Construction method for expanding excavation of water-rich soil surrounding rock small-section tunnel and large-section tunnel

Abstract

The invention discloses a construction method for expanding excavation of a large-section tunnel from a water-rich soil surrounding rock small-section tunnel, and belongs to the technical field of tunnel expanding excavation construction.According to the construction method, the small-section tunnel is constructed through an upper step and a lower step, and the large-section tunnel is constructed through the upper step, the middle step and the lower step; the upper step of the small-section tunnel can be obliquely excavated to be connected with the upper step of the large-section tunnel, the upper step of the small-section tunnel is obliquely excavated towards the large tunnel to serve as an advanced pilot tunnel, the working face in the tunnel is increased, the reinforcement condition in the tunnel is formed, construction safety is facilitated, and meanwhile high efficiency of variable-section construction can be guaranteed; and finally, the upper step of the small-section tunnel and the lower step of the large-section tunnel are excavated cooperatively, and the construction steps are clear and reasonable.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel expansion construction, and in particular relates to a construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel. Background Art

[0002] Variable cross-section tunnel construction is inevitable in tunnel construction, especially when the cross-section changes suddenly from a small section to a large section. When excavating with a variable cross-section, each excavation stage has a corresponding short-term tunnel shape, which causes the surrounding rock to load or unload in a variable manner, which not only affects the stability of the surrounding rock during the expansion stage, but also affects the stress distribution and initial support stress condition after the tunnel is formed. In particular, the combination of unfavorable factors such as shallow burial, rich water and weak surrounding rock leads to low construction efficiency and high risk of construction collapse. Summary of the invention

[0003] In view of the deficiencies in the above-mentioned background technology, the present invention aims to provide a construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel, thereby solving the problem that the existing variable-section tunnel construction method will excavate a short-term tunnel shape during the construction process, which will affect the stability of the surrounding rock in the expansion stage and increase the risk of construction collapse.

[0004] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0005] A construction method for expanding a small-section tunnel in a water-rich soil surrounding rock into a large-section tunnel is provided, which comprises:

[0006] Step 1, small-section tunnel construction: excavate the upper step of the small-section tunnel in the small-section tunnel until the upper step of the small-section tunnel is connected with the junction of the small-section tunnel and the large-section tunnel, and provide initial support for the upper step of the small-section tunnel;

[0007] Step 2: Oblique excavation construction: excavate the oblique excavation area to a preset length in the large-section tunnel through the upper steps of the small-section tunnel, and provide initial support for the oblique excavation area;

[0008] Step 3: Excavation of large-section tunnel: Excavate the upper steps of the large-section tunnel to the size of the large-section tunnel through the oblique excavation area, and provide initial support for the upper steps of the large-section tunnel after the expansion;

[0009] Step 4: Back-excavation construction at the upper part of the oblique excavation area: back-excavate the surrounding rock at the top of the oblique excavation area to the junction of the small-section tunnel and the large-section tunnel to form a back-excavation area. The back-excavation direction of the oblique excavation area is from the upper step of the large-section tunnel to the direction of the small-section tunnel, and the back-excavation area is lined and supported;

[0010] Step 5, excavation of the middle and lower steps of the large-section tunnel: excavate the middle steps and lower steps of the large-section tunnel downward in the upper steps of the large-section tunnel, and during the excavation process, perform side wall support on the excavated middle steps and lower steps of the large-section tunnel simultaneously, and perform bottom support on the lower steps of the large-section tunnel after excavation;

[0011] Step 6, excavation construction of the lower steps of the small-section tunnel: excavate the lower steps of the small-section tunnel downwards in the upper steps of the small-section tunnel, and provide bottom support for the lower steps of the small-section tunnel after excavation.

[0012] Furthermore, in step 1, before excavating the upper steps of the small-section tunnel, multiple guide tubes are used to carry out advance support for the arch of the small-section tunnel; after the excavation of the upper steps of the small-section tunnel is completed, multiple grouting anchors are used to support the arch of the upper steps of the small-section tunnel, a steel frame is used to support the middle part of the upper steps of the small-section tunnel, and mortar anchors and shotcrete are used to support the inner wall of the upper steps of the small-section tunnel.

[0013] Furthermore, in step 2, before excavating the oblique excavation area, multiple guide tubes are used to perform advance support on the arch of the small-section tunnel;

[0014] The support and excavation of the oblique excavation area are carried out simultaneously; the excavation angle of the oblique excavation area is 30°, and the excavation width of the oblique excavation area is consistent with the width of the upper step of the small-section tunnel. After the oblique excavation area is excavated to a height difference of 4.9m with the top of the upper step of the small-section tunnel, a reserved horizontal distance of 3.0m is excavated forward horizontally.

[0015] Furthermore, in step 3, when expanding the upper step of the large-section tunnel, the construction is carried out in the order of first excavating the left surrounding rock in the large-section tunnel and then excavating the right surrounding rock in the cross-section tunnel.

[0016] Furthermore, in step 4, when back-digging the surrounding rock at the top of the oblique excavation area, the initial support at the top of the oblique excavation area is removed while the surrounding rock is excavated; the excavation width of the back-digging area is consistent with the width of the large-section tunnel.

[0017] Furthermore, in step 5, the upper steps, middle steps and lower steps of the large-section tunnel are all in the shape of inverted steps; a leveling layer, a waterproof layer, a cement mortar protective layer and a concrete layer are laid in sequence from bottom to top on the lower steps of the large-section tunnel.

[0018] The beneficial effects of the present invention are:

[0019] 1. The construction method of expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel in the present invention, compared with the existing variable-section tunnel construction method, uses the upper step of the small-section tunnel to dig obliquely toward the large tunnel as an advanced pilot tunnel, increases the working surface in the tunnel, forms reinforcement conditions in the tunnel, is beneficial to construction safety, and can also ensure the high efficiency of variable-section construction.

[0020] 2. The present invention discloses a construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel. The back-excavation method is used for the construction of a small-section tunnel into a large-section tunnel with a variable section. Compared with direct expansion construction, the conduit overlap, steel erection, conduit grouting, etc. are more convenient, the support is more efficient, and the construction safety factor is higher.

[0021] 3. The construction method of the present invention for expanding a small-section tunnel into a large-section tunnel in a water-rich soil surrounding rock provides support for the surrounding rock after excavation, which can effectively prevent tunnel construction collapse and improve safety.

[0022] 4. The present invention discloses a construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel. The small-section tunnel is constructed using upper and lower steps, while the large-section tunnel is constructed using upper, middle and lower steps. The upper step of the small-section tunnel is excavated obliquely to connect with the upper step of the large-section tunnel, and the vertical distance of the inclined section is separately excavated into the middle step. Finally, the excavation of the upper step of the small-section tunnel and the lower step of the large-section tunnel are carried out in coordination, making the construction sequence clearer and more reasonable. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The present invention is a flow chart of a construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel.

[0024] Figure 2 This is a schematic diagram of the oblique excavation construction of a small-section tunnel into a large-section tunnel.

[0025] Figure 3 This is a schematic diagram of the upper steps and inclined excavation areas of a small-section tunnel after support.

[0026] Figure 4 Schematic diagram of large-section tunnel expansion construction.

[0027] Figure 5 This is a schematic diagram of the back-excavation construction in the upper part of the inclined excavation area.

[0028] Figure 6 Schematic diagram of lining support for the backcut area.

[0029] Figure 7 Schematic diagram of the excavation construction of the middle and lower steps of a large-section tunnel and the lower steps of a small-section tunnel.

[0030] Figure 8 This is a support diagram for all areas.

[0031] Among them, 1. Small-section tunnel; 2. Upper steps of small-section tunnel; 3. Large-section tunnel; 4. Junction; 5. Oblique excavation area; 6. Upper steps of large-section tunnel; 7. Back-excavation area; 8. Middle steps of large-section tunnel; 9. Lower steps of large-section tunnel; 10. Lower steps of small-section tunnel. DETAILED DESCRIPTION

[0032] The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

[0033] like Figure 1 As shown, this scheme provides a construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel, which includes:

[0034] Step 1: Construction of small-section tunnel 1: Figure 2 As shown, an upper step 2 of a small-section tunnel is excavated in the small-section tunnel 1 until the upper step 2 of the small-section tunnel is connected to the junction 4 of the small-section tunnel 1 and the large-section tunnel 3, and initial support is provided for the upper step 2 of the small-section tunnel.

[0035] like Figure 3 As shown, in step 1, before excavating the upper step 2 of the small-section tunnel, multiple guide tubes are used to carry out advance support for the arch of the small-section tunnel 1. Specifically, the guide tube has a length of 3.5m, a diameter of 42mm, a longitudinal spacing of 0.4m×1.5m, a plum blossom-shaped layout, and an overlap distance of 1m.

[0036] After the excavation of the upper step 2 of the small-section tunnel is completed, multiple grouting anchors are used to support the arch of the upper step 2 of the small-section tunnel. The length of the grouting anchor is 3m, the diameter is 25mm, the ring longitudinal spacing is 1×1m, and the plum blossom shape is arranged. The middle part of the upper step 2 of the small-section tunnel is supported by a steel frame; the inner wall of the upper step 2 of the small-section tunnel is supported by setting mortar anchors and spraying concrete.

[0037] The mortar anchor rod is 3.5m long, 18mm in diameter, with a ring spacing of 1×1m and a plum blossom shape arrangement; the concrete used is C25 shotcrete with a thickness of 200mm.

[0038] Step 2: Oblique excavation construction: Figure 2As shown, the oblique excavation area 5 is excavated to a preset length in the large-section tunnel 3 through the upper step 2 of the small-section tunnel, and the oblique excavation area 5 is initially supported.

[0039] Specifically, in step 2, before excavating the oblique excavation area 5, multiple conduits are used to carry out advance support for the arch of the small-section tunnel 1; on the basis of the horizontal direction of the arch of the small-section tunnel 1, a Φ42mm conduit is laid at 30° upward, the length of the conduit is 3.5m, the longitudinal spacing of the ring of multiple conduits is 0.4m×1.5m, and the multiple conduits are arranged in a plum blossom shape with an overlap distance of 1m. The overlap width range is consistent with that of the small-section tunnel 1. When reaching the top of the large-section tunnel 3, the overlap form is overlapped according to the shape of the arch of the large-section tunnel 3, and the overlap width is consistent with the width of the slope, and then it is laid horizontally forward for 3.0m.

[0040] The support and excavation of the oblique excavation area 5 are carried out simultaneously; the excavation angle of the oblique excavation area 5 is 30°, and the excavation width of the oblique excavation area 5 is consistent with the width of the upper step 2 of the small-section tunnel. After the oblique excavation area 5 is excavated to a height difference of 4.9m with the top of the upper step 2 of the small-section tunnel, a reserved horizontal distance of 3.0m is excavated forward horizontally.

[0041] like Figure 3 As shown, the initial support of the oblique excavation area 5 is specifically as follows: a plurality of hollow grouting anchor rods with a diameter of 25 mm, a length of 3.5 m, a ring longitudinal spacing of 1×1 m and arranged in a plum blossom shape are arranged on the arch of the oblique excavation area 5, and a 240 mm thick concrete is sprayed on the inner wall of the arch of the oblique excavation area 5. A plurality of mortar anchor rods with a diameter of 18 mm, a length of 3.5 m, a ring longitudinal spacing of 1×1 m and arranged in a plum blossom shape are arranged on the side wall of the oblique excavation area 5; a 200 mm thick concrete is sprayed on the side wall of the oblique excavation area 5.

[0042] Step 3: Expansion and construction of large-section tunnel 3: Figure 4 As shown, the upper step 6 of the large-section tunnel is expanded to the size of the large-section tunnel 3 through the oblique excavation area 5 in the large-section tunnel 3, and initial support is performed on the upper step 6 of the large-section tunnel after expansion; in step 3, when expanding the upper step 6 of the large-section tunnel, the left surrounding rock in the large-section tunnel 3 is excavated first, and then the right surrounding rock in the large-section tunnel is excavated.

[0043] Step 4: Back-excavation of the upper part of the oblique excavation area 5: Figure 5 and Figure 6As shown, the surrounding rock at the top of the oblique excavation area 5 is back-excavated to the junction 4 of the small-section tunnel 1 and the large-section tunnel 3 to form a back-excavation area 7, and the back-excavation direction of the oblique excavation area 5 is from the upper step of the large-section tunnel 3 to the small-section tunnel 1, and the back-excavation area 7 is lined and supported; in step 4, when the surrounding rock at the top of the oblique excavation area 5 is back-excavated, the initial support at the top of the oblique excavation area 5 is removed while the surrounding rock is excavated; the excavation width of the back-excavation area 7 is consistent with the width of the large-section tunnel 3.

[0044] Step 5: Excavation of the lower steps of the large-section tunnel 3: Figure 7 and Figure 8 As shown, a middle step 8 and a lower step 9 of a large-section tunnel are excavated downwards in an upper step 6 of a large-section tunnel. During the excavation process, the middle step 8 and the lower step of the large-section tunnel are simultaneously supported by side walls, and the lower step 9 of the large-section tunnel is supported by bottom support after the excavation is completed.

[0045] In step 5, the upper step 6, the middle step and the lower step of the large-section tunnel are all in the shape of inverted steps; the leveling layer, the waterproof layer, the cement mortar protective layer and the concrete layer are laid from bottom to top on the lower step 9 of the large-section tunnel. The leveling layer is a 100mm thick fine stone concrete layer, the waterproof layer is a 1.5mm thick HDPE self-adhesive waterproof membrane, the cement mortar protective layer is 20mm thick, and the concrete layer is 500mm thick, with a grade of C40.

[0046] Step 6, excavation construction of the lower step 10 of the small-section tunnel: excavate the lower step 10 of the small-section tunnel downward in the upper step 2 of the small-section tunnel, and provide bottom support for the lower step 10 of the small-section tunnel after excavation.

[0047] In summary, the construction method of the water-rich soil surrounding rock small-section tunnel 1 in the present invention is compared with the existing variable-section tunnel construction method. The upper step 2 of the small-section tunnel is used to dig obliquely toward the large tunnel as a leading tunnel, thereby increasing the working surface in the tunnel and forming reinforcement conditions in the tunnel, which is beneficial to construction safety and can also ensure the high efficiency of variable-section construction. The back-digging method is used for the variable-section construction of the small-section tunnel 1 into the large-section tunnel 3. Compared with the direct expansion construction, the conduit overlap, steel erection, conduit grouting, etc. are more convenient, and the support is more secure. High efficiency, and at the same time a higher construction safety factor; after the surrounding rock is excavated, support is carried out to effectively prevent tunnel construction collapse and improve safety; the small-section tunnel 1 is constructed with upper and lower steps, while the large-section tunnel 3 is constructed with upper, middle and lower steps, so that the oblique excavation of the upper step 2 of the small-section tunnel can connect with the upper step 6 of the large-section tunnel, and the vertical distance of the inclined section is separately excavated into a middle step, and finally the excavation of the upper step 2 of the small-section tunnel and the lower step 9 of the large-section tunnel are carried out in coordination, making the construction sequence clearer and more reasonable.

Claims

1. A construction method for expanding a small-section tunnel in water-rich soil surrounding rock into a large-section tunnel, characterized in that: include: Step 1, small-section tunnel construction: excavate the upper step of the small-section tunnel in the small-section tunnel until the upper step of the small-section tunnel is connected with the junction of the small-section tunnel and the large-section tunnel, and provide initial support for the upper step of the small-section tunnel; Step 2: Oblique excavation construction: excavate the oblique excavation area to a preset length in the large-section tunnel through the upper steps of the small-section tunnel, and provide initial support for the oblique excavation area; Step 3: Excavation of large-section tunnel: Excavate the upper steps of the large-section tunnel to the size of the large-section tunnel through the oblique excavation area, and provide initial support for the upper steps of the large-section tunnel after the expansion; Step 4: Back-excavation construction at the upper part of the oblique excavation area: back-excavate the surrounding rock at the top of the oblique excavation area to the junction of the small-section tunnel and the large-section tunnel to form a back-excavation area. The back-excavation direction of the oblique excavation area is from the upper step of the large-section tunnel to the direction of the small-section tunnel, and the back-excavation area is lined and supported; Step 5, excavation of the middle and lower steps of the large-section tunnel: excavate the middle steps and lower steps of the large-section tunnel downward in the upper steps of the large-section tunnel, and during the excavation process, perform side wall support on the excavated middle steps and lower steps of the large-section tunnel simultaneously, and perform bottom support on the lower steps of the large-section tunnel after excavation; Step 6, excavation construction of the lower steps of the small-section tunnel: excavate the lower steps of the small-section tunnel downwards in the upper steps of the small-section tunnel, and provide bottom support for the lower steps of the small-section tunnel after excavation.

2. The construction method for expanding a small-section tunnel into a large-section tunnel in water-rich soil surrounding rock according to claim 1 is characterized in that: In step 1, before excavating the upper step of the small-section tunnel, multiple guide tubes are used to support the arch of the small-section tunnel in advance; after the excavation of the upper step of the small-section tunnel is completed, multiple grouting anchors are used to support the arch of the upper step of the small-section tunnel, a steel frame is used to support the middle of the upper step of the small-section tunnel, and mortar anchors and shotcrete are used to support the inner wall of the upper step of the small-section tunnel.

3. The construction method for expanding a small-section tunnel into a large-section tunnel in water-rich soil surrounding rock according to claim 1 is characterized in that: In step 2, before excavating the oblique excavation area, multiple guide tubes are used to provide advance support for the arch of the small-section tunnel; The support and excavation of the oblique excavation area are carried out simultaneously; the excavation angle of the oblique excavation area is 30°, and the excavation width of the oblique excavation area is consistent with the width of the upper step of the small-section tunnel. After the oblique excavation area is excavated to a height difference of 4.9m with the top of the upper step of the small-section tunnel, a reserved horizontal distance of 3.0m is excavated forward horizontally.

4. The construction method of expanding a small-section tunnel into a large-section tunnel in water-rich soil surrounding rock according to claim 1 is characterized in that: In step 3, when expanding the upper step of the large-section tunnel, the construction is carried out in the order of first excavating the left surrounding rock in the large-section tunnel and then excavating the right surrounding rock in the cross-section tunnel.

5. The construction method of expanding a small-section tunnel into a large-section tunnel in water-rich soil surrounding rock according to claim 1, characterized in that: In step 4, when back-digging the surrounding rock at the top of the oblique excavation area, the initial support at the top of the oblique excavation area is removed while the surrounding rock is excavated; the excavation width of the back-digging area is consistent with the width of the large-section tunnel.

6. The construction method of expanding a small-section tunnel into a large-section tunnel in water-rich soil surrounding rock according to claim 1, characterized in that: In step 5, the upper steps, middle steps and lower steps of the large-section tunnel are all in the shape of inverted steps; a leveling layer, a waterproof layer, a cement mortar protective layer and a concrete layer are laid in sequence from bottom to top on the lower steps of the large-section tunnel.

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