Construction technical method for shallow covering layer double-layer steel sheet pile cofferdam of complex sea area

Abstract

The invention relates to a construction technical method of a shallow covering layer double-layer steel sheet pile cofferdam in a complex sea area, and belongs to the technical field of cofferdam construction, the construction technical method comprises the following steps: 1, lengthening an inner side steel sheet pile and an outer side steel sheet pile, and inserting and driving the inner side steel sheet pile and the outer side steel sheet pile; secondly, the inner side ring beam structural part is transported to the site and is in butt joint, a support is welded to the inner side ring beam installation position, and the inner side ring beam is hoisted to the support and fixed; thirdly, the inner supporting structural part is transported to the site and installed; fourthly, a pouring platform is erected, inter-plate concrete is poured between the two layers of steel sheet piles through a guide pipe method, and meanwhile a seabed in the cofferdam is leveled; 5, installing a middle ring beam and an outer ring beam; and sixthly, bottom sealing construction is conducted.

Description

Technical Field

[0001] This invention belongs to the field of cofferdam construction technology, specifically relating to a construction technique for a shallow overburden double-layer steel sheet pile cofferdam in complex sea areas. Background Technology

[0002] With the continuous development of science and technology and economy in my country, the construction of long-span bridges has made remarkable progress. Bridge construction requires the setting of cofferdams to construct piers. However, cofferdam construction, especially in complex marine environments, faces problems such as deep water, strong winds, rapid waves, high current speeds, or bare rock geology.

[0003] Existing cofferdam construction methods typically include, for example, a double-layer steel sheet pile cofferdam disclosed in Chinese Patent CN115075270B. This cofferdam structure comprises several double-layer U-shaped steel plates and several double-layer curved steel plates connected together. A connecting plate is used to connect the double-layer U-shaped steel plates, and each double-layer U-shaped steel plate has a locking joint on both sides. Similarly, a connecting plate is used to connect the double-layer curved steel plates, and each double-layer curved steel plate has a locking joint on both sides. The interlocking of the two locking joints on the front and rear of the double-layer U-shaped steel plates with the locking joints on the front and rear of another double-layer U-shaped steel plate creates a tighter seal between the sheet piles. The resulting enclosure groove can be filled with absorbent sponge or sand, significantly improving the waterproofing effect. Positioning bolts on the connecting plate pass through threaded holes on the connecting plate and are threaded into positioning bolt holes on the upper part of another double-layer U-shaped steel plate, thus making the connection between the sheet piles more stable and robust. However, in complex marine environments, simply setting up double-layer steel sheets may not be enough to withstand complex environmental factors. For example, in a certain sea area, the impact of water flow in some directions is greater, causing it to exceed the design bearing capacity of the local cofferdam. If every part of the cofferdam is reinforced, the cost or construction period will exceed expectations. Therefore, a construction technology method for shallow overburden double-layer steel sheet pile cofferdams in complex sea areas with strong adaptability to water areas and high structural strength is needed. Summary of the Invention

[0004] To address the aforementioned problems in the existing technology, this invention provides a construction technology method for a shallow overburden double-layer steel sheet pile cofferdam in complex sea areas, which features strong adaptability to water conditions and high structural strength.

[0005] The objective of this invention can be achieved through the following technical solutions: A construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex marine areas includes the following steps: Step 1: Extend the inner and outer sheet piles, drive the inner and outer sheet piles, measure the water flow velocity and direction around the cofferdam area, draw a flow field diagram, find the main flow direction, and find the location where the maximum flow velocity occurs in the main flow direction. Divide the cofferdam into several sections, and mark the section closest to the location where the maximum flow velocity occurs as the danger section. Step 2: Transport the inner ring beam structural components to the site, connect them, weld the brackets at the inner ring beam installation positions, hoist the inner ring beam onto the brackets and fix it in place; Step 3: Transport the internal support structure to the site and install it; Step 4: Construct a pouring platform and pour inter-slab concrete between the two layers of sheet piles using the tremie method. Simultaneously, level the seabed inside the cofferdam. For critical sections, embed shear reinforcement mesh in advance during inter-slab concrete pouring. Step 5: Install the intermediate ring beam and outer ring beam; Step Six: Perform bottom sealing construction.

[0006] As a preferred technical solution of the present invention, step one further includes: measuring the water flow velocity and direction around the cofferdam area, drawing a flow field diagram, finding the main flow direction, and finding the location where the maximum flow velocity occurs in the main flow direction, dividing the cofferdam into several sections, and marking the section closest to the location where the maximum flow velocity occurs as the danger section; step four further includes: embedding shear-resistant steel mesh in advance when pouring concrete in the danger section.

[0007] As a preferred embodiment of the present invention, step one further includes: determining whether the flow velocity value of the maximum flow velocity exceeds the flow velocity threshold; step four further includes: when the determination result is yes, increasing the density of the shear reinforcement mesh.

[0008] As a preferred embodiment of the present invention, step one further includes: measuring the flow velocity value L of the maximum flow velocity; step four further includes: adjusting the density of the shear reinforcement mesh to M, where M=L / L0×M0, M0 is a pre-input density reference value, and L0 is a pre-input flow velocity threshold.

[0009] As a preferred embodiment of the present invention, step one further includes: finding the frequency at which the maximum flow velocity occurs and determining whether the frequency exceeds a threshold; step four further includes: when the determination result is yes, further adjusting the density of the shear reinforcement mesh upward.

[0010] As a preferred embodiment of the present invention, step one further includes: measuring the frequency P of the occurrence of the maximum flow velocity; step four further includes: adjusting the density of the shear reinforcement mesh to M×A1, where A1=P / P0×d, d is a pre-input constant, and P0 is a pre-input frequency threshold.

[0011] As a preferred embodiment of the present invention, step four further includes: pouring C30 concrete between the two layers of steel sheet piles; step six further includes: using C35 concrete.

[0012] As a preferred embodiment of the present invention, step five further includes: the outer ring beam is made of HN500×400 steel.

[0013] The beneficial effects of this invention are as follows: (1) By using double-layer steel sheet piles and pouring concrete in the middle of the double-layer steel sheet piles to form a composite structure, the overall structural strength and overturning stability are improved without adding extra steel structure, while avoiding the cost or construction period exceeding expectations due to the additional reinforcement of each part of the cofferdam. (2) By measuring the water flow velocity and direction around the cofferdam area, the cofferdam is divided into several sections. The section closest to the location where the maximum flow velocity occurs is marked as the dangerous section. When pouring concrete in the dangerous section, shear-resistant steel mesh is embedded in advance. In a certain sea area, the water flow impact force in some directions is relatively large, which may lead to exceeding the design bearing capacity of the local cofferdam. The cofferdam is strengthened in a targeted manner, which improves the structural strength and water adaptability. At the same time, it is not necessary to strengthen every part of the cofferdam. Compared with the scheme of additionally reinforcing every part of the cofferdam, the cost or construction period is reduced. (3) By increasing the density of the shear reinforcement mesh when the maximum flow velocity exceeds the flow velocity threshold, the cofferdam is further strengthened in a targeted manner, thereby improving the structural strength and water adaptability; (4) By further increasing the density of the shear reinforcement mesh when the frequency of the maximum flow velocity exceeds the frequency threshold, the cofferdam is further strengthened in a targeted manner, thereby improving the structural strength and water adaptability. Attached Figure Description

[0014] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0015] Figure 1 This is a cross-sectional schematic diagram of the present invention; Figure 2 This is a schematic diagram of the inner steel sheet pile driving of the present invention; In the diagram: 1. Inner sheet pile; 2. Outer sheet pile; 21. Temporary guide; 3. Inner ring beam; 4. Internal support; 5. Concrete between slabs; 6. Intermediate ring beam; 7. Seabed inside the cofferdam; 8. Bottom sealing concrete; 9. Pier cap. Detailed Implementation

[0016] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided.

[0017] Please see Figure 1-2 A construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex marine areas includes the following steps: Step 1: Extend the inner sheet pile 1 and the outer sheet pile 2, and drive the inner sheet pile 1 and the outer sheet pile 2 into the ground. Step 2: Transport the inner ring beam 3 structural component to the site, connect it, weld the bracket at the installation position of the inner ring beam 3, hoist the inner ring beam 3 onto the bracket and fix it. Step 3: Transport the four internal support structural components to the site and install them; Step 4: Construct a pouring platform and pour concrete between the two layers of sheet piles using the tremie pipe method. Simultaneously, level the seabed 7 within the cofferdam. Step 5: Install the intermediate ring beam 6 and the outer ring beam; Step Six: Perform bottom sealing construction; Specifically, in step one, when splicing sheet piles, it is necessary to ensure that the sheet piles are of equal width, the interlocks are straight and parallel, and there is no twisting. At the same time, the inner sheet pile 1 and the outer sheet pile 2 are driven from two directions using a special sheet pile driving machine, a 100t crawler crane and an ICE 36RF vibratory hammer, with the joints of adjacent sheet piles staggered during driving. Before driving the outer sheet pile 2, a temporary guide 21 is installed using the inner sheet pile 1 of the inner layer to ensure the driving accuracy of the sheet piles. Specifically, the outer sheet pile driving uses the platform pipe pile and the inner sheet pile 1 to install the temporary guide 21. The platform pipe pile guide is the same as the guide used for the inner sheet pile. A bracket is welded on the platform pipe pile, and I-beams of 16 are erected on the bracket as temporary sheet piles to control the driving line of the sheet piles. In this embodiment, the allowable deviation of the verticality of the sheet piles is 1.0%. In step two: the inner ring beam 3 is processed into a semi-finished product in the steel structure factory and connected into a whole on the platform. When the tide is low to +0.5m, a triangular bracket is first welded at the steel sheet pile under the installation position of the inner ring beam 3. Then, the inner ring beam 3 is placed on the triangular bracket and adjusted and fixed using a gantry crane. Step 3 specifically includes the following process for the internal support 4 structural components: processing the internal support 4 semi-finished products at the steel structure factory, with the length controlled within 12m, transporting them to the site, assembling them into a whole on the platform, and directly installing them using a gantry crane; In complex marine environments, simply setting up double-layer steel plates may not be enough to withstand complex environmental factors. For example, in a certain sea area, the impact of water flow in some directions is greater, causing it to exceed the design bearing capacity of the local cofferdam. If every part of the cofferdam is reinforced, the cost or construction period will exceed expectations. Therefore, after step three is completed, step four is executed: a pouring platform is erected, and concrete 5 is poured between the two layers of steel sheet piles using the tremie method, while the seabed 7 inside the cofferdam is leveled. Specifically, in step four: C30 concrete is used between the two layers of steel sheet piles. While the concrete is being poured between the two layers of steel sheet piles, a long-arm excavator is used to level the seabed 7 inside the cofferdam. Before leveling, the seabed 7 inside the cofferdam is fully measured. Then, the seabed 7 inside the cofferdam is leveled to reach the specified elevation. If the elevation of the seabed 7 inside the cofferdam is not high enough, sand is used to backfill to the specified elevation. When installing the intermediate ring beam 6 and the outer ring beam in step five, the process is similar to that of installing the inner ring beam 3. Preferably, the outer ring beam is made of HN500×400 steel. In step six, the bottom sealing concrete 8 adopts a dry sealing construction method. After the water is pumped out of the cofferdam, the steel casing and the inner steel sheet pile 1 are cleaned with a high-pressure water gun, and then the bottom sealing concrete 8 is constructed. The bottom sealing concrete 8 uses C35 concrete with a thickness of 2.2m and is poured in one go. By using double-layer steel sheet piles and pouring concrete between the double-layer steel sheet piles to form a composite structure, the overall structural strength and overturning stability are improved without adding extra steel structures, while avoiding the cost or construction period exceeding expectations due to additional reinforcement of every part of the cofferdam.

[0018] Although the above scheme improves the overall structural strength and reduces the construction period by setting up inter-slab concrete 5, in some cases, the ocean currents are quite complex, and there is a probability that high-intensity water flow will continuously scour a part of the cofferdam around it. Therefore, it is necessary to improve this. To this end, step one also includes: measuring the water flow velocity and direction around the cofferdam area, drawing a flow field diagram, finding the main flow direction, and finding the location of the maximum flow velocity in the main flow direction. Divide the cofferdam into several sections, and mark the section closest to the location of the maximum flow velocity as the danger section. Step four also includes: embedding shear reinforcement mesh in advance when pouring concrete in the danger section. Specifically, in step one, an acoustic Doppler current profiler (ADCP) is deployed around the planned cofferdam area. The cofferdam is divided into 10 sections along its own direction. The water flow near the 10 sections is measured continuously for 48 to 72 hours to measure the flow velocity and direction, draw the flow rose diagram, find the main flow direction, the location and frequency of the maximum flow velocity, and mark the section with the closest location of the maximum flow velocity as the danger section. By measuring the water flow velocity and direction around the cofferdam area, the cofferdam is divided into several sections. The section closest to the location of the maximum flow velocity is marked as the danger section. When pouring concrete in the danger section, shear-resistant steel mesh is embedded in advance. In a certain sea area, the water flow impact force in some directions is relatively large, which may cause the local cofferdam to exceed its design bearing capacity. The cofferdam is reinforced in a targeted manner, which improves the structural strength and water adaptability. At the same time, compared with the solution of reinforcing every part of the cofferdam, the cost or construction period is reduced. In some cases, it is necessary to supplement the structural strength of the dangerous section. Therefore, step one also includes: determining whether the flow velocity value of the maximum flow velocity exceeds the flow velocity threshold; step four also includes: increasing the density of the shear reinforcement mesh when the determination result is yes. Specifically, in step one, the flow velocity value L of the maximum flow velocity is measured first; in step four, the density of the shear reinforcement mesh is adjusted to M, where M=L / L0×M0, M0 is the pre-input density reference value, and L0 is the pre-input flow velocity threshold. When the maximum flow velocity L is large, it means that the water flow in the dangerous section is large and the shear reinforcement mesh density needs to be increased. At this time, the value of M=L / L0×M0 is large. When the density of the shear reinforcement mesh is adjusted to M, the local targeted reinforcement for the case of large maximum flow velocity is completed. By increasing the density of the shear reinforcement mesh when the maximum flow velocity exceeds the flow velocity threshold, the cofferdam is further strengthened in a targeted manner, thereby improving the structural strength and water adaptability. Meanwhile, step one also includes: finding the frequency of the maximum flow velocity and determining whether the frequency exceeds the threshold; step four also includes: when the determination result is yes, further adjusting the density of the shear reinforcement mesh upwards; Specifically, in step one, the frequency P of the maximum flow velocity needs to be measured; in step four, the density of the shear reinforcement mesh is adjusted to M×A1, where A1=P / P0×d, d is a pre-input constant, and P0 is a pre-input frequency threshold. When the maximum flow velocity occurs frequently, it means that the water flow in the impact danger zone reaches a large value more often. It is also necessary to increase the density of the shear reinforcement mesh. At this time, the value of A1=P / P0×d is large. When the density of the shear reinforcement mesh is adjusted to M×A1, local targeted reinforcement is completed for the case of large maximum flow velocity. By further increasing the density of the shear reinforcement mesh when the frequency of the maximum flow velocity exceeds the frequency threshold, the cofferdam is further strengthened in a targeted manner, thereby improving the structural strength and water adaptability.

[0019] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas, characterized in that: Includes the following steps: Step 1: Extend the inner and outer sheet piles, drive the inner and outer sheet piles, measure the water flow velocity and direction around the cofferdam area, draw a flow field diagram, find the main flow direction, and find the location where the maximum flow velocity occurs in the main flow direction. Divide the cofferdam into several sections, and mark the section closest to the location where the maximum flow velocity occurs as the danger section. Step 2: Transport the inner ring beam structural components to the site, connect them, weld the brackets at the inner ring beam installation positions, hoist the inner ring beam onto the brackets and fix it in place; Step 3: Transport the internal support structure to the site and install it; Step 4: Construct a pouring platform and pour inter-slab concrete between the two layers of sheet piles using the tremie method. Simultaneously, level the seabed inside the cofferdam. For critical sections, embed shear reinforcement mesh in advance during inter-slab concrete pouring. Step 5: Install the intermediate ring beam and outer ring beam; Step Six: Perform bottom sealing construction.

2. The construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas according to claim 1, characterized in that: Step one further includes: determining whether the flow velocity value of the maximum flow velocity exceeds the flow velocity threshold; Step four further includes: when the determination result is yes, increasing the density of the shear reinforcement mesh.

3. The construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas according to claim 2, characterized in that: Step one further includes: measuring the flow velocity value L of the maximum flow velocity; Step four further includes: adjusting the density of the shear reinforcement mesh to M, where M=L / L0×M0, M0 is a pre-input density reference value, and L0 is a pre-input flow velocity threshold.

4. The construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas according to claim 3, characterized in that: Step one also includes: finding the frequency at which the maximum flow velocity occurs and determining whether the frequency exceeds the threshold; Step four also includes: if the determination result is yes, further adjusting the density of the shear reinforcement mesh upward.

5. The construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas according to claim 4, characterized in that: Step one further includes: measuring the frequency P of the maximum flow velocity; Step four further includes: adjusting the density of the shear reinforcement mesh to M×A1, where A1=P / P0×d, d is a pre-input constant, and P0 is a pre-input frequency threshold.

6. The construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas according to claim 5, characterized in that: Step four also includes: pouring C30 concrete between the two layers of steel sheet piles as inter-slab concrete; Step six also includes: using C35 concrete.

7. The construction technique for a double-layer steel sheet pile cofferdam with shallow overburden in complex sea areas according to claim 1, characterized in that: Step five also includes: the outer ring beam is made of HN500×400 steel.

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