Concrete box pipe jacking receiving method

Abstract

The application discloses a concrete box top pipe receiving method, which comprises the following steps: S1, end reinforcement: erecting a working support platform at a hole door position, performing drilling operation, and performing grouting when the drilling reaches a grouting depth; and S2, concrete box wall construction: constructing two concrete box outer walls with a wall width of 400 mm at the receiving end hole door, reserving a hole door, adopting C30 concrete for the outer wall, adopting double-layered φ22@300 for horizontal and vertical steel bars, adopting φ12@450*450 for a pulling hook steel bar, and adopting a chiseling and reinforcing method for connecting a part connected with a main structure. In the process of tunneling, the top pipe receiving has a large pushing force, the application adopts a cast-in-place reinforced concrete box structure, is safer and more stable in stress, is convenient in construction, is high in efficiency, and solves the technical problems of high technical requirements, easy deformation and easy influence on sealing performance of a steel box structure in the prior art.

Description

Technical Field

[0001] This invention relates to the field of pipe jacking technology, and more specifically to a method for receiving jacking pipes in a concrete box. Background Technology

[0002] The geological conditions at the pipe jacking receiving end are poor, with numerous pipelines and close proximity to the existing Metro Line 5 and municipal roads. The end lacks ground reinforcement conditions, making it prone to water and sand inrush during pipe jacking, potentially causing ground subsidence and posing safety risks to the metro line, with significant social impact. Existing pipe jacking receiving methods utilize steel box housings, but due to the diverse shapes and sizes of pipes, it's difficult to utilize existing steel boxes. Specially manufactured steel boxes are required, which are welded, demanding high technical skill. The quality of welding affects structural safety, and after a certain number of uses, the steel box structure is prone to deformation, compromising overall sealing and resulting in high costs and poor economic efficiency.

[0003] This invention provides a method for receiving jacking pipes in a concrete box, which aims to ensure safe reception of the jacking pipe by filling the box with foamed concrete in a cast-in-place concrete box in the receiving well. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings and provide a method for receiving concrete box-type jacking pipes.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for receiving concrete box jacking pipes, comprising the following steps:

[0006] S1. End reinforcement: Erect a working support platform at the tunnel entrance and carry out drilling operations. Grouting is carried out after drilling reaches the grouting depth.

[0007] S2. Construction of concrete box wall: Construct two 400mm wide concrete box walls at the receiving end door, and reserve the door. The outer wall uses C30 concrete. The horizontal and vertical steel bars are arranged in double layers of φ22@300. The tie bars are φ12@450×450. The connection with the main structure is made by roughening and planting steel bars.

[0008] S3. Portal exploration holes: Before conducting portal exploration holes, water-soluble polyurethane sealant is injected into the outer ring of the portal to stop the water from entering the gap between the retaining structure and the reinforced body. The spacing between the injection holes is 1.5m.

[0009] S4. Portal Removal and Backfilling: When removing the portal, first remove the surface concrete and cut the reinforcing steel. Divide the diaphragm wall portal after stripping the reinforcing steel into two sections: inner (70cm on the station side) and outer (30cm on the soil-facing side). Remove the first layer of the portal using a breaker until the second layer of reinforcing steel on the soil-facing side is reached. When removing the portal on the soil-facing side, divide the portal into 11 layers at 50cm intervals. Remove the concrete in a bottom-up order. Use double-liquid grout for backfilling and counter-pressure, and then backfill with foamed concrete.

[0010] S5. Pipe Jacking Machine Reception: After the tunnel portal is completely excavated and foamed concrete backfilling is completed, the pipe jacking machine is prepared for reception. The pipe jacking machine exits the tunnel at a 50° angle to the original main structure. When the left cutterhead in the excavation direction completes the cutting of the original soil and reaches the soil-facing side of the diaphragm wall, the right cutterhead is about 6.5m away from the soil-facing side of the diaphragm wall. At this time, the left side is about to cut the backfill, while the right side continues to cut the original soil. This may cause the face to tilt due to uneven hardness. The attitude can be stabilized by actively hinged the pipe jacking machine and adjusting the slag discharge speed of the left and right augers.

[0011] S6. Tunnel Portal Sealing: The tunnel portal sealing for pipe jacking is carried out in three stages. The first stage is when the pipe jacking machine is received, and double-liquid grout is injected into the pipe section for temporary sealing to prevent water and sand inrush after the pipe jacking machine exits the tunnel. After the first sealing, the box wall is demolished using a 200mm crusher. After demolition, the second stage of tunnel portal sealing is carried out by constructing the tunnel portal ring beam structure. The gap between the tunnel portal and the pipe section is sealed by welding a steel plate around the entire ring, and then double-liquid grout is injected to enhance the temporary sealing effect. After the tunnel portal ring beam structure is completed, single-liquid grout is used for the third stage of tunnel portal sealing to completely fill the gap and achieve the functions of complete filling and water stoppage.

[0012] Furthermore, in S1, because there are pipelines on the ground, the grouting pressure at the holes above the waist of the tunnel portal is controlled within 0.5 MPa, and the grouting pressure below the waist of the tunnel portal is controlled within 0.8 MPa.

[0013] Furthermore, during grouting, after reaching the grouting pressure, a small amount of retraction is performed, and the injection speed is slowed down. The drilling and grouting machine is adjusted to the lowest speed setting, and pressure is stabilized during injection. If the pressure gauge pointer fluctuation range decreases and the pressure stabilization effect is achieved, the drill is pulled back 50cm. Throughout the grouting process, the surrounding pipeline wells and the ground are monitored and inspected. If grout leakage occurs, grouting is stopped immediately. Grouting is resumed only after the leakage at the leakage location stops and the gap is sealed.

[0014] Furthermore, the grout used for grouting is mainly a mixture of liquid A and liquid C, or liquid B and liquid C, injected through the pores. Liquid A is water and cement mixed at a mass ratio of 1:1.1, liquid B is water and water glass mixed at a volume ratio of 3:1, and liquid C is water and phosphoric acid mixed at a mass ratio of 20:1.

[0015] Furthermore, after construction is completed, the unconfined compressive strength of the reinforced body after 28 days should not be less than 0.8 MPa; a water permeability test should be conducted, and the permeability coefficient should not exceed 1×10⁻⁶. -6 After the drilling and core sampling is completed, the gaps should be sealed with M10 cement mortar in a timely manner, and the grouting pressure should not be less than 0.3 MPa.

[0016] Furthermore, in step S3, after the polyurethane sealant is injected, a exploratory hole is drilled at a depth of 1.8m to observe whether there is a water flow channel. If water leakage occurs, the leak is sealed by injecting polyurethane sealant or injecting two-component grout. The number of exploratory holes should be no less than 12. If water leakage occurs, the number of exploratory holes should be increased according to the actual situation. The spacing between exploratory holes should be dynamically controlled according to the actual situation on site.

[0017] Furthermore, in S4, during the construction of each layer, the concrete of the wall is first completely demolished and cleaned up, and finally the steel bars on the soil-facing side of the ground wall are cut off. After the cutting is completed, double-liquid grout is immediately used for backfilling and counter-pressure to minimize the exposure time of the tunnel entrance and reduce the risk of water and sand inrush at the tunnel entrance.

[0018] Furthermore, in S4, a temporary support frame is erected between the first and second basement levels before the tunnel entrance is removed. During the backfilling and tunnel exit stages, the stress on the first basement level is distributed by the middle slab of the second basement level and its structure.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) During the tunneling process, the thrust of the pipe jacking receiver is large. The present invention adopts a cast-in-place reinforced concrete box structure, which is safer and more stable under force, and is convenient to construct and has higher efficiency. In addition, the cast-in-place concrete box structure solves the technical problems of high technical requirements, easy deformation and easy to affect the sealing of the steel box structure in the prior art.

[0021] (2) The dimensions of the cast-in-place concrete box structure of the present invention are flexible and can be adjusted according to the size of the pipe jacking machine, thus avoiding the problem of huge waste of costs caused by the inability to recycle specially customized steel boxes. Attached Figure Description

[0022] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0023] Figure 1 This is a schematic diagram of the exterior wall of a concrete box according to an embodiment of the present invention.

[0024] Figure 2 This is a schematic diagram of the grouting point locations according to an embodiment of the present invention.

[0025] Figure 3 This is a schematic diagram of the excavation and backfilling of a hole in an embodiment of the present invention. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figure 1-3 .

[0028] The present invention provides a method for receiving concrete box-type jacking pipes, comprising the following steps:

[0029] S1. End reinforcement: A working support platform is erected at the tunnel entrance to carry out drilling operations. Grouting is carried out after drilling reaches the grouting depth. Due to the presence of pipelines on the ground, the grouting pressure of the holes above the tunnel entrance waist is controlled within 0.5 MPa, and the grouting pressure of the holes below the tunnel entrance waist is controlled within 0.8 MPa.

[0030] S2. Construction of concrete box wall: Construct two 400mm wide concrete box walls at the receiving end door, and reserve the door. The outer wall uses C30 concrete. The horizontal and vertical steel bars are arranged in double layers of φ22@300. The tie bars are φ12@450×450. The connection with the main structure is made by roughening and planting steel bars.

[0031] S3. Portal exploration holes: Before conducting portal exploration holes, water-soluble polyurethane sealant is injected into the outer ring of the portal to stop the water from entering the gap between the retaining structure and the reinforced body. The spacing between the injection holes is 1.5m.

[0032] S4. Portal Removal and Backfilling: When removing the portal, first remove the surface concrete and cut the reinforcing steel. Divide the diaphragm wall portal after stripping the reinforcing steel into two sections: inner (70cm on the station side) and outer (30cm on the soil-facing side). Remove the first layer of the portal using a breaker until the second layer of reinforcing steel on the soil-facing side is reached. When removing the portal on the soil-facing side, divide the portal into 11 layers at 50cm intervals. Remove the concrete in a bottom-up order. Use double-liquid grout for backfilling and counter-pressure, and then backfill with foamed concrete.

[0033] S5. Pipe Jacking Machine Reception: After the tunnel portal is completely excavated and foamed concrete backfilling is completed, the pipe jacking machine is prepared for reception. The pipe jacking machine exits the tunnel at a 50° angle to the original main structure. When the left cutterhead in the excavation direction completes the cutting of the original soil and reaches the soil-facing side of the diaphragm wall, the right cutterhead is about 6.5m away from the soil-facing side of the diaphragm wall. At this time, the left side is about to cut the backfill, while the right side continues to cut the original soil. This may cause the face to tilt due to uneven hardness. The attitude can be stabilized by actively hinged the pipe jacking machine and adjusting the slag discharge speed of the left and right augers.

[0034] S6. Tunnel Portal Sealing: The tunnel portal sealing for pipe jacking is carried out in three stages. The first stage is when the pipe jacking machine is received, and double-liquid grout is injected into the pipe section for temporary sealing to prevent water and sand inrush after the pipe jacking machine exits the tunnel. After the first sealing, the box wall is demolished using a 200mm crusher. After demolition, the second stage of tunnel portal sealing is carried out by constructing the tunnel portal ring beam structure. The gap between the tunnel portal and the pipe section is sealed by welding a steel plate around the entire ring, and then double-liquid grout is injected to enhance the temporary sealing effect. After the tunnel portal ring beam structure is completed, single-liquid grout is used for the third stage of tunnel portal sealing to completely fill the gap and achieve the functions of complete filling and water stoppage.

[0035] In one embodiment, during grouting, after reaching the grouting pressure, a small amount of retraction (about 10cm) is performed, and the injection speed is slowed down. The drilling and grouting machine is adjusted to the lowest speed setting, and pressure is stabilized during injection. If the fluctuation range of the pressure gauge pointer decreases and the pressure stabilization effect is achieved, the drill is retracted and lifted by 50cm. Throughout the grouting process, the surrounding pipeline wells and the ground are monitored and inspected. If grout leakage occurs, grouting is stopped immediately. Grouting is resumed only after the leakage at the leakage location stops and the gap is sealed.

[0036] In one embodiment, the materials for preparing the grout are mainly cement, water glass, and phosphoric acid. The cement used is 42.5 ordinary Portland cement, the water glass is 50 Baume water glass, and the phosphoric acid is 85% industrial phosphoric acid. The grout used for injection is mainly a mixture of liquid A and liquid C, or liquid B and liquid C, for injection through the pores. Liquid A is water and cement prepared at a mass ratio of 1:1.1, liquid B is water and water glass prepared at a volume ratio of 3:1, and liquid C is water and phosphoric acid prepared at a mass ratio of 20:1.

[0037] Since solution C can react with either solution A or B, care should be taken to prevent solution C from mixing into solutions A or B during mixing. The specific ratio should be adjusted according to the setting time to ensure that the slurry setting time is controlled at around 20 seconds. The setting time should not be too long (not more than 25 seconds), otherwise the slurry may spread too far and the reinforcement effect will be poor. The setting time should not be too short (not less than 15 seconds), otherwise it may cause frequent pipe blockage or the pressure to increase too quickly, resulting in pipeline damage.

[0038] In one embodiment, after construction is completed, the unconfined compressive strength of the reinforced body after 28 days should not be less than 0.8 MPa; a water permeability test should be conducted, and the permeability coefficient should not be greater than 1 × 10⁻⁶. -6 After the drilling and core sampling is completed, the gaps should be sealed with M10 cement mortar in a timely manner, and the grouting pressure should not be less than 0.3 MPa.

[0039] In one embodiment, in step S3, after the polyurethane sealant is injected, a exploratory hole is drilled at a depth of 1.8m to observe whether there is a water flow channel. If water leakage is found, the leak is sealed by injecting polyurethane sealant or injecting a two-component grout. The number of exploratory holes should be no less than 12. If water leakage occurs in the exploratory holes, the number of holes can be increased according to the actual situation. The spacing between the exploratory holes is dynamically controlled according to the actual situation on site.

[0040] In one embodiment, during the S4 construction process, the concrete of the wall is first completely demolished and cleaned up, and then the reinforcing steel bars on the soil-facing side of the ground wall are cut off. After the cutting is completed, double-liquid grout is immediately used for backfilling and counter-pressure to minimize the exposure time of the tunnel entrance and reduce the risk of water and sand inrush at the tunnel entrance.

[0041] In one embodiment, in S4, a temporary support frame is erected between the first and second basement levels before the tunnel entrance is removed, and the stress on the first basement level is distributed by the middle slab of the second basement level and its structure during the backfilling and tunnel exit stages.

[0042] Preferably, the polyurethane sealant is a commercially available product, so its specific components will not be described here.

[0043] This invention has been successfully applied to the 50° inclined receiving end of the jacking pipe at the D2 entrance / exit of Dashadong Station on Guangzhou Metro Line 7 Phase II. Compared with conventional receiving schemes under the same working conditions, the economic benefits are analyzed as shown in Table 1 below:

[0044] Table 1. Economic Benefit Analysis Table

[0045]

[0046]

[0047] Comparative analysis shows that, under the same working conditions, the conventional receiving scheme costs approximately 2.254 million yuan, while the cost of this method is only 645,000 yuan, saving approximately 1.609 million yuan.

[0048] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within the present invention.

Claims

1. A method for receiving concrete box-type jacking pipes, characterized in that: Includes the following steps: S1. End reinforcement: Erect a working support platform at the tunnel entrance and carry out drilling operations. Grouting is carried out after drilling reaches the grouting depth. S2. Construction of concrete box wall: Construct two 400mm wide concrete box walls at the receiving end door, and reserve the door. The outer wall uses C30 concrete. The horizontal and vertical steel bars are arranged in double layers of φ22@300. The tie bars are φ12@450×450. The connection with the main structure is made by roughening and planting steel bars. S3. Portal exploration holes: Before conducting portal exploration holes, water-soluble polyurethane sealant is injected into the outer ring of the portal to stop the water from entering the gap between the retaining structure and the reinforced body. The spacing between the injection holes is 1.5m. S4. Portal Removal and Backfilling: When removing the portal, first remove the surface concrete and cut the reinforcing steel. Divide the diaphragm wall portal after stripping the reinforcing steel into two sections for segmented removal. The first layer of the portal is removed using a breaker until the second layer of reinforcing steel on the soil-facing side is reached. When removing the portal on the soil-facing side, divide the portal into 11 layers at 50cm intervals. Remove the concrete in a bottom-up order, and use double-liquid grout for backfilling and counter-pressure, followed by foamed concrete backfilling. S5. Pipe Jacking Machine Reception: After the tunnel portal is completely excavated and foamed concrete backfilling is completed, preparations are made for the pipe jacking machine to be received. The pipe jacking machine exits the tunnel at a 50° angle to the original main structure. When the left cutterhead in the excavation direction completes the cutting of the original soil and reaches the soil-facing side of the diaphragm wall, the right cutterhead is 6.5m away from the soil-facing side of the diaphragm wall. At this time, the left side is about to cut the backfill, while the right side continues to cut the original soil. The attitude is stabilized by the active hinge of the pipe jacking machine and the different discharge speeds of the left and right augers. S6. Tunnel Portal Sealing: The tunnel portal sealing for pipe jacking is carried out in three stages. The first stage is when the pipe jacking machine is received, and double-liquid grout is injected into the pipe section for temporary sealing to prevent water and sand inrush after the pipe jacking machine exits the tunnel. After the first sealing, the box wall is demolished using a crusher. After demolition, the second stage of tunnel portal sealing is carried out by constructing the tunnel portal ring beam structure and sealing the gap between the tunnel portal and the pipe section by welding a steel plate around the entire circle, followed by double-liquid grout injection. After the tunnel portal ring beam structure is completed, single-liquid grout is used for the third stage of tunnel portal sealing.

2. The method for receiving concrete box-type jacking pipes as described in claim 1, characterized in that: In S1, there are pipelines on the ground. The grouting pressure at the holes above the waist of the tunnel portal is controlled within 0.5 MPa, and the grouting pressure below the waist of the tunnel portal is controlled within 0.8 MPa.

3. The method for receiving concrete box-type jacking pipes as described in claim 1 or 2, characterized in that: During grouting, after reaching the grouting pressure, first retreat slightly and slow down the injection speed. Adjust the drilling and grouting machine to the lowest speed setting, stabilize the pressure during injection, and when the pressure stabilization effect is achieved, retreat and lift the drill by 50cm.

4. The method for receiving concrete box-type jacking pipes as described in claim 1 or 2, characterized in that: The grout used for grouting is mainly composed of a mixture of liquid A and liquid C, or liquid B and liquid C, for injection through the pores. Liquid A is a mixture of water and cement at a mass ratio of 1:1.1, liquid B is a mixture of water and water glass at a volume ratio of 3:1, and liquid C is a mixture of water and phosphoric acid at a mass ratio of 20:

1.

5. The method for receiving concrete box-type jacking pipes as described in claim 1 or 2, characterized in that: After construction is completed, the unconfined compressive strength of the reinforced body after 28 days should not be less than 0.8 MPa; a water permeability test should be conducted, and the permeability coefficient should not be greater than 1×10⁻⁶. -6 After the drilling and core sampling is completed, the gaps should be sealed with M10 cement mortar in a timely manner, and the grouting pressure should not be less than 0.3 MPa.

6. The method for receiving concrete box-type jacking pipes as described in claim 1 or 2, characterized in that: In step S3, after the polyurethane sealant is injected, a exploratory hole is drilled at a depth of 1.8m to observe whether there is a water flow channel. If water leakage occurs, the leak is sealed by injecting polyurethane sealant or injecting two-component grout. The number of exploratory holes should be no less than 12. If water leakage occurs, the number of exploratory holes should be increased according to the actual situation. The spacing between exploratory holes should be dynamically controlled according to the actual situation on site.

7. The method for receiving concrete box-type jacking pipes as described in claim 1 or 2, characterized in that: In S4, during the construction of each layer, the concrete of the wall is first completely demolished and cleaned up, and then the steel bars on the soil-facing side of the ground wall are cut off. After the cutting is completed, double-liquid grout is immediately used for backfilling and counter-pressure to minimize the exposure time of the tunnel entrance and reduce the risk of water and sand inrush at the tunnel entrance.

8. The method for receiving concrete box-type jacking pipes as described in claim 1 or 2, characterized in that: In S4, a temporary support frame is erected between the first and second basement levels before the tunnel entrance is removed. During the backfilling and exiting stages, the middle slab of the second basement level and its structure are used to distribute the stress on the middle slab of the first basement level.

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