Rapid construction method for TBM double-track tunnel trackless transportation cross-line bypassing cushion layer

Abstract

The invention discloses a TBM double-track tunnel trackless transportation cross-line bypassing cushion layer rapid construction method, and belongs to the technical field of tunnel construction. According to the method, a construction area is divided into a plurality of construction sections in the longitudinal direction of a tunnel, construction and transport vehicle framing and side alternate operation is organized, and parallel cushion layer pouring and trackless transport are achieved; the method comprises the following steps of: performing radar detection and scabbling treatment on the top surface of an inverted arch block during construction preparation; installing a steel plate water stop belt, and penetrating through the ground beam and the drainage blind pipe; a detachable steel pipe is adopted for shaping and constructing a cushion drainage ditch; after a reinforcing mesh is laid, concrete pouring, multi-pass surface finishing, steam and heat preservation curing and temperature and humidity monitoring are conducted; by optimizing the construction organization and technology, the problems that transportation is interrupted, the construction period is long and cracking is prone to occurring in a traditional method are solved, efficient, high-quality and low-interference cushion layer construction is achieved, optimal construction parameters can be scientifically screened by setting a contrast test section, and adaptability is high.

Description

Technical Field

[0001] This invention relates to the field of tunnel construction technology, and in particular to a rapid construction method for a trackless transport bypass subbase layer in a TBM double-track tunnel. Background Technology

[0002] In the construction of dual-track tunnels using a TBM (Tunnel Boring Machine), a concrete cushion layer is typically constructed on the top surface of the tunnel invert block to ensure the safe and efficient passage of subsequent trackless transport vehicles (such as dump trucks, concrete mixer trucks, and commuter vehicles). This cushion layer not only serves as the road surface but also integrates auxiliary functions such as drainage ditches and pre-embedded rail pipes, making it a key structure for ensuring smooth logistics during the overall tunnel construction.

[0003] However, traditional subbase construction methods generally have the following prominent drawbacks, making them difficult to adapt to the efficient and continuous tunneling rhythm of TBM tunnels:

[0004] Low construction efficiency severely disrupts TBM tunneling: Traditional methods often employ on-site formwork and segmented full-section cast-in-place concrete pouring. This process is cumbersome, and the long concrete curing period necessitates prolonged and complete interruptions to the trackless transport line. This fundamentally contradicts the rapid transport requirements for materials, personnel, and equipment needed for continuous TBM tunneling, easily causing TBMs to stop due to material shortages and severely impacting the overall construction progress.

[0005] Insufficient structural safety and durability: Existing methods lack precise control over the bonding quality between the subbase and the underlying arch block, as well as its own load-bearing capacity. Problems such as improper surface treatment, inadequate control of the reinforcing steel protective layer, and insufficient release of temperature and shrinkage stress can easily lead to road surface settlement, damage, and through cracks in the subbase under repeated heavy vehicle traffic, creating safety hazards and increasing subsequent maintenance costs.

[0006] The construction organization is complex and the safety risks are high: cross-line construction and transportation operations overlap in space and time. Traditional solutions require frequent traffic diversions and switching between construction and traffic areas. This not only greatly increases the difficulty of on-site coordination and management, but also leads to chaotic personnel and equipment flow routes, significantly increases the risk of collisions, and makes it difficult to guarantee the supply of materials.

[0007] Poor adaptability and poor economic efficiency: Traditional "one-size-fits-all" construction parameters are difficult to adapt to differences in tunnel cross-sections, geological conditions, and vehicle loads. At the same time, the extensive use of disposable formwork, waste of curing water resources, and losses due to TBM downtime caused by construction interruptions all contribute to the high overall construction costs.

[0008] Therefore, developing a TBM dual-track tunnel trackless transportation bypass subbase construction method that enables rapid construction, parallel transportation, safety, reliability, and cost-effectiveness has become a key issue that urgently needs to be addressed in the field of tunnel construction technology. Summary of the Invention

[0009] The purpose of this invention is to provide a rapid construction method for the bypass subbase layer of a TBM dual-track tunnel trackless transportation system in order to solve the above-mentioned problems.

[0010] The present invention achieves the above objectives through the following technical solutions:

[0011] A rapid construction method for a bypass subbase layer in a TBM dual-track tunnel for trackless transportation includes the following steps:

[0012] The construction area was divided into multiple construction sections along the longitudinal direction of the tunnel; for each construction section, construction equipment and transport vehicles were organized to work alternately on different sides and sections to achieve parallel construction of the subbase layer and trackless transportation.

[0013] The construction preparation, installation of waterstops and embedded parts, construction of drainage ditches for the foundation layer, construction of steel mesh, and concrete pouring and curing are carried out in sequence.

[0014] Preferably, the cushion layer is a permanent structural layer set on the top surface of the tunnel invert block, and its cross-section is arranged symmetrically on both sides, with a central drainage ditch between the two cushion layers.

[0015] Preferably, the construction preparation includes:

[0016] The top surface of the inverted arch block was cleaned and rinsed, and radar scanning was used to detect the compaction of the backfill at its bottom.

[0017] The top surface of the inverted arch block and the low side wall shall be roughened, with a roughening rate of not less than 95%, and the roughening height of the low side wall shall be equal to the design height of the subbase.

[0018] Preferably, the installation of the waterstop and embedded parts includes the installation of steel plate waterstop, the installation of through ground beam, and the installation of blind pipe;

[0019] The installation of the steel plate waterstop includes:

[0020] Make a slit at the designed location on the side of the low wall, with a slit width of 5mm and a depth of 15cm;

[0021] After the steel plate waterstop is hammered to extend it into a straight shape on one side, it is inserted into the cut to ensure straight installation.

[0022] The installation of the through-beam includes:

[0023] Mark the installation location of the through-beam with a chalk line;

[0024] A percussion drill was used to drill holes in the top surface of the inverted arch block, and the ground beam reinforcement was inserted. The ground beam reinforcement was then installed by binding and connecting it to the ground beam.

[0025] The blind tube installation includes:

[0026] Clean and unclog the holes in the pre-reserved blind pipes in the triangular area;

[0027] Use a 90° connector to connect the blind pipe and fix it above the ground beam on the side of the low side wall. The blind pipe extends to the side of the drainage ditch of the subgrade.

[0028] The construction of the drainage ditch in the subgrade adopts a steel pipe standard, including:

[0029] Before concrete construction, the steel pipe is fixed at the drainage ditch, with half of the steel pipe embedded in the concrete and the other half exposed.

[0030] After the concrete has set, the steel pipe is removed to form a semi-circular drainage ditch.

[0031] Clean the drainage ditches, blind drainage pipes, and blind drainage pipes of the subgrade and side ditches, and protect them with geotextile.

[0032] Preferably, the construction of the reinforcing mesh includes:

[0033] Positioning ribs are arranged in a rectangular array on the top of the inverted arch block;

[0034] The reinforcing mesh is fixed to the positioning bar by tying and overlapping.

[0035] Preferably, the concrete pouring and curing includes:

[0036] Concrete pump trucks are used for unidirectional pouring.

[0037] Manually compacting with a hand-held vibrator;

[0038] The surface treatment is completed before the concrete sets by using a horizontal scraper for initial leveling, a road polisher for secondary finishing, and a manual trowel for tertiary finishing.

[0039] After the concrete has initially set, a steam curing frame is erected using tarpaulin and seamless steel pipes, and an atomizing generator is used for steam curing.

[0040] Steam curing continues until the next batch of concrete is poured;

[0041] After the curing is completed, cover the area with geotextile and sprinkle water to keep it moist. The total curing time should not be less than 14 days.

[0042] Preferably, the method further includes embedding a temperature sensor in the core of the subbase before concrete pouring to continuously monitor the hydration heat temperature of the concrete for a period of not less than 14 days, and optimizing the curing process based on the temperature data.

[0043] Preferably, it also includes traffic testing and crack monitoring steps: after the subbase reaches the design strength, small load and heavy load traffic tests are carried out in stages, and crack observation instruments are used to monitor and record the morphology, width, depth and development of cracks on the subbase surface throughout the process.

[0044] On the other hand, the present invention also relates to a method for selecting the optimal construction scheme for the subbase based on the above-mentioned rapid construction method for trackless transportation bypass subbase in TBM dual-track tunnels, including:

[0045] Multiple parallel test sections with different construction parameters are set up along the longitudinal direction of the tunnel. The construction parameters include at least one of the following: concrete strength grade, steel mesh configuration, spanned pouring length, and whether or not to set embedded parts.

[0046] A unified traffic load test and crack monitoring were conducted on the completed subbase layers of each test section.

[0047] Based on the timing, number, development of cracks, and overall condition of the subbase, the effects of different construction parameters on the crack resistance and bearing capacity of the subbase were compared and analyzed, and the optimal combination of construction parameters was selected as the standard scheme for subsequent construction.

[0048] Preferably, the comparative analysis and screening steps include:

[0049] When test data show that the crack resistance and bearing capacity of the plain concrete cushion layer meet the requirements under the short-span pouring and refined curing process, the parameter combination without steel mesh is selected as the optimal solution.

[0050] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0051] 1. Through the innovative “segmented pouring and segmented detour” construction organization, the parallel operation of the subbase layer and trackless transportation in time and space was realized; the transport vehicles do not need to wait for the entire section to be completed before they can pass through the unconstructed or already maintained sections, which fundamentally solves the conflict between construction and transportation, so that the TBM tunneling logistics is not disturbed and the construction progress of the critical path is guaranteed.

[0052] 2. Through radar detection, high-standard roughening (≥95%), and precise control of the steel reinforcement protective layer, a strong bond between the foundation concrete and the invert arch block is ensured, preventing interlayer delamination; standardized construction of the continuous ground beam and steel mesh enhances the integrity and bending resistance of the foundation, effectively resisting heavy vehicle loads; a scientifically designed system of real and dummy joints, and the use of polyurethane sealant for filling, effectively guides and releases the shrinkage stress and temperature stress of the concrete, significantly reducing the risk of disordered cracking;

[0053] 3. From base surface treatment and material installation to concrete pouring and curing, quantitative process parameters and inspection standards are set; in particular, automatic monitoring of concrete core temperature and environment is introduced, realizing active control of the hydration heat effect of large-volume concrete, transforming "experience-based construction" into "data-driven construction", and ensuring the controllability and traceability of the project's physical quality.

[0054] 4. Significantly reduced safety risks and smooth construction organization: Clear zoning and traffic organization plans reduce equipment cross-operation and mixed traffic of people and vehicles, thus reducing the risk of safety accidents; modular construction technology (such as steel pipe fixed drainage ditches) reduces high-altitude and edge-prone operations, improving operational safety;

[0055] 5. Rapid construction technology and parallel operation mode directly shorten the critical path construction period and reduce labor input and equipment shifts; reusable prefabricated molds (such as drainage ditch steel pipes) replace a large number of disposable wooden formwork, reducing material consumption and waste; high-pressure water washing for dust suppression, utilization of the high humidity environment inside the tunnel, and precise maintenance measures meet the requirements of green construction and reduce water and energy consumption.

[0056] 6. This invention, through setting up parallel test sections with multiple parameters and conducting systematic verification, can scientifically and quickly screen out the optimal construction scheme (such as concrete grade, reinforcement method, and span length) that is most suitable for specific engineering geology, load, and cross-sectional conditions. This empirical decision-making mechanism enables the method to be flexibly adapted to various TBM dual-track tunnel projects and has broad application value. Attached Figure Description

[0057] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0058] Figure 1 This is a flowchart illustrating a rapid construction method for a TBM dual-track tunnel trackless transportation bypass subbase layer as described in Embodiment 1 of the present invention.

[0059] Figure 2 This is a schematic diagram of the subbase pouring location as described in Embodiment 1 of the present invention.

[0060] Figure 3 This is a schematic diagram of the installation position of the through-beam as described in Embodiment 1 of the present invention.

[0061] Figure 4 This is a schematic diagram of the installation positions of the positioning bars and steel mesh as described in Embodiment 1 of the present invention.

[0062] Figure 5 This is a schematic diagram of the installation position of the temperature and humidity sensor inside the padding layer as described in Embodiment 1 of the present invention.

[0063] Figure 6 This is a construction schematic diagram of test section one as described in Embodiment 2 of the present invention.

[0064] Figure 7 This is a construction schematic diagram of test section two as described in Embodiment 2 of the present invention.

[0065] Figure 8 This is a construction diagram of the location of the electric track pipe passing through the cushion layer in the test section 2 of the present invention, as described in Embodiment 2 of the present invention.

[0066] Figure 9 This is a construction schematic diagram of test section three as described in Embodiment 2 of the present invention.

[0067] Figure 10 This is a construction schematic diagram of test section four as described in Embodiment 2 of the present invention.

[0068] Figure 11 This is a construction schematic diagram of test section five as described in Embodiment 2 of the present invention.

[0069] Explanation of reference numerals in the attached figures:

[0070] 1. Inverted arch block; 2. Triangular area; 3. Low side wall; 4. Subbase; 5. Central drainage ditch; 6. Subbase drainage ditch; 7. Subbase drainage blind pipe; 8. Side ditch drainage blind pipe; 9. Blind pipe reserved in inverted arch block; 10. Blind pipe reserved in triangular area; 11. Ground beam reinforcement; 12. Through ground beam; 13. Positioning reinforcement; 14. Reinforcing mesh; 15. Temperature sensor; 16. Power rail conduit. Detailed Implementation

[0071] The present invention will be further described below with reference to the accompanying drawings:

[0072] Example 1

[0073] This embodiment provides a rapid construction method for a bypass subbase layer in a TBM dual-track tunnel for trackless transportation, such as... Figure 1 The construction organization process shown includes the following steps:

[0074] Step S1: Construction Preparation

[0075] The pouring location of the foundation layer 4 is as follows Figure 2 As shown, firstly, the top surface of the installed tunnel invert block 1 is thoroughly treated; high-pressure water hoses are used to flush away concrete laitance, loose slag and other debris; then, ground-penetrating radar is used to scan and detect the compaction of the backfill inside and at the bottom of the invert block 1 to ensure the stability of the base layer; the detection points are reasonably arranged along the longitudinal and transverse directions of the tunnel.

[0076] Next, the top surface of the inverted arch block 1 and the low side wall 3 are roughened. First, a road surface roughening machine is used to roughen the large area as a whole, and then a handheld pneumatic roughening machine is used to roughen the local area in detail to ensure that the overall roughening rate is not less than 95% in order to enhance the bonding force between the new and old concrete. The roughening height of the low side wall 3 is consistent with the design height of the subsequent subbase 4, for example, 34.5 cm.

[0077] Step S2: Installation of waterstop and embedded parts

[0078] At the predetermined location on the low side wall 3 (e.g., 15 cm from the side), use a road cutter to cut a 5 mm wide and 15 cm deep slit; tap the L-shaped steel plate waterstop on one side to extend it into a straight strip, and then insert it into the cut slit to ensure straight installation;

[0079] like Figure 3 As shown, the installation position of the through beam 12 is marked with a chalk line; a hole is drilled on the top surface of the inverted arch block 1 using an impact drill, with a drilling depth of 30 cm, and the spacing of the reinforcing bars 11 in the same group of ground beams can be 20 cm.

[0080] Clean the holes for the pre-reserved blind pipes 10 in the triangular area 2 of the tunnel, use a high-pressure water gun to unclog any potentially blocked pipes, and install the subgrade drainage blind pipes 7 and side ditch drainage blind pipes 8; fix the subgrade drainage blind pipes 7 and side ditch drainage blind pipes 8 to the through beam 12, ensuring they are secure and straight; Figure 2 As shown, the lower ends of the subgrade drainage blind pipe 7 and the side ditch drainage blind pipe 8 are connected to the central drainage ditch 5 through the triangular area reserved blind pipe 10 and the invert block reserved blind pipe 9, respectively.

[0081] Step S3: Construction of drainage ditch and steel mesh 14

[0082] The subgrade drainage ditch 6 uses a steel pipe with an outer diameter of 200 mm as a shaping mold. Before pouring concrete, the steel pipe is accurately fixed at the upper end of the subgrade drainage blind pipe 7, so that it is buried 100 mm into the concrete and exposed 100 mm. After the concrete has set, the steel pipe is pulled out to form a smooth ditch. During construction, the subgrade drainage blind pipe 7 in the subgrade drainage ditch 6 and the side ditch drainage blind pipe 8 on the upper surface of the subgrade 4 need to be cleaned, and the pipe openings are covered with geotextile to prevent debris from clogging.

[0083] like Figure 4 As shown, during the construction of the steel mesh 14, positioning bars 13 are set on the top surface of the invert block 1 at a spacing of about 1 meter × 1 meter; the positioning bars 13 and the steel mesh 14 are tied and lapped together, and the thickness of the protective layer of the steel bar ends and the steel mesh 14 is strictly controlled to ensure the durability of the structure.

[0084] Step S4: Concrete pouring and curing

[0085] Concrete is poured continuously in one direction using a pump truck. During the pouring process, a handheld vibrator is used to fully vibrate the concrete to ensure compaction. Surface treatment is completed in three steps before initial setting: first, a horizontal scraper is used for initial leveling; then, a road polisher is used for secondary finishing to eliminate scratches and improve flatness; finally, a trowel is used manually for three rounds of fine finishing to improve surface smoothness.

[0086] About 4 hours after the concrete is poured (after initial setting), a curing shed consisting of tarpaulin and seamless steel pipes is immediately erected and equipped with an atomizing generator for steam curing. Steam curing continues until the next section of concrete is poured. Afterward, geotextile is used to cover the four surfaces of the subbase and water is sprayed regularly to keep it moist. The total curing time is no less than 14 days.

[0087] Step S5: Expansion Joint Treatment and Quality Monitoring

[0088] True joints and false joints are set along the longitudinal direction of the tunnel at the designed intervals; the width of the true joint is 2 cm, extending downwards to the invert block 1, and is pre-formed using a shaped steel template; the width of the false joint is 8 mm and the depth is 8 cm, and it is cut out using a cutting machine after the concrete has reached a certain strength; after all gaps are cleaned, they are filled tightly with polyurethane sealant.

[0089] like Figure 5 As shown, to control the heat of hydration of concrete, temperature sensors 15 (e.g., 2 per side per section) were pre-embedded in the core of the foundation layer 4 before pouring. The core temperature and ambient temperature and humidity were continuously monitored for 14 days after pouring. Data showed that under steam and moisturizing curing, the core temperature of concrete of different grades usually reached its peak within 32-44 hours after pouring (e.g., 56.6℃-72.1℃), then steadily decreased, and stabilized after 14 days (e.g., 20.8℃-24.9℃), approaching the ambient temperature. The average humidity inside the cavity was maintained above 93%, effectively suppressing the generation of temperature cracks.

[0090] Example 2

[0091] This embodiment provides a method for selecting the optimal construction scheme for the subbase layer based on the basic construction method of the trackless transportation bypass subbase layer in TBM double-track tunnels according to Embodiment 1. It aims to illustrate how to screen out the optimal subbase layer construction parameters suitable for specific engineering conditions through systematic testing. The specific implementation steps are as follows:

[0092] Five parallel test sections were set up in a continuous section within the tunnel. The construction requirements for the subbase 4 in each test section were as follows: 34.5 cm thick concrete subbase 4, 255 cm wide on one side, 580 cm wide on both sides including the central drainage ditch, 0.88 m³ concrete volume per linear meter on one side, and 1.76 m³ concrete volume per linear meter on both sides. Different combinations of construction parameters were used for each test section. The construction parameters for each test section are set as follows:

[0093] Test Section 1: Mileage from DK949+700 to 625, using C20 concrete with double-layer steel mesh 14; 8mm HPB300 steel mesh 14 is added 5cm below the top surface and 5cm above the bottom surface of the subbase 4; in the DK949+700-662.5 section (37.5m), slabs are poured every 6.25m, and in the DK949+662.5-625 section (37.5m), slabs are poured every 12.5m; a true joint with a width of 2cm is formed between adjacent slabs; the construction diagram of this test section is shown below. Figure 6 As shown.

[0094] Test Section 2: The section spans from DK949+625 to 550, using C20 concrete with a single layer of 14mm steel mesh. An additional 10HPB30 steel mesh (14mm) is added 5cm below the top surface of the foundation layer. In the DK949+625-587.5 section (37.5m), slabs are poured every 6.25m, and in the DK949+587.5-550 section (37.5m), slabs are poured every 12.5m. A true joint with a width of 2cm is formed between adjacent slabs. A construction diagram of this test section is shown below. Figure 7 As shown; this section contains an RRU chamber, such as Figure 8 As shown, six 125mm power rail conduits 16 are required to pass through the pad 4. At this location, a layer of 10HPB30 steel mesh 14 is added 5cm from the bottom of the pad 4.

[0095] Test Section 3: Mileage from DK949+550 to 475, using C30 concrete; the section from DK949+550 to 512.5 (37.5m) is divided into sections every 6.25m, and the section from DK949+512.5 to 475 (37.5m) is divided into sections every 12.5m; except for the section between two slabs at DK949+512.5, which is a real joint with a width of 2cm, all other sections have dummy joints with a width of 8mm and a depth of 8cm; the construction diagram of this test section is shown below. Figure 9 As shown.

[0096] Test Section 4: Mileage from DK949+475 to 400, using C20 concrete; the section from DK949+475 to 437.5 (37.5m) is divided into sections of 6.25m each, and the section from DK949+437.5 to 400 (37.5m) is divided into sections of 12.5m each; except for the genuine joint at DK949+437.5 between two slabs (2cm wide), all other sections have dummy joints (8mm wide, 8cm deep); the construction diagram for this test section is shown below. Figure 10 As shown.

[0097] Test Section 5: Mileage from DK949+400-325, using C30 concrete with a single layer of 14mm steel mesh; an additional 10HPB30 steel mesh (14mm) is added 5cm below the top surface of the foundation layer; in the DK949+400-362.5 section (37.5m), slabs are poured every 6.25m, and in the DK949+362.5-325 section (37.5m), slabs are poured every 12.5m; a true joint with a width of 2cm is formed between adjacent slabs; the construction diagram of this test section is shown below. Figure 11 As shown.

[0098] All test sections were constructed strictly according to the general method in Example 1. After the subbase layer of each section reached the design strength (e.g., 28 days after curing), a uniform rutting load test was conducted. The test was divided into two phases: the first phase lasted 20 days and included a small-load traffic test, including small transport vehicles such as flatbed trucks and commuter vehicles, to observe concrete cracking, mainly including alligator cracks, through cracks, and drying shrinkage cracks; the second phase lasted 22 days and included a heavy-load traffic test, including large transport vehicles such as loaders, dump trucks, excavators, and installation machines, to observe concrete surface cracking.

[0099] Cracks appeared during the curing period of the subbase and in the two test phases. The development of the cracks was observed using a crack observation instrument with glass slides. The specific results are as follows:

[0100] ① During the curing period of the subbase:

[0101] The first crack: DK949+620, is the second test section. This section consists of 14 segments of C20 concrete with a single layer of 10mm steel mesh, with a segmented pouring length of 6.25m. The crack is 0.2m wide, transverse, with a vertical angle of 10°, a length of 135cm (right side of the working face), and a depth of 34.5cm. (This crack is located at the left side of the RRU tunnel where the rail pipe passes).

[0102] The second crack: DK949+484, is the third test section, which is a C30 plain concrete section with a segmented pouring length of 37.5m; the crack width is 0.1mm, it is a transverse crack with a vertical angle of 0°, a length of 110cm (left side of the working face), and a depth of 8cm, and does not extend to the drainage ditch 6 of the subbase.

[0103] The third crack: DK949+480, is the third test section. This section is a C30 plain concrete section with a segmented pouring length of 37.5m. The crack width is 0.05mm, it is a transverse crack with a vertical angle of 0°, a length of 180cm (left side of the working face), a depth of 7cm, and extends to the drainage ditch 6 of the subbase.

[0104] ② First stage

[0105] The first crack: DK949+620, is the second test section. This section consists of 14 segments of C20 concrete with a single layer of 10mm steel mesh, with a segmented pouring length of 6.25m. The crack is 0.3mm wide, transverse, with a vertical angle of 10°, a length of 135cm (right side of the tunnel face), and a depth of 34.5cm. (This crack is located at the left side of the RRU tunnel where the rail pipe passes).

[0106] The second crack: DK949+484, is the third test section, which is a C30 plain concrete section with a segmented pouring length of 37.5m; the crack width is 0.2mm, it is a transverse crack with a vertical angle of 0°, a length of 110cm (left side of the working face), and a depth of 8cm, and does not extend to the drainage ditch 6 of the subbase.

[0107] The third crack: DK949+480, is the third test section. This section is a C30 plain concrete section with a segmented pouring length of 37.5m. The crack width is 0.25mm, it is a transverse crack with a vertical angle of 0°, a length of 180cm (left side of the working face), a depth of 7cm, and extends to the drainage ditch 6 of the subbase.

[0108] ③ Second stage

[0109] The first crack: DK949+620, is the second test section. This section consists of 14 segments of C20 concrete with a single layer of 10mm steel mesh, with a segmented pouring length of 6.25m. The crack is 0.4mm wide, transverse, with a vertical angle of 10°, a length of 135cm (right side of the working face), and a depth of 34.5cm. (This crack is located at the left side of the RRU tunnel where the rail pipe passes).

[0110] The second crack: DK949+484, is the third test section. This section is a C30 plain concrete section with a segmented pouring length of 37.5m. The crack width is 0.3mm, it is a transverse crack with a vertical angle of 0°, a length of 110cm (left side of the working face), and a depth of 8cm. It does not extend to the drainage ditch 6 of the subbase.

[0111] The third crack: DK949+480, is the third test section. This section is a C30 plain concrete section with a segmented pouring length of 37.5m. The crack width is 0.4mm, it is a transverse crack with a vertical angle of 0°, a length of 180cm (left side of the working face), a depth of 7cm, and extends to the drainage ditch 6 of the subbase.

[0112] By comparing and analyzing the monitoring data, the influence of each parameter on the performance of the subbase can be determined. For example, the analysis found that:

[0113] Under the same concrete grade, sections with reinforced concrete mesh 14 (especially double-layer mesh) exhibit significantly better crack resistance and load-bearing capacity than plain concrete sections.

[0114] Under the same support parameters, sections poured with shorter spans (e.g., 6.25 meters) have a significantly lower probability and severity of cracking than sections poured with longer spans or as a single unit.

[0115] Around embedded parts such as rail pipes, stress concentration makes them more prone to cracking.

[0116] Based on the above principles, the optimal and most economical parameter combination can be scientifically selected as the standard scheme for subsequent large-scale construction. This embodiment selects test section four: the DK949+475-400 section (75m) is poured with slabs every 6.25m, using C20 plain concrete. This scheme is the final scheme.

[0117] This solution achieves a good balance between economy, efficiency and quality under the specific conditions, while ensuring that the subbase 4 meets the requirements for heavy-duty transportation.

[0118] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are only illustrative of the principles of the present invention. Various changes and modifications can be made to the present invention without departing from the spirit and scope of the present invention, and all such changes and modifications fall within the scope of the present invention as claimed.

Claims

1. A rapid construction method for a bypass subbase layer for trackless transportation in a TBM dual-track tunnel, characterized in that, Includes the following steps: The construction area is divided into multiple construction sections along the longitudinal direction of the tunnel; for each construction section, construction equipment and transport vehicles are organized to work alternately on different sides and in different sections to achieve parallel construction of the subbase (4) and trackless transportation. Construction preparation, installation of waterstop and embedded parts, construction of drainage ditch (6) of subbase, construction of steel mesh (14) and concrete pouring and curing are carried out in sequence.

2. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, The cushion layer (4) is a permanent structural layer set on the top surface of the tunnel invert block (1). Its cross-section is arranged symmetrically on both sides, and a central drainage ditch (5) is provided between the two cushion layers (4).

3. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, The construction preparation includes: The top surface of the inverted arch block (1) was cleaned and rinsed, and radar scanning was used to detect the compaction of the backfill at its bottom. The top surface of the inverted arch block (1) and the short side wall (3) are roughened, and the roughening rate is not less than 95%. The roughening height of the short side wall (3) is equal to the design height of the cushion layer (4).

4. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, The installation of the waterstop and embedded parts includes the installation of the steel plate waterstop, the installation of the through ground beam 12, and the installation of the blind pipe. The installation of the steel plate waterstop includes: Make a cut at the designed location on the side of the low wall (3), with a cut width of 5mm and a depth of 15cm; After hammering the steel plate waterstop to extend it into a straight shape on one side, insert it into the cut to ensure straight installation; The installation of the through-beam 12 includes: Mark the installation position of the through beam 12 with a chalk line; A hole was drilled on the top surface of the inverted arch block (1) using an impact drill, and the ground beam reinforcement (11) was inserted. The ground beam (12) was then installed by binding the ground beam reinforcement (11). The blind tube installation includes: Clean and unclog the triangular area (2) the reserved holes for blind pipes 10 in the triangular area; Connect the blind pipe with a 90° connector and fix it above the ground beam (12) on the side of the low side wall (3). The blind pipe extends to the side of the drainage ditch (6) of the subgrade. The construction of the drainage ditch (6) in the subgrade adopts a steel pipe standard, including: Before concrete construction, the steel pipe is fixed at the drainage ditch, with half of the steel pipe embedded in the concrete and the other half exposed. After the concrete has set, the steel pipe is removed to form a semi-circular drainage ditch. Clean the drainage ditch (6), drainage blind pipe (7), and side ditch drainage blind pipe (8) of the subgrade and protect them with geotextile.

5. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, The construction of the steel mesh (14) includes: Positioning ribs (13) are arranged in a rectangular array on the top of the inverted arch block (1); The steel mesh (14) is fixed on the positioning bar (13) by tying and overlapping.

6. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, The concrete pouring and curing process includes: Concrete pump trucks are used for unidirectional pouring. Manually compacting with a hand-held vibrator; The surface treatment is completed before the concrete sets by using a horizontal scraper for initial leveling, a road polisher for secondary finishing, and a manual trowel for tertiary finishing. After the concrete has initially set, a steam curing frame is erected using tarpaulin and seamless steel pipes, and an atomizing generator is used for steam curing. Steam curing continues until the next batch of concrete is poured; After the curing is completed, cover the area with geotextile and sprinkle water to keep it moist. The total curing time should not be less than 14 days.

7. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, It also includes embedding a temperature sensor (15) in the core of the subbase (4) before concrete pouring to continuously monitor the hydration heat temperature of the concrete for a period of no less than 14 days, and optimizing the curing process based on the temperature data.

8. The rapid construction method for a bypass subbase layer in a TBM dual-track tunnel according to claim 1, characterized in that, It also includes the steps of traffic test and crack monitoring: after the subbase (4) reaches the design strength, small load and heavy load traffic tests are carried out in stages, and crack observation instruments are used to monitor and record the morphology, width, depth and development of cracks on the surface of the subbase (4) throughout the process.

9. A method for selecting the optimal construction scheme for a subbase layer based on the rapid construction method for trackless transportation bypass subbase layer in a TBM double-track tunnel as described in any one of claims 1-8, characterized in that, include: Multiple parallel test sections with different construction parameters are set up along the longitudinal direction of the tunnel. The construction parameters include at least one of the following: concrete strength grade, steel mesh (14) configuration, span pouring length, and whether or not to set embedded parts. A unified traffic load test and crack monitoring were conducted on the subbase (4) completed in each test section; Based on the timing, number, development of cracks and the overall condition of the subbase (4), the effects of different construction parameters on the crack resistance and bearing capacity of the subbase (4) were compared and analyzed, and the combination of construction parameters with the best comprehensive performance was selected as the standard scheme for subsequent construction.

10. The method for selecting the optimal construction scheme for the subbase layer according to claim 9, characterized in that, The comparative analysis and screening steps include: When the test data shows that the crack resistance and bearing capacity of the plain concrete cushion layer (4) meet the requirements under the short-span pouring and refined curing process, the parameter combination of not configuring the steel mesh (14) is selected as the optimal solution.

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