A construction method for a permeable immersed tube foundation structure

Abstract

This invention relates to a construction method for a permeable immersed tube foundation structure. First, a down-the-hole hammer drilling technique is used to quickly drill holes for the pile foundation to a depth of at least 6 meters into moderately weathered rock. Then, a leveling layer at the bottom of the permeable wall and a large-volume concrete cushion layer are poured. Finally, the permeable wall is poured section by section to form a permeable channel. This invention utilizes a down-the-hole hammer for rapid drilling into the rock, improving the efficiency of pile foundation construction. The cast-in-place wall and large-volume concrete cushion layer are constructed using prefabricated steel formwork, enabling the use of interchangeable steel formwork, quick formwork erection and dismantling, and ensuring the quality of the final product. The large-volume concrete cushion layer is poured in layers and strips, allowing for accurate control of the slope of the top surface of the large-volume concrete. This invention offers strong operability and high construction efficiency, creating favorable conditions for shortening the construction cycle.

Description

Technical Field

[0001] This invention relates to the technical field of underwater immersed tunnel construction, and in particular to a construction method for a permeable immersed tunnel foundation structure. Background Technology

[0002] To meet the requirements of the national marine use policy, the cast-in-place immersed tube foundation of the Dalian Bay Subsea Tunnel must have both load-bearing and water-permeable functions. The foundation consists of rock-inserted piles, slab walls, and a large-volume concrete cushion layer, and water-permeable channels are reserved between the slab walls. Therefore, a more reasonable construction method is required. Summary of the Invention

[0003] This invention aims to provide a permeable immersed tube foundation construction method for the Dalian Bay undersea tunnel, which is designed to enable more efficient construction of cast-in-place immersed tube foundations.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] A construction method for a permeable immersed tube foundation structure, the specific steps of which are as follows:

[0006] S1, Cast-in-place piles at the bottom of the permeable wall.

[0007] First, the location of the borehole is measured and positioned on the foundation rock layer. A down-the-hole hammer is used to drill into the foundation rock layer. At the same time, the pile foundation steel cage is tied at the rear site. Then, the steel cage is hoisted and placed on site and the pile foundation concrete is poured. Finally, the pile head treatment of the cast-in-place pile is completed.

[0008] S2, Pouring the leveling layer

[0009] A leveling layer is poured on top of the excavated foundation rock layer. The leveling layer is controlled by both flatness and elevation to ensure that the reserved height of the permeable channel is not less than 2.3m.

[0010] S3. Concrete foundation layer poured in sections.

[0011] The top surface of the concrete foundation has a 4% slope and is poured in two layers, with the thickness of the upper layer controlled at 0.2m.

[0012] S4. Construct permeable pleated walls section by section.

[0013] The permeable wall has construction joints on the bottom surface of the cast-in-place pipe, so that the cast-in-place pipe and the permeable wall are cast separately. Each permeable channel has three permeable walls.

[0014] S5. Complete the foundation construction of the immersed tunnel.

[0015] Twenty-eight days after the permeable wall and concrete cushion layer are poured, a polyurea anti-corrosion coating is sprayed onto the surface of the permeable wall and concrete cushion layer at the permeable channel, and debris inside the permeable channel is cleaned up, thus completing the foundation structure construction of the permeable immersed tube.

[0016] In step S1, the control pile head extends 5cm into the permeable wall.

[0017] In step S3, the layered pouring method is as follows:

[0018] First, erect a 4m high prefabricated steel formwork on the already poured leveling layer. Mark the top elevation of the lower concrete layer on the steel formwork. The pouring height of the lower concrete layer is between 2.1m and 3.8m. When pouring concrete, control the layer to not exceed 0.5m and simultaneously vibrate it evenly by hand.

[0019] When the strength of the lower concrete pad reaches 50% of the design strength, the top elevation of the upper concrete pad is marked on the 4m high steel formwork. The upper concrete pad is poured to a height of 0.2m. It is then poured in strips along the design slope, with each strip being 2m wide. The surface is then manually finished and precisely leveled.

[0020] Finally, cover the concrete subbase with a geotextile membrane and water it for at least 10 days to prevent cracking of the concrete subbase surface.

[0021] In step S4, the specific construction method for the permeable wall is as follows:

[0022] First, the steel bars for the wall section are manually tied on the already poured leveling layer, and the steel bars reserved at the top of the wall section extend into the cast-in-place sinking pipe bottom slab.

[0023] Then erect 4m high prefabricated steel formwork;

[0024] Finally, mark the top elevation of the permeable wall on the steel formwork. When pouring the permeable wall concrete, the thickness of each layer should not exceed 0.5m, and manual vibration should be carried out simultaneously. After demolding, cover the surface of the permeable wall with a geotextile membrane and water it for curing for no less than 10 days.

[0025] In steps S3 and S4, the assembled steel formwork is made according to the maximum depth of the foundation structure of the immersed tube and the minimum width of the permeable wall. The maximum height of a single steel formwork piece is 4m, the maximum width is 2m, and the weight of a single piece does not exceed 1.5t. It can be hoisted single piece or assembled into a whole for hoisting.

[0026] In steps S3 and S4, the steel formwork is reinforced by two tie rods at the top and bottom, with a tie rod spacing of 1m. The bottom tie rod must be a water-stop type tie rod.

[0027] In steps S3 and S4, to ensure the rigidity and strength of the template itself, a 6mm thick steel plate is used as the panel, 8# channel steel is used as the horizontal strip with a spacing of 0.5m, and double 22# channel steel is used as the vertical strip with a spacing of 1m.

[0028] The beneficial effects of this invention are as follows: It employs a down-the-hole hammer for rapid rock drilling, improving the efficiency of pile foundation construction; the cast-in-place slab walls and large-volume concrete cushion layers utilize modular steel formwork, enabling the reuse and interchangeability of steel formwork, quick formwork erection and dismantling, and guaranteed structural quality; the large-volume concrete cushion layer employs a layered and strip-casting method, achieving accurate control of the slope of the top surface of the large-volume concrete. This invention offers strong operability and high construction efficiency, creating favorable conditions for shortening the construction cycle. Attached Figure Description

[0029] Fig. 1 This is a schematic elevation view of the permeable immersed tube foundation structure of the present invention;

[0030] Fig. 2 This is a schematic cross-sectional view of the permeable immersed tube foundation structure of the present invention;

[0031] In the diagram: 1-Submerged pipe; 2-Foundation rock layer; 3-Cast-in pile; 4-Leveling layer; 5-Permeable wall; 6-Concrete foundation; 7-Permeable channel;

[0032] The following will describe in detail, with reference to the accompanying drawings, embodiments of the present invention. Detailed Implementation

[0033] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. The advantages and features of the invention will become clearer from the following description and claims. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the invention.

[0034] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0036] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0037] like Figs. 1-2 As shown, a construction method for a permeable immersed tube foundation structure includes the following specific steps:

[0038] S1, the grouting pile 3 at the bottom of the permeable wall 5.

[0039] First, the location of the drilling hole is measured on the foundation rock layer 2. The hole is drilled in the foundation rock layer 2 using a down-the-hole hammer. At the same time, the pile foundation steel cage is tied in the rear area. Then, the steel cage is hoisted and placed on site and the pile foundation concrete is poured. Finally, the pile head treatment of the cast-in-place pile 3 is completed, and the pile head is controlled to extend 5cm into the permeable wall 5.

[0040] S2, Pouring leveling layer 4

[0041] A leveling layer 4 is poured on top of the excavated foundation rock layer 2. The leveling layer 4 is controlled by both flatness and elevation to ensure that the reserved height of the permeable channel 7 is not less than 2.3m.

[0042] S3, pour concrete foundation layer in sections 6

[0043] The top surface of the concrete foundation 6 has a 4% slope and is poured in two layers, with the thickness of the upper layer controlled at 0.2m.

[0044] In step S3, the layered pouring method is as follows:

[0045] First, erect a 4m high assembled steel formwork on the already poured leveling layer 4. Mark the top elevation of the lower concrete layer 6 on the steel formwork. The pouring height of the lower concrete layer 6 is between 2.1m and 3.8m. When pouring concrete, control the layer to not exceed 0.5m and simultaneously vibrate it evenly by hand.

[0046] When the strength of the lower concrete pad 6 reaches 50% of the design strength, the top elevation of the upper concrete pad 6 is marked on the 4m high steel formwork. The upper concrete pad 6 is poured to a height of 0.2m. It is then poured in strips along the design slope, with each strip being 2m wide. The surface is then finished and leveled manually.

[0047] Finally, cover the surface of concrete cushion layer 6 with geotextile membrane and water it for curing for no less than 10 days to prevent cracking of the surface of concrete cushion layer 6.

[0048] S4. Construct permeable pleated wall sections in stages.

[0049] The permeable wall 5 is divided into construction joints on the bottom surface of the cast-in-place pipe 1, so that the cast-in-place pipe 1 and the permeable wall 5 are cast separately. A single permeable channel 7 is provided with three permeable walls 5.

[0050] The specific construction method for permeable sheet wall 5 is as follows:

[0051] First, the reinforcing bars of the wall are manually tied on the leveling layer 4 that has been poured. The pre-reserved reinforcing bars at the top of the wall extend into the bottom slab of the cast-in-place pipe 1.

[0052] Then erect 4m high prefabricated steel formwork;

[0053] Finally, draw lines on the steel formwork to mark the top elevation of the permeable wall 5. When pouring the concrete of the permeable wall 5, the thickness of each layer should not exceed 0.5m, and manual vibration should be performed simultaneously. After demolding, cover the surface of the permeable wall 5 with a geotextile membrane and water it for curing for no less than 10 days.

[0054] S5. Complete the foundation construction of immersed tube 1.

[0055] Twenty-eight days after the permeable wall 5 and concrete cushion 6 are poured, a polyurea anti-corrosion coating is sprayed on the surface of the permeable wall 5 and concrete cushion 6 at the permeable channel 7, and debris in the permeable channel 7 is cleaned up, thus completing the foundation structure construction of the permeable immersed tube 1.

[0056] In steps S3 and S4, the assembled steel formwork is manufactured according to the maximum depth of the foundation structure of the immersed tube 1 and the minimum width of the permeable wall 5. The maximum height of a single steel formwork piece is 4m, the maximum width is 2m, and the weight of a single piece does not exceed 1.5t. It can be hoisted individually or assembled into a whole for hoisting. The steel formwork is reinforced by two tie rods at the top and bottom with a spacing of 1m. The bottom tie rod must be a water-stop type tie rod. To ensure the rigidity and strength of the formwork itself, a 6mm thick steel plate is used as the panel, 8# channel steel is used as the horizontal band with a spacing of 0.5m, and double 22# channel steel is used as the vertical band with a spacing of 1m. Specific Implementation Example 1:

[0058] A construction method for a permeable immersed tube foundation structure, which rapidly completes the drilling of the cast-in-place pile 3 using a down-the-hole hammer process, and pours the foundation leveling layer 4 and permeable sheet wall 5 to form a permeable channel 7.

[0059] In this embodiment, the construction of the foundation piles and permeable wall 5 is as follows: a permeable channel 7 is set every 15m along the foundation of the sinking pipe 1, and three permeable walls 5 are set in each permeable channel 7. Each permeable wall 5 is 41.3m long, 2m wide, and no less than 2.3m high. At the same time, six 1m diameter cast-in-place piles 3 are set at the bottom of each permeable wall 5.

[0060] Construction technology and quality requirements: The cast-in-place pile 3 must be drilled into the moderately weathered foundation rock layer 2 for no less than 6m, and the height of the cast-in-place permeable wall 5 shall not be less than 2.3m.

[0061] The construction of the foundation piles and permeable wall 5 for the permeable pipe 1 includes the following steps:

[0062] The location of the borehole was measured on the foundation rock layer 2. The down-the-hole hammer equipment was used to quickly drill the hole in the moderately weathered foundation rock layer 2 with a drilling efficiency of 2m / h. After cleaning the hole, the steel cage was hoisted and lowered. Finally, the pile foundation concrete was poured and the pile head was treated to control the pile head concrete to extend 5cm into the permeable wall 5.

[0063] A leveling layer is poured on top of the excavated moderately weathered rock surface. Because the actual foundation rock surface depth and elevation are not uniform, the leveling layer needs to control both flatness and top elevation to ensure that the reserved height of the permeable channel is not less than 2.3m.

[0064] On the foundation leveling layer 4, the line is laid out to determine the edge line of the permeable wall 5. The wall reinforcement is tied manually on site, and the top of the wall reinforcement extends into the bottom plate of the sinking pipe 1.

[0065] After the wall reinforcement is inspected and approved, general-purpose 4m×2m steel formwork is erected one by one. The steel formwork is hoisted into place. The formwork is connected by bolts. The top of the steel formwork is fixed by φ20mm tie rods, and the bottom is reinforced by φ20mm waterstops. The spacing of the tie rods is controlled at 1m. Diagonal braces are set on the back of the formwork to control the verticality of the formwork.

[0066] The theoretical elevation for pouring the permeable sheet wall 5 was determined by measurement, and lines were simultaneously drawn on the steel formwork as a reference for pouring.

[0067] When pouring concrete for the permeable sheet wall 5, the thickness of each layer should not exceed 0.5m, and it should be formed by manual vibration.

[0068] After the poured concrete reaches its final set, the top surface of the permeable wall 5 is roughened manually to remove the laitance on the top surface of the concrete and expose the aggregate, thereby increasing the bonding force between the permeable wall 5 structure and the upper submerged pipe 1.

[0069] After demolding, cover the surface of the permeable sheet wall 5 with a geotextile membrane to retain moisture, and at the same time spray water for curing for no less than 10 days to prevent cracks from forming.

[0070] Twenty-eight days after the concrete pouring of the permeable wall was completed, the surface of the permeable wall 5 was cleaned and a polyurea anti-corrosion coating was applied.

[0071] After the above basic construction processes are completed, the debris in the permeable channel 7 is cleaned up, and after acceptance, it is handed over to the next process. Specific Implementation Example 2:

[0073] A construction method for a permeable immersed tube foundation structure is proposed, which uses a general-purpose steel formwork that can be applied to large-volume concrete cushion layers 6 with heights ranging from 2.3m to 4m. At the same time, a layered and strip-based pouring method is adopted to control and align the top surface of the large-volume concrete cushion layer 6 with a design slope of 4%.

[0074] The construction of the large-volume concrete cushion layer 6 involved in this embodiment is as follows: a large-volume concrete cushion layer 6 is set every 15m of the foundation of the immersed tube 1. The length of a single large-volume concrete cushion layer 6 is 41.3m, the width is 15m, and the height is not less than 2.3m. The top surface of the concrete cushion layer 6 is designed to have a slope of 4%.

[0075] Construction technology and quality requirements: The slope deviation of the top surface of the large-volume concrete cushion layer 6 shall not exceed ±5mm, and no harmful cracks shall appear on the surface of the concrete cushion layer 6.

[0076] The construction of the large-volume concrete foundation layer 6 specifically includes the following steps:

[0077] A leveling layer 4 is poured on top of the excavated moderately weathered foundation rock layer 2. Because the actual foundation rock surface depth and elevation are not uniform, the leveling layer 4 needs to control both flatness and top elevation to ensure that the reserved height of the permeable channel 7 is not less than 2.3m.

[0078] To accurately align the 4% slope of the top surface of the large-volume concrete foundation layer 6, it was poured in two layers, with the upper layer thickness controlled at 0.2m and the lower layer thickness not less than 2.1m.

[0079] On the foundation leveling pad 4, the design edge line of the large volume concrete pad 6 is determined by laying out the lines. A general-purpose 4m×2m steel formwork is erected according to the layout line position. The steel formwork is hoisted into place, and each formwork is connected by bolts. Diagonal bracing is installed on the back of the formwork to control the verticality of the formwork.

[0080] The theoretical elevation for pouring the large-volume concrete foundation layer 6 was determined by measurement and marked on the steel formwork. The pouring height of the lower concrete foundation layer 6 is between 2.1m and 3.8m.

[0081] When pouring the concrete foundation layer 6, the height of each layer should be controlled to not exceed 0.5m, and manual vibration should be used in conjunction with the pouring.

[0082] When the strength of the lower concrete cushion layer 6 reaches 50% of the design strength, the top elevation of the upper concrete cushion layer 6 is marked on the steel formwork for the second time. The pouring height of the upper concrete cushion layer 6 is only 0.2m.

[0083] The concrete was poured in sections along the designed slope, with each section being 2 meters wide. The surface was then manually finished and precisely leveled.

[0084] Finally, cover the surface of the concrete cushion layer 6 with a geotextile membrane for moisture retention, and spray water for curing for no less than 10 days to prevent cracking of the large-volume concrete surface.

[0085] Twenty-eight days after the large-volume concrete foundation 6 is poured, the surface of the concrete foundation 6 is cleaned and a polyurea anti-corrosion coating is applied. After acceptance, it is handed over to the next construction process.

[0086] This invention uses a down-the-hole hammer to quickly drill into the rock, improving the efficiency of pile foundation construction; the cast-in-place permeable wall 5 and the large-volume concrete cushion 6 are constructed using assembled steel formwork, which enables the steel formwork to be reusable and versatile, and the formwork can be quickly erected and dismantled while ensuring the quality of the actual structure; the large-volume concrete cushion 6 is constructed using a layered and strip-casting method, which enables accurate control of the slope of the top surface of the large-volume concrete cushion 6.

[0087] This invention is highly operable and efficient in construction, creating favorable conditions for shortening the construction cycle.

[0088] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A method of construction of a water permeable immersed tube foundation structure, characterised in that, The specific steps are as follows: S1, pouring pile (3) at the bottom of the water permeable sheet wall (5) First, measure and locate the drilling position on the foundation rock stratum (2), drill into the foundation rock stratum (2) using a down-the-hole hammer, and then bind the pile foundation reinforcement cage on the rear site. Then, hoist and place the reinforcement cage on site and pour the pile foundation concrete. Finally, complete the pile head treatment of the pouring pile (3); S2, pouring and leveling the cushion layer (4) Pour the leveling cushion layer (4) on the upper part of the excavated foundation rock stratum (2), and control the flatness and elevation of the leveling cushion layer (4) to ensure that the reserved height of the water permeable channel (7) is not less than 2.3m; S3, pouring the concrete cushion layer (6) in sections The top surface of the concrete cushion layer (6) has a slope of 4%, and it is poured in two layers, with the thickness of the upper layer controlled to be 0.2m; The specific steps are as follows: First, erect a 4m high assembled steel formwork on the poured leveling cushion layer (4), and mark the top elevation of the lower concrete cushion layer (6) on the steel formwork. The pouring height of the lower concrete cushion layer (6) is between 2.1m and 3.8m, and the concrete is poured in layers with a thickness not exceeding 0.5m, and is synchronously and evenly vibrated by hand; When the strength of the lower concrete cushion layer (6) reaches 50% of the design strength, mark the top elevation of the upper concrete cushion layer (6) on the 4m high steel formwork again. The pouring height of the upper concrete cushion layer (6) is 0.2m, and the pouring is again carried out in strips along the design slope direction, with a single strip pouring width of 2m, and the surface is collected and precisely leveled by hand; Finally, cover the surface of the concrete cushion layer (6) with a film geotextile, and water curing for not less than 10 days to prevent the surface of the concrete cushion layer (6) from cracking; S4, pouring the water permeable sheet wall (5) in sections The water permeable sheet wall (5) is divided into construction joints on the bottom surface of the cast-in-place pipe (1), so that the cast-in-place pipe (1) and the water permeable sheet wall (5) are poured separately, and each section of the water permeable channel (7) is provided with three water permeable sheet walls (5); The specific steps are as follows: First, manually bind the sheet wall reinforcement on the poured leveling cushion layer (4), and the top reinforcement of the sheet wall extends into the bottom plate of the cast-in-place pipe (1); Then, erect a 4m high assembled steel formwork; Finally, mark the top elevation of the water permeable sheet wall (5) on the steel formwork, and pour the concrete of the water permeable sheet wall (5) in layers with a thickness not exceeding 0.5m, and synchronously and evenly vibrate by hand. After demolding, cover the surface of the water permeable sheet wall (5) with a film geotextile, and water curing for not less than 10 days; S5, complete the foundation construction of the pipe (1) After 28 days of pouring of the water permeable sheet wall (5) and the concrete cushion layer (6), spray a polyurea anticorrosive coating on the surface of the water permeable sheet wall (5) and the concrete cushion layer (6) at the water permeable channel (7), and complete the cleaning of the debris in the water permeable channel (7), and complete the foundation structure construction of the water permeable pipe (1).

2. A construction method of a water permeable immersed tube foundation structure according to claim 1, wherein In step S1, control the pile head to extend into the water permeable sheet wall (5) by 5cm.

3. A construction method of a water permeable immersed tube foundation structure according to claim 2, wherein In steps S3 and S4, the assembled steel formwork is made according to the maximum depth of the foundation structure of the pipe (1) and the minimum width of the water permeable sheet wall (5), with a maximum height of 4m and a maximum width of 2m for a single steel formwork, and a weight of not more than 1.5t for a single steel formwork. The single steel formwork is hoisted or multiple steel formworks are combined to form a whole for hoisting.

4. A construction method of a water permeable immersed tube foundation structure according to claim 3, wherein In steps S3 and S4, the steel formwork is reinforced by two top and bottom pull rods, with a 1m interval between the pull rods, wherein the bottom pull rod is of a water-stopping type.

5. A construction method of a water permeable immersed tube foundation structure according to claim 4, wherein In steps S3 and S4, in order to ensure the rigidity and strength of the formwork, a 6mm-thick steel plate is used as the face plate, an 8# channel steel is used as the horizontal band with a 0.5m interval, and a double-spliced 22# channel steel is used as the vertical band with a 1m interval.

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