Double-column stepped caisson and support structure suitable for long-span bridge

Abstract

The application discloses a double-column stepped caisson and support structure suitable for large-span bridges and relates to the field of bridge caisson foundations. The double-column stepped caisson suitable for large-span bridges comprises a stepped assembly and an erosion reduction assembly. The stepped assembly is arranged along the water flow direction and comprises a caisson lower step with a plurality of axial through holes and a double-column upper step extending upward from the top surface of the caisson lower step and being hollow and through the caisson lower step holes. The double-column upper step comprises two protruding column bodies arranged at intervals. The erosion reduction assembly comprises a first flow guide unit arranged at the bottom of each protruding column body and a second flow guide unit arranged at the bottom between the two protruding column bodies. The first flow guide unit comprises a sharp end for shearing water flow, and the second flow guide unit is provided with recessed curved surfaces on both sides for guiding the sheared water flow. The application can control the self-weight, reduce the consumption of materials, improve the water flow erosion on the water-approaching side, and reduce the sediment accumulation on the water-backing side.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bridge caisson foundation, in particular to a double-column stepped caisson and support structure suitable for large-span bridges. BACKGROUND

[0002] As a bridge foundation, the self-weight of the caisson accounts for a large proportion in the bridge load, especially when the bearing stratum is weak, the self-weight of the caisson accounts for more than 50% in the bridge load. Nowadays, the span of bridges is increasing, and the construction conditions of bridges are becoming more and more complex. Therefore, in order to adapt to higher construction requirements and make the bridge structure safe and reliable, the requirements for scour reduction and bearing capacity of the caisson foundation are also increasing. In order to adapt to the bearing requirements of large-span bridges, the following measures are often taken during the design of the caisson foundation: (1) expanding the cross-sectional area of the caisson structure to utilize a larger caisson structure base area to bear the load of large-span bridges; (2) increasing the buried depth of the caisson structure to make the bearing capacity per unit area of the caisson base stronger.

[0003] In the past engineering practice, both the expansion of the cross-sectional area of the caisson and the increase of the buried depth of the caisson have been widely used, and the technology is relatively mature. However, both of the above-mentioned methods will greatly increase the construction cost of the bridge. In particular, after the cross-sectional area of the caisson structure is expanded, it means that the caisson structure will be subjected to a greater flow scouring force. At the same time, after the caisson structure is sunk, it will be subjected to long-term scouring by the flow, which will form a scour pit at the front end of the caisson structure and form a silt accumulation at the rear end of the caisson structure. This imbalance of local scouring and silt accumulation at the front and rear will increase the risk of construction of the top surface of the step outside the cofferdam, and even cause uneven settlement during the operation period, which will cause safety hazards. SUMMARY

[0004] The purpose of the present application is to provide a double-column stepped caisson and support structure suitable for large-span bridges, in order to solve the technical problems in the prior art that the cross-sectional area of the caisson structure in the large-span bridge is correspondingly increased, which not only leads to an increase in construction cost, but also causes a scour pit to be formed at the front end and a silt accumulation to be formed at the rear end of the caisson structure after the cross-sectional area of the larger caisson structure is subjected to flow impact, resulting in uneven settlement and safety hazards.

[0005] In a first aspect, the present application provides a double-column stepped caisson suitable for large-span bridges, comprising:

[0006] A step assembly is arranged along the flow direction, which comprises a caisson lower step having a plurality of axially through holes, and a double-column upper step extending upward from the top surface of the caisson lower step and being hollow and through the holes of the caisson lower step, the double-column upper step comprising two protruding column bodies arranged along the length direction of the caisson lower step.

[0007] The scouring reduction assembly comprises first flow guide units arranged at the bottom of the two protruding columns and a second flow guide unit arranged at the bottom between the two protruding columns, the first flow guide units comprise sharp ends for shearing water flow, the sharp ends of the two first flow guide units are respectively used for facing the water side and the backwater side, and the second flow guide unit is provided with recessed curved surfaces on both sides for guiding the sheared water flow.

[0008] In an embodiment, the water side and the backwater side of the caisson lower step are provided with circular arc end faces.

[0009] In an embodiment, the bottom of the caisson lower step is provided with a caisson bottom sealing area.

[0010] In an embodiment, the top of the caisson lower step is provided with a step cover plate for sealing the well hole.

[0011] In an embodiment, the top of the double-column upper step is provided with a top bearing platform for connecting the structure above the bridge.

[0012] In an embodiment, the horizontal cross-sectional area of the bottom of the top bearing platform is greater than the horizontal cross-sectional area of the protruding column.

[0013] In an embodiment, the first flow guide unit comprises two oppositely arranged flow guide plates, and one side of the two flow guide plates is separated from each other, and the other side is gathered to form a sharp end.

[0014] In an embodiment, the second flow guide unit comprises two oppositely arranged flow guide plates.

[0015] In an embodiment, the flow guide plates have a certain curvature, and the curved surfaces of the two flow guide plates are close to each other to form a recessed curved surface.

[0016] In a second aspect, the embodiments of the present application provide a bridge support structure, which comprises the double-column step caisson described above, and the top of the double-column upper step of the double-column step caisson is provided with a bridge tower for supporting the bridge.

[0017] The technical scheme provided by the embodiments of the present application has the following beneficial effects:

[0018] 1. The double-column step caisson suitable for large-span bridges provided by the present application can bear the double-column upper step through the caisson lower step, and compared with the traditional method of simply expanding the cross-sectional area of a single caisson, such a structure has better economic benefits under the premise of meeting the stability.

[0019] 2. The double-column stepped caisson suitable for large-span bridges provided by the application has a reduced cross-sectional size of the upper step of the caisson compared to the lower step of the caisson, which can reduce the amount of material and save the investment of funds, and the reduced water-blocking area caused by the double-column structure can effectively reduce the scouring, and the water flow can be accelerated again when passing through the rear end column due to the reduced water passage section, and in addition, the stepped structure formed by the upper step of the double column and the lower step of the caisson can preliminarily consume the energy of the water flow when the water flow passes through the double-column stepped caisson in the application.

[0020] 3. The double-column stepped caisson suitable for large-span bridges provided by the application is provided with a first flow guide unit and a second flow guide unit, wherein the front end first flow guide unit effectively suppresses the formation of the undercutting water flow, which can effectively reduce the scouring of the riverbed by the horseshoe vortex, and the second flow guide unit and the rear end first flow guide unit can shear and guide the water flow, further reducing the sediment accumulation at the rear end. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0022] Figure 1 A double-column stepped caisson structure suitable for large-span bridges provided by an embodiment of the application;

[0023] Figure 2 Another embodiment of a protruding column in a double-column stepped caisson suitable for large-span bridges provided by an embodiment of the application;

[0024] Figure 3 A cross-sectional view of a double-column stepped caisson suitable for large-span bridges provided by an embodiment of the application;

[0025] Figure 4 A top view of a double-column stepped caisson suitable for large-span bridges provided by an embodiment of the application;

[0026] Figure 5 A bridge support structure provided by an embodiment of the application.

[0027] In the drawings: 1, lower step of caisson; 101, circular arc end face water passage end; 102, step cover plate; 2, upper step of double column; 201, protruding column; 3, first flow guide unit; 301, flow guide plate; 4, second flow guide unit; 401, flow guide plate; 5, caisson bottom sealing area; 6, top bearing platform; 7, bridge tower. DETAILED DESCRIPTION

[0028] In order to make the personnel in the technical field better understand the scheme of the present application, the technical scheme in the embodiments of the present application will be clearly and completely described below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by the person skilled in the art without creative labor are within the scope of protection of the present application.

[0029] In a first aspect, the embodiments of the present application provide a double-column stepped caisson suitable for a large-span bridge, which can solve the technical problems of the prior art that the cross section of the caisson structure in the large-span bridge is increased, resulting in increased construction cost, and that a scour pit is formed at the front end and silt is formed at the rear end of the large caisson structure after long-term water flow impact, resulting in uneven settlement and causing safety hazards.

[0030] The double-column stepped caisson in the present application includes a stepped assembly and a scour reduction assembly. The stepped assembly is used to form the stepped caisson foundation structure in the present application and can greatly reduce the water-blocking area of the upper part of the foundation. The stepped assembly is embedded in the riverbed to provide foundation support for the bridge. The double-column upper step breaks out of the riverbed and reaches above the water surface, greatly reducing the water-blocking area of the foundation and effectively improving the foundation scouring situation. At the same time, when the water flow passes through the rear end of the stepped assembly, it can be accelerated again based on the structure of the scour reduction assembly, reducing the silt accumulation at the rear end of the double-column stepped caisson. The scour reduction assembly is arranged on the stepped assembly. The double-column stepped caisson in the present application is arranged in the flow direction. The scour reduction assembly can first contact the water flow, shear and guide the water flow, prevent it from accumulating on the outer periphery of the stepped assembly, and reduce the silt accumulation, thereby further improving the foundation scouring condition.

[0031] Specifically, Figure 1 A double-column stepped caisson structure suitable for a large-span bridge is provided in the embodiments of the present application, as shown in Figure 1 The stepped assembly in the present application includes a stepped caisson lower step 1 having a plurality of axially through shaft holes, and a double-column upper step 2 extending upward from the top surface of the stepped caisson lower step 1 and being hollow inside and through the shaft holes of the stepped caisson lower step 1. The double-column upper step 2 includes two spaced apart protruding column bodies 201.

[0032] The lower step 1 of the caisson is made of a hollow metal shell filled with concrete. It has several well holes that penetrate the lower step 1 of the caisson. This structure can not only significantly reduce the self-weight of the double-column stepped caisson, but also, during the sinking process, the well holes can serve as channels for discharging mud and sand, making it easier for the double-column stepped caisson to sink to the designed depth. In one possible embodiment of this application, the lower step 1 of the caisson has a long strip cross-section. When assembled, the lower step 1 of the caisson is arranged in the transverse direction of the bridge to conform to the direction of water flow. The length of the long side of the lower step 1 of the caisson is not less than the width of the bridge, and the wide side of the lower step 1 of the caisson faces the direction of water flow to reduce the scouring force of the water flow.

[0033] The two protruding columns 201 in the double-column upper step 2 are spaced apart along the length of the lower step 1 of the caisson and are fixedly connected to the lower step 1 of the caisson. The double-column upper step 2 is made of the same material and is manufactured in the same way as the lower step 1 of the caisson. The top of the double-column upper step 2 extends vertically upward and protrudes a certain height from the surface of the lower step 1 of the caisson to form a step shape.

[0034] As an optional embodiment, Figure 2 This application provides a schematic diagram of another embodiment of a protruding column 201 in a double-column stepped caisson suitable for long-span bridges, as shown in the following example. Figure 2 As shown, the cross-section of the protruding column 201 can be any shape, such as a circle or a semi-circle, as long as the outer side of the protruding column 201 has an arc surface, which is not limited in this application.

[0035] It should be noted that in this article, "outer side" refers to the side where the two protruding columns 201 are far apart from each other, namely the water-facing side and the back side, while "inner side" refers to the side where the two protruding columns 201 are close to each other. This will not be repeated in the following text.

[0036] Furthermore, the scour reduction assembly includes a first flow guiding unit 3 provided at the bottom of the outer side of each of the two protruding columns 201 and a second flow guiding unit 4 located at the bottom between the two protruding columns 201. The first flow guiding unit 3 has an open top and includes a sharp end for shearing the water flow. The sharp ends of the two first flow guiding units 3 are respectively directed toward the water-facing side and the water-repelling side. The second flow guiding unit 4 has an open top and concave curved surfaces on both sides for guiding the sheared water flow.

[0037] Each of the protruding columns 201 is provided with a set of first flow guiding units 3, one end of which is fixedly connected to the outer side of the protruding column 201, and the other end forms a sharp end and protrudes towards the direction of the water flow. The caisson lower step 1 is arranged in the flow direction. Based on the structural arrangement, the two protruding columns 201 are also arranged in front of and behind the direction of the water flow, so that the sharp ends of the two first flow guiding units 3 are respectively directed towards the water-facing side and the water-leaving side. When the water flow carries the sediment through the first flow guiding unit 3 located on the water-facing side, the first flow guiding unit 3 will first separate the water flow, reducing the direct scouring of the protruding column 201 provided with the first flow guiding unit 3, and the first flow guiding unit 3 located on the water-leaving side can be used to assist in guiding the sheared water flow, reducing the sediment accumulation phenomenon at the rear end of the caisson.

[0038] The second flow guiding unit 4 is arranged between the two protruding columns 201, and the length direction of the second flow guiding unit 4 is also arranged in the water flow direction. The sheared water flow will pass through the concave curved surfaces on both sides of the second flow guiding unit 4. Due to the reduction of the water passage section, the water flow is accelerated, so that the water flow produces scouring. At the same time, the concave curved surface can use the power of the flowing water to guide the water flow to the protruding column 201 located at the rear end, and then guide the water flow again through the first flow guiding unit 3 on the double-column upper step 2 located at the rear end, using the scouring force to further reduce the sediment accumulation phenomenon at the rear end.

[0039] The caisson lower step 1 and the double-column upper step 2 can control the basic self-weight of the double-column step caisson in the present application. Compared with the traditional method of simply expanding the cross-sectional area of a single caisson, it has better stability and supporting force. At the same time, the setting of the double-column upper step 2 not only reduces the material consumption of the overall structure and saves capital investment, but also, due to the stepped structure of the caisson lower step 1 and the double-column upper step 2, the energy of the water flow passing through the double-column step caisson in the present application is preliminarily consumed in the form of shearing. The cross section of the double-column upper step 2 is small, which can also reduce the impact of the water flow on the overall double-column step caisson in the present application. In combination with the first flow guiding unit 3 and the second flow guiding unit 4, the water flow can be further sheared and guided. At the same time, due to the reduction of the water section, the sheared water flow can also increase the flow rate, thereby generating greater scouring force, further avoiding the sediment accumulation phenomenon. The structure is complementary and interacts.

[0040] Further, Figure 3 A double-column step caisson cross-sectional view suitable for large-span bridges is provided for the embodiments of the present application, as shown in Figure 3As shown, the water-facing side and the backwater side of the caisson lower step 1 are both provided with a circular arc end face flow end 101. In combination with the above description, the narrower side of the caisson lower step 1 faces the water flow direction, and the circular arc end face flow end 101 is arranged on the two narrow sides of the caisson lower step 1 to face the water-facing side and the backwater side. Based on this structure, the resistance of the two ends when the water flows through the caisson lower step 1 can be reduced, and the stress caused by the water flow load can be more evenly distributed, thereby reducing the water scouring force on the overall double-column step caisson in the present application.

[0041] Further, as shown in Figure 3 , the bottom of the caisson lower step 1 is provided with a caisson bottom sealing area 5, which covers the entire bottom surface of the caisson lower step 1, and is used to form a solid bottom sealing structure by pouring concrete. This bottom sealing structure not only significantly increases the stress area and overall weight of the bottom surface of the caisson lower step 1, but also enables it to better disperse and withstand loads from above and the sides, thereby improving its overall stability and greatly enhancing the anti-overturning capability of the double-column step caisson in the present application. Even under the action of external loads such as water flow, the double-column step caisson can remain stable and will not tilt or collapse due to uneven stress.

[0042] At the same time, as an optional embodiment, the bottom surface of the caisson lower step 1 is divided into several pouring areas. When performing the bottom sealing operation, the caisson bottom sealing area 5 can be partitioned and poured. Workers can adopt appropriate pouring strategies and equipment according to the characteristics and needs of different areas, thereby improving work efficiency. Through partitioned pouring, the pouring of concrete in each area can be ensured to be more uniform. This helps to form a solid bottom sealing structure, improve overall stability and carrying capacity, and at the same time, partitioned pouring of concrete also helps quality control. Workers can monitor and manage the pouring process of each area more carefully to ensure that the quality and performance of the concrete meet the design requirements.

[0043] Further, as shown in Figure 3 , the top of the caisson lower step 1 is provided with a step cover plate 102 for sealing the well hole to prevent silt from entering the well hole. The cross section of the step cover plate 102 is consistent with the cross section of the caisson lower step 1 and a through hole is reserved for the protruding column body 201 to tightly cover the caisson lower step 1.

[0044] Further, as shown in Figure 3 , the top of the double-column upper step 2 is provided with a top bearing platform 6 for connecting the structure above the bridge, and the horizontal cross-sectional area of the bottom of the top bearing platform 6 is greater than the horizontal cross-sectional area of the protruding column body 201, so that the top bearing platform 6 completely covers the top of the double-column upper step 2. Through the larger cross-sectional top bearing platform 6, the overall stability of the top bearing platform 6 can be increased and the carrying capacity can be improved, preventing shaking or collapse due to uneven stress, and more effectively distributing and transferring loads to make the overall stress of the top bearing platform 6 more uniform.

[0045] Further, Figure 4 A double-column stepped caisson for large-span bridge is provided in the embodiment of the present application, as shown in Figure 4 The first flow guide unit 3 includes two oppositely arranged flow guide plates 301, and the two flow guide plates 301 are separated from each other on one side and gathered on the other side to form a sharp end. The two flow guide plates 301 are longitudinally arranged along the height direction of the protruding column 201, and the two flow guide plates 301 are respectively connected to the outer wall of one of the protruding columns 201 on the side separated from each other. The two flow guide plates 301 are gathered on the other side to form a sharp end, so as to be directed towards the water side and the backwater side, respectively.

[0046] Further, Figure 4 The second flow guide unit 4 includes two oppositely arranged flow guide plates 401, and the two flow guide plates 401 have a certain curvature and the curved surfaces of the two flow guide plates 401 are close to each other to form a concave curved surface. The two sides of the flow guide plate 401 are respectively connected to the inner wall of the two protruding columns 201. This design helps to guide the sheared water flow to flow along a specific path, reducing the accumulation of sediment at the rear end of the caisson.

[0047] In the construction of the double-column stepped caisson in the present application, the caisson lower step 1 and the double-column upper step 2 are constructed in sequence according to the design size, and then the caisson lower step 1 and the double-column upper step 2 are sunk to the bottom. After sinking to the position, the concrete bottom sealing and the step cover plate 102 are installed, and then the top bearing platform 6 is constructed, and the first flow guide unit 3 and the second flow guide unit 4 are installed.

[0048] The double-column stepped caisson in the present application can form a stepped structure by setting the caisson lower step 1 and the double-column upper step 2 with a smaller cross section than the caisson lower step 1. While controlling the self-weight of the double-column stepped caisson, reducing the overall material consumption of the structure and saving the capital investment, the large water-blocking cross section of the double-column upper step 2 can effectively reduce the erosion, and the water flow will be accelerated again when passing through the rear end column, reducing the sediment accumulation at the rear end of the caisson. In addition, when the water flow passes through the caisson lower step 1, the water flow is preliminarily consumed in the form of shearing by the stepped structure, further reducing the impact of the water flow on the foundation. By setting the first flow guide unit 3 and the second flow guide unit 4, the water flow can be sheared and guided, and the sheared and guided water flow has stable flow rate and flow direction, which can control the surrounding erosion pit to be more flat and avoid the accumulation of sediment at the rear end.

[0049] In a second aspect, the embodiment of the present application also provides a bridge support structure, and the bridge support structure includes the above-mentioned double-column stepped caisson, Figure 5A bridge support structure structure schematic diagram provided by the embodiment of the application is shown in FIG. 5. The top of the double-column stepped caisson upper step 2 is provided with a bridge tower 7 for supporting the bridge, i.e., the bridge tower 7 is two, respectively connected to the top of the top bearing platform 6 of the two protruding column bodies 201. The bridge tower 7 is mainly used for supporting the bridge deck structure and is responsible for transmitting these loads to the foundation. They disperse the load to the ground through a solid foundation structure, ensuring the stability and safety of the bridge. In combination with the above description, the double-column stepped caisson of the above is arranged in the transverse direction of the bridge, and the two bridge towers 7 are respectively supported on the two sides of the wide side of the bridge.

[0050] In the description of the present application, it should be noted that the terms "upper", "lower", etc. indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. Unless otherwise expressly specified and limited, the terms "mounting", "connection", "connection" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the communication inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0051] It should be noted that in the present application, relational terms such as "first" and "second", etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. Moreover, the terms "include", "contain" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the sentence "including a…" does not exclude the presence of other identical elements in the process, method, article or equipment including the element.

[0052] The above is only a specific embodiment of the present application, which enables those skilled in the art to understand or implement the present application. Various modifications of these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features applied herein.

Claims

1. A double-column stepped caisson suitable for long-span bridges, characterized in that, include: A step assembly for arrangement in the direction of water flow includes a lower step (1) of a caisson with several axially penetrating well holes, and a double-column upper step (2) extending upward from the top surface of the lower step (1) and having an internally hollow structure that communicates with the well holes of the lower step (1). The double-column upper step (2) includes two protruding columns (201) spaced apart along the length direction of the lower step (1). The scour reduction assembly includes a first flow guiding unit (3) provided on the bottom of the outer side of the two protruding columns (201) and a second flow guiding unit (4) located at the bottom between the two protruding columns (201). The first flow guiding unit (3) includes a sharp end for shearing the water flow. The sharp ends of the two first flow guiding units (3) are respectively used to face the water-facing side and the water-repelling side. The second flow guiding unit (4) has concave curved surfaces on both sides for guiding the sheared water flow. The first flow guiding unit (3) includes two flow guiding plates (301) arranged opposite each other, and one side of the two flow guiding plates (301) is separated from each other, while the other side is brought together to form a sharp end. The second flow guiding unit (4) includes two flow diverting plates (401) arranged opposite each other. The flow diverting plates (401) have a certain curvature and the arc surfaces of the two flow diverting plates (401) are close to each other to form a concave curved surface.

2. A double-column stepped caisson suitable for long-span bridges as described in claim 1, characterized in that, The lower step (1) of the caisson is provided with a circular arc end face flow end (101) on both the water-facing side and the back water-facing side.

3. A double-column stepped caisson suitable for long-span bridges as described in claim 2, characterized in that, The bottom of the caisson lower step (1) is provided with a caisson sealing area (5).

4. A double-column stepped caisson suitable for long-span bridges as described in claim 3, characterized in that, The caisson lower step (1) is provided with a step cover plate (102) at the top for sealing the well hole.

5. A double-column stepped caisson suitable for long-span bridges as described in claim 1, characterized in that, The top of the double-column upper step (2) is provided with a top support (6) for connecting the structure above the bridge.

6. A double-column stepped caisson suitable for long-span bridges as described in claim 5, characterized in that, The horizontal cross-sectional area of ​​the bottom of the top support (6) is greater than the horizontal cross-sectional area of ​​the protruding column (201).

7. A bridge support structure, characterized in that, The bridge support structure includes the double-column stepped caisson as described in any one of claims 1 to 6, wherein the top of the double-column stepped caisson is provided with a bridge tower (7) for supporting the bridge.

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