A method for repairing tunnel structure after earthquake

Abstract

The invention discloses a method for repairing a tunnel structure after an earthquake. The method not only facilitates the laying of a waterproof layer in sections by setting an annular steel sleeve arch and replacing a vertical temporary support by segmented dismantling, thereby ensuring the waterproof effect of the tunnel invert arch and ensuring the safety and quality of the construction of a large-section tunnel invert arch lining concrete with annular temporary support; but also effectively solves the safety factor of the stratum during the repair construction process by grouting and reinforcing the damaged stratum around the tunnel, thereby providing a safety guarantee for the smooth progress of the tunnel repair work; at the same time, by optimizing the repair method and requirements of the damaged section of the tunnel, especially the removal and replacement sequence and requirements of the initial support or the invert arch, the damaged structure can be quickly and safely removed and replaced; the repair method can realize the repair of the tunnel with a damaged structure, and has the advantages of being scientific and reasonable, technically rigorous, highly targeted, low in construction cost and good in social benefits.

Description

Technical Field

[0001] The present invention relates to the field of tunnel engineering, in particular to the field of tunnel repair engineering, and in particular to a method for repairing a tunnel structure after an earthquake. Background Art

[0002] Generally speaking, due to the particularity of the tunnel's location and structure, the impact of earthquakes on tunnel structures will not be too great. The impact of earthquakes on tunnels is mainly reflected in local cracking, broken blocks and / or cracks in the tunnel lining structure. To repair these effects, the main method is to reinforce the lining surface by applying a sleeve lining.

[0003] However, for tunnels located in fault zones, after a strong earthquake, there may be problems such as tunnel structure dislocation, arch uplift deformation, and even structural fracture. For tunnels whose structures have been damaged, conventional tunnel lining reinforcement treatment methods are difficult to complete the repair of such tunnels. Therefore, there is an urgent need for a method that can repair tunnel structure dislocation, arch uplift deformation, and even structural fracture. Summary of the invention

[0004] The purpose of the present invention is to overcome the defects of existing tunnel repair methods that it is difficult to repair the problems of tunnel structure dislocation, arch uplift deformation and even structural fracture, and propose a method for repairing tunnel structure after earthquake. The repair method is based on the structure of the tunnel and the characteristics of tunnel damage, combines the tunnel repair and tunnel construction methods, and performs targeted optimization and adjustment. The repair method can quickly and safely realize the repair of the tunnel with a damaged structure, and has the advantages of scientific rationality, rigorous technology, strong pertinence, low construction cost and good social benefits.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides a method for repairing a tunnel structure after an earthquake, comprising the following steps:

[0006] Step 1: Find the damaged part of the tunnel structure and construct a circular steel arch at the damaged part of the tunnel structure;

[0007] Step 2: Under the support of the annular steel sleeve arch, radially drill holes and inject grouting to reinforce the surrounding rock of the tunnel from the steps on the tunnel arch wall; then, remove the secondary lining and initial support of the steps on the tunnel arch wall one by one, and expand the excavation while removing the initial support. After the expansion is completed, re-apply the initial support of the tunnel; after the upper step of the arch wall is removed and the initial support length is reconstructed to be not less than 21m, radially inject grouting to reinforce the surrounding rock on both sides of the lower step of the tunnel arch wall. After reinforcement, remove the lining and initial support of the lower step of the tunnel arch wall one by one, and remove the initial support. Excavation can be carried out while supporting, and the initial support of the tunnel can be re-applied after the excavation is completed; after the initial support reconstruction length of the step under the arch wall is not less than 24m, radial grouting is used to reinforce the outer soil layer of the tunnel invert, and the original filling layer, invert and initial support structure of the tunnel are removed section by section. Excavation can be carried out while removing the initial support, and the initial support of the tunnel can be re-applied after the excavation is completed. After the initial support length of the invert is not less than 6m, the invert thermal insulation and shock-absorbing layer is first laid on the initial support of the invert, and then the tunnel invert and filling layer are re-applied;

[0008] Step 3: After the reconstruction length of the invert and filling layer is not less than 24m, assemble the tunnel arch wall secondary lining trolley, first lay the thermal insulation and shock absorption layer and waterproof board on the initial support of the arch wall, and then reconstruct the tunnel arch wall secondary lining concrete;

[0009] Step 4: Move the annular steel arch to the next location where the tunnel structure is damaged, and repeat steps 2-4 until all damaged locations of the tunnel structure are repaired.

[0010] The invention discloses a post-earthquake tunnel structure repair method, which not only facilitates the laying of waterproof layers in sections by setting annular steel sleeve arches and replacing vertical temporary supports by segmented dismantling, thereby ensuring the waterproof effect of tunnel inverts and the safety and quality of large-section tunnel invert lining concrete construction with vertical temporary supports; but also effectively solves the safety factor of the stratum during the repair construction process by grouting and reinforcing the damaged stratum around the tunnel, thereby providing a safety guarantee for the smooth progress of the tunnel repair work; at the same time, by optimizing the repair method and requirements of the damaged section of the tunnel, especially the removal and replacement sequence and requirements of the initial support or the invert, the damaged structure can be quickly and safely removed and replaced; the repair method can realize the repair of the tunnel with a damaged structure, and has the advantages of being scientific and reasonable, technically rigorous, highly targeted, low in construction cost and good in social benefits.

[0011] Among them, before step (1), it also includes looking up relevant information about the tunnel to be repaired, understanding the tunnel structure, and determining the specific location of the tunnel structure damage and assessing the degree of damage, in preparation for the repair work; by consulting the tunnel information and understanding the degree of damage, confirming the actual situation of the tunnel to be repaired, and making preparations for the repair of the tunnel, it has a positive effect on ensuring the smooth and safe repair of the tunnel.

[0012] Preferably, in step (1), the longitudinal spacing of the arch wall of the steel arch is 0.6m; fixed steel bars are fixedly arranged at the joint positions of the steel frame; longitudinal channel steels are arranged on both sides of the bottom of the steel frame; the steel frames are connected longitudinally by longitudinal welding of steel sections, with a circumferential spacing of 1.2m; the preferred steel arch structure has good integrity, stable structure, good support and fast erection speed.

[0013] Preferably, the longitudinal segment length of the steel arch is 6m.

[0014] Among them, preferably, a locking foot anchor pipe is also provided at the foot of the steel frame wall of the steel arch; the setting of the locking foot anchor pipe can better fix the steel arch and facilitate grouting reinforcement. At the same time, after the radial grouting reinforcement of the tunnel, the locking foot anchor rod is cut off to facilitate the longitudinal movement of the steel arch and realize the rapid reuse of the steel arch.

[0015] Preferably, a protective net is hung on the arch portion of the steel sleeve arch; the provision of the protective net can reduce potential safety hazards and improve construction safety.

[0016] Wherein, in step (2), the depth of asymmetric grouting reinforcement is determined according to the characteristics of the distorted and deformed section of the tunnel, and the grouting range is at least guaranteed to have a 3m reinforcement area around after the expansion; the grouting reinforcement can dynamically adjust the grouting range of each section according to the expansion section; if grouting occurs during the grouting process, the orifice valve is closed or the orifice is blocked, and the valve is opened after the grouting of other holes is completed, until each hole reaches the grouting end standard.

[0017] Among them, the standard for ending grouting of a single hole in the grouting reinforcement is: when the designed final pressure is reached and grouting is continued for more than 10 minutes, the grouting volume of a single hole is less than 20L / min.

[0018] Among them, the standard for completing grouting in the entire section during the grouting reinforcement is: all grouting holes have met the single-hole completion conditions and there is no leakage.

[0019] Among them, preferably, in the grouting reinforcement, the grouting material is sulphoaluminate cement, the grouting pressure is not more than 1.5MPa, the grouting adopts skip-hole interval grouting, and the compaction type grouting is implemented; the preferred grouting parameters result in better grouting reinforcement effect and higher efficiency.

[0020] Among them, in step (2), preferably, during the repair process of the upper step, the lower step and the invert, the secondary lining structure or the invert structure is first demolished after the length is greater than 20m, and then a 3m wide groove is opened in the replacement area, and then the initial support is demolished and excavated, and a new initial support is applied after the excavation is completed; during the demolition and excavation process, mechanical loosening blasting can be used simultaneously; the preferred repair sequence and method are faster and safer.

[0021] Among them, preferably, the length of each repair of the initial support of the upper step is not more than 2m, and the initial support construction is carried out immediately after each demolition and expansion; 21m after the upper step is dismantled and replaced, the repair of the lower step is started, and the length of each repair of the initial support of the lower step is not more than 2m, and the initial support construction is carried out immediately after each demolition and expansion; 24m after the initial support construction of the lower step, the demolition of the invert arch is started, and the length of each repair of the initial support of the invert arch is 3m, and the initial support construction is carried out immediately after each demolition and expansion; the preferred demolition and replacement requirements are faster, safer, and the repaired tunnel performance is better.

[0022] Among them, in step (2), preferably, the flatness of the new initial support after the repair is completed should meet the depth-to-length ratio D / L≤1 / 30; wherein D is the depth of the recess between two adjacent convex surfaces of the base surface; L is the distance between two adjacent convex surfaces of the base surface, and L is not greater than 1m.

[0023] Among them, in step (2), preferably, the thermal insulation and shock-absorbing layer on the initial support of the invert arch includes a seismic isolation support and a thermal insulation board; the seismic isolation support is a composite seismic isolation support made of rubber and stiffened steel plate; the thermal insulation board is a polyurethane foam board; the preferred materials of the seismic isolation support and the thermal insulation board have better seismic resistance and better thermal insulation effect.

[0024] Preferably, the isolation bearing has a size of 500×300×64 mm (length×width×height), and is evenly laid in a dotted form on the inner surface of the initial support of the invert, and the center distance between each isolation bearing is 1.2×1.0 m (circumferential×longitudinal).

[0025] Wherein, the thermal insulation board is used to fill the gap between the seismic isolation bearings.

[0026] Among them, in step (2), preferably, the thermal insulation and shock-absorbing layer on the initial support of the arch wall is a rubber isolation pad.

[0027] Preferably, one side of the rubber isolation pad is located in the direction of the initial support, the raised surface is located in the direction of the secondary lining, and is evenly fixed to the arch wall using M12 expansion bolts. Each isolation pad is arranged with 2 rows of expansion bolts along the longitudinal direction of the tunnel (with a longitudinal spacing of 300mm), and 5 rows of expansion bolts are arranged along the circumferential direction of the tunnel (with a circumferential spacing of 300mm). The spacing and number of expansion bolts can be adjusted appropriately according to the actual situation on site, and it is necessary to ensure that the isolation pad is close to the inner surface of the initial support. The installation gap between each rubber isolation pad is controlled at 5-10mm.

[0028] In step (2), the tunnel invert is cast in layers, with each construction length of 6 m.

[0029] Wherein, in step (3), the waterproof layer includes a waterproof roll and a waterproof board.

[0030] Preferably, the method for laying the waterproof layer is as follows: fixing the waterproof coiled material on the raised surface of the seismic isolation support, and fixing the waterproof board on the inner side of the waterproof coiled material.

[0031] Among them, preferably, the laying requirements of the waterproof layer are: the waterproof layer should be laid closely and flatly with the base layer, without wrinkles, collapses, and damage, to prevent the waterproof layer from expanding outward too much and squeezing into the groove of the seismic isolation pad when pouring the second lining concrete.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The repair method of the present invention can quickly and safely dismantle and replace damaged tunnel structures, thereby repairing tunnels with damaged structures.

[0034] 2. The repair method of the present invention uses segmented dismantling to replace vertical temporary supports through the setting of vertical steel sleeve arches, which is conducive to the segmented laying of the waterproof layer, ensures the waterproof effect of the tunnel invert, and ensures the safety and quality of the large-section tunnel invert lining concrete construction with vertical temporary supports.

[0035] 3. The repair method of the present invention has the advantages of being scientific and reasonable, technically rigorous, highly targeted, having low construction costs and good social benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a construction flow chart in an embodiment of the present invention;

[0037] Figure 2 This is a schematic cross-sectional diagram of a tunnel structure according to an embodiment of the present invention;

[0038] Figure 3 This is a schematic diagram of the cross-sectional structure of the upper step and the lower step according to an embodiment of the present invention;

[0039] Figure 4 This is a schematic diagram of laying the thermal insulation and shock absorbing layers of the upper and lower steps according to an embodiment of the present invention;

[0040] Figure 5 It is a schematic cross-sectional diagram of an upper step and a lower step according to an embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of laying the heat-insulating and shock-absorbing layer of the inverted arch according to an embodiment of the present invention;

[0042] Figure 7 This is a schematic cross-sectional view of an inverted arch according to an embodiment of the present invention;

[0043] Figure 8 The following are photos of on-site construction of an embodiment of the present invention.

[0044] Figure numerals: 1-initial support; 2-waterproof layer; 3-thermal insulation and shock-absorbing layer; 301-thermal insulation board; 302-vibration isolation support; 303-installation gap; 304-expansion bolt; 305-rubber seismic isolation pad; 4-secondary lining; 5-inverted arch; 6-steel sleeve arch. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with test examples and specific implementation methods. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following embodiments, and all technologies realized based on the content of the present invention belong to the scope of the present invention.

[0046] Example:

[0047] 1. Tunnel information and damage extent:

[0048] The exit of Daliang Tunnel is located at the F5 fault. The whole section of the tunnel is equipped with I20a steel frame, with a spacing of 1 frame / 0.8m. The secondary lining adopts double-layer lining. The first layer of lining adopts C30 cast-in-place concrete with a thickness of 30cm. The arch wall is equipped with grid steel frame with a spacing of 1 frame / 0.5m. The second layer of lining adopts C35 reinforced concrete, the arch wall is 40cm thick, and the invert arch is 60cm thick.

[0049] On January 8, 2022, a magnitude 6.9 earthquake occurred in Menyuan, with a focal depth of 10km and continuous aftershocks. The earthquake's seismogenic fault was the Lenglongling Fault (F5) in the middle and western section of the Qilian-Haiyuan Fault on the northeastern edge of the Qinghai-Tibet Plateau, which has a left-lateral strike-slip nature. The main surface crack formed by the earthquake passes through the upper mountain of the Daliang Tunnel exit. The surface cracks extend nearly east-west and are divided into two north-south cracks. According to the investigation, the crack on the north side is about 21.5km long, with a maximum displacement of about 3.1m; the crack on the south side is about 3.8km long, with a maximum displacement of about 0.5m. The maximum displacement at the invert uplift of the Daliang Tunnel exit section is about 2.0m, and the maximum displacement at the severe deformation is about 2m. The roadbed at the tunnel entrance (350m) is severely uplifted, with an uplift of about 20 to 70cm. It is completely damaged, with serious damage at the fault position. The lining is circumferentially squeezed and damaged, the waterproof layer is exposed, the arch has fallen off in a large area, a large number of steel bars are deformed and broken and leaked, and the electrical equipment on the arch is damaged. The tunnel is circumferentially dislocated at the fault, with a large mileage side shifted to the west by about 1.5 to 1.8m. The cracks between the linings are about 30 to 80cm wide and the structure is damaged.

[0050] 2. Specific repair method ( Figure 1 ):

[0051] (1) Install a steel arch on the inner side of the tunnel arch wall structure damaged by earthquake. Figure 2), using H175 steel, longitudinal spacing of 0.6m, the arch foot is set at the arch line of the tunnel cross section, the bottom of the steel arch uses 32c channel steel as the bottom longitudinal support beam, the longitudinal segment length of the steel arch is 6m, the segment length of the bottom channel steel support beam is 12m, after the segmented construction and grouting reinforcement of the tunnel surrounding rock, the steel arch is moved to enter the lower cycle reinforcement.

[0052] (2) After the steel-cased arches are reinforced in sections, the cross-sectional characteristics of the tunnel distortion and deformation caused by earthquake damage to the tunnel structure are measured and determined to determine the depth of asymmetric grouting reinforcement. The grouting range should ensure that there is at least a 3m reinforcement area around the expansion. The length of a single small duct is 0.5m shorter than the grouting range, and the spacing between small ducts is 2m*2m. The grouting material is sulphoaluminate cement, and the grouting pressure is controlled within 1.5MPa.

[0053] (3) After the radial grouting reinforcement of the tunnel, the lining structure is grooved, divided into three layers of excavation: upper step, lower step, and invert, and the secondary lining structure of the advanced tunnel is temporarily reinforced ( Figure 3 ) The demolition construction length is greater than 20m. After 3m of slotting in the replacement area, the formwork concrete and initial support removal and excavation are carried out simultaneously. Mechanical demolition is adopted in conjunction with loosening blasting and hydraulic shears to cut the steel bars. Initial support construction is carried out immediately after demolition and excavation. The maximum height after excavation of the upper step is about 8.2m, the lower step is 4.3m, and the invert excavation is 4.1m. After 3m of slotting on the replacement surface, the length of each replacement of the initial support of the upper step is not more than 2m. After 21m of replacement of the upper step, the replacement and excavation of the initial support of the lower step will begin, and the length of each replacement will not exceed 2m. After 24m of initial support construction of the lower step, the removal of the invert and expansion of the initial support will begin.

[0054] (4) After the initial support of the tunnel invert is completed, the base surface is cleaned and rubber isolation bearings are distributed in a dotted manner ( Figure 6 The vibration isolation material at the bottom of the tunnel invert is made of rubber isolation bearings and polyurethane foam boards ( Figure 7 ), the seismic isolation bearing is a composite material composed of rubber and stiffening steel plate, with a size of 500×300×64mm (length×width×height), and is evenly laid on the inner surface of the initial support of the arch in a dotted form. The center distance of each seismic isolation bearing is adjusted from the original design of 0.6×1.0m (circular×longitudinal) to 1.2×1.0m (circular×longitudinal). The tunnel arch wall adopts seismic isolation measures with full rubber seismic isolation pads ( Figure 4 ), the seismic isolation layer is located inside the initial support structure and outside the waterproof layer. Before laying, the exposed steel bar heads and other protrusions on the initial support base surface are cut off and water is sprinkled to soak. One side of the rubber seismic isolation pad is located in the direction of the initial support, and the raised surface is located in the direction of the second lining. It is evenly fixed to the arch wall with M12 expansion bolts ( Figure 5), each isolation pad is equipped with 2 rows of expansion bolts along the longitudinal direction of the tunnel (with a longitudinal spacing of 300mm), and 5 rows of expansion bolts are arranged along the circumferential direction of the tunnel (with a circumferential spacing of 300mm) to ensure that the isolation pad is close to the inner surface of the initial support. The circumferential blind pipe is fixed and the waterproof membrane is constructed according to the design documents and specifications to prevent the waterproof layer from expanding too much and squeezing into the groove of the isolation pad when pouring the secondary lining concrete.

[0055] (5) The secondary lining of the tunnel is constructed using a lining trolley, with each construction length of 6.2m.

Claims

1. A method for repairing a tunnel structure after an earthquake, characterized in that: The following steps are involved: Step 1: Find the damaged part of the tunnel structure and construct a circular steel arch at the damaged part of the tunnel structure; Step 2: Under the support of the annular steel sleeve arch, radially drill holes and inject grouting to reinforce the surrounding rock of the tunnel from the steps on the tunnel arch wall; then, remove the secondary lining and initial support of the steps on the tunnel arch wall one by one, and expand the excavation while removing the initial support. After the expansion is completed, re-apply the initial support of the tunnel; after the upper step of the arch wall is removed and the initial support length is reconstructed to be not less than 21m, radially inject grouting to reinforce the surrounding rock on both sides of the lower step of the tunnel arch wall. After reinforcement, remove the lining and initial support of the lower step of the tunnel arch wall one by one, and remove the initial support. Excavation can be carried out while supporting, and the initial support of the tunnel can be re-applied after the excavation is completed; after the initial support reconstruction length of the step under the arch wall is not less than 24m, radial grouting is used to reinforce the outer soil layer of the tunnel invert, and the original filling layer, invert and initial support structure of the tunnel are removed section by section. Excavation can be carried out while removing the initial support, and the initial support of the tunnel can be re-applied after the excavation is completed. After the initial support length of the invert is not less than 6m, the invert thermal insulation and shock-absorbing layer is first laid on the initial support of the invert, and then the tunnel invert and filling layer are re-applied; Step 3: After the reconstruction length of the invert and filling layer is not less than 24m, assemble the tunnel arch wall secondary lining trolley, first lay the thermal insulation and shock absorption layer and waterproof board on the initial support of the arch wall, and then reconstruct the tunnel arch wall secondary lining concrete; Step 4: Move the annular steel arch to the next location where the tunnel structure is damaged, and repeat steps 2-4 until all damaged locations of the tunnel structure are repaired.

2. The repair method according to claim 1, characterized in that: In step 1, the longitudinal spacing of the arch wall of the steel arch is 0.6m; fixed steel bars are fixed at the joints of the steel frame; longitudinal channel steels are arranged on both sides of the bottom of the steel frame; the steel frames are connected longitudinally by longitudinal welding of steel sections, with a circumferential spacing of 1.2m.

3. The repair method according to claim 1, characterized in that: In step 2, the depth of asymmetric grouting reinforcement is determined according to the characteristics of the twisted and deformed section of the tunnel, and the grouting range is at least guaranteed to have a 3m reinforcement area around it after the expansion.

4. The repair method according to claim 1, characterized in that: In step 2, the standard for ending grouting of a single hole in the grouting reinforcement is: when the designed final pressure is reached and grouting is continued for more than 10 minutes, the grouting volume of a single hole is less than 20L / min.

5. The repair method according to claim 1, characterized in that: In step 2, in the grouting reinforcement, sulphoaluminate cement is used as the grouting material, the grouting pressure is not greater than 1.5 MPa, and the grouting adopts skip-hole interval grouting to implement compaction type grouting.

6. The repair method according to claim 1, characterized in that: In step 2, when repairing the upper step, lower step and invert, first demolish the secondary lining structure or invert structure with a length greater than 20m, then open a 3m wide trench in the replacement area, and then demolish and expand the initial support. After the expansion is completed, apply new initial support.

7. The repair method according to claim 1, characterized in that: In step 2, the length of each repair of the initial support of the upper step is not more than 2m; after 21m of the upper step is dismantled and replaced, the repair of the lower step begins, and the length of each repair of the initial support of the lower step is not more than 2m, and the initial support construction is carried out immediately after each demolition and expansion; after 24m of the initial support construction of the lower step, the demolition of the invert begins, and the length of each repair of the initial support of the invert is 3m, and the initial support construction is carried out immediately after each demolition and expansion.

8. The repair method according to claim 1, characterized in that: In step 2, the flatness of the new initial support after the repair is completed should meet the depth-to-length ratio D / L≤1 / 30.

9. The repair method according to claim 1, characterized in that: In step 2, the thermal insulation and shock absorption layer on the initial support of the invert arch includes a seismic isolation support and a thermal insulation board; in step 3, the thermal insulation and shock absorption layer on the initial support of the upper step and the lower step is a rubber seismic isolation pad.

10. The repair method according to claim 1, characterized in that: In step 3, the waterproof layer includes a waterproof membrane and a waterproof board.

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