Tunnel inverted arch floor heave improvement construction method

Abstract

The invention belongs to the technical field of tunnel construction, and particularly relates to a tunnel inverted arch floor heave improvement construction method. In order to recover the passage of the tunnel as soon as possible under the condition that a part of constructed inverted arches cannot continuously bear or influence the use due to the structural action of high ground stress or active faults, the technical scheme adopts a step-by-step dismounting and replacing thought to complete the full-ring dismounting and replacement and expanded excavation of a target section, so that the construction efficiency of the tunnel is improved, and the construction cost is reduced. And primary support and secondary lining construction of the tunnel is carried out again.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel construction, and in particular relates to a tunnel invert bottom drum regulation construction method. Background Art

[0002] At present, the operating mileage of domestic highway and railway tunnels continues to grow. During the construction or operation of some tunnels, due to reasons such as geology, construction quality, repeated loads from operating vehicles, etc., serious cracks in the lining, inward extrusion, and ballast uplift are found in many places of the tunnel, which do not meet the requirements for safe tunnel operation; or during the construction stage, due to high ground stress or the tectonic action of active faults, some of the completed inverts cannot continue to bear or are affected in use, and the diseased sections need to be repaired. Summary of the invention

[0003] The purpose of the present invention is to provide a tunnel invert bottom drum regulation construction method to solve the technical problems existing in the prior art such as the bulge and deformation of the tunnel roadbed, the circumferential extrusion damage of the tunnel fault lining, the exposure of the waterproof layer, the large-scale detachment of the arch, the deformation and fracture of a large number of steel bars and the leakage, the damage of the arch power equipment and other serious damages caused by natural disasters, thereby interrupting traffic.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A tunnel invert bottom heave treatment construction method comprises the following steps:

[0006] Step 1: Conduct statistical classification of the degree of damage to the damaged section of the tunnel, confirm the mileage section of the tunnel to be fully replaced, set up a channel and a filling platform for the mileage section to be fully replaced, and carry out temporary reinforcement operations; the length of the advanced second lining removal construction shall not be less than 20m;

[0007] Step 2, replace the upper step, the lower step, and the inverted arch in sequence, make a groove of not less than 3m in the replacement section as a working opening, remove the molded concrete and the initial support, and expand the excavation; after the expansion, the maximum height of the upper step is 8-9m, the height of the lower step is 4-5m, and the excavation depth of the inverted arch is 3-4m;

[0008] Step 3: The lower step replacement construction is carried out 20 meters after the upper step, and the invert arch removal construction is carried out 20 meters after the lower step; the secondary lining construction is started 18 meters after the invert arch filling construction.

[0009] In the technical solution of the present invention, in order to restore the tunnel to traffic as soon as possible, in the case where part of the completed invert arch is seriously unable to continue to bear load or is affected by the tectonic action of high ground stress or active faults, the technical solution of the present invention adopts a step-by-step replacement idea to complete the full-ring replacement and expansion of the target section, and re-construct the primary support and secondary lining of the tunnel.

[0010] As a preferred embodiment of the present invention, in step 1, the temporary reinforcement work needs to be constructed in advance. After the top is found by an excavator, a steel frame arch is set on the arch wall for temporary reinforcement. The section is dismantled for radial grouting. The arch steel frame is manually erected on a dismantling stand, and the locking feet are constructed by a manual hand-held pneumatic drill. The arch frame and the arch wall are intermittently wedged with steel wedges or wooden squares. After the radial grouting drilling, a small grouting tube is installed for grouting. The grouting range is: to ensure that there is at least a 3m reinforcement area around after the expansion, and to dynamically adjust the grouting range of each section according to the expansion section.

[0011] As a preferred embodiment of the present invention, in step 2, the tunnel construction adopts the open hole buffer hole expansion as the construction channel into the tunnel. After the rails and fasteners in the tunnel are removed, the grooves between the track plates and the track plates are filled with the slag backfill method of the original tunnel excavation. After filling, it is used as a construction and transportation channel, and a staggered lane is set every 100m.

[0012] Fill the working surface of the replacement area, fill the entire filling area, set up slopes on both sides of the filling area for transport vehicles to go up and down, and the highest filling position is at least 6m above the arch to meet the requirements of crushing head removal and temporary reinforcement of lining. After the full ring is replaced, the filling surface is roughened to meet the design elevation.

[0013] As a preferred embodiment of the present invention, in step 2, when grooving the working surface, the grooving length is not less than 3m, and construction is carried out according to different excavation. Mechanical demolition is first performed, supplemented by radial drilling and blasting construction. The secondary lining is blasted first, followed by blasting the formwork lining and initial support, and finally the excavation is carried out.

[0014] Once the excavation is completed, the initial support will be carried out immediately. After the initial support is completed, the front and rear end areas of the current support will be advanced supported. Since the minimum excavation is 1.8m, the excavation gantry needs to be assembled and dismantled each time. When the trench reaches 9m, the gantry does not need to be assembled and dismantled repeatedly.

[0015] Preferably, in step 3, the replacement length of the initial support unit of the upper step does not exceed 2m. After the upper step is replaced for 21m, the lower step is replaced and the initial support of the lower step is expanded. The length of each replacement is no more than 2m. After the lower step is constructed for 24m, the invert arch is removed and the initial support of the invert arch is expanded. The length of each construction is 3m. After the invert arch is replaced for 6m, the invert arch is cast and filled. The invert arch casting and filling are carried out by one-time layered casting.

[0016] After the invert and filling construction of 18m, the second lining construction began. The second lining was constructed with a lining trolley, with each construction length of 6m. A 12m waterproof board rack was processed as a seismic layer, waterproof board, and second lining steel bar installation stand. After the lining construction of the ditch cable trough on this working surface was completed for 40m, small wooden formwork was used for synchronous construction.

[0017] Further preferably, the cast-in-place concrete and initial support are removed by using an excavator with a crushing head installed at the same time, and hydraulic shears are used to cut the steel bars and steel sections, and the upper step is removed first, which is actually the lower step.

[0018] The initial support removal is carried out in a working cycle of 2m and each removal is not more than 2.3m. The initial support removal of the lower step is carried out in a working cycle of 2m and each removal is not more than 2.3m. Within the current removal range, the temporary supporting arch frame will be removed first and moved to the rear for installation.

[0019] The width of the slot excavated in each cycle is 2 to 3m, and it is expanded outward according to the changed design section size (the second lining is thickened, the profile is enlarged, and 10cm deformation is reserved).

[0020] After the section is excavated, the section contour is measured and individual intrusion areas are processed to ensure a 15cm reserved deformation.

[0021] Each working face of the primary support removal is equipped with a breaker. Each working face is broken and removed, expanded and excavated, and the arch frame is installed, and the anchor spraying support is operated in a continuous manner. In order to improve the utilization rate of the machinery, after providing enough space for the secondary lining removal, during the arch frame installation and anchor spraying operations, the machine is chiseled to jump forward two plates to open notches for the primary support removal operation, and the bench is arranged to prepare for the arch frame cutting operation and anchor spraying installation operation at that location.

[0022] Preferably, when the initial support is removed, since the tunnel has already reached a stable state, further removal will inevitably cause new stress distribution. After the removal is completed, the surrounding rock should be sealed again in time, and monitoring points should be deployed in time to obtain original data for observation.

[0023] When the deformation of the surrounding rock increases rapidly, the daily relative clearance change exceeds 5mm and the cumulative change reaches 100mm, the removal of the secondary lining and primary support should be stopped, and the focus should be on strengthening observation and paying close attention to changes in the support; after the initial support convergence reaches 15cm (that is, 15cm of reserved deformation is consumed) or the monitored steel frame stress is close to the steel frame bearing capacity requirement and the relative change still exceeds 1mm / day, the support must be strengthened by increasing the thickness of the sprayed concrete, spraying 5cm thick mesh sprayed concrete, increasing the length and number of prestressed grouting anchors, increasing the strength and spacing of steel supports, or temporary steel supports.

[0024] As the preferred technical solution of the present invention, the initial support installation construction: the upper step adopts a dismantling platform and increases the height to meet the needs of manual installation of the steel frame, and a vehicle passage is left at the bottom.

[0025] Preferably, the main components of the test stand include: an I-beam portal frame, side "wings", a bottom longitudinal beam, a steel mesh, a telescopic steel pipe, a Feng Shui pipe system, a traction wire rope, etc.

[0026] Preferably, steel mesh, anchor rods, uprights, locking feet, advance, and shotcrete can all be constructed on the scaffold. The height of the lower step arch is about 4m. Use the formed scaffolding to manually install the steel frame and steel mesh, connect the joint bolts, remove the accumulated water at the arch foot, loosen the slag and pad it, spray it in time after the excavation is completed, and then spray concrete again after the construction locks the feet. The excavation and installation of the lower step arch are staggered on the left and right sides, with a staggered distance of not less than 3m, and the upper step arch must not be suspended at the same time. An anti-misalignment joint is set at 6m, with a joint width of 5cm, and asphalt hemp is used to fill it. Before construction, the four joints should be aligned on the premise that the invert and the second lining layout meet the contact network groove.

[0027] As the preferred technical solution of the present invention, the construction of the demolition and expansion of the inverted arch is as follows: after the grouting of the inverted arch, after the monitoring and measurement of the arch wall shows no abnormality, the inverted arch is replaced. The original design filling layer is C25 plain concrete, the inverted arch is reinforced concrete, and the initial support means a steel frame. Mechanical demolition, assisted by air gun drilling, loosening blasting method demolition, hydraulic shear cutting steel frame and steel bars, lag 24m behind the lower step, after the original lining is demolished, the excavator is used to expand the excavation according to the designed section, and after removing the false slag, the inverted arch frame is installed, and the initial support is closed by spraying concrete. After 3m, the reconstructed inverted arch is mechanically demolished, assisted by longitudinal drilling and loosening blasting. After 6m, the earthquake-proof layer, inverted arch steel bars, construction inverted arch, partition and filling are installed in time.

[0028] As a preferred technical solution of the present invention, specifically, the construction process of the earthquake-proof layer located at the invert is:

[0029] (1) Vibration isolation materials are laid at the bottom of the invert. The vibration isolation materials are made of rubber isolation bearings and polyurethane foam boards. The exposed steel bar heads and other protrusions on the primary support base are cut off and water is sprinkled to soak them.

[0030] (2) When applying cement mortar, the flatness should meet the depth-to-length ratio between the two protrusions:

[0031] D / L≤1 / 50 (D is the depth of the depression between two adjacent convex surfaces of the base surface after cement mortar leveling; L is the distance between two adjacent convex surfaces of the base surface after cement mortar leveling, L is not greater than 1m).

[0032] (3) The polyurethane foam panels are evenly arranged at the bottom of the invert and fixed with long steel nails with gaskets. The installation gap between the panels is controlled to be 5 to 10 mm. Then, the rubber seismic isolation bearings are embedded in the middle frame of the polyurethane foam panels according to the designed layout position, and the bottom surface of the bearings is firmly fixed with epoxy mortar.

[0033] The earthquake-proof layer and waterproof board are laid manually without nails on a working platform.

[0034] Preferably, the invert and the invert filling are cast in one go and meet the following requirements:

[0035] 1. The invert arch filling and invert arch concrete are poured at one time, using C35 polypropylene fiber concrete (parameter 0.9kg / m3).

[0036] 2. In order to effectively connect the inverted arch filling partition with the inverted arch, the ends of the partition steel bars on both sides shall be anchored in the straight section of the inverted arch for a length of not less than 60 cm, and a straight hook with a length of 15 cm shall be added.

[0037] 3. When pouring the inverted arch filling and the inverted arch concrete as a whole, it should be poured in layers, and the thickness of each layer shall not be less than 20cm and not more than 50cm.

[0038] 4. Concrete is poured directly into the mold through a tank truck through a chute. The height of the chute outlet from the concrete pouring surface should not exceed 2m.

[0039] 5. Concrete should be compacted by using an inserted high-frequency vibrator. The insertion points of the inserted vibrator should be evenly arranged without missing any vibrations. The movement distance of each insertion point should not be greater than 1.5 times the effective radius of the vibrator. The inserted vibrator should be inserted quickly and pulled out slowly. The overlap depth with the lower layer of concrete should be not less than 10cm. The vibration time for each time should be 20s to 30s. Stop the vibration when the concrete does not sink significantly, there are no bubbles, and it begins to overflow.

[0040] 6. During the integral pouring construction of the invert and filling, embedded parts such as drainage trenches and inspection wells should be fixed with steel bar fixing brackets and other measures.

[0041] 7. The invert and filling concrete should be cured for no less than 7 days after demoulding, and should be covered and kept moisturized.

[0042] The arch formwork is reinforced by internal tension and external support. The internal tension adopts φ16 steel bars + double φ42 small pipes, arranged in a plum blossom shape with a spacing of 2m*2m, and the external support adopts wooden planks and φ76 steel pipes.

[0043] Preferably, the secondary lining construction is carried out after the surrounding rock and initial support have converged and stabilized, with a delay of 18m in the construction of the invert arch, and is equipped with a concrete transport truck and concrete pump.

[0044] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0045] In the technical solution of the present invention, the tunnel lining is repaired in stages by dismantling and excavating the tunnel in different areas, which achieves rapid treatment of tunnel diseases and greatly shortens the construction period. During the construction process, no damage is caused to the original lining structure. For the tunnel mileage sections with serious damage, the whole tunnel is replaced. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 It is a working surface layout diagram of the construction section of the present invention;

[0047] Figure 2 It is a schematic diagram of the step height of the full ring replacement section of the present invention;

[0048] Figure 3 It is a schematic diagram of the cross-sectional structure before and after the construction of the present invention;

[0049] Figure 4 Schematic diagram of sections corresponding to the construction process of the tunnel mileage section of the present invention;

[0050] Figure 5 This is a schematic diagram of the invert base structure;

[0051] Figure 6 This is the position relationship diagram of the rubber seismic isolation bearing and the polyurethane foam board in the inverted arch vibration isolation layer;

[0052] Icons: 1- tunnel center line; 2- right center line; 3- left center line; 4- first working surface; 5- second working surface; 6- outer contour of reconstructed cross-section structure; 7- inner contour of reconstructed cross-section structure; 8- small guide tube; 9- steel flower pipe; 10- upper step; 11- lower step; 12- invert; 13- waterproof layer; 14- initial support of invert; 15- rubber seismic isolation bearing; 16- polyurethane foam board; 17- initial support; 18- second lining working area; 19- waterproof board laying area; 20- invert replacement area; 21- lower step working area; 22- upper step working area. DETAILED DESCRIPTION

[0053] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0054] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0055] Example 1

[0056] This embodiment provides a construction method for the treatment of tunnel invert bottom heave, which is applied in practice in a tunnel section K1971+341 to K1971+427 where the damage was extremely serious.

[0057] Specifically, the construction geographical environment of this practice is poor and the climate is harsh. The tunnel is a double-line single-hole tunnel with a large cross-section. The original design surrounding rock is mainly IV and V grade surrounding rock, and the surrounding rock is broken. Affected by the earthquake, the tunnel has a 2m left-handed dislocation and the arch is squeezed and uplifted by a maximum of about 2.0m. The stability of the surrounding rock of the tunnel is destroyed, the tunnel drainage facilities are damaged, and the outlet drainage tunnel is blocked at the full ring replacement section. The daily water inflow reaches more than 25,000 cubic meters. The safety risk of replacement construction is extremely high, and it is very easy to cause disasters such as landslides and water inflows. The full ring replacement section is asymmetrical 205m 2 Large-section demolition and replacement, the excavation width is expanded to 1.8 to 4.2 m, and the tunnel excavation height reaches 15.6 m, which poses a great safety risk.

[0058] For the restoration of tunnel damage in this mileage section, this embodiment provides the following construction plan:

[0059] The mileage section from K1971+341 to K1971+427 is divided into two working surfaces, such as Figure 1 As shown, the tunnel is a double-track transportation channel, with the tunnel centerline 1 in the middle, the left centerline 2 on one side, and the right centerline 3 on the other side. The first working surface 4 is located at K1971+341, and the severely damaged section from K1971+341 to +378 is being dismantled and replaced. The second working surface 5 is located at K1971+378, and the most severely damaged section from K1971+378 to +427 is being constructed. The Φ108 advanced large pipe shed construction from K1971+385 to +427 is being carried out in advance.

[0060] The dismantling and replacement construction starts from the first working surface 4, and the second working surface 5 carries out advanced support construction in advance.

[0061] The steps include:

[0062] Step 1: Conduct statistical classification of the degree of damage to the damaged section of the tunnel, identify the mileage section of the tunnel for full-loop replacement, build the construction channel to the replacement area, and after the replacement platform is filled, the tunnel construction adopts the open hole buffer hole expansion as the construction channel into the tunnel, removes the rails and fasteners in the tunnel, and uses the original tunnel excavation slag backfill method to fill the track plate and the grooves between them. After filling, it is used as a construction and transportation channel, and the mileage section of the full-loop replacement is pre-reinforced. In the pre-reinforcement operation, the length of the advanced second lining removal construction is not less than 20m; Figure 2 It can be confirmed that after the full ring replacement is completed, the reconstructed cross-sectional structure outer contour 6 and the reconstructed cross-sectional structure inner contour 7 are expanded compared with the original tunnel cross-section.

[0063] Specifically, during the pre-reinforcement construction process, the top is first found, and then the tunnel arch wall is temporarily reinforced with a steel frame arch. The replacement area is radially grouted. After the radial grouting drilling, a small grouting pipe is installed for grouting. The grouting range at least ensures that there is a 3m reinforcement area around the expansion and excavation. The grouting range of each section is dynamically adjusted according to the expansion section. In this scheme, the arch wall adopts H175 steel frame temporary arch fixing measures: 4 φ42 locking foot anchor pipes are set on each side of each steel frame wall foot, and each one is 4m long. In order to strengthen the integrity of the steel frame, two φ22 steel frame fixing steel bars (each 0.65m long) are set at the steel frame joint position and welded firmly to the steel frame; a full-length 32c channel steel is set on both sides of the bottom of the steel frame: the steel frame is longitudinally connected with I-16 longitudinal connection, and the circumferential spacing is 1m.

[0064] Radial grouting parameters of K1971+341~+427(86m) section: φ42 small duct is used for radial grouting of arch wall. The length of small duct 8 is dynamically adjusted according to the grouting range. The length of a single duct is 0.5m shorter than the grouting range, and the spacing is 2m*2m. φ108 steel tube 9 is used for radial grouting of invert arch. The length of a single steel tube 9 is 8m, and the spacing is 2.3m*2.3m.

[0065] The grouting material used is sulphoaluminate cement, and the grouting pressure is: within about 1.5MPa for the arch wall and about 2-3MPa for the invert arch. During the grouting process, skip-hole interval grouting is carried out, and compaction-type grouting measures are implemented. If grouting occurs during the grouting process, close the orifice valve or block the orifice, and open the valve again after the grouting of other holes is completed, until each hole reaches the grouting end standard. The orifice pipe should be buried firmly and have good grouting stopping measures. Single-hole end standard: When the designed final pressure is reached and grouting continues for more than 10 minutes, the grouting volume of a single hole is less than 20L / min. Full-section end grouting standard: All grouting holes have met the single-hole end conditions and there is no leakage. The schematic diagram of tunnel radial grouting is shown in Figure 2 shown.

[0066] Step 2: Replace in three steps (upper step 10, lower step 11, invert 12), open a 3m slot in the replacement area as a working opening, and simultaneously carry out molded concrete and initial support removal and excavation. After removal and excavation, immediately carry out initial support 17 construction. Schematic diagram of step height in the tunnel is shown in the figure below: Figure 3 shown.

[0067] (More specifically, according to different expansions, construction is carried out in three mechanical demolitions, supplemented by radial drilling and blasting. The first blast is for the secondary lining, the second blast is for the molded lining and initial support, and the third is for expansion. After the expansion is in place, the initial support 17 is immediately carried out, and after the support is completed, the two ends are advanced support. Since the minimum expansion is 1.8m, the excavation stand needs to be assembled and dismantled each time. When the slot reaches 9m, the stand can be assembled and dismantled without repetition.)

[0068] like Figure 4 It is a schematic diagram of the construction process in the mileage direction of the tunnel: from left to right: the second-floor working area 18, the waterproof board laying area 19, the invert arch replacement area 20, the lower step working area 21 and the upper step working area 22.

[0069] Further preferably, the cast-in-place concrete and initial support removal are carried out simultaneously by using an excavator with a crushing head installed, and hydraulic shears are used to cut the steel bars and steel sections. The process is divided into upper and lower steps, and the height of the upper step after excavation is expanded is 8.3m.

[0070] The initial support removal is a 2m work cycle and each removal is no more than 2.3m. The lower step initial support removal is a 2m work cycle and each removal is no more than 2.3m. The temporary support arch frame will be removed within the current removal range and moved to the rear for installation. The width of the slot excavated in each cycle is 2 to 3m, and it is expanded according to the changed design section size (the second lining is thickened, the outline is enlarged, and 10cm deformation is reserved).

[0071] Specifically, the length of each replacement of the primary support of the upper step is no more than 2m. After the upper step is replaced for 21m, the lower step will be replaced and the primary support of the lower step will be expanded. The length of each replacement is no more than 2m. After the lower step is constructed for 24m, the arch removal and primary support operation will begin. The construction length is 3m each time. After the replacement is completed for 6m, the arch pouring and arch filling operation will be carried out immediately. The pouring and arch filling will be poured in layers at one time. After the arch and filling construction is 18m, the secondary lining construction will begin. The secondary lining will be constructed by a lining trolley. The construction length is 6m each time. A 12m waterproof board rack will be processed as a seismic layer, waterproof board, and secondary lining steel bar installation stand.

[0072] The initial support construction method is:

[0073] The upper step adopts the method of dismantling the scaffold and increasing the height for initial support. The initial support includes steel mesh, anchor rods, stand, foot lock, advance, shotcrete and other operations. The height of the lower step arch is about 4m. The steel frame and steel mesh are installed manually using the formed scaffold, and the joint bolts are connected. The water at the arch foot is cleared and the loose slag is padded. After the excavation is completed, the initial spraying is carried out in time, and the construction is locked and then the concrete is sprayed again. The excavation and installation of the lower step arch are staggered on the left and right sides, and the staggered distance is not less than 3m, and the upper step arch shall not be left hanging. Anti-stagger joints are set at 6m, with a width of 5cm, and asphalt hemp tendons are used to fill them.

[0074] After the invert grouting, the invert was replaced after the monitoring and measurement of the arch wall showed no abnormality. The original design filling layer was C25 plain concrete, the invert was reinforced concrete, and the primary support contained a steel frame. Mechanical demolition, assisted by air gun drilling, loosening blasting, and hydraulic shears were used to cut the steel frame and steel bars. The demolition of the invert lagged behind the lower step by 24m. After the original lining was demolished, the excavator was used to expand the excavation according to the designed section. After removing the false slag, the invert arch frame was installed and the initial support was closed with sprayed concrete. After 3m, the reconstructed invert was mechanically demolished, assisted by longitudinal drilling and loosening blasting. After 6m, the earthquake-proof layer, invert steel bars, construction invert, partition and filling were installed in time.

[0075] The construction of the inverted arch is as follows: after the flatness of the initial support base surface of the inverted arch is checked and qualified, the vibration isolation material is constructed at the bottom of the inverted arch, and the vibration isolation material includes a rubber vibration isolation support 15 and a polyurethane foam board 16. The polyurethane foam board is evenly arranged at the bottom of the inverted arch and fixed with long steel nails with gaskets, and the installation gap between the boards is controlled to be 5-10mm; then the rubber vibration isolation support is embedded in the middle frame of the polyurethane foam board according to the designed layout position, and the bottom surface of the support is firmly fixed with epoxy mortar. Among them, the flatness should meet the depth-to-length ratio D / L between the two protrusions ≤1 / 50 (D-the depth of the recess between the two adjacent convex surfaces of the base after cement mortar leveling; L-the distance between the two adjacent convex surfaces of the base after cement mortar leveling, L is not more than 1m.

[0076] After the construction of the inverted arch base is completed, the inverted arch is poured and filled at one time. C35 polypropylene fiber concrete is used for pouring; when the inverted arch filling and the inverted arch concrete are poured as a whole, they are poured in layers, and the thickness of each layer shall not be less than 20cm and not more than 50cm.

[0077] The concrete is compacted by using an inserted high-frequency vibrator. The insertion points of the inserted vibrator should be evenly arranged without missing any vibrations. The movement distance of each insertion point should not be greater than 1.5 times the effective radius of the vibrator. The inserted vibrator should be inserted quickly and pulled out slowly. The overlap depth with the lower layer of concrete should be not less than 10cm. The vibration time for each time should be 20s to 30s. The vibration should be stopped when the concrete does not sink significantly, there are no bubbles, and it begins to overflow.

[0078] During the construction of the secondary lining: the seismic layer and waterproof board are constructed by manual nailless laying on the work platform. The invert closely follows the working face. In order to solve the interference problem between the invert pouring and mucking, an invert trestle is used. The tunnel lining adopts a hydraulic lining trolley. Each working face is equipped with a 6.3m long lining trolley (newly manufactured). The lining is constructed after the surrounding rock and initial support converge and stabilize, and the invert is constructed 18m behind, and a concrete transport truck and concrete delivery pump are equipped.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A tunnel invert bottom heave treatment construction method, characterized in that: The steps include: Step 1: Conduct statistical classification of the degree of damage to the damaged section of the tunnel, confirm the mileage section of the tunnel to be fully replaced, set up a channel and a filling platform for the mileage section to be fully replaced, and carry out temporary reinforcement operations; the length of the advanced second lining removal construction shall not be less than 20m; Step 2, replace the upper step, the lower step, and the inverted arch in sequence, make a groove of not less than 3m in the replacement section as a working opening, remove the molded concrete and the initial support, and expand the excavation; after the expansion, the maximum height of the upper step is 8-9m, the height of the lower step is 4-5m, and the excavation depth of the inverted arch is 3-4m; Step 3: The lower step replacement construction is carried out 20 meters after the upper step, and the invert arch removal construction is carried out 20 meters after the lower step; the secondary lining construction is started 18 meters after the invert arch filling construction.

2. The tunnel invert bottom heave treatment construction method according to claim 1, characterized in that: In step 1, the temporary reinforcement work needs to be constructed in advance. After the top is found by an excavator, a steel frame arch is set on the arch wall for temporary reinforcement. The replaced section is subjected to radial grouting. The grouting range is to ensure that there is at least 3m of reinforcement area around after the expansion, and the grouting range of each section is dynamically adjusted according to the expansion section.

3. The tunnel invert bottom heave treatment construction method according to claim 2 is characterized in that: In step 1 and step 2, the tunnel construction adopts the open hole buffer hole expansion as the construction channel into the tunnel. After removing the rails and fasteners in the tunnel, the grooves between the track plates and the track plates are filled with the slag backfilling method of the original tunnel excavation. After filling, it is used as a construction and transportation channel. The working surface of the replacement area is filled, and the filling area is fully filled. Slopes are set on both sides of the filling area for transport vehicles to go up and down. The highest filling position is at least 6m above the arch height to meet the requirements of crushing head removal and temporary reinforcement of the lining.

4. The tunnel invert bottom heave treatment construction method according to claim 1, characterized in that: The length of each replacement and expansion of the initial support shall not be less than 2m. When the replacement length of the upper step is more than 20m, the lower step replacement operation and the expansion of the initial support of the lower step will be started. When the construction length of the lower step is greater than 24m, the invert removal operation and the initial support construction of the lower step will be started. The length of each construction is 3m. When the replacement length of the invert reaches 6m, the casting and filling of the invert will be started. The casting and filling of the invert are carried out by one-time layered casting.

5. The tunnel invert bottom heave treatment construction method according to claim 1, characterized in that: In the step 2, when grooving the working surface, the grooving length is 3m, and construction is carried out according to different expansion excavations, mechanical demolition, assisted by radial drilling and blasting construction, first blasting the secondary lining, then blasting the formwork lining and initial support, and finally expanding the excavation. After the expansion is in place, initial support is immediately carried out. After the initial support is completed, advance support is carried out on the front and rear end areas of the current support.

6. The tunnel invert bottom heave treatment construction method according to claim 5, characterized in that: The cast-in-place concrete and initial support are removed simultaneously using an excavator with a crushing head installed, and hydraulic shears are used to cut the steel bars and steel sections. The upper step is removed first, followed by the lower step.

7. The tunnel invert bottom heave treatment construction method according to claim 6, characterized in that: The initial support removal is carried out in a working cycle of 2m and each removal is not more than 2.3m. The initial support removal of the lower step is carried out in a working cycle of 2m and each removal is not more than 2.3m. Within the current removal range, the temporary supporting arch frame will be removed first and moved to the rear for installation.

8. The tunnel invert bottom heave treatment construction method according to claim 1, characterized in that: During the initial support process, the upper step is carried out using a dismantling and replacement scaffold, and the lower step arch frame height is about 4m. The steel frame and steel mesh are manually installed using the formed scaffolding, and the joints are bolted. The accumulated water is removed from the arch foot, and the loose slag is padded after it is compacted. After the excavation is completed, the initial spraying is carried out in time, and the concrete is sprayed again after the construction foot is locked.

9. The tunnel invert bottom heave treatment construction method according to claim 7, characterized in that: The secondary lining construction is carried out after the surrounding rock and initial support are converged and stabilized, and the construction of the back arch is delayed by 18m.

10. The tunnel invert bottom heave treatment construction method according to claim 1, characterized in that: In step 2, after the initial support is removed, the surrounding rock should be re-erected in time, and monitoring points should be deployed in time to obtain original data for observation.

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