Method for rapidly measuring springback value of tunnel primary support sprayed concrete

Abstract

The invention relates to a method for rapidly measuring the springback amount of tunnel primary support sprayed concrete, and belongs to the technical field of tunnel concrete springback amount measurement. The method comprises the steps that the tunnel excavation depth L is selected firstly, and the total length M of the arc-shaped edge of the inner wall of a tunnel is delimited; two first concrete spraying areas are delimited on the inner wall of the tunnel from top to bottom along the arc-shaped edge by taking the arc-shaped length S as the distance, two second concrete spraying areas are delimited on the inner wall of the tunnel from top to bottom by taking the arc-shaped length S as the distance along the two first concrete spraying areas, and so on; and the roughness of the inner wall of the tunnel is increased, and a plurality of triangular pyramid-shaped grooves with the depth being H are formed in the concrete spraying areas respectively, so that the situation that the measurement result of the springback amount of the tunnel primary support sprayed concrete is not accurate, and the measurement accuracy is high is avoided. Therefore, the difficulty in measuring the real amount of the springback amount of the sprayed concrete is increased, and the springback amount measuring speed of the sprayed concrete is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel concrete rebound measurement, and in particular relates to a method for quickly measuring the rebound of initial support shotcrete in a tunnel. Background Art

[0002] As an efficient support method, shotcrete has been widely used in the initial support of tunnels. However, there is a common rebound phenomenon in the construction process of shotcrete, that is, the concrete part sprayed onto the surface of the surrounding rock fails to effectively bond, resulting in falling and rebound. The impact of shotcrete rebound on project quality and economic benefits is becoming increasingly prominent. Therefore, accurately measuring the rebound of shotcrete in the initial support of the tunnel is of great significance to optimizing construction technology and improving construction quality. At present, in the process of concrete spraying, due to the unevenness of the spraying process, the rebound of concrete at different positions may be different, which also increases the difficulty of measurement. In this regard, layered spraying is usually used to reduce the unevenness during the spraying process.

[0003] However, there are some problems in the current layered spraying, which will affect the measurement of the rebound amount of the initial support shotcrete of the tunnel: for example, in the layered spraying process, especially when spraying the bottom layer of concrete, it is necessary to ensure that the bedrock and the concrete are fully in contact and bonded. However, during the current layered spraying, when the bedrock surface is uneven, there are many gaps or unevenness, it is usually adopted to increase the thickness of the bottom layer spraying so that the bedrock and the concrete are fully in contact and bonded. However, since the shotcrete requires a certain impact force to ensure its dense combination with the bottom rock surface, when the thickness of the bottom layer spraying is too thick, the newly sprayed concrete may not be able to fill the gaps in the bottom layer concrete, resulting in a decrease in the overall density, thereby increasing the rebound, which can easily lead to inaccurate measurement results of the rebound amount of the initial support shotcrete of the tunnel, thereby increasing the difficulty of measuring the true amount of the rebound amount of the shotcrete. In this regard, a method for quickly measuring the rebound amount of the initial support shotcrete of the tunnel is proposed. Summary of the invention

[0004] In order to solve the above problems existing in the prior art, the present invention provides a method for quickly measuring the rebound amount of the initial support shotcrete of the tunnel, which solves the problem in the prior art that when the thickness of the bottom layer shotcrete is too thick, the newly shotcrete may not be able to fill the gaps in the bottom layer concrete, resulting in a decrease in the overall density, thereby increasing the rebound.

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

[0006] A method for quickly measuring the rebound amount of initial support shotcrete in a tunnel comprises the following steps:

[0007] S1: First, select the depth L of tunnel excavation, define the total length of the arc edge of the tunnel inner wall as M, take the midpoint of the arc edge as the starting point, define two first concrete spraying areas on the tunnel inner wall from top to bottom along the arc edge with an arc length S as the distance, define two second concrete spraying areas on the tunnel inner wall from top to bottom along the two first concrete spraying areas with an arc length S as the distance, define two third concrete spraying areas on the tunnel inner wall from top to bottom along the two second concrete spraying areas with an arc length S as the distance, and so on, until two Nth concrete spraying areas are defined at the bottom of the tunnel;

[0008] S2: increasing the roughness of the inner wall of the tunnel, respectively opening a number of triangular pyramidal grooves with a depth of H on the two first concrete spraying areas, the two second concrete spraying areas, ..., the two Nth concrete spraying areas, wherein the relationship between the depth H of the triangular pyramidal groove and the arc length S is: S = 2H;

[0009] S3: Select the first concrete spraying area, the N / 2 concrete spraying area and the N concrete spraying area as the test areas respectively, lay plastic films under the first concrete spraying area, the N / 2 concrete spraying area and the N concrete spraying area, and use a compression and limiting device to press the edge of the plastic film to prevent the rebounded concrete from overflowing;

[0010] S4: uniformly spray the first layer of concrete on the test area. First, use a concrete sprayer to uniformly spray concrete on three groups of areas: the first concrete spraying area, the N / 2 concrete spraying area, and the N concrete spraying area. After the spraying is completed, compaction treatment is performed, and then the temperature of the concrete is increased by heating the concrete to accelerate the hydration reaction rate.

[0011] S5: Evenly spray the middle layer of concrete on the first layer of concrete. When the first layer of concrete reaches a certain strength, evenly spray the middle layer of concrete on the first layer of concrete using a sprayer, and compact it. Then, heat the concrete to increase the temperature of the concrete so as to accelerate the hydration reaction.

[0012] S6: Evenly spray the top layer of concrete on the middle layer of concrete. After the middle layer of concrete reaches a certain strength, evenly spray the top layer of concrete on the middle layer of concrete. After spraying, compact it in time.

[0013] S7: Collect rebound materials. After the spraying is completed, wait for the initial setting of the concrete and collect all the rebound concrete on the plastic film;

[0014] S8: Weigh the rebound material, using a weighing device to weigh the mass of the collected rebound concrete;

[0015] S9: Calculate the rebound amount and the spraying amount. According to the amount of sprayed concrete and the spraying area, calculate the average thickness of the sprayed concrete, and then calculate the total amount of spraying. Finally, calculate the rebound amount of the sprayed concrete according to the rebound rate = (rebound weight / total amount of sprayed concrete) × 100%.

[0016] As a further solution of the present invention, one of the faces of the triangular pyramidal groove in S2 is parallel to the inner wall of the tunnel.

[0017] As a further solution of the present invention, the triangular pyramidal grooves in S2 are arranged in an up-and-down staggered manner.

[0018] As a further solution of the present invention, the thickness of the middle layer of concrete is twice the thickness of the first layer of concrete, and the thickness of the top layer of concrete is half the thickness of the first layer of concrete.

[0019] As a further solution of the present invention, an area is selected from the area between the first concrete spraying area and the N / 2 concrete spraying area in S3, and an area between the N / 2 concrete spraying area and the N concrete spraying area, respectively, and a plastic film is laid thereunder. The rebound amount of concrete in all areas where the plastic film is laid is calculated, and then the average value is taken as the final rebound amount.

[0020] As a further solution of the present invention, when the spraying machine is used to spray concrete, an interval spraying method is adopted.

[0021] As a further solution of the present invention, a layer of liquid paraffin or silicone oil or polyethylene wax is applied on the plastic film, so that an isolation layer is formed between the concrete and the plastic film.

[0022] As a further solution of the present invention, a flexible sealing block is provided at the edge of the plastic film, and one end of the flexible sealing block in contact with the inner wall of the tunnel is a wedge-shaped structure.

[0023] As a further solution of the present invention, the clamping and limiting device includes a support frame, a first limit frame and a second limit frame arranged on the support frame, the second limit frame is clamped on the first limit frame, and the plastic film is clamped and limited by the first limit frame and the second limit frame.

[0024] As a further solution of the present invention, the edge of the first limiting frame is provided with first saw teeth, the edge of the second limiting frame is provided with second saw teeth, and the first saw teeth are meshed with the second saw teeth.

[0025] The beneficial effects of the present invention are:

[0026] By first selecting the depth L of tunnel excavation, defining the total length of the arc edge of the tunnel inner wall as M, taking the midpoint of the arc edge as the starting point, and defining two first concrete spraying areas on the tunnel inner wall from top to bottom along the arc edge with an arc length S as the distance, defining two second concrete spraying areas on the tunnel inner wall from top to bottom along the two first concrete spraying areas with an arc length S as the distance, defining two third concrete spraying areas on the tunnel inner wall from top to bottom along the two second concrete spraying areas with an arc length S as the distance, and so on, until two Nth concrete spraying areas are defined at the bottom of the tunnel, and the roughness of the tunnel inner wall is increased, and two first concrete spraying areas are defined respectively. A number of triangular pyramidal grooves with a depth of H are opened in the spraying area, two second concrete spraying areas... and the two Nth concrete spraying areas to increase the roughness of the tunnel surface, so that the tunnel surface and the bottom layer of concrete are better combined, ensuring that the standard thickness of the bottom layer of concrete can fully contact and bond the bedrock and concrete, and avoiding the possibility that the newly sprayed concrete may not fill the gaps in the bottom layer of concrete, resulting in a decrease in the overall density and increased rebound, which can easily lead to inaccurate measurement results of the rebound amount of the initial shotcrete shotcrete of the tunnel, thereby increasing the difficulty of measuring the true amount of the shotcrete rebound, and also speeding up the measurement of the shotcrete rebound. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0028] Figure 1 It is a schematic diagram of the concrete spraying area division of the present invention;

[0029] Figure 2 It is a schematic diagram of the structure of the pressing and limiting device of the present invention.

[0030] Description of main component symbols:

[0031] In the figure: 1, support frame; 2, first limiting frame; 3, second limiting frame; 4, first sawtooth; 5, second sawtooth. DETAILED DESCRIPTION

[0032] 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.

[0033] See also Figure 1 - Figure 2 This embodiment provides a method for quickly measuring the rebound amount of shotcrete in the initial support of a tunnel, comprising the following steps:

[0034] S1: First select the depth L of tunnel excavation, define the total length of the arc edge of the tunnel inner wall as M, take the midpoint of the arc edge as the starting point, and define two first concrete spraying areas on the tunnel inner wall from top to bottom along the arc edge with an arc length S as the distance, define two second concrete spraying areas on the tunnel inner wall from top to bottom along the two first concrete spraying areas with an arc length S as the distance, define two third concrete spraying areas on the tunnel inner wall from top to bottom along the two second concrete spraying areas with an arc length S as the distance, and so on, until two Nth concrete spraying areas are defined at the bottom of the tunnel; the measurement of the rebound amount of the initial shotcrete of the tunnel here is during the construction process It is carried out in the tunnel, that is, when the tunnel is just excavated and initially supported, so as to timely discover the problem of excessive rebound and take measures to adjust it. Therefore, the selected tunnel excavation depth L here should be the standard depth of tunnel excavation. This depth is carried out in accordance with the national standard. The total length of the arc edge of the inner wall of the tunnel refers to the overall arc length from the top to the bottom of the tunnel. Two first concrete spraying areas, two second concrete spraying areas... two Nth concrete spraying areas are drawn. The purpose is to ensure that when the rebound of the initial support shotcrete of the tunnel is evenly measured, the overall stability of the tunnel must also be ensured. In addition, the two first concrete spraying areas are connected together, just connecting the top of the tunnel with the left and right sides;

[0035] S2: Increase the roughness of the inner wall of the tunnel, and respectively open a number of triangular pyramid grooves with a depth of H on two first concrete spraying areas, two second concrete spraying areas...two Nth concrete spraying areas, wherein the relationship between the depth H of the triangular pyramid groove and the arc length S is: S=2H. Since it is necessary to consider that the stability of the inner wall of the tunnel in the area of ​​the arc length S is not affected when opening the triangular pyramid groove, the longer the arc length S is, the greater the depth H of the triangular pyramid groove can be designed, so that the effect of providing a fulcrum for concrete on the inner wall of the tunnel is better. However, it is also necessary to ensure that the depth of the triangular pyramid groove does not exceed half of the arc length S, so as to ensure that the stability of the inner wall of the tunnel is not affected. In addition, increasing the roughness and setting the triangular pyramid groove increases the roughness of the inner wall of the tunnel. One of the faces of the triangular pyramid groove is parallel to the inner wall of the tunnel, which is equivalent to one of the corners of the triangular pyramid groove being perpendicular to the inner wall of the tunnel. When spraying concrete, part of the concrete will enter the triangular pyramid groove to make the tunnel more stable, and it is also equivalent to providing a fulcrum for concrete on the inner wall of the tunnel, so that the overall density is increased;

[0036] S3: Select the first concrete spraying area, the N / 2 concrete spraying area and the N concrete spraying area as the test areas respectively, lay plastic films under the first concrete spraying area, the N / 2 concrete spraying area and the N concrete spraying area, and use a compression and limiting device to press the edge of the plastic film to prevent the rebounded concrete from overflowing;

[0037] S4: uniformly spray the first layer of concrete on the test area. First, use a concrete sprayer to uniformly spray concrete on three groups of areas: the first concrete spraying area, the N / 2 concrete spraying area, and the N concrete spraying area. After the spraying is completed, compaction treatment is performed, and then the temperature of the concrete is increased by heating the concrete to accelerate the hydration reaction rate.

[0038] S5: Evenly spray the middle layer of concrete on the first layer of concrete. When the first layer of concrete reaches a certain strength, evenly spray the middle layer of concrete on the first layer of concrete using a sprayer, and compact it. Then, heat the concrete to increase the temperature of the concrete so as to accelerate the hydration reaction.

[0039] S6: Evenly spray the top layer of concrete on the middle layer of concrete. After the middle layer of concrete reaches a certain strength, evenly spray the top layer of concrete on the middle layer of concrete. After spraying, compact it in time.

[0040] S7: Collect rebound materials. After the spraying is completed, wait for the initial setting of the concrete and collect all the rebound concrete on the plastic film;

[0041] S8: Weighing the rebound material, using a weighing device to weigh the mass of the collected rebound concrete; the weighing device may be an electronic scale;

[0042] S9: Calculate the rebound amount and the spraying amount. According to the amount of sprayed concrete and the spraying area, calculate the average thickness of the sprayed concrete, and then calculate the total amount of spraying. Finally, calculate the rebound amount of the sprayed concrete according to the rebound rate = (rebound weight / total amount of sprayed concrete) × 100%.

[0043] Due to some problems in the current layered spraying, it will affect the measurement of the rebound amount of the initial support shotcrete of the tunnel: for example, in the layered spraying process, especially when spraying the bottom layer of concrete, it is necessary to ensure that the bedrock and the concrete are fully in contact and bonded. However, during the current layered spraying, when the bedrock surface is uneven, there are many gaps or unevenness, it is usually adopted to increase the thickness of the bottom layer spraying so that the bedrock and the concrete are fully in contact and bonded. However, since the shotcrete needs a certain impact force to ensure its dense combination with the bottom rock surface, when the thickness of the bottom layer spraying is too thick, the newly sprayed concrete may not be able to fill the gaps in the bottom layer concrete, resulting in a decrease in the overall density, thereby increasing the rebound, which can easily lead to inaccurate measurement results of the rebound amount of the initial support shotcrete of the tunnel, thereby increasing the difficulty of measuring the true amount of the shotcrete rebound.

[0044] In order to solve the above problems, in this embodiment, by first selecting the depth L of tunnel excavation, the total length of the arc side of the tunnel inner wall is defined as M, and taking the midpoint of the arc side as the starting point, two first concrete spraying areas are defined on the tunnel inner wall from top to bottom along the arc side with an arc length S as a distance, two second concrete spraying areas are defined on the tunnel inner wall from top to bottom along the two first concrete spraying areas with an arc length S as a distance, two third concrete spraying areas are defined on the tunnel inner wall from top to bottom along the two second concrete spraying areas with an arc length S as a distance, and so on, until two Nth concrete spraying areas are defined at the bottom of the tunnel, and the roughness of the tunnel inner wall is increased, respectively. A number of triangular pyramidal grooves with a depth of H are opened in the two first concrete spraying areas, the two second concrete spraying areas...the two Nth concrete spraying areas to increase the roughness of the tunnel surface, thereby making the tunnel surface better combined with the bottom layer of concrete, ensuring that the bedrock and concrete can be fully contacted and bonded by using the bottom layer of concrete of standard thickness, thereby avoiding the possibility that the newly sprayed concrete may fail to fill the gaps in the bottom layer of concrete, resulting in a decrease in the overall density and thus increased rebound, which can easily lead to inaccurate measurement results of the rebound amount of the initial shotcrete sprayed in the tunnel, thereby increasing the difficulty of measuring the true amount of the shotcrete rebound, and also speeding up the measurement of the shotcrete rebound amount.

[0045] In order to increase the stability of the tunnel and improve the bonding effect between the bedrock and the concrete, and further speed up the subsequent measurement of the rebound amount of the shotcrete, in one embodiment, the triangular pyramidal grooves in S2 are arranged in an up-and-down staggered manner. The staggered triangular pyramidal grooves can make the bedrock structure more stable and can provide more support points for the concrete, thereby increasing the shear resistance and compressive strength of the structure and improving the bonding effect between the bedrock and the concrete.

[0046] In addition, since the roughness of the tunnel has been increased, the thickness of the first layer of concrete is a normal thickness so that the bedrock and concrete can be bonded. However, what are the requirements for the thickness between the first layer of concrete, the middle layer of concrete and the top layer of concrete? In this regard, in one embodiment, the thickness of the middle layer of concrete is twice the thickness of the first layer of concrete, and the thickness of the top layer of concrete is half the thickness of the first layer of concrete. The reason for this design is that because the middle layer of concrete needs to bear a larger load, a thicker concrete layer is required to provide a greater bearing capacity to ensure the safety and stability of the structure. The thinner top layer of concrete is used as a protective layer to prevent environmental factors from damaging the internal structure. By reducing the thickness of the top layer of concrete, the cost and construction difficulty can be reduced. Thickening the middle layer can improve the performance of the overall structure without sacrificing structural performance. And why the thickness of the middle layer of concrete is twice the thickness of the first layer of concrete and the thickness of the top layer of concrete is half the thickness of the first layer of concrete? It is to facilitate construction and to provide data for the subsequent measurement of the rebound of the initial support shotcrete of the tunnel.

[0047] Since the rapid measurement of the rebound of the initial shotcrete of the tunnel usually needs to be carried out in a local area, this may cause the measurement result to not fully represent the rebound of the initial shotcrete of the entire tunnel. In order to ensure rapid measurement as much as possible while increasing the accuracy of the measurement result, in one embodiment, an area is selected from the area between the first concrete spraying area and the N / 2 concrete spraying area in S3, and the area between the N / 2 concrete spraying area and the N concrete spraying area, respectively, and a plastic film is laid thereunder. The rebound of concrete in all areas where the plastic film is laid is calculated, and then the average value is taken as the final rebound. By selecting the above special positions, and at other special positions, A plastic film is laid underneath, and the rebound of concrete in all areas where the plastic film is laid is calculated. The average value is then taken as the final rebound value, so as to ensure fast measurement while increasing the accuracy of the measurement results as much as possible. In addition, the location selected here is selected based on the size of the tunnel and the rock material of the tunnel. If the tunnel is large, one more area can be selected at the midpoint of each two adjacent concrete spraying areas, and the average value is taken at last. However, one thing to note is that each time an additional area is added, an area needs to be selected at the midpoint of each two adjacent concrete spraying areas, and the same operation is performed at symmetrical positions, so as to avoid too large intervals between the selected areas, which will again affect the accuracy of the measurement results.

[0048] At the same time, when spraying concrete, in order to make the concrete sprayed more evenly, so as to avoid the influence of the uneven concrete on the rebound amount of the initial sprayed concrete of the measuring tunnel, in one embodiment, when the concrete is sprayed by a sprayer, an interval spraying method is adopted. The interval spraying method is to divide the spraying area into 1, 2, 3...B, and then spray 1, 3, 5...areas in turn, and then spray 2, 4, 6...areas. In this way, the concrete can be sprayed more evenly, and the overlap of the areas sprayed twice can be avoided, so as to ensure that each area can be evenly covered to avoid overlap or omission.

[0049] It is worth mentioning that when the rebound objects are collected in S7, the rebound concrete on the plastic film may stick to the plastic film, resulting in the inability to remove all the rebound concrete, affecting the rebound amount of the initial shotcrete of the tunnel. In order to solve this problem, in one embodiment, a layer of liquid paraffin or silicone oil or polyethylene wax is applied to the plastic film to form an isolation layer between the concrete and the plastic film. The specific operation method for forming the isolation layer is as follows: before applying the separation layer, thoroughly clean the surface of the plastic film to remove dust, oil and other impurities, ensure that the separation agent can be evenly applied and effectively adhered, and use a spray gun, brush or roller to evenly apply the separation agent. Apply it on the surface of the plastic film. After applying the separation agent, let it dry naturally or use a hot air gun to accelerate the drying process until the separation agent is completely dry and forms a uniform separation layer. This solves the problem that the rebound concrete cannot be completely removed, affecting the rebound amount of the initial support shotcrete of the tunnel. In addition, in order to ensure good sealing between the plastic film and the inner wall of the tunnel and avoid leakage of rebounded concrete, a flexible sealing block is provided at the edge of the plastic film. The end of the flexible sealing block that contacts the inner wall of the tunnel is a wedge-shaped structure. The special shape of the wedge-shaped structure can fill the tiny gap between the flexible sealing block and the inner wall of the tunnel when embedded, which can effectively prevent fluid leakage.

[0050] Furthermore, in order to facilitate the fixing and removal of the plastic film and speed up the collection of rebound objects, the measurement of the rebound amount of the initial support shotcrete of the tunnel is accelerated. In this regard, in one embodiment, the clamping and limiting device includes a support frame 1, a first limit frame 2 and a second limit frame 3 arranged on the support frame 1, and the second limit frame 3 is clamped and arranged on the first limit frame 1. The plastic film is clamped and limited by the first limit frame 2 and the second limit frame 3. The edge of the first limit frame 2 is provided with a first saw tooth 4, and the edge of the second limit frame 3 is provided with a second saw tooth 5. The first saw tooth 4 is meshed with the second saw tooth 5. After the first saw tooth 4 is meshed with the second saw tooth 5, the plastic film is firmly fixed between the first limit frame 2 and the second limit frame 3, which can ensure that the plastic film will not move when collecting the rebound objects. At the same time, it is also easy to remove after the rebound objects are collected.

[0051] 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 method for quickly measuring the rebound of initial support shotcrete in a tunnel, characterized in that: The following steps are involved: S1: First select the tunnel excavation depth L, and define the total length of the arc edge of the tunnel inner wall as M. Taking the midpoint of the arc side as the starting point, two first concrete spraying areas are delineated on the inner wall of the tunnel from top to bottom along the arc side with an arc length S as the distance, two second concrete spraying areas are delineated on the inner wall of the tunnel from top to bottom along the two first concrete spraying areas with an arc length S as the distance, two third concrete spraying areas are delineated on the inner wall of the tunnel from top to bottom along the two second concrete spraying areas with an arc length S as the distance, and so on, until two Nth concrete spraying areas are delineated at the bottom of the tunnel; S2: increasing the roughness of the inner wall of the tunnel, respectively opening a number of triangular pyramidal grooves with a depth of H on the two first concrete spraying areas, the two second concrete spraying areas, ..., the two Nth concrete spraying areas, wherein the relationship between the depth H of the triangular pyramidal groove and the arc length S is: S = 2H; S3: Select the first concrete spraying area, the N / 2 concrete spraying area and the N concrete spraying area as the test areas respectively, lay plastic films under the first concrete spraying area, the N / 2 concrete spraying area and the N concrete spraying area, and use a compression and limiting device to press the edge of the plastic film to prevent the rebounded concrete from overflowing; S4: uniformly spray the first layer of concrete on the test area. First, use a concrete sprayer to uniformly spray concrete on three groups of areas: the first concrete spraying area, the N / 2 concrete spraying area, and the N concrete spraying area. After the spraying is completed, compaction treatment is performed, and then the temperature of the concrete is increased by heating the concrete to accelerate the hydration reaction rate. S5: Evenly spray the middle layer of concrete on the first layer of concrete. When the first layer of concrete reaches a certain strength, evenly spray the middle layer of concrete on the first layer of concrete using a sprayer, and compact it. Then, heat the concrete to increase the temperature of the concrete so as to accelerate the hydration reaction. S6: Spray the top layer of concrete evenly on the middle layer of concrete. After the middle layer of concrete reaches a certain strength, spray the top layer of concrete evenly on the middle layer of concrete. After spraying is completed, Compacting treatment is carried out; S7: Collect rebound materials. After the spraying is completed, wait for the initial setting of the concrete and collect all the rebound concrete on the plastic film; S8: Weigh the rebound material, using a weighing device to weigh the mass of the collected rebound concrete; S9: Calculate the rebound amount and the spraying amount. According to the amount of sprayed concrete and the spraying area, calculate the average thickness of the sprayed concrete, and then calculate the total amount of spraying. Finally, calculate the rebound amount of the sprayed concrete according to the rebound rate = (rebound weight / total amount of sprayed concrete) × 100%.

2. A method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1, characterized in that: One of the faces of the triangular pyramidal groove in S2 is parallel to the inner wall of the tunnel.

3. The method for quickly measuring the rebound of the initial support shotcrete of a tunnel according to claim 1 is characterized in that: The triangular pyramidal grooves in S2 are arranged in an up-and-down staggered manner.

4. The method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1 is characterized in that: The thickness of the middle layer of concrete is twice the thickness of the first layer of concrete, and the thickness of the top layer of concrete is half the thickness of the first layer of concrete.

5. The method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1 is characterized in that: Then, from the area between the first concrete spraying area and the N / 2 concrete spraying area in S3, and from the area between the N / 2 concrete spraying area and the N concrete spraying area, select an area respectively and lay a plastic film underneath it, calculate the rebound amount of concrete in all areas where the plastic film is laid, and then take the average value as the final rebound amount.

6. A method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1, characterized in that: When the concrete is sprayed by the spraying machine, an interval spraying method is adopted.

7. A method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1, characterized in that: A layer of liquid paraffin, silicone oil or polyethylene wax is applied on the plastic film to form an isolation layer between the concrete and the plastic film.

8. The method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1 is characterized in that: A flexible sealing block is arranged at the edge of the plastic film, and one end of the flexible sealing block in contact with the inner wall of the tunnel is a wedge-shaped structure.

9. A method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 1, characterized in that: The clamping and limiting device comprises a support frame, a first limiting frame and a second limiting frame arranged on the support frame, the second limiting frame is clamped and arranged on the first limiting frame, and the plastic film is clamped and limited by the first limiting frame and the second limiting frame.

10. A method for rapidly measuring the rebound of initial support shotcrete in a tunnel according to claim 9, characterized in that: The edge of the first limiting frame is provided with a first sawtooth, the edge of the second limiting frame is provided with a second sawtooth, and the first sawtooth is meshed with the second sawtooth.

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