A small-span tunnel supporting device and a supporting method thereof in a soft surrounding rock environment

Abstract

The application discloses a small-span tunnel supporting device in a soft surrounding rock environment and a supporting method thereof, and the bottom of the tunnel is supported through a bottom supporting part, and the top of the tunnel is supported through a top supporting part; meanwhile, the bottom supporting part and the top supporting part are mutually anchored and reinforced through the multilayer supporting structures of the bottom supporting part and the top supporting part, so that the stability of the supporting structures is ensured, the tunnel in the soft surrounding rock environment can be stably supported, the stability of the supporting structures is effectively ensured, and the load bearing property of the supporting structures is improved.

Description

A support device and method for short-span tunnels in weak surrounding rock environments Technical Field

[0001] This invention belongs to the technical field of tunnel support, specifically relating to a support device and method for small-span tunnels in weak surrounding rock environments. Background Technology

[0002] Municipal and water conservancy projects, such as water conveyance tunnels and transportation tunnels, often encounter weak surrounding rock at their entrances and exits. Weak surrounding rock is characterized by its soft surrounding rock, low bearing capacity, well-developed joints and fissures, and fragmented structure. This results in weak surrounding rock being fragmented, loose, poorly bonded, low in strength, easily softened by water, and prone to landslides. If the surrounding weak surrounding rock is not effectively reinforced during tunnel excavation in areas with weak surrounding rock, deformation and collapse are highly likely during tunnel construction, posing a significant threat to construction safety.

[0003] Existing support structures for weak surrounding rock mostly employ methods such as pre-grouting reinforcement and temporary support during construction to reinforce the surrounding rock. However, in weak surrounding rock environments, the surrounding rock is inherently loose and prone to slippage. Therefore, support structures that are directly anchored to the surrounding rock are also prone to slippage and displacement, thus affecting the stability of the support structure itself.

[0004] In view of the shortcomings of existing support structures for weak surrounding rock and the difficulty in ensuring the stability of the support structure itself during construction, this invention discloses a support device and method for small-span tunnels in weak surrounding rock environments. Summary of the Invention

[0005] The purpose of this invention is to provide a support device and method for small-span tunnels in weak surrounding rock environments, which can provide stable support for tunnels in weak surrounding rock environments, effectively ensure the stability of the support structure itself, and improve the load-bearing capacity of the support structure.

[0006] This invention is achieved through the following technical solution:

[0007] A support device for short-span tunnels in weak surrounding rock environments includes a bottom support and a top support located above the bottom support. The bottom support includes a bottom arch support corresponding to the tunnel's bottom arch, side wall supports corresponding to the left and right side walls of the tunnel, and a drainage cavity located inside the side wall supports. The bottom of the side wall supports is connected to the end of the bottom arch support via prestressed steel cables. A water guide pipe is provided on one side of the drainage cavity facing away from the tunnel. The top support includes an arch support corresponding to the tunnel's arch and a shoulder. The arch supports are linearly spaced at the top of the side wall supports on the left and right sides along the tunnel axis. An outer reinforcement is provided on the side of the arch support closest to the surrounding rock, and an inner reinforcement is provided on the side of the arch support away from the surrounding rock. A segment lining or shotcrete support is provided between the outer and inner reinforcements depending on the surrounding rock grade.

[0008] The bottom arch support in the bottom support section reinforces the tunnel's bottom arch position, while the sidewall supports at both ends of the bottom arch support section reinforce the tunnel's left and right sidewalls. Simultaneously, drainage chambers are installed inside the prefabricated sidewall supports, which are connected to the surrounding rock via water pipes. By incorporating drainage chambers, the weight of the sidewall supports is effectively reduced, and the water pipes quickly guide accumulated water from the surrounding rock to the drainage chambers for discharge, helping to lower the water level in the surrounding rock and thus reducing the risk of tunnel leakage. To ensure the stability of the sidewall supports, prestressed steel cables connect the bottom of the sidewall supports to the ends of the bottom arch support section. An inverted U-shaped top support is installed between the tops of the sidewall supports on both sides. This top support consists of three layers: outer, middle, and inner. The outer layer is an external reinforcement close to the surrounding rock; the middle layer is the arch support primarily bearing the pressure of the arch crown; and the inner layer is an internal reinforcement that shares the pressure of the arch crown and further reinforces the arch support. Furthermore, depending on the surrounding rock grade, either a segment lining section or a shotcrete and anchor support section is installed between the inner and outer reinforcement sections. The segment lining section supports and reinforces surrounding rock of grade IV or higher, while the shotcrete and anchor support section supports and reinforces surrounding rock of grade IV or lower, thus achieving stable support for the tunnel in weak rock environments.

[0009] To better realize the present invention, an outer waterproof layer is provided between the outer reinforcement part and the arch support part, and an inner waterproof layer is provided between the inner reinforcement part and the arch support part.

[0010] To better realize the present invention, furthermore, a plurality of anchor rods are provided circumferentially between the inner reinforcement part and the outer reinforcement part, anchored into the rock wall, and the arch support part is provided with an opening for the connecting anchor rods to pass through; a connecting anchor plate is provided between the free ends on the left and right sides of the inner reinforcement part and the outer reinforcement part, and the connecting anchor plate is anchored to the top of the side wall support part.

[0011] To better realize the present invention, the left and right ends of the bottom arch support are provided with pressure-bearing inclined surfaces, and the bottom end of the side wall support is provided with a compression inclined surface that squeezes the pressure-bearing inclined surface toward the center of the tunnel. The compression inclined surface and the pressure-bearing inclined surface are connected by prestressed steel cables.

[0012] To better realize the present invention, further, the top, middle and bottom of the drainage cavity on the side away from the tunnel are respectively provided with water guide pipes extending into the surrounding rock, and a gravel filter layer is provided at the end of the water guide pipe extending into the surrounding rock.

[0013] To better realize the present invention, it further includes a temporary support section installed inside the tunnel. The temporary support section includes horizontal temporary support components and vertical temporary support components. The horizontal temporary support components are installed horizontally between the side wall support sections on the left and right sides or horizontally inside the inner reinforcement section. The vertical temporary support components are installed vertically between the inner reinforcement section and the bottom arch support section.

[0014] A method for supporting short-span tunnels in weak surrounding rock environments, based on the aforementioned support device for short-span tunnels in weak surrounding rock environments, includes the following steps:

[0015] Step 1: Inspect the quality of the surrounding rock around the tunnel and determine the rock grade;

[0016] Step 2: Excavate the tunnel soil along the excavation line, and pre-support the excavated part of the tunnel using sidewall supports and arch frames;

[0017] Step 3: Reinforce the tunnel's bottom arch and sidewalls with grouting. After reinforcement, construct the bottom arch support corresponding to the tunnel's bottom arch, and then install reinforcement anchors between the bottom arch support and the surrounding rock at the bottom of the tunnel.

[0018] Step 4: The sidewall support is a precast component with drainage chambers and water pipes inside. Then, using the bottom arch support as the construction foundation, the sidewall support is constructed on the left and right sides of the tunnel through prestressed steel cables. Horizontal connecting anchors are installed between the sidewall support and the surrounding rock of the tunnel sidewall for reinforcement. The pre-pressure of the bottom arch support on the sidewall support is tested.

[0019] Step 5: Perform grouting reinforcement on the arch shoulder and arch crown of the tunnel. After the reinforcement is completed, construct an external reinforcement between the top of the sidewall support on the left and right sides of the arch shoulder and the arch crown. Then, based on the external reinforcement, construct an arch crown support linearly at intervals along the tunnel axis on the side of the external reinforcement away from the surrounding rock. Connect the arch crown support to the external reinforcement through connecting ring bars. Finally, construct an external waterproof layer between the external reinforcement and the arch crown support.

[0020] Step 6: If the surrounding rock grade is less than IV, spray anchors are directly used to form a spray anchor support between adjacent arch support sections; if the surrounding rock grade is greater than or equal to IV, segment lining is directly constructed between adjacent arch support sections, and ring reinforcement is used to connect the segment lining section with the external reinforcement section.

[0021] Step 7: Apply an inner waterproof layer on the side of the arch support away from the surrounding rock. Then, relying on the outer reinforcement, apply an inner reinforcement between the tops of the side wall supports on both sides. Then, apply anchor bolts circumferentially between the inner and outer reinforcements and anchor them into the rock wall.

[0022] To better realize the present invention, further, if the cross-sectional width of the tunnel is greater than or equal to 6.5m, then after the external reinforcement is constructed and before the internal reinforcement is constructed, a temporary support is constructed on the inner side of the tunnel; if the surrounding rock grade is greater than or equal to Class V, then the temporary support includes a set of horizontal temporary support members and a set of vertical temporary support members forming a cross-shaped support structure; if the surrounding rock grade is greater than or equal to Class V and is located in the tunnel entrance area, then the temporary support includes at least two sets of horizontal temporary support members and at least two sets of vertical temporary support members.

[0023] To better realize the present invention, further, after the internal reinforcement is constructed, the connecting section of the horizontal temporary support extending into the side wall support or the interior of the internal reinforcement is retained, and the support section of the horizontal temporary support extending into the tunnel is cut off; the connecting section of the vertical temporary support extending into the interior of the internal reinforcement or the bottom arch support is retained, and the support section of the vertical temporary support extending into the tunnel is cut off.

[0024] To better realize the present invention, furthermore, before applying the external waterproof layer, the surrounding rock around the tunnel is pre-anchored for drainage.

[0025] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0026] (1) This invention provides support for the bottom of the tunnel by setting a bottom support at the bottom position of the tunnel, and provides effective support for the bottom arch position of the tunnel by setting a bottom arch support in the bottom support. Side wall support is set at both ends of the bottom arch support to support the side walls on both sides of the tunnel, thereby effectively ensuring the stability of the bottom structure of the tunnel and the surrounding rock. In the side wall support, the drainage chamber is connected to the surrounding rock by a water pipe, so that the water in the surrounding rock can quickly enter the drainage chamber through the water pipe to drain the water, thereby effectively reducing the water level of the surrounding rock and preventing tunnel leakage. The side wall support on both sides applies pressure to the bottom arch support towards the center of the tunnel, thereby ensuring the stability of the bottom arch support and effectively preventing the side wall support and the bottom arch support from sliding.

[0027] (2) The present invention relies on the bottom support part and sets the top support part on the top of the bottom support part to support and reinforce the top of the tunnel and the surrounding rock. The bottom arch support part in the top support part supports and reinforces the top and shoulder positions of the tunnel. At the same time, in order to improve the stability of the bottom arch support part itself, an outer reinforcement part is set on the side of the bottom arch support part close to the surrounding rock, and an inner reinforcement part is set on the side of the bottom arch support part away from the surrounding rock. The outer reinforcement part reinforces the outer side of the bottom arch support part, and the inner reinforcement part reinforces the inner side of the bottom arch support part, which effectively improves the stability and load-bearing capacity of the bottom arch support part itself.

[0028] (3) For surrounding rock with a grade less than IV, the present invention provides a shotcrete and anchor support between the outer reinforcement and the inner reinforcement for support and reinforcement; for surrounding rock with a grade greater than or equal to IV, a segment lining is provided between the outer reinforcement and the inner reinforcement for support and reinforcement, thereby enabling adaptive support and reinforcement for different surrounding rock environments and ensuring the stability of the tunnel in a weak surrounding rock environment. Attached Figure Description

[0029] Figure 1 is a schematic diagram of the tunnel support device;

[0030] Figure 2 is a schematic diagram of the temporary support structure arranged in a cross shape;

[0031] Figure 3 is a schematic diagram of the temporary support structure arranged in a grid pattern;

[0032] Figure 4 is a schematic diagram of the segment lining section;

[0033] Figure 5 is a schematic diagram of the shotcrete anchor support;

[0034] Figure 6 is a magnified view of part A in Figure 1.

[0035] Wherein: 1-bottom support; 2-top support; 3-temporary support; 11-bottom arch support; 12-side wall support; 13-drainage cavity; 21-arch crown support; 22-external reinforcement; 23-internal reinforcement; 24-segment lining; 25-sprayed and anchored support; 31-horizontal temporary support; 32-vertical temporary support. Detailed Implementation

[0036] Example 1:

[0037] This embodiment of a short-span tunnel support device in a weak surrounding rock environment, as shown in Figure 1, includes a bottom support 1 and a top support 2 disposed on top of the bottom support 1. The bottom support 1 includes a bottom arch support 11 corresponding to the bottom arch of the tunnel, side wall supports 12 corresponding to the left and right side walls of the tunnel, and a drainage cavity 13 disposed inside the side wall supports 12. The bottom of the side wall supports 12 is connected to the end of the bottom arch support 11 by prestressed steel cables. One side of the drainage cavity 13 faces away from the tunnel. A water guide pipe is provided in the direction of the tunnel; the top support 2 includes an arch support 21 corresponding to the tunnel arch and a shoulder support. The arch support 21 is linearly spaced along the tunnel axis on the top of the side wall support 12 on the left and right sides. An outer reinforcement 22 is provided on the side of the arch support 21 closest to the surrounding rock, and an inner reinforcement 23 is provided on the side of the arch support 21 away from the surrounding rock. A segment lining 24 or a shotcrete support 25 is provided between the outer reinforcement 22 and the inner reinforcement 23 according to the surrounding rock grade.

[0038] The sidewall support 12 is a precast reinforced concrete component, with a drainage chamber 13 and a water pipe inside. The bottom arch support 11 can be a precast reinforced concrete component or directly cast concrete at the bottom arch of the tunnel. Before tunnel excavation, the tunnel is first pre-grouted. Grouting pipes are pre-installed at the tunnel arch and sidewall locations, and grouting reinforcement is carried out. After grouting reinforcement, the tunnel is excavated in progressive steps, with a unit length of 0.5m-1.0m. Excavation is carried out in the order of upper, middle, and lower layers, with central soil reserved when excavating the upper soil layer. After the upper soil layer is excavated, a waterproof layer is applied at the tunnel arch location, and then a top support is constructed to support the arch, with temporary support provided for the top support. Then, the upper central soil and middle soil layers are excavated. After the middle soil layer is excavated, a waterproof layer is applied to the corresponding tunnel sidewalls. Then, side supports are installed to support the tunnel sidewalls, and temporary supports are also applied to the side supports. Then, the lower soil layer is excavated. After the lower soil layer is excavated, a waterproof layer is applied to the tunnel bottom arch. Then, the side supports are connected to the top supports to form a support structure.

[0039] Then, soil is excavated on both sides of the tunnel to bury the sidewall support 12. The bottom of the sidewall support 12 is connected to the end of the bottom arch support 11 by prestressed steel cables to maintain the stability of the sidewall support 12. Then, anchor rods are driven into the sidewall support 12 towards the surrounding rock for reinforcement.

[0040] After the bottom support 1 is completed, an outer reinforcement 22 can be constructed between the tops of the side wall supports 12 on both the left and right sides. The outer reinforcement 22 can be a precast reinforced concrete component, or it can be constructed by symmetrically pouring concrete in sections on both sides in the direction from the shoulder to the arch. After the outer reinforcement 22 is completed, an arch support 21 can be constructed linearly at intervals along the tunnel axis on the inner side of the outer reinforcement 22, with the spacing between adjacent arch support 21 being less than or equal to 0.5m.

[0041] Depending on the surrounding rock grade, segment lining section 24 or shotcrete and anchor support section 25 are constructed between adjacent arch support sections 21. Specifically, as shown in Figure 5, when the surrounding rock grade is less than IV, shotcrete and anchor support section 25 is constructed; as shown in Figure 4, when the surrounding rock grade is greater than or equal to IV, segment lining section 24 is constructed. Segment lining section 24 or shotcrete and anchor support section 25 is connected to arch support section 21 via a connecting steel cage. Then, an inner reinforcement section 23 can be constructed on the inner side of the arch support section 21 to achieve support and reinforcement for the tunnel arch and shoulder.

[0042] Furthermore, an outer waterproof layer is provided between the outer reinforcement part 22 and the arch support part 21, and an inner waterproof layer is provided between the inner reinforcement part 23 and the arch support part 21.

[0043] Example 2:

[0044] This embodiment is a further optimization based on the above embodiment 1. A plurality of connecting anchor rods are provided circumferentially between the inner reinforcement part 23 and the outer reinforcement part 22. An opening for the connecting anchor rods to pass through is provided on the arch support part 21. A connecting anchor plate is provided between the free ends on the left and right sides of the inner reinforcement part 23 and the outer reinforcement part 22. The connecting anchor plate is anchored to the top of the side wall support part 12.

[0045] The included angle between adjacent connecting anchor rods is less than or equal to 30°. Openings for the connecting anchor rods to pass through are provided in the inner reinforcement part 23, the outer reinforcement part 22, and the arch support part 21 of the connecting anchor rods. A grouting port communicating with the opening is provided on one side of the opening. After the connecting anchor rod is driven into the surrounding rock through the opening for installation, grouting is performed to reinforce the opening through the grouting port.

[0046] The other parts of this embodiment are the same as those in Embodiment 1, so they will not be described again.

[0047] Example 3:

[0048] This embodiment is a further optimization based on the above embodiment 1 or 2. As shown in Figure 6, the left and right ends of the bottom arch support 11 are provided with pressure-bearing inclined surfaces, and the bottom end of the side wall support 12 is provided with a compression inclined surface that squeezes the pressure-bearing inclined surface toward the center of the tunnel. The compression inclined surface and the pressure-bearing inclined surface are connected by prestressed steel cables.

[0049] The inclination angle of the pressure-bearing slope is 30°-45°, and at least one set of prestressed steel cables is installed on the pressure-bearing slope. The compression slopes at the bottom ends of the left and right sidewall support parts 12 simultaneously compress the pressure-bearing slopes at the ends of the bottom arch support parts 11 towards the tunnel center, thereby subjecting the left and right sidewall support parts 12 to symmetrical reaction forces, enabling the sidewall support parts 12 to provide stable support for the surrounding rock of the sidewalls.

[0050] Furthermore, a horizontal connecting anchor is installed between the sidewall support 12 and the surrounding rock. An opening for the horizontal connecting anchor to pass through is provided on the side of the sidewall support 12 closest to the surrounding rock, and a grouting port communicating with the opening is provided on one side of the opening. After the horizontal connecting anchor is driven into the surrounding rock through the opening for installation, grout is injected into the opening for reinforcement.

[0051] The top, middle and bottom of the drainage chamber 13 on the side away from the tunnel are respectively provided with water guide pipes extending into the surrounding rock, and a gravel filter layer is provided at the end of the water guide pipe extending into the surrounding rock.

[0052] The other parts of this embodiment are the same as those in Embodiment 1 or 2 above, so they will not be described again.

[0053] Example 4:

[0054] This embodiment is a further optimization based on any one of the above embodiments 1-3, and also includes a temporary support 3 set inside the tunnel. The temporary support 3 includes a horizontal temporary support 31 and a vertical temporary support 32. The horizontal temporary support 31 is set horizontally between the side wall support 12 on the left and right sides or horizontally inside the inner reinforcement 23. The vertical temporary support 32 is set vertically between the inner reinforcement 23 and the bottom arch support 11.

[0055] As shown in Figure 2, for tunnels with a tunnel end span of less than or equal to 6.5m and a surrounding rock grade of greater than or equal to V, a set of vertical temporary support members 32 and a set of horizontal temporary support members 31 are set up inside the tunnel to form a cross-shaped temporary support structure.

[0056] As shown in Figure 3, for tunnels with a tunnel end span greater than 6.5m and a surrounding rock grade greater than or equal to V, two sets of vertical temporary support components 32 and two sets of horizontal temporary support components 31 are set inside the tunnel to form a grid-shaped temporary support structure.

[0057] By setting up temporary support sections 3 inside the tunnel, temporary support can be provided for the tunnel with a large cross-sectional span, thus avoiding the problem of loosening of the surrounding rock when the bottom support section 1 and the top support section 2 are constructed.

[0058] The other parts of this embodiment are the same as any one of the embodiments 1-3 above, so they will not be described again.

[0059] Example 5:

[0060] A method for supporting short-span tunnels in weak surrounding rock environments, based on the support device for short-span tunnels in weak surrounding rock environments described in any one of Examples 1-4, includes the following steps:

[0061] Step 1: Inspect the quality of the surrounding rock around the tunnel and determine the rock grade;

[0062] Step 2: Excavate the tunnel soil along the excavation line and use arch frames to pre-support the excavated part of the tunnel;

[0063] Step 3: Reinforce the bottom arch and sidewalls of the tunnel by inserting pipes and grouting. After the reinforcement is completed, construct the bottom arch support 11 corresponding to the bottom arch of the tunnel, and then construct reinforcement anchors between the bottom arch support 11 and the surrounding rock at the bottom of the tunnel.

[0064] Step 4: Prefabricate drainage cavity 13 and water pipe inside sidewall support 12. Then, using bottom arch support 11 as the construction foundation, construct sidewall support 12 on the left and right sides of the tunnel through prestressed steel cables. Reinforce the sidewall support 12 with horizontal connecting anchor rods between the sidewall support 12 and the surrounding rock of the tunnel sidewall. Detect the pre-pressure of the bottom arch support 11 on the sidewall support 12.

[0065] Step 5: Grouting reinforcement is carried out on the arch shoulder and arch crown of the tunnel. After the reinforcement is completed, an external reinforcement part 22 is constructed between the top of the side wall support part 12 on the left and right sides of the tunnel arch shoulder and the arch crown. Then, based on the external reinforcement part 22, an arch crown support part 21 is constructed linearly at intervals along the tunnel axis on the side of the external reinforcement part 22 away from the surrounding rock. The arch crown support part 21 is connected to the external reinforcement part 22 by connecting ring bars. Then, an external waterproof layer is constructed between the external reinforcement part 22 and the arch crown support part 21.

[0066] Step 6: If the surrounding rock grade is less than IV, spray anchors are directly used to form a spray anchor support 25 between adjacent arch support sections 21; if the surrounding rock grade is greater than or equal to IV, segment lining section (24) is directly constructed between adjacent arch support sections 21, and ring reinforcement is used to connect segment lining section 24 with external reinforcement section 22.

[0067] Step 7: Apply an inner waterproof layer on the side of the arch support 21 away from the surrounding rock. Then, relying on the outer reinforcement 22, apply an inner reinforcement 23 between the tops of the side wall support 12 on both sides. Then, apply connecting anchors circumferentially between the inner reinforcement 23 and the outer reinforcement 22.

[0068] Furthermore, if the cross-sectional width of the tunnel is greater than or equal to 6.5m, then after the construction of the outer reinforcement 22 and before the construction of the inner reinforcement 23, a temporary support 3 is constructed on the inner side of the tunnel; if the surrounding rock grade is less than V, then the temporary support 3 includes a set of horizontal temporary support members 31 and a set of vertical temporary support members 32 forming a cross-shaped support structure; if the surrounding rock grade is greater than or equal to V, then the temporary support 3 includes at least two sets of horizontal temporary support members 31 and at least two sets of vertical temporary support members 32.

[0069] Furthermore, after the inner reinforcement section 23 is constructed, the connecting section of the horizontal temporary support member 31 extending into the side wall support section 12 or the inner reinforcement section 23 is retained, and the support section of the horizontal temporary support member 31 extending into the tunnel is cut off; the connecting section of the vertical temporary support member 32 extending into the inner reinforcement section 23 or the bottom arch support section 11 is retained, and the support section of the vertical temporary support member 32 extending into the tunnel is cut off.

[0070] Furthermore, before applying the external waterproofing layer, the surrounding rock around the tunnel is pre-anchored for drainage.

[0071] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for supporting short-span tunnels in weak surrounding rock environments, wherein the support device for implementing the method includes a bottom support (1) and a top support (2) disposed above the bottom support (1), characterized in that, The bottom support (1) includes a bottom arch support (11) corresponding to the bottom arch of the tunnel, side wall supports (12) corresponding to the left and right side walls of the tunnel, and a drainage cavity (13) inside the side wall support (12). The bottom of the side wall support (12) is connected to the end of the bottom arch support (11) by prestressed steel cables. A water guide pipe is provided on one side of the drainage cavity (13) facing away from the tunnel. The top support (2) includes an arch support (21) corresponding to the arch top and arch shoulder of the tunnel. The arch support (21) is linearly spaced along the tunnel axis and is provided with the side wall supports (11) on the left and right sides. 2) At the top, the arch support (21) is provided with an outer reinforcement (22) on the side close to the surrounding rock, and an inner reinforcement (23) on the side away from the surrounding rock. The outer reinforcement (22) and the inner reinforcement (23) are provided with a segment lining (24) or a shotcrete support (25) between them according to the surrounding rock grade. The left and right ends of the bottom arch support (11) are provided with pressure-bearing inclined surfaces, and the bottom end of the side wall support (12) is provided with a compression inclined surface that squeezes the pressure-bearing inclined surface toward the center of the tunnel. The compression inclined surface and the pressure-bearing inclined surface are connected by prestressed steel cables. It also includes a temporary support (3) set inside the tunnel. The temporary support (3) includes a horizontal temporary support (31) and a vertical temporary support (32). The horizontal temporary support (31) is set horizontally between the side wall support (12) on the left and right sides or horizontally inside the inner reinforcement (23). The vertical temporary support (32) is set vertically between the inner reinforcement (23) and the bottom arch support (11). The support method includes the following steps: Step 1, detect the quality of the surrounding rock around the tunnel and determine the surrounding rock grade; Step 2, excavate the tunnel soil along the excavation line, and use the side wall support (12) and arch frame to pre-support the excavated part of the tunnel; Step 3 Step 1: The bottom arch and side walls of the tunnel are reinforced by grouting. After the reinforcement is completed, the bottom arch support (11) is constructed in the corresponding bottom arch of the tunnel. Then, reinforcement anchors are installed between the bottom arch support (11) and the surrounding rock at the bottom of the tunnel. Step 4: The side wall support (12) is a prefabricated component with a drainage cavity (13) and a water pipe inside. Then, the bottom arch support (11) is used as the construction foundation. The side wall support (12) is constructed in the corresponding side walls on the left and right sides of the tunnel through prestressed steel cables. Horizontal connecting anchors are installed between the side wall support (12) and the surrounding rock of the tunnel side wall for reinforcement. The pre-pressure of the bottom arch support (11) on the side wall support (12) is detected.Step 5: Grouting reinforcement is performed on the arch shoulder and arch crown of the tunnel. After reinforcement, an external reinforcement part (22) is constructed between the tops of the sidewall support parts (12) on both sides of the tunnel arch shoulder and arch crown. Then, based on the external reinforcement part (22), an arch crown support part (21) is constructed linearly at intervals along the tunnel axis on the side of the external reinforcement part (22) away from the surrounding rock. The arch crown support part (21) is connected to the external reinforcement part (22) by connecting ring bars. Then, an external waterproof layer is constructed between the external reinforcement part (22) and the arch crown support part (21). Step 6: If the surrounding rock grade is less than IV, spray anchors are directly applied between adjacent arch support sections (21) to form a spray anchor support section (25); if the surrounding rock grade is greater than or equal to IV, segment lining section (24) is directly applied between adjacent arch support sections (21), and ring reinforcement is used to connect the segment lining section (24) with the outer reinforcement section (22); Step 7: An inner waterproof layer is applied on the side of the arch support section (21) away from the surrounding rock, and then, relying on the outer reinforcement section (22), an inner reinforcement section is applied between the tops of the side wall support sections (12) on the left and right sides. 23), and then anchor bolts are installed circumferentially between the inner reinforcement (23) and the outer reinforcement (22) and anchored into the rock wall; if the cross-sectional width of the tunnel is greater than or equal to 6.5m, then after the outer reinforcement (22) is installed and before the inner reinforcement (23) is installed, a temporary support (3) is installed on the inner side of the tunnel; if the surrounding rock grade is greater than or equal to V, then the temporary support (3) includes a set of horizontal temporary support components (31) and a set of vertical temporary support components (32) forming a cross-shaped support structure; if the surrounding rock grade is greater than or equal to V and is located in the tunnel entrance area, then the temporary support (3) (3) Includes at least two sets of horizontal temporary supports (31) and at least two sets of vertical temporary supports (32); after the inner reinforcement (23) is constructed, the connecting sections of the horizontal temporary supports (31) extending into the sidewall support (12) or the inner reinforcement (23) are retained, and the support sections of the horizontal temporary supports (31) extending into the tunnel are cut off; the connecting sections of the vertical temporary supports (32) extending into the inner reinforcement (23) or the bottom arch support (11) are retained, and the support sections of the vertical temporary supports (32) extending into the tunnel are cut off.

2. The method for supporting short-span tunnels in weak surrounding rock environments according to claim 1, characterized in that, An outer waterproof layer is provided between the outer reinforcement part (22) and the arch support part (21), and an inner waterproof layer is provided between the inner reinforcement part (23) and the arch support part (21).

3. The method for supporting short-span tunnels in weak surrounding rock environments according to claim 2, characterized in that, A number of anchor rods are provided circumferentially between the inner reinforcement part (23) and the outer reinforcement part (22) and anchored into the rock wall. An opening is provided on the arch support part (21) for the connecting anchor rods to pass through. A connecting anchor plate is provided between the free ends on the left and right sides of the inner reinforcement part (23) and the outer reinforcement part (22). The connecting anchor plate is anchored to the top of the side wall support part (12).

4. The method for supporting short-span tunnels in weak surrounding rock environments according to claim 1, characterized in that, The drainage chamber (13) is provided with water pipes extending into the surrounding rock at the top, middle and bottom of the side away from the tunnel. A gravel filter layer is provided at the end of the water pipe extending into the surrounding rock.

5. The method for supporting short-span tunnels in weak surrounding rock environments according to claim 1, characterized in that, Before applying the external waterproofing layer, the surrounding rock around the tunnel is pre-anchored for drainage.

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