Grouting method for railway tunnel crossing goaf

Abstract

The invention relates to the technical field of reinforcement of a railway tunnel passing through a goaf, in particular to a grouting method for the railway tunnel passing through the goaf, which comprises the following steps of: drilling grouting drill holes which are symmetrical by taking a tunnel structure as a center from a ground line, and grouting to pre-reinforce a stratum; after grouting drill holes are drilled to the position 1-3 m below a goaf of the upper layer and a goaf caving zone bottom plate, the goaf of the upper layer and the goaf caving zone are reinforced through grouting; a grouting drill hole is drilled downwards, and a stratum is pre-reinforced through grouting; grouting to reinforce the lower-layer goaf and the goaf caving zone after the lower-layer goaf and the goaf caving zone are 1-3 m below the bottom plate; secondary grouting is conducted on the stratum within the excavation disturbance range of the tunnel structure cavern; and sealing the grouting drill hole. According to the method, layered grouting is conducted on the multi-layer goaf slump zone penetrated by the railway tunnel in a targeted mode, the unconsolidated bed is pre-reinforced, the problems of drilling hole collapse and drilling tool jamming are solved, the number of protective walls or steel protective cylinders is reduced, and the good reinforcing effect and economic benefits are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of reinforcement for railway tunnels passing through goaf areas, and particularly relates to a grouting method for railway tunnels passing through goaf areas. Background Art

[0002] During the construction of railway tunnel projects, passing through goaf areas is a complex and challenging technical problem. The geological conditions of goaf areas and their caving zones are complex, the strata are loose, and there are risks such as hole collapse, drill sticking, and drill burying, which bring great difficulties to drilling construction. Traditionally, the grouting reinforcement method for railway tunnels passing through goaf areas usually uses a single upward or downward grouting method, that is, after the drilling is formed, grout is injected into the goaf area and the caving zone through the grouting pipe until the grouting termination condition is reached. However, this method has many limitations.

[0003] Firstly, the traditional method lacks pertinence during the grouting process and cannot accurately grout and reinforce specific strata. Due to the complex geological conditions of goaf areas and their caving zones, the strata at different depths have different physical and mechanical properties. Therefore, a single grouting method often fails to meet the reinforcement requirements of all strata. This results in unsatisfactory grouting effects, and often requires remedial secondary grouting, increasing the construction cost and duration.

[0004] Secondly, during the drilling construction of the traditional method, if risks such as hole collapse occur, steel casing is usually used for protection. However, the use of steel casing not only increases the material cost but also prolongs the construction period. In addition, in deep drilling, if drill sticking or drill burying occurs and the drill cannot be retrieved, only the hole can be abandoned and redrilled, further increasing the construction difficulty and cost.

[0005] Furthermore, the traditional method also has deficiencies in the inspection of grouting effects. Usually, a comprehensive inspection is carried out after the grouting is completed. If the requirements are not met, remedial secondary grouting is carried out. This method cannot timely detect problems during the grouting process, nor can it monitor and adjust the grouting effects in real time.

[0006] Finally, the traditional method also has defects in the reinforcement of strata within the disturbance range of tunnel excavation. After the goaf area is reinforced, small duct grouting and bolt pre-reinforcement and other measures are usually required in the tunnel to ensure the stability of the chamber during tunnel structure excavation. However, these measures often require additional construction time and cost, and cannot be combined with the goaf area reinforcement process, resulting in low overall construction efficiency.

[0007] In view of the above problems, the present invention provides a grouting method for railway tunnels passing through goaf areas. Summary of the Invention

[0008] To solve the above problems, the present invention provides a grouting method for a railway tunnel passing through a mined-out area. This grouting method for a railway tunnel passing through a mined-out area uses the combined use of a grouting pipe and a grout stop valve in a borehole, and specifically grouts the caving zones of the mined-out areas in multiple layers through which the railway tunnel passes in a layered manner. By comprehensively using the down-the-hole method and the up-the-hole method, different grouting treatments are carried out for the original formation, the mined-out area, and the caving zone. This not only pre-reinforces the loose layer, eliminates the problems of borehole collapse and sticking of the drill bit, but also saves the quantity of retaining walls or steel casing pipes, achieving good reinforcement effects and economic benefits.

[0009] The technical solution of the present invention is as follows:

[0010] A grouting method for a railway tunnel passing through a mined-out area, comprising the following steps:

[0011] S1: Drill grouting boreholes symmetrically centered on the tunnel structure from the ground line and grout to pre-reinforce the formation;

[0012] S2: After drilling the grouting borehole to 1 - 3 m below the floor of the mined-out area and the caving zone of the upper layer, grout to reinforce the mined-out area and the caving zone of the upper layer;

[0013] S3: Drill the grouting borehole downward and grout to pre-reinforce the formation;

[0014] S4: After reaching 1 - 3 m below the floor of the mined-out area and the caving zone of the lower layer, grout to reinforce the mined-out area and the caving zone of the lower layer;

[0015] S5: Conduct secondary grouting on the formation within the excavation disturbance range of the tunnel structure chamber;

[0016] S6: Seal the grouting borehole;

[0017] Through a series of step-by-step grouting operations, comprehensive and layered grouting reinforcement is carried out on the formation of the railway tunnel passing through the mined-out area. First, pre-reinforce the formation, then grout and reinforce the mined-out areas and caving zones of the upper and lower layers respectively, and finally conduct secondary grouting and seal the borehole on the formation within the excavation disturbance range of the tunnel chamber, effectively improving the formation stability, ensuring the safety of the tunnel structure during the process of passing through the mined-out area, and reducing the construction risks.

[0018] In step S1 or S3, grouting reinforcement is carried out by the down-the-hole grouting method through the grouting pipe; the down-the-hole grouting method can pre-reinforce the formation, prevent problems such as borehole collapse and sticking of the drill bit during the drilling process, create good conditions for subsequent grouting and tunnel construction, save the use of temporary borehole protection measures (such as steel casing pipes), and reduce the cost and construction difficulty.

[0019] In step S2 or S4, a grouting pipe is placed in the grouting borehole, and two grout stop valves are installed on the grouting pipe. The two grout stop valves are respectively arranged at the upper and lower boundaries of the goaf and the caving zone of the upper or lower layer, and the upward grouting method is used for reinforcement; it can accurately control the grouting range, ensure that the grout fully fills the goaf and the caving zone, improve the grouting effect. At the same time, the two grouting boreholes are within the diffusion radius of the grouting pipe, verifying the grouting effect with each other to ensure the grouting quality.

[0020] The two grouting boreholes are within the diffusion radius of the grouting pipe; on the one hand, the grouting effect can be verified with each other. By comparing the grouting conditions of the two boreholes, problems in the grouting process can be detected in a timely manner, such as uneven grouting and insufficient grouting volume. On the other hand, this layout can expand the grouting reinforcement range, improve the overall effect of grouting reinforcement, and ensure that the goaf and the caving zone are fully reinforced.

[0021] When using the upward grouting method to reinforce the goaf and the caving zone of the upper layer, large-particle grouting is carried out first and then fine-particle grouting; large-particle grouting can fill larger pores and quickly improve the overall stability of the formation; fine-particle grouting further fills small pores, making the formation more dense, improving the strength and impermeability of the formation, and ensuring that the goaf and the caving zone are effectively reinforced.

[0022] When using the upward grouting method to reinforce the goaf and the caving zone of the lower layer, large-particle grouting is carried out first and then fine-particle grouting, and then high-pressure splitting grouting with fly ash slurry is adopted; the functions of large-particle and fine-particle grouting are the same as those of the upper layer. High-pressure splitting grouting with fly ash slurry can use high pressure to inject the slurry into the microfractures of the formation, further expanding the grouting reinforcement range, improving the density and strength of the formation, enhancing the overall stability of the formation, and effectively preventing the goaf and the caving zone of the lower layer from affecting the tunnel construction.

[0023] After the grouting of each layer of the goaf and the caving zone is completed, water injection detection is carried out; it can timely detect the parts with poor grouting effect so as to take targeted remedial measures. This "grouting and detecting simultaneously" method is more targeted than detecting once after all grouting is completed, which can avoid the situation that some defective parts cannot be effectively treated due to untimely detection and ensure the grouting reinforcement quality.

[0024] In step S5, the grouting pipe is lifted to the lower limit depth affected during the construction of the tunnel structure excavation chamber, and grout stop valves are positioned and installed through the grouting pipe at the upper and lower limit parts, and high-pressure splitting grouting with fly ash slurry is carried out; it can focus on reinforcing the formation within the range disturbed by the tunnel excavation, improve the stability and cohesion of the formation, reduce the risk of collapse during tunnel construction, and ensure the safety of construction personnel.

[0025] After step S5 ends, the grouting effect is inspected in at least two ways. If the grouting reinforcement effect does not meet the requirements, secondary grouting is carried out to replenish the grout at the non-compliant parts until the inspection is qualified. Such double inspection and grout replenishment measures can ensure that the grouting reinforcement effect meets the design requirements, improve the stability and safety of the tunnel structure after passing through the goaf, and reduce the later maintenance cost.

[0026] In step S6, the grouting holes for the whole section are sealed with cement mortar, which can prevent water and other substances in the stratum from entering the tunnel structure through the holes, affecting the stability and safety of the tunnel. At the same time, the hole-sealing operation is simple and low-cost, which can effectively protect the grouting effect and ensure the long-term stable operation of the tunnel.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The grouting method for a railway tunnel passing through a goaf disclosed by the present invention has a remarkable stratum reinforcement effect: by drilling grouting holes symmetrically centered on the tunnel structure, grouting reinforcement is carried out respectively for the upper and lower goafs and the goaf collapse zones, and a grout stop valve is reasonably set in the grouting holes to accurately control the grouting range, ensuring that each goaf and collapse zone can be effectively reinforced, and improving the overall stability of the stratum. By comprehensively applying the downward grouting method and the upward grouting method, differential grouting is carried out for the original stratum, goaf and collapse zone. The downward grouting method can pre-reinforce the loose layer and eliminate the problems of borehole collapse and sticking during drilling. The upward grouting method can better overcome the influence of gravity, make the grout fully fill the pores of the goaf and collapse zone, and improve the grouting effect.

[0029] 2. The grouting method for a railway tunnel passing through a goaf disclosed by the present invention ensures construction safety: during the drilling process, the downward grouting method is used to pre-reinforce the stratum, effectively preventing the occurrence of borehole collapse. After the grouting reinforcement of each goaf and the goaf collapse zone is completed, secondary high-pressure splitting grouting is carried out on the stratum within the excavation disturbance range of the tunnel structure chamber to strengthen the stability of the stratum within the disturbance range.

[0030] 3. A grouting method for a railway tunnel passing through a mined - out area disclosed by the present invention. This grouting method for a railway tunnel passing through a mined - out area adopts a "detect while grouting" detection method. After grouting each layer of the mined - out area and the caving zone of the mined - out area is completed, water injection detection is carried out. This detection method is different from the general one - time detection after all grouting is completed. The detection location is clearer, and it can timely discover the parts with poor grouting effect and conduct targeted and timely remedies. After step S5 ends, the grouting effect is inspected through at least two methods, further ensuring the reliability of the grouting reinforcement effect. If the grouting reinforcement effect does not meet the requirements, secondary grouting is carried out to replenish the slurry in the non - compliant parts until the inspection is qualified, ensuring the formation stability of the railway tunnel passing through the mined - out area and providing guarantee for the long - term safe operation of the railway tunnel.

[0031] 4. A grouting method for a railway tunnel passing through a mined - out area disclosed by the present invention. This grouting method for a railway tunnel passing through a mined - out area has remarkable economic benefits: By combining the use of grouting pipes and grout - stop valves in the boreholes, targeted stratified grouting is carried out for the caving zones of the mined - out areas where the railway tunnel passes through multiple mined - out areas. By comprehensively using the down - ward method and the upward method, different grouting is carried out for the original formation, the mined - out area, and the caving zone. It not only pre - reinforces the loose layer, eliminates the problems of borehole collapse and sticking of the drill bit, but also saves the number of retaining walls or steel casing pipes. At the same time, considering the mined - out area reinforcement and the tunnel structure excavation comprehensively, from a higher unified level, the construction period is shortened, the construction safety risk is reduced, and the investment is saved. For example, compared with the traditional grouting reinforcement method, this method avoids the re - drilling of waste holes caused by borehole collapse and sticking of the drill bit and the extensive use of steel casing pipes, reduces the material cost and construction cost, and shortens the construction period. This grouting method can be applied to the treatment of mined - out areas, the grouting reinforcement of tunnels and other underground chambers passing through, underlying cavities, and loose layers, ensuring the grouting reinforcement effect, guaranteeing the stability and safety of the upper structure, shortening the construction period, and saving investment, and has broad prospects for popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a flowchart of a grouting method for a railway tunnel passing through a mined - out area according to an embodiment of the present invention;

[0033] Figure 2 is a schematic diagram of the grouting method for a railway tunnel passing through a mined - out area according to an embodiment of the present invention when grouting and reinforcing the mined - out area and the caving zone of the mined - out area in the upper layer;

[0034] Figure 3 is a schematic diagram of the grouting method for a railway tunnel passing through a mined - out area according to an embodiment of the present invention when grouting and reinforcing the mined - out area and the caving zone of the mined - out area in the lower layer;

[0035] Figure 4 is a schematic diagram of the grouting method for a railway tunnel passing through a mined - out area according to an embodiment of the present invention when grouting and reinforcing the influence range of the tunnel structure chamber excavation;

[0036] The components represented by the reference numerals in the figures are as follows:

[0037] In the present invention: 1. Ground line, 2. Grouting borehole, 3. Grouting pipe, 4. Goaf and caving zone of goaf, 5. Tunnel structure, 6. Grout stop valve. Specific embodiments

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings through specific embodiments. Similar elements in different embodiments are labeled with related similar reference numerals. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present application. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present application are not shown or described in the specification, which is to avoid the core part of the present application being overwhelmed by excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0039] In addition, the features, operations, or characteristics described in the specification can be combined in any appropriate manner to form various embodiments. At the same time, the steps or actions in the method description can also be reordered or adjusted in an obvious manner by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean that they are the necessary sequences, unless it is stated that a certain sequence must be followed.

[0040] As Figures 1 to 4 shown, the grouting method for a railway tunnel passing through a goaf includes the following steps:

[0041] S1: Drill grouting boreholes 2 symmetrically centered on the tunnel structure 5 from the ground line 1 and grout to pre-reinforce the formation;

[0042] S2: After drilling the grouting boreholes 2 to 1 - 3 m below the floor of the upper goaf and caving zone of goaf 4, grout to reinforce the upper goaf and caving zone of goaf 4;

[0043] S3: Drill the grouting boreholes 2 downward and grout to pre-reinforce the formation;

[0044] S4: After reaching 1 - 3 m below the floor of the lower goaf and caving zone of goaf 4, grout to reinforce the lower goaf and caving zone of goaf 4;

[0045] S5: Perform secondary grouting on the formation within the range of excavation disturbance of the tunnel structure 5 chamber;

[0046] S6: Seal the grouting borehole 2.

[0047] Embodiment

[0048] On the ground 1, boreholes 2 are drilled into the formation symmetrically through a drill rig. Downward self-flow grouting is carried out through the grouting pipe 3. When the borehole 2 enters 1 - 3 m below the bottom of the first upper goaf and the caving zone 4 of the goaf, the grouting pipe 3 is placed, and two grout stop valves 6 are installed in position through the positioning of the grouting pipe. After installation, the first upward grouting method is started through the grouting pipe 3. First, self-flow grouting of large particles is carried out, and then low-pressure grouting of large particles; to ensure the temporary stability of the first caving zone and prevent borehole collapse when drilling deeper, which may affect the borehole; the two boreholes 2 are symmetrically arranged and within the diffusion radius of the grouting pipe 3 to mutually verify the grouting effect (both a grouting hole and a verification hole); continue to adopt the downward grouting method to continue drilling to 1 - 3 m below the bottom of the second lower goaf and the caving zone 4 of the goaf. Stop valves 6 are installed above and below, and the second upward grouting method is started. First, self-flow grouting of large particles is carried out, and then low-pressure grouting of large particles; then fine-grained high-pressure splitting grouting is adopted. The two boreholes 2 are symmetrically arranged and within the diffusion radius of the grouting hole to mutually verify the grouting effect (both a grouting hole and a verification hole), and the simple water injection method is adopted to detect that the grouting effect reaches the reinforcement effect; then the grouting pipe 3 is lifted to the lower limit depth affected during the construction of the excavation chamber of the tunnel structure 5, and stop valves are installed in position through the positioning of the grouting pipe 3 at the upper and lower limit parts affected, and secondary high-pressure splitting grouting of fine-grained slurries such as cement fly ash is carried out at the key parts to ensure that there are no voids in the caving zone after grouting and there is sufficient cohesive force, which can ensure the stability of the surrounding rock during construction, and the simple water injection method is used to detect the grouting effect; finally, the grouting pipe 3 is lifted to the ground 1, and the entire section of the borehole 2 is sealed with cement mortar. After inspection and passing, the grouting is completed.

[0049] Through the combined use of the grouting hole 3 and the grout stop valve 6, the effective grouting part is accurately positioned, and targeted grouting reinforcement is carried out for the goaf and the caving zone 4 of the goaf at different depths to ensure the stability of the site, thus ensuring the stability and safety of the tunnel structure 5 during the operation period; when using the upward grouting method for the goaf and the caving zone 4 of the goaf, and the downward grouting method for the upper formation of the caving zone of the goaf and the formation between the two goafs and the caving zone 4 of the goaf, it has the function of pre-reinforcement to prevent borehole collapse and eliminate the hidden danger of drill jamming. At the same time, different from the general single grouting method, the effect is more targeted, and when using the upward grouting method for the goaf and the caving zone 4 of the goaf, gravity needs to be overcome, and the grouting effect is better.

[0050] After the two groutings of large particles and fine particles for each goaf and the caving zone 4 of the goaf are completed, the corresponding parts are detected by water injection at any time. Different from the general one-time detection after all groutings are completed. The detection parts are more definite, and timely remedial measures can be taken specifically when the effect is not good.

[0051] After the grouting reinforcement is completed in each goaf and the goaf caving zone 4, through the combined use of the grouting pipe 3 and the grout stop valve 6, fully considering the influence of the surrounding rock disturbance during the construction of the tunnel structure 5 itself, secondary high-pressure split grouting is carried out on the strata disturbed during the excavation of the tunnel structure 5 to enhance the stability of the strata within the disturbed range.

[0052] The grouting method for a railway tunnel passing through a goaf adopts the combined use of a grouting pipe and a grout stop valve in a borehole, and specifically grouts in layers in the goaf caving zone of the railway tunnel passing through multiple goafs. By comprehensively using the down-the-hole method and the up-the-hole method, different grouting is carried out for the original strata, goafs and caving zones. This not only pre-reinforces the loose layer, eliminates the problems of borehole collapse and sticking of the drill bit, but also saves the quantity of shaft lining or steel casing, achieving good reinforcement effects and economic benefits. This method adopts a "detect while grouting" detection method, solving the problem of unclear defective parts caused by a single detection after the grouting of multiple goafs is completed.

[0053] The grouting method for the railway tunnel passing through the goaf pre-reinforces the strata by adopting the down-the-hole grouting method from the ground 1. After drilling the grouting borehole 2 to 1 - 3 m below the bottom plate of the upper goaf and the goaf caving zone 4, the grouting and detection positions are defined through the grouting pipe 3 and the grout stop valve 6. The up-the-hole grouting method is adopted to complete the grouting reinforcement and pass the inspection by first grouting with large particles and then with fine particles. Then, the down-the-hole grouting method is continued to drill to 1 - 3 m below the bottom plate of the lower goaf and the goaf caving zone 4, and the up-the-hole grouting method is adopted to complete the grouting reinforcement and pass the inspection by first grouting with large particles and then with fine particles. Then, the same method is adopted to carry out secondary split grouting on the strata within the disturbed range of the tunnel structure 5 chamber excavation to ensure the stability of the surrounding rock of the tunnel chamber. Finally, the borehole is sealed to end the grouting, ultimately achieving the dual effects of grouting reinforcement and stable excavation of the tunnel structure.

[0054] In the grouting method, the grouting borehole 2 is drilled into a hole using a suitable drill rig and drilling method according to the strata. It is required that the opening diameter is not less than 130 mm and the final hole diameter is not less than 91 mm.

[0055] In the grouting method, the grouting pipe 3 is a device for realizing the grouting channel and positioning, and materials such as cast iron, perforated steel pipe, and high-strength composite materials can be used according to needs.

[0056] In the grouting method, the grout stop valve 6 is a facility for positioning and restricting the flow of the grout, and it needs to meet the requirements of easy adjustment and airtightness. Materials such as cast iron, alloy, and high-strength composite materials can be used according to needs, and it can also be reused.

[0057] The grouting pipe 3 and the grout stop valve 6 need to be used in combination for positioning and sealing the grout.

[0058] During construction:

[0059] 1. Conduct general exploration using more than two geophysical exploration methods such as seismic waves and electrical methods, and adopt a comprehensive exploration method of drilling verification to determine the specific depth and looseness degree of the underground mined - out area and the collapse range.

[0060] 2. After surface clearing and relocation, carry out site leveling and temporary intercepting and draining construction around the site, set up slurry ponds, install grouting equipment, and configure supporting grouting monitoring equipment, etc.

[0061] 3. Mark or groove the grouting holes according to the depth of the mined - out area and the caving zone shown in the exploration report and on - site drilling. Use a suitable drilling rig to drill holes, and grout and reinforce the loose strata while drilling to prevent hole collapse.

[0062] 4. Adopt the downward grouting method to drill from the ground to a certain depth below the bottom of the first - layer mined - out area and the caving zone of the mined - out area. Install grout - stopping valves at the top and bottom, and start the first upward grouting. First, self - flowing grouting (large particles) and then low - pressure grouting of large particles; ensure the temporary stability of the first - layer caving zone, and prevent hole collapse when drilling deeper, which may affect the drilling; arrange two drill holes symmetrically, and within the diffusion radius of the grouting hole, verify the grouting effect with each other (both are grouting holes and verification holes).

[0063] 5. Adopt the downward grouting method to continue drilling to a certain depth below the bottom of the second - layer mined - out area and the caving zone of the mined - out area. Install grout - stopping valves at the top and bottom, and start the second upward grouting. First, self - flowing grouting (large particles) and then low - pressure grouting of large particles; then adopt high - pressure split grouting with fly ash slurry (fine particles). Arrange two drill holes symmetrically, and within the diffusion radius of the grouting hole, verify the grouting effect with each other (both are grouting holes and verification holes), and adopt a simple water - injection method to detect the grouting effect.

[0064] 6. Lift the grouting holes to the lower limit depth affected during the construction of the tunnel structure excavation chamber, and install grout - stopping valves at the upper and lower limit parts, and conduct secondary high - pressure split grouting (fine - particle slurry such as cement and fly ash) at key parts to ensure that there are no voids in the caving zone after grouting and there is sufficient cohesive force, which can ensure the stability of the surrounding rock during construction. And adopt a simple water - injection method to detect the grouting effect.

[0065] 7. Lift the grouting pipes to the ground, and test the grouting effect of the field area through more than two geophysical exploration methods and core sampling, etc.

[0066] 8. If the grouting reinforcement effect does not meet the requirements, adopt secondary grouting to supplement grout for the non - compliant parts specifically and conduct water - injection inspection.

[0067] 9. Until the reinforcement effect is met, use cement mortar to seal the holes of the whole section of the drill holes, and the grouting ends.

[0068] 10. Layout deep - layer and surface monitoring points to form a long - term monitoring network, and conduct long - term deformation monitoring on the grouting reinforcement effect.

[0069] 11. Form inspection, grouting construction, detection and monitoring complete reports, summarize the grouting experience of corresponding strata and corresponding types of goafs, and guide the treatment of similar goafs in this area.

[0070] While ensuring the reinforcement effect of the goaf, this grouting method takes into account the risks during the excavation of the railway tunnel structure, pre-reinforces the strata within the range of tunnel excavation disturbance (secondary split grouting), reduces the risk of tunnel construction collapse, ensures personal safety, and reduces the number of temporary protections during excavation.

[0071] This grouting method is based on the overall consideration of goaf treatment and tunnel structure construction excavation when the railway tunnel passes through multiple goafs. It overcomes the defects of existing grouting methods that cannot perform targeted grouting, detect by parts, and comprehensively consider the temporary reinforcement during tunnel construction. Moreover, it combines the measures to ensure construction quality during construction with the measures for subsequent tunnel structure construction, saving investment and accelerating the construction progress.

[0072] This grouting method for the railway tunnel passing through the goaf adopts the comprehensive grouting method to perform targeted grouting and reinforcement on the loose strata (goaf and caving zone). By using grouting pipes and grout stop valves for positioning, gradually compact and strengthen the large pores, small pores and split grouting in a step-by-step manner. Considering the goaf reinforcement and tunnel structure excavation comprehensively, from a higher unified level, it shortens the construction period, reduces the construction safety risk, and saves investment; it can be applied to the treatment of goafs, the grouting reinforcement of tunnels and other underground chambers passing through, underlying cavities and loose strata, ensuring the grouting reinforcement effect, guaranteeing the stability and safety of the upper structure, shortening the construction period and saving investment, and has broad prospects for popularization and application.

[0073] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the embodiments of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0074] The above uses specific examples to elaborate on the present invention, which is only used to help understand the present invention and is not intended to limit the present invention. For those skilled in the technical field to which the present invention belongs, according to the idea of the present invention, several simple deductions, deformations or substitutions can also be made.

Claims

1. A grouting method for a railway tunnel passing through a goaf, characterized in that: The following steps are involved: S1: Drilling grouting holes (2) symmetrically centered around the tunnel structure (5) from the ground line (1) and injecting grout to pre-reinforce the ground; S2: After drilling a grouting borehole (2) to 1-3 m below the bottom plate of the goaf and the goaf collapse zone (4) of the upper layer, grouting is performed to reinforce the goaf and the goaf collapse zone (4) of the upper layer; S3: Drilling a grouting borehole (2) downward and injecting grouting to pre-reinforce the stratum; S4: After reaching 1-3 m below the bottom plate of the goaf and the goaf collapse zone (4) in the lower layer, grouting is performed to reinforce the goaf and the goaf collapse zone (4) in the lower layer; S5: performing secondary grouting on the strata within the disturbance range of the tunnel structure (5) cavern excavation; S6: Seal the grouting drill hole (2).

2. A grouting method for a railway tunnel passing through a goaf as claimed in claim 1, characterized in that: In step S1 or S3, grouting reinforcement is performed by adopting a downward grouting method through a grouting pipe (3).

3. A grouting method for a railway tunnel passing through a goaf as claimed in claim 1, characterized in that: In step S2 or S4, a grouting pipe (3) is placed in the grouting borehole (2), and two grouting stop valves (6) are installed on the grouting pipe (3). The two grouting stop valves (6) are respectively arranged at the upper and lower boundaries of the goaf area of ​​the upper or lower layer and the goaf collapse zone (4), and the upward grouting reinforcement is adopted.

4. A grouting method for a railway tunnel passing through a goaf as claimed in claim 3, characterized in that: The two grouting boreholes (2) are within the diffusion radius of the grouting pipe (3).

5. A grouting method for a railway tunnel passing through a goaf as claimed in claim 3, characterized in that: When the upper goaf and goaf collapse zone (4) are reinforced by upward grouting, large particles are injected first and then fine particles are injected.

6. A grouting method for a railway tunnel passing through a goaf as claimed in claim 3, characterized in that: When the goaf and the collapsed zone (4) of the goaf in the lower layer are reinforced by the upward grouting method, large particles are first grouted and then fine particles are grouted, and then fly ash slurry is used for high-pressure splitting grouting.

7. A grouting method for a railway tunnel passing through a goaf as claimed in claim 3, characterized in that: After the grouting of each layer of goaf and goaf collapse zone (4) is completed, water injection testing is carried out.

8. A grouting method for a railway tunnel passing through a goaf as claimed in claim 1, characterized in that: In step S5, the grouting pipe (3) is lifted to the lower limit depth affected by the excavation of the tunnel structure (5) during construction, and a stop valve (6) is positioned and installed through the grouting pipe (3) at the upper and lower limit positions affected, and high-pressure splitting grouting is performed using fly ash slurry.

9. A grouting method for a railway tunnel passing through a goaf as claimed in claim 1, characterized in that: After step S5 is completed, the grouting effect is tested in at least two ways. If the grouting reinforcement effect does not meet the requirements, secondary grouting is performed to fill the unsatisfactory parts until the test is qualified.

10. A grouting method for a railway tunnel passing through a goaf as claimed in claim 1, characterized in that: In step S6, cement mortar is used to seal the entire grouting borehole (2).

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