A construction method suitable for back-digging and dismantling of pipe segments in situ test of ventilation shaft

Abstract

The invention discloses a construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts, which comprises the following steps: S1, soil removal of tunnel vault; S2, tunnel door blocking; S3, pipe segment removal; S4, construction of tunnel ring beam and shaft structure. The invention realizes reverse excavation of pipe segments under the premise of ensuring the reliability of tunnel structure connection, can effectively prevent the deformation of shield tunnel settlement, floating and left and right movement from causing instability and damage of pipe segment structure, ensure the integrity of pipe segments, and stabilize surrounding strata.

Description

Technical Field

[0001] The invention belongs to the technical field of shield tunnel construction, and in particular relates to a construction method suitable for reverse excavation and removal of in-situ test pipe segments of a ventilation shaft. Background Art

[0002] In recent years, with the continuous advancement of national development strategies and infrastructure construction, and the further improvement of high-speed railway networks, highway networks, and urban road network structures, shield tunnel technology has become an indispensable key technology in the construction of major transportation and other infrastructure in my country.

[0003] However, due to the limitation of underground space, it is difficult for large lifting machinery to enter the shield construction space and carry out related operations. At the same time, the removal of the shield tunnel segments is very difficult and has a low safety factor. Therefore, after the shield passes through the wind shaft, the wind shaft in-situ test segment back-excavation construction is carried out, which has the following risks:

[0004] 1) It is difficult to seal the deep buried tunnel and the interval ventilation shaft. The main reason is that water leakage is easy to occur during the removal of the pipe segments, and in severe cases, there is the possibility of sudden water inrush;

[0005] 2) The removal of the segments is likely to cause deformation of the tunnel. The main reason is that after the segments are removed, the tight longitudinal arrangement of the segments is broken, and the prefabricated structure tends to relax, which can easily cause overall deformation of the tunnel.

[0006] 3) The integrity of the segment structure is easily damaged. The main reason is that during the demolition process, the tunnel is easily caused to sink, float, and move left and right, causing the segment structure to become unstable and damaged;

[0007] 4) Affecting the stability of the surrounding strata. The main reason is that the pipe segments are displaced and deformed during the demolition process, and the pipe segments settle, which can easily cause the surrounding soil to loosen, deform, and collapse.

[0008] Therefore, with the increasing amount of shield tunnel construction, the effect of segment removal operation will directly affect the quality of shield tunnel construction. Therefore, how to safely and efficiently remove the segments in the narrow space of the interval ventilation shaft has become an issue that needs to be studied and solved urgently. Summary of the invention

[0009] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide an improved construction method suitable for back-digging and dismantling of pipe segments for in-situ testing of ventilation shafts.

[0010] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows: a construction method suitable for back-digging and dismantling of in-situ test pipe segments of a ventilation shaft, which comprises the following steps:

[0011] S1. Soil removal from tunnel vault

[0012] When the soil is excavated to the position of 2±0.5m from the tunnel vault, protective excavation is carried out until the synchronous grouting body of the tunnel vault between the left and right openings is exposed, wherein multiple hole rings are formed between the two openings, each of which is assembled from multiple arc-shaped segments, and the hole ring formed at the opening is the opening ring;

[0013] S2. Tunnel Gate Blockage

[0014] a) Excavate from the tunnel opening ring, remove the synchronous grouting inclusions on the arch, and simultaneously weld the tunnel door sealing plate and the tunnel opening ring backing steel plate to remove part of the blockage; b) Gradually excavate the soil on both sides of the tunnel opening ring, remove the synchronous grouting inclusions on both sides of the tunnel opening ring, and simultaneously weld the tunnel door sealing plate and the tunnel opening ring backing steel plate, and at the same time, add temporary supports one by one on the pipe segment where the tunnel opening ring is located; c) Until the soil on both sides of the pipe segment at the tunnel opening ring is excavated to the top surface of the plain concrete, the plain concrete and synchronous grouting inclusions at the tunnel opening rings at both ends are removed, and the steel plates are synchronously welded to complete the blockage of the tunnel door;

[0015] S3. Segment removal

[0016] First, break the top pipe segment of the middle hole ring between the two hole rings, and then remove the pipe segments along the arc surface of the hole ring segment to the hole rings on both sides in sequence until the upper semicircular pipe segments between the two hole rings are removed, and then gradually remove the lower semicircular pipe segments until the pipe segments of the hole rings in the well are removed;

[0017] S4, construction tunnel ring beam and shaft structure.

[0018] Preferably, in step S2 b), the temporary support includes an outer support frame and an inner support frame respectively arranged on the outer side and inner side of the segment corresponding to the hole ring. Through the inner and outer supports, the tight longitudinal arrangement of the segments is prevented from being broken during the back-excavation construction, and the overall deformation of the tunnel is prevented. At the same time, the probability of the segment structure being unstable and damaged due to tunnel settlement, floating and left-right movement deformation is also reduced.

[0019] According to a specific implementation and preferred aspect of the present invention, the external support frame includes a plurality of external support rods located on both sides of the tunnel vault, wherein the external support rods are horizontally supported between the pipe segments and the inner wall of the wind shaft at the hole ring in a direction perpendicular to the centerline of the hole ring, and are spaced from the tunnel vault to the bottom in sequence. In this way, the probability of tunnel settlement, floating and left-right movement deformation is reduced by the mode of digging out and supporting at the same time.

[0020] Preferably, the multiple external support rods on both sides are symmetrically arranged about the tunnel vault, or the multiple external support rods on both sides are spaced up and down and staggered. Here, the layout of the external support rods can not only reduce the probability of tunnel settlement, floating and left and right movement deformation, but also effectively locate the tunnel opening during plugging, and can also prevent the tight longitudinal arrangement of the segments from being broken during segment removal.

[0021] Furthermore, the plurality of external support rods include a top support rod, a bottom support rod and a middle support rod, and the length formed by the top support rod and the middle support rod gradually decreases from top to bottom, and the length formed by the middle support rod and the bottom support rod gradually increases from middle to bottom, wherein the length of the top support rod is greater than that of the bottom support rod, and the bottom support rod is located between the lower semicircle of the tunnel and the top surface of the plain concrete. Here, the position of the external support rod is also very important. Too many are inconvenient for construction, and it should not be too high or too low.

[0022] In this example, there is one middle support rod and it extends radially along the hole ring. The length of the top support rod is greater than that of the bottom support rod. The distance between the top support rod and the top surface of the hole ring is 3 / 5~7 / 10 of the hole ring radius. The bottom support rod is between the lower semicircle of the tunnel and the top surface of the plain concrete, and the distance between the bottom support rod and the top surface of the hole ring is 1.2~1.4 times the hole ring radius. In this way, when the side soil is removed accurately, the layout of the external support rods is set up so that it is in a specific position to avoid the probability of tunnel settlement, floating and left-right movement deformation, and it is also convenient for the removal of the pipe segment.

[0023] Preferably, the inner support frame comprises a plurality of inner support rods located in the hole ring from which the synchronous grouting inclusion has been removed, wherein the support rods are arranged in parallel and / or intersecting.

[0024] In this case, temporary support for the segments includes tensioning by welding I-beams on both sides of the segments (forming an external support frame) and horizontal and vertical steel supports inside the segments (forming an internal support frame).

[0025] According to another specific implementation and preferred aspect of the present invention, when removing the pipe segments in step S3, the top pipe segment of the middle hole ring is removed by cutting tools and lifting tools, and then the pipe segment on the middle hole ring is removed, and then the pipe segment is removed from the removal gap to the left or right to the hole ring in sequence, until the upper semicircular pipe segment between the two hole rings is completely removed. The best removal method, combined with temporary support, can achieve the best removal effect: 1. It is not easy to cause tunnel deformation during the removal of the pipe segment; 2. The integrity of the pipe segment structure is not easily damaged; 3. It will not affect the stability of the surrounding strata.

[0026] Preferably, the removal process of the lower semicircular segment and the upper semicircular segment between the two opening rings is the same. Therefore, the effect of the segment removal operation will not affect the construction quality of the shield tunnel.

[0027] Preferably, the seepage gaps in the pipe segments need to be sealed before back-digging construction, and the soil at the bottom of the pipe segments needs to be grouted through the grouting holes at the bottom of the pipe segments. Grouting the soil around the pipe segments before excavation can effectively control the displacement and deformation of the pipe segments and the settlement of the pipe segments, while increasing the water-stopping effect of the soil outside the pipe segments, greatly reducing the disturbance to the surrounding strata.

[0028] In addition, the tunnel door needs to be continuously sealed during the excavation process, and the open water in the air shaft and / or tunnel is pumped out during the back-excavation construction. The tunnel door has a good sealing effect and no water leakage.

[0029] Due to the implementation of the above technical solution, the present invention has the following advantages compared with the prior art:

[0030] The present invention realizes the reverse excavation construction of the pipe segment under the premise of ensuring the reliability of the tunnel structure connection, which can effectively prevent the deformation of the shield tunnel such as settlement, floating and left and right movement from causing instability and damage of the pipe segment structure, ensure the integrity of the pipe segment, and stabilize the surrounding strata. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the main view of the construction method for reverse excavation and removal of pipe segments for in-situ test of ventilation shafts in this embodiment (with synchronous grouting body exposed);

[0032] Figure 2 for Figure 1 The schematic cross-sectional view from the hole ring in the middle;

[0033] Figure 3 The main schematic diagram of the construction method for reverse excavation and removal of pipe segments for in-situ test of the ventilation shaft in this embodiment (when excavating from the ring of the hole opening)

[0034] Figure 4 for Figure 3 The schematic cross-sectional view from the hole ring in the middle;

[0035] Figure 5 Schematic diagram of the main view of the construction method for reverse excavation and removal of pipe segments for in-situ testing of a ventilation shaft according to this embodiment (when removing the soil on both sides of the hole ring);

[0036] Figure 6 for Figure 5 The schematic cross-sectional view from the hole ring in the middle;

[0037] Figure 7 This is a schematic diagram of the main view of the construction method for reverse excavation and removal of pipe segments for in-situ testing of a ventilation shaft in this embodiment (when the soil on both sides of the hole ring is excavated to the lower semicircular pipe segment);

[0038] Figure 8 for Figure 7 The schematic cross-sectional view from the hole ring in the middle;

[0039] Fig. 9 This is a schematic diagram of the main view of the construction method for reverse excavation and removal of pipe segments for in-situ testing of a ventilation shaft in this embodiment (when the soil on both sides is excavated to the top surface of the plain concrete);

[0040] Fig.10 for Fig. 9 The schematic cross-sectional view from the hole ring in the middle;

[0041] Fig.11 This is a schematic diagram of the main view of the construction method for reverse excavation and removal of pipe segments for in-situ testing of a ventilation shaft in this embodiment (when the top pipe segment of the middle hole ring is used);

[0042] Fig.12 for Fig.11 Schematic diagram of removing the pipe segments in a circle along the arc surface toward the openings on both sides;

[0043] Fig.13 for Fig.11 Schematic diagram after the middle and upper semicircular tube segments are removed;

[0044] Fig.14 for Fig.11 Schematic diagram of the pipe segments of the inner hole ring of the middle well after removal;

[0045] Fig.15 This is a schematic diagram of the main view of the construction method for reverse excavation and removal of pipe segments for in-situ testing of a ventilation shaft in this embodiment (when constructing a ring beam of a tunnel ring);

[0046] Fig.16 for Fig.15 The main schematic diagram of the completed construction of the tunnel ring beam and the shaft structure;

[0047] Fig.17 for Fig.16 The middle part is a schematic cross-sectional view of the hole ring;

[0048] Fig.18 for Fig.17 Schematic diagram of partial structure section;

[0049] Among them: F, ventilation shaft; S, tunnel; 1, tunnel vault; 2, synchronous grouting body; 3a, opening ring; 3b, opening ring; 30a, pipe segment; 4, temporary support; 4a, top support rod; 4b, middle support rod; 4c, bottom support rod; m, plain concrete top surface; 5, L-shaped steel bar; 6, side wall; 7, ring steel bar; 8, ring end covering steel plate. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0051] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0052] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0053] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0054] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0055] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0056] Combination Figures 1 to 16 As shown, the construction method of this embodiment is applicable to the reverse excavation and removal of the in-situ test pipe segment of the ventilation shaft, which includes the following steps:

[0057] S1. Soil removal from tunnel vault

[0058] When the soil is excavated to the position of 2±0.1m from the tunnel vault, protective excavation is performed until the synchronous grouting body 2 of the tunnel vault 1 between the left and right openings is exposed, wherein a plurality of hole rings 3b are formed between the two openings, each hole ring 3b is assembled from a plurality of arc-shaped segments, and the hole ring 3a is formed at the opening;

[0059] S2. Tunnel Gate Blockage

[0060] a) Excavate from the hole ring 3a respectively, remove the synchronous grouting 2 inclusions on the arch, and synchronously weld the hole door sealing plate and the hole ring backing steel plate to remove part of the blockage; b) Gradually excavate the soil on both sides of the hole ring 3a, remove the synchronous grouting inclusions on both sides of the hole ring, and synchronously weld the hole door sealing plate and the hole ring backing steel plate, and at the same time, gradually add temporary supports 4 on the pipe segment where the hole ring is located; c) Until the soil on both sides of the pipe segment at the hole ring is excavated to the top surface of the plain concrete, remove the plain concrete and synchronous grouting inclusions at the hole rings at both ends, and synchronously weld the steel plates to complete the complete blockage of the hole door;

[0061] S3. Segment removal

[0062] First, break the top pipe segment of the middle hole ring between the two hole rings, and then remove the pipe segments along the arc surface of the hole ring segment to the hole rings on both sides in sequence until the upper semicircular pipe segments between the two hole rings are removed, and then gradually remove the lower semicircular pipe segments until the pipe segments of the hole rings in the well are removed;

[0063] S4, construction tunnel ring beam and shaft structure.

[0064] In order to facilitate implementation, before back-excavation construction, the water seepage gaps in the pipe segments need to be sealed, and the drainage of open water in the air shaft and air duct needs to be strengthened. At the same time, grouting is also required for the soil at the bottom of the pipe segments through the grouting holes at the bottom of the pipe segments.

[0065] Specifically, the temporary support 4 includes an outer support frame and an inner support frame respectively arranged on the outer side and inner side of the segment corresponding to the hole ring. Through the inner and outer supports, the tight longitudinal arrangement of the segments is prevented from being broken during the back-excavation construction, and the overall deformation of the tunnel is prevented. At the same time, the probability of the segment structure being unstable and damaged due to tunnel settlement, floating and left-right movement deformation is also reduced.

[0066] The external support frame includes multiple external support rods located on both sides of the tunnel vault, wherein the external support rods are horizontally supported between the pipe segment and the inner wall of the wind shaft at the hole ring 3a in a direction perpendicular to the center line of the hole ring, and are spaced from the tunnel vault 1 to the bottom. In this way, the probability of tunnel settlement, floating and left-right movement deformation is reduced by the mode of digging out and supporting at the same time.

[0067] In this example, multiple external support rods on both sides are symmetrically arranged about the tunnel vault. Here, the main function of the external support rod layout is not only to reduce the probability of tunnel settlement, floating and left-right movement deformation, but also to effectively locate the tunnel opening during blockage, and to prevent the tight longitudinal arrangement of the segments from being broken during segment removal.

[0068] The multiple outer braces include a top brace 4a, a bottom brace 4c and a middle brace 4b, and the length formed by the top brace 4a and the middle brace 4b gradually decreases from top to bottom, and the length formed by the middle brace 4b and the bottom brace 4c gradually increases from the middle to bottom, wherein the length of the top brace is greater than that of the bottom brace, and the bottom brace is located between the lower semicircle of the tunnel and the top surface of the plain concrete. Here, the position of the outer brace is also very important. Too many are inconvenient for construction, and it is not suitable to be too high or too low.

[0069] In this example, there is one middle support rod 4b and it extends radially along the hole ring 3a. The length of the top support rod 4a is greater than that of the bottom support rod. The bottom support rod 4c is located between the lower semicircle of the tunnel and the top surface m of the plain concrete.

[0070] Specifically, the radius of the tunnel opening ring is 7.7m, the distance between the top support rod and the top surface of the tunnel opening ring is 4.9m, and the distance between the bottom support rod and the top surface of the tunnel opening ring is 10m. In this way, when the side soil is removed accurately, the layout of the external support rods can be set up so that they are in a specific position to avoid the probability of tunnel settlement, floating and left and right movement deformation, and it is also convenient for the removal of the pipe segments.

[0071] The inner support frame comprises a plurality of inner support rods located in the hole ring from which the synchronous grouting inclusion has been removed, wherein the support rods are arranged in parallel or / and intersecting, that is, as long as a certain top support can be formed inside.

[0072] In this case, temporary support for the segments includes tensioning by welding I-beams on both sides of the segments (forming an external support frame) and horizontal and vertical steel supports inside the segments (forming an internal support frame).

[0073] Combination Fig.17 and 18 As shown, the construction of the tunnel ring beam and the shaft structure includes the tunnel ring beam construction process and the shaft structure construction process, wherein the tunnel ring beam construction process: one end of the L-shaped steel bar 5 is embedded in the side wall 6, and the other end is welded to the tunnel ring back covering steel plate or the ring end covering steel plate 8, and the annular steel bar 7 is inserted to form a steel skeleton; the tunnel ring beam is formed by supporting the formwork and pouring concrete, and the pipe segment 30a of the tunnel ring 3a is connected to the wind shaft structure as a whole.

[0074] The construction process of the shaft structure is as follows: formwork is set up inside the shaft, and steel bars are tied and concrete is poured from bottom to top to form the shaft structure.

[0075] In summary, the implementation process of this embodiment is as follows:

[0076] 1) Before back-digging construction, the water seepage gaps in the pipe segments need to be sealed, and the drainage of open water in the air shaft and tunnel needs to be strengthened. At the same time, grouting of the soil at the bottom of the pipe segments needs to be carried out through the grouting holes at the bottom of the pipe segments;

[0077] 2) If Figure 1 and Figure 2 As shown, the soil is excavated to the position 2m above the tunnel vault, and protective excavation is carried out until the synchronous grouting body is completely exposed;

[0078] 3) If Figure 3 and Figure 4 As shown, excavation is carried out at the left and right end opening rings 3, the synchronous grouting inclusions of the arch are chiseled out, and the tunnel door sealing plate and the back-covering steel plate of the tunnel opening ring are synchronously welded to seal the tunnel door;

[0079] 4) If Figure 5 and Figure 6 As shown in the figure, the soil on both sides of the segment is gradually excavated, the synchronous grouting inclusions at both ends are chiseled out, the tunnel cover plate and the tunnel opening ring backing steel plate are welded synchronously, and temporary support is added to the segment (the temporary support of the segment includes the use of I-beam welding on both sides of the segment for tensioning and the use of horizontal and vertical steel support inside the segment), so that the tunnel is continuously blocked and the open water in the air shaft is pumped out;

[0080] 5) If Figure 7 and Figure 8As shown, the soil on both sides of the segment is gradually excavated to the lower semicircle position, the synchronous grouting inclusions at both ends are chiseled out, the tunnel cover plate and the tunnel opening ring backing steel plate are welded synchronously, and temporary support is added to the segment (the temporary support of the segment includes the use of I-beam welding on both sides of the segment for tensioning and the use of horizontal and vertical steel support inside the segment), that is, the relative connection of the top support rod, the middle support rod and the bottom support rod is completed in sequence;

[0081] 6) If Fig. 9 and Fig.10 As shown, the soil on both sides of the segment is gradually excavated to the top surface of the plain concrete, the plain concrete and synchronous grouting inclusions at the hole rings at both ends are chiseled out, and the steel plates are welded synchronously to seal the tunnel door. The tunnel door sealing is completed;

[0082] 7) If Figures 11 to 14 As shown, the K block on the top of the middle ring is manually broken (the K block of the pipe segment is cut by a water drill, and the crane is used to tighten it to complete the cutting and removal), and the pipe segments are removed from the K block on the top of the middle ring along the arc surface to both sides in sequence until all the upper semicircular pipe segments are removed;

[0083] 8) Remove the lower semicircular segments step by step until all the segments in the well are removed;

[0084] 9) If Figures 15 to 18 The construction tunnel ring beam and the structure inside the well are shown.

[0085] In summary, this embodiment has the following advantages:

[0086] 1. The sealing effect of the tunnel door is good, and there is no water leakage. The steel plate is welded to connect the tunnel door sealing plate and the back-covering steel plate of the tunnel opening ring. During the excavation process, welding and grouting are carried out simultaneously.

[0087] 2. The overall structural deformation of the tunnel is controllable.

[0088] 3. Protect the integrity of the segment structure. Before dismantling, add horizontal I-beam welded supports to the outside of the segment and add horizontal and vertical steel welded supports to the inside of the segment to ensure the stability of the overall structure.

[0089] 4. Maintain the stability of the surrounding strata. Grouting is performed on the soil around the segments before excavation to effectively control the displacement and settlement of the segments, while increasing the water-stopping effect of the soil outside the segments, greatly reducing the disturbance to the surrounding strata.

[0090] The above detailed description of the present invention is intended to enable persons familiar with the art to understand the contents of the present invention and implement them. It does not limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A construction method suitable for back-digging and dismantling of pipe segments in an in-situ test of a ventilation shaft, characterized in that: The method comprises the following steps: S1. Soil removal from tunnel vault When the soil is excavated to the position of 2±0.5m from the tunnel vault, protective excavation is carried out until the synchronous grouting body of the tunnel vault between the left and right openings is exposed, wherein multiple hole rings are formed between the two openings, each of which is assembled from multiple arc-shaped segments, and the hole ring formed at the opening is the opening ring; S2. Tunnel Gate Blockage a) excavating from the tunnel opening ring respectively, chiseling out the synchronous grouting inclusions on the vault, synchronously welding the tunnel door sealing plate and the tunnel opening ring backing steel plate, and chiseling out partial plugging; b) gradually excavating the soil on both sides of the tunnel opening ring, chiseling out the synchronous grouting inclusions on both sides of the tunnel opening ring, and synchronously welding the tunnel door sealing plate and the tunnel opening ring backing steel plate, and at the same time gradually adding temporary supports on the pipe segment where the tunnel opening ring is located, the temporary supports include external support frames and internal support frames respectively arranged on the outer side and inner side of the pipe segment corresponding to the tunnel opening ring, the external support frames include the ones located on both sides of the tunnel vault Multiple external support rods on the sides, wherein the external support rods are horizontally supported between the pipe segment at the hole ring and the inner wall of the air shaft along a direction perpendicular to the center line of the hole ring, and are spaced in sequence from the tunnel vault to the bottom, and the multiple external support rods on both sides are symmetrically arranged about the tunnel vault, or the multiple external support rods on both sides are spaced and staggered; c) until the soil on both sides of the pipe segment at the hole ring is excavated to the top surface of the plain concrete, the plain concrete at the hole rings at both ends and the synchronous grouting inclusions are chiseled out, and the steel plates are synchronously welded to complete the complete blocking of the tunnel door; S3. Segment removal First, break the top pipe segment of the middle hole ring between the two hole rings, then remove the pipe segments along the arc surface of the pipe segment of the middle hole ring to the hole rings on both sides in sequence, until the upper semicircular pipe segments between the two hole rings are removed, and then gradually remove the lower semicircular pipe segments until the pipe segments of the hole rings in the well are completely removed; S4, construction tunnel ring beam and shaft structure.

2. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 1 is characterized in that: The plurality of outer support rods include a top support rod, a bottom support rod and a middle support rod, and the length formed by the top support rod and the middle support rod gradually decreases from top to bottom, and the length formed by the middle support rod and the bottom support rod gradually increases from the middle to bottom.

3. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 2 is characterized in that: There is one middle support rod and it extends radially along the hole opening ring. The length of the top support rod is greater than that of the bottom support rod. The distance between the top support rod and the top surface of the hole opening ring is 3 / 5 to 7 / 10 of the radius of the hole opening ring. The bottom support rod is located between the lower semicircle of the tunnel and the top surface of the plain concrete, and the distance between the bottom support rod and the top surface of the hole opening ring is 1.2 to 1.4 times the radius of the hole opening ring.

4. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 1 is characterized in that: The inner support frame comprises a plurality of inner support rods located in the hole ring from which the synchronous grouting inclusion has been removed, wherein the inner support rods are arranged in parallel or / and intersecting.

5. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 1 is characterized in that: When removing the pipe segments in step S3, the top pipe segment of the middle hole ring is removed by using cutting tools and lifting tools, and then the pipe segment on the upper part of the middle hole ring is removed, and then the pipe segments are removed from the removal notch to the left or right to the hole ring in sequence until the upper semicircular pipe segment between the two hole rings is completely removed.

6. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 5 is characterized in that: The removal process of the lower semicircular pipe segment between the two hole rings is the same as that of the upper semicircular pipe segment.

7. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 1 is characterized in that: Before back-excavation construction, the water seepage gaps in the pipe segments need to be sealed, and at the same time, grouting is required into the soil at the bottom of the pipe segments through the grouting holes at the bottom of the pipe segments.

8. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 1 is characterized in that: During the excavation process, the tunnel entrance needs to be continuously sealed, and the open water in the ventilation shaft and / or the tunnel needs to be pumped out during the back-excavation construction.

9. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 1 is characterized in that: The construction of the tunnel ring beam and the shaft structure in step S4 includes the tunnel ring beam construction process and the shaft structure construction process.

10. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 9 is characterized in that: The construction process of the tunnel ring beam is to use an L-shaped steel bar with one end embedded in the side wall, and the other end welded to the tunnel ring back covering steel plate or the ring end covering steel plate, insert the annular steel bar to form a steel skeleton; support the formwork and cast concrete to form the tunnel ring beam, connecting the pipe segments of the tunnel ring with the wind shaft structure into a whole.

11. The construction method for reverse excavation and removal of pipe segments for in-situ testing of ventilation shafts according to claim 9 is characterized in that: The construction process of the shaft structure is to support the formwork inside the wind shaft, tie the steel bars and pour the concrete from bottom to top to form the shaft structure.

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