A method for slope support at the tunnel entrance

Abstract

This invention discloses a method for slope protection at the tunnel entrance, belonging to the field of tunnel entrance protection technology. The method includes: setting up a first support along the longitudinal direction on the tunnel's slope section; setting up a second support connected to the first support along the transverse direction on the tunnel's slope section; extending the tunnel opening to cover the first and second supports; backfilling the upper part of the extended tunnel with sand to cover the first and second supports; through the established slope protection structure, the first and second supports are combined with the tunnel opening extension and backfill counterpressure for comprehensive support. After grouting, the first and second supports and the concrete form an integrated structure, effectively improving slope stability and ensuring safe tunnel construction; the extension of the tunnel combined with sand backfill counterpressure reduces the impact of slope disasters such as rockfalls and provides a certain degree of protection for the first and second supports.

Description

Technical Field

[0001] This invention relates to the field of tunnel entrance protection technology, specifically to a method for slope support at the tunnel entrance section. Background Technology

[0002] The slope at the tunnel entrance is most vulnerable to natural disasters and is also the most prone to landslides and other accidents. The terrain at the tunnel entrance is complex, with steep slopes and numerous dangerous rocks and boulders on the tunnel roof. To ensure safe tunnel construction and subsequent safe operation, it is necessary to support the dangerous slopes at the tunnel entrance.

[0003] Currently, the common type of slope protection for tunnel entrances is a combination of shotcrete, anchor bolts, and steel mesh support structures. For dangerous slopes with poor stability and steep inclines, numerous cracks often appear, compromising construction safety. Furthermore, steep tunnel slopes are prone to rockfalls, posing a safety hazard to vehicles entering the tunnel. Summary of the Invention

[0004] To address the problems of existing technologies, this invention provides a method for slope support at the tunnel entrance, comprising:

[0005] Along the longitudinal direction, several first supports are installed on the slope section of the tunnel, and the height of the first supports extends at least to the bottom of the open tunnel.

[0006] Along the transverse direction, several second supports connected to the first support are installed on the tunnel slope section for reinforcement;

[0007] Extend the open tunnel so that the extended open tunnel can be shielded from the installation of the first and second supports along the tunnel extension direction;

[0008] Backfill the top of the extended section of the tunnel with sand to cover the first and second supports.

[0009] Furthermore, the spacing between adjacent first supports is 0.4mm-0.6mm.

[0010] Furthermore, the first support structure includes:

[0011] Along the longitudinal direction, multiple first boreholes are drilled on the slope section of the tunnel, and the drilled first boreholes are cleaned.

[0012] The first support is inserted into each first borehole and grout is injected into each first support.

[0013] Furthermore, the first support is a hollow steel pipe with a thickness of 35mm-37mm and a diameter of 168-172mm. The top of the steel pipe is located 2.5m-3.5m below the opening.

[0014] Furthermore, the second support includes:

[0015] Multiple second boreholes are drilled along the transverse direction, corresponding to the location of the first borehole, and the second boreholes respectively pass through each of the first supports;

[0016] A second support is installed in each second borehole, and grout is injected into each second support.

[0017] Furthermore, the second support includes: grouting anchor bolts, I-beams, and angle steel supports;

[0018] One end of the grouting anchor rod passes through the first support, and an anchor is provided at the other end of the grouting anchor rod;

[0019] A gap is left between the anchor and the first support;

[0020] The I-beam is provided between the anchor and the first support.

[0021] Furthermore, a pad is provided between the I-beam and the anchor, and an angle steel support is provided between the I-beam and the first support.

[0022] Furthermore, the grouting anchor bolt has four layers, namely the first layer anchor bolt, the second layer anchor bolt, the third layer anchor bolt, and the fourth layer anchor bolt;

[0023] The first layer of anchor bolts consists of the uppermost anchor bolts on each first support. The first layer of anchor bolts is inclined upwards, and the angle between the first layer of anchor bolts and the horizontal direction is 10°.

[0024] The second layer of anchors, the third layer of anchors, and the fourth layer of anchors are located below the first layer of anchors in sequence, and are respectively set horizontally.

[0025] Furthermore, the spacing between adjacent anchors in the first layer of anchors and the spacing between adjacent anchors in the third layer of anchors are both 2m.

[0026] The spacing between adjacent anchors in the second layer of anchors and the spacing between adjacent anchors in the fourth layer of anchors are both 1.5m.

[0027] The length of the first layer of anchor bolts is 17m-19m;

[0028] The length of the second layer of anchor bolts is 9m-11m;

[0029] The length of the third layer of anchor bolts is 7m-9m;

[0030] The length of the fourth layer of anchors is 5m-7m.

[0031] Furthermore, after backfilling the upper part of the tunnel with sand, a layer of concrete is sprayed on the surface of the sand, and a drainage ditch is opened at the front end of the tunnel and on the uphill slope.

[0032] The beneficial effects of this invention are:

[0033] The slope protection structure provided in this application adopts a comprehensive support system combining the first and second supports with tunnel extension and backfill counterpressure. After grouting, the first and second supports and the concrete form an integrated structure, which can effectively improve slope stability and ensure the safety of tunnel construction. The extension of the tunnel combined with sand backfill counterpressure can reduce the impact of slope disasters such as rockfalls and provide a certain degree of protection for the first and second supports. At the same time, the entire support structure is coated with a concrete protective layer and a water interception ditch is set up, giving the entire structure good waterproof and seepage-resistant properties.

[0034] By combining the first and second supports with the backfilling of sand at the top of the tunnel, the project solved the problems of dangerous and difficult tunnel entrance construction, the instability of the tunnel entrance slope, and the occurrence of numerous cracks in the later stages after the implementation of common slope support measures.

[0035] This construction method enables comprehensive protection of steep slopes at tunnel entrances. It is applicable to the protection of dangerous slopes at various tunnel entrances, effectively improving slope stability and addressing risks and hidden dangers encountered during tunnel construction. Attached Figure Description

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the first support structure provided by the present invention;

[0038] Figure 2 This is a schematic diagram of the anchor bolt arrangement structure provided by the present invention;

[0039] Figure 3 This is a schematic diagram of the cross-sectional structure of the extended tunnel and backfill sand provided by the present invention;

[0040] Figure 4 This is a schematic diagram of the longitudinal section structure of the extended tunnel and backfill sand provided by the present invention;

[0041] Figure 5 This is a schematic diagram of the extended tunnel planar structure provided by the present invention;

[0042] Figure 6 This is a schematic diagram of the construction process provided by the present invention.

[0043] Attached diagram labels: 1 for micropile; 2 for grouting anchor; 21 for first-layer anchor; 22 for second-layer anchor; 23 for third-layer anchor; 24 for fourth-layer anchor; 3 for I-beam; 4 for anchorage; 5 for pad; 6 for angle steel support; 7 for grouting body; 8 for tunnel inside the slope; 9 for extended open tunnel; 10 for backfill sand; 11 for concrete; 12 for concrete sidewall; 13 for intercepting ditch; 14 for slope intercepting ditch. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0045] It should be noted that the support method designed in this application is applicable to support schemes for tunnel portal sections where the tunnel slope stability is poor and conventional support methods cannot meet safety requirements, as well as for problems such as excessive slope of the tunnel portal section and poor strength of the slope rock and soil.

[0046] See Figures 1 to 6 A method for slope support at the tunnel entrance, comprising:

[0047] Along the longitudinal direction, the first support 1 is installed on the tunnel slope section for reinforcement:

[0048] The first support is provided in multiple ways, with the spacing between adjacent first supports being 0.4mm-0.6mm, preferably 0.5m. They are evenly distributed on the slope along the tunnel direction, and adjacent steel pipes are connected by sleeve welding.

[0049] The first support includes:

[0050] Along the longitudinal direction, multiple first boreholes are drilled on the tunnel slope section, and the drilled first boreholes are cleaned; the first support is inserted into each first borehole, and grout is injected into each first support.

[0051] The first support is a hollow steel pipe with a thickness of 35mm-37mm, preferably 36mm, and a diameter of 168-172mm, preferably 170mm. The top of the steel pipe is located 2.5m-3.5m below the opening, preferably 3m.

[0052] The first borehole has a diameter of 24cm. After the steel pipe is inserted, C30 cement mortar with a water-cement ratio of less than or equal to 0.5 is poured in. The grouting is done in one go, and the grouting pressure is 1-3Mpa. After the grouting is completed, a cap beam with a cross section of 400mm×400mm is set at the upper end of the steel pipe.

[0053] Along the transverse direction, a second support connected to the first support 1 is installed on the tunnel slope section for reinforcement:

[0054] The second support system includes:

[0055] Multiple second boreholes with a diameter of 80 mm are drilled along the transverse direction, corresponding to the location of the first borehole, and the second boreholes pass through each of the first supports respectively;

[0056] A second support is installed in each second borehole, and grout is injected into each second support.

[0057] The second support includes: grouting anchor bolts, I-beams, and angle steel supports;

[0058] One end of the grouting anchor rod passes through the first support, and an anchor is provided at the other end of the grouting anchor rod; wherein, the diameter of the grouting anchor rod is 40mm;

[0059] A gap is left between the anchor and the first support;

[0060] The I-beam is provided between the anchor and the first support;

[0061] A pad is provided between the I-beam and the anchor, and an angle steel support is provided between the I-beam and the first support.

[0062] The I-beams are fixed to 40×5 angle steel, and the base plate, I-beams, anchors and angle steel supports are all connected by welds.

[0063] See Figure 1 The pad and I-beam are fixed to the first support, and the other end of the I-beam is fixed by the angle steel bracket. After the anchor bolts are installed, grouting is performed to form the grout body 7.

[0064] See Figures 2 to 3 The grouting anchor 2 is driven into the tunnel 8 inside the slope. The grouting anchor has four layers, namely the first layer anchor, the second layer anchor, the third layer anchor and the fourth layer anchor.

[0065] The first layer of anchor bolts consists of the uppermost anchor bolts on each first support. The first layer of anchor bolts is inclined upwards, and the angle between the first layer of anchor bolts and the horizontal direction is 10°.

[0066] The second layer of anchors, the third layer of anchors, and the fourth layer of anchors are located below the first layer of anchors in sequence, and are respectively set horizontally.

[0067] The spacing between adjacent anchors in the first layer of anchors and the spacing between adjacent anchors in the third layer of anchors are 2m each, and 20 of each are provided.

[0068] The spacing between adjacent anchors in the second layer of anchors and the spacing between adjacent anchors in the fourth layer of anchors are both 1.5m.

[0069] The length of the first layer of anchor bolts is 17m-19m, preferably 18m;

[0070] The length of the second layer of anchor bolts is 9m-11m, preferably 10m;

[0071] The length of the third layer of anchor bolts is 7m-9m, preferably 8m;

[0072] The length of the fourth layer of anchor bolts is 5m-7m, preferably 6m;

[0073] The first layer of anchor bolts is driven into the tunnel arch. After the anchor bolts are installed, C30 cement grout is injected at a pressure of not less than 1 to 2.5 MPa.

[0074] See Figure 4 Extend the open tunnel 9 to the rear side of the entrance of the inner tunnel 8 on the slope, so as to cover the first support 1 and the second support. Then, backfill the upper part of the extended open tunnel 9 with sand 10 to cover the first support 1 and the second support.

[0075] The tunnel is extended by approximately 40 meters, covering the entire first and second support structures, and the extended portion is designed identically to the original tunnel.

[0076] The entire process is as follows: the invert arch of the extended tunnel is constructed, then the tunnel is lined, followed by the installation of a waterproof layer for the tunnel, then backfilling of the tunnel top after the lining strength reaches the design strength, then spraying concrete and reinforcing mesh on the outer and upper edges after backfilling, and finally constructing a drainage ditch in front of the backfill section.

[0077] The upper part of the extended tunnel 9 is backfilled with sand 10 for counter-pressure. The outer sidewall 12 of the extended tunnel is constructed with concrete 11 with a surface slope of about 18%. A water interception ditch 13 is set on the upper side of the sand backfill near the tunnel entrance, and a slope water interception ditch 14 is opened on the slope.

[0078] Figure 5 This is a schematic diagram of the extended open-cut tunnel in this application. The original tunnel entrance section is located on a natural steep slope, and there is a risk of landslides and rockfalls between the two entrances. The constructed support system enhances the stability of the tunnel slope and ensures the safety of the natural slope. The extended open-cut tunnel not only avoids the risk of rockfalls but also protects both the support system and the natural slope. The backfill counterweight protects the safety of the extended tunnel section, while the sprayed concrete and drainage ditches on its upper side provide excellent waterproofing and impermeability as part of the overall support structure.

[0079] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for slope support at the tunnel entrance, characterized in that, Includes the following steps: Along the longitudinal direction, several first supports are installed on the tunnel slope section. The first supports are hollow steel pipes, and the installation height of the first supports extends at least to the bottom of the open tunnel. Along the transverse direction, several second supports connected to the first support are installed on the tunnel slope section for reinforcement; Extend the open tunnel so that the extended open tunnel can be shielded from the installation of the first and second supports along the tunnel extension direction; Backfill the top of the extended section of the tunnel with sand to cover the first and second supports; The first support structure includes: Along the longitudinal direction, multiple first boreholes are drilled on the slope section of the tunnel, and the drilled first boreholes are cleaned. The first support is inserted into each first borehole, and grout is injected into each first support. The second support system includes: Multiple second boreholes are drilled along the transverse direction, corresponding to the location of the first borehole, and the second boreholes respectively pass through each of the first supports; Install a second support in each second borehole and grout into each second support; The second support includes: grouting anchor bolts, I-beams, and angle steel supports; One end of the grouting anchor rod passes through the first support, and an anchor is provided at the other end of the grouting anchor rod; A gap is left between the anchor and the first support; The I-beam is provided between the anchor and the first support; The grouting anchor bolts are configured in four layers: the first layer anchor bolt, the second layer anchor bolt, the third layer anchor bolt, and the fourth layer anchor bolt. The first layer of anchor bolts consists of the uppermost anchor bolts on each first support. The first layer of anchor bolts is inclined upwards, and the angle between the first layer of anchor bolts and the horizontal direction is 10°. The second layer of anchors, the third layer of anchors, and the fourth layer of anchors are located below the first layer of anchors in sequence, and are respectively set horizontally.

2. The method for slope support at the tunnel entrance section according to claim 1, characterized in that, The distance between adjacent first supports is 0.4m-0.6m.

3. The method for slope support at the tunnel entrance section according to claim 1, characterized in that, The steel pipe has a thickness of 35mm-37mm and a diameter of 168-172mm. The bottom of the steel pipe is located 2.5m-3.5m below the open tunnel.

4. The method for slope support at the tunnel entrance section according to claim 1, characterized in that, A pad is provided between the I-beam and the anchor, and an angle steel support is provided between the I-beam and the first support.

5. The method for slope support at the tunnel entrance section according to claim 1, characterized in that, The spacing between adjacent anchors in the first layer of anchors and the spacing between adjacent anchors in the third layer of anchors are both 2m. The spacing between adjacent anchors in the second layer of anchors and the spacing between adjacent anchors in the fourth layer of anchors are both 1.5m. The length of the first layer of anchor bolts is 17m-19m; The length of the second layer of anchor bolts is 9m-11m; The length of the third layer of anchor bolts is 7m-9m; The length of the fourth layer of anchors is 5m-7m.

6. The method for slope support at the tunnel entrance section according to claim 1, characterized in that, After the upper part of the extended tunnel is backfilled with sand, a layer of concrete is sprayed on the surface of the sand, and drainage ditches are opened at least at the front end of the tunnel and on the uphill slope.

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