Self-stabilizing steel sheet pile cofferdam structure and construction method

Abstract

A self-stabilizing steel sheet pile cofferdam structure relates to the field of basic equipment for bridge engineering construction. It includes steel sheet piles, inner supports, outer ring beams and connecting parts. Among them, the inner support includes support rods and inner ring beams, the inner ring beams and outer ring beams are respectively supported on the inner and outer surfaces of the steel sheet piles, and the connecting parts are arranged in parallel with the support rods of the uppermost layer. The inner and outer ring beams, support rods and connecting parts of the uppermost layer of the present application form a structural system with the inner ring beams and support rods of other layers to participate in the force, and the connecting parts are prestressed and tensioned, so that the connecting parts will not cause significant damage to the top of the steel sheet piles due to elongation. The present application ensures the overall stability and uplift stability of the steel sheet piles, and can solve the problems of long steel sheet piles and long insertion and extraction time in the cofferdam structure, thereby achieving the purpose of saving construction period and cost, and facilitating construction.

Description

Technical Field

[0001] The present application relates to the field of foundation equipment for bridge engineering construction, and in particular to a self-stabilizing steel sheet pile cofferdam structure and a construction method. Background Art

[0002] A cofferdam is a temporary facility for bridge foundation construction, generally used in the construction of hydraulic structures. Its main function is to serve as a water-isolating device during underwater foundation construction or as a protective support for deep foundation pit excavation, preventing water and soil from entering the construction site of the building so that construction processes such as steel bar binding, formwork installation, and concrete pouring can be carried out under water-free and safe conditions. The cofferdam can also be used as an operating platform for pile foundation construction.

[0003] Steel sheet pile cofferdams are commonly used in underwater foundation construction due to their excellent structural strength, rigidity, and water-stopping properties. Conventional steel sheet pile cofferdams, when used in deep water and in poor geology, require long steel sheet piles, making them difficult to drive and install. Consequently, they are costly, time-consuming, and difficult to operate. Summary of the Invention

[0004] The embodiments of the present application provide a self-stabilizing steel sheet pile cofferdam structure and construction method to solve the problem of long steel sheet piles and long insertion and extraction time in the cofferdam structure, thereby saving construction time and cost and facilitating construction.

[0005] A self-stabilizing steel sheet pile cofferdam structure, comprising:

[0006] There are multiple steel sheet piles, each of which is vertically inserted into the water, and the sides are connected end to end to form a closed enclosure structure;

[0007] There are multiple inner supports distributed from top to bottom inside the enclosed structure; each inner support includes an inner ring beam and multiple horizontally arranged support rods, each inner ring beam abuts against the inner surface of the enclosed structure, and each support rod is connected to the corresponding inner ring beam at both ends;

[0008] an outer ring beam, corresponding to the position of the uppermost inner ring beam and abutting against the outer surface of the enclosed structure;

[0009] The connecting components are at the same height as the support rods of the top layer and are arranged in parallel. The two ends of each connecting component respectively pass through the enclosure structure and pass through the inner ring beam arranged in the enclosure structure. The end of each connecting component passing through the outside of the enclosure structure is locked with the outer ring beam through a locking device, and at least one connecting component is arranged next to each support rod of the top layer.

[0010] Furthermore, the connecting component is a prestressed steel bar or a prestressed steel strand.

[0011] Furthermore, it also includes a plurality of pull rods, which horizontally penetrate the inner ring beam, steel sheet piles and outer ring beam of the top layer, and one end extends out of the outer ring beam and is locked by a locking device, and the other end is fixed to the inner ring beam by a locking device.

[0012] Furthermore, each of the inner ring beam and the outer ring beam is a closed-loop structure, and is respectively supported against the inner surface and outer surface of the enclosed structure.

[0013] Furthermore, the cofferdam structure also includes a plurality of internal diagonal braces, and both ends of each of the internal diagonal braces are fixedly connected to the inner ring beam at the same height.

[0014] Furthermore, the material strength of the support rods in the bottom layer is greater than the material strength of the other support rods.

[0015] The present application also relates to a self-stabilizing steel sheet pile cofferdam construction method, which comprises:

[0016] S1. First, connect the two ends of each support rod to the corresponding inner ring beam, and set up the inner support lowering system on the steel casing;

[0017] S2. Insert steel sheet piles into the water to form an enclosure structure;

[0018] S3, installing the uppermost plurality of support rods and the inner ring beam to the designed elevation, so that the inner ring beam abuts against the inner surface of the enclosed structure;

[0019] S4, outer ring beam is installed on the outer surface of the enclosed structure, and corresponding to the position of the inner ring beam on the uppermost floor, the connecting component is horizontally inserted into the inner ring beam on the uppermost floor, the enclosed structure and the outer ring beam, and at least one connecting component is arranged beside the support rod of each uppermost floor, and a locking device is installed at the end of each described connecting component, and the locking device is positioned at the outer surface of the outer ring beam.

[0020] S5, sequentially removing the underwater soil inside the enclosed structure to the design elevation of the next layer of support rods, and lowering the next layer of inner ring beams and support rods through the inner support lowering system so that the inner ring beams abut against the inner surface of the enclosed structure;

[0021] S6. After all support rods and inner ring beams are installed, remove the inner support lowering system and corbels, and continue to take soil underwater to the designed elevation at the bottom, then pour the bottom sealing concrete. After completion, pump out the water to construct the foundation.

[0022] Furthermore, both step S3 and step S5 further include inserting a spacer block in the gap between the inner ring beam and the enclosing structure.

[0023] Furthermore, the step S4 also includes tensioning the connecting components, where the connecting components are steel bars or steel strands, and prestressed steel bars or prestressed steel strands are obtained after tensioning.

[0024] Furthermore, step S4 also includes inserting multiple pull rods at the upper end of the steel sheet piles, each of the pull rods horizontally passing through the inner ring beam, steel sheet piles and outer ring beam of the top layer, with one end extending out of the outer ring beam and locked by a locking device, and the other end fixed to the inner ring beam by a locking device.

[0025] The beneficial effects of the technical solution provided by this application include:

[0026] The present invention provides a self-stabilizing steel sheet pile cofferdam structure and construction method. The topmost layer's inner and outer ring beams, support rods, and connecting components, along with the inner ring beams and support rods of the other layers, form a structural force-bearing system, significantly enhancing the overall stability and uplift stability of the steel sheet piles. As a result, the actual usable length of the steel sheet piles is less than their theoretical calculated length. This reduction in length simplifies and accelerates their construction, significantly reducing construction time and costs.

[0027] In the embodiment of the present application, the top connecting parts and the inner and outer ring beams are first installed, and the connecting parts are prestressed, so that the connecting parts will not cause damage to the top of the steel sheet pile due to elongation, thereby enhancing the safety and overall stability of the steel sheet pile cofferdam structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0029] Figure 1 This is a schematic diagram of the overall structure of this application.

[0030] Figure 2 for Figure 1 Schematic diagram of the 1 / 4 cross-section of aa, bb, cc, and dd.

[0031] Figure 3 Schematic diagram of the corbel placed on the steel casing for this application.

[0032] Reference numerals:

[0033] 1. Steel sheet piles; 2. Internal support; 21. Inner ring beam; 22. Support rod; 3. Outer ring beam; 4. Locking device; 5. Steel casing; 6. Corbel; 7. Connecting parts; 8. Internal diagonal bracing; 9. Pull rod. DETAILED DESCRIPTION

[0034] To make the purpose, technical solutions, and advantages of the embodiments of this application more clear, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the drawings in the embodiments of this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0035] The embodiment of the present application provides a self-stabilizing steel sheet pile cofferdam structure and construction method, which can solve the problems of long steel sheet piles and long insertion and extraction time in the cofferdam structure, thereby saving construction time and cost and facilitating construction.

[0036] like Figure 1 As shown, a self-stabilizing steel sheet pile cofferdam structure includes a steel sheet pile 1, an inner support 2, an outer ring beam 3, and a connecting component 7.

[0037] There are multiple steel sheet piles 1, each of which is vertically inserted into the water, and the sides are connected end to end to form a closed enclosure structure, which can be a rectangular frame or a circular frame.

[0038] There are multiple inner supports 2, which are distributed from top to bottom inside the enclosure structure. Each inner support 2 includes an inner ring beam 21 and multiple horizontally arranged support rods 22. Each inner ring beam 21 abuts against the inner surface of the enclosure structure, and each support rod 22 is connected to the corresponding inner ring beam 21 at both ends. If the enclosure structure is a rectangular frame, the support rods 22 are arranged parallel to the short sides of the enclosure structure.

[0039] The outer ring beam 3 corresponds to the position of the inner ring beam 21 of the uppermost layer and is supported on the outer surface of the enclosed structure. There is a layer of steel sheet pile 1 between the outer ring beam 3 and the inner ring beam 21 of the uppermost layer, and the outer ring beam 3 and the inner ring beam 21 of the uppermost layer are at the same height.

[0040] The connecting component 7 is at the same height as the topmost support rod 22 and is arranged in parallel. The two ends of each connecting component 7 respectively pass through the enclosed structure and pass through the inner ring beam 21 arranged in the enclosed structure. The end of each connecting component 7 passing through the outside of the enclosed structure is locked with the outer ring beam 3 through the locking device 4. At least one connecting component 7 is arranged next to each topmost support rod 22. The specific number of connecting components 7 next to each support rod 22 can be set according to actual calculation needs.

[0041] Specifically, when the connecting component 7 is a steel bar, the locking device 4 is anchored by a locking nut; when the connecting component 7 is a steel strand, the locking device 4 is anchored by a clip.

[0042] Further, such as Figure 2 Shown, in the present embodiment, each inner ring beam 21 and outer ring beam 3 are closed loop structures, and are respectively supported on the inner surface and the outer surface of the enclosed structure.In other embodiments, if the minor side is less than 10 meters and the aspect ratio is greater than 5 o'clock, then inner ring beam 21 and outer ring beam 3 can not be set to closed loop structure, and support rod 22 is parallel to the minor side of the enclosed structure, so inner ring beam 21 only needs to be arranged along the long side of the enclosed structure and can meet the requirements.

[0043] Further, such as Figure 2 As shown, if the inner ring beam 21 is a closed-loop structure, an internal diagonal brace 8 is further provided. The number of the internal diagonal braces 8 is multiple, the internal diagonal braces 8 are horizontally arranged, and the two ends are respectively fixedly connected to the adjacent edges of the inner ring beam 21 at the same height. The internal diagonal braces 8 strengthen the inner ring beam 21.

[0044] Furthermore, the material strength of the support rods 22 in the lowest layer is greater than that of the other support rods 22. When the steel sheet piles 1 rotate around the support rods 22 in the lowest layer, the support rods 22 in the lowest layer are subjected to greater pressure than the support rods 22 in the other layers above. Therefore, strengthening the support rods 22 in the lowest layer can prevent them from being easily damaged, thus preventing the steel sheet piles 1 from rotating to a certain extent and enhancing the overall stability and uplift stability of the steel sheet pile cofferdam structure.

[0045] Further, such as Figure 1 As shown, stiffening ribs are provided at the connection between the support rod 22 and the corresponding inner ring beam 21. The stiffening ribs can be a plate-like structure. One part of the stiffening ribs is connected to the end of the support rod 22, and the other part is connected to the inner ring beam 21. The stiffening ribs play a role in reinforcing and stabilizing the connection between the support rod 22 and the inner ring beam 21.

[0046] Specifically, the multiple support rods 22 of each layer are horizontal and evenly distributed, which can ensure that each support rod 22 is evenly stressed and ensure the stability of the cofferdam structure.

[0047] Furthermore, the steel sheet piles 1 are Larsen VI type steel sheet piles with lock buckles on both sides, and butter is provided in the lock buckles to ensure that the connection between each steel sheet pile 1 is tighter and firmer.

[0048] Furthermore, the connecting member 7 is a prestressed steel bar or prestressed steel strand. Compared to ordinary steel bars or steel strands, prestressed steel bars or steel strands have higher strength and better crack resistance. When the steel sheet pile 1 rotates around the lowest support rod 22, the prestressed steel bar or prestressed steel strand is stretched, preventing the top of the steel sheet pile 1 from being damaged due to elongation, thereby enhancing the safety and overall stability of the steel sheet pile cofferdam structure.

[0049] Furthermore, spacers are inserted into the gaps between the inner ring beam 21 and the enclosed structure of each layer to make the inner ring beam 21 and the steel sheet pile 1 more tightly connected and better participate in the load as a whole. The spacers can be wedge-shaped steel plates or wooden wedges.

[0050] Furthermore, this embodiment also includes a pull rod 9, and the number of the pull rods 9 is multiple. The pull rod 9 horizontally passes through the inner ring beam 21, steel sheet pile 1 and outer ring beam 3 of the top layer, and one end extends out of the outer ring beam 3 and is locked by the locking device 4, and the other end is fixed to the inner ring beam 21 by the locking device 4, so as to prevent the inner ring beam 21 and the outer ring beam 3 from being separated from the pull rod 9 during the operation of the steel sheet pile cofferdam.

[0051] Specifically, the tie rod 9 is a common steel bar or a prestressed steel bar, which is arranged parallel to the connecting member 7. The tie rod 9 connects the inner ring beam 21, the outer ring beam 3 and the steel sheet pile 1 into a more solid whole, so that the inner ring beam 21 and the outer ring beam 3 can better participate in the force, thereby enhancing the overall stability of the steel sheet pile cofferdam structure.

[0052] This embodiment also provides a self-stabilizing steel sheet pile cofferdam construction method, which includes the following steps:

[0053] The first step is to connect the two ends of each support rod 22 with the corresponding inner ring beam 21, and then set the inner support lowering system on the steel casing 5 and place it on the bracket 6 of the side wall of the steel casing 5, as shown in the figure. Figure 3 In the figure, A represents the water surface elevation and B represents the riverbed elevation.

[0054] The second step is to drive the steel sheet piles 1 into the water to form an enclosure structure. When driving the steel sheet piles 1, the support rods 2 and the inner ring beam 21 resting on the corbels 6 can be used as guides to prevent the steel sheet piles 1 from being tilted or too wide or too narrow.

[0055] The third step is to install the topmost support rods 22 and the inner ring beam 21 to the designed elevation so that the inner ring beam 21 abuts against the inner surface of the enclosed structure.

[0056] The fourth step is to install the outer ring beam 3 on the outer surface of the enclosed structure, and corresponding to the position of the inner ring beam 22 of the uppermost layer, the connecting component 7 is horizontally inserted into the inner ring beam 21, the enclosed structure and the outer ring beam 3 of the uppermost layer, and at least one connecting component 7 is set next to each support rod 22 of the uppermost layer, and a locking device 4 is installed at the end of each connecting component 7, and the locking device 4 is located on the outer surface of the outer ring beam 3.

[0057] Step 5: Remove the underwater soil inside the enclosed structure in sequence to the designed elevation of the next layer of support rods 22, and lower the next layer of inner ring beams 21 and support rods 22 through the inner support lowering system so that the inner ring beams 21 are against the inner surface of the enclosed structure.

[0058] Step 6: After all support rods 22 and inner ring beam 21 are installed, remove the inner support lowering system and bracket 6, and continue to take soil underwater to the designed elevation of the bottom, then pour the bottom sealing concrete, and after completion, pump out the water to construct the foundation.

[0059] Furthermore, in the above-mentioned third step, if the inner ring beam 21 is a closed-loop structure, an internal diagonal brace 8 can also be provided. The number of the internal diagonal braces 8 can be multiple, and the two ends of each internal diagonal brace 8 are respectively welded to the inner ring beam 21 of the same height. The internal diagonal brace 8 strengthens the inner ring beam 21.

[0060] Furthermore, the third step in the above construction method also includes welding the two ends of each internal diagonal brace 8 to the inner ring beam 21 at the same height.

[0061] Furthermore, the fourth step in the above construction method also includes that the connecting component 7 is a steel bar or a steel strand, and the connecting component 7 is tensioned, and the tensioning obtains prestressed steel bars or prestressed steel strands, which have higher strength and better crack resistance.

[0062] Furthermore, the fourth step in the above construction method also includes inserting multiple pull rods 9 at the upper end of the steel sheet pile 1, each pull rod 9 horizontally passing through the inner ring beam 21, steel sheet pile 1 and outer ring beam 3 of the top layer, and one end extends out of the outside of the outer ring beam 3 and is locked by the locking device 4, and the other end extends out of the inner ring beam 2 inside the enclosed structure and is locked by the locking device 4.

[0063] Specifically, the tie rod 9 is an ordinary steel bar or a prestressed steel bar, and the tie rod 9 connects the inner ring beam 21, the outer ring beam 3 and the steel sheet pile 1 into a more solid whole, so that the inner ring beam 21 and the outer ring beam 3 can better participate in the force, thereby enhancing the overall stability of the steel sheet pile cofferdam structure.

[0064] This application does not directly calculate the length of the steel sheet pile 1 according to the standard formula, but improves the structure and construction method of the steel sheet pile cofferdam. According to multiple test verifications and calculation verifications, the steel sheet pile 1 can achieve no embedment depth or a small embedment depth, and the actual pile length of the steel sheet pile 1 can be reduced to 1 / 2 of the theoretical pile length calculated by the standard.

[0065] This application also provides a calculation and analysis process based on the above-mentioned self-stabilizing steel sheet pile structure and construction method, in conjunction with an engineering example. The calculation and analysis process includes two steps: the first step is to calculate the theoretical pile length using conventional calculation methods. The second step is to verify the safety and reliability of the steel sheet pile 1 after the pile length is reduced. The calculation and analysis process is as follows:

[0066] 1. Calculate the theoretical pile length according to conventional calculation methods

[0067] Project Overview: The Class A caps for a submerged approach bridge project, including piers 2# through 10#, measure 26.41×10.25×4m and are constructed using steel sheet pile cofferdams. Pier 2# has the lowest and most unfavorable top elevation. Two layers of internal supports were installed. The first layer's inner ring beam 21 utilizes 2I45b and support rods 22 utilize φ426×6; the second layer's inner ring beam 21 utilizes 2I56b and support rods 22 utilize φ630×8.

[0068] (1) Material parameters and geological parameters

[0069] Q235B strength design value, shear strength f v =120Mpa, Q235 should use E43 type welding rod manual welding fillet weld strength design value Q295bz tensile, compressive and bending resistance f=265MPa.

[0070] Geological parameters: internal friction angle 3.9°, bulk density 15.5kN / m3, cohesion 2.8kPa.

[0071] (2) Calculate load

[0072] A. Earth pressure

[0073] Active earth pressure coefficient

[0074] Passive earth pressure coefficient

[0075] When calculating water pressure and soil pressure, water and soil are calculated separately.

[0076] B. Water pressure

[0077] It is divided into three design conditions:

[0078] Working condition 1: Install the first layer of internal support 2, keep the water head inside and outside the cofferdam consistent, and excavate to 50 cm below the elevation of the second layer of internal support 2 (the second layer of internal support 2 is not installed).

[0079] Working condition 2: Install two layers of internal support 2 and continue excavating to the design elevation of the bottom of the foundation pit (bottom elevation of the bottom concrete).

[0080] Working condition three: After the bottom seal concrete reaches the required strength, pump out the water and remove the second layer of internal support 2 to prepare for the foundation construction.

[0081] (3) Confirmation of the length of steel sheet pile 1

[0082] A. Working condition 1

[0083] x can be obtained based on the equality of the moment of P0 and the passive earth pressure in front of the wall on the bottom end of the steel sheet pile 1, that is,

[0084]

[0085]

[0086] The minimum embedment depth of the steel sheet pile 1 is t0 = x + y = 5.2 + 1.1 = 6.1 m.

[0087] The actual burial depth is t=1.1×t0=6.93m.

[0088] The minimum pile length of the steel sheet pile 1 is 4.5+6.93=11.43m.

[0089] B. Working Condition 2

[0090] x can be obtained based on the equality of the moment of P0 and the passive earth pressure in front of the wall on the bottom end of the steel sheet pile 1, that is:

[0091]

[0092]

[0093] The minimum embedment depth of the steel sheet pile 1 is t0 = x + y = 17.2 + 3 = 20.2 m.

[0094] The actual burial depth is t=1.1×t0=22.22m.

[0095] The minimum pile length of the steel sheet pile 1 is 9.5+22.22=31.72m.

[0096] In view of the above two working conditions, the pile length of steel sheet pile 1 is selected to be 33m.

[0097] 2. Verify the safety and reliability of the reduced length of the steel sheet pile 1 of this application

[0098] Project Overview: The Class A caps of the underwater approach bridge of a certain project include piers 2# to 10# with a size of 26.41×10.25×4m. They are constructed using steel sheet pile cofferdams. The length of the steel sheet pile 1 is 15m. Two layers of inner supports 2 are set. The first layer's inner ring beam 21 adopts 2I45b, and the support rod 22 adopts φ426×6; the outer ring beam 3 adopts 2I45b, and the connecting component 7 adopts two φ32 precision-rolled threaded steel bars for tensioning; the second layer's inner ring beam 21 adopts 2I56b, and the support rod 22 adopts φ630×8.

[0099] (1) Material parameters and geological parameters

[0100] The steel sheet pile 1 is Larsen VI, with a length of 15m; two layers of internal supports 2 are set, and the spacing between the internal supports 2 is 5.0m.

[0101] Q235B steel strength design value: tensile, compressive and bending f = 215MPa (δ ≤ 16), f = 205MPa (16 < δ ≤ 40), shear f v=125MPa(δ≤16), f v =120MPa(16<δ≤40)

[0102] Q295bz steel strength design value: tensile, compressive and bending f = 265MPa,

[0103] E43 type welding rod manual welding fillet weld strength design values: tensile, compressive and shear

[0104] Geological parameters: internal friction angle 3.9°, bulk density 15.5kN / m3, cohesion 2.8kPa.

[0105] (2) Load calculation

[0106] A. Load Combinations

[0107] Ultimate limit state

[0108] In structural design, when expressed in the form of internal forces, the following ultimate limit state design expressions for structural components should be used:

[0109] γ0S≤R

[0110] R=R(f c ,f s ,…) / γ Rd

[0111] In this application, water and soil pressures are calculated based on the Technical Specifications for Construction Foundation Pit Support.

[0112] B. Water pressure

[0113] Calculation of water pressure in static groundwater:

[0114] u a =γ w h wa

[0115] u p =γ w h wp

[0116] C. Earth pressure

[0117] In this application, the soil layer below the groundwater level is calculated using the water-soil separation method. Because the soil layer is in water, it is considered according to the soil's buoyant density. The soil layer above the groundwater level is calculated using the water-soil combined method and is considered according to the soil's natural density.

[0118] The calculation formula is as follows:

[0119]

[0120]

[0121] (3) Calculation and analysis of steel sheet pile cofferdam structure

[0122] A. Calculation of reaction force of connection component 7 and verification of steel sheet pile 1

[0123] Working condition 1: After the riverbed is excavated to a depth of 2.5m, steel sheet piles 1 are driven and two layers of inner supports 2 are installed in sequence. The riverbed is then excavated further to a bottom elevation of -7.0m. During the excavation process, the difference in water head between the inside and outside is kept consistent in preparation for underwater bottom sealing.

[0124] According to the Technical Code for Construction Foundation Pit Support, when the soil below the pit bottom is soft soil, the embedment depth of the support retaining structure should meet the following requirements for arc sliding stability with the lowest inner support 2 as the axis.

[0125]

[0126] The anti-overturning moment generated by the tensile reaction force and the passive earth pressure of the uppermost inner ring beam 21 and the outer ring beam 3 resists the overturning moment of the active earth pressure.

[0127] Take the steel sheet pile with unit width of 1m for calculation. Since the internal and external water are balanced, the water pressure is not considered.

[0128] Active earth pressure

[0129] Active earth pressure resultant

[0130] Overturning moment

[0131] Passive earth pressure

[0132] Passive earth pressure resultant

[0133] Assume that the unit width is 1m and the required pulling force is N

[0134]

[0135] N=121KN.

[0136] The above calculations show that to ensure the overall stability of the steel sheet pile, the top inner ring beam 21 and outer ring beam 3 must withstand a tensile force of 157 kN per 1 meter. The lower portion of steel sheet pile 1 is a cantilever structure. Calculations using MIDAS software show that the maximum bending moment of steel sheet pile 1 is 599.5 kN·m, and the stress is 222 MPa < 265 MPa, meeting the requirements.

[0137] Working Condition 2: After the bottom concrete reaches full strength, water is pumped out. A point 0.5 m below the top surface of the bottom concrete is selected as the support point. The second layer of internal support 2 is removed, and the stress of steel sheet pile 1 is verified. At this point, steel sheet pile 1 is subject to external water pressure and active earth pressure.

[0138] q 水 =γ 水 h 水 =10×8.1=81KN / m 2

[0139]

[0140] The calculation results of MIDAS software show that the maximum bending moment of steel sheet pile 1 is 540.2kN.m and the stress is 265MPa, which meets the requirements.

[0141] (2) Verification of outer ring beam 3 and inner support 2

[0142] A. Verification of the inner ring beam 21 of the first layer (top layer)

[0143] The calculation results of midas software show that the inner ring beam 21 of the first layer (top layer) adopts 2I45b, the support adopts φ426×6, the material is Q235B, the maximum force is 113.6KN / m, and the maximum stress σ=185.2MPa<σ=215Mpa, which meets the requirements.

[0144] B. Verification of support rod 22

[0145] The calculation results of MIDAS software show that the most unfavorable maximum axial force of the steel pipe is 863.9KN, the bending stress under deadweight is 22MPa, and the length of the steel pipe is 14.4m. The cross-sectional characteristics are:

[0146] A=7916mm 2 , i=148.5, l=14400mm, λ=97

[0147] The stability coefficient can be obtained by looking up the table: φ = 0.67.

[0148] The calculated stable stress is:

[0149] C. Verification of the second-story inner ring beam 21

[0150] The second-layer inner ring beam 21 adopts 2I56b, the support adopts φ630×8, the material is Q235B, the maximum force is 173.4KN / m, the maximum stress σ=183.6MPa<σ=215Mpa, which meets the requirements.

[0151] D. Steel pipe stability verification

[0152] The most unfavorable maximum axial force of the steel pipe is 1314.3KN, the self-weight bending stress is 15.8MPa, and the length of the steel pipe is 14.4m.

[0153] The cross-sectional properties are:

[0154] A=15632mm 2 , i=219.9, l=14400mm, λ=66

[0155] The stability coefficient can be obtained by looking up the table: φ = 0.77.

[0156] The calculated stable stress is:

[0157]

[0158] E. Calculation of outer ring beam 3

[0159] The outer ring beam 3 is made of 2I45b, with two φ32 fine-rolled threaded steel bars (PSB930 grade) tensioned. The spacing is 4.8m based on the size of steel sheet pile 1. A 1m width requires a tensile force of 156KN. Each φ32 fine-rolled threaded steel bar can withstand the following tensile force:

[0160]

[0161] Meet the requirements.

[0162] The maximum stress σ=148.2MPa<σ=215Mpa, which meets the requirements.

[0163] In summary, calculations show that the actual length of the steel sheet piles 1 in the steel sheet pile cofferdam is 15 meters, which is half the theoretical length calculated using the standard formula, and both strength and stiffness meet the requirements. Therefore, the self-stabilizing steel sheet pile cofferdam structure and construction method of the present application can achieve the goal of reducing the length of the steel sheet piles 1, making the construction of the steel sheet piles 1 simple and quick, significantly saving construction time and costs, and ensuring the safety and overall stability of the steel sheet pile cofferdam structure.

[0164] In the description of this application, it should be noted that the terms "upper" and "lower" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on this application. Unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be internal communication between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0165] It should be noted that, in this application, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0166] The foregoing is merely a list of specific embodiments of the present application, intended to enable those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application is not limited to the embodiments shown herein, but is intended to conform to the broadest scope consistent with the principles and novel features of the present application.

Claims

1. A construction method for a self-stabilizing steel sheet pile cofferdam structure, characterized by: The self-stabilizing steel sheet pile cofferdam structure comprises: There are multiple steel sheet piles (1), each of which is vertically inserted into the water, and the sides are connected end to end to form a closed enclosure structure; There are multiple inner supports (2) distributed from top to bottom inside the enclosure structure; each inner support (2) comprises an inner ring beam (21) and multiple horizontally arranged support rods (22); each inner ring beam (21) is supported on the inner surface of the enclosure structure, and both ends of each support rod (22) are connected to the corresponding inner ring beam (21); An outer ring beam (3) corresponds to the position of the uppermost inner ring beam (21) and abuts against the outer surface of the enclosed structure; The connecting component (7) is at the same height as the support rod (22) of the uppermost layer and is arranged in parallel. The two ends of each connecting component (7) respectively pass through the enclosed structure and pass through the inner ring beam (21) arranged in the enclosed structure. The end of each connecting component (7) passing through the outer ring beam (3) is locked by a locking device (4), and at least one connecting component (7) is arranged next to each support rod (22) of the uppermost layer. The construction method comprises the following steps: S1, first connect the two ends of each support rod (22) to the corresponding inner ring beam (21), and place them on the bracket (6) of the side wall of the steel casing (5), and set the internal support lowering system on the steel casing (5); S2, inserting steel sheet piles (1) into the water to form an enclosure structure; S3, installing the uppermost plurality of support rods (22) and the inner ring beam (21) to the designed elevation, so that the inner ring beam (21) abuts against the inner surface of the enclosed structure; S4, an outer ring beam (3) is installed on the outer surface of the enclosed structure, and the position of the inner ring beam (21) of the uppermost layer is corresponding, a connecting member (7) is horizontally inserted into the inner ring beam (21) of the uppermost layer, the enclosed structure and the outer ring beam (3), and at least one connecting member (7) is provided beside each support rod (22) of the uppermost layer, and the connecting member (7) is prestressed, and a locking device (4) is installed at the end of each of the connecting members (7), and the locking device (4) is located at the outer surface of the outer ring beam (3); S5, sequentially taking out the underwater soil inside the enclosed structure to the design elevation of the next layer of support rods (22), lowering the next layer of inner ring beams (21) and support rods (22) through the inner support lowering system, so that the inner ring beams (21) are supported on the inner surface of the enclosed structure; S6. After all support rods (22) and inner ring beams (21) are installed, the inner support lowering system and the bracket (6) are removed, and soil is taken underwater to the designed elevation of the bottom, and then the bottom sealing concrete is poured. After completion, water is pumped out to construct the foundation.

2. The construction method of the self-stabilizing steel sheet pile cofferdam structure according to claim 1, characterized in that: Each of the inner ring beam (21) and the outer ring beam (3) is a closed-loop structure and is respectively supported against the inner surface and the outer surface of the enclosed structure.

3. The construction method of the self-stabilizing steel sheet pile cofferdam structure according to claim 1, characterized in that: The material strength of the support rod (22) at the bottom layer is greater than the material strength of the other support rods (22).

4. The construction method of the self-stabilizing steel sheet pile cofferdam structure according to claim 1, wherein: The cofferdam structure comprises a plurality of internal diagonal braces (8), and both ends of each internal diagonal brace (8) are respectively fixedly connected to an inner ring beam (21) at the same height; The step S3 further comprises welding the two ends of each internal diagonal brace (8) to the inner ring beam (21) at the same height.

5. The construction method of the self-stabilizing steel sheet pile cofferdam structure according to claim 1, characterized in that: The step S4 also includes: the connecting component (7) is a steel bar or a steel strand, and the connecting component (7) is tensioned to obtain a prestressed steel bar or a prestressed steel strand.

6. The construction method of the self-stabilizing steel sheet pile cofferdam structure according to claim 1, characterized in that: It also includes a plurality of pull rods (9), wherein the pull rods (9) horizontally penetrate the inner ring beam (21), the steel sheet piles (1) and the outer ring beam (3) of the uppermost layer, and one end of the pull rods (9) extends out of the outer ring beam (3) and is locked by a locking device (4), and the other end is fixed to the inner ring beam (21) by the locking device (4); The step S4 also includes horizontally passing multiple tie rods (9) through the inner ring beam (21), steel sheet piles (1) and outer ring beam (3) of the top layer, with one end of the tie rod (9) extending out of the outer ring beam (3), and then locking the tie rod (9) through a locking device (4), and the other end is also fixed by the locking device (4).

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