Reinforcing method for shield tunnel to pass through bead-stringed karst cave

Abstract

The invention relates to a reinforcing method for a shield tunnel to pass through bead-stringed karst cave, which comprises the following steps of: sequentially reinforcing each layer of karst cave from bottom to top to form a reinforcing area until the current layer of reinforcing area is constructed, and judging that all the constructed reinforcing areas can be kept stable; the determination method of the reinforcing area comprises the steps that if the shield tunneling machine penetrates through the position below the maximum diameter position of the crossing layer karst cave, the lowest reinforcing area is the area between the top face of the crossing area of the shield tunneling machine and the maximum diameter position of the crossing layer karst cave; if the shield tunneling machine penetrates through the position above the maximum diameter position of the karst cave of the crossing layer, the lowest reinforcing area is the area between the maximum diameter position and the bottom face of the karst cave of the upper layer of the crossing layer, and the area between the lowest reinforcing area and the top face of the crossing area is also reinforced; and the other layers of reinforcing areas are all areas between the maximum-diameter positions of the corresponding layers of karst caves and the bottom surfaces of the karst caves. By the adoption of the method, the construction cost is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering, and in particular to a reinforcement method for a shield tunnel passing through a beaded cave. Background Art

[0002] The statements herein merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Under karst geological conditions, shield construction faces severe challenges, especially complex underground structures such as caves and fissures, which are prone to cause geological disasters such as ground collapse and tunnel collapse during construction, seriously threatening construction safety and project progress. This not only affects the safety of construction, but is also directly related to the overall quality and economic benefits of the project. Due to the widespread distribution of limestone strata and the degree of karst development, caves are often encountered frequently during construction. This requires special measures to ensure the smooth progress of tunnel construction. In particular, beaded caves, a series of connected caves formed by karst action, contain multiple large caverns that are interconnected by narrow tunnels. Since the karst phenomena in karst strata vary in scale, form, size and location, the overall reinforcement economic cost is large and the construction cost is high. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a reinforcement method for a shield tunnel passing through a beaded cave, which improves the safety of construction and reduces the cost of reinforcement construction.

[0005] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0006] The embodiment of the present invention provides a reinforcement method for a shield tunnel passing through a beaded karst cave, wherein each layer of the karst cave is reinforced in sequence from bottom to top to form a reinforcement zone, until the construction of the reinforcement zone of the current layer is completed, and all the completed reinforcement zones are determined to be able to remain stable;

[0007] Among them, the method for determining the reinforcement area is: if the shield machine passes below the maximum diameter position of the karst cave in the crossing layer, then the lowest reinforcement area is the area between the top surface of the shield machine crossing area and the maximum diameter position of the karst cave in the crossing layer; if the shield machine passes above the maximum diameter position of the karst cave in the crossing layer, then the lowest reinforcement area is the area between the maximum diameter position and the bottom surface of the upper layer of the karst cave in the crossing layer, and the area between the lowest reinforcement area and the top surface of the crossing area is also reinforced; the remaining reinforcement areas are all the areas between the maximum diameter position of the corresponding layer of karst cave and the bottom surface of the karst cave.

[0008] Optionally, after the current layer reinforcement area is reinforced, the stability of the reinforcement area of ​​the layer below the current layer reinforcement area is judged. If it is still unstable, the reinforcement area of ​​the layer below the current layer reinforcement area is reinforced for the second time.

[0009] Optionally, a bag-type expansion anchor cable may be used for secondary reinforcement.

[0010] Optionally, the stability judgment method for the reinforcement area of ​​the current layer is:

[0011] The maximum bending moment and the maximum shear force of the current layer reinforcement zone are obtained according to the load applied to the current layer reinforcement zone by the karst cave filling material where the current layer reinforcement zone is located and the load applied to the current layer reinforcement zone by all karst cave filling materials above the karst cave where the current layer reinforcement zone is located;

[0012] The stability of the reinforcement area of ​​the current layer is determined based on the maximum bending moment and maximum shear force obtained.

[0013] Optionally, the strength of the current layer reinforcement area is checked based on the obtained maximum bending moment and maximum stress combined with the fourth strength theory and von Mises stress as failure judgment indicators, and whether the current layer reinforcement area is stable is determined based on the strength check results.

[0014] Optionally, when judging the stability of the current layer reinforcement area, the current layer reinforcement area is simplified to a simply supported beam model for calculation.

[0015] Optionally, the length of the simply supported beam model is the diameter of the bottom surface of the reinforcement zone of the current layer, and the thickness of the simply supported beam model is the actual thickness of the reinforcement zone of the current layer.

[0016] Optionally, after obtaining the maximum diameter position and the minimum diameter position of each layer of caves, each layer of caves is simplified into a cave with a quadrilateral vertical cross-section, and then the position of the reinforcement area is determined.

[0017] Optionally, the reinforcement method for each reinforced area is grouting reinforcement.

[0018] Optionally, when the shield machine passes above the maximum diameter position of the karst cave in the crossing layer, the area between the lowest reinforcement area and the top surface of the crossing area is reinforced by grouting, and bag-type hole expansion anchor cables are also used for auxiliary reinforcement.

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. The reinforcement method of the present invention sequentially reinforces each layer of caves from bottom to top to form a reinforcement area, until the top reinforcement area is reinforced. Each layer of reinforcement area can remain stable, and the reinforcement area does not cover the entire cave space. Therefore, when reinforcing the beaded caves, only the reinforcement area of ​​the set multi-layer caves is reinforced, rather than grouting reinforcement of all the caves, which greatly reduces the processing and construction costs and shortens the processing and construction time.

[0021] 2. The reinforcement method of the present invention, after the current reinforcement area is reinforced, the stability of the reinforcement area of ​​the layer below the current reinforcement area is judged. If it is still unstable, the reinforcement area of ​​the layer below the current reinforcement area is reinforced for the second time, thereby ensuring the stability of all completed reinforcement layers, and further ensuring the safety of tunnel shield crossing construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0023] Figure 1 is a flow chart of the reinforcement method of embodiment 1 of the present invention;

[0024] Figure 2 Schematic diagram of the bottom reinforcement area when the shield machine passes below the maximum diameter position of the karst cave in the traversing layer according to Embodiment 1 of the present invention;

[0025] Figure 3 Schematic diagram of the bottom reinforcement area when the shield machine passes through the top of the maximum diameter position of the karst cave in the traversing layer according to Embodiment 1 of the present invention;

[0026] Figure 4 This is the force diagram of the bottom reinforcement area of ​​Example 1 of the present invention;

[0027] Figure 5 This is a schematic diagram of the second layer reinforcement area of ​​Example 1 of the present invention;

[0028] Figure 6 This is a schematic diagram of secondary reinforcement of the first layer reinforcement area in Example 1 of the present invention;

[0029] Among them, 1. limestone, 2. filling material, 3. shield tunnel, 4. reinforcement area, 5. anchor cable, 6. bladder bag. DETAILED DESCRIPTION

[0030] Example 1

[0031] This embodiment provides a reinforcement method for a shield tunnel passing through a beaded cave. Figure 1As shown, the method includes the following steps: first, determining the maximum diameter position of each layer of the beaded caves; then, reinforcing each layer of the caves in order from bottom to top to form a reinforced area; after the construction of the reinforced area of ​​the current layer is completed, all the completed reinforced areas are judged to be able to remain stable.

[0032] Among them, if the shield machine passes below the maximum diameter position of the karst cave in the traversing layer, the lowest reinforced area is the area between the top surface of the shield machine traversing area and the maximum diameter position of the karst cave in the traversing layer; if the shield machine passes above the maximum diameter position of the karst cave in the traversing layer, the lowest reinforced area is the area between the maximum diameter position and the bottom surface of the upper karst cave in the traversing layer, and the area between the lowest reinforced area and the top surface of the traversing area is also reinforced; the remaining reinforced areas are all the areas between the maximum diameter position of the corresponding karst cave and the bottom surface of the karst cave.

[0033] The specific steps include:

[0034] Step 1: Conduct geological surveys of the site, collect geological parameters, investigate karst landform features in detail, and identify adverse geological bodies such as caves and underground rivers. In this embodiment, the geology is limestone 1, the cave is a beaded cave, and there is a filler 2 in the cave. Through drilling, seismic wave reflection and other methods, the distribution, size and filler 2 characteristics of the beaded cave are determined, and the stability of the stratum and groundwater activity are evaluated. The survey results are used to optimize the shield construction plan, prevent risks such as water inrush and landslides, and improve the safety and construction efficiency of the project;

[0035] The above steps can be carried out using existing technologies and will not be described in detail here.

[0036] Step 2: Characterize the morphology of the cave according to the survey results, accurately identify the morphology of the cave, and obtain the maximum diameter position and bottom position of each layer of the cave. In this embodiment, based on the identification results, each layer of the cave is simplified into a cave with a quadrilateral vertical cross-section.

[0037] Step 3: Determine the reinforcement position of the cave and perform grouting reinforcement on the cave, which specifically includes the following steps:

[0038] Step 3.1 first determines the position of the lowest reinforcement area. In this embodiment, a layer of caves that the shield machine passes through is defined as the passing layer caves.

[0039] like Figure 2 As shown, if the shield machine passes below the maximum diameter position of the karst cave in the traversing layer, the lowest reinforcement area 4 is from the top surface of the shield machine traversing area to the maximum diameter position of the karst cave in the traversing layer, and grouting reinforcement is performed on the determined lowest reinforcement area.

[0040] like Figure 3As shown, if the shield machine passes above the maximum diameter position of the karst cave in the crossing layer, the lowest reinforcement area 4 is the area between the maximum diameter position and the bottom surface of the karst cave above the crossing layer. Grouting reinforcement is performed on this area, and grouting reinforcement is also performed on the karst cave area between the top surface of the crossing area and the lowest reinforcement area. While grouting reinforcement is being performed on this area, bag-type hole expansion anchor cables are used for auxiliary reinforcement, and the area between the top surface of the crossing area and the lowest reinforcement area is not included in the thickness of the reinforcement area.

[0041] The bag-type hole-enlarging anchor cable can use existing parts, including the anchor cable 5 and the bag 6, and the construction method can also use the existing technology. Its specific structure and construction method will not be described in detail here.

[0042] In this embodiment, the cave where the lowest reinforcement area is located is defined as the first cave.

[0043] Step 3.2: Determine the stability of the lowest reinforcement area. The determination method is as follows:

[0044] like Figure 4 As shown in the figure, the lowest reinforcement area is the current reinforcement area. The current reinforcement area above the shield machine is simplified into a simply supported beam model with the upper part bearing the pressure of the beaded cave soil. The maximum bending moment M max and the maximum shear force F s，max The calculation is as follows:

[0045]

[0046] q i =γ i z i (3)

[0047] q=γz (4)

[0048] 1—The bottom diameter of the soil in the current reinforcement layer.

[0049] q—The uniformly distributed load applied to the soil in the reinforcement area by the cave filling in the layer where the current reinforcement area is located.

[0050] q i —The uniformly distributed load applied to the soil in the current reinforcement area by the filling material in the i-th layer of cave above the current reinforcement area.

[0051] l i —The bottom diameter of the i-th layer of beaded caves above the current reinforcement area.

[0052] Z—The distance between the top surface of the reinforcement area of ​​the current layer and the bottom surface of the cave of the previous layer.

[0053] z i —The height of the i-th cave layer above the current reinforcement area.

[0054] γ- Bulk density of the filling material in the cave where the reinforcement area of ​​the current layer is located.

[0055] γ i -The bulk density of the filling material of the i-th layer of cave above the current reinforcement area.

[0056] Through the principle of moment superposition, the moment and shear force under different forces are obtained for superposition, and then according to the standard formula for beam failure judgment in material mechanics:

[0057]

[0058] Where, δ—maximum bending stress

[0059] M max —maximum bending moment;

[0060] W—bending section coefficient (known quantity);

[0061] l—the length of the reinforcement area of ​​the current layer, that is, the diameter of the bottom surface of the reinforcement area of ​​the current layer;

[0062] h—thickness of the reinforcement zone of the current layer;

[0063]

[0064] in, τ —Maximum shear stress

[0065] F s，max — maximum shear force;

[0066] S z —The static moment of the soil in the reinforcement area of ​​the current layer, which is calculated by the existing method according to the shape and size of the reinforcement area of ​​the current layer;

[0067] I z —The moment of inertia of the soil in the reinforcement area of ​​the current layer, which is calculated using existing methods based on the shape and size of the reinforcement area of ​​the current layer;

[0068] l—the length of the reinforcement area of ​​the current layer, that is, the diameter of the bottom surface of the reinforcement area of ​​the lowest layer;

[0069]

[0070] Where, [δ]—allowable stress;

[0071] δ b —Ultimate tensile strength (determined according to actual working conditions);

[0072] n—safety factor (determined according to actual working conditions);

[0073] According to the fourth strength theory, von Mises stress is used as the failure judgment index to perform strength verification. The strength condition is:

[0074]

[0075] If formula (8) is satisfied, the lowest reinforcement area is stable. In this case, the lowest reinforcement area can be used as the final reinforcement area. After the lowest reinforcement area is reinforced by grouting, shield tunneling construction can be carried out. If formula (8) is not satisfied, the lowest reinforcement area is unstable and the reinforcement measures are insufficient.

[0076] Step 3.3: If Figure 5 As shown in the figure, if the reinforcement measures are judged to be insufficient in step 3.2, it means that the lowest reinforced area is unstable. The cave (second cave) above the cave (first cave) where the lowest reinforced area is located should be reinforced using this technology to form a second reinforced area. The lowest reinforced area only bears the filling load of the cave where it is located, and the second reinforced area bears the load of the cave soil above it.

[0077] The second reinforcement area is the area between the maximum diameter position and the bottom surface of the cave.

[0078] Formula (1) to Formula (8) are used to judge the stability of the first reinforcement area and the second reinforcement area respectively. If both reinforcement areas are stable, the first reinforcement area and the second reinforcement area are the final reinforcement areas, and grouting reinforcement is performed. Figure 6 As shown, if the first reinforced area is still unstable, secondary reinforcement is performed. In this embodiment, a bag-type hole-expanding anchor cable is used for secondary reinforcement.

[0079] In step 3.4, if the second reinforced area is unstable, continue to reinforce the cave above the cave where the second reinforced area is located (the third cave) to form a third reinforced area, and repeat steps 3.2-3.3 to reinforce the nth layer of caves until each reinforced area can be judged to be stable.

[0080] After the grouting reinforcement is completed, the shield tunneling construction can be carried out to form a shield tunnel 3.

[0081] In a practical application of the reinforcement method of this embodiment, the beaded cave has two layers, and the shield tunnel passes through 3m below the maximum diameter of the lower beaded cave. After simplification, the maximum diameter of the lower cave is 5m, the bottom diameter of the upper cave is 2m, the distance from the maximum diameter of the lower cave to the top of the cave is 3m, the upper cave is 5m high, and the maximum diameter of the cave is 1m. The bulk density of the filling is 15KN / m 3 , the calculation method is as follows:

[0082] q=γz=15×3×1=45KN / m

[0083] q1=γ1z1=15×5×1=75KN / m

[0084]

[0085]

[0086] It can be concluded that the reinforced area is in a stable state. After grouting reinforcement of the reinforced area, shield crossing construction can be carried out.

[0087] With the reinforcement method of this embodiment, the reinforcement area does not cover the entire cave space. Therefore, when reinforcing the beaded cave, only the reinforcement area of ​​the set multi-layer cave is reinforced, rather than grouting reinforcement of all caves, which greatly reduces the processing and construction costs and shortens the processing and construction time. The reinforcement method of this embodiment provides a new theoretical support and technical method for tunnel construction under complex geological conditions, which can effectively evaluate and predict stability problems that may occur during the construction process, thereby significantly improving construction safety and having important application and promotion value.

[0088] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A reinforcement method for a shield tunnel passing through a beaded cave, characterized in that: From bottom to top, each layer of caves is reinforced in turn to form a reinforcement zone, until the reinforcement zone of the current layer is completed, and all completed reinforcement zones are judged to be able to remain stable; Among them, the method for determining the reinforcement area is: if the shield machine passes below the maximum diameter position of the karst cave in the crossing layer, then the lowest reinforcement area is the area between the top surface of the shield machine crossing area and the maximum diameter position of the karst cave in the crossing layer; if the shield machine passes above the maximum diameter position of the karst cave in the crossing layer, then the lowest reinforcement area is the area between the maximum diameter position and the bottom surface of the upper layer of the karst cave in the crossing layer, and the area between the lowest reinforcement area and the top surface of the crossing area is also reinforced; the remaining reinforcement areas are all the areas between the maximum diameter position of the corresponding layer of karst cave and the bottom surface of the karst cave.

2. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 1, characterized in that: After the current layer reinforcement area is reinforced, the stability of the reinforcement area of ​​the layer below the current layer reinforcement area is judged. If it is still unstable, the reinforcement area of ​​the layer below the current layer reinforcement area is reinforced for the second time.

3. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 2, characterized in that: Bag-type hole-enlarging anchor cables are used for secondary reinforcement.

4. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 1, characterized in that: The stability judgment method for the current layer reinforcement area is: The maximum bending moment and the maximum shear force of the current layer reinforcement area are obtained according to the load applied to the current layer reinforcement area by the karst cave filling material where the current layer reinforcement area is located and the load applied to the current layer reinforcement area by all karst cave filling materials above the karst cave where the current layer reinforcement area is located; The stability of the reinforcement area of ​​the current layer is determined based on the maximum bending moment and maximum shear force obtained.

5. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 4, characterized in that: The strength of the reinforced area of ​​the current layer is checked based on the obtained maximum bending moment and maximum stress combined with the fourth strength theory and von Mises stress as failure judgment indicators. The stability of the reinforced area of ​​the current layer is determined based on the strength check results.

6. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 4, characterized in that: When judging the stability of the current layer reinforcement area, the current layer reinforcement area is simplified to a simply supported beam model for calculation.

7. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 6, characterized in that: The length of the simply supported beam model is the diameter of the bottom surface of the reinforcement area of ​​the current layer, and the thickness of the simply supported beam model is the actual thickness of the reinforcement area of ​​the current layer.

8. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 1, characterized in that: After obtaining the maximum diameter position and the minimum diameter position of each layer of caves, each layer of caves is simplified into a cave with a quadrilateral vertical cross-section, and then the position of the reinforcement area is determined.

9. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 1, characterized in that: The reinforcement method for each reinforced area is grouting reinforcement.

10. A method for reinforcing a shield tunnel passing through a beaded cave as claimed in claim 1, characterized in that: When the shield machine passes above the maximum diameter position of the karst cave in the crossing layer, the area between the lowest reinforcement area and the top surface of the crossing area is reinforced by grouting, and bag-type hole expansion anchor cables are also used for auxiliary reinforcement.

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