Construction method for converting single-wall cofferdam into double-wall cofferdam

Abstract

The application discloses a construction method for changing a single-wall cofferdam into a double-wall cofferdam, which comprises the following steps: underwater terrain exploration on the outside of the single-wall cofferdam, leveling the covering layer or bare rock surface on the outside of the single-wall cofferdam; installing an outside cofferdam on the outside of the single-wall cofferdam during a low water level period; performing joint sealing of the outside cofferdam; filling the joint with bagged concrete by means of a diving plug on the periphery of the outside cofferdam, and then pouring concrete between the single-wall cofferdam and the outside cofferdam; after the strength of the concrete between the single-wall cofferdam and the outside cofferdam reaches a design requirement, performing hierarchical water pumping and layered installation of inner supports in the cofferdam, and preparing for construction of a bearing platform. The construction method for changing the single-wall cofferdam into the double-wall cofferdam changes the structure of the single-wall cofferdam into the structure of the double-wall cofferdam, increases the structural strength of the original single-wall steel cofferdam under the condition of a flood period or a high water level, reduces the influence of the flood period or the high water level, guarantees the continuity of bridge foundation construction, ensures the implementation period, and avoids increase of project cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of bridge construction technology, in particular to a construction method for converting a single-wall cofferdam into a double-wall cofferdam. BACKGROUND

[0002] In the bridge foundation design of the reservoir area in the upper reaches of the Yangtze River, in order to reduce the excavation depth of the foundation pit, the pile end is designed to be on the overburden layer or bare rock surface, and the pile cap bottom is placed thereon. The reservoir area bridge foundation construction is greatly affected by the water level of the Three Gorges, and the operation time is short. Generally, the bridge foundation construction is carried out in the dry season, the pile foundation is constructed first, and then the steel cofferdam is constructed. After the pile foundation construction is completed, the site is leveled, the steel cofferdam is assembled on the pile cap boundary line, and the bottom sealing concrete is poured to form a water retaining structure.

[0003] The single-wall steel cofferdam is a large-scale temporary facility for the construction of deep-water bridge piers of large and medium-sized bridges. It has good waterproof performance, light structure, small manufacturing and installation difficulty, high positioning accuracy, and can be used as a water retaining structure for bridge underwater foundation. Therefore, it has unique advantages in the construction of deep-water pier body of bridges. However, due to insufficient experience, incomplete boundary condition consideration, improper construction process control, or inadequate management measures, and other factors, the construction process of the original plan to construct the pile cap in the dry season is delayed, and the single-wall steel cofferdam needs to go through the flood period or high water level condition. The single-wall cofferdam structure does not consider the flood period or high water level condition in the design stage.

[0004] At present, the single-wall steel cofferdam is generally designed to wait for the next dry season under the design water pumping condition (i.e. the maximum water head difference condition considered in the design stage) and then the pile cap construction is carried out. The problem of this method is that it cannot form continuous operation. If this pile cap construction is the planned key line of the project, it will have a very bad impact on the implementation of the project, prolong the implementation period of the project, and increase the cost of the project. SUMMARY

[0005] Therefore, it is necessary to provide a construction method for converting a single-wall cofferdam into a double-wall cofferdam to solve the problem that the existing single-wall steel cofferdam does not consider the flood period or high water level condition, which prolongs the construction period of the project and increases the cost of the project.

[0006] A construction method for converting a single-wall cofferdam into a double-wall cofferdam, comprising the following steps:

[0007] Exploring the underwater topography outside the single-wall cofferdam and leveling the overburden layer or bare rock surface outside the single-wall cofferdam;

[0008] Installing the outside cofferdam outside the single-wall cofferdam during the low water level period;

[0009] Sealing the joint of the outside cofferdam;

[0010] The outer cofferdam peripheral submerged plug fills the bagged concrete to form a seal, and then the sandwich concrete between the single-wall cofferdam and the outer cofferdam is poured;

[0011] After the sandwich concrete strength reaches the design requirement, the inner support is installed by grading water pumping in the cofferdam, and the pile cap construction is prepared.

[0012] In one of the embodiments, before the step of exploring the underwater terrain outside the single-wall cofferdam and leveling the covering layer or bare rock surface outside the single-wall cofferdam, it further comprises:

[0013] According to the geological exploration data and hydrological conditions, the structural design and review calculation of changing the single-wall cofferdam to the double-wall cofferdam are carried out.

[0014] In one of the embodiments, the step of leveling the covering layer or bare rock surface outside the single-wall cofferdam is specifically:

[0015] The covering layer or bare rock surface outside the single-wall cofferdam is leveled by filling sandbags.

[0016] In one of the embodiments, the step of completing the installation of the outer cofferdam outside the single-wall cofferdam during the low water level period is specifically:

[0017] According to the structural characteristics of the outer cofferdam, the outer cofferdam is divided into multiple layers, and each single-layer cofferdam is divided into multiple segments.

[0018] The outer cofferdam is installed in layers and segments during the low water level period, each layer of cofferdam is fixedly connected with the single-wall cofferdam through horizontal cross braces, and the segments of the single-layer cofferdam are sequentially assembled.

[0019] In one of the embodiments, the upper part of the first layer of cofferdam is fixedly connected with the single-wall cofferdam through horizontal cross braces, and the lower part of the first layer of cofferdam is fixedly connected with the single-wall cofferdam through flower basket bolt pull rods.

[0020] In one of the embodiments, the horizontal cross brace is located in a horizontal plane, and the connection point of the flower basket bolt pull rod and the single-wall cofferdam is higher than the connection point of the flower basket bolt pull rod and the outer cofferdam.

[0021] In one of the embodiments, the step of sealing the joint of the outer cofferdam is specifically:

[0022] The water stop tape is attached to the inner and outer sides of the joint of the outer cofferdam;

[0023] The bolt backing plate is provided on the inner water stop tape, and the connecting steel plate is provided on the outer water stop tape;

[0024] The bolt backing plate and the connecting steel plate are fixedly connected through connecting bolts.

[0025] In one of the embodiments, the method further comprises the step of:

[0026] The outer cofferdam is located at the joint of the upper part of the double-wall concrete, and the grouting sealing treatment is performed before the water is pumped out of the cofferdam.

[0027] In one of the embodiments, the step of performing the grouting sealing treatment before the water is pumped out of the cofferdam specifically comprises:

[0028] The U-shaped steel plate is installed between the two vertical ribs adjacent to the joint, and the U-shaped steel plate, the two vertical ribs and the outer wall plate form a grouting sealing treatment area;

[0029] The concrete grout is filled in the grouting sealing treatment area, and after the concrete grout solidifies to meet the design requirements, the U-shaped steel plate is retained as part of the joint sealing measure.

[0030] In one of the embodiments, the step of pouring the double-wall concrete between the single-wall cofferdam and the outer cofferdam specifically comprises:

[0031] The single-wall cofferdam and the outer cofferdam form a double-wall cofferdam, and a working platform is installed at the top end of the double-wall cofferdam;

[0032] A collecting hopper is installed on the working platform, and the concrete is poured through the collecting hopper between the single-wall cofferdam and the outer cofferdam.

[0033] The single-wall cofferdam changes into a double-wall cofferdam, and the method has at least the following advantages:

[0034] 1. The single-wall cofferdam changes into a double-wall cofferdam, which increases the structural strength of the original single-wall steel cofferdam under the condition of flood period or high water level, reduces the influence of flood period or high water level, ensures the continuity of bridge foundation construction, guarantees the implementation period, and avoids the increase of project cost.

[0035] 2. The changed double-wall steel cofferdam has more reasonable structure stress under the requirement of structural strength under the condition of flood period or high water level.

[0036] 3. The double-wall steel cofferdam structure is economical in cost, small in construction difficulty, and controllable in quality. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the specific embodiments of the present application, the following will briefly introduce the drawings needed to be used in the specific embodiments. In all the drawings, the elements or parts are not necessarily drawn according to the actual proportion.

[0038] Figure 1 A flow chart of the method for changing the single-wall cofferdam into a double-wall cofferdam in one of the embodiments;

[0039] Figure 2 Structure diagram of single-wall cofferdam in an embodiment;

[0040] Figure 3 Structure diagram of single-wall cofferdam in an embodiment; Figure 2

[0041] Figure 4 Figure 2

[0042] Figure 5 Figure 3

[0043] Figure 6

[0044] Figure 7

[0045] Figure 8 Figure 6

[0046] Figure 9

[0047] Figure 10

[0048] Figure 11

[0049] Figure 12

[0050] Figure 13

[0051] Reference signs:

[0052] ​​​​​​​​​​​​​​10 - double-wall cofferdam, 11 - single-wall cofferdam, 111 - wall plate, 112 - cross rib, 113 - vertical rib, 114 - bracing purlin, 115 - inner support, 116 - bottom sealing concrete, 117 - hole cutting, 12 - outer cofferdam, 121 - outer wall plate, 122 - long side segment, 123 - short side segment, 124 - round steel hook, 13 - horizontal cross brace, 14 - sack concrete, 15 - sandwich concrete, 16 - basket bolt tension rod, 20 - sand bag, 30 - waterstop, 32 - bolt backing plate, 34 - connecting steel plate, 36 - connecting bolt, 40 - installation platform, 42 - aggregate hopper, 50 - U-shaped steel plate, 52 - pressure grouting sealing treatment area. DETAILED DESCRIPTION

[0053] In order to make the above objectives, features and advantages of the present application more obvious and easy to understand, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, a large number of specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the scope of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0054] It should be noted that when an element is referred to as being "fixed" to another element, it can be directly on the other element or there can be an intervening element. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or there can be an intervening element. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description of the application herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0056] Referring to Figure 1 A construction method for converting a single-wall cofferdam into a double-wall cofferdam, which is mainly applicable to bridge deep water construction under large amplitude bare rock conditions. Specifically, the construction method comprises the following steps:

[0057] Step S110: Exploring the outer terrain of the single-wall cofferdam 11, and leveling the covering layer or bare rock layer outside the single-wall cofferdam 11.

[0058] Referring to Figures 2 to 4Specifically, first, the terrain outside the single-wall cofferdam 11 is explored to understand the terrain outside the single-wall cofferdam 11. The terrain exploration can be performed by manual diving exploration or by collecting images by a robot. After the underwater terrain exploration outside the single-wall cofferdam 11 is completed, the covering layer or bare rock layer outside the single-wall cofferdam 11 is leveled by filling sandbags 20 to facilitate the initial positioning of the outside cofferdam 12. It should be understood that the leveling of the covering layer or bare rock layer is not limited to the filling of sandbags 20, but can also be achieved by other methods, such as by excavating or excavating the rock layer to level the terrain.

[0059] In an embodiment, before step S110, the method further includes the step of: according to the geological exploration data and hydrological conditions, changing the structure design of the single-wall cofferdam 11 to the double-wall cofferdam 10 and reviewing the calculation to prepare for the construction. Specifically, the single-wall cofferdam 11 and the double-wall cofferdam 10 are both steel cofferdams, and the structures of the single-wall cofferdam 11 and the double-wall cofferdam 10 are as follows:

[0060] Please refer to Figure 2 The single-wall cofferdam 11 includes a wall plate 111, a horizontal rib 112, a vertical rib 113, a surrounding purlin 114, an inner support 115, and a bottom sealing concrete 116. The wall plate 111 forms a closed space to form a cofferdam, the horizontal rib 112 and the vertical rib 113 are arranged on the outside of the wall plate 111, the horizontal rib 112 is arranged horizontally on the wall plate 111, and the vertical rib 113 is arranged vertically on the wall plate 111 to strengthen the strength of the wall plate 111. The surrounding purlin 114 is installed on the inside of the wall plate 111, and the cross brace connects the two surrounding purlins 114 opposite to each other to achieve internal support of the wall plate 111.

[0061] Please refer to Figure 3 The double-wall cofferdam 10 includes the single-wall cofferdam 11, the outside cofferdam 12, the horizontal cross brace 13, the sack concrete 14, and the sandwich concrete 15. The outside cofferdam 12 includes an outer wall plate 121, a horizontal rib 112, and a vertical rib 113. The outer wall plate 121 surrounds the outside of the single-wall cofferdam 11, the horizontal rib 112 and the vertical rib 113 are arranged on the inside of the outer wall plate 121, and the horizontal rib 112 and the vertical rib 113 are arranged longitudinally and transversely to increase the strength of the outer wall plate 121. The horizontal cross brace 13 connects the outside cofferdam 12 and the single-wall cofferdam 11, the sack concrete 14 is filled in the bottom of the outer wall plate 121, and the sandwich concrete 15 is poured between the outside cofferdam 12 and the single-wall cofferdam 11.

[0062] Step S120: installing the outside cofferdam 12 outside the single-wall cofferdam 11 during the low water level period.

[0063] Please refer to Figure 5 Specifically, according to the structural characteristics of the outside cofferdam 12, the outside cofferdam 12 is divided into M layers, and each layer is divided into N segments. The height of the i-th layer is Hi m, the weight of a single segment (G±1) t. In an embodiment, the single-layer cofferdam is divided into four segments, including two long-side segments 122 and two short-side segments 123, the short-side segments 123 including curvedly extended right-angle portions.

[0064] Please refer to Figures 6 to 8 In the low-water period, the outer cofferdam 12 is installed in layers and segments, each layer of the cofferdam is fixedly connected to the single-wall cofferdam 11 through horizontal cross braces 13, and the segments of the single-layer cofferdam are sequentially assembled.

[0065] Further, for the first layer of the cofferdam, the upper part of the first layer of the cofferdam is fixedly connected to the single-wall cofferdam 11 through the horizontal cross brace 13, and the lower part of the first layer of the cofferdam is fixedly connected to the single-wall cofferdam 11 through the flower basket bolt pull rod 16. The flower basket bolt pull rod 16 can be telescoped by using a screw rod to adjust the distance and tension between the single-wall cofferdam 11 and the outer cofferdam 12. For other layers of the cofferdam, they are fixedly connected to the single-wall cofferdam 11 through the horizontal cross brace 13.

[0066] On the basis of the above embodiment, further, the horizontal cross brace 13 is located in the horizontal plane, while the flower basket bolt pull rod 16 is not in the horizontal plane, but is arranged at an angle to the horizontal plane. Specifically, the connection point of the flower basket bolt pull rod 16 and the single-wall cofferdam 11 is higher than the connection point of the flower basket bolt pull rod 16 and the outer cofferdam 12, so as to avoid the outer cofferdam 12 from being turned up.

[0067] In an embodiment, the vertical ribs 113 of the outer cofferdam 12 are pre-welded with round steel hooks 124, the vertical ribs 113 of the single-wall cofferdam 11 are provided with cut holes 117, and the two ends of the horizontal cross brace 13 or the flower basket bolt pull rod 16 are respectively connected to the round steel hooks 124 and the cut holes 117, so as to realize the fixed connection of the horizontal cross brace 13 and the flower basket bolt pull rod 16 to the outer cofferdam 12 and the single-wall cofferdam 11.

[0068] Step S130: Perform joint sealing of the outer cofferdam 12.

[0069] Please refer to Figure 9 Specifically, the inner and outer sides of the joint of the outer cofferdam 12 are attached with water stop belts 30, the inner water stop belt 30 is provided with a bolt backing plate 32, and the outer water stop belt 30 is provided with a connecting steel plate 34. A connecting bolt 36 is sequentially threaded through the bolt backing plate 32, the outer wall plate 121 and the connecting steel plate 34, so as to realize the fixed connection of the bolt backing plate 32 and the connecting steel plate 34. The bolt backing plate 32 cooperates with the connecting steel plate 34 to clamp and fix the water stop belt 30, so as to ensure that the water stop belt 30 is tightly attached to the joint of the outer cofferdam 12.

[0070] Step S140: Fill the joint with the diving plug bag concrete 14 around the outer cofferdam 12, and then pour the wall concrete 15 between the single-wall cofferdam 11 and the outer cofferdam 12.

[0071] Referring to Figure 10 and Figure 11 , specifically, after the outer cofferdam 12 is installed, there is a gap between the bottom of the cofferdam and the ground. In order to ensure the water stopping effect, the diving plug filled with bagged concrete 14 is located in the outer cofferdam 12 to block the gap. Then, the single-wall cofferdam 11 and the outer cofferdam 12 form the double-wall cofferdam 10, a working platform is installed at the top end of the double-wall cofferdam 10, and the aggregate hopper 42 is installed on the working platform. The concrete is poured between the single-wall cofferdam 11 and the outer cofferdam 12 through the aggregate hopper 42 to realize the pouring of the sandwiched concrete 15. The height of the sandwiched concrete 15 can be set according to actual engineering needs.

[0072] Step S150: After the sandwiched concrete 15 meets the design requirements, the cofferdam is graded pumped and the inner support 115 is installed layer by layer to prepare for the construction of the pile cap.

[0073] Referring to Figure 12 , specifically, after the sandwiched concrete 15 meets the design requirements, the cofferdam is graded pumped, and the cofferdam purlin 114 and the inner support 115 are installed after each pumping level is completed to ensure the water retaining strength of the double-wall cofferdam 10. After the construction of the inner support 115 in the double-wall cofferdam 10 is completed, the bottom sealing concrete 116 is poured to prepare for the construction of the pile cap.

[0074] Referring to Figure 13 , in an embodiment, in order to ensure the water retaining performance of the cofferdam, after the strength of the sandwiched concrete 15 reaches the design strength and before the cofferdam is pumped, the joint of the outer cofferdam 12 above the sandwiched concrete 15 is subjected to grouting sealing treatment.

[0075] Further, on the basis of the above embodiment, the step of grouting sealing treatment is specifically: installing a U-shaped steel plate 50 between two adjacent vertical ribs 113 of the joint, and the U-shaped steel plate 50, the two vertical ribs 113 and the outer wall plate 121 form a grouting sealing treatment area 52. Fill the concrete grout in the grouting sealing treatment area 52, and after the concrete grout solidifies to meet the design requirements, the U-shaped steel plate 50 is retained as part of the joint sealing measure.

[0076] The above construction method of converting the single-wall cofferdam into the double-wall cofferdam has at least the following advantages:

[0077] 1. By converting the single-wall cofferdam 11 into the double-wall cofferdam 10, the structural strength of the original single-wall steel cofferdam is increased under the condition of flood period or high water level, the influence of flood period or high water level is reduced, the continuity of bridge foundation construction is ensured, the implementation period can be ensured, and the increase of project cost is avoided.

[0078] 2. The changed double-wall steel cofferdam has more reasonable structure stress under the requirement of structural strength in flood period or high water level working condition.

[0079] 3. The double-wall steel cofferdam has economic structure cost, small construction difficulty and controllable quality.

[0080] The above examples are only used to illustrate the technical solutions of the present application, but not limit the present application; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that the technical solutions recorded in the foregoing examples can be modified, or some or all of the technical features can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should be covered in the scope of the claims and the description of the present application.

Claims

1. A construction method for converting a single-wall cofferdam into a double-wall cofferdam, characterized in that, Includes the following steps: Underwater topographic survey of the outer side of the single-walled cofferdam, and leveling of the overburden or bare rock surface on the outer side of the single-walled cofferdam; During periods of low water levels, the installation of the outer cofferdam is completed on the outside of the single-wall cofferdam. Perform the sealing of the joints of the outer cofferdam; The outer cofferdam is surrounded by underwater sack concrete to form a seal, and then the interlayer concrete between the single-wall cofferdam and the outer cofferdam is poured. After the concrete strength of the interlayer wall reaches the design requirements, the internal support is installed in stages and pumped out in stages within the cofferdam to prepare for the construction of the foundation. The specific steps for completing the installation of the outer cofferdam on the outside of the single-wall cofferdam during the low water level period are as follows: Based on the structural characteristics of the outer cofferdam, the outer cofferdam is divided into multiple layers, and each layer of cofferdam is further divided into multiple segments. During periods of low water levels, the outer cofferdam is installed in layers and sections. Each layer of cofferdam is fixedly connected to the single-wall cofferdam by horizontal bracing. The sections of the single-layer cofferdam are assembled in sequence. The upper part of the first layer of cofferdam is fixed to the single-wall cofferdam by horizontal bracing, and the lower part of the first layer of cofferdam is fixed to the single-wall cofferdam by turnbuckle tie rods. The horizontal cross brace is located in the horizontal plane, and the connection point between the turnbuckle tie rod and the single-wall cofferdam is higher than the connection point between the turnbuckle tie rod and the outer cofferdam.

2. The construction method for converting a single-wall cofferdam into a double-wall cofferdam according to claim 1, characterized in that, Before the underwater topographic survey and leveling of the overburden or bare rock surface outside the single-wall cofferdam, the following steps are also included: Based on geological survey data and hydrological conditions, the structural design and verification calculation of changing a single-wall cofferdam to a double-wall cofferdam were carried out.

3. The construction method for converting a single-wall cofferdam into a double-wall cofferdam according to claim 1, characterized in that, The specific steps for leveling the overburden or bare rock surface on the outer side of the single-wall cofferdam are as follows: Sandbags were dumped to level the outer cover layer or bare rock surface of the single-walled cofferdam.

4. The construction method for converting a single-wall cofferdam into a double-wall cofferdam according to claim 1, characterized in that, The specific steps for sealing the joints of the outer cofferdam are as follows: Waterstop strips are attached to both the inner and outer sides of the outer cofferdam joint; A bolt washer is provided on the inner side of the waterstop, and a connecting steel plate is provided on the outer side of the waterstop; The bolt washer and the connecting steel plate are fixedly connected by connecting bolts.

5. The construction method for converting a single-wall cofferdam into a double-wall cofferdam according to claim 1, characterized in that, Before proceeding with the steps of staged dewatering and layered installation of internal supports within the cofferdam, the following steps are also included: The joint of the outer cofferdam located above the concrete of the inner wall is sealed by grouting before water is pumped out from inside the cofferdam.

6. The construction method for converting a single-wall cofferdam into a double-wall cofferdam according to claim 5, characterized in that, The specific steps for grouting and sealing the cofferdam before pumping water are as follows: The U-shaped steel plate is installed between two adjacent vertical ribs at the joint, and the U-shaped steel plate, the two vertical ribs and the outer wall plate form a grouting and sealing area; Concrete grout is filled into the grouting sealing area. After the concrete grout has solidified to meet the design requirements, the U-shaped steel plate is retained as part of the joint sealing measures.

7. The construction method for converting a single-wall cofferdam into a double-wall cofferdam according to claim 1, characterized in that, The specific steps for pouring the concrete in the space between the single-walled cofferdam and the outer cofferdam are as follows: The single-walled cofferdam and the outer cofferdam together form a double-walled cofferdam, and a working platform is installed at the top of the double-walled cofferdam. The aggregate hopper is installed on the working platform, and concrete is poured through the aggregate hopper between the single-wall cofferdam and the outer cofferdam.

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