Concrete temporary platform grouting steel pipe reinforced tunnel entering structure for complex gully terrain

Abstract

The invention relates to a complex gully terrain concrete temporary platform grouting steel pipe reinforcement tunnel entering structure, a cover arch is arranged at a hidden hole entering position of an entrance side slope line of a single-hole bidirectional tunnel, temporary side slopes are formed on two sides of the cover arch, and anchor-shotcrete supports and intercepting ditches are arranged on the temporary side slopes. The method has the beneficial effects that the tunnel entering local cover excavation construction technology is adopted, the cover arch is constructed to backfill the ecological slope protection in a back pressure mode, and the problems of shallow burying and exposing of the gully section and the ecological slope protection are solved; a hole body drilling and grouting reinforcement technology at the tunnel entering position is adopted, disturbance of a large-crack rock mass above the tunnel top is reduced, tunnel reinforcement is conducted between an excavation contour line and a grouting reinforcement boundary through partition grouting, the integrity of the rock mass in construction is guaranteed, and potential safety hazards are eliminated.

Description

Technical Field

[0001] The invention belongs to the field of tunnel entry construction, and in particular relates to a tunnel entry structure reinforced with grouting steel pipes on a temporary concrete platform on complex gully terrain. Background Art

[0002] With the development of highway engineering construction, tunnel excavation in mountainous areas is becoming more and more frequent. Affected by gullies, the bearing capacity of the foundation is reduced, some sections of the tunnel are exposed, the terrain is severely biased, and there are large cracks in the rock above the top of the tunnel. The construction at the tunnel entrance will cause disturbance of the rock mass, making it difficult to ensure the integrity of the rock mass, and posing a great safety hazard.

[0003] To sum up, for the construction of concrete temporary platform grouting steel pipe reinforced tunnel entrance structure on complex gully terrain, it is very important to seek a complex gully terrain concrete temporary platform grouting steel pipe reinforced tunnel entrance structure with fast construction speed, simple operation, reliable construction quality and high safety level and its construction method. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a grouting steel pipe reinforced tunnel entrance structure for a temporary concrete platform on complex gully terrain.

[0005] This kind of concrete temporary platform grouting steel pipe reinforced tunnel entrance structure for complex gully terrain has a single-hole bidirectional tunnel with a sleeve arch at the entrance of the blind tunnel on the entrance slope line, and temporary slopes are formed on both sides of the sleeve arch. Anchor spraying support and intercepting ditches are provided on the temporary slope; the excavation contour line of the single-hole bidirectional tunnel is located below the sleeve arch, and a grouting wall is cast at the entrance of the single-hole bidirectional tunnel. An initial support is provided on the inner side of the sleeve arch, and the initial support fixes the steel formwork connected to the grouting wall;

[0006] A grouting orifice pipe is pre-buried in the grouting wall, which is used to drill holes and insert grouting pipes from the entrance position of a single-hole bidirectional tunnel. The grouting pipes are obliquely inserted into the soil outside the excavation contour line along the entrance direction for grouting reinforcement.

[0007] Preferably, the gullies on the entrance slope line are provided with partial gully backfill, and a cushion layer is cast on the arch construction platform; the anchor spraying support includes anchor rods and concrete, and intercepting ditches are provided on the slopes above the anchor spraying support on both sides.

[0008] Preferably, a small conduit is drilled in the temporary slope along the tangent direction at the arch foot of the sleeve arch, a grouting body is formed at the bottom end of the small conduit, and a reserved deformation amount is provided between the sleeve arch and the single-hole bidirectional tunnel lining at the bottom.

[0009] Preferably, the slurry stop wall includes a rock-embedded section, which is embedded in the surrounding rock outside the excavation contour line, and grouting orifice pipes are pre-buried around the slurry stop wall; pre-embedded screw barrels are provided at the top and bottom of the initial support, and the slurry stop wall formwork is a steel formwork; a square steel frame is welded and connected to the back of the steel formwork, wherein the square steel frame includes several segments, and ear plates are provided at the ends of the square steel frame segments, and the ear plates of the upper and lower adjacent steel formwork segments are fixedly connected by bolts; an upper cross bar and a lower cross bar are respectively welded to the top and bottom of the square steel frame, and the upper cross bar and the lower cross bar are fixed to the pre-embedded screw barrels provided for the initial support by screws; the steel formwork is provided with reserved holes according to the position of the grouting orifice pipe.

[0010] Preferably, steel pipe piles are driven under the invert of the single-hole bidirectional tunnel entrance, grouting bodies are provided on the outside of the steel pipe piles as the tunnel entrance foundation reinforcement structure, and the tops of the steel pipe piles are welded to the single-hole bidirectional tunnel invert steel cage; sidewalks, pavements, cable trenches, side ditches and central drainage ditches are constructed in the single-hole bidirectional tunnel.

[0011] Preferably, the upper part of the sleeve arch is provided with foam concrete, a waterproof layer, backfill soil and ecological slope protection in sequence.

[0012] The construction method of the grouting steel pipe reinforced tunnel entrance structure of the temporary concrete platform on complex gully terrain includes the following steps:

[0013] Step 1: construct an arch construction platform; construct anchor spraying support for the temporary slope and set up a water intercepting ditch on its upper part;

[0014] Step 2: construct grouting at the arch foot and pour concrete arch;

[0015] Step 3: Use steel formwork to construct grout-stopping walls in sections within the arch and pre-embed grouting orifice pipes;

[0016] Step 4: Drill holes at the entrance of a single-hole bidirectional tunnel through a grouting orifice pipe, and use zoned grouting to reinforce the tunnel;

[0017] Step 5: Drive steel pipe piles under the invert of the single-hole bidirectional tunnel entrance and inject grout to form a grouting body to reinforce the foundation of the single-hole bidirectional tunnel entrance.

[0018] Preferably, after the reinforcement cage of the slurry-stopping wall is tied, the steel formwork is supported in sections from bottom to top and the slurry-stopping wall is cast in sections. After the uppermost steel formwork is installed in sections, the upper support rod is installed. One end of the upper support rod is fixed to the square steel skeleton bolt, and the other end is fixed to the bottom of the initial support. A concrete grouting port and an air guide hole are provided on the uppermost steel formwork. The air guide hole is inserted to the top of the slurry-stopping wall. In step three, concrete construction is carried out on the upper part of the slurry-stopping wall through the concrete grouting port. When concrete flows out of the air guide hole, the concrete construction is stopped. During the process of supporting the steel formwork in sections, a grouting orifice pipe is simultaneously provided and sealed so that the grouting orifice pipe is pre-buried in the slurry-stopping wall.

[0019] Preferably, step four is to drill holes at the entrance positions of single-hole and bidirectional tunnels through the grouting orifice pipes pre-buried in the stop wall, and insert the grouting pipes from the grouting orifice pipes, and use zone grouting to reinforce the tunnel between the excavation contour line and the grouting reinforcement boundary, and perform zone grouting in reverse order from the position away from the stop wall to the direction close to the stop wall.

[0020] The beneficial effects of the present invention are:

[0021] 1) The present invention adopts the local cover excavation construction technology of tunnel entry, and constructs the arch counter-pressure backfill ecological slope protection, which solves the problems of shallow burial, exposure and ecological slope protection in the gully section.

[0022] 2) The present invention adopts the technology of drilling and grouting reinforcement of the tunnel body at the tunnel entrance position, which reduces the disturbance of the rock mass with large cracks above the tunnel top, and uses zoned grouting to reinforce the tunnel between the excavation contour line and the grouting reinforcement boundary, thereby ensuring the integrity of the rock mass during construction and eliminating safety hazards. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the cross-section of the grouting steel pipe reinforced tunnel entrance structure on a temporary concrete platform in complex gully terrain;

[0024] Figure 2 It is a schematic diagram of the cross-section of the temporary platform structure for gully backfilling and slope spray anchor support reinforcement;

[0025] Figure 3 This is a schematic diagram of the tunnel body drilling and grouting reinforcement at the tunnel entrance;

[0026] Figure 4 It is a schematic diagram of the cross section of the formwork of the stop wall;

[0027] Figure 5 This is a schematic diagram of the location of the upper steel formwork concrete grouting port;

[0028] Figure 6 This is a schematic diagram of the grouting reinforcement area of ​​the tunnel body at the entrance of the tunnel;

[0029] Figure 7 It is a schematic diagram of the cross section of a single-hole bidirectional tunnel after construction is completed.

[0030] Explanation of reference numerals: 1-entrance slope line, 2-single-hole bidirectional tunnel, 3-gully, 4-sidewalk, 5-pavement, 6-tunnel centerline, 7-cable trench, 8-side ditch, 9-central drainage ditch, 10-steel pipe pile, 11-grouting body, 12-intercepting ditch, 13-arch, 14-anchor spraying support, 15-sprayed concrete, 16-small guide tube, 17-anchor rod, 18-cushion, 19-arch construction platform, 20-local backfill of gully, 21-excavation contour line, 22- grouting pipe, 23- ear plate, 24- upper support rod, 25- lower support rod, 26- square steel frame, 27- steel formwork, 28- concrete grouting port, 29- air guide hole, 30- rock embedded section, 31- grouting wall, 32- grouting hole pipe, 33- upper cross bar, 34- lower cross bar, 35- screw, 36- embedded screw barrel, 37- initial support, 38- grouting reinforcement boundary, 39- backfill soil, 40- foam concrete, 41- waterproof layer, 42- ecological slope protection. DETAILED DESCRIPTION

[0031] The present invention is further described below in conjunction with embodiments. The description of the following embodiments is only used to help understand the present invention. It should be noted that for ordinary persons in the art, without departing from the principle of the present invention, the present invention can also be modified in some ways, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0032] Embodiment 1

[0033] As an example, Figures 1 to 7 As shown, this complex gully terrain concrete temporary platform grouting steel pipe reinforcement tunnel entrance structure includes: entrance slope line 1, single hole bidirectional tunnel 2, gully 3, sidewalk 4, road surface 5, tunnel center line 6, cable trench 7, side ditch 8, central drainage ditch 9, steel pipe pile 10, grouting body 11, intercepting ditch 12, arch 13, anchor spraying support 14, shotcrete 15, small guide tube 16, anchor rod 17, cushion layer 18, arch construction platform 19, gully bureau Backfill 20, excavation contour line 21, grouting pipe 22, ear plate 23, upper support rod 24, lower support rod 25, square steel frame 26, steel formwork 27, concrete grouting port 28, air guide hole 29, rock embedded section 30, grouting wall 31, grouting hole pipe 32, upper cross bar 33, lower cross bar 34, screw 35, embedded screw barrel 36, initial support 37, grouting reinforcement boundary 38, backfill soil 39, foam concrete 40, waterproof layer 41, ecological slope protection 42.

[0034] It involves gully backfilling and slope spray-anchor support reinforcement of temporary arch platform technology, arch partial cover excavation technology, rock-embedded grouting wall casting template technology, grouting hole pipe precise pre-embedding technology, grouting hole guide drilling technology, tunnel entrance foundation steel pipe pile grouting reinforcement technology, arch foam concrete backfill and ecological slope protection technology.

[0035] The gully backfilling and slope spraying anchor support reinforcement arch temporary platform technology first selects a suitable entry position of a single-hole bidirectional tunnel 2 on the entrance slope line 1, and determines the local cover excavation construction section of the tunnel; removes the covering layer of the gully 3, performs local gully backfilling 20 and leveling of the arch 13 construction platform, and pours a cushion layer 18; performs anchor spraying support 14 protection on the temporary slope, adopts the method of first driving anchor rods 17 and then spraying concrete 15, and sets a cut-off ditch 12 on the upper part thereof;

[0036] The technology of partially covering the arch and digging the hole is to set a small pipe 16 in the vertical direction of the arch foot of the arch 13 and perform grouting through a high-pressure grouting machine to form a grouting body 11, thereby improving the bearing capacity of the arch foot of the arch 13; the arch 13 is made of I-beams, and after the erection is completed, a small piece of standardized steel formwork is used to support the concrete arch 13, and a reserved deformation is set between the arch and the lower tunnel lining;

[0037] The rock-embedded grout-stopping wall casting template technology is that the grout-stopping wall 31 is cast with C30 concrete and has a thickness of 1m, wherein the rock-embedded section 30 is embedded in the surrounding rock by no less than 30cm, and a 3m long seamless steel pipe is pre-buried as a grouting orifice pipe during casting; the initial support 37 is provided with a pre-buried screw barrel 36 at the designed position of the grout-stopping wall 31; the template of the grout-stopping wall 31 adopts a segmented standardized steel template 27 system, and the steel template 27 is welded on a square steel skeleton 26, wherein the square steel skeleton 26 is The ear plate 23 is set, and the upper and lower segmental shaped steel templates 27 are connected by bolts to fix the ear plates 23; the upper cross bar 33 and the lower cross bar 34 are welded to the square steel frame 26, and are fixed to the embedded screw barrel 36 set by the initial support 37 through the screw 35; the steel template 27 is set with a reserved hole according to the position of the grouting orifice pipe 32; after the reinforcement cage of the grout-stopping wall 31 is tied, the shaped steel template 27 is supported in sections, and the lower steel template 27 is supported first, and the lower support rod 25 is fixed to the lower support rod 25. After the lower steel formwork is supported, one end is bolted to the ear plate 23 of the square steel frame 26, and the other end is fixed to the embedded screw barrel 36 set in the initial support 37 through the screw 35, and concrete is poured; then the middle steel formwork 27 is installed, and concrete is poured; finally, the upper steel formwork 27 is installed, and the upper support rod 25, after the upper steel formwork 27 is supported, one end is bolted to the ear plate 23 of the square steel frame 26, and the other end is fixed to the embedded screw barrel 36 set in the initial support 37 through the screw 35 is fixed, wherein a concrete grouting port 28 and an air guide hole 29 are arranged on the upper steel template 27, the air guide hole 29 is inserted into the top of the rock embedded section 30, and the upper concrete of the stop wall 31 is constructed through the concrete grouting port 28. When concrete flows out of the air guide hole 29, the concrete construction is stopped; after the segmented steel template 27 is supported, the grouting orifice pipe 32 is respectively inserted into the reserved hole position of the steel template 27 and sealed, so that the grouting orifice pipe 32 is pre-buried in the stop wall 31;

[0038] The grouting hole guide drilling technology is to drill holes at the entrance of the single-hole bidirectional tunnel 2 through the grouting hole pipe 32 pre-buried in the grouting wall 31, and use zone grouting to reinforce the tunnel, using 4 zones → 3 zones → 2 zones → 1 zones, and grouting in reverse order, wherein the area between the excavation contour line 21 and the grouting reinforcement boundary 38 is the reinforcement area;

[0039] like Figure 1 As shown, the steel pipe pile 10 is set at the foundation position of the tunnel entrance, and high-pressure grouting is performed to form a grouting body 11 to reinforce the foundation of the tunnel entrance, wherein the top of the steel pipe pile 10 is welded to the inverted arch steel cage of the single-hole bidirectional tunnel 2; the sidewalk 4, road surface 5, cable trench 7, side ditch 8, central drainage ditch 9, etc. are constructed in the single-hole bidirectional tunnel 2;

[0040] The upper part of the sleeve arch 13 is constructed with foamed concrete 40, waterproof layer 41, backfill soil 39, and ecological slope protection 42 in sequence, wherein the foamed concrete 40 can effectively reduce the backfill load at the hole position.

[0041] Embodiment 2

[0042] As another embodiment, this embodiment 2 proposes, based on the embodiment 1, a construction method for the grouting steel pipe reinforced tunnel entrance structure of a temporary concrete platform on complex gully terrain, and its main construction steps are as follows:

[0043] Step 1: Backfilling of gullies and construction of temporary platform for reinforcing arches with sprayed anchor support on slopes: First, select a suitable entry position of a single-hole bidirectional tunnel 2 on the entrance slope line 1, and determine the local cover and excavation construction section of the tunnel; remove the covering layer of the gully 3, perform local backfilling of the gully 20, level the construction platform of the arch 13, and pour the cushion layer 18; perform anchor spraying support 14 for the temporary slope, first install anchor rods 17 and then spray concrete 15, and set a water intercepting ditch 12 on its upper part;

[0044] Step 2: Construction of partial cover of the arch: a small conduit 16 is set in the vertical direction of the arch foot of the arch 13, and grouting is performed by a high-pressure grouting machine to form a grouting body 11, so as to improve the bearing capacity of the arch foot of the arch 13; the arch 13 is made of I-beams, and after the erection is completed, a small piece of standardized steel formwork is used to support the casting of the concrete arch 13, and a reserved deformation is set between the arch and the lower tunnel lining;

[0045] Step 3: Construction of rock-embedded mortar-stopping wall:

[0046] Step 4: Reinforcement construction of the entrance position of a single-hole bidirectional tunnel: Use grouting hole guide drilling technology to drill holes at the entrance position of the single-hole bidirectional tunnel 2 through the grouting hole pipe 32 pre-buried in the grouting wall 31, and use zoned grouting to reinforce the tunnel.

[0047] Step 5: Tunnel entrance foundation reinforcement construction: The foundation is set up at the tunnel entrance and high-pressure grouting is performed to form a grouting body 11 to reinforce the tunnel entrance foundation, wherein the top of the steel pipe pile 10 is welded to the inverted steel cage of the single-hole bidirectional tunnel 2;

[0048] Step 6: Tunnel construction: Construction of sidewalk 4, road surface 5, cable trench 7, side ditch 8, central drainage ditch 9, etc. is carried out in the single-hole bidirectional tunnel 2;

[0049] Step 7: Arch foam concrete backfill and ecological slope protection construction: The upper part of the arch 13 is constructed with foam concrete 40, waterproof layer 41, backfill soil 39, and ecological slope protection 42 in sequence, wherein the foam concrete 40 can effectively reduce the backfill load at the hole position. Figure 7 shown.

[0050] Step 8: Gully Relocation: The existing gully terrain was changed by partial excavation and backfilling of the tunnel. To avoid scouring of the tunnel entrance by gully water during the rainy season, the existing gully was diverted outside the tunnel.

[0051] It should be noted that the parts in this embodiment that are the same or similar to those in the first embodiment can be referenced to each other and will not be described in detail in this application.

[0052] Embodiment 3

[0053] As another embodiment, this embodiment 3 proposes a more specific construction method for reinforcing the tunnel entrance structure by grouting steel pipes on a temporary concrete platform on complex gully terrain based on embodiments 1 and 2:

[0054] like Figures 3 to 6 As shown, in step three, the grout-stopping wall 31 is cast with C30 concrete and has a thickness of 1m, wherein the rock-embedded section 30 is embedded in the surrounding rock by no less than 30cm, and a 3m long seamless steel pipe is pre-buried as a grouting orifice pipe during casting; the initial support 37 is provided with a pre-buried screw barrel 36 at the designed position of the grout-stopping wall 31; the template of the grout-stopping wall 31 adopts a segmented standardized steel template 27 system, and the steel template 27 is welded on the square steel skeleton 26, wherein the square steel skeleton 26 is provided with an ear plate 2 3. The upper and lower segmental shaped steel templates 27 are connected by bolts to fix the ear plates 23; the upper cross bar 33 and the lower cross bar 34 are welded to the square steel frame 26, and are fixed to the embedded screw barrel 36 set in the initial support 37 by screws 35; the steel template 27 is provided with reserved holes according to the position of the grouting orifice pipe 32; after the reinforcement cage of the grout-stopping wall 31 is tied, the shaped steel template 27 is supported in sections, and the lower steel template 27 is supported first, and the lower support rod 25 is at the lower After the steel formwork is supported, one end is bolted to the ear plate 23 of the square steel frame 26, and the other end is fixed to the embedded screw barrel 36 set in the initial support 37 through the screw 35, and concrete is poured; then the middle steel formwork 27 is installed, and concrete is poured; finally, the upper steel formwork 27 is installed, and the upper support rod 25, after the upper steel formwork 27 is supported, one end is bolted to the ear plate 23 of the square steel frame 26, and the other end is fixed to the embedded screw barrel 36 set in the initial support 37 through the screw 35 Fixed, wherein a concrete grouting port 28 and an air guide hole 29 are provided on the upper steel formwork 27, the air guide hole 29 is inserted into the top of the rock-embedded section 30, and the upper concrete construction of the grouting wall 31 is carried out through the concrete grouting port 28, and when the concrete flows out of the air guide hole 29, the concrete construction is stopped; after the segmented steel formwork 27 is supported, the grouting orifice pipe 32 is respectively inserted into the reserved hole position of the steel formwork 27 and sealed, so that the grouting orifice pipe 32 is pre-buried in the grouting wall 31.

[0055] In step four, the grouting hole guide drilling technology is adopted to drill holes at the entrance position of the single-hole bidirectional tunnel 2 through the grouting hole pipe 32 embedded in the grouting wall 31, and the tunnel is reinforced by zoned grouting. The grouting is carried out in reverse order of 4 zones → 3 zones → 2 zones → 1 zone, wherein the area between the excavation contour line 21 and the grouting reinforcement boundary 38 is the reinforcement area; the grouting order is outer circle first and then inner circle, and in the same circle, the upper hole is made first and then the lower hole, with holes skipped at intervals, and the number of holes is gradually increased. The water-free area is injected first, and the water area is injected later, and one hole is injected after drilling.

[0056] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

Claims

1. A concrete temporary platform grouting steel pipe reinforced tunnel entrance structure for complex gully terrain, characterized in that: A single-hole bidirectional tunnel is provided with a casing arch at the entrance slope line of the blind tunnel, with temporary slopes formed on both sides of the casing arch, and anchor spraying support and intercepting ditches are provided on the temporary slopes; the excavation contour line of the single-hole bidirectional tunnel is located below the casing arch, a grouting wall is cast at the entrance of the single-hole bidirectional tunnel, and an initial support is provided inside the casing arch, which fixes the steel formwork connected to the grouting wall; A grouting orifice pipe is pre-buried in the grouting wall, which is used to drill holes and insert grouting pipes from the entrance position of a single-hole bidirectional tunnel. The grouting pipes are obliquely inserted into the soil outside the excavation contour line along the entrance direction for grouting reinforcement.

2. The complex gully terrain concrete temporary platform grouting steel pipe reinforced tunnel entry structure according to claim 1 is characterized in that: The gullies on the entrance slope line are provided with partial backfill, and a cushion layer is cast on the arch construction platform; the anchor spraying support includes anchor rods and concrete, and intercepting ditches are set on the slopes above the anchor spraying support on both sides.

3. The complex gully terrain concrete temporary platform grouting steel pipe reinforced tunnel entrance structure according to claim 1 is characterized in that: A small conduit is drilled in the temporary slope along the tangent direction at the arch foot of the sleeve arch, a grouting body is formed at the bottom of the small conduit, and a reserved deformation amount is set between the sleeve arch and the single-hole bidirectional tunnel lining at the bottom.

4. The complex gully terrain concrete temporary platform grouting steel pipe reinforced tunnel entrance structure according to claim 1 is characterized in that: The slurry-stopping wall includes a rock-embedded section, which is embedded in the surrounding rock outside the excavation contour line, and grouting orifice pipes are pre-buried around the slurry-stopping wall; pre-embedded screw barrels are provided at the top and bottom of the initial support, and the slurry-stopping wall formwork is a steel formwork; a square steel frame is welded and connected to the back of the steel formwork, wherein the square steel frame includes several segments, and ear plates are provided at the ends of the square steel frame segments, and the ear plates of the upper and lower adjacent steel formwork segments are fixedly connected by bolts; an upper cross bar and a lower cross bar are respectively welded to the top and bottom of the square steel frame, and the upper cross bar and the lower cross bar are fixed to the pre-embedded screw barrels provided for the initial support by screws; the steel formwork is provided with reserved holes according to the position of the grouting orifice pipe.

5. The complex gully terrain concrete temporary platform grouting steel pipe reinforced tunnel entrance structure according to claim 1 is characterized in that: Steel pipe piles are driven under the invert of the single-hole bidirectional tunnel entrance, and grouting bodies are arranged on the outer sides of the steel pipe piles as the foundation reinforcement structure of the tunnel entrance, and the tops of the steel pipe piles are welded to the steel cage of the invert of the single-hole bidirectional tunnel; sidewalks, pavements, cable trenches, side ditches and central drainage ditches are constructed in the single-hole bidirectional tunnel.

6. The complex gully terrain concrete temporary platform grouting steel pipe reinforced tunnel entrance structure according to claim 1, characterized in that: The upper part of the sleeve arch is provided with foam concrete, a waterproof layer, backfill soil and ecological slope protection in sequence.

7. The construction method of grouting steel pipe reinforced tunnel entrance structure on a temporary concrete platform on complex gully terrain as claimed in any one of claims 1 to 6, characterized in that: The following steps are involved: Step 1: construct an arch construction platform; construct anchor spraying support for the temporary slope and set up a water intercepting ditch on its upper part; Step 2: construct grouting at the arch foot and pour concrete arch; Step 3: Use steel formwork to construct grout-stopping walls in sections within the arch and pre-embed grouting orifice pipes; Step 4: Drill holes at the entrance of a single-hole bidirectional tunnel through a grouting orifice pipe, and use zoned grouting to reinforce the tunnel; Step 5: Drive steel pipe piles under the invert of the single-hole bidirectional tunnel entrance and inject grout to form a grouting body to reinforce the foundation of the single-hole bidirectional tunnel entrance.

8. The construction method of the grouting steel pipe reinforced tunnel entrance structure of a temporary concrete platform on complex gully terrain according to claim 7 is characterized in that: After the reinforcement cage of the stop wall is tied, the steel formwork is supported in sections from bottom to top and the stop wall is cast in sections. After the uppermost steel formwork is installed in sections, the upper support rod is installed. One end of the upper support rod is fixed to the square steel frame bolt, and the other end is fixed to the bottom of the initial support. A concrete grouting port and an air guide hole are provided on the uppermost steel formwork. The air guide hole is inserted to the top of the stop wall. In step three, concrete construction is carried out on the upper part of the stop wall through the concrete grouting port. When concrete flows out of the air guide hole, the concrete construction is stopped. During the process of supporting the steel formwork in sections, a grouting orifice pipe is simultaneously set and sealed so that the grouting orifice pipe is pre-buried in the stop wall.

9. The construction method of the grouting steel pipe reinforced tunnel entrance structure of a temporary concrete platform on complex gully terrain according to claim 7 is characterized in that: Step four is to drill holes at the entrance of a single-hole bidirectional tunnel through the grouting orifice pipe pre-buried in the stop wall, insert the grouting pipe from the grouting orifice pipe, and use zone grouting to reinforce the tunnel between the excavation contour line and the grouting reinforcement boundary. The zone grouting is performed in reverse order from the position far from the stop wall to the direction close to the stop wall.

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