Large-span beam type bearing platform structure and construction method thereof

Abstract

The invention relates to the technical field of bridge engineering, in particular to a large-span beam type bearing platform structure and a construction method thereof.The construction method comprises the following steps that S1, a first pile foundation and a second pile foundation are constructed on the two sides of an underground structure correspondingly; s2, a foundation pit is excavated to the top face of the first pile foundation and the top face of the second pile foundation, a cushion layer is constructed at the bottom of the pit, and then a temporary supporting layer is constructed on the cushion layer in the midspan area; s3, a support is installed on the top face of the second pile foundation; s4, a bearing platform is cast in place, one end of the bearing platform is fixedly connected with the first pile foundation, and the other end of the bearing platform is supported on the support; s5, a pier body and a platform body are poured on the top face of the bearing platform; and S6, the temporary supporting layer is removed, and a post-pouring section is poured between the bearing platform and the second pile foundation. Potential influence of a bridge structure on an underground structure below can be reduced, safety and durability of the bridge structure are ensured, influence on arrangement of ground auxiliary roads can be reduced, and meanwhile cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge engineering, and particularly relates to a long-span beam type bearing platform structure and a construction method thereof. Background Art

[0002] With the rapid development of urban construction, the problem of traffic congestion has become increasingly prominent. The urban roads urgently need to be developed and improved. However, the road construction conditions are becoming more and more complex and the traffic maintenance requirements are getting higher and higher, which puts forward very high requirements for design and construction.

[0003] During the process of bridge construction, it is often encountered that the layout of bridge piers is restricted by underground pipelines, tunnels or other structures. Using long-span structures on the ground is uneconomical and will also affect the layout of ground auxiliary roads. Therefore, it is necessary to design a long-span beam type bearing platform structure and a construction method thereof to overcome the above problems. Summary of the Invention

[0004] The purpose of the present invention is to provide a long-span beam type bearing platform structure and a construction method thereof, which can reduce the potential impact of the bridge structure on the underlying underground structure, reduce the impact on the layout of ground auxiliary roads, and reduce costs at the same time.

[0005] To achieve the above purpose, the technical solution of the present invention is a construction method of a long-span beam type bearing platform structure, including the following steps:

[0006] S1. Construct the first pile foundation and the second pile foundation respectively on both sides of the underground structure;

[0007] S2. Excavate the foundation pit to the top surfaces of the first pile foundation and the second pile foundation. First, construct a cushion layer at the bottom of the pit, and then construct a temporary support layer on the cushion layer in the mid-span area;

[0008] S3. Install a bearing on the top surface of the second pile foundation;

[0009] S4. Cast the bearing platform in-situ, so that one end of the bearing platform is consolidated with the first pile foundation, and the other end is supported on the bearing;

[0010] S5. Pour the pier body and the abutment body on the top surface of the bearing platform;

[0011] S6. Remove the temporary support layer, and pour a post-cast section between the bearing platform and the second pile foundation.

[0012] As one of the implementation manners, in step S4, after the bearing platform is constructed, install the first prestressed steel bundle in the bearing platform and tension and anchor it; in step S5, after the pier body and the abutment body are constructed, install the second prestressed steel bundle in the bearing platform and tension and anchor it.

[0013] As one of the implementation manners, in step S2, after the temporary support layer is constructed, a friction reducing layer is constructed on the surface of the temporary support layer.

[0014] As one of the implementation manners, in step S4, first, the bearing platform formwork is installed and a box chamber is reserved, then foam material is filled in the box chamber, and then the bearing platform is cast in place.

[0015] As one of the implementation manners, in step S4, when the bearing platform is cast in place, a groove is reserved at the position corresponding to the second pile foundation on the bottom surface of the bearing platform, and the bottom of the groove is supported on the bearing.

[0016] As one of the implementation manners, a lower steel plate is arranged on the top surface of the bearing, an upper steel plate is embedded at the bottom of the groove, and lubricating oil is smeared on the contact surface between the lower steel plate and the upper steel plate.

[0017] As one of the implementation manners, the temporary support layer is a sulfur mortar layer; in step S6, the sulfur mortar layer is melted by heating, and then the melted sulfur mortar is removed, so that the bearing platform in the mid-span area is suspended.

[0018] As one of the implementation manners, in step S2, when the sulfur mortar layer is constructed, heating elements are embedded in the sulfur mortar layer, and both ends of the heating elements extend out of the sulfur mortar layer.

[0019] As one of the implementation manners, the thickness of the cushion layer is 15 - 25 cm, and the thickness of the temporary support layer is 10 - 20 cm.

[0020] The present invention also provides a long-span beam type bearing platform structure, which includes a first pile foundation, a second pile foundation and a bearing platform; the first pile foundation, the second pile foundation and the bearing platform are all located below the ground surface, and the first pile foundation and the second pile foundation are respectively located on both sides of the underground structure, both ends of the bearing platform are respectively supported on the first pile foundation and the second pile foundation, and the bearing platform in the mid-span area is suspended above the soil body above the underground structure; a pier body and a abutment body are arranged on the top surface of the bearing platform and extend above the ground surface.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The present invention first constructs a temporary support layer on the cushion layer in the mid-span area, then casts in place the bearing platform, the pier body and the abutment body, and then removes the temporary support layer, so that there is a certain gap between the bearing platform in the mid-span area and the soil body below, avoiding the bearing platform, the pier body and the abutment body directly pressing on the soil body, thereby reducing the potential influence on the underground structure below (such as a subway tunnel or other structures).

[0023] (2) The present invention adopts the method of applying loads in batches and tensioning prestressed steel tendons in batches. By gradually increasing the stress state of the bearing platform, it avoids the structural damage or excessive deformation that may be caused by applying all loads at once. After the bearing platform is poured, the first prestressed steel tendon is tensioned first, enabling the bearing platform to expand and contract freely and release creep, without generating self-stress. This helps to reduce the lateral bending moment on the pile foundation, making it mainly bear vertical forces, thereby correspondingly reducing the amount of reinforcement in the pile foundation and lowering the construction cost. Then, after the pier body and abutment body are poured, the second prestressed steel tendon is tensioned to further improve the bearing capacity and stability of the bridge, ensuring the safety and durability of the bridge structure.

[0024] (3) The present invention constructs a friction-reducing layer on the surface of the temporary support layer, which can reduce the friction coefficient of the surface of the temporary support layer, helping the bearing platform to expand and contract freely on the temporary support layer during the tensioning of the prestressed steel tendon.

[0025] (4) When installing the formwork of the bearing platform, the present invention reserves a box chamber and fills the box chamber with foam materials. This can not only reduce the self-weight of the bearing platform but also prevent groundwater from seeping into the box chamber of the bearing platform and increasing its self-weight, helping to reduce the pressure on the foundation structure and the construction cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0027] Figure 1 It is a schematic diagram of the bearing platform of the long-span beam-type bearing platform structure provided by the embodiment of the present invention;

[0028] Figure 2 It is a schematic diagram of the long-span beam-type bearing platform structure provided by the embodiment of the present invention;

[0029] Figure 3 It is a cross-sectional view at the mid-span of the bearing platform provided by the embodiment of the present invention;

[0030] Figure 4 It is a cross-sectional view of the second pile foundation end of the bearing platform provided by the embodiment of the present invention;

[0031] Figure 5 It is a layout diagram of the prestressed steel tendons in the bearing platform;

[0032] Figure 6 For Figure 5 the layout diagram of the prestressed steel tendons of the A-A cross-section in

[0033] Figure 7 ForFigure 5 Prestressed steel bundle layout diagram of cross-section B-B;

[0034] Figure 8 For Figure 5 Prestressed steel bundle layout diagram of cross-section C-C;

[0035] In the figure: 1. Underground structure; 2. First pile foundation; 3. Second pile foundation; 4. Cushion layer; 5. Sulfur mortar layer; 6. Talcum powder layer; 7. Bearing platform; 8. Foam rubber; 9. Bearing; 10. Pier body; 11. Abutment body; 12. Post-cast section. Specific implementation manner

[0036] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0037] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention.

[0038] The terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0039] As Figures 1 - 8 shown, this embodiment provides a construction method for a long-span beam-type bearing platform structure, including the following steps:

[0040] S1. Construct the first pile foundation 2 and the second pile foundation 3 on both sides of the underground structure 1 respectively;

[0041] S2. Excavate the foundation pit to the top surfaces of the first pile foundation 2 and the second pile foundation 3. First, construct the cushion layer 4 at the bottom of the pit, and then construct a temporary support layer on the cushion layer 4 in the mid-span area;

[0042] S3. Install the bearing 9 on the top surface of the second pile foundation 3;

[0043] S4, cast-in-place cap 7, so that one end of the cap 7 is consolidated with the first pile foundation 2, and the other end is supported on the support 9;

[0044] S5, pouring the pier body 10 and the platform body 11 on the top surface of the cap 7;

[0045] S6, removing the temporary supporting layer, and pouring a post-casting section 12 between the cap 7 and the second pile foundation 3.

[0046] In this embodiment, a temporary support layer is first constructed on the cushion layer 4 in the mid-span area, and then the cap 7 and the pier body 10 and the platform body 11 are cast in situ, and then the temporary support layer is removed, so that there is a certain gap between the cap 7 in the mid-span area and the soil below, so as to avoid the cap 7 and the pier body 10 and the platform body 11 directly pressing on the soil, thereby reducing the potential impact on the underground structure 1 below (such as a subway tunnel or other structures).

[0047] The above embodiment is optimized. In step S4, after the construction of the cap 7 is completed, the first prestressed steel bundle is installed in the cap 7, and tensioned and anchored; in step S5, after the construction of the pier body 10 and the platform body 11 is completed, the second prestressed steel bundle is installed in the cap 7, and tensioned and anchored. This embodiment adopts the stepwise application of loads and the stepwise tensioning of prestressed steel bundles, and gradually increases the stress state of the cap 7 to avoid structural damage or excessive deformation caused by applying all loads at one time. After the cap 7 is cast, the first prestressed steel bundle is tensioned first, so that the cap 7 can freely expand and contract and release creep, and will not generate self-stress, which helps to reduce the lateral bending moment of the pile foundation, so that it mainly bears vertical force, thereby correspondingly reducing the number of reinforcements of the pile foundation and reducing construction costs. Then, after the pier body 10 and the platform body 11 are cast, the second prestressed steel bundle is tensioned, further improving the bearing capacity and stability of the bridge, and ensuring the safety and durability of the bridge structure.

[0048] In some embodiments, the first prestressed steel strand and the second prestressed steel strand in the cap 7 are arranged as shown in FIG. Figures 5 - 8As shown in the figure, where N1, N2, N1b, N1c, N2b, N3, N3a, N3b, N4, N4a, N5, and N6 are all the first prestressed steel tendons, and N1a, N2a, and N7 are all the second prestressed steel tendons. After the concrete strength and elastic modulus of the bearing platform 7 reach 90% of the design value and meet the age of not less than 7 days, the first prestressed steel tendons N1, N2, N1b, N1c, N2b, N3, N3a, N3b, N4, N4a, N5, and N6 are tensioned to the design value; after the concrete strength and elastic modulus of the pier body 10 and the abutment body 11 reach 90% of the design value and meet the age of not less than 7 days, the second prestressed steel tendons N1a, N2a, and N7 are tensioned to the design value. Among them, the first prestressed steel tendons N2, N2b, N3, N3a, N3b and the second prestressed steel tendon N7 are tensioned from one end, and the remaining steel tendons are tensioned symmetrically and simultaneously from both ends.

[0049] To optimize the above embodiment, in step S2, after the construction of the temporary support layer, a friction-reducing layer is constructed on the surface of the temporary support layer. In this embodiment, constructing a friction-reducing layer on the surface of the temporary support layer can reduce the friction coefficient of the surface of the temporary support layer, which helps the bearing platform 7 to freely expand and contract on the temporary support layer during the tensioning of the prestressed steel tendons.

[0050] Furthermore, the friction-reducing layer is a talcum powder layer 6 or a graphite layer, which not only has excellent lubrication performance and chemical stability, but also will not corrode the temporary support layer; the thickness of the friction-reducing layer is 0.1 - 1 mm, which can not only ensure the friction-reducing effect, but also avoid material waste and cost increase caused by excessive thickness.

[0051] To optimize the above embodiment, in step S4, first install the formwork of the bearing platform 7 and reserve a box chamber, then fill the box chamber with foam material, and then pour the bearing platform 7 in situ. In this embodiment, a box chamber is reserved when installing the formwork of the bearing platform 7 and filled with foam material, which can not only reduce the self-weight of the bearing platform 7, but also prevent groundwater from seeping into the box chamber of the bearing platform 7 and increasing the self-weight of the bearing platform 7, which helps to reduce the pressure on the foundation structure and the construction cost. Among them, the foam material has properties such as light weight, durability, and waterproofness. Preferably, the foam material is foam glue 8 or foamed concrete.

[0052] In step S4 of this embodiment, when pouring the bearing platform 7 in situ, a groove is reserved at the position corresponding to the second pile foundation 3 on the bottom surface of the bearing platform 7, and the bottom of the groove is supported on the bearing 9. As Figure 1 and Figure 3 shown, at one end of the bearing platform 7 close to the second pile foundation 3, a groove is reserved at the position corresponding to the second pile foundation 3, and at the position corresponding to the area between the second pile foundations 3, it is located on the cushion layer 4.

[0053] Optimize the above embodiment. A lower steel plate is provided on the top surface of the bearing 9, and an upper steel plate is embedded at the bottom of the groove, and lubricating oil is applied to the contact surface between the lower steel plate and the upper steel plate. In this embodiment, by fixing steel plates on the contact surfaces of the bearing 9 and the bearing platform 7 respectively and applying lubricating oil to the contact surfaces of the steel plates, friction can be reduced, so that when the first prestressed steel strand is tensioned, the horizontal force is not transmitted to the second pile foundation 3. Among them, tung oil can be used as the lubricating oil.

[0054] In this embodiment, the top surface of the bearing 9 is a plane with a height of about 4 cm. The bearing 9 can be removed before pouring the pier body 10 and the abutment body 11 in step S5, or the bearing 9 can be removed and directly poured into the post-cast section 12.

[0055] In some embodiments, the temporary support layer is a sulfur mortar layer 5; in step S6, the sulfur mortar layer 5 is melted by heating, and then the melted sulfur mortar is removed to make the bearing platform 7 in the mid-span area suspended. During the melting process of the temporary support layer, appropriate tools or equipment can be used to assist the flow and discharge of the sulfur mortar. Optimally, the top surface of the cushion layer 4 can be inclined downward from the first pile foundation 2 to the second pile foundation 3 with a slope of 1-1.5% to facilitate the timely automatic discharge of the melted sulfur mortar.

[0056] Furthermore, in step S2, when constructing the sulfur mortar layer 5, heating elements are embedded in the sulfur mortar layer 5, and both ends of the heating elements extend out of the sulfur mortar layer 5. Both ends of the heating elements extend out of the temporary support layer and are connected to the switch and the power supply. In this embodiment, the switch can be used to control the power supply to the heating elements, so as to heat the temporary support layer by the heating elements. Among them, the heating elements can adopt resistance wires, electric heating tubes, etc.

[0057] In this embodiment, the thickness of the cushion layer 4 is 15-25 cm, and the thickness of the temporary support layer is 10-20 cm. Preferably, the thickness of the cushion layer 4 is 20 cm, and the thickness of the temporary support layer is 15 cm. In actual construction, the thicknesses of the cushion layer 4 and the temporary support layer should be selected and adjusted according to specific conditions.

[0058] This embodiment also provides a long-span beam-type bearing platform structure, including a first pile foundation 2, a second pile foundation 3 and a bearing platform 7; the first pile foundation 2, the second pile foundation 3 and the bearing platform 7 are all located below the ground, and the first pile foundation 2 and the second pile foundation 3 are respectively located on both sides of the underground structure 1, and both ends of the bearing platform 7 are respectively supported on the first pile foundation 2 and the second pile foundation 3, and the bearing platform 7 in the mid-span area is suspended above the soil body above the underground structure 1; piers 10 and abutment bodies 11 are provided on the top surface of the bearing platform 7 and extend above the ground.

[0059] The above construction will be described below through a specific embodiment.

[0060] A construction method for a long-span beam-type bearing platform structure includes the following steps:

[0061] S1. Level the site, and construct the first pile foundation 2 and the second pile foundation 3 on both sides of the underground structure 1 respectively; the first pile foundation 2 and the second pile foundation 3 adopt bored cast-in-place piles.

[0062] S2. Excavate the foundation pit to the top surface of the first pile foundation 2 and the second pile foundation 3. First, construct a cushion layer 4 at the bottom of the pit, then construct a sulfur mortar layer 5 on the cushion layer 4 in the mid-span area, embed resistance wires in the sulfur mortar layer 5, and then lay a talcum powder layer 6 on the sulfur mortar layer 5.

[0063] S3. Install a bearing 9 on the top surface of the second pile foundation 3, and fix a lower steel plate on the top surface of the bearing 9.

[0064] S4. Install the formwork of the bearing platform 7 and reserve a box chamber, then fill the box chamber with foam rubber 8. At the same time, reserve a groove and embed an upper steel plate at the position corresponding to the second pile foundation 3, and apply tung oil on the contact surface between the lower steel plate and the upper steel plate. Then, cast the bearing platform 7 in situ, so that one end of the bearing platform 7 is consolidated with the first pile foundation 2, and the other end is supported on the bearing 9; install the first prestressed steel bundles N1, N2, N1b, N1c, N2b, N3, N3a, N3b, N4, N4a, N5, N6 in the bearing platform 7, and tension and anchor them.

[0065] S5. Remove the bearing 9, and pour the pier body 10 and the abutment body 11 on the top surface of the bearing platform 7; install the second prestressed steel bundles N1a, N2a, N7 in the bearing platform 7, and tension and anchor them.

[0066] S6. Energize the resistance wires to heat up, melt the sulfur mortar layer 5, then remove the melted sulfur mortar, and pour a post-cast section 12 between the bearing platform 7 and the second pile foundation 3 to consolidate the other end of the bearing platform 7 with the second pile foundation 3.

[0067] After step S6 is completed, construct the superstructure of the bridge and the bridge deck auxiliary facilities, and open to traffic after the bridge is completed.

[0068] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A construction method for a large-span beam-type bearing platform structure, characterized in that, It includes the following steps: S1. Construct the first pile foundation and the second pile foundation respectively on both sides of the underground structure; S2. Excavate the foundation pit to the top surfaces of the first pile foundation and the second pile foundation. First, construct the cushion layer at the bottom of the pit, and then construct the temporary support layer on the cushion layer in the mid-span area; S3. Install the bearing on the top surface of the second pile foundation; S4. Cast the cap in-situ, making one end of the cap consolidated with the first pile foundation and the other end supported on the bearing; S5. Pour the pier body and the abutment body on the top surface of the cap; S6. Remove the temporary support layer, and pour the post-cast section between the cap and the second pile foundation.

2. The construction method of the long-span beam-type pile cap structure according to claim 1, characterized in that: In step S4, after the cap is constructed, install the first prestressed steel bundle in the cap and tension and anchor it; in step S5, after the pier body and the abutment body are constructed, install the second prestressed steel bundle in the cap and tension and anchor it.

3. The construction method of the long-span beam type pile cap structure according to claim 2, characterized in that: In step S2, after the temporary support layer is constructed, construct the friction-reducing layer on the surface of the temporary support layer.

4. The construction method of the long-span beam-type pile cap structure according to claim 1, characterized in that: In step S4, first install the formwork of the cap and reserve the box chamber, then fill the box chamber with foam material, and then cast the cap in-situ.

5. The construction method of the long-span beam-type bearing platform structure according to claim 1, characterized in that: In step S4, when casting the cap in-situ, reserve a groove at the position corresponding to the second pile foundation on the bottom surface of the cap, and the bottom of the groove is supported on the bearing.

6. The construction method of the long-span beam type bearing platform structure according to claim 5, characterized in that: A lower steel plate is arranged on the top surface of the bearing, an upper steel plate is embedded at the bottom of the groove, and lubricating oil is smeared on the contact surface between the lower steel plate and the upper steel plate.

7. The construction method of the long-span beam-type pile cap structure according to claim 1, characterized in that: The temporary support layer is a sulfur mortar layer; in step S6, melt the sulfur mortar layer by heating, and then remove the melted sulfur mortar to make the cap in the mid-span area suspended.

8. The construction method of the long-span beam-type bearing platform structure according to claim 7, characterized in that: In step S2, when constructing the sulfur mortar layer, embed heating elements in the sulfur mortar layer and extend both ends of the heating elements out of the sulfur mortar layer.

9. The construction method of the long-span beam-type bearing platform structure according to claim 1, characterized in that: The thickness of the cushion layer is 15 - 25 cm, and the thickness of the temporary support layer is 10 - 20 cm.

10. A large-span beam-type bearing platform structure, characterized in that: It includes the first pile foundation, the second pile foundation and the cap; the first pile foundation, the second pile foundation and the cap are all below the ground surface, and the first pile foundation and the second pile foundation are respectively located on both sides of the underground structure. Both ends of the cap are supported on the first pile foundation and the second pile foundation respectively, and the cap in the mid-span area is suspended above the soil body above the underground structure; the pier body and the abutment body are arranged on the top surface of the cap and extend above the ground surface.

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