A tunnel waterproof curtain rubber plate adapting to construction error of a sudden structure

Abstract

The application provides a hole waterproof curtain rubber plate suitable for construction error of structure mutation, which comprises a curtain rubber plate fixed on the end wall of a working well and having a suspended end capable of being lifted by a bite pipe, and a sharp corner tail wing provided at a sharp corner position of the bite pipe at which two pipes of the bite pipe are overlapped, the sharp corner tail wing comprising an overlapping surface capable of being overlapped with the outer contour of the bite pipe after being lifted, and the surface shape of the overlapping surface is matched with the shape of the sharp corner of the bite pipe. The curtain rubber plate with the tail wing has corresponding ductility and wear resistance, the size of the tail wing meets the construction error requirement, and the wing corner can be pushed to the structure mutation position and fill the waterproof gap under the error working condition.

Description

Technical Field

[0001] This invention belongs to the field of tunnel engineering and can be applied to waterproofing the starting portal of shield tunnels and pipe jacking structures with abrupt changes in the external wall structure. Specifically, it relates to a waterproof curtain rubber sheet for the portal that adapts to construction errors caused by abrupt changes in the structure. Background Technology

[0002] With the continuous advancement of urbanization in my country, large-span shallow-buried tunnels are becoming increasingly common, especially those passing under railways, roads, subway stations, and other structures. This places increasingly higher demands on settlement control during tunnel construction. Therefore, a ring-shaped pre-excavation and advanced support cyclical tunnel construction method was proposed. This method employs multiple pipe jacking machines arranged circumferentially along the tunnel to excavate the tunnel's pre-support structure. The excavation contours of adjacent pipe jacking machine cutterheads overlap and interlock, jacking in an interlocking pipe body composed of interlocking steel pipes.

[0003] In the launching, arrival, and receiving stages of tunnel boring machines (TBMs) and pipe jacking machines, the use of rubber sheet curtains for water sealing is a commonly used technical method. (See attached image) Figure 1 As shown, the rubber sheet is arranged in a circular ring around the pre-embedded ring frame 2. One end is fixed to the ring plate 2-1 of the pre-embedded ring frame, and the other end is a free end. The inner diameter of the ring is smaller than the outer diameter of the jacking pipe or shield tunnel structure. (See attached diagram) Figure 2 As shown, the working principle of the rubber sheet 3 is that the tunnel boring machine, pipe jacking machine, or tunnel structure with both shield and pipe jacking passes through the rubber sheet, lifting it up and overlapping it on the outside of the structure. Then, the pressure of the mud or water in the excavation gap compresses the rubber sheet to the tunnel structure, forming contact compressive stress between it and the tunnel or pipe jacking. When the contact stress between the rubber sheet 3 and the tunnel structure is greater than the pressure of the mud or water in the excavation gap, the mud or water cannot flow out through the portal.

[0004] When this technology is applied to tunnel structures with conforming and continuous surfaces, it provides good waterproofing and meets the design and construction requirements. However, when the structure has sharp corners, the following problems arise:

[0005] 1. After the rubber sheet is lifted, it can overlap the tunnel structure, but it will bulge at the sharp corners of the structure, forming an arc-shaped angle. It cannot completely fit the sharp corners, becoming a point of origin and destination for leaks during construction. (See attached image.) Figure 3 As shown, there is still a gap 15 between the ordinary fabric rubber sheet and the outline of the interlocking pipe body, which is prone to water and mud flow, making it difficult for the interlocking jacking pipe to start and receive water stop.

[0006] 2. The cord rubber sheet is specially customized, but there are errors in the installation of the cord rubber sheet and errors in the construction of shield tunneling or pipe jacking, which leads to more serious leakage problems in actual applications. Summary of the Invention

[0007] The purpose of this invention is to overcome the defects of the prior art and provide a waterproof curtain rubber sheet for tunnel entrances that can adapt to construction errors caused by abrupt structural changes. This invention solves at least some of the problems in the prior art.

[0008] This invention is implemented as follows:

[0009] This invention provides a waterproof curtain rubber sheet for tunnel entrances that adapts to construction errors caused by abrupt structural changes. The sheet includes a curtain rubber sheet fixed to the end wall of the working shaft and whose suspended end can be lifted by the interlocking jacking pipe. The curtain rubber sheet has a pointed tail wing at the sharp corner where the two round pipes of the interlocking jacking pipe overlap. The pointed tail wing includes an overlapping surface that overlaps with the outer contour of the interlocking jacking pipe after being lifted. The surface shape of the overlapping surface fits the shape of the sharp corner where the two round pipes of the interlocking jacking pipe overlap.

[0010] Furthermore, the end wall includes the working well side wall and the portal. The pre-embedded ring frame includes a corrugated frame, an annular frame, and an annular plate set on the inner side wall of the working well. Both the corrugated frame and the annular frame are pre-embedded in the working well side wall. The annular frame is set on the side of the working well side wall closer to the working well, and the corrugated frame is set on the side of the working well side wall away from the working well. The diameter of the corrugated frame is smaller than the diameter of the annular frame. The portal is set in the area enclosed by the corrugated frame and the annular frame. The annular plate and the corrugated frame are both connected to the annular frame. The curtain rubber plate is fixed on the annular plate.

[0011] Furthermore, the ring plate is also equipped with a fixing plate and a flap that can be engaged and lifted by the jacking pipe along with the curtain rubber sheet. The curtain rubber sheet and the fixing plate are fixed to the ring plate by bolts. The bottom of the flap and the fixing plate are rotatably connected. The curtain rubber sheet is located between the working well side wall and the flap.

[0012] Furthermore, the flap includes several irregularly shaped flaps and several annular flaps. The irregularly shaped flaps are set at the pointed corners of the annular frame to adapt to the water-stopping requirements at the joint of the interlocking jacking pipe.

[0013] Furthermore, the pointed tail fin includes a pointed wing angle in the middle and wing surfaces on both sides. The wing surfaces are connected to the pointed wing angle, and the surface shape of the pointed wing angle and the wing surface facing the flap side fits the pointed wing shape of the two round tubes of the bite-type top tube overlapping.

[0014] Furthermore, the back of the pointed wing corner has a rounded shape.

[0015] The present invention has the following beneficial effects:

[0016] 1. The waterproof curtain rubber sheet for tunnel portals proposed in this invention adapts to construction errors caused by abrupt structural changes. By setting tail wings that fit the structural outline at the corresponding sharp corners of the curtain rubber sheet, the shape of the contact surface between the curtain rubber sheet and the tunnel / jacking pipe corresponds to the structural outline. This allows the curtain rubber sheet to fit into the abrupt structure through the tail wings and be pressed tightly against the tunnel structure under the action of mud pressure in the excavation gap. This solves the problem of starting and reaching the construction waterproofing at the sharp corners formed when adjacent jacking pipes overlap.

[0017] 2. The cord rubber sheet with tail fin proposed in this invention has corresponding ductility and wear resistance. The tail fin size meets the construction error requirements. Under error conditions, as the rubber sheet extends, the fin angle is pushed to the position of structural change and fills the waterproof gap to ensure that the fin angle and fin surface can fit the structural shape within a certain error range. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram showing the layout of the curtain, fabric rubber sheet, and related waterproofing devices (taking initial waterproofing as an example);

[0020] Figure 2 This is a cross-sectional schematic diagram illustrating the working principle of the rubber sheet curtain (taking initial waterproofing as an example);

[0021] Figure 3 Addressing the waterproofing issue at sharp corners of existing fabric rubber sheets;

[0022] Figure 4 for Figure 3 A magnified view of a portion of the image;

[0023] Figure 5 This is a schematic cross-sectional view of the arrangement of the interlocking jacking pipe starting end ring frame and the curtain rubber plate provided in an embodiment of the present invention;

[0024] Figure 6 Provided for embodiments of the present invention Figure 5 A magnified view of a portion of the image;

[0025] Figure 7 A front view of the arrangement of the interlocking jacking pipe initiation end ring frame and the curtain rubber plate provided in an embodiment of the present invention;

[0026] Figure 8 Provided for embodiments of the present invention Figure 7 Enlarged view on the left;

[0027] Figure 9 Provided for embodiments of the present invention Figure 7 Enlarged view on the right;

[0028] Figure 10 Provided for embodiments of the present invention Figure 7 Cross-sectional view of the mid-point tail fin (AA);

[0029] Figure 11 A schematic diagram of the installation error of the rubber sheet for the curtain fabric provided in the embodiment of the present invention (the arrow indicates the direction of the wing angle extension).

[0030] In the diagram: 1-1 working shaft sidewall, 1-2 tunnel portal, 2-2 embedded ring frame, 2-1 ring plate, 2-2 ring frame, 2-3 corrugated frame, 3 rubber sheet, 4 irregular flap, 5 fan-shaped ring flap, 6 pointed tail wing, 6-1 pointed wing angle, 6-2 wing surface, 8 outer contour of interlocking jacking pipe, 9 bolt, 10 bolt axis, 11 outer contour of jacking pipe structure, 12 flap, 13 inner contour of rubber sheet, r1 inner diameter of rubber sheet, r2 inner diameter of flap, r3 outer diameter of tunnel structure, 14 excavation direction, 15 gap, 16 grouting pipe, 17 pin, 18 tightening direction, 19 outer contour of shield or jacking pipe structure, 21 interlocking jacking pipe wall, 22 protruding foot of embedded ring frame structure, 23 concave angle of interlocking jacking pipe structure, 25 shape of the back of pointed wing angle. Detailed Implementation

[0031] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0032] In the description of this invention, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0034] like Figures 5-11This invention provides a waterproof rubber sheet for tunnel entrances that adapts to construction errors caused by abrupt structural changes. The sheet includes a rubber sheet 3 fixed to the end wall of the working shaft, with its suspended end capable of being lifted by an interlocking jacking pipe. The rubber sheet 3 has a pointed tail wing 6 at the sharp corner where the two circular pipes of the interlocking jacking pipe overlap. The pointed tail wing 6 includes an overlapping surface that overlaps with the outer contour 8 of the interlocking jacking pipe after being lifted, and the surface shape of the overlapping surface conforms to the shape of the sharp corner where the two circular pipes overlap. A gap 15 is located at the sharp corner where the two circular pipes overlap, and the pointed tail wing 6 can effectively fill the gap 15, preventing water and mud inrush. The interlocking jacking pipe includes an interlocking jacking pipe body and a guide pipe.

[0035] The end wall includes the working shaft side wall 1-1 and the portal 1-2. The pre-embedded ring frame 2 includes a corrugated frame 2-3, an annular frame 2-2, and an annular plate 2-1 set on the inner side wall of the working shaft. Both the corrugated frame 2-3 and the annular frame 2-2 are pre-embedded in the working shaft side wall 1-1. The annular frame 2-2 is set on the side of the working shaft side wall 1-1 close to the working shaft, and the corrugated frame 2-3 is set on the side of the working shaft side wall 1-1 away from the working shaft. The diameter of the corrugated frame 2-3 is smaller than the diameter of the annular frame 2-2. The circumferential contour of the corrugated frame 2-3 is approximately the same as the outer contour 8 of the interlocking jacking pipe. The portal 1-2 is set in the area enclosed by the corrugated frame 2-3 and the annular frame 2-2. The annular plate 2-1 and the corrugated frame 2-3 are both connected to the annular frame 2-2. The curtain rubber plate 3 is fixed on the annular plate 2-1.

[0036] The ring plate 2-1 is also equipped with a fixing plate and a flap that can be lifted up by the interlocking jacking pipe along with the curtain rubber plate 3. The curtain rubber plate 3 and the fixing plate are fixed to the ring plate 2-1 by bolts 9. The flap is rotatably connected to the fixing plate by pins. The curtain rubber plate 3 is located between the working well side wall 1-1 and the flap. The flap includes several irregular flaps 4 and several fan-shaped flaps 5. The irregular flaps 4 are set at the pointed corners of the ring frame 2-2 to adapt to the water-stopping requirements at the interlocking point of the jacking pipe. Fan-shaped flaps 5 are set at other positions of the ring frame 2-2. At the same pipe end, each fan-shaped flap 5 has the same shape and size.

[0037] In this embodiment, the pointed tail fin 6 includes a central pointed fin angle 6-1 and two side fin surfaces 6-2. The fin surfaces 6-2 are connected to the pointed fin angle 6-1. The surface shapes of the pointed fin angle 6-1 and the fin surfaces 6-2 facing the flap plate conform to the pointed fin shape of the overlapping two round tubes of the interlocking top tube. The back surface of the pointed fin angle is rounded 25° to accommodate the deformation requirements of the curtain rubber sheet.

[0038] As attached Figure 11 As shown, when there is an installation error between the cord rubber sheet 3 and the outer contour 8 of the interlocking jacking pipe, since both the cord rubber sheet 3 and the pointed tail wing 6 have extensibility, under the action of mud pressure in the excavation gap, as the wing surface 6-2 swings and extends, the pointed wing angle 6-1 is pushed along the structural contour to the structural sharp corner or abrupt change position.

[0039] This invention proposes a waterproof rubber curtain sheet for tunnel entrances that adapts to construction errors caused by abrupt structural changes. It effectively solves the problem of ordinary rubber curtain sheets failing to fit snugly against the contours of interlocking jacking pipes, ensuring effective waterproofing of the tunnel entrance and significantly reducing construction risks. With the widespread use of interlocking jacking pipes, the waterproof rubber curtain sheet structure for tunnel entrances proposed in this invention has broad development prospects.

[0040] This invention proposes a waterproof rubber sheet structure for tunnel entrances that adapts to construction errors caused by abrupt structural changes. Its purpose is to solve the problem that existing waterproof rubber sheets cannot fully adhere to the outer wall of the structure at sharp corners or under conditions of installation or construction errors. The specific technical solution is as follows:

[0041] A waterproof curtain rubber sheet for tunnel portals that adapts to construction errors caused by sudden structural changes can be used for temporary water stoppage at the starting and receiving tunnel portals of the jacking pipe. The following explanation uses the starting end as an example.

[0042] During the jacking process of the interlocking jacking pipe assembly, the pilot guides at both ends of the assembly must be jacked in first, followed by the guide pipes and the jacking pipe body. The guide pipes are located at both ends of the jacking pipe body, i.e., at the positions of the pilot guides, and are jacked in along the trajectory of the pilot guides, while simultaneously pushing out sections of the pilot guides. To accommodate construction errors in the pilot guides at both ends, the subsequent jacking pipe structure must have a joint with at least one end of the guide pipes on both sides, meaning there must be a certain gap between the subsequent jacking pipe structure and the guide pipes to allow for relative displacement.

[0043] As attached Figure 5 As shown, the starting end wall includes the working shaft side wall 1-1 and the portal 1-2, with the portal diameter slightly larger than the outer diameter of the interlocking jacking pipe structure. The pre-embedded ring frame 2 is pre-embedded between the working shaft side wall 1-1 and the portal 1-2 during the construction of the main structure of the working shaft. For interlocking jacking pipes, since construction requires first jacking in the pilot pipe, then jacking in the interlocking jacking pipe body and guide pipe, and the guide pipe is located at the pilot pipe position, jacking along the trajectory of the pilot pipe, the pilot pipe position needs to be jacked multiple times. The types of jacking pipes include individual round pipes and interlocking round pipes. Therefore, multiple ring frames and corresponding curtain rubber sheet waterproof structures need to be set at the start of the interlocking jacking pipe to adapt to the requirements of different jacking pipe structures. Therefore, the pre-embedded ring frame 2 includes a ring plate 2-1, an annular frame 2-2, and a corrugated frame 2-3 on the inner surface of the starting end wall, wherein there is a certain gap between the annular frame 2-2 and the corrugated frame 2-3. When viewed along the direction of advancement of the starting end of the jacking pipe, the corrugated frame 2-3 is located in front of the annular frame 2-2.

[0044] Both the annular frame 2-2 and the corrugated frame 2-3 can be equipped with curtain rubber sheets and flaps, etc., to stop the water in the opening. Here, the curtain rubber sheet structure on the annular frame 2-2 is used as an example for explanation.

[0045] As attached Figure 7 As shown, the following explanation uses a three-pipe interlocking jacking pipe as an example. The annular frame 2-2 is connected and fixed to the annular plate 2-1 on the inner wall of the starting end wall. The curtain rubber plate 3 and the flap are fixed to the annular plate 2-1 by bolts. The flap includes an irregular flap 4 and a fan-shaped annular flap 5. The irregular flap 4 is set at the pointed corner of the annular frame 2-2 to adapt to the water-stopping requirements at the interlocking joint of the jacking pipe structure. The size of each irregular flap 4 is determined according to the size of the interlocking jacking pipe structure and the overlap requirements.

[0046] As attached Figure 7 As shown, the inner diameter of the rubber sheet 3 is smaller than the outer diameter of the interlocking jacking pipe structure to meet the requirement of the overlap length after the jacking pipe is pushed in. Its inner contour is basically corresponding to the inner contour of the interlocking jacking pipe, except that a pointed tail wing 6 is set at the pointed corner of the interlocking jacking pipe.

[0047] As attached Figure 10 As shown, the pointed tail fin 6 is located at the pointed corner where the two circular tubes of the interlocking jacking pipe overlap; it consists of a pointed fin 6-1 in the middle and two fin surfaces 6-2 on both sides; the shape of the flap side surface of the pointed fin 6-1 and the fin surface 6-2 fits the shape of the pointed corner of the interlocking jacking pipe structure; the thickness and size of the pointed fin 6-1 are determined according to factors such as the gap between the ring frame and the jacking pipe structure and the size of the curtain rubber sheet, and the shape of the back of the fin is rounded to adapt to the deformation requirements of the curtain rubber sheet; the thickness of the fin surface 6-2 is determined according to the material properties, and the length needs to meet the dimensional requirements of installation error and construction error.

[0048] The rubber sheet 3, the irregular flap 4, and the fan-shaped flap 5 are all set along the direction of the plumb bob. Before the interlocking jacking pipe is advanced, the flaps and the rubber sheet are not deformed, and the pointed tail wing 6 faces the inside of the working shaft. After the interlocking jacking pipe is advanced, the rubber sheet 3, the irregular flap 4, and the fan-shaped flap 5 are all bent in the direction of advancement, and the pointed tail wing 6 faces the side of the jacking pipe structure. Under the action of the mud pressure in the jacking pipe excavation gap, it is tightly attached to the jacking pipe structure. The pointed wing 6-1 fills the gap at the pointed corner of the jacking pipe structure and plays a role in water stop.

[0049] The waterproof curtain rubber sheet for tunnel entrance proposed in this invention mainly includes a flap or clamping plate, a regular curtain rubber sheet, and a pointed tail wing corresponding to the sharp corner position of the interlocking jacking pipe.

[0050] Before the construction of interlocking pipe jacking, it is necessary to customize the cord rubber sheet in advance according to the shape and size of the interlocking pipe and its pre-embedded ring frame, the gap between the ring frame and the cutter head of the pipe jacking machine and the structural outline, the external water pressure, the mud pressure, the water-stopping requirements, and other conditions. Ordinary cord rubber sheets are used in the smooth parts of the structure, and cord rubber sheets with tail wings are used in the sharp corners of the structure.

[0051] The rubber sheet of the curtain needs to be closed into a ring in the horizontal direction. It can be installed alone, in multiple layers, or in combination with other water-stopping structures. The installation position should be as accurate as possible.

[0052] Before the interlocking jacking pipe is advanced, the flap and the rubber curtain are not deformed, and the tail wing of the rubber curtain faces the inside of the working shaft. After the interlocking jacking pipe is advanced, the rubber curtain and the flap are bent in the direction of advancement, and the tail wing faces the side of the jacking pipe structure. Under the action of mud pressure in the jacking pipe excavation gap, they are closely attached to the jacking pipe structure. The wing corners fill the gaps at the sharp corners of the jacking pipe structure and play a role in water stop.

[0053] When a large swing amplitude of the tail fin of the cord rubber sheet is required, or when the sharp corner structure is complex, or when the jacking pipe structure needs to be advanced under the pressure of the rubber bladder, the friction of the contact surface can be reduced by applying oil to the surface of the cord rubber sheet, which facilitates the extension and deformation of the tail fin and wing corner of the cord rubber sheet.

[0054] The above description is merely a description of the basic principles of the present invention and does not impose any specific shape, size, arrangement, excavation method, or material limitations on the structure of the present invention. Therefore, all possible modifications and equivalents are within the scope of the patent application of the present invention.

[0055] This invention proposes a waterproof rubber curtain sheet for tunnel portals that adapts to construction errors caused by abrupt structural changes. The rubber curtain sheet is continuously arranged along the outer edge of the structure. The shape of the rubber curtain sheet at the contact points with the protrusions or grooves on the outer edge of the structure is adjusted to correspond with the structure's shape, ensuring that the rubber curtain sheet fits the outer edge of the structure as closely as possible. Tail wings are provided at the contact points of the rubber curtain sheet with the protrusions or grooves on the outer edge of the structure. The length of the tail wings should be able to accommodate the requirements of tunnel or pipe jacking construction errors. The contact surface between the tail wings and the structure should adapt to structural changes and meet the requirements for tensile stress caused by longitudinal friction. Wing surfaces connected to the rubber curtain sheet are provided on both sides of the tail wings, and the width of the wing surfaces is sufficient to accommodate tunnel construction errors after the tail wings swing.

[0056] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A waterproof curtain rubber sheet for tunnel entrances that adapts to construction errors caused by abrupt structural changes, characterized in that: It includes a curtain rubber sheet fixed to the end wall of the working well and whose suspended end can be lifted by the interlocking jacking pipe. The curtain rubber sheet has a pointed tail wing at the sharp corner position where the two round pipes of the interlocking jacking pipe overlap. The pointed tail wing includes an overlapping surface that overlaps with the outer contour of the interlocking jacking pipe after being lifted. The surface shape of the overlapping surface fits the shape of the sharp corner where the two round pipes of the interlocking jacking pipe overlap. The end wall includes the working well side wall and the portal. The pre-embedded ring frame includes a corrugated frame, an annular frame, and an annular plate set on the inner side wall of the working well. Both the corrugated frame and the annular frame are pre-embedded in the working well side wall. The annular frame is set on the side of the working well side wall closer to the working well, and the corrugated frame is set on the side of the working well side wall away from the working well. The diameter of the corrugated frame is smaller than the diameter of the annular frame. The portal is set in the area enclosed by the corrugated frame and the annular frame. The annular plate and the corrugated frame are both connected to the annular frame. The curtain rubber plate is fixed on the annular plate. The ring plate is also equipped with a fixing plate and a flap that can be lifted up by the jacking pipe along with the curtain rubber sheet. The curtain rubber sheet and the fixing plate are fixed to the ring plate by bolts. The bottom of the flap and the fixing plate can be rotatably connected. The curtain rubber sheet is located between the working well side wall and the flap. The flap includes several irregularly shaped flaps and several annular flaps. The irregularly shaped flaps are set at the pointed corners of the annular frame to adapt to the water-stopping requirements at the joint of the interlocking jacking pipe. The pointed tail fin includes a pointed wing angle in the middle and wing surfaces on both sides. The wing surfaces are connected to the pointed wing angle. The surface shape of the pointed wing angle and the wing surfaces facing the flap side fits the pointed wing shape of the two round tubes of the interlocking top tube.

2. The waterproof curtain rubber sheet for the tunnel entrance as described in claim 1, characterized in that: The back of the pointed wing corner has a smooth, rounded shape.

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