A filling device and construction method for a goaf under a pilot tunnel in a multi-arch tunnel

Abstract

The present invention discloses a filling device and a construction method for a goaf under a middle pilot tunnel of a multi-arch tunnel. It includes a filling device body and a multi-arch tunnel. The middle part of the multi-arch tunnel is a middle pilot tunnel. A concrete transition plate formed by splicing multiple precast slabs is provided at the bottom of the middle pilot tunnel. The goaf is located below the middle pilot tunnel, and small conduits and seamless steel pipes are provided between the goaf and the concrete transition plate. The beneficial effects of the present invention are: low construction cost, high safety, easy to operate, and can effectively solve the problems of insufficient bearing capacity of the middle partition wall foundation caused by the goaf under the multi-arch tunnel and large grouting volume and long grouting time caused by a large goaf at the tunnel bottom.

Description

Technical Field

[0001] The present invention relates to the technical field of the construction of multi-arch tunnels, in particular to a filling device and a construction method for a mined-out area under the middle pilot tunnel of a multi-arch tunnel. Background Art

[0002] With the continuous increase in the density of the highway network in China, the urban trunk lines are gradually developing towards the surrounding areas of the city. In many cities with developed mining industries, highway construction will inevitably pass through mined-out areas. Most of the mineral resources were mined earlier. Due to the limitations in engineering technology, safety awareness, etc. at that time, the support structure of the mined-out area is poor, and even there is no support structure at all. On the other hand, multi-arch tunnels generally have a large cross-sectional span, many construction processes, and complex mechanical properties. As the main load-bearing member of the multi-arch tunnel, when there is a mined-out area at the bottom of the tunnel, the bearing capacity of the foundation of the middle partition wall cannot be guaranteed, which may cause accidents such as the sinking of the middle wall, the cracking of the wall body, and the collapse of the vault, seriously endangering the safety of the construction and operation processes.

[0003] However, although the existing production methods can produce the filling device and the implementation method at the bottom of the middle partition wall, there are still many defects: 1. In the existing filling device, the bottom of the middle pilot tunnel is mainly hardened, but after the treatment, the small ducts or seamless steel pipes need to be drilled, which increases the difficulty of the small ducts and seamless steel pipes entering the soil. 2. The stress characteristics of the partition wall are not considered in the existing technology, and at the same time, the construction efficiency is low and the cost is too high. 3. In the existing mined-out area, although grouting is carried out on the bottom of the middle pilot tunnel, it is easy to cause instability at the end after grouting, and in the existing small ducts, it is easy to cause blockage of the grouting holes during the grouting process, and it is not easy to achieve uniform grouting during the grouting process.

[0004] Based on the above technical defects, the present application urgently needs a filling device and a construction method for a mined-out area under the middle pilot tunnel of a multi-arch tunnel. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the existing technology and effectively solve the problems of low construction cost, high safety, easy operation, and can effectively solve the problems of insufficient bearing capacity of the foundation of the middle partition wall caused by the mined-out area under the multi-arch tunnel and large grouting volume and long grouting time caused by a large mined-out area at the bottom of the tunnel. A filling device and a construction method for a mined-out area under the middle pilot tunnel of a multi-arch tunnel.

[0006] The purpose of the present invention is achieved through the following technical solutions: A filling device for a mined-out area under the middle pilot tunnel of a multi-arch tunnel, which includes a filling device body and a multi-arch tunnel. The middle part of the multi-arch tunnel is a middle pilot tunnel. The bottom of the middle pilot tunnel is provided with a concrete transition plate spliced by multiple precast slabs. The mined-out area is below the middle pilot tunnel, and small ducts and seamless steel pipes are provided between the mined-out area and the concrete transition plate;

[0007] One end of each precast slab is provided with a groove group, and the other end is provided with a lapping rod group. The precast slab is provided with a through-hole group, and both ends of each precast slab are provided with foldable metal sheets. The foldable metal sheets are provided with strip-shaped grooves and through-hole threads. A gear mechanism I is arranged at the connection between the small conduit and the seamless steel pipe and the concrete transition slab. A movable power mechanism I is arranged on the gear mechanism I. The movable power mechanism I is placed on the concrete transition slab and is connected by bolts. The small conduit and the seamless steel pipe both penetrate through the concrete transition slab, and a detachable limit plate I and a detachable limit plate II are arranged at the connection between the small conduit or the seamless steel pipe and the concrete transition slab. Detachable rollers are arranged between the limit plate I and the limit plate II and the concrete transition slab.

[0008] In the filling device for the gob area under the middle pilot tunnel of the multi-arch tunnel of the present invention, a bevel gear I is arranged on the limit plate I. The movable power mechanism I includes a movable box body I. A base is arranged at the bottom of the box body I. A moving groove is arranged in the middle of the base, and through-hole threads I and through-hole threads II are arranged at both ends of the base. A motor I is arranged inside the box body I. A bevel gear II is arranged on the output shaft of the motor I. The bevel gear I and the bevel gear II are meshed with each other.

[0009] In the filling device for the gob area under the middle pilot tunnel of the multi-arch tunnel of the present invention, a switch valve is arranged on the top of the box body I. The through-hole group is provided with through-holes I, II and III with different diameters. Each precast slab is provided with at least two through-holes I, II and III. The groove group is provided with at least 7 grooves, and the lapping rod group is provided with at least 7 lapping rods that cooperate with the grooves.

[0010] In the filling device for the gob area under the middle pilot tunnel of the multi-arch tunnel of the present invention, at least three locking grooves are arranged on the bottom of each precast slab. An anti-settlement cushion plate is arranged under the concrete transition slab. The anti-settlement cushion plate is provided with convex strips. The length of the anti-settlement cushion plate has three different specifications. Blind hole threads I and blind hole threads II are arranged at both ends of the convex strips. The locking grooves cooperate with the convex strips. Rotatable sleeves are arranged at the ends of the small conduit and the seamless steel pipe. The rotatable sleeves are hermetically connected to the small conduit or the seamless steel pipe, so that when the grouting pipe is connected to the small conduit and the seamless steel pipe, the rotation of the small conduit or the seamless steel pipe is ensured.

[0011] In the filling device for the goaf under the middle pilot tunnel of the multi-arch tunnel of the present invention, each of the locking grooves is provided with a first fixing block and a second fixing block. Above the first fixing block and the second fixing block, there are respectively a first locking bolt and a second locking bolt. At both ends of each locking groove, there are a first movable locking plate and a second movable locking plate. The first movable locking plate and the second movable locking plate are both provided with a third locking bolt, and the third locking bolt is engaged with the first blind hole thread and the second blind hole thread on the rib.

[0012] In the filling device for the goaf under the middle pilot tunnel of the multi-arch tunnel of the present invention, the foldable metal sheet is formed by welding multiple metal sheets, thereby forming a docking groove. A support plate is provided on the docking groove, and the support plate is arranged on the side wall of the middle pilot tunnel; there are counterbore grooves on the first through hole, the second through hole and the third through hole. There is a gap between the small conduit and the seamless steel pipe and the through hole group, and they can rotate with the rotation of the first movable power mechanism.

[0013] In the filling device for the goaf under the middle pilot tunnel of the multi-arch tunnel of the present invention, the concrete transition plate is provided with through hole threads that cooperate with both ends of the first box body for fixation, and the small conduit and the seamless steel pipe can be selected whether to rotate according to the actual construction conditions on site.

[0014] In the construction method of the filling device for the goaf under the middle pilot tunnel of the multi-arch tunnel of the present invention, it includes the following steps:

[0015] S10. After the middle pilot tunnel is excavated and supported, the specific position and scope of the goaf under the tunnel are explored and verified through drilling and geophysical prospecting;

[0016] S11. Use a drill to drill holes at both side edges 1 m away from the bottom of the middle pilot tunnel within the goaf range, with a longitudinal spacing of 2 m and a drilling depth exceeding 1 m of the loose area at the bottom of the goaf;

[0017] S12. After the drill is displaced, insert the seamless steel pipe until the bottom of the hole for curtain grouting to form a mortar wall;

[0018] S13. Use a drill to drill small conduits for grouting on the central axis of the middle pilot tunnel within the goaf range until the lower goaf is filled, with a longitudinal drilling spacing of 2 m and a drilling depth exceeding 1 m of the loose area at the bottom of the goaf;

[0019] S14. Randomly drill holes to check whether the filling is dense. If there are still voids, insert seamless steel pipes into the inspection holes for re-grouting, and select another drilling point;

[0020] S15. Within the goaf range, the middle pilot tunnel is further excavated downward, and a reinforced concrete transition plate is laid.

[0021] In step S12, the steel pipe used is a φ108 seamless steel pipe. The butt joint of the seamless steel pipe is connected by internal screw threads. The non-pressure grouting method is adopted, and the grouting is carried out in an upward manner from bottom to top. The grouting sequence is from the deep side to the shallow side, and from the deep hole to the shallow hole. The length of the first-order hole section for grouting should be 0.3m to 0.5m. The length of the second-order hole section can be increased according to the grouting volume and grouting effect, but shall not exceed 1.0m. The main grouting material is M7.5 cement single-fluid slurry, and the water-cement ratio should be selected from 0.7:1 to 1:1. The curtain grouting is carried out according to the principle of sequential and intermittent. After the cement single-fluid slurry reaches the designed grouting pressure, immediately switch to grouting the cement-sodium silicate double-fluid slurry for sealing the hole. The volume ratio of the cement slurry to the sodium silicate slurry can be taken as 1:0.1 to 1:1. Finally, two sealed mortar walls are formed. After the grouting is completed, the steel pipe is pulled out.

[0022] In step S13, φ60 small ducts are drilled with grouting holes with a diameter of 10mm in a plum blossom shape at intervals of 5cm along the pipe circumference and 20cm along the pipe length direction. The grouting method adopted is grouting until the slurry emerges from the top. After the grouting is completed, the small ducts are not taken out and are permanently placed under the pilot tunnel together with the corresponding precast slabs.

[0023] The present invention has the following advantages:

[0024] 1. The filling device body and the connected-arch tunnel of the present invention. The filling device body includes small ducts, seamless steel pipes, and concrete steel transition plates. The concrete transition plate includes precast slabs spliced by multiple pieces, and the two ends of the precast slabs are provided with foldable metal sheets, and the foldable metal sheets cooperate with the pilot tunnel, thereby improving the integrity of the side and bottom of the pilot tunnel and increasing the stability of the pilot tunnel.

[0025] 2. The precast slab of the present invention is provided with a locking groove at the bottom, and an anti-settlement cushion plate is provided below the locking groove. The anti-settlement cushion plate is provided with convex strips, and the convex strips cooperate with the locking groove. The middle part of the locking groove is provided with a fixing plate one and a fixing plate two, and the fixing plate one and the fixing plate two are provided with a movable locking plate one and a movable locking plate two, so that the anti-settlement cushion plate can be arranged between two precast slabs for connection, solving the instability at the connection and the uneven settlement caused by directly connecting traditional precast slabs. At the same time, the setting of the anti-settlement cushion plate increases the stability with the upper part of the goaf.

[0026] 3. The mutual cooperation of the bevel gear one and the bevel gear two of the present invention enables the rotation of the small duct or the seamless steel pipe according to actual needs. When the seamless steel pipe rotates, the local stability can be guaranteed.

[0027] 4. By filling the bottom cavity of the connected-arch tunnel through the method of drilling and grouting, the problem of insufficient bearing capacity of the middle partition wall foundation in the connected-arch tunnel is solved.

[0028] 5. First, drill holes and grout on both side edges of the middle pilot tunnel. After forming two sealed mortar walls, then fill the middle area. This method can prevent the slurry injected into the cavity below the middle pilot tunnel from collapsing and flowing sideways, thereby reducing the usage of filling mortar, saving costs. At the same time, since it is not necessary to fill the entire cavity, it can also reduce the construction period delay and improve the construction efficiency.

[0029] 6. By adding a transition plate under the middle partition wall, the influence caused by uneven settlement at the bottom after the middle partition wall is poured can be reduced, and the construction safety of the double-arch tunnel can be further improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a schematic diagram of the overall structure of the present invention;

[0031] Figure 2 is a schematic diagram of the structure of the concrete transition plate in the present invention;

[0032] Figure 3 is a schematic diagram of the structure of the precast slab in the present invention;

[0033] Figure 4 is a schematic diagram of the structure of the anti-settlement cushion plate in the present invention;

[0034] Figure 5 is Figure 2 a partial enlarged schematic diagram at A in

[0035] Figure 6 is Figure 3 a partial enlarged schematic diagram at B in

[0036] Figure 7 is Figure 4 a partial enlarged schematic diagram at C in

[0037] Figure 8 is Figure 1 a partial enlarged schematic diagram at D in

[0038] Figure 9 is a flow chart of the construction method in the present invention.

[0039] In the figure, there are filling device body 1, multi-arch tunnel 2, middle pilot tunnel 3, precast slab 4, concrete transition slab 5, goaf 6, small conduit 7, seamless steel pipe 8, groove group 9, lapping bar group 10, through-hole group 11, foldable-edge metal sheet 12, first gear mechanism 13, movable power mechanism 14, first limit plate 15, second limit plate 16, first bevel gear 17, first box body 18, base 19, moving groove 20, first through-hole thread 21, second through-hole thread 22, first motor 23, second bevel gear 24, switch valve 25, locking groove 26, anti-settlement cushion plate 27, rib 28, first blind-hole thread 29, second blind-hole thread 30, first fixing block 31, second fixing block 32, first locking bolt 33, second locking bolt 34, first movable locking plate 35, second movable locking plate 36, third locking bolt 37. Detailed implementation mode

[0040] The following further describes the present invention in conjunction with the attached drawings. The protection scope of the present invention is not limited to the following:

[0041] As Figures 1 - 8 shown, a filling device for the goaf under the middle pilot tunnel of a multi-arch tunnel, which includes a filling device body 1 and a multi-arch tunnel 2. The middle part of the multi-arch tunnel 2 is a middle pilot tunnel 3. A concrete transition slab 5 composed of multiple precast slabs 4 is arranged at the bottom of the middle pilot tunnel 3. The goaf 6 is below the middle pilot tunnel 3. Small conduits 7 and seamless steel pipes 8 are arranged between the goaf 6 and the concrete transition slab 5.

[0042] A groove group 9 is arranged at one end of each precast slab 4, and a lapping bar group 10 is arranged at the other end. The mutual cooperation between the lapping bar group 10 and the groove group 9 ensures the effective splicing of adjacent precast slabs. Through-hole groups 11 are arranged on the precast slabs 4. Foldable-edge metal sheets 12 are arranged at both ends of each precast slab 4. Strip-shaped grooves and through-hole threads are arranged on the foldable-edge metal sheets 12. A first gear mechanism 13 is arranged at the connection between the small conduits 7 and the seamless steel pipes 8 and the concrete transition slab 5. A movable power mechanism 14 is arranged on the first gear mechanism 13. The setting of the movable power mechanism 14 enables selection according to actual needs. The movable power mechanism 14 is placed on the concrete transition slab 5 and connected by bolts. Both the small conduits 7 and the seamless steel pipes 8 penetrate the concrete transition slab 5. A detachable first limit plate 15 and a detachable second limit plate 16 are arranged at the connection between the small conduits 7 and the seamless steel pipes 8. Removable rollers (not shown in the figure) are arranged between the first limit plate 15 and the second limit plate 16 and the concrete transition slab 5.

[0043] The first limiting plate 15 is provided with a first bevel gear 17. The first movable power mechanism 14 includes a movable first box body 18, and a base 19 is provided at the bottom of the first box body 18. A moving groove 20 is provided in the middle of the base 19. The moving groove 20 can be placed and moved according to the needs of construction. Through holes with threads one 21 and through holes with threads two 22 are provided at both ends of the base 19. The through holes with threads one 21 and through holes with threads two 22 enable the first box body 18 to be fixed by bolts. A first motor 23 is provided inside the first box body 18, and a second bevel gear 24 is provided on the output shaft of the first motor 23. The first bevel gear 17 and the second bevel gear 24 are meshed with each other.

[0044] A switch valve 25 is provided on the top of the first box body 18. The through-hole group 11 is provided with through holes one, two and three with different diameters. Each concrete transition plate is provided with at least two through holes one, two and three. The groove group is provided with at least 7 grooves, and the lapping rod group 10 is provided with at least 7 lapping rods that cooperate with the grooves.

[0045] At least three locking grooves 26 are provided on the bottom of each precast slab 4. A sinking prevention backing plate 27 is provided below the concrete transition plate 5. A convex strip 28 is provided on the sinking prevention backing plate 27. The length of the sinking prevention backing plate 27 has three different specifications. Blind holes with threads one 29 and blind holes with threads two 30 are provided at both ends of the convex strip 28. The locking grooves 26 and the convex strip 28 cooperate with each other. Rotatable sleeves (not shown in the figure and are prior arts, not elaborated here one by one) are provided at the ends of the small conduit 7 and the seamless steel pipe 8. The rotatable sleeves are hermetically connected to the small conduit 7 or the seamless steel pipe 8, so that when the grouting pipe is connected to the small conduit and the seamless steel pipe, the rotation of the small conduit 7 or the seamless steel pipe 8 is ensured.

[0046] A first fixing block 31 and a second fixing block 32 are provided on each locking groove 26. The first fixing block 31 and the second fixing block 32 are arranged in the middle, so that the sinking prevention backing plate 27 can be quickly and stably connected, improving the stability of the connection between two precast slabs 4. A first locking bolt 33 and a second locking bolt 34 are respectively provided above the first fixing block 31 and the second fixing block 32. The first locking bolt 33 and the second locking bolt 34 play a limiting role. A first movable locking plate 35 and a second movable locking plate 36 are provided at both ends of each locking groove 26. Locking bolts three 37 are provided on both the first movable locking plate 35 and the second movable locking plate 36. The locking bolts three 37 cooperate with the blind holes with threads one 29 and blind holes with threads two 30 on the convex strip 28, so that while being able to expand and contract, a gap can also exist between two precast slabs 4, making it more convenient to drill the small conduit.

[0047] The foldable metal sheet 12 is formed by welding multiple metal sheets, thereby forming a butt joint groove. A support plate (not shown in the figure, and the support plate is an existing technology in current construction) is provided on the butt joint groove, and the support plate is arranged on the side wall of the middle pilot tunnel; countersunk grooves are provided on the first through hole, the second through hole and the third through hole. There is a gap between the small conduit 7 and the seamless steel pipe 8 and the through hole group, and it can rotate with the rotation of the movable power mechanism 1, so as to strengthen the integrity with the side wall of the middle pilot tunnel.

[0048] Through holes with threads that cooperate with the two ends of the first box body 18 are provided on the concrete transition plate 5, and whether the small conduit 7 and the seamless steel pipe 8 rotate can be selected according to the actual construction conditions on site. In the threaded connection adopted in the present invention, threaded sleeves are embedded in the precast concrete slabs.

[0049] As Figure 9 shown, in the construction method of the filling device for the mined - out area under the middle pilot tunnel of a multi - arch tunnel, it includes the following steps:

[0050] S10. After the middle pilot tunnel is excavated and supported, the filling device in the present invention is applied, and the specific position and scope of the mined - out area under the tunnel are explored and verified through drilling and geophysical prospecting;

[0051] S11. Use a drill to drill holes at the two - side edges 1 m away from the bottom of the middle pilot tunnel within the mined - out area range, with a longitudinal spacing of 2 m, and the drilling depth exceeds the loose area at the bottom of the mined - out area by 1 m;

[0052] S12. After the drill is displaced, insert the seamless steel pipe until the bottom of the hole for curtain grouting to form a mortar wall;

[0053] S13. Use a drill to drill small conduits for grouting on the central axis of the middle pilot tunnel within the mined - out area range until the mined - out area below is filled, with a longitudinal drilling spacing of 2 m, and the drilling depth exceeds the loose area at the bottom of the mined - out area by 1 m;

[0054] S14. Randomly drill holes to check whether the filling is dense. If there are still voids, insert seamless steel pipes into the inspection holes for re - grouting, and select another drilling point;

[0055] S15. In the mined - out area range, the middle pilot tunnel is further excavated downward, and a reinforced concrete transition plate is laid.

[0056] In step S12, the steel pipe used is a φ108 seamless steel pipe. The butt joint of the seamless steel pipe is connected by internal screw threads. The non-pressure grouting method is adopted, and the grouting is carried out in an upward manner from bottom to top. The grouting sequence is from the deep side to the shallow side, and from the deep holes to the shallow holes. The length of the first-order grouting hole section should be 0.3m - 0.5m. The length of the second-order hole section can be increased according to the grouting volume and grouting effect, but shall not exceed 1.0m. The main grouting material is M7.5 single-fluid cement slurry, and the water-cement ratio should be selected as 0.7:1 - 1:1. The curtain grouting is carried out according to the principle of sequential and intermittent. After the single-fluid cement slurry reaches the designed grouting pressure, immediately change to grout the cement-sodium silicate double-fluid slurry to seal the hole. The volume ratio of the cement slurry to the sodium silicate slurry can be taken as 1:0.1 - 1:1. Finally, two sealed mortar walls are formed. After the grouting is completed, the steel pipe is pulled out.

[0057] In step S13, φ60 small pipes are drilled with grouting holes with a diameter of 10mm in a plum blossom shape along the pipe circumference at a spacing of 5cm and at a spacing of 20cm in the pipe length direction. The grouting method adopted is grouting until the slurry emerges from the top. After the grouting is completed, the small pipes are not removed and are permanently placed under the middle pilot tunnel together with the corresponding precast slabs.

[0058] In step S10, the geophysical exploration method uses one or more of geological radar, seismic reflection method, and high-density electrical method for detection.

[0059] In step S11, dry drilling is used to form the hole, and no water is allowed to be added during drilling. The hole diameter of the drill is 120mm.

[0060] In step S14, the number of inspection holes is 10% - 20% of the number of grouting holes. The holes are arranged by the method of arranging between the grouting holes or randomly. The positions of some (about 20% - 30%) of the inspection holes are determined on-site by the supervision personnel and acceptance personnel of the construction unit and the receiving unit. The depth of the inspection holes is 2 - 3m deeper than the depth of the adjacent grouting holes.

[0061] In step S15, the transition plate is 40cm thick, made of C20 concrete, with double-layer φ20 steel bars arranged longitudinally and transversely, the steel bar spacing is 25cm, and φ10 stirrups are arranged inside, with a spacing of 75cm. Embodiment

[0062] This embodiment takes the Anyuanshan Tunnel Project on the Middle Ring Road East in Pingxiang City as the background, and takes the filling device for the mined-out area under the middle pilot tunnel of the double-arch tunnel in the present invention as the construction basis to introduce a construction method for the reinforcement treatment of the bottom cavity of the tunnel during the construction of the middle pilot tunnel when the double-arch tunnel crosses the mined-out area.

[0063] Anyuan Tunnel is located near Anyuan Coal Mine in Anyuan Town, Anyuan District, Pingxiang City. It is a continuous arch tunnel with starting and ending pile numbers of K6+514~K6+660, a tunnel length of 146 meters, and a clearance (width×height) of 2-13.25×5 meters. The tunnel site belongs to the low mountain and hilly area, and the unfavorable geology is mainly manifested in the goaf. According to the survey and investigation data, there is unfavorable geology at the bottom of the middle guide tunnel, which is a mule and horse tunnel and a winch road.

[0064] The specific steps of this embodiment are as follows:

[0065] Step 1: After the middle guide tunnel of the construction tunnel is penetrated and initially supported, drilling and geophysical exploration are used to explore the exact location and range of the goaf at the bottom of the tunnel. Specifically, during the excavation of the middle guide tunnel of the tunnel, geological radar is used for advanced geological prediction to detect that there may be goaf below the middle guide tunnel. After the middle guide tunnel is penetrated, the goaf is explored and verified by drilling, seismic imaging and high-density electrical method. In this embodiment, drilling and geophysical exploration were used to find that there is a goaf 4m-14m below the middle guide tunnel in the K6+580~K6+620 section. The middle guide tunnel is horizontally crossed and it is judged to be caused by the collapse of the mule and horse tunnel and the old tunnel.

[0066] Step 2: Drill holes at 0.5m from the edges of both sides of the middle guide hole within the goaf. Use a small down-the-hole drill for dry drilling, with a hole diameter of 120mm and a spacing of 2m. The drilling depth exceeds the bottom of the goaf by more than 1m, and the seamless steel pipe does not rotate at this time.

[0067] Step 3: Drill holes at 0.5m on both sides of the edge of the middle guide hole within the goaf. Use a small down-the-hole drill dry method to drill, with a hole diameter of 120mm, a spacing of 2m, and a drilling depth of more than 1m above the bottom of the goaf. After the drilling rig is moved, insert a φ108 seamless steel pipe until the bottom of the borehole for curtain grouting. Use the bottom-up upward grouting method, with each step lifting 0.5m. M7.5 cement single liquid slurry is used as the main curtain grouting material, and the proportion of cement mortar per cubic meter is: 245kg cement, 1620kg sand, and 225kg water. Curtain grouting is carried out according to the principle of sequential intervals. After the cement single liquid slurry reaches the designed grouting pressure, it is immediately replaced with cement-water glass double liquid slurry to seal the hole to form a curtain. The volume ratio of cement slurry to water glass slurry is 1:1. Finally, two sealed mortar walls are formed. After the grouting is completed, the steel pipe is pulled out, and the seamless steel pipe does not rotate at this time. When the mortar wall is unstable, the method of rotating the seamless steel pipe can be used.

[0068] Step 4: After the mortar wall has initially set, drill the permanently placed φ60 grouting small conduits 6 along the central axis of the middle pilot tunnel, 5 m above the through-hole group, with the drilling depth exceeding 1 m below the bottom of the cavity. Along the circumference of the conduit, drill 10-mm grouting small holes in a plum blossom pattern every 5 mm, and every 20 cm along the length of the conduit. Use pressure grouting, with the grouting material being M7.5 cement mortar. The mix ratio per cubic meter of the cement mortar is: 245 kg of cement, 1620 kg of sand, and 225 kg of water. Each conduit can be grouted simultaneously until the slurry emerges from the top of each steel pipe.

[0069] Step 5: A total of 8 inspection drill holes are arranged, randomly drilled within the goaf area, with 3 of them inspected on-site by the supervision personnel and the acceptance personnel. No cavities are found in the inspection results of all the drill holes.

[0070] Step 6: After the on-site drilling inspection is completed, excavate 40 cm further downward at the bottom of the middle pilot tunnel within the goaf area, and add a reinforced concrete transition plate combination with a thickness of 40 cm. The transition plate uses C20 concrete with a thickness of 40 cm, and is provided with double-layer φ20 longitudinal and transverse steel bars with a spacing of 25 cm, and φ10 stirrups are internally arranged with a spacing of 75 cm.

[0071] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A filling device for the goaf under the middle pilot tunnel of a multi-arch tunnel, Characterized in that: It includes a filling device body and a multi-arch tunnel. The middle part of the multi-arch tunnel is a middle pilot tunnel. A concrete transition plate composed of multiple precast slabs is provided at the bottom of the middle pilot tunnel. The goaf is located below the middle pilot tunnel. Small conduits and seamless steel pipes are provided between the goaf and the concrete transition plate; At one end of each precast slab, there is a groove group, and at the other end, there is a lapping rod group. Through-hole groups are provided on the precast slab, and foldable metal sheets are provided at both ends of each precast slab. Strip-shaped grooves and through-hole threads are provided on the foldable metal sheets. A gear mechanism one is provided at the connection between the small conduit and the seamless steel pipe and the concrete transition plate. A movable power mechanism one is provided on the gear mechanism one and is placed on the concrete transition plate and connected by bolts. The small conduit and the seamless steel pipe both penetrate the concrete transition plate, and detachable limit plates one and detachable limit plates two are provided at the connection between the small conduit or the seamless steel pipe and the concrete transition plate. Detachable rollers are provided between the limit plates one and two and the concrete transition plate. The movable power mechanism one includes a movable box one; A switch valve is provided on the top of the box one. Different-diameter through-holes one, two, and three are provided on the through-hole group. Each precast slab is provided with at least two through-holes one, two, and three. The groove group has at least 7 grooves, and the lapping rod group has at least 7 lapping rods that cooperate with the grooves; At least three locking grooves are provided on the bottom of each precast slab, and an anti-settlement cushion plate is provided below the concrete transition plate. Convex strips are provided on the anti-settlement cushion plate, and the length of the anti-settlement cushion plate has three different specifications. Blind hole threads one and two are provided at both ends of the convex strip. The locking grooves cooperate with the convex strips. Rotatable sleeves are provided at the ends of the small conduit and the seamless steel pipe, and the rotatable sleeves are hermetically connected to the small conduit or the seamless steel pipe, so that when the grouting pipe is connected to the small conduit and the seamless steel pipe, the rotation of the small conduit or the seamless steel pipe is ensured; A fixing block one and a fixing block two are provided on each locking groove. Locking bolts one and two are respectively provided on the fixing block one and the fixing block two. Movable locking plates one and two are provided at both ends of each locking groove. Locking bolts three are provided on both the movable locking plates one and two, and the locking bolts three cooperate with the blind hole threads one and two on the convex strip; The foldable metal sheet is formed by welding multiple metal thin sheets to form a docking groove. A support plate is provided on the docking groove, and the support plate is arranged on the side wall of the middle pilot tunnel; Counterbore grooves are provided on the through-holes one, two, and three. There is a gap between the small conduit and the seamless steel pipe and the through-hole group, and they can rotate with the rotation of the movable power mechanism one.

2. The filling device for the goaf under the middle pilot tunnel of a multi-arch tunnel according to claim 1, Characterized in that: A first limiting plate is provided with a first bevel gear. A base is provided at the bottom of the first box body. A moving groove is provided in the middle of the base, and through holes with threads one and two are provided at both ends of the base. A first motor is provided inside the first box body, and a second bevel gear is provided on the output shaft of the first motor. The first bevel gear and the second bevel gear are meshed with each other.

3. The filling device for the mined - out area under the middle pilot tunnel in a multi - arch tunnel according to claim 2, characterized in that: The concrete transition plate is provided with through - holes with threads that cooperate with and fix the two ends of the first box body. Whether the small conduit and the seamless steel pipe are rotated can be selected according to the actual construction conditions on site.

4. The construction method of the filling device for the mined - out area under the middle pilot tunnel in a multi - arch tunnel according to any one of claims 1 to 3, characterized in that: It includes the following steps: S10. After the middle pilot tunnel is excavated and supported, the filling device is applied, and the specific position and scope of the mined - out area under the tunnel are explored and verified through drilling and geophysical prospecting. S11. Use a drill to drill holes at the two - side edges 1 m away from the bottom of the middle pilot tunnel within the mined - out area, with a longitudinal spacing of 2 m and a drilling depth exceeding the loose area at the bottom of the mined - out area by 1 m. S12. After the drill is displaced, insert the seamless steel pipe until the bottom of the hole for curtain grouting to form a mortar wall. S13. Use a drill to drill small conduits for grouting on the central axis of the middle pilot tunnel within the mined - out area until the mined - out area below is filled. The longitudinal drilling spacing is 2 m, and the drilling depth exceeds the loose area at the bottom of the mined - out area by 1 m. S14. Randomly drill holes to check whether it is filled densely. If there are still voids, insert seamless steel pipes into the inspection holes for re - grouting, and select another drilling point. S15. Within the mined - out area, the middle pilot tunnel is further excavated downward, and a reinforced concrete transition plate is laid.

5. The construction method of the filling device for the mined - out area under the middle pilot tunnel in a multi - arch tunnel according to claim 4, characterized in that: In step S12, the steel pipe used is a φ108 seamless steel pipe. The butt joint of the seamless steel pipe is connected by internal screw threads. The non - pressure grouting method is adopted, and the upward grouting method from bottom to top is used. The grouting sequence is from the deep side to the shallow side, from the deep hole to the shallow hole. The length of the first - order grouting hole section is 0.3 m - 0.5 m. The length of the second - order hole section increases according to the grouting volume and grouting effect, but does not exceed 1.0 m. The main grouting material is M7.5 cement single - liquid grout, and the water - cement ratio is 0.7:1 - 1:

1. The curtain grouting is carried out according to the principle of dividing into sequences and intervals. After the cement single - liquid grout reaches the designed grouting pressure, immediately change to inject cement - water glass double - liquid grout to seal the hole. The volume ratio of the cement slurry to the water glass slurry is taken as 1: 0.1 - 1:1, and finally two sealed mortar walls are formed. After the grouting is completed, the steel pipe is pulled out.

6. The construction method of the filling device for the mined - out area under the middle pilot tunnel in a multi - arch tunnel according to claim 5, characterized in that: In step S13, φ60 small conduits are drilled with grouting holes with a diameter of 10 mm in a plum - blossom shape at intervals of 5 cm along the pipe circumference and 20 cm along the pipe length direction. The grouting method adopted is grouting until the slurry emerges from the top. After the grouting is completed, the small conduits are not taken out and are permanently placed under the middle pilot tunnel together with the corresponding precast slabs.

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