Deep water steel sheet pile cofferdam bottom sealing method

Abstract

The application discloses a deep-water steel sheet pile cofferdam bottom sealing method, which comprises the following steps: S1, the cofferdam foundation pit is divided into a steel sheet pile side and a support ring beam projection area and the rest of the area, and excavation and cleaning are carried out; S2, a plurality of bottom sealing concrete steels are made; S3, the bottom sealing concrete steels are lowered to corresponding support point positions to carry out underwater pouring of bottom sealing concrete; S4, after the bottom sealing concrete is cured, a concrete wall is poured; S5, after the concrete wall is cured, water in the cofferdam is pumped out, and a formwork and a support rod are removed; S6, a pile casing is cut off, a pile head is broken, and secondary bottom sealing and leveling are carried out; and S7, subsequent cofferdam ring beam mounting and dismounting construction and pile cap pouring construction are carried out. The application adopts a reinforced concrete bottom sealing mode, solves the problem that the cofferdam excavation depth cannot reach the design elevation due to geological reasons and the thickness of the bottom sealing needs to be reduced, adds a steel framework between the steel sheet pile and the pile foundation casing to support and guarantee the quality of the bottom sealing concrete, and solves the problem that the steel sheet pile hole leads to easy water seepage around the periphery by adopting a bottom sealing concrete wall mode.

Description

TECHNICAL FIELD

[0001] The present application relates to the construction technology field of cofferdam, in particular to a deep water steel sheet pile cofferdam bottom sealing method. BACKGROUND

[0002] In modern bridge engineering construction, it is often necessary to carry out pile cap construction on the riverbed of the river channel. Since the position of these pile caps is in the wading area, direct pile cap construction is not possible, so the cofferdam construction method is usually used to solve the problem of bridge pile cap construction. With the increasing level of waterway navigation and river flood discharge, the design of bridge pile cap depth is also becoming deeper; however, the construction technology of lock steel cofferdam continues to break through, and the deep foundation pit steel sheet pile cofferdam shows obvious advantages. Due to the complexity of the riverbed hydrogeological conditions of the actual position of the bridge, the deep foundation pit steel sheet pile cofferdam often encounters some unexpected situations, for example, in some cases, the riverbed geology contains weathered rock layers, the weathered rock layers have high hardness, and the steel sheet pile cannot be normally inserted to the design elevation position, and needs to be changed to use the hole insertion method for construction. Since the steel sheet pile hole insertion hole disturbs the original geology, it is easy to cause water seepage around the steel sheet pile, so this water seepage problem is a technical problem that must be solved for deep water steel sheet pile cofferdam in this case. On the other hand, due to the high hardness and basically impermeable nature of the weathered rock layer, the foundation pit cannot be cleaned to the design elevation, and the bottom sealing thickness needs to be reduced. How to ensure the quality of the bottom sealing after reducing the bottom sealing thickness is also a technical problem that must be solved for deep water steel sheet pile cofferdam construction in this case. SUMMARY

[0003] The present application provides a deep water steel sheet pile cofferdam bottom sealing method to solve the above problems, comprising the following steps:

[0004] S1, divide the cofferdam foundation pit into a steel sheet pile side and a support ring beam projection area and the rest of the area, excavate and clean the steel sheet pile side and the support ring beam projection area to a first depth, and excavate and clean the rest of the area to a second depth;

[0005] S2, a plurality of support points are provided between the steel sheet pile and the pile foundation casing, and a plurality of bottom sealing concrete reinforcements are correspondingly made;

[0006] S3, the bottom sealing concrete reinforcements are lowered to the corresponding support point positions, and underwater pouring of bottom sealing concrete is carried out;

[0007] S4, after the bottom sealing concrete is cured, the steel reinforcement, formwork and support rod of the concrete wall are lowered, and the pouring point and the pouring of the concrete wall are arranged;

[0008] S5, after the concrete wall is cured, the water in the cofferdam is pumped out, and the formwork and support rod are removed;

[0009] S6, the casing, pile breaking head and secondary bottom sealing are cut off;

[0010] S7, performing subsequent conventional cofferdam ring beam construction and pouring construction of the pile cap.

[0011] As a further illustration of the present application, the bottom sealing concrete reinforcement is designed according to the site conditions, and during construction, the bottom sealing concrete reinforcement is lowered to the corresponding design position according to the set angle direction.

[0012] Further, the bottom sealing concrete reinforcement includes stirrups and main reinforcement, and the stirrups are welded together after penetrating the main reinforcement to form the bottom sealing concrete reinforcement.

[0013] Further, the step S3 includes photographing the periphery of the steel sheet pile and the pile foundation sleeve edge using a camera before pouring the bottom sealing concrete.

[0014] Further, during the pouring of the bottom sealing concrete in step S3, the pouring periphery is vibrated using an underwater vibrating rod.

[0015] Further, in step S4, the pouring point and the guide pipe arrangement point are prepared in advance, and the concrete wall is poured using an underwater pouring method.

[0016] Further, the reinforcement and formwork of the concrete wall are divided into several segments, and are installed and closed by segment combination.

[0017] Further, each side of the concrete wall includes a closing segment, and the closing segment is located at the oblique edge position.

[0018] Further, the reinforcement and formwork installation steps of the concrete wall include:

[0019] S401, the diver first installs the corner reinforcement formwork of the two long sides in place, and after installation, the second block reinforcement is also lowered to the design position according to the original idea;

[0020] S402, the third and fourth blocks are assembled on the shore according to the segment, and then lowered to the design position by the diver;

[0021] S403, according to the actual situation on site, the closing segment is cut to the excess length, first, the diver measures the length underwater, then cuts the length on the shore, and then lowers the whole to the design position for long side closing or short side closing;

[0022] S404, using the method steps of steps S401-S403, start to lower the concrete wall reinforcement formwork in the short side direction symmetrically;

[0023] S405, in the same direction as the short side, requires a closure section, which is cut according to the actual length on site;

[0024] S406, the conduit is laid out in advance, and then the concrete wall is poured according to the conduit.

[0025] This invention solves the problem of reducing the bottom sealing thickness when the cofferdam excavation depth cannot reach the design elevation due to geological reasons by using reinforced concrete bottom sealing. A steel reinforcement skeleton is added between the sheet piles and the pile foundation casing for support to ensure the quality of the bottom sealing concrete. On the other hand, the drilling of the sheet pile pilot holes disturbs the original geology, making the area around the sheet piles prone to water seepage. This invention solves the problem of water seepage around the area caused by the sheet pile pilot holes by setting up a bottom sealing concrete wall. Attached Figure Description

[0026] Figure 1 This is a flowchart of the deep-water steel sheet pile cofferdam bottom sealing method of the present invention;

[0027] Figure 2 This is a schematic diagram of the concrete wall setup according to an embodiment of the present invention;

[0028] Figure 3 This is a schematic diagram of the installation of the first and second sections of reinforcing bars and formwork on the long side of the concrete wall according to an embodiment of the present invention;

[0029] Figure 4 This is a schematic diagram of the installation of the third and fourth sections of reinforcing bars and formwork on the long side of the concrete wall in an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram illustrating the setting of the long side closure section of the concrete wall in an embodiment of the present invention;

[0031] Figure 6 This is a schematic diagram illustrating the short-side closure section of the concrete wall according to an embodiment of the present invention;

[0032] Figure 7 This is a schematic diagram showing the relative positions of the pouring points, the reinforcing steel cage, and the inner supports of the ring beam in an embodiment of the present invention.

[0033] Figure 8 This is a diagram showing the arrangement of the bottom sealing concrete pouring conduit and the setting of the pouring points in an embodiment of the present invention;

[0034] Figure 9 This is a schematic diagram of the bottom-sealing concrete reinforcement structure according to an embodiment of the present invention;

[0035] Figure 10 This is a schematic diagram of the connection between the bottom sealing concrete reinforcement and the top of the pile foundation casing in an embodiment of the present invention.

[0036] Attached reference numerals: 1. Sheet pile; 2. Support ring beam; 3. Pile foundation casing; 4. Bottom sealing concrete reinforcement; 5. Concrete wall; 6. Crawler crane; 7. Support rod. Detailed Implementation

[0037] Example:

[0038] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0039] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not 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.

[0040] like Figure 1 As shown, a method for sealing the bottom of a deep-water steel sheet pile cofferdam includes the following steps:

[0041] S1, the cofferdam foundation pit is divided into the area of ​​the steel sheet pile edge and the projection surface of the supporting ring beam and the remaining area. The area of ​​the steel sheet pile edge and the projection surface of the supporting ring beam is excavated and cleaned to the first depth, and the remaining area is excavated and cleaned to the second depth.

[0042] S2, Several support points are set between the steel sheet pile 1 and the pile foundation casing 3, and several bottom sealing concrete reinforcement bars 4 are made accordingly;

[0043] S3, lower the bottom sealing concrete reinforcement to the corresponding support point position and pour the bottom sealing concrete underwater;

[0044] S4, after the bottom sealing concrete has reached the required strength, the reinforcing bars, formwork, and support rods of the concrete wall 5 are lowered, the pouring points are arranged, and the concrete wall is poured.

[0045] S5, after the concrete wall is reinforced, the water inside the cofferdam is drained, and the formwork and support rods are removed;

[0046] S6, cut off the casing, break the pile head, and perform secondary sealing and leveling;

[0047] S7, proceed with the subsequent routine installation and dismantling of the cofferdam ring beam and the pouring of the foundation.

[0048] This invention addresses the problem of insufficient cofferdam excavation depth due to geological reasons, necessitating a reduction in the sealing thickness, by employing reinforced concrete sealing. A steel reinforcement frame is added between the sheet piles and the pile casing to ensure the quality of the sealing concrete. Furthermore, the drilling of sheet pile pilot holes disrupts the original geological conditions, leading to water seepage around the sheet piles. This invention specifically addresses this issue by installing a sealing concrete wall to prevent water seepage around the sheet pile pilot holes.

[0049] Specifically, in this embodiment, the bottom sealing concrete reinforcement is designed according to the site conditions. During construction, the bottom sealing concrete reinforcement is lowered to its corresponding designed position at a predetermined angle. This ensures the quality of the bottom sealing concrete, acts as a perimeter waterproofing layer, reduces the mud wall between the sheet pile and the steel casing, and ensures the quality of the bottom sealing concrete between the sheet pile and the bottom sealing concrete, and between the steel casing and the concrete. In practical applications, a truck crane or crawler crane can be used to hoist the reinforcement cage on shore, and divers can then lower the bottom sealing concrete reinforcement to the designed position.

[0050] Specifically, the bottom-sealing concrete reinforcement in this embodiment includes stirrups and main reinforcement bars. The stirrups pass through the main reinforcement bars and are then welded together to form an integral component, thus forming the bottom-sealing concrete reinforcement. The specific processing procedure is as follows: first, the steel bars are cut at the steel mill according to the design drawings; the steel bars processed at the mill are transported to the site using a flatbed truck and then processed into an integral component on-site; finally, the bottom-sealing concrete reinforcement is processed into an integral component according to the design drawings. In practical applications, the main reinforcement bars can be neatly arranged on the ground according to the angles shown in the design drawings, and then stirrups are passed through the main reinforcement bars before spot welding. See Appendix. Figure 7 As shown in this embodiment, underwater pouring of the bottom sealing concrete wall requires the installation of related components such as steel bars, formwork, and support rods underwater. The materials need to be divided into sections in advance. The bottom sealing concrete steel bars can be lowered by using a truck crane or crawler crane to hoist the steel cage on the shore, and then divers can cooperate to lower it to the design position.

[0051] Specifically, in this embodiment, before pouring the bottom sealing concrete in step S3, the perimeter of the sheet pile and the edge of the pile foundation casing are photographed using a camera.

[0052] Specifically, in this embodiment, during the pouring of the bottom sealing concrete in step S3, an underwater vibrator is used to vibrate the surrounding area.

[0053] Specifically, in this embodiment, in step S4, the concrete wall is poured underwater. Since the bottom sealing thickness in this embodiment is only 78cm, the pouring points, guide pipe placement points, etc., need to be planned in advance; see appendix for details. Figure 8As shown, the specific pouring sequence is as follows: Step 1: Using overhead pumps 2 and 3 in conjunction with two crawler cranes 6, the concrete is sheared at point 1#. Pouring stops when the height of the concrete surface near the pile casing is higher than -2.8m (the concrete should not visibly flow out of the casing edge); Step 2: The hopper is moved to point 2#, and the three overhead pumps simultaneously shear the concrete at point 2#. When the concrete surface height within 1.5m of point 2# reaches -2.4m, the surrounding area is re-measured. After confirming that the difference in the surrounding concrete surface is less than 10cm, the pouring continues at these points to -2.22m, without removing the guide pipe. Point 3# is poured in the same way. The concrete surface near points 2# and 3# is then measured. After confirming that the pouring surface has reached -2.22m (deviation <5cm), the guide pipes for points 2# and 3# on the side of the smaller pile number are moved to points 6# and 7# for placement and fixation; Step 3: Overhead pump 3 is retracted and parked on the bank for standby. Using two overhead pumps (1 and 2) and two crawler cranes, the concrete was sheared at point 4 (shown in the diagram). Pouring was stopped when the concrete level near the pile casing edge was higher than -2.8m (concrete should not visibly overflow the casing edge). Fourth step: The hopper was moved to point 5, and both overhead pumps simultaneously sheared the concrete at point 5. When the concrete level within a 1.5m radius reached -2.4m, the surrounding area was re-measured. After confirming the difference in concrete level was less than 10cm, pouring continued at these points to -2.22m, without removing the guide pipe. Points 6 and 7 were poured in the same manner. Fifth step: The hopper was moved to point 8 and closed. The concrete level near the hopper was re-measured, ensuring the bottom of the guide pipe was 10cm higher than the concrete level. Five seconds after shearing, the bottom of the guide pipe was inserted to the riverbed bottom, and pouring continued to -2.22m (not lower than -2.4m).

[0054] Specifically, in this embodiment, the steel reinforcement and formwork of the concrete wall are divided into several sections, which are assembled and joined together using a section combination method.

[0055] Specifically, in this embodiment, each side of the concrete wall includes a closing section, which is located on the inclined side.

[0056] Specifically, the installation steps for the reinforcing steel and formwork of the concrete wall include:

[0057] S401, with the help of divers underwater, the corner steel reinforcement formwork of the two long sides is first installed in place. After installation, the second steel reinforcement is also lowered to the design position according to the original plan.

[0058] S402 was assembled on shore according to the third and fourth sections, and then lowered to the designed position by divers in underwater coordination.

[0059] S403, according to the actual situation on site, the excess length of the merging section is cut off. First, the diver must measure the length below, and then the length is cut on the shore. Then the whole section is lowered to the design position for merging the long side or the short side.

[0060] S404, using the methods and steps of S401-S403, begin symmetrically lowering the concrete wall reinforcement formwork in the short side direction;

[0061] S405, in the same direction as the short side, requires a closure section, which is cut according to the actual length on site;

[0062] S406, the conduit is laid out in advance, and then the concrete wall is poured according to the conduit.

[0063] In one specific application embodiment, during the construction of a cofferdam, after clearing the main pier foundation cofferdam to -3m to -3.5m (strongly weathered rock surface), it became difficult to clear it to the bottom of the designed foundation pit (elevation -4.17m). Furthermore, some of the dredged material was moderately weathered sandstone with high strength. Continuing construction using existing cofferdam construction techniques would present numerous difficulties and potentially affect the project's progress. To ensure the sheet piles could be driven to the designated depth, pilot-drilling was employed. However, this disrupted the original geological conditions and led to water seepage around the sheet piles. Therefore, the deep-water sheet pile cofferdam bottom sealing method described above is used to continue construction. The specific construction process is as follows:

[0064] The cofferdam excavation continues to the bottom of the foundation pit, down to a rock surface elevation of -3.0m (the projected surface of the sheet piles and supporting ring beams is controlled at no less than -3.0m, and the rest of the area is controlled at no less than -3.5m). Mud and debris around the sheet piles and pile heads are cleared. A 78cm thick bottom-sealing concrete layer is poured underwater (top elevation at -2.22m) to reach the design strength. After reaching the required strength, the reinforcing steel, formwork, and support rods for the 1m x 1m concrete wall are lowered underwater in sections. The pouring points are arranged, and the concrete is poured. The subsequent process is consistent with the revised B1 version, except that the foundation size is reduced by 25cm. The first section of the foundation is poured to a depth of 2.25m, using the concrete wall as formwork. Therefore, only a 0.75m thick backfill sand layer is needed, as detailed below:

[0065] After the cofferdam is leveled, the water is pumped out, and the formwork and support rods are removed. The casing is cut, the pile heads are broken, and the bottom is sealed and leveled a second time. The first layer of foundation formwork and support is installed, and the reinforcing steel is tied. The first layer of foundation concrete (2.25m) is poured. Once the foundation concrete reaches the design strength, the formwork is removed. A 0.75m thick layer of sand is backfilled, and then a 50cm thick concrete ring beam is poured around the foundation. The fourth ring beam is removed. The second section of formwork and support is installed, and the reinforcing steel is tied. The second layer of foundation concrete (3.5m) is poured. A 3m thick layer of sand is backfilled, and then a 50cm thick concrete ring beam is poured around the foundation. The pier body is poured above the water surface (6m sections, two sections are poured). The third ring beam is removed. The connection between the first and second ring beams is disconnected. Water is returned to the internal and external water balance. Two diagonal piles are removed. The first ring beam is removed. The second ring beam is lifted to +12m and fixed to the sheet piles. The second ring beam is removed, and the remaining sheet piles are pulled out.

[0066] The above description only illustrates preferred embodiments of the present invention and should not be construed as limiting the scope of the claims. The present invention is not limited to the above embodiments, and variations in its specific structure are permitted. In short, all variations made within the scope of the independent claims of the present invention are within the scope of protection of the present invention.

Claims

1. A method for sealing the bottom of a deep-water steel sheet pile cofferdam, characterized in that, Includes the following steps: S1, the cofferdam foundation pit is divided into the area of ​​the steel sheet pile edge and the projection surface of the supporting ring beam and the remaining area. The area of ​​the steel sheet pile edge and the projection surface of the supporting ring beam is excavated and cleaned to the first depth, and the remaining area is excavated and cleaned to the second depth. S2, Several support points are set between the steel sheet pile and the pile foundation casing, and several bottom sealing concrete reinforcements are made accordingly; S3, lower the bottom sealing concrete reinforcement to the corresponding support point position and pour the bottom sealing concrete underwater; S4, after the bottom concrete has reached the required strength, lower the reinforcing bars, formwork, and support rods of the concrete wall, arrange the pouring points, and pour the concrete wall. S5, after the concrete wall is reinforced, the water inside the cofferdam is drained, and the formwork and support rods are removed; S6, cut off the casing, break the pile head, and perform secondary sealing and leveling; S7, proceed with the subsequent routine installation and dismantling of the cofferdam ring beam and the pouring of the foundation.

2. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 1, characterized in that: The bottom sealing concrete reinforcement is designed according to the site conditions. During construction, the bottom sealing concrete reinforcement is lowered to its corresponding design position according to the set angle and direction.

3. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 2, characterized in that: The bottom sealing concrete reinforcement includes stirrups and main bars. The stirrups pass through the main bars and are welded together to form an integral component to form the bottom sealing concrete reinforcement.

4. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 2, characterized in that: Before pouring the sealing concrete in step S3, the perimeter of the sheet pile and the edge of the pile foundation casing are photographed using a camera.

5. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 2, characterized in that: During the pouring of the sealing concrete in step S3, underwater vibrators are used to vibrate the surrounding area.

6. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 2, characterized in that: In step S4, the pouring points and conduit placement points are prepared in advance, and the concrete wall is poured using an underwater pouring method.

7. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 6, characterized in that: The steel reinforcement and formwork of the concrete wall are divided into several sections, which are assembled and joined together using a section combination method.

8. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 7, characterized in that: Each side of the concrete wall includes a closure segment located at an inclined position.

9. The method for sealing the bottom of a deep-water steel sheet pile cofferdam according to claim 8, characterized in that: The steps for installing the reinforcement and formwork of the concrete wall include: S401, with the help of divers underwater, the corner steel reinforcement formwork of the two long sides is first installed in place. After installation, the second steel reinforcement is also lowered to the design position according to the original plan. S402 was assembled on shore according to the third and fourth sections, and then lowered to the designed position by divers in underwater coordination. S403, according to the actual situation on site, the excess length of the merging section is cut off. First, the diver must measure the length below, and then the length is cut on the shore. Then the whole section is lowered to the design position for merging the long side or the short side. S404, using the methods and steps of S401-S403, begin symmetrically lowering the concrete wall reinforcement formwork in the short side direction; S405, in the same direction as the short side, requires a closure section, which is cut according to the actual length on site; S406, the conduit is laid out in advance, and then the concrete wall is poured according to the conduit.

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