Tunnel holing method based on wall-embedded cover arch in foundation pit

Abstract

The invention relates to the field of underground engineering portal construction, and discloses a tunnel holing method based on a wall-embedded cover arch in a foundation pit, which comprises the following steps: step 1, constructing a row of fender posts at a portal position, each fender post comprises a half-pile section, a reserved notch is formed in one side, close to the interior of the foundation pit, of each half-pile section, and the reserved notches are formed above the portal; a filler is arranged in the reserved notch; secondly, the foundation pit is excavated to the position of the reserved notch, and the filler in the reserved notch is taken out; thirdly, a cover arch is constructed, the cover arch is embedded into the reserved notches of the multiple fender posts, and the multiple fender posts are connected into a whole; fourthly, a pipe shed is constructed on the cover arch; and fifthly, a hole is excavated. The method is suitable for narrow space and complex geological conditions.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of underground engineering portal construction, in particular to a tunnel opening method based on embedded wall nested arch in foundation pit. BACKGROUND

[0002] In the construction of a tunnel by excavation, when it is necessary to enter the tunnel from an open excavation foundation pit, an advanced pipe shed is usually set up to ensure construction safety. In the prior art, the traditional construction scheme of the advanced pipe shed is to construct a nested arch structure in the inner side of the foundation pit after the foundation pit is excavated to the design elevation and the bottom is completed, and then the nested arch is used as a guide frame to perform the pipe shed setting operation.

[0003] However, the traditional construction scheme has the following technical defects: first, since the nested arch needs to be used as the fulcrum of the pipe shed, the nested arch must have a certain length (usually 2-3 m) and thickness (usually ≥0.6 m) to ensure the stability of the nested arch; the nested arch structure occupies the effective space inside the open excavation foundation pit, and when the width of the foundation pit is limited by the surrounding environment and is relatively small, it may not meet the operation space requirements of the pipe shed construction, resulting in increased construction difficulty or even inability to implement the construction, and if the bottom of the nested arch is filled with soil or other poor geology, the foundation of the nested arch bottom needs to be treated; second, the nested arch as a temporary structure occupies the space of the main structure constructed in the later stage of the open excavation section, and the nested arch needs to be removed during the construction of the main structure, which not only increases the construction process and engineering cost, but also may disturb the completed structure; in addition, the traditional scheme requires the foundation pit to be excavated to the design bottom, and the foundation pit enclosure structure in the opening range needs to be designed in strength and stiffness according to the design depth of the entire foundation pit, resulting in a large amount of enclosure structure engineering, conservative design and uneconomical design.

[0004] The above problems limit the applicability of the traditional portal construction method in narrow spaces and complex geological conditions, and therefore, there is an urgent need for a portal construction method that can solve the above technical defects. SUMMARY

[0005] The present application aims to provide a tunnel opening method based on embedded wall nested arch in foundation pit, which is suitable for narrow spaces and complex geological conditions.

[0006] To achieve the above purpose, the present application adopts the following technical scheme: a tunnel opening method based on embedded wall nested arch in foundation pit, comprising the following steps: Step one, a row of enclosure piles are constructed at the portal position, the enclosure piles each include a half pile section, the half pile section is provided with a reserved gap near the inner side of the foundation pit, the reserved gap is arranged above the portal, and a filler is arranged in the reserved gap; Step two, the foundation pit is excavated to the reserved gap position, and the filler in the reserved gap is removed; Step three, a nested arch is constructed, the nested arch is embedded in the reserved gaps of the enclosure piles, and the enclosure piles are connected into a whole; Step four, make a pipe shed on the arch; Step five, excavate the hole.

[0007] The beneficial effects of the present scheme are: 1. In the prior art, since the arch is supported on the ground, when the foundation pit is continuously excavated later, the arch on the ground needs to be broken first, which increases the engineering quantity and construction period.

[0008] The present structure is suitable for the position of the underground engineering open-cut hole. When the hole needs to be provided with an advanced pipe shed, the arch is directly poured between the retaining piles, and the embedded wall arch can make the arch and the pipe shed be made at the stage when the excavation of the foundation pit is not completed. With the excavation of the foundation pit, the retaining piles in the hole can be broken in steps. In the case that the foundation pit is not bottomed, the rock-soil body behind the retaining piles is excavated in advance, the hole range of the foundation pit can not be designed according to the depth of the whole foundation pit, the length of the retaining piles can be reduced to save the engineering investment; the arch does not occupy the space in the foundation pit, which is more conducive to the pipe shed operation in a narrow foundation pit, and also avoids the breaking of the arch later.

[0009] 2. The present scheme is not simply embedded in the retaining pile, but combines the construction process to make the structure more convenient to implement. Specifically, the retaining pile is constructed on the ground, and the reserved gap is provided in advance when the retaining pile is poured to facilitate the construction of the arch later; the foundation pit is excavated with the retaining pile as a side support, and the excavation is performed to the height of the arch; the retaining piles are connected into a whole through the arch, which increases the stability of the whole structure and plays a good guiding role for the subsequent construction of the pipe shed, thereby ensuring the advanced support effect of the pipe shed.

[0010] 3. The pipe shed is driven into the soil, which not only can provide advanced support during excavation, but also helps the retaining pile resist the soil pressure behind the pile, thereby optimizing the stress structure.

[0011] Further, in step one, the retaining pile has a circular cross section, and the reserved gap of the half-pile section has a semicircular cross section.

[0012] Further, in step three, the arch fills the reserved gaps of a plurality of retaining piles.

[0013] Further, the retaining piles on both sides of the arch are edge piles, and the remaining retaining piles are middle piles; in step five, the part of the middle piles located in the tunnel range is broken, and the lower side of the arch is trimmed into an arc-shaped gap matching the cross-sectional shape of the tunnel.

[0014] Further, in step one, the reserved gaps of the middle piles are all semicircular columns with the same shape, size and height; in step three, after the arch is poured, the lower side of the arch is a trapezoidal gap.

[0015] Further, in step one, the filler is concrete or foam.

[0016] Further, in step one, a steel box is arranged in the fender pile, the fender pile comprises a steel reinforcement cage, the steel box and the steel reinforcement cage are fixedly connected, and a reserved gap is formed in the internal space of the steel box.

[0017] Further, the fender pile comprises an outer steel reinforcement cage and an inner steel reinforcement cage, the outer steel reinforcement cage has a circular cross section, the inner steel reinforcement cage has a semicircular cross section, the inner steel reinforcement cage is inserted into the outer steel reinforcement cage to the half-pile section and is fixed with the outer steel reinforcement cage.

[0018] Further, the inner steel reinforcement cage is fixed with a side iron sheet near the inner side of the foundation pit; the outer steel reinforcement cage is provided with an annular reinforcing rib at a position corresponding to the bottom of the half-pile section, the inner steel reinforcement cage is supported on the annular reinforcing rib, and the annular reinforcing rib is provided with a bottom iron sheet as the bottom of the reserved gap.

[0019] The present scheme has the following effects: 1. The embedded sleeve arch and the fender pile form a whole, the fender pile can serve as the foundation pile of the sleeve arch, and the foundation treatment of the traditional sleeve arch on the sleeve arch base is avoided.

[0020] 2. The land occupied by the sleeve arch can be saved, thereby reducing the land occupied by the whole open excavation foundation pit project.

[0021] 3. The sleeve arch not only needs to be embedded in the fender pile, but also needs to fill the reserved gap of the fender pile to ensure the integrity of the fender pile, thereby ensuring the supporting effect of the fender pile. 4. The column is a necessary core stress structure which simultaneously bears the load of the fender pile and the pipe shed.

[0022] 5. The filler is concrete; when the concrete is used for filling, a steel sheet is used to isolate the filler and the fender pile body, so that the fender pile body will not be damaged when the filler is broken in the later period.

[0023] 6. When the filler is foam, a steel box is arranged around the foam, and the foam is used for filling, so as to strengthen the stability of the filling range and avoid problems such as floating of the foam in the concrete pouring process and hydration heat erosion.

[0024] 7. By arranging the nested outer steel reinforcement cage and the inner steel reinforcement cage, the outer steel reinforcement cage is first placed in the pile hole, and then the inner steel reinforcement cage is placed, so as to adjust the position of the steel reinforcement cage, thereby adjusting the height of the reserved gap, and then ensuring that the upper sides of all the reserved gaps are flush, so that the part of the fender pile above the half-pile section can uniformly transmit the load to the sleeve arch, thereby avoiding stress concentration and reducing durability.

[0025] 8. The inner steel reinforcement cage is separately arranged at the half-pile section to strengthen it, so that the half-pile section can effectively transmit the load before pouring the sleeve arch. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 is a flowchart of Example 1; Figure 2 is a schematic diagram of the initial state of embodiment 1; Figure 3 is a schematic diagram of the installation of the arch after the installation of the arch reinforcement of embodiment 1; Figure 4 is a schematic diagram of the pouring of the arch after the pouring of the arch of embodiment 1; Figure 5 is a schematic diagram of the construction of the pipe shed after the construction of the pipe shed of embodiment 1; Figure 6 is a schematic diagram of the tunnel excavation after the tunnel excavation of embodiment 1; Figure 7 is a schematic diagram of the tunnel excavation after the tunnel excavation of embodiment 1; Figure 2 is a sectional view along A-A of Figure 8 is a sectional view along A-A of Figure 3 is a sectional view along A-A of Figure 9 Figure 4 is a sectional view along A-A of Figure 10 is a sectional view along A-A of Figure 5 is a sectional view along A-A of Figure 11 Figure 6 is a sectional view along A-A of DETAILED DESCRIPTION

[0027] The following is further described in detail through specific embodiments: The reference signs in the drawings of the specification include: foundation pit 1, hole opening 2, arch 3, arch reinforcement 31, column 32, arch portion 33, pipe shed 4, enclosure pile 5, side pile 51, middle pile 52, filler 53, half pile segment L.

[0028] Embodiment 1 The method for opening a hole in a tunnel based on a wall-embedded arch in a foundation pit, a flowchart as shown in Figure 1 includes the following steps: Step one, a row of enclosure piles 5 is constructed at the hole opening 2 position, as shown in Figure 2 The enclosure piles 5 each include a half pile segment L, the half pile segment L has a reserved gap near one side in the foundation pit 1, the reserved gap of the half pile segment L is a semicircular cross section, the reserved gap is used to accommodate the arch 3, the arch 3 and the enclosure pile 5 are both reinforced concrete structures, the enclosure pile 5 includes a steel cage, the steel cage of the half pile segment L is a semicircular cross section; a steel box is provided in the enclosure pile 5, the enclosure pile 5 includes a steel cage, the steel box and the steel cage are welded, and the internal space of the steel box forms the reserved gap.

[0029] The reserved gap is provided above the hole opening 2, and the reserved gap is provided with a filler 53; as shown in Figure 2 , Figure 7 The filler 53 is concrete or foam, in this embodiment, the filler 53 is foam; Step two, as​​Figure 3 , Figure 8 As shown, excavate the foundation pit 1, excavate the soil in front of the pile to the reserved gap position, remove the filling material 53, and tie the arch reinforcement 31 in the reserved gap; Step 3, as follows Figure 4 , Figure 9 As shown, the construction arch 3 is embedded in the reserved gaps of several retaining piles 5. The arch 3 passes through the reserved gaps of several retaining piles 5 in sequence, connecting several retaining piles 5 into a whole. like Figure 7 As shown, the retaining piles 5 on both sides of the arch 3 are side piles 51, and the remaining retaining piles 5 are central piles 52. The reserved gaps of the central piles 52 are all semi-circular columns with the same shape, size and height. The depth of the central piles 52 does not need to be designed according to the depth of the foundation pit 1. The main function of the central piles 52 is to provide temporary support for the foundation pit 1 before the excavation of the opening 2. The arch 3 includes an arch 33, and columns 32 are provided on both sides of the arch 33. The two columns 32 are used to fill the reserved gaps of the side piles 51. The arch 33 passes through the reserved gaps of the central piles 52, and the upper surface of the arch 33 fits against the upper side of the reserved gaps of the central piles 52.

[0030] Among them, the arch 33 fills the reserved gap of the central pile 52, thereby forming a trapezoidal gap on the lower side of the arch 33, and the column 32 fills the reserved gap of the side pile 51. Step 4: Construction on arch 3 as follows Figure 5 , Figure 10 The pipe roof 4 shown is an existing advanced support structure constructed from the two sets of arches 3 at the entrance to the depth of the tunnel, which will not be described in detail here. Step 5, Excavate opening 2: (e.g.) Figure 6 , Figure 11 As shown, after the pipe roof 4 is constructed, the portion of the central pile 52 located within the tunnel area is broken, and the lower side of the arch 33 is modified into an arc-shaped notch that matches the shape of the tunnel cross section.

[0031] Example 2 The difference between Example 2 and Example 1 is that the retaining pile 5 includes an outer steel cage and an inner steel cage. The outer steel cage has a circular cross-section, and the inner steel cage has a semi-circular cross-section. Circular reinforcing bars are welded on-site at the top and bottom positions of the corresponding half-pile segment L inside the outer steel cage. The structure of the circular reinforcing bars is existing technology, and this example only limits their position. A bottom iron plate is provided on the circular reinforcing bar as the bottom of the reserved notch. The inner steel cage is inserted into the outer steel cage to the half-pile segment L. The inner steel cage is supported on the circular reinforcing bar. The inner and outer steel cages are welded and fixed. A side iron plate is welded and fixed on the side of the inner steel cage closest to the pit 1. The side iron plate serves as the side of the reserved notch. The filling material 53 in the reserved notch is concrete.

[0032] The sleeve arch 3 is generally arranged in the upper part of the foundation pit 1, and the soil pressure behind the retaining structure pile is increased by a small amount. Although the scheme has a loss in the cross-sectional size of the retaining pile 5, the reinforcement of the variable cross-section retaining pile 5 can be considered to be strengthened, and therefore, the inner steel reinforcement cage is additionally arranged in the embodiment.

[0033] The inner hole size of the inner steel reinforcement cage needs to meet the installation of the concrete pumping pipe and the use of the vibrating rod, otherwise, the embodiment is not suitable.

[0034] The above-mentioned is only an embodiment of the present application, and the specific technical solutions and / or common knowledge of the scheme are not described in detail. It should be pointed out that for those skilled in the art, without departing from the technical scheme of the present application, a number of modifications and improvements can be made, which should also be considered as the protection scope of the present application, which will not affect the effect and practicality of the patent. The protection scope claimed in the present application should be subject to the content of its claims, and the specific implementation mode and the like recorded in the specification can be used to explain the content of the claims.

Claims

1. A method for tunnel opening within an excavation pit based on embedded wall and arch, characterized in that, Includes the following steps: Step 1: Construct a row of retaining piles at the opening location. Each retaining pile includes a half-pile segment. A reserved gap is provided on the side of the half-pile segment closest to the pit. The reserved gap is located above the opening and is filled with filling material. Step 2: Excavate the foundation pit to the reserved gap location and remove the filling material inside the reserved gap; Step 3: Construct the arch, embedding the arch into the reserved gaps of several retaining piles to connect the retaining piles into a whole; Step 4: Construct pipe sheds on the arch; Step 5: Excavate the opening.

2. The method for tunnel opening based on embedded wall arch within a foundation pit according to claim 1, characterized in that: In step one, the retaining piles have a circular cross-section, and the reserved notch in the half-pile section has a semi-circular cross-section.

3. The method for tunnel opening based on embedded wall arch in foundation pit according to claim 1, characterized in that: In step three, the arch is used to fill the reserved gaps in several retaining piles.

4. The method for tunnel opening based on embedded wall arch within a foundation pit according to claim 3, characterized in that: The retaining piles on both sides of the arch are side piles, and the remaining retaining piles are center piles; in step five, the part of the center pile located within the tunnel is broken, and the lower side of the arch is modified into an arc-shaped notch that matches the shape of the tunnel cross section.

5. The method for tunnel opening based on embedded wall arch within a foundation pit according to claim 4, characterized in that: In step one, the reserved gaps in the central piles are all semi-circular columns with the same shape, size and height; in step three, after the arch is poured, the lower side of the arch is a trapezoidal gap.

6. The method for tunnel opening based on embedded wall arch in foundation pit according to claim 1, characterized in that: In step one, the filler is concrete or foam.

7. The method for tunnel opening based on embedded wall arch within a foundation pit according to claim 1, characterized in that: In step one, a steel box is installed inside the retaining pile. The retaining pile includes a steel cage. The steel box and the steel cage are fixedly connected, and a reserved gap is formed in the internal space of the steel box.

8. The method for tunnel opening based on embedded wall arch in foundation pit according to claim 1, characterized in that: The retaining pile consists of an outer steel cage and an inner steel cage. The outer steel cage has a circular cross-section, and the inner steel cage has a semi-circular cross-section. The inner steel cage is inserted into the outer steel cage to half of the pile section and fixed to the outer steel cage.

9. The method for tunnel opening within a foundation pit based on embedded wall arches according to claim 1, characterized in that: The inner steel cage has a side iron plate fixed on the side closest to the foundation pit; the outer steel cage has a ring-shaped reinforcing bar at the bottom of the corresponding half pile section, the inner steel cage is supported on the ring-shaped reinforcing bar, and the ring-shaped reinforcing bar has a bottom iron plate as the bottom of the reserved notch.

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