Fabricated prefabricated inverted arch construction method for single-track curve railway tunnel

Abstract

The invention provides an assembly type prefabricated inverted arch construction method for a single-track curve railway tunnel, which comprises the following steps of: carrying out field survey, and selecting an excavation method to carry out preliminary excavation after determining a tunnel curve and geological conditions; after excavation is completed, assembling type curve prefabricated structures are designed according to the curve condition of the tunnel, and after the assembling type prefabricated structures are sequentially spliced in the tunnel, precise positioning and high-precision adjustment are conducted; after high-precision adjustment is completed, the assembly type curve prefabricated structure is fixed and grouted; the assembly type curve prefabricated structure comprises a plurality of wedge-shaped blocks and flexible connecting pieces used for achieving tight connection of the wedge-shaped blocks. The assembly type prefabricated inverted arch construction method is mainly used for achieving rapid construction of the single-track curve railway tunnel, and the construction period of the curve railway tunnel is remarkably shortened through direct assembly of the assembly type curve prefabricated structures.

Description

Technical Field

[0001] The present invention belongs to the technical field of prefabricated construction, and specifically relates to a prefabricated invert construction method for a single-track curved railway tunnel. Background Art

[0002] In the construction of single-track railway tunnels, a suitable construction method is usually selected according to factors such as geological conditions, section form, and construction period requirements. The cast-in-place invert construction plan is still the mainstream construction method, but its efficiency is low. Especially in the construction and quality inspection at the curved section, it still relies on manual labor, with low construction efficiency, cumbersome processes, low turnover rate of the curved formwork, and extremely difficult control of the curved alignment. In addition, in the cast-in-place invert construction plan, the structural quality risk is relatively high. The vibration compaction at the curved section is difficult, and problems such as honeycombing and pockmarks are likely to occur. In addition, it is difficult to handle the waterproofing at the construction joints of the segmental cast-in-place, and when the force at the curved section is complex, leakage is likely to occur at this joint, which further makes the overall tunnel structure quality at risk. Therefore, how to design a construction method with high construction efficiency, high precision of the curved alignment, and comprehensive upgrade of the structural quality is the key to realizing the construction of single-track curved tunnels.

[0003] In view of this, the present invention is specifically proposed. Summary of the Invention

[0004] The first object of the present invention is to provide a prefabricated invert construction method for a single-track curved railway tunnel. This prefabricated invert construction method is mainly used to achieve the rapid construction of single-track curved railways. Through the prefabricated curved structure, the rapid construction at the single-track curved section can be realized. After the prefabricated assembled curved structure is directly assembled, the construction period of the curved section can be significantly shortened. And when prefabricating, the radian of the prefabricated assembled curved structure can be customized according to the curvature of the curve, so as to ensure close conformity with the tunnel design alignment, reduce stress concentration, improve the precision of the curved alignment, and embed a water-stop component in the prefabricated assembled curved structure to comprehensively upgrade the structural quality.

[0005] In order to achieve the above object of the present invention, the following technical solutions are specifically adopted: A prefabricated invert construction method for a single-track curved railway tunnel, the method comprising the following steps: Conduct on-site survey, determine the tunnel curve and geological conditions, and then select an excavation method for preliminary excavation; After the excavation is completed, design a prefabricated assembled curved structure according to the tunnel curve conditions, and sequentially splice the prefabricated structures in the tunnel and then perform precise positioning and high-precision adjustment; After the high-precision adjustment is completed, fix the prefabricated assembled curved structure and grout; Wherein the prefabricated assembled curved structure includes a plurality of wedge blocks and a flexible connecting member for realizing the tight connection of the plurality of wedge blocks.

[0006] In the present invention, by providing an assembled precast invert construction method for a single-track curved railway tunnel, it has significant advantages in tunnels with narrow or restricted space, especially applicable to assembled precast invert construction methods for single-track railway tunnels, urban subway tunnels, mine roadways, etc. It can effectively overcome the limitations of traditional construction methods and improve construction efficiency, quality, and safety; by prefabricating assembled curved precast structures in the factory and transporting them to the site for assembly, cumbersome processes such as formwork erection, steel bar binding, concrete pouring, and curing can be avoided, thus reducing on-site operation time. Moreover, in this construction method, factory prefabrication and tunnel excavation can be carried out simultaneously, avoiding process waiting and the situation of restricted multi-disciplinary cross-operation caused by the narrow space of single-track railway tunnels, significantly improving construction efficiency and shortening the construction period; in addition, the traditional in-situ casting method requires the participation of a large number of workers and machinery, while the assembled construction method provided by the present invention only requires a small hoisting device to achieve overall construction, reducing manual interference and well solving the construction problem in narrow spaces. In addition, when prefabricating assembled curved precast structures in the factory, their concrete strength, waterproof performance, and other indicators are superior to in-situ casting, well avoiding problems such as honeycombing and pockmarks caused by insufficient in-situ casting vibration compaction.

[0007] Among them, the focus of the present invention is to achieve the assembled construction of curved tunnel railways with narrow or restricted space. In existing assembled construction schemes, most of them are for the rapid construction of straight tunnels. In curved tunnels, especially in single-track railways with narrow or restricted space, there are still certain technical difficulties and potential drawbacks in the assembled construction scheme. Among them, the assembled construction of curved tunnels has higher requirements for the complexity of precast components, strict requirements for curvature adaptability, and difficulties in standardizing special-shaped components. In the specific construction process, it is difficult to control the on-site assembly accuracy of precast components in curved railway tunnels. Limited by the poor vision conditions in the tunnel, each ring of precast components in the curved section needs to be independently lofted, resulting in an increased risk of errors; in addition, in the assembled construction of curved railway tunnels, due to a larger opening amount at the joints in the curved section, the compression and rebound of the waterstop are insufficient, which may lead to leakage. Therefore, higher requirements are imposed on the waterproof system in curved railway tunnels.

[0008] Preferably, as a further specific embodiment, the width of the inner side of the wedge block in the longitudinal direction is smaller than the width of the outer side of the curve.

[0009] Preferably, as a further specific embodiment, the flexible connecting member is a non-bonded steel strand.

[0010] In summary, the present invention provides an assembled precast inverted arch construction method for a single-track curved railway tunnel, which can well realize the assembled construction of a curved railway tunnel with narrow or space-limited tunnels. The present invention provides an assembled curved precast structure mainly applied to the construction of this curved railway tunnel. The assembled curved precast structure includes a plurality of wedge-shaped blocks and flexible connectors for realizing the tight connection of the plurality of wedge-shaped blocks. Among them, the wedge-shaped block is the key to realizing the assembled construction of a single-track curved railway tunnel. By adjusting the precast inverted arch blocks, the width of the inner side of the longitudinal curve is made smaller than the width of the outer side of the curve, so as to better realize the rapid construction of a curved railway tunnel; when assembling with wedge-shaped blocks at the curved section of a single-track railway tunnel, it can better adapt to the curve geometric characteristics at this curved section and increase the construction convenience and structural stability. By directly shortening the inner width during prefabrication, the on-site construction adjustment is reduced, the assembly accuracy is accelerated, and the longer wedge-shaped blocks on the outer side can provide a larger bearing area, so that when the train load at the curve biases to the outer side, the load can be well dispersed, avoiding cracking caused by stress concentration due to the shorter inner side. In addition, shortening the inner width at the narrow single-track tunnel railway curve section facilitates adjusting the height difference of the blocks, thus ensuring smooth drainage and preventing water accumulation while leaving more space for the inspection passage; at the same time, the present invention also realizes the assembly of a plurality of wedge-shaped blocks by adopting flexible connectors, which has a higher assembly efficiency compared with the single splicing of precast components in the existing assembled construction scheme. And adopting flexible connectors can better adapt to the deformation of the tunnel structure. When uneven settlement or lateral pressure occurs in the tunnel surrounding rock, the flexible connectors allow small displacements between the wedge-shaped blocks, avoiding concrete cracking or joint damage caused by stress concentration. In addition, the flexible connectors can tightly fill the joints. Even if there are small gaps in the joints due to deformation, the flexible connectors can expand adaptively, thereby blocking groundwater leakage, and further enhancing the waterproof seal. At the same time, the flexible connectors have elasticity, which can dissipate the vibration energy generated by earthquakes or train operations, reduce the resonance risk of precast components, and enhance the overall seismic capacity of the tunnel; therefore, the present invention splices a plurality of wedge-shaped blocks by adopting flexible connectors, so as to carry out assembled construction at the curved section of a single-track curved railway tunnel, improving the construction efficiency while achieving better waterproof performance.

[0011] Preferably, as a further specific implementation manner, the specific steps of the high-precision adjustment are as follows: One end of the lateral positioning adjustment device is attached to the primary support steel arch, and the other end is connected to the longitudinal positioning adjustment device, wherein the longitudinal positioning adjustment device is placed under the assembled curved precast structure.

[0012] In the present invention, the engineering quality and construction efficiency are significantly improved by adopting a high-precision adjustment method. This is because there are high-precision requirements for the placement position of precast blocks at the curved section of a single-track railway tunnel with a curve. The present invention realizes the high-precision positioning of the assembled curved precast structure by adopting a lateral positioning adjustment device and a longitudinal positioning adjustment device, avoiding subsequent adjustments caused by cumulative errors, enabling the assembly of precast components to be formed in one go, saving construction time. Among them, the primary support steel arch is installed immediately after the tunnel excavation, which can effectively support the surrounding rock, prevent it from loosening or collapsing, and thus ensure construction safety. A hand-operated jack is provided in the lateral positioning adjustment device, and the top of the hand-operated jack abuts against the inverted arch precast block, so that the lateral position adjustment of the assembled curved precast structure can be realized by hand-cranking; and a vertical hand-operated jack is provided in the longitudinal positioning adjustment device, and the top of the vertical jack also abuts against the assembled curved precast structure. Therefore, the longitudinal position adjustment of the assembled curved precast structure can be realized by adjusting the vertical jack. The assembled curved precast structure is finely adjusted at the millimeter level through high-precision adjustment, so as to accurately meet the splicing requirements of short inner precast blocks and long outer precast blocks, ensure uniform force on the curve, and at the same time, the splicing of the assembled curved precast structure by adopting high-precision adjustment can further improve the structural integrity and durability. High-precision adjustment can well control the assembly gap between precast components, avoid stress concentration or local water seepage at the joints, and thus extend the service life of the tunnel.

[0013] Preferably, as a further specific implementation manner, the fixing steps of the assembled curved precast structure are as follows: A reserved hole is provided on one side of the assembled curved precast structure; Subsequently, a lead screw is used to connect with the reserved hole to fix the assembled curved precast structure to the primary support steel arch of the tunnel and then pour concrete; After the pouring is completed, 2 exhaust pipes are reserved in the gap formed between the primary support steel arch and the assembled curved precast structure to ensure the grouting is dense.

[0014] In the present invention, by providing a reserved hole on one side of the assembled curved precast structure and connecting the assembled curved precast structure to the side wall by means of a hinged lead screw, it can better adapt to the uneven deformation of the curve, reduce structural stress. By adopting the hinged lead screw method, when the forces on the inner and outer sides of the tunnel at the curve are uneven, the hinged lead screw method allows for slight rotation or displacement between the precast component and the side wall, avoiding stress concentration caused by rigid connection and preventing concrete cracking. Moreover, the hinged lead screw method does not require on-site welding. After the precast component is hoisted, it can be temporarily fixed through the screw and the hinge joint, and then gradually and precisely adjusted, thus shortening the construction period.

[0015] Preferably, as a further specific implementation manner, the steps of grouting are as follows: Use an airbag to seal the gap between the bottom of the prefabricated curved structure and the tunnel bottom; Subsequently, inject the slurry through the grouting hole reserved at the top of the prefabricated curved structure.

[0016] Preferably, as a further specific implementation manner, the slurry is a mixed slurry of cement slurry, early strength agent, water and micro-expansion agent or a mixed slurry of cement mortar, early strength agent, water and micro-expansion agent.

[0017] Preferably, as a further specific implementation manner, the slurry is a mixture of cement slurry, early strength agent, water and micro-expansion agent.

[0018] In order to further ensure the construction quality, the present invention reserves a row of vertical exhaust holes in the gap formed between the primary support steel arch and the prefabricated curved structure, so as to ensure the grouting chamber, avoid cavity defects. During the grouting process, due to the extrusion of air by the slurry, if there is no exhaust hole, the air will be trapped between the precast member and the surrounding rock, thus forming cavities or bubbles, which will reduce the support strength. The setting of the exhaust hole allows the air to be discharged orderly, ensuring that the slurry completely fills the back void while preventing local cavities from appearing between the precast member and the surrounding rock at the bend. In addition, the setting of the exhaust hole can also improve the grouting fullness and structural integrity. When the air is discharged through the exhaust hole, the slurry can flow more smoothly to all the gaps, especially at the bend where the curvature changes, thus avoiding the unfilled area caused by air resistance. And the dense grouting layer can make the precast member and the surrounding rock fit tightly, improve the distribution of the eccentric load at the bend, and reduce the stress concentration. The slurry used for grouting is cement slurry or cement mortar. At the same time, in order to reduce the hardening shrinkage, the present invention adds a certain amount of early strength agent and micro-expansion agent to the slurry. Preferably, the slurry is prepared by mixing cement slurry, early strength agent, water and micro-expansion agent according to the mass ratio of 1:1:0.02:0.08.

[0019] Preferably, as a further specific implementation manner, the precise positioning adopts the infrared positioning method.

[0020] Preferably, as a further specific implementation manner, the excavation method is the bench cut method with core soil reserved.

[0021] In the present invention, after determining the geological conditions of the single-track railway tunnel, the bench cut method with core soil reserved can be selected for cross-section excavation. The specific excavation steps are as follows: Excavate the bench 1 and reserve the core soil; Construct the primary support of bench 1, that is, initially spray 4 cm thick concrete, erect the steel frame, and construct the locking foot anchor pipes; Drill the radial anchor bolts and then re-spray the concrete to the designed thickness; Subsequently, when the upper bench is constructed to an appropriate distance, excavate two steps of the bench, extend the steel frame, and carry out the initial support for the lower bench.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The present invention provides an assembled precast invert construction method for a single-track curved railway tunnel. This assembled precast invert construction method is mainly used to achieve the rapid construction of a single-track curved railway. Through the assembled curved precast structure, rapid construction at the single-track curve is realized. After the precast assembled curved precast structure is directly assembled, the construction period of the curve section is significantly shortened. Moreover, when precasting, the radian of the assembled curved precast structure can be customized according to the curve curvature of the tunnel, so as to ensure close conformity with the designed alignment of the tunnel, reduce stress concentration, improve the accuracy of the curve alignment, and embed the water-stop effect for the assembled curved precast structure, thus comprehensively upgrading the structural quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] By reading the following detailed description of the preferred embodiments, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present invention. Moreover, throughout the drawings, the same reference numerals are used to represent the same components.

[0024] Figure 1 It is a schematic diagram of the first excavation step of the bench method with a reserved core soil in an assembled precast invert construction method for a single-track curved railway tunnel according to the present invention; Figure 2 It is a schematic diagram of the second excavation step of the bench method with a reserved core soil in an assembled precast invert construction method for a single-track curved railway tunnel according to the present invention; Figure 3 It is a schematic diagram of the third excavation step of the bench method with a reserved core soil in an assembled precast invert construction method for a single-track curved railway tunnel according to the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The technical solutions of the present invention will be clearly and completely described below in conjunction with the specific embodiments. However, those skilled in the art will understand that the following described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments, and are only used to illustrate the present invention and should not be considered as a limitation to the scope of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0026] In order to more clearly illustrate the technical solutions in the present invention, the following will be described in the form of specific embodiments.

[0027] Embodiment 1 In this embodiment, the specific railway tunnel under construction is the Yaopo Tunnel of the Tianlong Railway, which is a typical curved single-track railway tunnel with limited tunnel space. The total length of the tunnel is 154 m, the elevation of the tunnel entrance is 1380.55 m, and the elevation of the tunnel exit is 1377.82 m. The tunnel is located on the R-1600 curve and the transition curve, and the longitudinal slope in the tunnel is a single-sided downhill of 154 m / -17.7‰.

[0028] The specific construction steps of the prefabricated and assembled inverted arch construction method for single-track curved railway tunnels of the present invention are as follows: Step 1: Conduct on-site surveys to determine the surrounding rock grade of the tunnel body, and use the bench method to reserve the core soil for cross-section excavation and laying of the base cushion; Surrounding rock grade of the tunnel body: It is determined that the surrounding rock grade of the tunnel body is all grade V surrounding rock; Construction and excavation method: The bench method is used to reserve the core soil for construction. The excavation method is mechanical excavation. After the cross-section and inverted arch excavation are completed, the base cushion is laid; the initial support of the tunnel is promptly constructed in accordance with the design standards following the excavation face to reduce the exposure time of the surrounding rock, inhibit the deformation of the surrounding rock, and prevent the surrounding rock from loosening and peeling in the short term; The excavation sequence of the bench method with reserved core soil. The cross-section excavation sequence of the tunnel cross-section is mainly divided into 3 steps, and the specific excavation sequence is as Figures 1-3 shown; The excavation steps of the bench method with reserved core soil are as follows: Step 1 is as Figure 1 shown: Construct advanced support and excavate the upper bench of section 1; Construct the initial support of the upper bench, that is, initially spray 4 cm thick concrete, erect the upper bench steel frame and temporary cross braces, and set up locking foot anchor pipes; After constructing the system anchor bolts, re-spray the concrete to the design thickness; Step 2 is as Figure 2 shown: When the upper bench is constructed to an appropriate distance, after the sprayed concrete on the upper bench reaches more than 70% of the design strength, excavate the lower bench of section 2. After the excavation of the lower bench is completed, immediately erect the lower bench steel frame and construct the initial support of the lower bench; Step 3 is as Figure 3 shown: Mechanically excavate the inverted arch, deal with the over-excavation and under-excavation of the inverted arch base, and remove the temporary cross braces. Under-excavation is strictly prohibited during the excavation of the tunnel inverted arch. The maximum over-excavation value shall not be greater than 25 cm, and the average linear over-excavation value shall not be greater than 10 cm. The over-excavated part of the prefabricated inverted arch shall be backfilled with shotcrete or crushed stones; The steps for laying the base cushion after the inverted arch excavation are as follows: S1: The thickness of the crushed stone laid on the inverted arch base is 15 cm, and well-graded 3-5 cm crushed stones or pea gravels are selected; S2: For the laying of base gravel, a mold - type feeding hopper is used. The bottom surface is arc - shaped and serves as the mold for gravel laying. There is a herringbone partition board that discharges materials from both sides. Moving 1.5 m can achieve the feeding within a range of 3 m. The inner partition board realizes sectional loading and sectional feeding. S3: During transportation, the gravel outside the tunnel is loaded into the gravel mold feeding hopper by a loader and then transported to the designated position inside the tunnel by a transport vehicle. S4: After the gravel mold feeding hopper is transported to the place, the precast block assembling machine moves the trolley to lower the hook. After hoisting the gravel spreading hopper firmly and lifting it until it is completely separated from the transport vehicle, the trolley moves longitudinally forward to the assembling place, rotates 90°, aligns, and descends. S5: Open the feed door to discharge materials. The spreader drives the hopper to move forward and vibrate. The bottom surface of the hopper is scraped into an arc surface to complete the laying of gravel within a range of 3 m. S6: Close the feed door and cooperate with the lifting device of the invert assembling machine to realize automatic hook - up and unhook. Vibrate to level the surface of the gravel to form a standard arc surface. S7: The laying of tunnel - bottom gravel or pea gravel has no heaving, and the laying thickness, curvature, compaction degree and flatness meet the design requirements. Step Three: Prefabricated Assembled Curved Prefabricated Structure S1: Prefabricate wedge - shaped blocks, and adjust the difference between the width of the inner curve and the outer curve of the wedge - shaped blocks longitudinally according to the curve conditions at the tunnel bend. S2: Waterproof the wedge - shaped blocks. The waterproof system of the prefabricated wedge - shaped blocks adopts self - waterproofing of C40 reinforced concrete + water - swelling rubber waterstop strip around the longitudinal joint + rubber waterstop belt for the circumferential joint + bottom grouting waterproofing. Step Four: Preliminary Assembly of the Prefabricated Assembled Curved Prefabricated Structure Use infrared positioning to measure the position where the wedge - shaped blocks are lowered and installed externally, and then carry out the butt - joint assembly of the wedge - shaped blocks. The process of the butt - joint assembly of the wedge - shaped blocks mainly includes four stages: transporting the wedge - shaped blocks to the designated position, hoisting inside the tunnel, rotary hoisting of the wedge - shaped blocks, and finally installing them in place. Among them, the precast invert block assembling machine moves to lower the hook. After hoisting the wedge - shaped block firmly and lifting it until it is completely separated from the transport vehicle, it moves longitudinally forward to the assembling place, then hoists the wedge - shaped block, rotates 90°, aligns, and lowers the wedge - shaped block to the measured designated position. Step Five: Accurately Position the Prefabricated Assembled Curved Prefabricated Structure after Preliminary Assembly and Judge Whether High - Precision Adjustment is Required S1: After the longitudinal pre - tightening connection is completed, use the infrared positioning method to re - position the assembled prefabricated assembled curved prefabricated structure. If there is a deviation in the position, a high - precision adjustment device can be used to adjust the precision of the prefabricated assembled curved prefabricated structure. S2: Attach one end of the lateral positioning adjustment device tightly to the lower bench steel arch in the primary support steel arch, and the other end to the precast assembled curved structure whose position needs to be adjusted. The adjustment of the lateral orientation of the wedge block can be completed by manually controlling the hand-operated lateral jack in the lateral positioning adjustment device; S3: Place the longitudinal positioning adjustment device under the precast assembled curved structure, with its bottom closely attached to the tunnel bottom and its top tightly attached to the precast assembled curved structure. The adjustment of the longitudinal orientation of the wedge block can be completed by manually controlling the hand-operated longitudinal jack in the longitudinal positioning adjustment device; S4: According to the accurate installation position of the infrared positioning wedge block, then manually adjust the longitudinal positioning adjustment device or the lateral positioning adjustment device according to this position so that the precast assembled curved structure is in the correct position; Step Six: Complete the splicing of the precast assembled curved structure S1: The longitudinal connection of the precast assembled curved structure adopts a connection method tightened by prestressed flexible connectors. The precast assembled curved structure is installed by the embedded connector method. The position of the connector is measured and positioned by a total station to ensure accurate installation. After the first wedge block is installed, it is tensioned and pre-tightened by a flexible connector to ensure close fitting between multiple wedge blocks; S2: Check whether the positions of the concave-convex tenon grooves (structures inherent in the wedge block) at the joints of the wedge blocks are accurately docked. After longitudinal squeezing, there is no water seepage at the joints, the overall waterproof performance meets the design requirements, and after the assembly axis and elevation of the precast blocks meet the design requirements, carry out splicing; S3: The longitudinal pre-tightening device is connected and locked by unbonded steel strands; S4: The longitudinal tensile force is mainly controlled by the oil gauge reading calculated according to the regression equation of the tensioning control system for the tightening force. Due to the short elongation value, a digital display wedge-shaped feeler gauge is used to measure the gap, and the gap size is less than 3 mm, meeting the assembly accuracy requirements; S5: The prestressed locking uses a tensioning jack, the backing plate uses a steel backing plate with a diameter of 170 mm, and the connector, anchor head, etc. are selected according to the supporting products of the manufacturer; S6: After the longitudinal pre-tightening is completed, carry out lateral fixation according to the above steps to achieve the splicing of the precast assembled curved structure; Step Seven: Fix the precast assembled curved structure and grout The specific steps to achieve the fixed connection between the precast assembled curved structure and the side wall primary support steel arch are as follows: S1: There is a reserved hole on one side of the precast assembled curved structure, which is hinged and fixed to the side wall steel arch by a screw rod, and concrete is poured to make the whole structure form a closed loop, increasing the integrity of the tunnel structure; S2: Before pouring concrete at the location of the horizontally connected lead screw, embed a PVC exhaust pipe with a hollow middle as an exhaust hole, and then pour concrete to seal it. The specific steps of grouting are as follows: The construction process and technical requirements for filling and grouting the base of the prefabricated curved structure are as follows: S1: Before filling and grouting the base, check whether the positions of the concave-convex tenon grooves (structures originally on the wedge blocks) are accurately docked. After longitudinal tightening, there is no water seepage at the joint, the overall waterproof performance meets the design requirements, and the assembly axis and elevation of the precast blocks meet the design requirements. S2: The prefabricated curved structure has been connected to the initial support steel frame of the side wall, and the concrete pouring at the connection between the side wall and the prefabricated curved structure has been completed. S3: Single-component slurry is used for synchronous grouting at the bottom of the prefabricated curved structure, and cement slurry or two-component slurry can be used for secondary grouting. S4: Subsequently, use an airbag to block the gap between the wedge block at the last piece of the entire tunnel and the tunnel bottom to prevent the slurry from flowing out during grouting. S5: The filling and grouting of the base of the prefabricated curved structure is carried out by secondary grouting through the holes reserved on the wedge blocks. The primary grouting is carried out after the installation of the wedge blocks is completed. It is necessary to ensure the consolidation of the crushed stones or pea gravels at the tunnel bottom, and the slurry overflows from the joints of the two side walls to ensure the denseness of the gaps between the stones laid at the tunnel bottom and the filling of the gaps between the stones and the precast blocks. The grouting time should be carried out after the arch wall has reached an age of at least 14 days. Control the grouting pressure during the grouting process. Generally, when it reaches 0.2 MPa, the grouting can be ended. S6: Grouting is carried out before the construction of the arch wall lining without affecting the construction progress of the main tunnel. During construction, grouting is carried out from the top, with the slurry coming out at the front end. The slurry flows from the downhill point to the uphill point, and the slurry continuously spreads to fill the gap between the bottom of the precast block and the cushion layer. Try to avoid excessive bubbles and slurry bleeding during the grouting process. S7: The prepared slurry should be easy to inject, the grouting operation should be continuous, and in accordance with the principle of injecting less and multiple times, control the foundation deformation to gradually tend to be stable. S8: Equip relevant instrument and equipment for automatically recording grouting parameters, observe the changes in grouting pressure and flow rate during operation, and strictly control the grouting parameters to make dynamic adjustments in a timely manner.

[0029] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for constructing an assembled prefabricated invert for a single-track curved railway tunnel, characterized in that: The method comprises the following steps: Conduct field surveys to determine tunnel curves and geological conditions and then select an excavation method for preliminary excavation; After excavation is completed, the prefabricated curved structure is designed according to the tunnel curve, and the prefabricated curved structure is sequentially spliced ​​in the tunnel for precise positioning and high-precision adjustment; After high-precision adjustment is completed, the assembled curved prefabricated structure is fixed and grouting is performed; The assembled curved prefabricated structure comprises a plurality of wedge-shaped blocks and a flexible connector for achieving tight connection of the plurality of wedge-shaped blocks.

2. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 1, characterized in that: The width of the inner side of the curve of the wedge-shaped block in the longitudinal direction is smaller than the width of the outer side of the curve.

3. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 1, characterized in that: The flexible connector is a non-bonded steel strand.

4. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 1, characterized in that: The specific steps of the high-precision adjustment are: One end of the transverse positioning and adjusting device is attached to the primary supporting steel arch frame, and the other end is connected to the longitudinal positioning and adjusting device, wherein the longitudinal positioning and adjusting device is placed under the assembled curved prefabricated structure.

5. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 4, characterized in that: The fixing steps of the assembled curved prefabricated structure are as follows: A reserved channel is provided on one side of the assembled curved prefabricated structure; Then, the prefabricated curved prefabricated structure is connected to the reserved channel by a screw rod, and then cast after being fixed to the tunnel primary support steel arch frame; After pouring is completed, two exhaust pipes are reserved in the gap formed between the primary supporting steel arch frame and the assembled curved prefabricated structure to ensure dense grouting.

6. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 4, characterized in that: The steps of grouting are: An air bag is used to seal the bottom of the prefabricated curved structure and the tunnel bottom; Then, slurry is injected through the grouting holes reserved at the top of the assembled curved prefabricated structure.

7. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 6, characterized in that: The slurry is a mixed slurry of cement slurry, early strength agent, water and micro-expansion agent, or a mixed slurry of cement mortar, early strength agent, water and micro-expansion agent.

8. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 7, characterized in that: The slurry is a mixture of cement slurry, early strength agent, water and micro-expansion agent.

9. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 1, characterized in that: The precise positioning adopts infrared positioning method.

10. The method for constructing an assembled prefabricated invert for a single-track curved railway tunnel according to claim 1, characterized in that: The excavation method is a step method to reserve core soil.

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