A construction method of a tunnel vault cave

Abstract

The present application relates to the construction technical field of tunnel construction processing broken surrounding rock, especially to a kind of construction method of tunnel vault karst cave, comprising the following steps: first, the face and the surface of karst cave are closed;From outside to inside in tunnel excavation end face, steel arch and construction advance pipe shed are successively erected;First grouting pipe and second grouting pipe are pre-buried at steel arch, and grouting process is completed by first grouting pipe and second grouting pipe in turn;Preferably, the material injected in first grouting pipe is foam concrete, and the material injected in second grouting pipe is cement slurry solution. Wherein, foam concrete and cement slurry solution not only can complete the backfilling of karst cave, but also the self-weight of foam concrete is lighter, which can effectively ensure the safety of tunnel supporting structure, after the consolidation of foam concrete, cement slurry solution is injected again, which can further fill the cavity gap, ensure the filling effect of karst cave, and effectively ensure the safety of tunnel supporting structure, with high popularization prospect.

Description

Technical Field

[0001] This invention relates to the field of construction technology for treating fractured surrounding rock in tunnel construction, and in particular to a construction method for a karst cave in the tunnel arch. Background Technology

[0002] The formation of karst caves is the result of long-term erosion by groundwater in limestone areas. Insoluble calcium carbonate in limestone can be converted into slightly soluble calcium bicarbonate by the action of water and carbon dioxide. This geological phenomenon affects the stability and mechanical distribution of the surrounding rock, impacting the quality of nearby engineering construction. Karst caves of a certain size and scale not only affect the structural stability of tunnels, endangering tunnel construction safety and progress, but can also cause tunnel uplifts and collapses due to improper handling, such as insufficient support and reinforcement, or blockage of karst water channels leading to excessive groundwater pressure, seriously affecting the operational safety of tunnels.

[0003] In tunnel construction, some construction techniques significantly impact the stress distribution of the surrounding rock. Encountering unavoidable karst caves increases the risk of structural instability and complicates construction processes. Among these, karst caves at the tunnel arch are a common adverse geological phenomenon, including fully filled, dry, and partially filled caves. Located at the tunnel arch, improper handling of these caves can pose significant safety hazards during both initial construction and subsequent operation.

[0004] Currently, the main method for dealing with karst caves in China is to backfill them with plain concrete. However, due to the large weight of concrete, when the karst cave is large, it can easily damage the original support system of the tunnel, posing a significant safety hazard.

[0005] To address the aforementioned problems, developing a novel construction method for tunnel arch karst caves is a technical issue that urgently needs to be resolved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide a construction method for a karst cave in the tunnel arch. This construction method can effectively ensure the safety of the tunnel support structure and has high potential for widespread application.

[0007] This invention provides a construction method for a karst cave in the arch of a tunnel, comprising the following steps:

[0008] S1. First, seal the working face and the surface of the cave.

[0009] S2. Steel arch frames and construction advance pipe sheds are erected sequentially from the outside to the inside at the tunnel excavation end face;

[0010] S3. Pre-embed the first grouting pipe and the second grouting pipe at the steel arch frame, and complete the grouting process in sequence through the first grouting pipe and the second grouting pipe;

[0011] Preferably, the material injected into the first grouting pipe is foamed concrete, and the material injected into the second grouting pipe is cement slurry.

[0012] The construction method of this invention mainly includes the following steps: First, the tunnel face and the surface of the karst cave are sealed to prevent the surface of the karst cave from collapsing and affecting subsequent construction; then, steel arch frames and construction advance pipe roofs are erected sequentially from the outside to the inside of the tunnel excavation end face to provide stable and effective support for the subsequent filling and grouting of the karst cave, ensuring the stability of the excavation face; finally, foamed concrete and cement grout are injected into the karst cave through the first and second grouting pipes pre-embedded at the steel arch frames. The foamed concrete and cement grout can not only completely backfill the karst cave, but the foamed concrete is also lightweight, which can effectively ensure the safety of the tunnel support structure. After the foamed concrete has solidified, cement grout is injected to further fill the cavity voids and ensure the filling effect of the karst cave.

[0013] As a preferred embodiment of this technical solution, in step S1, when sealing the working face and the surface of the karst cave, shotcrete is used. On the one hand, this can effectively prevent the surface of the karst cave from falling off, and on the other hand, it can effectively ensure the initial strength between the karst cave and the working face and the concrete, thereby ensuring the smooth progress of subsequent construction.

[0014] As a preferred embodiment of this technical solution, in step S2, the pre-construction pipe shed includes multiple steel pipes arranged along the longitudinal direction of the tunnel, and the steel pipes are arranged circumferentially along the tunnel surface; preferably, the spacing of the circumferentially arranged steel pipes is 400-500mm.

[0015] In actual construction, depending on the condition of the surrounding rock, steel pipes of different lengths and diameters can be selected for the construction of the advanced pipe roof. Specifically, the steel pipes are laid out circumferentially along the tunnel face, and the spacing between the circumferentially laid steel pipes is any value between 400-500mm.

[0016] As a preferred embodiment of this technical solution, after the steel pipes are laid out, cement grout is injected into the steel pipes.

[0017] To further improve the support strength of the pre-construction pipe shed, cement grout can be injected into the steel pipe, which not only solves the problem of poor steel pipe strength, but also ensures the safety of the tunnel support structure.

[0018] As a preferred embodiment of this technical solution, the cement slurry contains 4-6% water glass by weight of cement, and the water-cement ratio in the cement slurry is 1:(0.8-1.2); preferably, the concentration of the water glass is 30-40 Baume degrees, and the modulus of the water glass is 2-3; preferably, grouting is considered complete when the grouting pressure is 0.5-1.0 MPa.

[0019] As a preferred embodiment of this technical solution, step S3 specifically includes: using a ground pump and pumping pipeline, injecting foamed concrete into the collapsed cavity above the arch through the reserved first grouting pipe, and after solidification, injecting cement slurry through the second grouting pipe to fill the cavity gaps.

[0020] As a preferred embodiment of this technical solution, the length of the second grouting pipe is greater than that of the first grouting pipe, and the end of the second grouting pipe extends to the uppermost part of the karst cave.

[0021] In this invention, the second grouting pipe is used not only to fill the cavity gaps and solve the problem of incomplete filling in some areas, but also to serve as an observation pipe to check whether the grouting is complete. Specifically, the end of the second grouting pipe is extended to the uppermost end of the karst cave. When the karst cave is completely grouted, the excess cement grout will overflow from the end of the second grouting pipe. Therefore, when grout overflows from the second grouting pipe, it indicates that the gaps in the karst cave have been completely filled.

[0022] As a preferred embodiment of this technical solution, a collection trough is detachably provided at the end of the second grouting pipe away from the karst cave.

[0023] In addition, a collection tank is provided at the end of the second grouting pipe away from the karst cave, which can collect the grout overflowing from the second grouting pipe.

[0024] As a preferred embodiment of this technical solution, the dry density of the foamed concrete is 200-500 kg / m³. 3 .

[0025] Based on actual construction requirements, the dry density of the foamed concrete used in this invention is 200-500 kg / m³. 3 Any value between these ranges. Specifically, the foamed concrete preparation method of this invention is as follows: First, according to the mix proportions and production process, foamed slurry is prepared; then, according to the designed foamed concrete model, a certain amount of water is added to the mixer, and then the prepared cement is added to the mixer for mixing; finally, the pre-made foam is added to the cement slurry and stirred until the slurry is homogeneous and non-viscous, at which point it can be poured or pumped on-site. The prepared foamed concrete should be used immediately, and slurry prepared the next day should not be used the following day.

[0026] As a preferred embodiment of this technical solution, the strength of the sprayed concrete is C15-C30.

[0027] Depending on the initial strength requirements of the working face and karst caves, shotcrete with strengths of C15, C20, C25, or C30 can be selected.

[0028] The construction method for the tunnel arch karst cave of the present invention has at least the following technical effects:

[0029] In the construction method of the tunnel arch karst cave of the present invention, firstly, the tunnel face and the surface of the karst cave are sealed to prevent the surface of the karst cave from collapsing and affecting subsequent construction. Then, steel arch frames and construction advance pipe roofs are erected sequentially from the outside to the inside of the tunnel excavation end face to provide stable and effective support for the subsequent filling and grouting of the karst cave, ensuring the stability of the excavation face. Finally, foamed concrete and cement grout are injected into the karst cave through the first and second grouting pipes pre-embedded at the steel arch frames. The foamed concrete and cement grout can not only completely backfill the karst cave, but the lightweight foamed concrete can also effectively ensure the safety of the tunnel support structure. After the foamed concrete has solidified, cement grout is injected to further fill the cavity voids, ensuring the filling effect of the karst cave. The karst cave filling method of the present invention has low construction risk, requires no special mechanical equipment, allows for rapid response and handling on site, and can effectively ensure the safety of the tunnel support structure, thus having high prospects for promotion. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a cross-sectional layout diagram of the karst cave treatment method according to the present invention;

[0032] Figure 2 This is a longitudinal section layout diagram of the karst cave treatment method of the present invention.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1: Steel arch frame; 2: Construction advance pipe shed; 3: First grouting pipe; 4: Second grouting pipe; 5: Ground pump; 6: Pumping pipeline. Detailed Implementation

[0035] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0037] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly; for example, they may refer to a fixed connection, a detachable connection, or an integral connection; they may refer to a mechanical connection or an electrical connection; they may refer to a direct connection or an indirect connection through an intermediate medium; and they may refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Example 1

[0039] S11. During the excavation process, a karst cave was found in the arch. First, C20 shotcrete was used to seal the working face and the surface of the karst cave to prevent the surface of the karst cave from falling off.

[0040] S12. After the closure construction is completed, steel arch frame 1 and construction advance pipe shed 2 are erected on the excavation section to share the load of foamed concrete injected into the cavity above. Cement slurry is injected into the pipe of construction advance pipe shed 2. The cement slurry contains 4% water glass by weight of cement, the water-cement ratio is 1:0.8, the concentration of water glass is 30 Baume degrees, and the modulus is 2.

[0041] S13. A first grouting pipe 3 and a second grouting pipe 4 are pre-embedded at the steel arch frame 1. Using a ground pump 5 and a pumping pipeline 6, foamed concrete is injected into the collapsed cavity above the arch crown along the pre-embedded first grouting pipe 3. The dry density of the foamed concrete is 300 kg / m³. 3After solidification, cement grout is injected through the second grouting pipe 4. The parameters of the cement grout are the same as those used for steel pipe grouting to fill the cavity voids and complete the treatment of all tunnel karst caves. After construction, the overall stability of the tunnel is good, with no water seepage or large deformation of the lining, indicating that the karst cave treatment measures were appropriate.

[0042] Example 2

[0043] S21. During the excavation process, a karst cave was found in the arch. First, C25 shotcrete was used to seal the working face and the surface of the karst cave to prevent the surface of the karst cave from falling off.

[0044] S22. After the closure construction is completed, steel arch frame 1 and construction advance pipe shed 2 are erected on the excavation section to share the load of foamed concrete injected into the cavity above. Cement grout is injected into the pipe of construction advance pipe shed 2. The cement grout contains 5% water glass by weight of cement, the water-cement ratio is 1:1, and the concentration of water glass is 35 Baume degrees and the modulus is 2.

[0045] S23. A first grouting pipe 3 and a second grouting pipe 4 are pre-embedded at the steel arch frame 1. Using a ground pump 5 and a pumping pipeline 6, foamed concrete is injected into the collapsed cavity above the arch crown along the pre-embedded first grouting pipe 3. The dry density grade of the foamed concrete is 200 kg / m³. 3 After solidification, cement grout is injected through the second grouting pipe 4. The parameters of the cement grout are the same as those used for steel pipe grouting to fill the cavity voids and complete the treatment of all tunnel karst caves. After construction, the overall stability of the tunnel is good, with no water seepage or large deformation of the lining, indicating that the karst cave treatment measures were appropriate.

[0046] Example 3

[0047] S31. During the excavation process, a karst cave was found in the arch. First, C30 shotcrete was used to seal the working face and the surface of the karst cave to prevent the surface of the karst cave from falling off.

[0048] S32. After the closure construction is completed, steel arch frame 1 and construction advance pipe shed 2 are erected on the excavation section to share the load of foamed concrete injected into the cavity above. Cement grout is injected into the pipe of construction advance pipe shed 2. The cement grout contains 6% water glass by weight of cement, the water-cement ratio is 1:1.2, the concentration of water glass is 40 Baume degrees, and the modulus is 3.

[0049] S33. A first grouting pipe 3 and a second grouting pipe 4 are pre-embedded at the steel arch frame 1. Using a ground pump 5 and a pumping pipeline 6, foamed concrete is injected into the collapsed cavity above the arch crown along the pre-embedded first grouting pipe 3. The dry density of the foamed concrete is 300 kg / m³. 3After solidification, cement grout is injected through the second grouting pipe 4. The parameters of the cement grout are the same as those used for steel pipe grouting to fill the cavity voids and complete the treatment of all tunnel karst caves. After construction, the overall stability of the tunnel is good, with no water seepage or large deformation of the lining, indicating that the karst cave treatment measures were appropriate.

[0050] In summary, the karst cave filling method of the present invention has low construction risk, requires no special mechanical equipment, enables rapid response and handling on site, and can effectively ensure the safety of tunnel support structures, thus having high prospects for promotion.

[0051] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method of constructing a tunnel-vault cavern, characterized by, The method comprises the following steps: S1, first, the tunnel face and the cave surface are closed; S2, a steel arch (1) and a construction advanced pipe shed (2) are erected in turn from the outside to the inside of the tunnel excavation end face; S3, a first grouting pipe (3) and a second grouting pipe (4) are pre-buried at the steel arch (1), and the grouting process is completed in turn through the first grouting pipe (3) and the second grouting pipe (4); The material injected into the first grouting pipe (3) is foamed concrete, and the material injected into the second grouting pipe (4) is cement slurry; In step S1, when the tunnel face and the cave surface are closed, sprayed concrete is used; In step S2, the construction advanced pipe shed (2) comprises a plurality of steel pipes arranged along the longitudinal direction of the tunnel, and the steel pipes are arranged in a ring around the tunnel face; The spacing of the ring arrangement of the steel pipes is 400-500mm; After the steel pipes are arranged, cement slurry is injected into the steel pipes; The water glass added in the cement slurry accounts for 4-6% of the weight of the cement, and the water-cement ratio in the cement slurry is 1:(0.8-1.2); The concentration of the water glass is 30-40 Baume, and the modulus of the water glass is 2-3; The completion of grouting is determined by the grouting pressure of 0.5-1.0MPa; Step S3 specifically comprises: using a ground pump (5) and a pumping pipeline (6) to inject foamed concrete into the cavity above the collapsed dome along the first grouting pipe (3), and after solidification, injecting cement slurry through the second grouting pipe (4) to fill the cavity gap; The length of the second grouting pipe (4) is greater than that of the first grouting pipe (3), and the end of the second grouting pipe (4) extends to the uppermost end of the cave; The end of the second grouting pipe (4) away from the cave is detachably provided with a collecting groove; The dry density level of the foam concrete is 200-500 kg / m 3 ; The strength of the sprayed concrete is C15-C30.

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