A surrounding rock pre-reinforcement construction method suitable for large-span expansion tunnels

Abstract

The present invention provides a surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel, comprising the following steps: S1, after determining the grouting reinforcement range, according to a first preset spacing and a second preset spacing, a first radial grouting pipe is arranged at equal intervals along the axial direction and radial direction of the original tunnel, and cement-water-glass double liquid slurry and cement slurry are successively injected to form a slurry stop wall; S2, according to a third preset spacing, along the radial direction of the original tunnel, a second radial grouting pipe is arranged at equal intervals between two first radial grouting pipes and cement slurry is injected; S3, at the heading face, according to the designed initial support structure contour, an advance pipe shed is set for the loose layer and grouting is performed; S4, an advance small guide tube is set for the loose layer along the advance pipe shed contour and cement slurry is injected; S5, the surrounding rock reinforcement effect is detected by a hole inspection method or an acoustic wave detection method; compared with the prior art, the surrounding rock pre-reinforcement construction method provided by the present invention can improve the reinforcement effect and stability of the surrounding rock, and enhance the self-stabilizing arching ability of the surrounding rock.

Description

Technical Field

[0001] The present invention relates to the technical field of civil engineering, and in particular to a surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel in a poor geological section, which improves the grouting reinforcement effect on the surrounding rock, can better enhance the self-stabilizing arching ability of the surrounding rock around the expansion tunnel, and greatly reduces the possibility of landslide accidents during the tunnel expansion construction process. Background Art

[0002] In order to meet the traffic demand, some old tunnels need to be expanded. The surrounding rock conditions encountered in the expansion of old tunnels are more complicated than those of new tunnels. During the construction of old tunnels, due to the limited technological level at that time, the arch of the old tunnel structure was over-excavated, and usually after the completion of the secondary lining construction, soil, stone and other materials were used to backfill, and the backfill was not dense enough. At the same time, during the excavation and operation of the original tunnel, the rocks around the original tunnel continued to loosen, and the range of the rock loosening circle continued to expand. The rocks and the loose backfill together formed a large outer wall of the original tunnel. The loose strata within a certain range contain a large number of pores and channels. When grouting is performed using conventional grouting methods, the slurry flows longitudinally along the pores and channels away from the heading face, resulting in unsatisfactory surrounding rock grouting reinforcement effect. In addition, during the expansion construction process, the loose strata will be disturbed many times and the support structure will also change many times. If the surrounding rock grouting reinforcement effect is not good, it will be very easy to cause surrounding rock instability and support structure damage, landslides, roof falls and other accidents, resulting in serious delays in the construction period, increased costs and even casualties, and the safety risk is extremely high. Summary of the invention

[0003] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a surrounding rock pre-reinforcement construction method suitable for large-span expansion tunnels that can improve the reinforcement effect and stability of the loose layer outside the original tunnel structure and enhance the self-stabilizing arching ability of the surrounding rock around the expanded tunnel.

[0004] The present invention achieves the above object by:

[0005] The present invention discloses a surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel, comprising the following steps: S1, after determining the grouting reinforcement range, according to a first preset spacing and a second preset spacing, respectively, along the axial direction and radial direction of the original tunnel, the first radial grouting pipes are evenly spaced, and the first radial grouting pipes are used to successively inject cement-water-glass double slurry and cement slurry into the loose layer outside the original tunnel to form a slurry-stopping wall; S2, according to a third preset spacing, along the radial direction of the original tunnel, a plurality of adjacent first radial grouting pipes are evenly spaced between the first radial grouting pipes on the original tunnel. A second radial grouting pipe is used, and cement slurry is injected into the loose layer by using the second radial grouting pipe; S3, according to the designed initial support structure contour, an advance pipe shed is set for the loose layer outside the original tunnel at the heading face, and the advance pipe shed is grouted; S4, according to the designed initial support structure contour, at the heading face, along the contour of the advance pipe shed, a number of advance small ducts are set for the loose layer, and cement slurry is injected into the advance small ducts; S5, the inspection hole method or the ultrasonic detection method is used to inspect the reinforced surrounding rock to confirm whether the surrounding rock reinforcement effect meets the standards.

[0006] Furthermore, the second preset distance is 6 meters.

[0007] Furthermore, in the step S3, the grouting includes two groutings. The first grouting uses cement-waterglass double-liquid slurry grouting, and the grouting is carried out in a low-pressure and high-flow manner, and the grouting pressure is controlled at 0.5-1.0 MPa; the second grouting uses cement slurry grouting, and the grouting pressure is increased from low to high based on the upgraded partial pressure method, and the grouting pressure is controlled at 1.0-2.0 MPa; the MPa grouting sequence should be the axis of the original tunnel chamber, from low to high, from bottom to top, first the side wall and then the arch.

[0008] Furthermore, before injecting cement slurry, the grouting process parameters are adjusted according to the specific conditions of the loose layer and the grouting reinforcement range.

[0009] Furthermore, the advanced pipe shed is made of steel flower pipes, a steel cage is arranged inside the steel flower pipes, the steel flower pipes are connected by fixing rings made of seamless steel pipes, and the steel flower pipes and the fixing rings are welded to the main bars of the steel cage.

[0010] Furthermore, the advanced pipe rack is constructed by using the pipe-following drilling technology.

[0011] Furthermore, the grouting reinforcement range, the first preset spacing, the second preset spacing, the third preset spacing, and the initial support structure profile are all designed based on the surrounding rock conditions of the exposed part of the face excavation, the original tunnel design drawings, the expanded tunnel design drawings, and the geological survey conditions of the tunnel.

[0012] Furthermore, before implementing the step S1, a temporary support structure needs to be set up at the tunnel face, and the temporary support structure is located between the original tunnel and the existing initial support structure.

[0013] Beneficial effects of the present invention:

[0014] The present invention provides a surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel. After determining the grouting reinforcement range, firstly, according to the first preset spacing and the second preset spacing, a plurality of first radial grouting pipes are evenly spaced on the original tunnel along the axial direction and radial direction of the original tunnel respectively, and the first radial grouting pipes are used to successively inject cement-water-glass double liquid slurry and cement slurry into the loose layer to block the gaps and channels in the loose layer and form a plurality of grout-stopping walls in the loose layer. Afterwards, according to the third preset spacing, a plurality of second radial grouting pipes are evenly spaced between two adjacent first radial grouting pipes along the radial direction of the original tunnel. pipe, and inject cement slurry. Under the action of the slurry-stopping wall, the slurry cannot flow along the pores and channels, so that the soil and stone materials in the loose layer are fully bonded and consolidated with sufficient cement slurry, thereby ensuring and improving the consolidation effect of the surrounding rock. Thereafter, at the heading face, according to the designed initial support structure contour, an advance pipe shed is set for the original tunnel, and the advance pipe shed and the surrounding area of ​​the advance pipe shed are grouting. Then, according to the designed initial support structure contour, a number of advance small guide tubes are set along the outer contour of the advance pipe shed, and cement slurry is injected into the advance small guide tubes, thereby making the advance pipe shed bonded to the surrounding rock, thereby improving the stability of the surrounding rock and enhancing the self-stabilizing arching ability of the surrounding rock around the expanded tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The present invention is further described below in conjunction with the accompanying drawings and embodiments:

[0016] Figure 1 A schematic cross-sectional view of a tunnel structure before implementing a surrounding rock pre-reinforcement construction method applicable to a large-span expansion tunnel of the present invention;

[0017] Figure 2 A schematic longitudinal section diagram of a tunnel structure before implementing a surrounding rock pre-reinforcement construction method applicable to a large-span expansion tunnel of the present invention;

[0018] Figure 3 is a schematic cross-sectional view of the tunnel structure after implementing step S1;

[0019] Figure 4 A schematic diagram of the longitudinal section of the tunnel structure after the implementation of step S1;

[0020] Figure 5is a schematic cross-sectional view of the tunnel structure after implementing steps S2-S4;

[0021] Figure 6 for Figure 5 A is an enlarged schematic diagram;

[0022] Figure 7 It is a schematic diagram of the longitudinal section of the tunnel structure after implementing steps S2-S4.

[0023] In the figure, 1- grouting reinforcement scope, 2- tunnel, 3- first radial grouting pipe, 4- loose layer, 5- grouting wall, 6- excavation exposed part, 7- erected initial support structure, 8- second radial grouting pipe, 9- heading face, 10- advance pipe shed, 11- surrounding rock, 12- advance small guide tube, 13- temporary support structure. DETAILED DESCRIPTION

[0024] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with examples and drawings. The schematic implementation scheme of the present invention and its description are only used to analyze the present invention and are not intended to limit the present invention.

[0025] Figure 1-Figure 7 The specific operation of a surrounding rock pre-reinforcement construction method applicable to a large-span expansion tunnel in one embodiment of the present invention is shown. The surrounding rock pre-reinforcement method specifically includes the following steps:

[0026] S1, after determining the grouting reinforcement range 1, according to the first preset spacing and the second preset spacing, the first radial grouting pipes 3 are arranged at equal intervals along the axial direction and the radial direction of the original tunnel 2, and the first radial grouting pipes 3 are used to successively inject cement-water-glass double slurry and cement slurry into the loose layer 4 outside the original tunnel 2 to form a slurry-stopping wall 5;

[0027] Specifically, before the surrounding rock pre-reinforcement construction is carried out, the surrounding rock conditions of the part 6 exposed by excavation outside the original tunnel 2 are judged and explored according to the construction drawings of the original tunnel, the design drawings of the expanded tunnel, and the geological information of the original tunnel periphery collected by survey, and the specific conditions of the surrounding rock and loose layer outside the original tunnel are determined, and the grouting reinforcement range 1 is determined according to the judgment result. The grouting reinforcement range 1 is as follows: Figure 1 and Figure 2 shown.

[0028] After determining the grouting reinforcement range 1, the first preset spacing, the second preset spacing, the third preset spacing, and the initial support structure profile are determined according to the specific conditions of the surrounding rock and loose layer 4 of the original tunnel 2, and then, Figure 3 and Figure 4As shown, firstly, according to the first preset spacing, along the axial direction of the original tunnel 2, the first radial grouting pipes 3 are evenly spaced on the original tunnel 2, and then, taking the first radial grouting pipe as a positioning standard, along the radial direction of the original tunnel 2, the remaining first radial grouting pipes 3 are evenly spaced on the original tunnel 2 according to the second preset spacing;

[0029] After the first radial grouting pipe 3 is installed, cement-water-glass double-liquid slurry and cement slurry are injected into the loose layer 4 outside the original tunnel 2 respectively by using the first radial grouting pipe 3. The cement-water-glass double-liquid slurry has the characteristic of fast coagulation speed. The cement-water-glass double-liquid slurry is injected first to quickly block the pores and channels of the loose layer 4 around the first radial grouting 3 to prevent the cement slurry from flowing along the pores and channels. Then, the cement slurry is injected to bond and solidify with the pores and channels to improve the blocking effect, thereby forming a slurry stop wall.

[0030] In this embodiment, preferably, the second preset distance is 6 meters; in other embodiments, the second preset distance can be appropriately adjusted according to on-site conditions.

[0031] S2, according to a third preset spacing, along the radial direction of the original tunnel 2, between two adjacent first radial grouting pipes 3 on the original tunnel 2, a plurality of second radial grouting pipes 8 are equally spaced, and cement slurry is injected into the loose layer 4 by using the second radial grouting pipes 8;

[0032] like Figure 7 As shown, after the grouting wall 5 is formed, according to the third preset spacing determined before implementing the step S1, a number of third radial grouting pipes 8 are evenly spaced along the radial direction of the original tunnel 2 and between two adjacent first radial grouting pipes 3 on the original tunnel 2, and cement slurry is injected into the loose layer 4 using the second radial grouting pipes 8. Thanks to the grouting wall 5 obtained by implementing the step S1, the grouting wall 5 prevents the cement slurry from flowing along the pores and channels of the loose layer 4, ensuring that there is sufficient cement slurry between the two grouting walls 5. A sufficient amount of cement slurry is conducive to the full bonding and consolidation of the material in the loose layer 4 and the cement slurry, thereby improving the consolidation degree of the surrounding rock 11.

[0033] S3, according to the designed initial support structure profile, at the tunnel face 9, an advanced pipe shed 10 is set on the loose layer 4 outside the original tunnel 2, and cement slurry is injected into the advanced pipe shed 10;

[0034] like Figure 5 , Figure 6 and Figure 7As shown, according to the initial support structure profile designed before implementing the step S1, the range of the advanced pipe shed 10 is determined, and then, at the tunnel face 9, the advanced pipe shed 10 is driven into the loose layer 4 outside the original tunnel 2, and after the driving is completed, grouting is injected into the advanced pipe shed 10;

[0035] Among them, the grouting includes two grouting times. The first grouting uses cement-water-glass double-liquid slurry grouting, and the grouting is carried out in a low-pressure and high-flow manner. The grouting pressure is controlled at 0.5-1.0MPa. The rapid solidification characteristics of the cement-water-glass double-liquid slurry are utilized to quickly block the pores and channels in the loose layer 4 around the advanced pipe rack 10 to prevent the cement slurry from losing along the pores and channels; the second grouting uses cement slurry grouting. During the grouting, the grouting pressure is increased from low to high based on the upgraded partial pressure method, and the grouting pressure is controlled at 1.0-2.0MP; the grouting sequence should be carried out along the axis of the cavern of the original tunnel 2, from low to high, from bottom to top, first the side wall and then the arch.

[0036] Among them, the advanced pipe shed 10 is made of a steel flower pipe, a steel cage is arranged in the steel flower pipe, the steel flower pipes are fixedly connected with each other by a fixing ring made of a seamless steel pipe, and the steel flower pipe and the fixing ring are also welded to the main bars of the steel cage; by welding a steel cage in the steel flower pipe, the steel cage is used to strengthen the resistance of the steel flower pipe, so that the advanced pipe shed 10 has better support ability; by injecting cement slurry into the steel flower pipe, the cement slurry seeps into the loose layer through the small holes of the steel flower pipe, and the advanced pipe shed 10 is bonded with the loose layer material around the advanced pipe shed 10, including the surrounding rock 11 consolidated by implementing steps S1 and S2, thereby enhancing the self-stabilizing arching ability of the surrounding rock 11, and at the same time, forming a newly constructed initial support structure.

[0037] S4, according to the designed initial support structure profile, at the tunnel face 9, along the profile of the advanced pipe shed 10, a plurality of advanced small pipes 12 are set in the loose layer 4, and cement slurry is injected into the advanced small pipes 12;

[0038] Specifically, it is based on the initial support structure profile designed before step S1, such as Figure 5 , Figure 6 and Figure 7 As shown, at the tunnel face 9, holes are opened in the loose layer 4 along the contour of the advance pipe rack 10 and a number of advance small pipes 12 are installed. Then, cement slurry is injected into the advance small pipes 12. The cement slurry flows into the loose layer 4 through the small holes on the advance small pipes 12, and the weak, loose, unbonded soil layer, the sand layer with poor self-stabilization ability and the crushed rock of the gravel layer in the loose layer 4 are bonded. By reducing the loose materials and filling the voids in the loose layer 4, the stability of the loose layer is reinforced and improved, thereby ensuring the stability of the reinforced surrounding rock 11.

[0039] S5, use the inspection hole method or the ultrasonic detection method to inspect the reinforced surrounding rock to confirm whether the surrounding rock reinforcement effect meets the standards; after confirming that the surrounding rock reinforcement effect meets the standards, tunnel excavation work can be carried out.

[0040] Furthermore, in this embodiment, the grouting operations in steps S1, S2, S3, and S4 are all carried out in accordance with the principle of "combining exploration and grouting, and dividing into zones and batches", that is, before grouting, the grouting process parameters are appropriately adjusted according to the specific conditions such as the scale and shape of the loose layer, the grouting reinforcement range 1, and the field test data.

[0041] Furthermore, in this embodiment, the advanced pipe rack 10 in step S3 is actually constructed by using a pipe-following drilling process, that is, a drill rod is sleeved on the front end of a casing, and the casing and the drill rod are drilled in simultaneously, so that the advanced pipe rack is formed in one step.

[0042] Furthermore, in the present embodiment, the first radial grouting pipe 3 and the second radial grouting pipe 8 are actually radial grouting pipes of the same model and specification.

[0043] Furthermore, before implementing the step S1 , a temporary support structure 13 needs to be established at the tunnel face 9 , and the temporary support structure 13 is located between the original tunnel 2 and the constructed initial support structure 7 .

[0044] It can be understood that the above embodiments only express the preferred implementation modes of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the patent scope of the present invention. It should be pointed out that, for ordinary technicians in this field, without departing from the concept of the present invention, the above technical features can be freely combined, and several deformations and improvements can be made, which all belong to the protection scope of the present invention. Therefore, all equivalent changes and modifications made to the claims and scope of the present invention should belong to the scope covered by the claims of the present invention.

Claims

1. A surrounding rock pre-reinforcement construction method suitable for large-span expansion tunnels, characterized in that: The following steps are involved: S1, after determining the grouting reinforcement range (1), according to the first preset spacing and the second preset spacing, first radial grouting pipes (3) are arranged at equal intervals along the axial direction and the radial direction of the original tunnel (2), and the first radial grouting pipes (3) are used to successively inject cement-water-glass double slurry and cement slurry into the loose layer (4) outside the original tunnel (2) to form a grouting wall (5); S2, according to the third preset spacing, along the radial direction of the original tunnel (2), between two adjacent first radial grouting pipes (3) on the original tunnel (2), a plurality of second radial grouting pipes (8) are arranged at equal intervals, and the second radial grouting pipes (8) are used to Inject cement slurry into the loose layer (4); S3, according to the designed initial support structure contour, at the tunnel face (9), set up an advance pipe shed (10) on the loose layer (4) outside the original tunnel (2), and inject grout into the advance pipe shed (10); S4, according to the designed initial support structure contour, at the tunnel face (9), along the contour of the advance pipe shed (10), set up a plurality of advance small guide tubes (12) in the loose layer (4), and inject cement slurry into the advance small guide tubes (12); S5, use the inspection hole method or the acoustic wave detection method to inspect the reinforced surrounding rock (11) to confirm whether the reinforcement effect of the surrounding rock (11) meets the standard.

2. A surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel according to claim 1, characterized in that: The second preset distance is 6 meters.

3. A surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel according to claim 2, characterized in that: In step S3, the grouting includes two groutings. The first grouting uses cement-water-glass double-liquid grouting, and the grouting is carried out in a low-pressure and high-flow manner. The grouting pressure is controlled at 0.5-1.0 MPa. The second grouting uses cement slurry grouting. During the grouting, the grouting pressure is increased from low to high based on the upgraded partial pressure method. The grouting pressure is controlled at 1.0-2.0 MPa. The grouting sequence should be carried out along the axis of the cavern of the original tunnel (2), from low to high, from bottom to top, first the side wall and then the arch.

4. A surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel according to claim 3, characterized in that: Before injecting cement slurry, the grouting process parameters are adjusted according to the specific conditions of the loose layer (4) and the grouting reinforcement range (1).

5. The surrounding rock pre-reinforcement construction method applicable to a large-span expansion tunnel according to claim 3 is characterized in that: The advanced pipe shed (10) is made of steel flower pipes, a steel cage is arranged inside the steel flower pipes, the steel flower pipes are connected by fixing rings made of seamless steel pipes, and the steel flower pipes and the fixing rings are welded to the main bars of the steel cages.

6. A surrounding rock pre-reinforcement construction method suitable for a large-span expansion tunnel according to claim 5, characterized in that: The advanced pipe rack (10) is constructed by using a pipe-following drilling process.

7. The surrounding rock pre-reinforcement construction method applicable to a large-span expansion tunnel according to claim 1, characterized in that: The grouting reinforcement range (1), the first preset spacing, the second preset spacing, the third preset spacing, and the initial support structure profile are all designed based on the surrounding rock conditions of the exposed portion (6) of the excavation of the tunnel face (9), the original tunnel design drawings, the expanded tunnel design drawings, and the geological survey conditions of the tunnel.

8. The surrounding rock pre-reinforcement construction method applicable to a large-span expansion tunnel according to claim 1, characterized in that: Before implementing the step S1, it is also necessary to set up a temporary support structure (13) at the tunnel face (9), wherein the temporary support structure (13) is located between the original tunnel (2) and the existing initial support structure (7).

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