step shotcreting, then inverted arch initial support shotcreting is carried out;Inverted arch excavation support and center ditch construction cycle;Inverted arch waterproofing construction, inverted arch reinforcement construction, inverted arch formwork installation, inverted arch concrete construction, inverted arch concrete waiting for strength, inverted arch filling construction;Next cycle inverted arch and center ditch construction, upper plate inverted arch filling curing waiting for strength.The construction method of the application can realize efficient connection during each assembly line construction, and shorten construction period.

Description

Technical Field

[0001] This invention belongs to the technical field of tunnel construction, and specifically relates to a method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel. Background Technology

[0002] Single-track railway tunnels, as an important component of railway transportation networks, are widely distributed in complex geological areas such as mountainous regions and plateaus. Among them, Class V surrounding rock sections, due to their characteristics of fractured rock mass, low degree of cementation, high water content, and poor self-stabilization capacity, become the most challenging areas in tunnel construction. Typically, a central drainage ditch is constructed at the bottom of the railway tunnel. This central ditch, as the core of the single-track railway tunnel's drainage system, plays a crucial role in channeling surface water and groundwater within the tunnel.

[0003] However, during the construction of the central drainage ditch in traditional single-track railway tunnels, spatial conflicts between work processes are prominent. The cross-sectional dimensions of single-track railway tunnels are usually small, and the construction of the central drainage ditch is carried out concurrently with processes such as face excavation, initial support, invert arch pouring, and muck removal within a limited space. The logistics channel and the work space highly overlap, which seriously affects the progress of construction. In addition, poor geological conditions and insufficient connection between construction processes can easily lead to earthwork collapse and construction accidents. Summary of the Invention

[0004] This invention provides a method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel, in order to solve the problem of low construction efficiency due to overlapping operations of various processes during the construction of the central drainage ditch in a single-track railway tunnel.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel includes the following steps:

[0007] Step 1: Drill holes, load the explosive, and remove slag from the central drainage channel;

[0008] Step 2: The hydraulic trestle bridge of the inverted arch is retracted and blast protection is applied;

[0009] Step 3: Simultaneous blasting of the working face, invert, and central drainage ditch;

[0010] Step 4: Ventilate and exhaust smoke, lower the front approach bridge of the inverted arch hydraulic trestle bridge;

[0011] Step 5: Excavator removes slag from the invert arch and upper circulation center water ditch;

[0012] Step Six: Initial shotcreting of the invert arch and backfilling of the central drainage ditch with over-excavated concrete; installation of concrete pipes and insulation boards for the central drainage ditch and treatment of joints; cast-in-place casting of the central drainage ditch foundation; installation of the central drainage ditch water guide pipe; backfilling of the central drainage ditch with graded crushed stone and top surface protection; installation of the invert arch steel frame; slag removal from the upper and lower steps of the working face; erection of the mesh frame for the upper and lower steps of the working face; locking the upper and lower steps of the working face, system anchor bolts, and advanced construction.

[0013] Step 7: Shotcrete the upper and lower steps of the working face, and then shotcrete the initial support of the invert arch;

[0014] Step 8: Cycle of excavation and support of the invert arch and construction of the central drainage ditch;

[0015] Step Nine: Invert arch drainage construction, invert arch reinforcement construction, invert arch formwork installation, invert arch concrete construction, invert arch concrete reinforcement, and invert arch filling construction.

[0016] Step 10: Construction of the invert arch and central drainage ditch in the next cycle, followed by filling and curing of the upper invert arch.

[0017] Furthermore, step one includes the following steps:

[0018] Drill holes and load explosives on the upper and lower steps of the working face, and remove slag in the central ditch; drill holes and load explosives 42m ahead of the lower step of the working face in the invert arch, drill holes and load explosives 8m ahead of the invert arch in the central ditch in the longitudinal direction, and drill holes and load explosives 5m ahead of the vertical pre-splitting of the invert arch in the longitudinal direction.

[0019] Simultaneous construction of "drilling and loading explosives on the upper and lower steps of the working face" and "slag removal in the central ditch"; simultaneous construction of "drilling and loading explosives 42m ahead of the inverted arch, offset longitudinally from the lower step of the working face" and "drilling and loading explosives 8m ahead of the central ditch, offset longitudinally from the inverted arch, vertical pre-splitting blasting blasting blasting blasting blasting 5m ahead of the central ditch" and "drilling and loading explosives blasting ...5m ahead of the inverted arch".

[0020] Furthermore, the time for the process of "drilling and loading explosives on the upper and lower steps of the working face" is X, the time for the process of "removing slag from the central ditch" is Y, and the time for the processes of "drilling and loading explosives 42m ahead of the lower step of the working face" and "drilling and loading explosives 8m ahead of the vertical pre-splitting of the central ditch and 5m ahead of the vertical lifting blasting" are both Z, satisfying X≥Y+Z.

[0021] Furthermore, a parallel operation mode was adopted for the central drainage ditch under the double trestle bridge and the invert arch lining, and an independent operation zone for the central drainage ditch was added between the working face and the invert arch lining.

[0022] Furthermore, when there is a conflict between the logistics of the central drainage ditch operation section and the working face operation section and the invert arch operation section, priority should be given to ensuring the backfilling of the central drainage ditch.

[0023] Furthermore, for the central ditch section formed by blasting, if there is over-excavation, it is treated by backfilling with C25 shotcrete and manual trimming.

[0024] Furthermore, for the construction of central drainage ditches in unfavorable areas, mobile supports that match the external excavation dimensions of the central drainage ditches are made using materials such as I-beams, steel pipes, and steel plates. After the central drainage ditches are excavated, they are hoisted into the trench by an excavator, and then the central drainage ditches are constructed inside the mobile supports.

[0025] Once the construction of the central drainage ditch in this cycle is completed, the excavator will be used to longitudinally move the support frame for the next cycle of construction.

[0026] Furthermore, if the geological conditions ahead are extremely poor and monitoring indicates that the deformation of the surrounding rock support is large, pre-reinforcement should be carried out in the central ditch area of ​​this section 7 days in advance.

[0027] A down-the-hole drill was used to excavate along the outer contour line on both sides of the central ditch and longitudinally install φ76 steel pipes at 1m intervals in a quincunx pattern, and then inject 1:1 cement slurry.

[0028] Furthermore, in step eight, the excavation areas of the invert arch and the central ditch are constructed longitudinally in a staggered manner.

[0029] Furthermore, to address the issue of increased sidewall deformation after the excavation of the central drainage ditch, the timing of the central drainage ditch excavation should be strictly controlled. Specifically, the central drainage ditch can be excavated when the strength of the initial shotcrete support of the arch wall and the strength of the anchor grout reach more than 80%.

[0030] The present invention can achieve the following beneficial effects:

[0031] 1. The construction method of this application divides the tunnel longitudinally into only the excavation and support operation area, the central ditch and invert arch operation area, and the secondary lining operation area, which reduces the difficulty of overlapping procedures and logistics organization; after excavation, the central ditch, which has a longer total operation time, is prioritized for slag removal, which effectively balances the operation efficiency with the excavation and support area at the tunnel face and reduces the overall operation efficiency and operation time.

[0032] 2. After the central drainage ditch is constructed, the initial support protection of the invert arch is applied promptly, eliminating the risk of damage from secondary excavation to create a channel. The vertical grouting pre-reinforcement work using steel pipes has ample space and time, the technology is mature, and the quality is controllable.

[0033] 3. In sections where the surrounding rock is difficult to stabilize after the excavation of the central drainage ditch, vertical grouting with steel pipes was used for pre-reinforcement to ensure the safety of the central drainage ditch foundation pit excavation; in terms of construction organization, the central drainage ditch was prioritized to ensure that the initial support of the invert arch was closed into a ring as soon as possible to control tunnel deformation. Attached Figure Description

[0034] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0035] Figure 1 This is a schematic flowchart of a construction method for a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to the present invention.

[0036] Figure 2 This is a cross-sectional view of the construction of the longitudinal section of the drainage ditch according to the present invention;

[0037] Figure 3 This is a longitudinal unfolded diagram of the construction steps of the central drainage ditch in the construction method of the present invention;

[0038] Figure 4 This is a diagram illustrating the layout effect when using steel pipe pile protection method to reinforce the soil on both sides of the central ditch according to the present invention. Detailed Implementation

[0039] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0040] A method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel, such as... Figures 1 to 4 The following steps are specifically included in one particular embodiment:

[0041] Step 1: Drill holes and load explosives on the upper and lower steps of the working face, advancing 1.6m per cycle, taking 4 hours; remove slag from the central ditch, taking 1 hour; drill holes and load explosives 42m forward longitudinally, offset from the lower step of the working face, taking 3 hours; drill holes and load explosives 8m forward longitudinally, offset from the inverted arch, and drill holes and load explosives 5m longitudinally, advancing 3m per cycle; follow up continuously for 4 cycles every 12m of working face construction, taking 3 hours.

[0042] In this process, while performing "drilling and charging at the upper and lower steps of the working face," the "slag removal from the central ditch" is carried out simultaneously. After the "slag removal from the central ditch" is completed, the "drilling and charging 42m ahead of the invert, staggered longitudinally from the lower step of the working face" and the "drilling and charging 8m ahead of the central ditch, staggered longitudinally from the invert, vertical pre-splitting, and 5m ahead of the central ditch, vertical pre-splitting, and 5m ahead of the central ditch, vertical lifting, and blasting" processes are performed simultaneously. By dividing the process into different sequential work sections, the different processes are carried out synchronously, so that step one in this embodiment only takes 4 hours. That is, the time for the "drilling and charging at the upper and lower steps of the working face" process is X, the time for the "slag removal from the central ditch" process is Y, and the time for the "drilling and charging 42m ahead of the invert, staggered longitudinally from the lower step of the working face" and the "drilling and charging 8m ahead of the central ditch, vertical pre-splitting, and 5m ahead of the central ditch, vertical lifting, and blasting" processes are both Z, satisfying X≥Y+Z.

[0043] Step 2: The hydraulic trestle bridge of the invert arch is retracted and blast protection is applied, which takes 0.5 hours.

[0044] Step 3: Demolish the working face, invert arch, and central drainage ditch simultaneously.

[0045] Step 4: Ventilation and smoke extraction. The hydraulic trestle bridge with the inverted arch is lowered to the front approach bridge, which takes 0.5 hours.

[0046] Step 5: Excavator removes slag from the invert arch and upper circulation center water ditch, taking 2 hours.

[0047] Step Six: Initial shotcreting of the invert arch and over-excavation and backfilling of the central drainage ditch with shotcrete, taking 2 hours; installation of concrete pipes and insulation boards for the central drainage ditch and joint treatment, taking 3 hours; cast-in-place casting of the central drainage ditch base, taking 2 hours; installation of the central drainage ditch water guide pipe, taking 0.5 hours; backfilling of the central drainage ditch with graded crushed stone and top surface protection, taking 2.5 hours; installation of the invert arch steel frame, taking 2 hours; slag removal from the upper and lower steps of the working face, taking 6 hours; erection of the mesh frame for the upper and lower steps of the working face, taking 2 hours; locking the upper and lower steps of the working face, system anchor bolts, and advanced construction, taking 4 hours.

[0048] In this step, the following steps can be carried out simultaneously: "Initial spraying of the invert arch and over-excavation and backfilling of the central water ditch with shotcrete, taking 2 hours; installation of concrete pipes and insulation boards and joint treatment of the central water ditch, taking 3 hours; cast-in-place casting of the central water ditch base, taking 2 hours; installation of the central water ditch water pipe, taking 0.5 hours; backfilling of the central water ditch with graded crushed stone and top protection, taking 2.5 hours; installation of the invert arch steel frame, taking 2 hours" and "slag removal from the upper and lower steps of the working face, taking 6 hours; erection of the mesh frame for the upper and lower steps of the working face, taking 2 hours; locking the upper and lower steps of the working face, system anchor bolts, and advanced construction, taking 4 hours". Therefore, the total time for this step in this embodiment is 12 hours.

[0049] Step 7: Shotcrete the upper and lower steps of the working face, taking 2 hours; Shotcrete the initial support of the invert arch, taking 1 hour.

[0050] Step 8: Excavation and support of the invert arch and construction of the central drainage ditch (4 cycles, 12m each, totaling 88 hours). During this step, the excavation areas of the invert arch and the central drainage ditch are constructed longitudinally in a staggered manner.

[0051] Step 9: Drainage and waterproofing construction of the invert arch, taking 8 hours; reinforcement construction of the invert arch, taking 24 hours; installation of the invert arch formwork, taking 8 hours; concrete construction of the invert arch, taking 8 hours; concrete reinforcement of the invert arch, taking 8 hours; infill construction of the invert arch, taking 8 hours; total time for this step is 64 hours.

[0052] Step 10: Construction of the next cycle of invert arch and central water ditch (88+64=152h), and curing of the upper invert arch filling (48h, 24m long trestle bridge, which does not take up the process time).

[0053] Using the construction method of this application, the construction can be completed in just 174 hours from step one to step nine.

[0054] Under the same construction conditions, the construction steps of the traditional construction method are as follows:

[0055] Step 1: Drill holes and load explosives on the upper and lower steps of the working face, advancing 1.6m in a cycle, taking 4 hours. The invert arch turns back to provide the excavation working face, taking 1 hour. The invert arch moves forward longitudinally, offsetting the lower step of the working face by 42-54m, to drill holes and load explosives, taking 3 hours. This step takes a total of 4 hours.

[0056] Step 2: The hydraulic trestle bridge of the invert arch is retracted and blast protection is applied, which takes 0.5 hours.

[0057] Step 3: Detonate the working face and the invert simultaneously.

[0058] Step 4: Ventilation and smoke extraction. The hydraulic trestle bridge with the inverted arch is lowered to the front approach bridge, which takes 0.5 hours.

[0059] Step 5: Slag removal from the upper and lower steps of the working face, taking 6 hours; erection of the mesh frame for the upper and lower steps of the working face, taking 2 hours; locking the toe of the upper and lower steps of the working face, installing system anchors, and advanced construction, taking 4 hours; shotcreting the upper and lower steps of the working face, taking 2 hours; this process takes a total of 14 hours.

[0060] Step 6: Continuously construct the upper and lower steps on the working face for 7-8 cycles, approximately 12m, taking 133-152 hours.

[0061] Step 7: Approximately 12m of slag removal from the invert arch, taking 3 hours; 3m of vertical drilling and charging in the first cycle's central water ditch, taking 3 hours; blasting of the first cycle's central water ditch; slag removal in the first cycle's central water ditch, taking 1 hour; 3m of vertical drilling and charging in the second cycle's central water ditch, taking 3 hours; blasting of the second cycle's central water ditch; slag removal in the second cycle's central water ditch, taking 1 hour; 3m of vertical drilling and charging in the third cycle's central water ditch, taking 3 hours; blasting of the third cycle's central water ditch; slag removal in the third cycle's central water ditch, taking 1 hour; 3m of vertical drilling and charging in the fourth cycle's central water ditch, taking 3 hours; blasting of the fourth cycle's central water ditch; slag removal in the fourth cycle's central water ditch, taking 1 hour; This process takes a total of 19 hours.

[0062] Step 8: Initial shotcreting of the invert arch and over-excavation and backfilling of the central drainage ditch with shotcrete, taking 4 hours; installation of concrete pipes and insulation boards for the central drainage ditch and joint treatment, taking 8 hours; cast-in-place casting of the central drainage ditch base, taking 4 hours; installation of the central drainage ditch water pipe, taking 1 hour; backfilling of the central drainage ditch with graded crushed stone and top surface protection, taking 6 hours; installation of the invert arch steel frame, taking 8 hours; initial shotcreting of the invert arch support, taking 3 hours; this process takes a total of 34 hours.

[0063] Step 9: Drainage and waterproofing construction of the invert arch (8 hours); reinforcement construction of the invert arch (24 hours); installation of the invert arch formwork (8 hours); concrete construction of the invert arch (8 hours); concrete reinforcement of the invert arch (8 hours); infill construction of the invert arch (8 hours); total time for this process is 64 hours.

[0064] Step 10: Construction of the invert arch and central drainage ditch in the next cycle, followed by filling and curing of the upper invert arch.

[0065] Using traditional construction methods, it would take 250-269 hours to complete the construction from step one to step nine.

[0066] In contrast, the construction method of this application adopts a parallel operation of the central drainage ditch under the double trestle bridge and the invert arch lining, and adds an independent working area for the central drainage ditch between the working face and the invert arch lining. This integrates the construction process of the central drainage ditch with the working face excavation and invert arch construction processes, allowing each process to be carried out simultaneously and with closer coordination, thus shortening the construction period. Furthermore, when constructing according to the method of this application, the following procedures require adaptive adjustments.

[0067] When there is a material conflict between the central drainage ditch work section and the working face work section for shotcreting and the invert arch work section for concrete pouring, priority should be given to ensuring the backfilling of the central drainage ditch to achieve construction safety.

[0068] The central drainage ditch in the soil section is prone to softening when exposed to water. It is necessary to construct water collection wells at intervals on the side near the working face in advance for interception and drainage. If necessary, dewatering wells should be constructed to reduce water level. At the same time, after the trench is excavated, it should be sealed with shotcrete immediately to prevent soaking.

[0069] To address the issue of unstable slope along the central drainage ditch in the soft rock fractured section, the excavation slope ratio is controlled at 1:0.2. If necessary, a 10cm thick layer of C25 shotcrete is applied to the excavation slope of the V surrounding rock section.

[0070] Because the central drainage ditch in the rocky section was formed by blasting, over-excavation was prone to occur. A vertical pre-splitting and longitudinal lifting blasting technique was adopted to control the blasting operation, and drilling accuracy and the amount of explosives were strictly controlled to reduce over-excavation. When the central drainage ditch was over-excavated, the traditional method was to use formwork and C20 concrete backfill for the over-excavated portion. However, in high-altitude and cold regions, the concrete has a long curing time. Therefore, a new method of using C25 shotcrete backfill followed by manual finishing has been adopted to shorten the process time.

[0071] If the deformation of the sidewalls intensifies after the central drainage ditch is excavated, the anchoring parameters need to be strengthened, and the timing of the central drainage ditch excavation should be strictly controlled. That is, the central drainage ditch can only be excavated when the strength of the initial shotcrete of the arch wall and the anchoring grout reaches more than 80%.

[0072] When encountering areas with unfavorable geological conditions, the construction of the central drainage ditch can be carried out using the following three methods:

[0073] Mobile scaffolding method: A mobile scaffolding system matching the external excavation dimensions of the central ditch is prefabricated using materials such as I-beams, steel pipes, and steel plates. After the central ditch is excavated, an excavator is used to hoist the mobile scaffolding system into the trench, and then the central ditch is constructed within the mobile scaffolding system. After the construction of the central ditch in this cycle is completed, the mobile scaffolding system is dragged longitudinally by an excavator to begin the next cycle of construction.

[0074] Permanent support method: Prefabricate permanent support segments that match the external excavation dimensions of the central ditch. After the central ditch is excavated, use an excavator to hoist them into the trench, and then construct the central ditch within the support.

[0075] Steel pipe pile protection method: When the results of advanced geological forecasting reveal that the geological conditions ahead are extremely poor, and monitoring shows that the deformation of the surrounding rock support is large, the central ditch area of ​​the section should be pre-reinforced 7 days in advance to improve the physical and mechanical properties of the surrounding rock and the uniformity of stress distribution.

[0076] Specifically, a down-the-hole drill was used to excavate along the outer contour line on both sides of the central ditch, longitudinally installing φ76 steel pipes at 1m intervals in a quincunx pattern. The steel pipes were 5m long, extending 3m into the bottom of the ditch, and then filled with 1:1 cement slurry.

[0077] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Under the concept of the present invention, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of the present invention as described above. For the sake of brevity, they are not provided in detail. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel, characterized in that, Includes the following steps: Step 1: Drill holes, load the explosive, and remove slag from the central drainage channel; Step one includes the following steps: Drill holes and load explosives on the upper and lower steps of the working face, and remove slag in the central ditch; drill holes and load explosives 42m ahead of the lower step of the working face in the invert arch, drill holes and load explosives 8m ahead of the invert arch in the central ditch in the longitudinal direction, and drill holes and load explosives 5m ahead of the vertical pre-splitting of the invert arch in the longitudinal direction. "Drilling holes and loading explosives on the upper and lower steps of the working face" and "slag removal in the central ditch" are carried out simultaneously; "drilling holes and loading explosives 42m ahead of the inverted arch and longitudinally offset from the lower step of the working face" and "drilling holes and loading explosives 8m ahead of the central ditch and longitudinally offset from the inverted arch and longitudinally offset from the inverted arch and 5m ahead of the central ditch" are carried out simultaneously. Step 2: The hydraulic trestle bridge of the inverted arch is retracted and blast protection is applied; Step 3: Simultaneous blasting of the working face, invert, and central drainage ditch; Step 4: Ventilate and exhaust smoke, lower the front approach bridge of the inverted arch hydraulic trestle bridge; Step 5: Excavator removes slag from the invert arch and upper circulation center water ditch; Step Six: Initial shotcreting of the invert arch and backfilling of over-excavated concrete for the central drainage ditch; installation of concrete pipes and insulation boards for the central drainage ditch and treatment of joints; cast-in-place casting of the central drainage ditch foundation; installation of the central drainage ditch water pipe; backfilling of the central drainage ditch with graded crushed stone and top surface protection. Installation of inverted arch steel frame; slag removal at upper and lower steps of the working face; erection of mesh panels for upper and lower steps of the working face; locking of upper and lower steps of the working face, system anchor bolts, and advanced construction; Step 7: Shotcrete the upper and lower steps of the working face, and then shotcrete the initial support of the invert arch; Step 8: Cycle the excavation and support of the invert arch and the construction of the central drainage ditch, with the excavation areas of the invert arch and the central drainage ditch being constructed longitudinally in a staggered manner; Step Nine: Invert arch drainage construction, invert arch reinforcement construction, invert arch formwork installation, invert arch concrete construction, invert arch concrete reinforcement, and invert arch filling construction. Step 10: Construction of the invert arch and central drainage ditch in the next cycle; filling and curing of the upper invert arch. The operation adopts a parallel operation method of central water ditch under double trestle bridge and invert arch lining, and adds an independent operation area for central water ditch between the working face and invert arch lining.

2. The method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to claim 1, characterized in that: The time for the process of "drilling and loading explosives on the upper and lower steps of the working face" is X, the time for the process of "removing slag from the central ditch" is Y, and the time for the processes of "drilling and loading explosives 42m ahead of the lower step of the working face" and "drilling and loading explosives 8m ahead of the vertical pre-splitting section and 5m ahead of the longitudinal lifting section of the central ditch" are both Z, satisfying X≥Y+Z.

3. The construction method for a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to claim 1, characterized in that: When there is a conflict between the logistics of the central drainage ditch operation section and the working face operation section and the invert arch operation section, priority should be given to ensuring the backfilling of the central drainage ditch.

4. The method for constructing a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to claim 1, characterized in that: For the central ditch section formed by blasting, if there is over-excavation, it is treated by backfilling with C25 shotcrete and manual trimming.

5. The construction method for a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to claim 1, characterized in that: For the construction of central drainage ditches in poor locations, mobile supports that match the external excavation dimensions of the central drainage ditches are made using I-beams, steel pipes, and steel plates. After the central drainage ditches are excavated, they are hoisted into the trench by an excavator, and then the central drainage ditches are constructed inside the mobile supports. Once the construction of the central drainage ditch in this cycle is completed, the excavator will be used to longitudinally move the support frame for the next cycle of construction.

6. The construction method for a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to claim 1, characterized in that: When the geological conditions ahead are extremely poor and monitoring indicates that the deformation of the surrounding rock support is large, the central ditch area of ​​this section should be pre-reinforced 7 days in advance. A down-the-hole drill was used to excavate along the outer contour line on both sides of the central ditch and longitudinally install φ76 steel pipes at 1m intervals in a quincunx pattern, and then inject 1:1 cement slurry.

7. The construction method for a central drainage ditch in the surrounding rock section of a single-track railway tunnel according to claim 1, characterized in that: To address the issue of increased sidewall deformation after the excavation of the central drainage ditch, the timing of the central drainage ditch excavation should be strictly controlled. Specifically, the central drainage ditch can be excavated when the strength of the initial shotcrete support of the arch wall and the strength of the anchor grout reach more than 80%.

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