Supporting structure crossing tunnel karst cave

Abstract

The utility model provides a supporting structure crossing a tunnel karst cave, which comprises a foundation platform, a reinforced concrete span plate and a protective shed frame, the foundation platform comprises a plurality of supporting units which are arranged along the transverse direction of a tunnel, and each supporting unit comprises a first lap joint section and a second lap joint section which are oppositely arranged along the extending direction of the supporting unit. The first lap joint section is in lap joint with the side, close to the excavated tunnel section, of the tunnel karst cave, the second lap joint section is in lap joint with the side, away from the excavated tunnel section, of the tunnel karst cave, the reinforced concrete span plate is arranged on the top of the foundation platform, and the bottom end of the protection shed frame is connected to the top of the foundation platform so as to resist impact of falling rocks in the cave. The problems that rocks fall from the top of a karst cave and water flows through the bottom in the tunnel building process can be solved, the construction efficiency is high, the foundation platform can also serve as a bottom die support of a reinforced concrete span plate, and the problem that under the condition that the bottom is free, a common formwork cannot bear the load when the reinforced concrete span plate with the large thickness is poured can be solved.

Description

Technical Field

[0001] The utility model relates to the technical field of tunnels, in particular to a support structure for spanning tunnel karst caves. Background Art

[0002] At present, during the construction of highway karst tunnels, large vertically developed karst caves (the height of the tunnel vault is greater than 10m, the depth of the tunnel invert is greater than 10m, and the longitudinal length is less than 10m) are often exposed at the heading face, posing great potential safety hazards to tunnel construction and operation. Currently, for karst caves encountered during tunnel excavation construction, when the karst cave is relatively small in scale, it is generally treated by backfilling with tunnel muck and rubble masonry. However, for terrains with relatively large karst cave spaces, it cannot be well treated, and the backfilling method will greatly weaken the water passing capacity of the karst cavity. In case of heavy rain or floods, etc., the water in the karst cavity cannot be drained in time, posing a great risk to tunnel safety.

[0003] In order not to affect the smoothness of the water passing channel at the bottom of the karst cavity, for relatively large karst caves, the prior art usually uses bridges or concrete slabs to span them. However, the front karst cavity wall is basically in a vertical state, the karst cave wall is vertical and smooth without a construction working surface, it is difficult to provide support for the concrete slab or bridge deck, and the muck generated by the front blasting excavation is also likely to block the bottom water passing channel. In addition, due to the narrow space in the tunnel, large machinery is difficult to play a role, the construction efficiency of the in-tunnel bridge is low, and the falling stones caused by the blasting vibration of the front heading face hitting the karst cavity wall are likely to injure construction workers, resulting in great construction difficulty, large potential safety hazards and low efficiency of the traditional construction method.

[0004] In view of this, it is necessary to propose a support structure for spanning tunnel karst caves to solve or at least alleviate the above defects. Summary of the Utility Model

[0005] The main purpose of the utility model is to provide a support structure for spanning tunnel karst caves, so as to solve the technical problems that when the existing technology constructs a tunnel and uses a bridge or a concrete slab to span a vertically developed tunnel karst cave, there are great construction difficulties and potential safety hazards of falling stones injuring people.

[0006] To achieve the above purpose, the utility model provides a support structure for spanning tunnel karst caves, which includes a foundation platform, a reinforced concrete cross slab and a protection shed frame, wherein,

[0007] The foundation platform includes a plurality of support units arranged transversely along the tunnel. Each support unit includes a first lapping section and a second lapping section arranged oppositely along its own extending direction. The first lapping section laps on one side of the tunnel karst cave close to the excavated tunnel section, and the second lapping section laps on the other side of the tunnel karst cave far from the excavated tunnel section;

[0008] The reinforced concrete slab spanning across is arranged on the top of the foundation platform, and the bottom end of the protective shed frame is connected to the top of the foundation platform to resist the impact of falling rocks in the tunnel.

[0009] Preferably, the protective shed frame includes an outer steel arch frame structure layer, an inner steel arch frame structure layer, and an intermediate buffer layer located between the outer steel arch frame structure layer and the inner steel arch frame structure layer, wherein,

[0010] The outer steel arch frame structure layer includes multiple outer steel arch frames arranged at intervals along the extension direction of the foundation platform. A first double-layer steel mesh is hung between two adjacent outer steel arch frames, and concrete is sprayed inside the first double-layer steel mesh to form a first concrete spraying layer. The outer steel arch frames are erected on the top of the foundation platform;

[0011] The inner steel arch frame structure layer is arranged inside the outer steel arch frame structure layer and has a partition space with the outer steel arch frame structure layer. The inner steel arch frame structure layer includes multiple inner steel arch frames arranged at intervals along the extension direction of the foundation platform. A second double-layer steel mesh is hung between two adjacent inner steel arch frames, and concrete is sprayed inside the second double-layer steel mesh to form a second concrete spraying layer. The inner steel arch frames are erected on the top of the foundation platform;

[0012] Sand grains are filled in the partition space to form the intermediate buffer layer.

[0013] Preferably, the length of the first overlapping section and / or the second overlapping section is greater than 3m.

[0014] Preferably, the support unit is an I-beam.

[0015] Preferably, the reinforced concrete slab spanning across includes a first end and a second end opposite to each other along its own extension direction. The first end matches the first overlapping section, and the second end matches the second overlapping section.

[0016] Preferably, the protective shed frame further includes a reinforced concrete arch wall arranged inside the inner steel arch frame structure layer, and the bottom of the reinforced concrete arch wall is connected to the top of the reinforced concrete slab spanning across.

[0017] Preferably, the thickness of the reinforced concrete slab spanning across is set between 0.8m and 1.2m.

[0018] Preferably, the reinforced concrete arch wall adopts a reinforced concrete structure with a thickness of 60cm.

[0019] Preferably, the first double-layer steel bar mesh includes a first steel bar mesh and a second steel bar mesh respectively arranged on both sides of the outer steel arch. The first steel bar mesh is connected to the outer side wall of the outer steel arch, and the second steel bar mesh is connected to the inner side wall of the outer steel arch. The spacing distance between the first steel bar mesh and the second steel bar mesh matches the thickness of the outer steel arch;

[0020] The second double-layer steel bar mesh includes a third steel bar mesh and a fourth steel bar mesh respectively arranged on both sides of the inner steel arch. The third steel bar mesh is connected to the outer side wall of the inner steel arch, and the fourth steel bar mesh is connected to the inner side wall of the inner steel arch. The spacing distance between the third steel bar mesh and the fourth steel bar mesh matches the thickness of the inner steel arch.

[0021] Preferably, the mesh size of the first steel bar mesh and the second steel bar mesh is set to 5 cm * 5 cm, and the mesh size of the third steel bar mesh and the fourth steel bar mesh is set to 10 cm * 10 cm.

[0022] Compared with the prior art, the utility model has the following beneficial effects:

[0023] The utility model provides a support structure for spanning a tunnel karst cave, including a foundation platform, a reinforced concrete cross slab, and a protection shed. The foundation platform includes a plurality of support units arranged horizontally along the tunnel. Each support unit includes a first overlapping section and a second overlapping section arranged oppositely along its extending direction. The first overlapping section overlaps on one side of the tunnel karst cave close to the excavated tunnel section, and the second overlapping section overlaps on the side of the tunnel karst cave far from the excavated tunnel section. The reinforced concrete cross slab is arranged on the top of the foundation platform, and the bottom end of the protection shed is connected to the top of the foundation platform to resist the impact of falling rocks in the cave. This application can solve the problems of falling rocks at the top and water passing through at the bottom of the karst cave during the tunnel construction process, with high safety, and can be constructed using small mechanical equipment, with high construction efficiency. The foundation platform can also serve as the bottom formwork support for the reinforced concrete cross slab, which can solve the problem that the general formwork cannot bear the load during the pouring of the reinforced concrete cross slab with a large thickness in the case of bottom airspace. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on the structures shown in these drawings.

[0025] Figure 1 It is a schematic diagram of the overall structure in an embodiment of the present utility model;

[0026] Figure 2 is Figure 1 the enlarged schematic view of part A in

[0027] Figure 3 the combined structural schematic view of the outer steel arch frame structure layer, the inner steel arch frame structure layer and the intermediate buffer layer in an embodiment of the present utility model;

[0028] Figure 4 the elevation schematic view after the construction of the complete overall structure in an embodiment of the present utility model;

[0029] Figure 5 the structural schematic view after drilling the overlapping blind holes in an embodiment of the present utility model;

[0030] Figure 6 the structural schematic view after overlapping the foundation platform well in an embodiment of the present utility model;

[0031] Figure 7 the longitudinal sectional schematic view after the construction of the complete overall structure in an embodiment of the present utility model.

[0032] The realization of the purpose, the functional features and the advantages of the present utility model will be further described with reference to the embodiments and the accompanying drawings.

[0033] Explanation of the reference numerals in the drawings:

[0034] 10. Foundation platform; 110. Support unit; 111. First overlapping section; 112. Second overlapping section; 20. Reinforced concrete cross slab; 210. First end; 220. Second end; 30. Protection shed; 310. Outer steel arch frame structure layer; 311. Outer steel arch frame; 312. First double-layer steel mesh; 320. Inner steel arch frame structure layer; 321. Inner steel arch frame; 322. Second double-layer steel mesh; 330. Intermediate buffer layer; 340. Reinforced concrete arch wall; 40. Tunnel karst cave; 410. Overlapping blind hole; 420. Construction platform; 430. Overlapping platform; 50. Excavated tunnel section. Detailed implementation manners

[0035] It should be understood that the specific embodiments described herein are only used to explain the present utility model and are not used to limit the present utility model.

[0036] Next, the technical solutions in the embodiments of the present utility model will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present utility model. Obviously, the described embodiments are only a part of the embodiments of the present utility model, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present utility model without creative efforts shall fall within the protection scope of the present utility model.

[0037] It should be noted that all directional indications (such as up, down, left, right, front, back...) in the embodiments of the present utility model are only used to explain the relative positional relationship, movement conditions, etc. between components in a certain specific posture (as described in the attached drawings). If this specific posture changes, the directional indications will also change accordingly.

[0038] In addition, the descriptions involving "first", "second", etc. in the present utility model are only for descriptive purposes, and cannot be understood as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present utility model.

[0039] Please refer to the attached Figures 1 to 7 , a support structure for crossing a tunnel karst cave 40 in an embodiment provided by the present utility model includes a foundation platform 10, a reinforced concrete cross - plate 20, and a protective shed frame 30. Among them, it should be noted that when facing the tunnel karst cave 40, especially the vertically - developed tunnel karst cave 40, especially the large vertically - developed karst cave with a height greater than 10 m and a depth greater than 10 m, the tunnel will face problems such as falling rocks at the top (this section of the tunnel structure will be completely exposed in a huge cavity), water passing through at the bottom, and the vertical and smooth karst cave walls without a construction operation surface during the construction process. As Figure 5 shown, a construction platform 420 can be excavated downward at a position near the tunnel karst cave 40 in the already - excavated tunnel section 50. The construction platform 420 can be used for temporary construction machinery operations, such as drilling devices, etc., and can also be used for the foundation platform 10 to be lapped later.

[0040] The foundation platform 10 includes a plurality of support units 110 arranged transversely along the tunnel. Each support unit 110 includes a first lapping section 111 and a second lapping section 112 arranged oppositely along its own extending direction. The first lapping section 111 lapps on one side of the tunnel karst cave 40 close to the already - excavated tunnel section 50, and the second lapping section 112 lapps on the other side of the tunnel karst cave 40 far from the already - excavated tunnel section 50;

[0041] Specifically, as Figures 5 - 6As shown, a row of overlapping blind holes 410 can be drilled on the opposite side walls of the tunnel karst cave 40 on the construction platform 420. Preferably, a down-the-hole drill is used as the drilling device, which has accurate positioning ability and fast construction ability, and can quickly and accurately drill the overlapping blind holes 410. The second overlapping section 112 of each support unit 110 is successively pushed into the corresponding overlapping blind hole 410, and the first overlapping section 111 overlaps on the construction platform 420, and adjacent two support units 110 are welded and fixed through connecting bars to form the foundation platform 10. By using a drilling device to drill and groove on the opposite karst cave wall and pushing a row of support units 110 into the opposite overlapping blind holes 410 to form the foundation platform 10, the problem that the karst cave wall is vertically smooth without a construction working surface and it is difficult to provide support for the concrete slab or bridge deck is effectively solved. Considering the problem of pouring a large-volume reinforced concrete cross slab 20 in a suspended state, the foundation platform 10 of the present application can also serve as the bottom formwork support for the reinforced concrete cross slab 20, which can solve the problem that the general formwork cannot bear the load during the pouring of the reinforced concrete cross slab 20 with a large thickness (such as 1 m) in the case of the bottom being empty.

[0042] The reinforced concrete cross slab 20 is arranged on the top of the foundation platform 10, and the bottom end of the protection shed frame 30 is connected to the top of the foundation platform 10 to resist the impact of falling rocks in the cave.

[0043] Those skilled in the art need to note that the karst cavity wall is temporarily stable without disturbance. However, due to the blasting vibration of the front heading face, the falling rocks caused by the karst cavity wall are likely to injure the construction workers. Therefore, it is crucial to construct the protection shed frame 30 inside the karst cavity before the heading face blasting.

[0044] Currently, the pipe shed is usually constructed outside the tunnel contour line to form the protection shed frame 30. However, constructing the pipe shed inside the tunnel requires excavating a pipe shed chamber and an arc-shaped drilling row, which is extremely inconvenient for construction, difficult for drilling positioning, and the pipe shed protection shed frame 30 is difficult to effectively resist the impact of falling rocks.

[0045] In order to avoid the falling rocks from the karst cavity wall injuring the workers during the blasting of the front tunnel heading face and prevent the subsequent main structure lining from being damaged by the impact of falling rocks during operation, the protection shed frame 30 needs to be constructed on the foundation platform 10 in the present application. Specifically, first, a plurality of outer steel arch frames 311 arranged at intervals along the extension direction of the foundation platform 10 are installed above the foundation platform 10, and a first double-layer steel mesh 312 is hung between adjacent two outer steel arch frames 311, and then concrete is sprayed towards the first double-layer steel mesh 312 to obtain the outer steel arch frame structure layer 310. The outer steel arch frame structure layer 310 includes the outer steel arch frames 311, the first double-layer steel mesh 312, and the corresponding sprayed concrete.

[0046] As a preferred embodiment, the protective shed frame 30 includes an outer steel arch frame structure layer 310, an inner steel arch frame structure layer 320, and an intermediate buffer layer 330 located between the outer steel arch frame structure layer 310 and the inner steel arch frame structure layer 320. Among them, the outer steel arch frame structure layer 310 includes a plurality of outer steel arch frames 311 arranged at intervals along the extension direction of the foundation platform 10. A first double-layer steel mesh 312 is hung between two adjacent outer steel arch frames 311. Concrete is sprayed in the first double-layer steel mesh 312 to form a first concrete spraying layer (not shown in the figure). The outer steel arch frame 311 is erected on the top of the foundation platform 10;

[0047] The inner steel arch frame structure layer 320 is arranged inside the outer steel arch frame structure layer 310 and has a partition space (not shown in the figure) between it and the outer steel arch frame structure layer 310. The inner steel arch frame structure layer 320 includes a plurality of inner steel arch frames 321 arranged at intervals along the extension direction of the foundation platform 10. A second double-layer steel mesh 322 is hung between two adjacent inner steel arch frames 321. Concrete is sprayed in the second double-layer steel mesh 322 to form a second concrete spraying layer. The inner steel arch frame 321 is erected on the top of the foundation platform 10;

[0048] It should be noted that in order to enable the sprayed concrete to effectively adhere, in a preferred embodiment, the first double-layer steel mesh 312 includes a first steel mesh (not shown in the figure) and a second steel mesh (not shown in the figure) respectively arranged on both sides of the outer steel arch frame 311. The first steel mesh is connected to the outer side wall of the outer steel arch frame 311, and the second steel mesh is connected to the inner side wall of the outer steel arch frame 311. The spacing distance between the first steel mesh and the second steel mesh matches the thickness of the outer steel arch frame 311. The mesh size of the first steel mesh and the second steel mesh is set to 5 cm * 5 cm. In other embodiments, those skilled in the art can also set the mesh size to other shapes or values as long as it is convenient for the sprayed concrete to adhere.

[0049] As a preferred embodiment, the first double-layer steel mesh 312 includes a first steel mesh and a second steel mesh respectively arranged on both sides of the outer steel arch frame 311. The first steel mesh is connected to the outer side wall of the outer steel arch frame 311, and the second steel mesh is connected to the inner side wall of the outer steel arch frame 311. The spacing distance between the first steel mesh and the second steel mesh matches the thickness of the outer steel arch frame 311, for example, it is set to be equal;

[0050] The second double-layer steel mesh 322 includes a third steel mesh and a fourth steel mesh respectively arranged on both sides of the inner steel arch 321, the third steel mesh is connected to the outer wall of the inner steel arch 321, and the fourth steel mesh is connected to the inner wall of the inner steel arch 321. The spacing distance between the third steel mesh and the fourth steel mesh matches the thickness of the inner steel arch 321, for example, is set to be equal.

[0051] As a preferred example, the mesh size of the first steel mesh and the second steel mesh is set to 5cm*5cm, and the mesh size of the third steel mesh and the fourth steel mesh is set to 10cm*10cm. In other embodiments, those skilled in the art can also set the mesh size to a shape or other value as long as it is convenient for sprayed concrete to adhere.

[0052] Sand is blown into the interlayer space to form the intermediate buffer layer 330. It is worth noting that a blowing and filling pipe (not shown) is reserved before the inner steel arch frame 321 is sprayed with concrete. The blowing and filling pipe is fixed to the inner steel arch frame 321 through connecting ribs. The outlet of the blowing and filling pipe faces the outer steel arch frame 311, and the inlet of the blowing and filling pipe faces the inner side of the inner steel arch frame 321. After the upper and lower arch frames are sprayed with concrete, in a preferred example, medium-grained sand is blown into the space between the outer steel arch frame structure layer 310 and the inner steel arch frame structure layer 320 through the blowing and filling pipe as the intermediate buffer layer 330. The particle size of the medium-grained sand ranges from 0.5 to 0.25 mm. The intermediate buffer layer 330 can unload most of the impact load when the outer steel arch frame structure layer 310 is impacted by falling rocks, significantly improving the ability of the protective scaffold 30 to prevent falling rocks from hitting workers during construction, and can be used as an arch protection buffer layer during operation to prevent falling rocks from the cave roof from damaging the tunnel structure.

[0053] Furthermore, the length of the first overlapping section 111 and / or the second overlapping section 112 is greater than 3m. As a preferred example, the length of the I-beam overlapping the overlapping blind hole 410 is not less than 3m, and the length of the I-beam overlapping the construction platform 420 is not less than 3m.

[0054] Furthermore, the support unit 110 is an I-beam.

[0055] Furthermore, the reinforced concrete span 20 includes a first end 210 and a second end 220 opposite to each other along its own extension direction, the first end 210 matches the first overlap section 111, and the second end 220 matches the second overlap section 112, for example, they are set to be consistent in length.

[0056] As a preferred embodiment, the protective shed frame 30 further includes a reinforced concrete arch wall 340 disposed inside the inner steel arch frame structure layer 320, and the bottom of the reinforced concrete arch wall 340 is connected to the top of the reinforced concrete cross slab 20. Preferably, the reinforced concrete arch wall 340 is made of a 60-cm-thick reinforced concrete structure. As a preferred example, considering problems such as the impact of falling rocks in large karst caves and the local instability and collapse of karst cave surrounding rocks during the annual operation of the tunnel, the reinforced concrete arch wall 340 is made of a 60-cm-thick C35 reinforced concrete structure, which can better resist the impact of falling rocks and the collapse load of the surrounding rocks.

[0057] As a preferred example, the thickness of the reinforced concrete cross slab 20 is set between 0.8 m and 1.2 m.

[0058] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. A support structure across a tunnel cave, characterized in that: It includes the foundation platform, reinforced concrete span slab and protective scaffolding, among which: The basic platform includes a plurality of support units arranged transversely along the tunnel, each of the support units includes a first overlapping section and a second overlapping section arranged opposite to each other along its own extension direction, the first overlapping section overlaps the side of the tunnel cave close to the excavated tunnel section, and the second overlapping section overlaps the side of the tunnel cave away from the excavated tunnel section; The reinforced concrete cross-slab is arranged on the top of the basic platform, and the bottom end of the protection scaffold is connected to the top of the basic platform to resist the impact of falling rocks in the cave.

2. The supporting structure across a tunnel cave according to claim 1 is characterized in that: The protective scaffolding comprises an outer steel arch structure layer, an inner steel arch structure layer and an intermediate buffer layer between the outer steel arch structure layer and the inner steel arch structure layer, wherein: The outer steel arch structure layer includes a plurality of outer steel arches arranged at intervals along the extension direction of the foundation platform, a first double-layer steel mesh is hung between two adjacent outer steel arches, concrete is sprayed in the first double-layer steel mesh to form a first concrete spraying layer, and the outer steel arch is erected on the top of the foundation platform; The inner steel arch frame structure layer is arranged on the inner side of the outer steel arch frame structure layer and has an interlayer space between the inner steel arch frame structure layer and the outer steel arch frame structure layer, the inner steel arch frame structure layer includes a plurality of inner steel arch frames arranged at intervals along the extension direction of the foundation platform, a second double-layer steel mesh is hung between two adjacent inner steel arch frames, concrete is sprayed in the second double-layer steel mesh to form a second concrete spraying layer, and the inner steel arch frame is erected on the top of the foundation platform; The interlayer space is filled with sand to form the middle buffer layer.

3. The supporting structure across a tunnel cave according to claim 1 is characterized in that: The length of the first overlapping section and / or the second overlapping section is greater than 3 m.

4. The supporting structure across a tunnel cave according to claim 3 is characterized in that: The supporting unit is an I-beam.

5. The supporting structure across a tunnel cave according to claim 1, characterized in that: The reinforced concrete span slab comprises a first end and a second end opposite to each other along its extension direction, wherein the first end matches the first overlapping section, and the second end matches the second overlapping section.

6. The supporting structure across a tunnel cave according to claim 2, characterized in that: The protection scaffolding also includes a reinforced concrete arch wall arranged on the inner side of the inner steel arch structure layer, and the bottom of the reinforced concrete arch wall is connected to the top of the reinforced concrete span slab.

7. The supporting structure across a tunnel cave according to claim 6 is characterized in that: The thickness of the reinforced concrete span slab is set between 0.8m and 1.2m.

8. The supporting structure across a tunnel cave according to claim 6, characterized in that: The reinforced concrete arch wall adopts a 60cm thick reinforced concrete structure.

9. The supporting structure across a tunnel cave according to claim 2, characterized in that: The first double-layer steel mesh comprises a first steel mesh and a second steel mesh respectively arranged on both sides of the outer steel arch frame, the first steel mesh is connected to the outer side wall of the outer steel arch frame, the second steel mesh is connected to the inner side wall of the outer steel arch frame, and the spacing between the first steel mesh and the second steel mesh matches the thickness of the outer steel arch frame; The second double-layer steel mesh includes a third steel mesh and a fourth steel mesh respectively arranged on both sides of the inner steel arch frame, the third steel mesh is connected to the outer wall of the inner steel arch frame, and the fourth steel mesh is connected to the inner wall of the inner steel arch frame. The spacing distance between the third steel mesh and the fourth steel mesh matches the thickness of the inner steel arch frame.

10. The supporting structure across a tunnel cave according to claim 9, characterized in that: The mesh sizes of the first steel mesh and the second steel mesh are set to 5cm*5cm, and the mesh sizes of the third steel mesh and the fourth steel mesh are set to 10cm*10cm.

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