Inlet supporting structure of unsymmetrical pressure tunnel and construction method

Abstract

The invention provides an inlet supporting structure of an unsymmetrical pressure tunnel and a construction method, the inlet supporting structure comprises the tunnel, a side slope, an external supporting structure and an internal supporting structure, the external supporting structure comprises a reinforced concrete panel, a suspension anchor rod, a panel reinforcing member and an opposite penetrating reinforcing member, and the internal supporting structure comprises a fore shaft reinforcing member and an in-tunnel supporting system. A plurality of vertical grouting holes are formed in the side slope, each vertical grouting hole is filled with grouting materials, and the suspension anchor rods are anchored in the side slope and are arranged close to the vertical grouting holes. In this way, the mode of external fixing and internal supporting is formed through the external supporting structure and the internal supporting structure, the bearing capacity of the surrounding rock is exerted to the maximum extent, external supporting resistance is provided in an auxiliary mode, the purpose of safe tunnel entering is achieved under the conditions that excavation is not increased, a high slope is not formed and a pipe shed is not arranged, and especially for a flat-top large-span high-side-wall bias tunnel, the supporting structure is simple and convenient to use. Excavation of a high slope is avoided, project investment is reduced, the construction period is shortened, and environmental protection is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tunnel engineering, and particularly relates to an inlet support structure of a bias pressure tunnel and a construction method. BACKGROUND

[0002] In tunnel engineering, due to the limited axial position and other reasons, the inlet is often arranged close to the bank slope to form a bias pressure tunnel with thin overburden on the outer side and top arch and thick mountain on the inner side. If the excavation section is small and the top arch is excavated into an arch shape, the bias pressure tunnel can be safely excavated to form the required section after taking the conventional pipe shed into the tunnel, locking the support, and the in-tunnel system anchor shotcrete support due to the good stress condition. However, in the water power engineering, the excavation span is often large, such as greater than 20 m, and the excavation height is high, such as greater than 25 m. Under such conditions, the bias pressure, complex geological conditions, poor stability of surrounding rock and other factors often cause high construction safety risk, large support difficulty and difficult tunneling.

[0003] For the bias pressure tunnel with a large-span flat top and high side wall, the traditional support method usually changes the inlet position and increases the excavation amount to ensure that the overburden is thick enough to form a bearing ring, and then the surrounding rock is reinforced by support. However, these methods often cause adverse effects such as high side slope, prolonged construction period and increased construction cost.

[0004] Therefore, it is necessary to provide an inlet support structure of a bias pressure tunnel and a construction method to solve or at least alleviate the above problems. SUMMARY

[0005] The main purpose of the present application is to provide an inlet support structure of a bias pressure tunnel and a construction method to solve the problem of large excavation amount and easy formation of high side slope in the prior art support method.

[0006] To achieve the above purpose, the present application provides an inlet support structure of a bias pressure tunnel, which comprises a tunnel, a slope, an external support structure and an internal support structure, the tunnel is formed in the slope; wherein,

[0007] The external support structure comprises a reinforced concrete panel, a suspended anchor rod, a panel reinforcing member and a through reinforcing member, and the internal support structure comprises a lock reinforcing member and an in-tunnel support system; wherein,

[0008] A plurality of vertical grouting hole groups are arranged in the slope along the width direction of the tunnel, each vertical grouting hole group comprises a plurality of vertical grouting holes arranged along the extension direction of the tunnel, the vertical grouting holes are arranged at the top of the tunnel, each vertical grouting hole is filled with grouting material, and the suspended anchor rod is anchored in the slope and arranged close to each vertical grouting hole;

[0009] The steel reinforced concrete panel is connected to the slope side of the slope and arranged close to the tunnel, the panel reinforcement penetrates the steel reinforced concrete panel, the slope and extends into the mountain in sequence, and the panel reinforcement is arranged on the top of the tunnel in sequence.

[0010] The lock reinforcement is arranged in the slope and surrounds the outside of the tunnel, and the tunnel support system is supported on the inside of the tunnel.

[0011] Preferably, the steel reinforced concrete panel comprises a first reinforcing section and a second reinforcing section arranged from top to bottom, the first reinforcing section is arranged above the tunnel, and the second reinforcing section is arranged beside the tunnel.

[0012] Preferably, the panel reinforcement comprises a plurality of panel anchor cable groups arranged vertically, each panel anchor cable group comprises a plurality of panel anchor cables arranged along the extension direction of the tunnel, and the panel anchor cables penetrate the first reinforcing section of the steel reinforced concrete panel, the slope and are anchored in the mountain in sequence.

[0013] Preferably, the lock reinforcement comprises a plurality of lock anchor rod groups, each lock anchor rod group comprises a plurality of lock anchor rods arranged along the circumference of the tunnel, and the lock anchor rods extend along the extension direction of the tunnel and are arranged outside the tunnel.

[0014] Preferably, the number of lock anchor rod groups is two, and the lock anchor rods in the two lock anchor rod groups are arranged staggered.

[0015] Preferably, the through reinforcement comprises a plurality of pre-stressed through anchor rod groups arranged vertically, each pre-stressed through anchor rod group comprises a plurality of pre-stressed through anchor rods arranged along the extension direction of the tunnel, and the pre-stressed through anchor rods penetrate the second reinforcing section of the steel reinforced concrete panel, the slope and extend into the tunnel in sequence.

[0016] Preferably, the external support structure further comprises a reinforcing bar, one end of the reinforcing bar is connected to the slope, and the other end of the reinforcing bar is embedded in the first reinforcing section of the steel reinforced concrete panel.

[0017] Preferably, the external support structure further comprises a first slope anchor cable and a second slope anchor cable, the first slope anchor cable is anchored in the mountain, and the second slope anchor cable extends along the extension direction of the tunnel and is anchored in the slope.

[0018] Preferably, the external support structure further comprises a slope anchor rod, and the slope anchor rod is anchored in the side wall of the tunnel and the mountain.

[0019] The application also provides a construction method of a support structure of an entrance of a bias tunnel, which is applied to the support structure of the entrance of the bias tunnel as described above, and comprises the following steps:

[0020] S1, excavating a slope body at the entrance of a target tunnel to form the slope;

[0021] S2, performing consolidation grouting at the slope above the top of the target tunnel, and installing the suspension anchor rod in the consolidation grouting position;

[0022] S3, applying the reinforced concrete panel at the slope surface of the slope, and arranging the panel reinforcing member on the reinforced concrete panel to extend into the mountain;

[0023] S4, excavating the tunnel face of the target tunnel to form a vertical tunnel face, and installing the lock reinforcing member outside the top arch contour of the target tunnel;

[0024] S5, excavating the target tunnel to form the tunnel, and applying the internal support system in the tunnel; wherein the internal support system comprises a steel arch, system anchor rods and a hanging net sprayed concrete support;

[0025] S6, drilling a hole from inside to outside of the tunnel in the tunnel, and installing the through reinforcing member in the hole to extend into the reinforced concrete panel;

[0026] S7, excavating the lower layer of the tunnel, pre-burying a bottom plate in the lower layer of the tunnel, extending the arch foot of the steel arch downward to be fixedly connected with the bottom plate, and completing the construction of the tunnel.

[0027] Compared with the prior art, the application has the following beneficial effects:

[0028] The application provides an entrance support structure of a bias pressure tunnel and a construction method, which comprises a tunnel, a slope, an external support structure and an internal support structure, the external support structure comprises a reinforced concrete panel, a suspension anchor rod, a panel reinforcing piece and a through reinforcing piece, the internal support structure comprises a lock mouth reinforcing piece and an in-hole support system, a plurality of groups of vertical grouting holes are arranged in the slope in a width direction of the tunnel, each group of vertical grouting holes comprises a plurality of vertical grouting holes arranged in an extension direction of the tunnel, the bottom end of each vertical grouting hole extends to the top of the tunnel, each vertical grouting hole is filled with grouting material and is internally connected with the suspension anchor rod, the reinforced concrete panel is connected to the slope side of the slope and is arranged close to the tunnel, the panel reinforcing piece penetrates the reinforced concrete panel, the slope and extends into the mountain body in sequence, and the panel reinforcing piece is arranged on the top of the tunnel in a spaced mode, the lock mouth reinforcing piece is internally arranged in the slope and is arranged on the outside of the tunnel in a surrounding mode, and the through reinforcing piece penetrates the reinforced concrete panel, the slope and extends into the tunnel in sequence; the lock mouth reinforcing piece is internally arranged in the slope and is arranged on the outside of the tunnel in a surrounding mode, and the in-hole support system is supported on the inside of the tunnel. In this way, the external support structure and the internal support structure form an "external support and internal support" mode, the self bearing capacity of the surrounding rock is maximally utilized, the external support resistance is supplemented, the goal of safe tunneling is achieved, especially for the bias pressure tunnel with a flat top, a large span and a high side wall, the high slope is avoided, and the project investment is reduced, the construction period is saved and the environmental protection is facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained from the drawings shown without any creative effort.

[0030] Figure 1 The application scenario diagram of the overall structure in an embodiment of the present application.

[0031] The purposes, functional features and advantages of the present application will be further described with reference to the embodiments and the drawings.

[0032] Explanation of the reference signs:

[0033] 10, tunnel; 20, slope; 210, vertical grouting hole; 30, external support structure; 310, reinforced concrete panel; 311, first reinforcing section; 312, second reinforcing section; 320, suspension anchor rod; 330, panel anchor cable; 340, prestressed through anchor rod; 350, inserted reinforcing bar; 360, first slope anchor cable; 370, second slope anchor cable; 380, slope anchor rod; 40, internal support structure; 410, lock mouth anchor rod; 420, in-hole support system; 50, mountain body. DETAILED DESCRIPTION

[0034] It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

[0035] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0036] It should be noted that all the directionality indications (such as up, down, left, right, front, back, and the like) in the embodiments of the present application are only used to explain the relative position relationship, movement condition and the like between components in a certain specific posture (as shown in the drawings), and if the specific posture changes, the directionality indications also change accordingly.

[0037] In addition, the descriptions involving “first”, “second” and the like in the present application are only for the purpose of description, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features with “first” and “second” can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the realization of a person of ordinary skill in the art, and when the combination of technical solutions contradicts each other or cannot be realized, it should be considered that the combination of technical solutions does not exist, and is also not within the protection scope of the present application.

[0038] Please refer to the accompanying drawings Figure 1 In an embodiment of the present application, an entrance support structure of a bias tunnel 10 is provided, which includes a tunnel 10, a slope 20, an external support structure 30 and an internal support structure 40. The tunnel 10 is built in the slope 20, and the specific scheme is as follows:

[0039] The external support structure 30 comprises a reinforced concrete panel 310, a suspended anchor rod 320, a panel reinforcing member and a through-reinforcing member, the internal support structure 40 comprises a lock reinforcing member and an in-hole support system 420; a plurality of vertical grouting holes 210 groups are arranged in the slope 20 along the width direction of the tunnel 10, each group of vertical grouting holes 210 comprises a plurality of vertical grouting holes 210 arranged along the extension direction of the tunnel 10, the vertical grouting holes 210 are arranged at the top of the tunnel 10, each vertical grouting hole 210 is filled with grouting material, and the suspended anchor rod 320 is anchored in the slope 20 and arranged close to each vertical grouting hole 210; the reinforced concrete panel 310 is connected to the slope surface of the slope 20 and arranged close to the tunnel 10, the panel reinforcing member penetrates the reinforced concrete panel 310, the slope 20 and extends into the mountain 50 in sequence, and the panel reinforcing member is arranged at intervals above the top of the tunnel 10, the lock reinforcing member is arranged in the slope 20 and surrounds the outside of the tunnel 10, and the through-reinforcing member penetrates the reinforced concrete panel 310, the slope 20 and extends into the tunnel 10 in sequence; the lock reinforcing member is arranged in the slope 20 and surrounds the outside of the tunnel 10, and the in-hole support system 420 is supported on the inside of the tunnel 10.

[0040] Specifically, the inlet support structure of the bias tunnel 10 comprises a tunnel 10, a slope 20, an external support structure 30 and an internal support structure 40, and the present application is mainly applied to a flat-top large-span high-side-wall bias tunnel 10. The bias tunnel 10 usually refers to a special tunnel form in which the pressure of the surrounding rock on both sides of the tunnel structure is significantly asymmetric due to topography, geology or construction factors. Therefore, the tunnel 10 in the present application is formed inside the slope 20, and the external support structure 30 is used to reinforce the external slope 20 rock mass, and at the same time, the internal support structure 40 is used for internal support during excavation of the tunnel 10, so that the comprehensive reinforcement measures of "external support and internal support" are realized, the tunnel 10 is safely entered without increasing excavation, forming a high slope 20 and setting a pipe shed, and the long-term stability of the tunnel 10 is ensured.

[0041] The external support structure 30 comprises a reinforced concrete panel 310, a suspended anchor rod 320, a panel reinforcing member, a lock reinforcing member, and a through reinforcing member. In the initial stage of reinforcing the outside of the tunnel, the slope surface is reinforced by consolidation grouting and the suspended anchor rod 320 to improve the integrity of the top surrounding rock. Specifically, a plurality of groups of vertical grouting holes 210 are arranged in the slope 20 along the width direction of the tunnel 10, and each group of vertical grouting holes 210 comprises a plurality of vertical grouting holes 210 arranged along the extension direction of the tunnel 10. This facilitates grouting, and the composition and ratio of the grouting material can be determined by a person skilled in the art according to the actual topography and performance requirements. Therefore, the details are not described here. After grouting is completed, the suspended anchor rod 320 is installed in the vicinity of the vertical grouting hole 210 to improve the integrity of the top surrounding rock.

[0042] Further, the reinforced concrete panel 310 is used to compensate for the structure of the weak rock mass on the side of the tunnel 10. Typically, it is located at the position of the concave part of the rock mass relative to the entire slope 20 around the tunnel 10. This stabilizes the mountain 50. Therefore, the reinforced concrete panel 310 is connected to the side of the slope 20 and is arranged close to the tunnel 10. The side of the reinforced concrete panel 310 facing the slope body needs to match the slope surface to ensure close connection. Preferably, considering the characteristics of the bias tunnel, the reinforced concrete panel can be arranged in the form of a first reinforcing section 311 and a second reinforcing section 312. The first reinforcing section 311 is arranged above the tunnel 10 to improve the integrity of the rock mass above the tunnel 10, and the second reinforcing section 312 is arranged on the side of the tunnel 10 to strengthen the integrity of the rock mass on the side of the tunnel 10.

[0043] After the reinforced concrete panel 310 is constructed, the panel reinforcing member is arranged on the reinforced concrete panel 310 to stabilize it together with the slope 20 and the rock mass, thereby improving the integrity. In a preferred embodiment of the present application, the panel reinforcing member comprises a plurality of groups of panel anchor cables 330 arranged vertically in a row. Each group of panel anchor cables 330 comprises a plurality of panel anchor cables 330 arranged along the extension direction of the tunnel 10. The panel anchor cables 330 pass through the first reinforcing section 311 of the reinforced concrete panel 310, the slope 20, and are anchored in the mountain 50 in sequence. This greatly improves the compression force and sliding resistance, and has little disturbance to the slope body. Further, a plurality of spaced reinforcing bars 350 can be arranged at the lower part of the reinforced concrete panel 310. One end of the reinforcing bar 350 is connected to the slope 20, and the other end of the reinforcing bar 350 is embedded in the first reinforcing section 311 of the reinforced concrete panel 310. This tightly "hangs" the weak rock mass on the reinforced concrete panel 310 and the surrounding stable mountain 50, so that this part of the rock mass will not collapse after the tunnel is excavated.

[0044] Further, the lock mouth reinforcing member is used to improve the integrity of the overlying rock mass around the tunnel 10; in a preferred embodiment, the lock mouth reinforcing member comprises a plurality of lock mouth anchor rod groups 410, each of which comprises a plurality of lock mouth anchor rods 410 arranged at intervals along the circumference of the tunnel 10, and the lock mouth anchor rods 410 extend along the extension direction of the tunnel 10 and are arranged outside the tunnel 10. Thus, in the initial stage of excavating the tunnel face, a plurality of lock mouth anchor rods 410 are arranged around the outside of the tunnel 10, and to better improve the effect, a plurality of groups of lock mouth anchor rods 410 can be arranged, that is, after one group of lock mouth anchor rods 410 is arranged, other groups of lock mouth anchor rods 410 are arranged around the basis of the one group of lock mouth anchor rods 410. Preferably, based on the construction space and construction cost, the number of groups of lock mouth anchor rods 410 can be set to two on the premise of ensuring the construction effect, and it is worth mentioning that the (adjacent) lock mouth anchor rods 410 in the two groups are staggered with each other to uniformly distribute the anchor rod stress and reduce stress concentration, forming a spatial staggered grid structure, which can better enhance the integrity of the surrounding rock.

[0045] Further, the through reinforcing member is used to improve the connection integrity between the reinforced concrete panel 310, the slope 20, and the tunnel 10 after excavation; in a preferred embodiment, the through reinforcing member comprises a plurality of groups of pre-stressed through anchor rods 340 arranged at intervals in the vertical direction, each of which comprises a plurality of pre-stressed through anchor rods 340 arranged at intervals along the extension direction of the tunnel 10, and the pre-stressed through anchor rods 340 sequentially penetrate the second reinforcing section 312 of the reinforced concrete panel 310, the slope 20, and extend into the tunnel 10. Thus, through the action of pre-stress, the external reinforced concrete panel 310 (mainly the second reinforcing section 312), the slope 20, and the surrounding rock in the tunnel 10 are pulled tightly with each other, thereby forming a whole supporting structure.

[0046] Further, the external supporting structure 30 further comprises a first slope anchor cable 360 and a second slope anchor cable 370, the first slope anchor cable 360 is anchored in the mountain 50, and the second slope anchor cable 370 extends along the extension direction of the tunnel 10 and is anchored in the slope 20.

[0047] It should be noted that the first slope anchor cable 360 is used to strengthen the connection integrity and fastening between the slope 20 and the mountain 50, so as to stabilize the slope 20 on the mountain 50 and prevent sliding deformation; and the second slope anchor cable 370 is used to improve the stress state of the slope 20, thereby improving the integrity of the slope 20 and avoiding landslides.

[0048] Further, the external support structure 30 further comprises a slope 20 anchor, which is anchored in the sidewall of the tunnel 10 and the mountain 50.

[0049] It should be noted that the slope 20 anchor is used to tightly anchor the tunnel 10 and the mountain 50, prevent the steel frame from sinking or moving inward due to the surrounding rock pressure, and enhance the structural integrity of the in-hole support system 420.

[0050] The application also provides a construction method for biasing the entrance support structure of a tunnel 10, which is applied to the biasing entrance support structure of a tunnel 10 as described above, and comprises the following steps:

[0051] S1, excavate the slope body at the entrance of the target tunnel 10 to form the slope 20; it should be noted that when excavating, the entrance slope 20 is excavated and supported moderately to meet the basic body shape of the slope 20 required for safe operation of the tunnel 10 structure, and a suitable construction platform is formed for subsequent operations.

[0052] S2, consolidate grouting at the slope 20 above the top of the target tunnel 10, and install the suspended anchor 320 in the consolidated grouting position; it should be noted that when performing the consolidation grouting operation, the slope 20 above the excavated top and its road should be used to erect a construction platform, before grouting, drill a vertical grouting hole 210 from top to bottom on the slope 20 above the top on the construction platform, and then segmentally grout downward in the vertical grouting hole 210 to consolidate the broken rock mass on the upper part of the rectangular tunnel 10 excavation section, and improve the integrity of the surrounding rock; then perform the construction of the suspended anchor 320: vertical hole drilling → anchor installation → grouting → tensioning and locking.

[0053] S3, the reinforced concrete panel 310 is constructed on the slope surface of the slope 20, and the panel reinforcing member is arranged on the reinforced concrete panel 310 to extend into the mountain 50; it should be noted that first, the base of the slope 20 slope surface side should be cleaned, and then a certain thickness of reinforced concrete panel 310 should be constructed, it should be noted that the range of the reinforced concrete panel 310 should be greater than the area where the rock mass of the slope 20 is thin (concave) to stabilize the weak rock mass; after the reinforced concrete panel 310 is formed, the panel reinforcing member (panel anchor cable 330) is installed to pass through the first reinforcing segment 311 of the reinforced concrete panel 310, the slope 20 (above the top of the tunnel 10) and anchor in the stable rock mass of the mountain 50.

[0054] S4, excavate the tunnel face of the target tunnel 10 to form a vertical tunnel face, and install the locking reinforcement outside the contour of the tunnel crown of the target tunnel 10; it can be understood that after the external reinforcement of the tunnel top slope 20 is completed, the excavation preparation work of the tunnel 10 can be carried out, and when the tunnel 10 is excavated, i.e. when the tunnel face of the target tunnel 10 is excavated to form a vertical tunnel face, the locking reinforcement (locking anchor 410) needs to be immediately installed outside the contour of the tunnel crown to improve the integrity of the overlying rock mass, and the tunnel 10 excavation work can be started after the locking anchor 410 is tightened.

[0055] S5, excavate the target tunnel 10 to form the tunnel 10, and construct the internal support system 420 inside the tunnel 10; wherein the internal support system 420 includes steel arches, system anchor rods and shotcrete support with mesh; it is worth mentioning that for large-span high-side-wall tunnels 10, layered excavation and step-by-step excavation measures are generally taken to excavate the tunnel 10 in a short footage and weak blasting manner, which is a well-known technology to those skilled in the art, and therefore will not be described in detail here; while the tunnel 10 is excavated, the internal support system 420 is constructed, which usually includes steel arches, system anchor rods and shotcrete support with mesh, which is a common internal support method in tunnel construction, so as to form an "external support and internal support" mode to achieve the goal of safe tunneling.

[0056] S6, drill holes from inside to outside in the tunnel 10, and install the through reinforcement into the reinforced concrete panel 310; it should be understood that when the tunnel crown is completely excavated, the through reinforcement (prestressed through anchor 340) needs to be arranged, the prestressed through anchor 340 can be installed in the corresponding drilled hole, and the prestressed anchor is tensioned to tighten the reinforced concrete panel 310, the slope 20 and the surrounding rock inside the tunnel 10 to form an integral support structure.

[0057] S7, excavate the lower layer of the tunnel 10, embed the bottom plate in the lower layer of the tunnel 10, extend the arch foot of the steel arch to the bottom plate for fixed connection, and complete the construction of the tunnel 10.

[0058] It can be understood that after the lower layer of the tunnel 10 is excavated, the steel arch is extended downward to be stably supported on the bottom plate, thereby improving the connection stability and support strength.

[0059] In order to facilitate those skilled in the art to understand the technical solutions of the present application, the following specific examples are also provided:

[0060] The water power station diversion tunnel entrance has a span of 20.56 m and a height of 26.85 m; the tunnel top within a range of 10 m from the entrance has a triangular platform with a maximum length of 10 m, a height of 2585 m, and an area of about 82 m 2 , and the distance from the excavation line in the tunnel to the natural slope surface is only 20 m; the distance from the upper left corner in the tunnel to the concave area of the natural slope surface is 4.4 m, so the stability of the surrounding rock during excavation into the tunnel is particularly prominent. Therefore, the design adopts the comprehensive support structure of "external fixation and internal support" in the application, and the tunnel 10 is successfully realized by the construction scheme of step-by-step excavation and timely support, and has been safely operated for many years. The specific method is as follows:

[0061] Consolidation grouting and suspended anchor rod 320: consolidation grouting is carried out on the platform with a height of 2585 m within the excavation span range of the tunnel 10 to treat the rock slab. The vertical grouting hole 210 is 25 m deep, the hole diameter is 56 mm, the interval distance is 2.5 m, the grouting pressure is 0.5-0.7 MPa, and a φ32L12 m anchor rod is arranged in the grouting hole.

[0062] Slope concrete and anchor cable: in the range of 28 m of the tunnel mouth, the natural terrain concave area and its periphery, a C25 concrete panel with a minimum thickness of 1.5 m is arranged, and a steel mesh φ28 with a spacing of 200 mm is arranged. The panel area is provided with a reinforcing bar 350 with a specification of φ32L9 m and φ28L6 m. Six panel anchor cables 330 are arranged, with a design tonnage of 2000 KN. The panel and the panel anchor cable 330 are completed 40 days before the tunnel excavation.

[0063] The tunnel face arch top 2 circle lock mouth anchor rod 410 has a specification of φ32L9 m, a ring spacing of 1 m, and a row spacing of 1 m.

[0064] The tunnel steel arch I18 has a spacing of 0.75 m; the tunnel system spray anchor support is arranged with a steel mesh φ6 with a spacing of 200 mm, a C25 concrete with a thickness of 280 mm, a system anchor rod φ32L9 m and φ28L6 m arranged in cross.

[0065] The φ32 pre-stressed opposite-through anchor rod 340 is arranged on the panel in the original terrain concave area, with 4 rows and an interval row distance of 2.5 m, and a pre-stress of 20 t.

[0066] The above is only a preferred embodiment of the application, and does not limit the patent scope of the application, and any equivalent structure or equivalent process transformation using the content of the application specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the application.

Claims

1. An inlet support structure for a biased tunnel, characterized in that, It includes a tunnel, a slope, an external support structure, and an internal support structure, wherein the tunnel is built into the slope; wherein, The external support structure includes reinforced concrete panels, suspended anchors, panel reinforcement components, and through-hole reinforcement components; the internal support structure includes interlocking reinforcement components and an internal support system. Multiple sets of vertical grouting holes are provided in the slope at intervals along the width direction of the tunnel. Each set of vertical grouting holes includes multiple vertical grouting holes at intervals along the extension direction of the tunnel. The vertical grouting holes are located at the top of the tunnel. Each vertical grouting hole is filled with grouting material. The suspension anchor is anchored in the slope and located close to each vertical grouting hole. The reinforced concrete panel is connected to the slope side of the slope and is set close to the tunnel. The panel reinforcements pass through the reinforced concrete panel and the slope in sequence and extend into the mountain body. The panel reinforcements are arranged at intervals above the top of the tunnel. The through reinforcements pass through the reinforced concrete panel and the slope in sequence and extend into the tunnel. The locking reinforcement is built into the slope and surrounds the outside of the tunnel, while the tunnel support system supports the inside of the tunnel.

2. The inlet support structure of the biased tunnel according to claim 1, characterized in that, The reinforced concrete panel includes a first reinforcement section and a second reinforcement section arranged from top to bottom. The first reinforcement section is located above the tunnel, and the second reinforcement section is located on the side of the tunnel.

3. The inlet support structure for the biased tunnel according to claim 2, characterized in that, The panel reinforcement includes multiple rows of panel anchor cable groups arranged vertically at intervals. Each row of panel anchor cable groups includes multiple panel anchor cables arranged at intervals along the extension direction of the tunnel. The panel anchor cables pass through the first reinforcement section of the reinforced concrete panel and the slope in sequence and are anchored in the mountain.

4. The inlet support structure for a biased tunnel according to claim 1, characterized in that, The locking reinforcement includes multiple rings of locking anchor bolts. Each ring of the locking anchor bolt group includes multiple locking anchor bolts spaced apart along the circumference of the tunnel. The locking anchor bolts extend along the extension direction of the tunnel and are located on the outside of the tunnel.

5. The inlet support structure for a biased tunnel according to claim 4, characterized in that, The number of lock anchor bolt groups is two rings, and the lock anchor bolts in the two rings of lock anchor bolt groups are staggered.

6. The inlet support structure of the biased tunnel according to claim 2, characterized in that, The through-through reinforcement includes multiple rows of prestressed through-through anchor bolt groups arranged vertically at intervals. Each row of the prestressed through-through anchor bolt groups includes multiple prestressed through-through anchor bolts arranged at intervals along the extension direction of the tunnel. The prestressed through-through anchor bolts sequentially penetrate the second reinforcement section of the reinforced concrete panel, the slope, and extend into the tunnel.

7. The inlet support structure for a biased tunnel according to claim 3, characterized in that, The external support structure also includes reinforcing bars, one end of which is inserted into the slope and the other end of which is embedded in the first reinforcement section of the reinforced concrete panel.

8. The inlet support structure for a biased tunnel according to claim 1, characterized in that, The external support structure also includes a first slope anchor cable and a second slope anchor cable. The first slope anchor cable is anchored in the mountain, and the second slope anchor cable extends along the extension direction of the tunnel and is anchored in the slope.

9. The inlet support structure for a biased tunnel according to claim 1, characterized in that, The external support structure also includes slope anchors, which are anchored to the sidewalls of the tunnel and the mountain.

10. A construction method for the inlet support structure of an eccentrically loaded tunnel, applied to the inlet support structure of an eccentrically loaded tunnel as described in any one of claims 1-9, characterized in that, Including the following steps: S1, excavate the slope at the entrance of the target tunnel to form the slope; S2, perform consolidation grouting at the slope above the top of the target tunnel, and install the suspension anchor at the consolidation grouting location; S3, construct the reinforced concrete panel on the slope surface of the slope, and install the panel reinforcement on the reinforced concrete panel until it extends into the mountain; S4, excavate the tunnel face to form a vertical slope, and install the locking reinforcement on the outside of the tunnel arch outline; S5, excavate the target tunnel to form the tunnel, and construct the tunnel support system inside the tunnel; wherein, the tunnel support system includes steel arch frame, system anchor bolts and shotcrete support with wire mesh; S6, drill a hole from the inside of the tunnel to the outside of the tunnel, and install the through-hole reinforcement in the drill hole until it extends into the reinforced concrete panel; S7. Excavate the lower layer of the tunnel and pre-embed a base plate in the lower layer of the tunnel. Extend the arch foot of the steel arch frame downwards to be fixedly connected with the base plate to complete the construction of the tunnel.

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