Design method and assembling method of steel hanging box cofferdam side wall suitable for water level sudden change environment and / or multiple work point turnover

Abstract

The invention discloses a design method and an assembly method for a side wall of a steel boxed cofferdam suitable for water level sudden change environments and / or multi-worksite turnover. The design method comprises: dividing the cofferdam side wall into layers for design along the vertical direction of the cofferdam, comprising a high-strength side wall layer and a low-strength side wall layer, wherein the material specification of vertical ribs and / or force transmission rods and / or ring plates for manufacturing the high-strength side wall layer is correspondingly larger than that of vertical ribs and / or force transmission rods and / or ring plates for manufacturing the low-strength side wall layer; the assembly method comprises: the height of the high-strength side wall layer is h1, the height of the low-strength side wall layer is h2, and the water level depth during construction is L; when L < h2, the side wall of the steel boxed cofferdam adopts the low-strength side wall layer; when h2 < L < h1 + h2, the side wall of the steel boxed cofferdam comprises two layers, wherein the lower layer is the high-strength side wall layer and the upper layer is the low-strength side wall layer. By processing the side wall of the steel boxed cofferdam in layers, the invention can adapt to the construction requirements of sudden water level change and achieve the purpose of reasonably controlling the cost.

Description

Technical Field

[0001] This invention relates to the field of steel cofferdam construction technology, and in particular to a design and assembly method for the sidewall of a steel caisson cofferdam suitable for environments with sudden changes in water level and / or multiple work sites. Background Technology

[0002] Construction of underwater foundation piers typically employs the steel cofferdam method to create waterless working conditions. Compared to land-based foundation piers, underwater foundation cofferdam construction is characterized by larger steel consumption and longer construction periods. Steel caissons are suitable for high-pile foundation construction in deep water. A steel caisson cofferdam is a bottomed structure that floats in the water after being lowered to the design elevation. After the bored piles are completed, the bottom is sealed with underwater concrete, and the cofferdam is formed after drainage. The construction of steel caisson cofferdams is affected by various factors such as water level, construction period, and efficiency, significantly increasing the difficulty of balancing construction requirements with cost control.

[0003] For example, the dimensions of a cofferdam are mainly determined by its wall thickness, the size of its foundation, and the net distance between the foundation and the cofferdam. The wall thickness generally depends on the water pressure the cofferdam will experience and the minimum space available for personnel to work. The water pressure is mainly affected by the water level. Therefore, before construction, the height of the steel caisson cofferdam with the foundation in the water needs to be designed based on the design water level. The design water level is usually inferred from historical water levels. However, if the water level changes, such as becoming lower, using the designed steel caisson cofferdam will result in wasted costs. If the water level becomes higher, another layer of steel cofferdam needs to be added, requiring the fabrication of a new layer of steel caisson cofferdam, which will extend the construction period.

[0004] If the construction site has characteristics of large water level fluctuations, or if there is a construction site with multiple underwater foundations, i.e. multiple work points, then in order to meet construction requirements and reasonably control costs, the control of steel volume, site time and space is particularly important. This also shows that the design of steel cofferdam is a prerequisite for whether bridge foundations can achieve green construction, and must be studied in detail. Summary of the Invention

[0005] This invention discloses a design and assembly method for the sidewall of a steel caisson cofferdam suitable for environments with sudden water level changes and / or multiple work sites. The sidewall of the steel caisson cofferdam is processed in layers, which can adapt to the construction requirements of sudden water level changes and achieve the purpose of reasonable cost control.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A design method for the sidewall of a steel caisson cofferdam suitable for environments with sudden water level changes and / or multiple work sites, comprising the following steps: Along the vertical direction of the cofferdam, the cofferdam sidewalls are designed in layers, including a high-strength sidewall layer and a low-strength sidewall layer. The materials used to make the vertical ribs and / or force transmission rods and / or ring plates of the high-strength sidewall layer are larger than those used to make the vertical ribs and / or force transmission rods and / or ring plates of the low-strength sidewall layer.

[0007] Preferably, along the horizontal direction of the cofferdam, the high-strength sidewall layer is designed in segments, including high-strength straight-area sidewall segments and high-strength corner-area sidewall segments. According to the dimensions of the cofferdam sidewall, several high-strength straight-area sidewall segments and several high-strength corner-area sidewall segments are horizontally assembled together to form a layer of cofferdam sidewall; the high-strength straight-area sidewall segments are straight, and the high-strength corner-area sidewall segments are corner-shaped, or one end is flat and the other end is oblique. The segmented design of the low-strength sidewall layer includes low-strength straight-area sidewall segments and low-strength corner-area sidewall segments. According to the dimensions of the cofferdam sidewall, several low-strength straight-area sidewall segments and several low-strength corner-area sidewall segments are horizontally assembled together to form a layer of cofferdam sidewall. The low-strength straight-area sidewall segments are straight, and the low-strength corner-area sidewall segments are corner-shaped, or one end is flat and the other end is oblique.

[0008] More preferably, the length and width of the high-strength straight-line sidewall segment and the low-strength straight-line sidewall segment are equal; the outer edge cross-sectional shape of the high-strength corner sidewall segment and the low-strength corner sidewall segment at the same vertical cofferdam sidewall position is the same.

[0009] Preferably, the vertical ribs of the high-strength sidewall layer are made of materials with a specification of L125mm×125mm×12mm or larger. The high-strength sidewall layer uses [20 channel steel or larger specification material] as the force transmission rod. The ring plate of the high-strength sidewall layer is made of steel plate with a thickness of 16mm or larger. The vertical ribs of the low-strength sidewall layer are made of materials with a specification of L75mm×75mm×5mm or larger. The material specifications used for the force transmission rods of the low-strength sidewall layer are [10 channel steel or larger specifications]. The annular plate of the low-strength sidewall layer is made of steel plate with a thickness of 10mm or larger.

[0010] More preferably, when there are cofferdams of different sizes at the same construction site, the length and width of the plurality of high-strength straight-sidewall sections and the plurality of low-strength straight-sidewall sections are all equal according to the sizes of the cofferdams; the dimensions of the high-strength corner-sidewall sections at different vertical cofferdam sidewall positions are designed based on the principle that the length / width of the cofferdam formed by splicing a plurality of said high-strength straight-sidewall sections and a plurality of said high-strength corner-sidewall sections is at least 0.1m greater than the length / width of the corresponding bearing platform, and the design takes the minimum number of said high-strength corner-sidewall sections with different cross-sectional dimensions required as the optimal solution, wherein said plurality can be 0; the low-strength corner-sidewall sections are designed by referring to the design principle of said high-strength corner-sidewall sections.

[0011] The present invention further provides an assembling method for a steel boxed cofferdam sidewall based on the above design method of a steel boxed cofferdam sidewall suitable for sudden water level change environments and / or turnover among multiple construction sites, wherein the height of the high-strength sidewall layer is h1, the height of the low-strength sidewall layer is h2, and the actual water depth during construction is L; when L < h2 and L < h1, the steel boxed cofferdam sidewall adopts said low-strength sidewall layer or said high-strength sidewall layer; when L < h2 and L > h1, the steel boxed cofferdam sidewall adopts said low-strength sidewall layer; when h2 < L < h1+h2, the steel boxed cofferdam sidewall comprises two layers, wherein the lower layer is said high-strength sidewall layer and the upper layer is said low-strength sidewall layer, and if L simultaneously satisfies L < 2h1, alternatively both layers of the steel boxed cofferdam sidewall can be selected as said high-strength sidewall layer; when L > h1+h2, the steel boxed cofferdam sidewall comprises at least three layers, wherein the lowermost layer is said low-strength sidewall layer and is fully filled with underwater compartment concrete, the penultimate layer is said high-strength sidewall layer, and said low-strength sidewall layer and / or said high-strength sidewall layer are further superimposed upward until the height is greater than the water depth L during construction, or the lowermost layer and the penultimate layer are said low-strength sidewall layers and are fully filled with underwater compartment concrete, and said low-strength sidewall layer and / or said high-strength sidewall layer are further superimposed upward until the height is greater than the water depth L during construction.

[0012] Preferably, when L < h2 and L < h1, the steel boxed cofferdam sidewall adopts said low-strength sidewall layer; when h2 < L < h1+h2, the steel boxed cofferdam sidewall comprises two layers, wherein the lower layer is said high-strength sidewall layer and the upper layer is said low-strength sidewall layer; when L > h1+h2, the steel boxed cofferdam sidewall comprises at least three layers, wherein the lowermost layer is said low-strength sidewall layer and is fully filled with underwater compartment concrete, the penultimate layer is said high-strength sidewall layer, and said high-strength sidewall layers are further superimposed upward until the height is greater than the water depth L during construction.

[0013] Preferably, h2 is 4 to 8 meters.

[0014] Preferably, h1 is 4 to 8 meters.

[0015] Preferably, h 2≥ h1.

[0016] The design and assembly methods for steel cofferdam sidewalls described above, applicable to environments with sudden water level changes and / or multi-site turnover, are mainly used in high-pile foundations with a design water depth of over 10m. The design includes a low-strength sidewall layer, a high-strength sidewall layer, and the low-strength sidewall layer can be fully filled with underwater compartment concrete after assembly. Among them, the high-strength sidewall layer uses large-sized materials, and the strength of the steel material can ensure the strength and rigidity of the cofferdam. The low-strength sidewall layer does not need to be filled with concrete and can be used alone when the pressure requirements for water pressure resistance are low. It can also be used in conjunction with the full filling of underwater compartment concrete, and the strength and rigidity of the cofferdam are ensured by the mixed strength of the low-strength sidewall layer and the concrete. High-strength sidewalls are generally not filled with concrete and can be reused. They can be reused on different steel cofferdams at the construction site, but they are heavier and relatively more expensive. Low-strength sidewalls, if filled with concrete, cannot be reused, but they are lighter and relatively less expensive. The combination of these structures can maximize construction safety, reduce construction costs, and ensure the rationality of cofferdam design under large water level differences.

[0017] If only one cofferdam needs to be built at the construction site, and the actual water level is lower than the design depth, the previously estimated extra high-strength straight section and high-strength corner section sidewalls can be discarded. These sections can be transferred to other projects or the steel can be recycled for other uses. This invention is particularly suitable for construction sites with multiple cofferdams, i.e., multi-work sites. In cases of sudden water level changes, if the actual water level is lower than the design level, the previously estimated extra high-strength straight section, high-strength corner section, and / or low-strength straight section, low-strength corner section sidewalls can be applied to cofferdam construction at other work sites. This satisfies rigidity and strength requirements while reasonably reducing costs. If the actual water level is higher than the design level, the high-strength straight section of other cofferdams can be adjusted. Sidewall segments, high-strength corner zone sidewall segments, and / or low-strength straight zone sidewall segments and low-strength corner zone sidewall segments are initially concentrated for the construction of some cofferdams. At the same time, supplementary sidewall segments are fabricated to achieve synchronous construction and fabrication, so as to shorten the construction period as much as possible. Meanwhile, for cofferdams constructed at different construction periods, the low-strength straight zone sidewall segments, high-strength straight zone sidewall segments, low-strength corner zone sidewall segments, and high-strength corner zone sidewall segments that have not been filled with concrete can be reused, which also helps to reduce costs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the sidewall segment of the high-strength straight zone #1 in one embodiment.

[0019] Figure 2This is a schematic diagram of the side wall segment of the high-strength corner zone #2 in one embodiment.

[0020] Figure 3 This is a schematic diagram of the structure of the side wall segment of the high-strength corner zone #3 in one embodiment.

[0021] Figure 4 This is a schematic diagram of the side wall segment of the high-strength corner zone #4 in one embodiment.

[0022] Figure 5 This is a schematic diagram of the structure of the side wall segment of the high-strength corner zone #5 in one embodiment.

[0023] Figure 6 This is a schematic diagram of the structure of the sidewall segment of the #1 low-intensity straight zone in one embodiment.

[0024] Figure 7 This is a schematic diagram of the side wall segment of the No. 2 low-intensity corner area in one embodiment.

[0025] Figure 8 This is a schematic diagram of the side wall segment of the No. 3 low-intensity corner area in one embodiment.

[0026] Figure 9 This is a schematic diagram of the side wall segment of the No. 4 low-intensity corner area in one embodiment.

[0027] Figure 10 This is a schematic diagram of the structure of the side wall segment of the No. 5 low-intensity corner area in one embodiment.

[0028] Figure 11 This is a schematic diagram of the structure of a type A steel caisson cofferdam in one embodiment.

[0029] Figure 12 This is a schematic diagram of the structure of a B-type steel caisson cofferdam in one embodiment.

[0030] Figure 13 This is a schematic diagram of the structure of a C-shaped steel caisson cofferdam in one embodiment.

[0031] Figure 14 This is a schematic diagram of the structure of a D-shaped steel caisson cofferdam in one embodiment.

[0032] Figure 15 It is a structural diagram of vertical ribs, force transmission rods, and ring plates.

[0033] In the figure, the following are the side wall segments: 1# high-strength straight section 1, 2# high-strength corner section 2, 3# high-strength corner section 3, 4# high-strength corner section 4, 5# high-strength corner section 5, 1# low-strength straight section 6, 2# low-strength corner section 7, 3# low-strength corner section 8, 4# low-strength corner section 9, 5# low-strength corner section 10, A-type steel caisson cofferdam 11, B-type steel caisson cofferdam 12, C-type steel caisson cofferdam 13, D-type steel caisson cofferdam 14, ring plate 15, vertical rib 16, and force transmission rod 17. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0035] In the description of this invention, it should be noted that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of this invention is usually placed when in use. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0036] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0037] A design method for the sidewall of a steel caisson cofferdam suitable for environments with sudden water level changes and / or multiple work sites includes the following steps: The sidewall of the cofferdam is designed in layers along the vertical direction of the cofferdam, including a high-strength sidewall layer and a low-strength sidewall layer. Vertical ribs 16 and / or dowel bars 17 and / or ring plates 15 are used to construct the high-strength sidewall layer, and the material specifications are correspondingly larger than those used to construct the low-strength sidewall layer. The high-strength sidewall layer uses large-sized materials, relying on the strength of the steel material to ensure the cofferdam's ability to withstand water pressure. The low-strength sidewall layer does not require concrete pouring and can be used alone when the water pressure requirements are lower. It can also be used in conjunction with fully poured underwater compartment concrete, relying on the combined strength of the low-strength sidewall layer and concrete to ensure the cofferdam's ability to withstand water pressure, and its ability to withstand water pressure is greater than that of the high-strength sidewall layer. High-strength sidewall layers are generally not filled with concrete, resulting in greater weight and relatively higher cost. However, they can be reused. If they are reused frequently or replaced in multiple work sites where the quantity of low-strength sidewall layers is insufficient, construction costs can be effectively reduced. Low-strength sidewall layers can be selectively filled with or not filled with concrete, depending on the load-bearing requirements. If they are filled with concrete, they cannot be reused, but they are lighter and have a relatively lower cost. The above structures can be used in combination, taking into account factors such as the cost of repeated reuse, load-bearing capacity, and the overall buoyancy of the steel caisson on the cofferdam.

[0038] Preferably, to facilitate the prefabrication of the cofferdam in standard segments at the factory and subsequent transportation to the construction site for assembly, the high-strength sidewall layer adopts a segmented design, including high-strength straight-area sidewall segments and high-strength corner-area sidewall segments. Based on the dimensions of the cofferdam sidewall, several high-strength straight-area sidewall segments and several high-strength corner-area sidewall segments are laterally assembled to form one layer of cofferdam sidewall. The high-strength straight-area sidewall segments are straight with both ends flush, while the high-strength corner-area sidewall segments are corner-shaped, matching the corner shape of the cofferdam sidewall, or with one end flush and the other end oblique, matching the shape of one side of the cofferdam sidewall. If the cofferdam is square, it will be a right-angled trapezoidal shape. The shape of the segment matches the shape of the corner of the cofferdam; similarly, the low-strength sidewall layer is designed in sections, including low-strength straight section sidewall segments and low-strength corner section sidewall segments. According to the size of the cofferdam sidewall, several low-strength straight section sidewall segments and several low-strength corner section sidewall segments are horizontally assembled together to form a layer of cofferdam sidewall; the low-strength straight section sidewall segments are straight, and the low-strength corner section sidewall segments are corner-shaped, matching the corner shape of the cofferdam sidewall, or one end is flush and the other end is oblique, matching the shape of one side of the cofferdam sidewall. If it is a square cofferdam, it is a right trapezoid shape. The shape of the low-strength corner section sidewall segments matches the shape of the corner of the cofferdam.

[0039] More preferably, to facilitate standardized processing and on-site assembly, the length and width of the high-strength straight-line sidewall segment and the low-strength straight-line sidewall segment are equal. Here, the length and width refer to the length and width of the outer edge. Similarly, the outer edge cross-sectional shape of the high-strength corner sidewall segment and the low-strength corner sidewall segment at the same vertical cofferdam sidewall location is the same.

[0040] Furthermore, this embodiment provides materials for manufacturing key components of the high-strength sidewall layer and the low-strength sidewall layer, combined with... Figure 15 As shown, referring to conventional cofferdam design, a dowel bar 17 connects the inner and outer sidewalls. Vertical ribs 16 are vertically welded to the inner sides of both the inner and outer sidewalls, and ring plates 15 are horizontally welded to them. Specifically: In the high-strength sidewall layer, the vertical ribs 16 are made of L125mm×125mm×12mm or larger; the dowel bars 17 are made of [20 channel steel or larger; and the ring plates 15 are made of 16mm thick steel plates or larger. In the low-strength sidewall layer, the vertical ribs 16 are made of L75mm×75mm×5mm or larger; the dowel bars 17 are made of [10 channel steel or larger; and the ring plates 15 are made of 10mm thick steel plates or larger.

[0041] More preferably, when there are cofferdams of different sizes at the same construction site, the lengths and widths of multiple high-strength straight-area sidewall segments and multiple low-strength straight-area sidewall segments are equal according to the size of the cofferdam. The dimensions of the high-strength corner-area sidewall segments at different vertical cofferdam sidewall positions are designed according to the principle that the length / width of the cofferdam formed by splicing several high-strength straight-area sidewall segments and several high-strength corner-area sidewall segments is at least 0.1m greater than the length / width of the corresponding pier cap. The optimal design is to minimize the number of high-strength corner-area sidewall segments with different cross-sectional dimensions required for the design. Here, "several" can be 0, that is, in actual splicing, depending on the length, the long or short side may not use high-strength straight-area sidewall segments, and two high-strength corner-area sidewall segments can be spliced ​​together. The low-strength corner-area sidewall segments are designed with reference to the design principles of high-strength corner-area sidewall segments. The design method of this embodiment is mainly applied to high-pile pier caps with a design water depth of more than 10m. If only one cofferdam needs to be built at the construction site, and the actual water level is lower than the design depth, the previously estimated extra high-strength straight section and high-strength corner section sidewalls can be discarded. These sections can be transferred to other projects or the steel can be recycled for other uses. This embodiment is particularly suitable for situations with multiple cofferdams at the same construction site, i.e., multi-worksite situations. In the event of a sudden change in water level, if the actual water level is lower than the design level, the previously estimated extra high-strength straight section, high-strength corner section, and / or low-strength straight section and low-strength corner section sidewalls can be applied to other cofferdam constructions. This satisfies the rigidity and strength requirements while reasonably reducing costs. If the actual water level is higher than the design level, the high-strength straight section sidewalls of other cofferdams can be adjusted. Sidewall segments, high-strength corner section sidewall segments, and / or low-strength straight section sidewall segments and low-strength corner section sidewall segments are initially concentrated for the construction of some cofferdams. At the same time, supplementary sidewall segments are fabricated to achieve simultaneous construction and fabrication, so as to shorten the construction period as much as possible. Meanwhile, for cofferdams constructed at different times, the low-strength straight section sidewall segments, high-strength straight section sidewall segments, low-strength corner section sidewall segments, and high-strength corner section sidewall segments that have not been filled with concrete can be reused, which also helps to reduce costs.

[0042] The present invention further provides an assembling method for a steel boxed cofferdam side wall based on the above steel boxed cofferdam side wall design method suitable for sudden water level change environments and / or multi-construction site turnover, wherein the height of a high-strength side wall layer is h1, the height of a low-strength side wall layer is h2, and the actual water level depth during construction is L; when L < h2 and L < h1, a low-strength side wall layer or a high-strength side wall layer is adopted as the steel boxed cofferdam side wall; when L < h2 and L > h1, a low-strength side wall layer is adopted as the steel boxed cofferdam side wall; when h2 < L < h1+h2, the steel boxed cofferdam side wall comprises two layers, wherein the lower layer is a high-strength side wall layer and the upper layer is a low-strength side wall layer; if L simultaneously satisfies L < 2h1, two high-strength side wall layers can be selected as the steel boxed cofferdam side wall; when L > h1+h2, the steel boxed cofferdam side wall comprises at least three layers, wherein the lowermost layer is a low-strength side wall layer and is fully filled with underwater compartment concrete, the penultimate layer is a high-strength side wall layer, and low-strength side wall layers and / or high-strength side wall layers are further stacked upwards until the height is greater than the construction water level depth L, or the lowermost layer and the penultimate layer are low-strength side wall layers and are fully filled with underwater compartment concrete, and low-strength side wall layers and / or high-strength side wall layers are further stacked upwards until the height is greater than the construction water level depth L.

[0043] In the above assembling method, the present embodiment provides an optimal method: when L < h2, a low-strength side wall layer is adopted as the steel boxed cofferdam side wall; at this time, the water depth is shallow, the requirement for bearing water pressure can be satisfied by adopting the low-strength side wall layer without concrete pouring, and the low-strength side wall layer can also be reused for turnover; when h2 < L < h1+h2, the steel boxed cofferdam side wall comprises two layers, wherein the lower layer is a high-strength side wall layer and the upper layer is a low-strength side wall layer, so that both the high-strength side wall layer and the low-strength side wall layer can be reused for turnover; when L > h1+h2, the steel boxed cofferdam side wall comprises at least three layers, wherein the lowermost layer is a low-strength side wall layer and is fully filled with underwater compartment concrete, which improves the rigidity and strength of the bottom of the cofferdam, the penultimate layer (i.e., the layer above the lowermost layer) is a high-strength side wall layer, and high-strength side wall layers are further stacked upwards until the height is greater than the construction water level depth L, and the high-strength side wall layers arranged at the upper part are more convenient for full turnover use, which reduces construction cost. When the first cofferdam is installed by the above optimal assembling method, the operation can be preferentially performed according to this method due to sufficient side wall segments; when subsequent cofferdams are installed, one of the multiple assembling methods provided in the present embodiment is selected according to the remaining condition of the side wall segments. During assembling, layers are only required to be fixed to each other, and welding can be adopted as a fixing method; of course, bolt connection and other methods can also be adopted as required.

[0044] Further, regarding the height of each layer, h2 is preferably 4 to 8 meters, and h1 is preferably 4 to 8 meters, which are reasonably divided according to the design water level depth and water pressure.

[0045] Further, regarding the height of each layer, h 2≥h1, with equal strength, is easier to process. The outer and inner sidewalls of the low-strength sidewall layer and the high-strength sidewall layer can be processed according to the same standard.

[0046] For easier understanding, this embodiment uses the Zaoshi Reservoir Bridge in the TJ4 section of the Luci Expressway as an example. The following method adopts the most optimized design approach that is easy to manufacture. Specifically, the left span pier #3, right span pier #4, left span pier #4, and right span pier #5 of Bridge No. 1, and the left and right spans piers #1, #2, #13, and #14 of the Zaoshi Reservoir No. 3 Extra-Large Bridge are all underwater piers. The pier design parameters are as follows: Table 1 Design Parameters of Foundation

[0047] Based on the cofferdam wall thickness and the dimensions of the foundation, calculate the minimum dimensions of the actual cofferdam length and width (corresponding length / width + wall thickness × 2 + 0.1; if two foundations are constructed together, the length also needs to include the distance between the two foundations; if the foundations are inclined, the inclination dimension also needs to be added; unit: m). Table 2 Minimum Dimensions for Steel Cofferdam Design

[0048] Based on the outer edge dimensions of the aforementioned steel caisson cofferdam, ten different structural forms of sidewall segments were designed, combined with... Figure 1-10As shown, there is one high-strength straight section sidewall segment, namely segment 1 (high-strength straight section sidewall segment 1); four high-strength corner section sidewall segments, namely segments 2 (high-strength corner section sidewall segment 2), 3 (high-strength corner section sidewall segment 3), 4 (high-strength corner section sidewall segment 4), and 5 (high-strength corner section sidewall segment 5); one low-strength straight section sidewall segment, namely segment 6 (low-strength straight section sidewall segment 1); and four low-strength corner section sidewall segments, namely segments 7 (low-strength corner section sidewall segment 2), 8 (low-strength corner section sidewall segment 3), 9 (low-strength corner section 4), and 10 (low-strength corner section sidewall segment 5). Based on the outer edge dimensions of the cofferdam, the length of segment 1 (high-strength straight section sidewall segment 1) is 5.390m, the sidewall length of segment 2 (high-strength corner section sidewall segment 2) is 4.796m, and the length of segment 3 (high-strength corner section sidewall segment 4) is... The sidewall length of segment 3 in the high-strength corner zone is 2.676m, the sidewall length of segment 4 in the high-strength corner zone is 7.176m, and the sidewall length of segment 5 in the high-strength corner zone is 5.266m. Correspondingly, the length and width of the sidewall segments in the low-strength straight zone are equal to those in the high-strength straight zone. The sidewall segments in the low-strength corner zone at the same height position have the same cross-sectional shape at their outer edges as those in the high-strength corner zone. Therefore, the corresponding sidewall lengths are as follows: segment 6 in the low-strength straight zone is 5.390m, segment 7 in the low-strength corner zone is 4.796m, segment 8 in the low-strength corner zone is 2.676m, segment 9 in the low-strength corner zone is 7.176m, and segment 10 in the low-strength corner zone is 5.266m.

[0049] Combination Figure 11-14 As shown, when assembling using the above-mentioned sidewall segments, taking the high-strength sidewall layer as an example, the combinations of each sidewall segment are shown in Table 3 (the length unit in Table 3 is m): Table 3. Schematic diagram of sidewall segment assembly

[0050] As can be seen from Table 2, the actual length and width of the cofferdam after assembly are both greater than the minimum length and width that the cofferdam design should meet.

[0051] Based on the sidewall length in the high-strength sidewall layer and the wall thickness of 1.2m, the lengths of each side can be calculated, as shown in Table 4: Table 4 Dimensions (m) of sidewall segments in high-strength straight zones and high-strength corner zones

[0052] The sidewall segments in the low-strength straight zone and low-strength corner zone can be designed by referring to the dimensions of the sidewall segments in the high-strength straight zone and high-strength corner zone.

[0053] The heights of the high-strength straight section side wall segment, high-strength corner section side wall segment, low-strength straight section side wall segment and low-strength corner section side wall segment are all designed to be 6m.

[0054] When L<6m, the side wall of the steel boxed cofferdam adopts a low-strength side wall layer. At this time, the water level depth is relatively shallow. The use of the low-strength side wall layer, which does not require concrete pouring, can meet the bearing capacity requirement for water pressure, and the low-strength side wall layer can also be reused for repeated turnover; when 6<L<12m, the side wall of the steel boxed cofferdam comprises two layers, the lower layer is a high-strength side wall layer and the upper layer is a low-strength side wall layer, thus both the high-strength side wall layer and the low-strength side wall layer can be reused for repeated turnover; when L>h1+h2, the side wall of the steel boxed cofferdam comprises at least three layers, the lowermost layer is a low-strength side wall layer which is fully filled with underwater compartment concrete to improve the stiffness and strength of the bottom of the cofferdam, the penultimate layer (i.e., the layer above the lowermost layer) is a high-strength side wall layer, and then high-strength side wall layers are superimposed upwards until the height is higher than the water level depth L during construction, and the adoption of high-strength side wall layers at the upper part can improve the turnover rate in later dismantling.

[0055] Adopting the design method and assembling method of this embodiment can ensure construction safety to the greatest extent, reduce construction cost, and also ensure the reasonability of the boxed cofferdam design under large water level drop.

Claims

1. A design method for the sidewall of a steel caisson cofferdam suitable for environments with sudden water level changes and / or multiple work sites, characterized in that... Includes the following steps: Along the vertical direction of the cofferdam, the cofferdam sidewalls are designed in layers, including a high-strength sidewall layer and a low-strength sidewall layer. The material specifications of the vertical ribs, force transmission rods and ring plates used to make the high-strength sidewall layer are greater than those of the vertical ribs, force transmission rods and ring plates used to make the low-strength sidewall layer. Along the horizontal direction of the cofferdam, the high-strength sidewall layer is designed in sections, including high-strength straight section sidewall segments and high-strength corner section sidewall segments. According to the dimensions of the cofferdam sidewall, several high-strength straight section sidewall segments and several high-strength corner section sidewall segments are horizontally assembled together to form a layer of cofferdam sidewall. The high-strength straight section sidewall segments are straight, and the high-strength corner section sidewall segments are corner-shaped, or one end is flat and the other end is oblique. The segmented design of the low-strength sidewall layer includes low-strength straight-area sidewall segments and low-strength corner-area sidewall segments. According to the dimensions of the cofferdam sidewall, several low-strength straight-area sidewall segments and several low-strength corner-area sidewall segments are horizontally assembled together to form a layer of cofferdam sidewall. The low-strength straight-area sidewall segments are straight, and the low-strength corner-area sidewall segments are corner-shaped, or have one end flat and the other end oblique. The length and width of the high-strength straight-line zone sidewall segment and the low-strength straight-line zone sidewall segment are equal; the outer edge cross-sectional shape of the high-strength corner zone sidewall segment and the low-strength corner zone sidewall segment at the same vertical cofferdam sidewall position is the same; The vertical ribs of the high-strength sidewall layer are made of materials with a specification of L125mm×125mm×12mm or larger. The high-strength sidewall layer uses [20 channel steel or larger specification material] as the force transmission rod. The ring plate of the high-strength sidewall layer is made of steel plate with a thickness of 16mm or larger. The vertical ribs of the low-strength sidewall layer are made of materials with a specification of L75mm×75mm×5mm or larger. The material specifications used for the force transmission rods of the low-strength sidewall layer are [10 channel steel or larger specifications]. The annular plate of the low-strength sidewall layer is made of steel plate with a thickness of 10mm or larger.

2. The design method for the sidewall of a steel cofferdam suitable for environments with sudden water level changes and / or multiple work sites, as described in claim 1, is characterized in that: When there are cofferdams of different sizes at the same construction site, the lengths and widths of the multiple high-strength straight-line sidewall segments and the multiple low-strength straight-line sidewall segments are equal, according to the size of the cofferdam. The dimensions of the high-strength corner sidewall segments at different vertical cofferdam sidewall positions are designed according to the principle that the length / width of the cofferdam formed by splicing several high-strength straight-line sidewall segments and several high-strength corner sidewall segments is at least 0.1m greater than the length / width of the corresponding pier. The optimal design is to minimize the number of high-strength corner sidewall segments with different cross-sectional dimensions required by the design, where several can be 0. The low-strength corner sidewall segments are designed with reference to the design principles of the high-strength corner sidewall segments.

3. A method for assembling the sidewalls of a steel caisson cofferdam, based on the design method for the sidewalls of a steel caisson cofferdam suitable for environments with sudden water level changes and / or multiple work sites as described in claim 1 or 2, is characterized in that: The height of the high-strength side wall layer is h1, and the height of the low-strength side wall layer is h2, h 2≥ h1, and the actual water level depth during construction is L; when L < h2 and L < h1, the side wall of the steel boxed cofferdam adopts the low-strength side wall layer or the high-strength side wall layer; when L < h2 and L > h1, the side wall of the steel boxed cofferdam adopts the low-strength side wall layer; when h2 < L < h1+h2, the side wall of the steel boxed cofferdam comprises two layers, wherein the lower layer is the high-strength side wall layer and the upper layer is the low-strength side wall layer; if L simultaneously satisfies L < 2h1, both layers of the side wall of the steel boxed cofferdam are the high-strength side wall layers; when L > h1+h2, the side wall of the steel boxed cofferdam comprises at least three layers, the lowermost layer is the low-strength side wall layer and is fully filled with underwater compartment concrete, the penultimate layer is the high-strength side wall layer, and the low-strength side wall layer and / or the high-strength side wall layer are further superposed upward until the height is higher than the actual water level depth L during construction, or the lowermost layer and the penultimate layer are the low-strength side wall layer and are fully filled with underwater compartment concrete, and the low-strength side wall layer and / or the high-strength side wall layer are further superposed upward until the height is higher than the actual water level depth L during construction.

4. The method for assembling the sidewalls of a steel caisson cofferdam according to claim 3, characterized in that: h2 is 4~8 meters.

5. The method for assembling the sidewalls of a steel cofferdam according to claim 3, characterized in that: h1 is 4~8 meters.

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