A super-large span tunnel excavation conversion process

Abstract

The invention relates to a conversion process for excavating a super-large-span tunnel, and belongs to the technical field of super-large-span tunnel construction. In a cavern after excavation, when designing initial support along a tunnel arc surface, a first support, a second support ... an Nth support are designed according to the spacing of an arithmetic progression, and then the inner wall of the tunnel other than the first support, the second support ... the Nth support is reinforced by spraying concrete. When the initial support is removed, a first stress dispersion area, a second stress dispersion area ... the Nth stress dispersion area are divided in sequence, and then the first support, the third support, the fifth support ... are removed in sequence, and then the second support, the fourth support, the sixth support ... are removed in sequence until all the initial supports are removed, thereby completing the conversion process, so that near the support point, the force originally borne by the support will not be transferred to other parts, so as to avoid increasing the stress of these parts.

Description

Technical Field

[0001] The invention belongs to the technical field of super-large span tunnel construction, and in particular relates to a super-large span tunnel excavation conversion process. Background Art

[0002] In the construction of ultra-large span tunnels, construction risks are prone to occur due to the large span and spacious space. The excavation conversion process can effectively reduce construction risks and ensure construction safety. In the current ultra-large span tunnel excavation conversion process, a part of the tunnel is excavated first, and then the tunnel is initially supported. Then the tunnel is excavated until the excavation section of the entire tunnel is formed. After the tunnel excavation is completed, the initial support needs to be removed for conversion construction, converting the tunnel from the excavation stage to the lining stage.

[0003] However, there are some problems with the current tunnel excavation conversion process: since it is aimed at super-large span tunnels, compared with ordinary tunnels, the supporting structure of super-large span tunnels is subjected to complex forces and needs to withstand greater pressure and torque, which requires the supporting structure to have higher strength and stability, otherwise it is easy to cause structural damage. At present, in the conversion construction of super-large span tunnels, it is necessary to remove the initial support first. In the process of removing the initial support, the removal of the support provided by the initial support will redistribute the internal force of the structure. Near the support point, the force originally borne by the support will be transferred to other parts, which will increase the stress in these parts. It may cause stress concentration or overload in some areas, affecting the stability of the super-large span tunnel. In this regard, an super-large span tunnel excavation conversion process is proposed. Summary of the invention

[0004] In order to solve the above-mentioned problems existing in the prior art, the present invention provides a super-large span tunnel excavation conversion process, which solves the problem that in the process of removing the initial support in the prior art, the force originally borne by the support will be transferred to other parts, causing the stress in these parts to increase, affecting the stability of the super-large span tunnel.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] A super-large span tunnel excavation conversion process comprises the following steps:

[0007] S1: The first step of excavation is to excavate a part of the tunnel to form a preliminary cavern;

[0008] S2: Support and reinforcement. In the excavated cavern, the initial support is designed along the curved surface of the tunnel. The first support is set at the top of the tunnel. The second support is set at a spacing of L on both sides of the first support. The third support is set at a spacing of L+B on the side of the two second supports far away from the first support. This is repeated until the Nth support is set at a spacing of L+(N-2)B at the edge of the tunnel farthest from the first support. Then, the inner wall of the tunnel outside the first support, the second support, ... the Nth support, is reinforced by spraying concrete.

[0009] S3: Based on the first step of excavation, continue to excavate the remaining part until the excavation section of the entire tunnel is formed;

[0010] S4: After the tunnel excavation is completed, the tunnel excavation conversion construction is carried out to convert the tunnel from the excavation stage to the lining stage;

[0011] S5: Remove the initial support in S2. When removing the initial support, first mark out two first stress dispersion areas with an interval of S on both sides of the first support, and evenly spray expansive concrete on the two first stress dispersion areas. Then mark out second stress dispersion areas with an interval of S on both sides of the two second supports, and evenly spray expansive concrete on the four second stress dispersion areas. Next, mark out third stress dispersion areas with an interval of S on both sides of the two third supports, and evenly spray expansive concrete on the four third stress dispersion areas. This is repeated until an Nth stress dispersion area is marked out with an interval of S on both sides of the two Nth supports, and evenly spray expansive concrete on the four Nth stress dispersion areas. After the expansive concrete solidifies, the first support, the third support, the fifth support, ... are removed in sequence, and then the second support, the fourth support, the sixth support, ... are removed in sequence, until all the initial supports are removed.

[0012] S6: Carry out tunnel lining construction according to design requirements;

[0013] S7: Construction joint treatment: During the lining construction process, the construction joints should be treated to ensure the integrity of the lining.

[0014] As a further solution of the present invention, before S1, pre-splitting blasting is first performed to reduce the disturbance to the surrounding rock during the subsequent excavation process, and certain cracks are formed by the pre-splitting blasting to reduce the stress concentration during excavation.

[0015] As a further solution of the present invention, the shapes of the contact portions of the first support, the second support ... the Nth support in S2 with the curved surface of the tunnel match the arc shape of the curved surface of the tunnel.

[0016] As a further solution of the present invention, the length of S in S5 is smaller than the length of L, and a spacing of length T is left between the stress dispersion area and the first support, the second support ... the Nth support, and the length of T is greater than the expansion distance of the expansive concrete.

[0017] As a further solution of the present invention, the side walls of the first support, the second support ... the Nth support are all provided with slide grooves, and the slide grooves are connected to the nozzles of a concrete spraying device, and the nozzles of the concrete spraying device evenly spray concrete by sliding along the slide grooves.

[0018] As a further solution of the present invention, the width of the concrete sprayed by the nozzle is the same as the width of the stress dispersion area.

[0019] As a further solution of the present invention, the first support, the second support ... the Nth support are connected to the curved surface of the tunnel through a curved steel plate, one side of the curved steel plate is plug-connected to the curved surface of the tunnel, and the other side of the curved steel plate is fitted with the first support, the second support ... the Nth support.

[0020] As a further solution of the present invention, in S5, hot water is added to the expansive concrete or the ambient temperature is increased during the pouring process to accelerate the solidification of the expansive concrete.

[0021] The beneficial effects of the present invention are:

[0022] When designing initial support along the curved surface of the tunnel in the cavern after excavation, the first support, the second support...the Nth support are designed according to the spacing of an arithmetic progression, and then the inner wall of the tunnel other than the first support, the second support...the Nth support is reinforced by spraying concrete. When the initial support is removed, the first stress dispersion area, the second stress dispersion area...the Nth stress dispersion area are divided in sequence, and then the first support, the third support, the fifth support...are removed in sequence, and then the second support, the fourth support, the sixth support...are removed in sequence until all the initial supports are removed, thereby completing the conversion process, so that near the support point, the force originally borne by the support will not be transferred to other parts, thereby avoiding the increase of stress in these parts, and solving the problem that in the prior art, the force originally borne by the support will be transferred to other parts during the removal of the initial support, thereby increasing the stress in these parts and affecting the stability of the ultra-large span tunnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0024] Figure 1 It is the overall construction schematic diagram of the present invention;

[0025] Figure 2It is a schematic diagram of the installation position of the nozzle of the present invention.

[0026] Description of main component symbols:

[0027] In the figure: 1. First support; 2. Second support; 3. Curved surface of tunnel; 4. Nozzle. DETAILED DESCRIPTION

[0028] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention are described in detail below in conjunction with the accompanying drawings and preferred embodiments.

[0029] See also Figure 1 - Figure 2 This embodiment provides a super-long span tunnel excavation conversion process, comprising the following steps:

[0030] S1: First, pre-splitting blasting is carried out to reduce the disturbance to the surrounding rock during the subsequent excavation process. A certain amount of cracks are formed through pre-splitting blasting to reduce the stress concentration during excavation. Then the first step of excavation is to excavate a part of the tunnel to form a preliminary cavern;

[0031] S2: Support and reinforcement. In the excavated cavern, the initial support is designed along the curved surface 3 of the tunnel. The first support 1 is set at the top of the tunnel. The second supports 2 are set at intervals of L on both sides of the first support 1. The third supports are set at intervals of L+B on the sides of the two second supports 2 far away from the first support 1, and so on, until the Nth support is set at the edge of the tunnel farthest from the first support 1 at an interval of L+(N-2)B. Then, the inner wall of the tunnel other than the first support 1, the second support 2...the Nth support is reinforced by spraying concrete. The length of L and the length of B here need to be designed according to the actual width of the super-large span tunnel, and the bearing capacity of the support used for the initial support also needs to be considered. The first support 1, the second support 2...the Nth support are combined together. A structure similar to a pipe roof is formed, but different from the current pipe roof in that the first support 1, the second support 2...the Nth support are designed for super-large span tunnels under actual conditions. In addition, the spacing between the first support 1, the second support 2...the Nth support is increased in sequence using an arithmetic progression. The purpose of this design is that, since it is aimed at super-large span tunnels, the terrain may change in super-long span tunnels. The increasing spacing of the arithmetic progression can make the load borne by each support point on the top of the tunnel more uniform, avoiding excessive force on some support points, thereby improving the stability and safety of the entire structure. At the same time, by increasing the support spacing, the number of supports can be reduced while ensuring structural safety, thereby saving materials and reducing costs. In order to facilitate understanding of the solution of the present application, Figure 1Only the first and second supports are numbered, and the remaining supports are not numbered;

[0032] S3: Based on the first step of excavation, continue to excavate the remaining part until the excavation section of the entire tunnel is formed;

[0033] S4: When excavating a super-long span tunnel, multiple excavation conversion processes are required. However, the common excavation conversion process is to carry out tunnel excavation conversion construction after the tunnel excavation is completed, converting the tunnel from the excavation stage to the lining stage;

[0034] S5: Remove the initial support in S2. When removing the initial support, first mark out two first stress dispersion areas with a spacing of S on both sides of the first support 1, and evenly spray expansive concrete on the two first stress dispersion areas. Then mark out second stress dispersion areas with a spacing of S on both sides of the two second supports 2, and evenly spray expansive concrete on the four second stress dispersion areas. Next, mark out third stress dispersion areas with a spacing of S on both sides of the two third supports, and evenly spray expansive concrete on the four third stress dispersion areas. This is repeated until the Nth stress dispersion area is marked out with a spacing of S on both sides of the two Nth supports, and evenly spray expansive concrete on the four Nth stress dispersion areas. After the expansive concrete solidifies, the first support 1, the third support, the fifth support, ... are removed in sequence, and then the second support 2, the fourth support, the sixth support, ... are removed in sequence, until all the initial supports are removed.

[0035] One point that needs to be explained is that by setting up several stress dispersion areas at both ends of each support, it is equivalent to increasing the stability near the support point. When the conversion process is completed, the force originally borne by the support will be transferred to other parts. At this time, the stress dispersion area can disperse the stress, avoiding the increase of stress in these parts and affecting the stability of the super-large span tunnel. On this basis, the order of demolition can further avoid stress concentration and affect the stability of the super-large span tunnel. Therefore, after the expansive concrete solidifies, the first support 1, the third support, the fifth support... are removed in sequence, and then the second support 2, the fourth support, the sixth support... are removed in sequence until all the initial supports are removed. Because in the super-span tunnel, if all the supports are removed at one time, it may cause a sudden collapse of the top surrounding rock, which will bring great safety risks to the construction personnel and equipment. Dismantling at intervals can gradually release stress and maintain the stability of the structure. However, the first support 1, the third support, the fifth support, etc. are dismantled in sequence, and then the second support 2, the fourth support, the sixth support, etc. are dismantled in sequence. This operation can disperse the stress evenly. When problems are found when dismantling the first support 1, the third support, the fifth support, etc., the staff can also carry out subsequent repairs, thereby reducing the risks in the construction process and reducing possible unexpected situations.

[0036] In addition, it is also necessary to ensure that the length of S is less than the length of L, and a spacing of length T is left between the stress dispersion area and the first support 1, the second support 2 ... the Nth support. The length of S is less than the length of L to ensure that the expansive concrete will not interfere with the first support 1, the second support 2 ... the Nth support, and the length of T is greater than the expansion distance of the expansive concrete. The selection of the length of S needs to be designed based on the bearing capacity of the adopted support and the actual width of the super-large span tunnel. In addition, in order to prevent the expansive concrete from making the first support 1, the second support 2 ... the Nth support adhere to the inner wall of the tunnel and cannot be removed later, it is ensured that the length of T is greater than the expansion distance of the expansive concrete to avoid this problem.

[0037] S6: Carry out tunnel lining construction according to design requirements;

[0038] S7: Construction joint treatment: During the lining construction process, the construction joints should be treated to ensure the integrity of the lining.

[0039] Since it is aimed at super-large span tunnels, compared with ordinary tunnels, the supporting structure of super-large span tunnels is subjected to complex forces and needs to withstand greater pressure and torque, which requires the supporting structure to have higher strength and stability, otherwise it is easy to cause structural damage. At present, during the conversion construction of super-large span tunnels, it is necessary to remove the initial support first. In the process of removing the initial support, the removal of the support provided by the initial support will cause the internal force of the structure to be redistributed. Near the support point, the force originally borne by the support will be transferred to other parts, which will increase the stress in these parts. It may cause stress concentration or overload in some areas, affecting the stability of the super-large span tunnel.

[0040] In order to solve the above problems, it is necessary to design the initial support along the curved surface 3 of the tunnel in the cavern after excavation, and design the first support 1, the second support 2... the Nth support according to the spacing of the arithmetic progression, and then spray concrete to reinforce the inner wall of the tunnel outside the first support 1, the second support 2... the Nth support. When removing the initial support, the first stress dispersion area, the second stress dispersion area... the Nth stress dispersion area are divided in sequence, and then the first support 1, the third support, the fifth support... are removed in sequence, and then the second support 2, the fourth support, the sixth support... are removed in sequence until all the initial supports are removed, thereby completing the conversion process, so that near the support point, the force originally borne by the support will not be transferred to other parts, avoiding the increase of stress in these parts, and solving the problem that in the prior art, the force originally borne by the support will be transferred to other parts during the removal of the initial support, causing the stress in these parts to increase, affecting the stability of the ultra-large span tunnel.

[0041] It is worth mentioning that in the process of removing the initial support, the first stress dispersion area, the second stress dispersion area...the Nth stress dispersion area are divided in sequence, and then the first support 1, the third support, the fifth support... are removed in sequence, and then the second support 2, the fourth support, the sixth support... are removed in sequence until all the initial supports are removed to complete the conversion process. Although it can avoid the force originally borne by the support from being transferred to other parts and avoid increasing the stress in these parts, when the initial support is removed, the part of the initial support that contacts the inner wall of the tunnel may experience stress changes, resulting in reduced local stability. When all positions of the initial support are removed, the stability reduction is accumulated, which will eventually have a greater impact on the overall stability. In order to To solve this problem, in one embodiment, the shapes of the contact parts of the first support 1, the second support 2 ... the Nth support in S2 and the tunnel curved surface 3 are matched with the arc shape of the tunnel curved surface 3. The shapes of the contact parts of the first support 1, the second support 2 ... the Nth support and the tunnel curved surface 3 are designed to be the same as the arc shape of the corresponding parts of the tunnel curved surface 3, so that there is no gap between the several supports and the inner wall of the tunnel when supporting. This will enable the several supports to squeeze the soil on the inner wall of the tunnel tighter. When the first support 1, the second support 2 ... the Nth support are removed, the part of the initial support that is in contact with the inner wall of the tunnel has been squeezed tightly. Therefore, the problem of stress change in the part of the initial support that is in contact with the inner wall of the tunnel, which leads to reduced local stability, can be avoided.

[0042] Furthermore, in order to ensure that after the first support 1, the second support 2 ... the Nth support are set for the super-large span tunnel, concrete can be evenly sprayed for fixing. In this regard, in one embodiment, the side walls of the first support 1, the second support 2 ... the Nth support are all provided with a slide groove, and the inside and outside of the slide groove are connected to the nozzle 4 of the concrete spraying device. The nozzle 4 of the concrete spraying device evenly sprays concrete by sliding along the slide groove. The concrete spraying device here needs to be specially designed and needs to cooperate with the first support 1, the second support 2 ... the Nth support in the super-large span tunnel. In addition, in order to ensure that the expansive concrete sprayed in the stress dispersion area can better disperse the stress, it is necessary to ensure that the width of the concrete sprayed by the nozzle 4 is the same as the width of the stress dispersion area.

[0043] Furthermore, since it is aimed at a super-large span tunnel, the shapes of the contact parts of the first support 1, the second support 2 ... the Nth support and the tunnel curved surface 3 are designed to be the same as the arc shape of the corresponding parts of the tunnel curved surface 3, so that there is no gap between the several supports and the inner wall of the tunnel when supporting, so that the several supports can squeeze the soil of the inner wall of the tunnel more tightly, so as to avoid the problem of stress change in the part where the initial support contacts the inner wall of the tunnel, resulting in reduced local stability. However, when encountering a super-large span tunnel with poor rock stability, the compressed soil between the contact part of the initial support and the tunnel curved surface 3 may also affect the local stability of the tunnel. In order to solve this problem, in one embodiment, the first support 1, the second support 2 ... the Nth support and the tunnel curved surface 3 are all connected by an arc-shaped steel plate, and one side of the arc-shaped steel plate is plug-connected with the tunnel curved surface 3 , the other side of the arc-shaped steel plate is fitted with the first support 1, the second support 2...the Nth support. First of all, the arc shape of the arc-shaped steel plate also needs to match the arc-shaped surface 3 of the tunnel to ensure that it can fit with the inner wall of the tunnel without gap. In addition, before the initial support, the specific position of the support needs to be determined, and a plug rod is provided on one side of the arc-shaped steel plate, which can be plugged and connected with the arc-shaped surface 3 of the tunnel through the plug rod, and the plug rod is threaded, which can prevent the gravity of the arc-shaped steel plate from causing the plug rod to detach from the tunnel, and the other side of the arc-shaped steel plate is fitted with the first support 1, the second support 2...the Nth support. With this design, it can be ensured that when encountering an ultra-large span tunnel with not particularly good rock stability, when the initial support is removed, the compacted soil between the initial support and the contact part of the arc-shaped surface 3 of the tunnel may still maintain good stability, and the arc-shaped steel plate here does not need to be removed, and the subsequent concrete can better increase the stability of the ultra-large span tunnel.

[0044] In addition, in order to ensure that the construction period is not excessively affected after the stress dispersion area is set, in one embodiment, hot water is added to the expansive concrete or the ambient temperature is increased during the pouring process to accelerate the solidification of the expansive concrete.

[0045] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technical personnel in this field can make some changes or modify the technical contents disclosed above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any brief modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A super-large span tunnel excavation conversion process, characterized in that: The following steps are involved: S1: The first step of excavation is to excavate a part of the tunnel to form a preliminary cavern; S2: Support and reinforcement. In the excavated cavern, the initial support is designed along the curved surface of the tunnel. The first support is set at the top of the tunnel. The second support is set at a spacing of L on both sides of the first support. The third support is set at a spacing of L+B on the side of the two second supports far away from the first support. This is repeated until the Nth support is set at a spacing of L+(N-2)B at the edge of the tunnel farthest from the first support. Then, the inner wall of the tunnel outside the first support, the second support, ... the Nth support, is reinforced by spraying concrete. S3: Based on the first step of excavation, continue to excavate the remaining part until the excavation section of the entire tunnel is formed; S4: After the tunnel excavation is completed, the tunnel excavation conversion construction is carried out to convert the tunnel from the excavation stage to the lining stage; S5: Remove the initial support in S2. When removing the initial support, first mark out two first stress dispersion areas with an interval of S on both sides of the first support, and evenly spray expansive concrete on the two first stress dispersion areas. Then mark out second stress dispersion areas with an interval of S on both sides of the two second supports, and evenly spray expansive concrete on the four second stress dispersion areas. Next, mark out third stress dispersion areas with an interval of S on both sides of the two third supports, and evenly spray expansive concrete on the four third stress dispersion areas. This is repeated until an Nth stress dispersion area is marked out with an interval of S on both sides of the two Nth supports, and evenly spray expansive concrete on the four Nth stress dispersion areas. After the expansive concrete solidifies, the first support, the third support, the fifth support, ... are removed in sequence, and then the second support, the fourth support, the sixth support, ... are removed in sequence, until all the initial supports are removed. S6: Carry out tunnel lining construction according to design requirements; S7: Construction joint treatment: During the lining construction process, the construction joints should be treated to ensure the integrity of the lining.

2. The ultra-large span tunnel excavation conversion process according to claim 1 is characterized in that: Before S1, pre-splitting blasting is first performed to reduce the disturbance to the surrounding rock during the subsequent excavation process. Certain cracks are formed by pre-splitting blasting to reduce stress concentration during excavation.

3. The ultra-large span tunnel excavation conversion process according to claim 1 is characterized in that: The shapes of the contact portions of the first support, the second support, ... the Nth support in S2 with the curved surface of the tunnel match the arc shape of the curved surface of the tunnel.

4. The ultra-large span tunnel excavation conversion process according to claim 1 is characterized in that: The length of S in S5 is smaller than the length of L, and a spacing of length T is reserved between the stress dispersion area and the first support, the second support, ... the Nth support, and the length of T is larger than the expansion distance of the expansive concrete.

5. The ultra-large span tunnel excavation conversion process according to claim 1 is characterized in that: The side walls of the first support, the second support ... the Nth support are all provided with slide grooves, and the slide grooves are connected to the nozzles of a concrete spraying device inside and outside, and the nozzles of the concrete spraying device evenly spray concrete by sliding along the slide grooves.

6. The ultra-large span tunnel excavation conversion process according to claim 5 is characterized in that: The width of the concrete sprayed by the nozzle is the same as the width of the stress dispersion area.

7. The ultra-large span tunnel excavation conversion process according to claim 3 is characterized in that: The first support, the second support ... the Nth support are connected to the curved surface of the tunnel through a curved steel plate, one side of the curved steel plate is plug-connected to the curved surface of the tunnel, and the other side of the curved steel plate is in contact with the first support, the second support ... the Nth support.

8. The ultra-large span tunnel excavation conversion process according to claim 1 is characterized in that: In S5, hot water is added to the expansive concrete or the ambient temperature is increased during the pouring process to accelerate the solidification of the expansive concrete.

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