Method for blocking bottom of deepwater steel sheet pile cofferdam

Abstract

The invention discloses a method for blocking the bottom of a deepwater steel sheet pile cofferdam. The method comprises the steps that S1, a cofferdam foundation pit is divided into a steel sheet pile edge and supporting ring beam projection plane area and other areas, and excavation and cleaning are conducted; s2, a plurality of bottom sealing concrete steel bars are manufactured; s3, bottom sealing concrete steel bars are lowered to the corresponding supporting point positions, and bottom sealing concrete is poured underwater; s4, the concrete wall is poured after bottom sealing concrete is equal in strength; s5, after the concrete wall is equal in strength, water in the cofferdam is pumped out, and the formworks and the supporting rods are removed; s6, a pile casing is cut off, a pile head is broken, and secondary bottom sealing and leveling are conducted; and S7, follow-up cofferdam ring beam assembling and disassembling construction and bearing platform pouring construction are conducted. The reinforced concrete bottom sealing mode is adopted, the problems that the excavation depth of the cofferdam cannot reach the designed elevation due to geological reasons, and the bottom sealing thickness needs to be reduced are solved, the steel reinforcement framework is additionally arranged between the steel sheet pile and the pile foundation pile casing for supporting, and the bottom sealing concrete quality is guaranteed; and the problem of easy water seepage of the periphery caused by steel sheet pile guide holes is solved by adopting a bottom sealing concrete wall mode.

Description

Technical Field

[0001] The invention relates to the technical field of cofferdam construction, in particular to a bottom plugging method for a deepwater steel sheet pile cofferdam. Background Art

[0002] In modern bridge construction, it is often necessary to construct abutments on the riverbed of rivers. Since these abutments are located in wading areas, it is impossible to directly construct the abutments. Therefore, cofferdam construction is usually used to solve the abutment construction problem of bridges. With the increasing level of navigation and flood discharge in waterways, the buried depth of bridge abutments is also being designed to be deeper; however, the construction technology of locking steel cofferdams has been continuously broken through, and deep foundation pit steel sheet pile cofferdams have shown obvious superiority. Due to the complexity of the riverbed hydrogeological conditions at the actual location of the bridge, deep foundation pit steel sheet pile cofferdams often encounter some unexpected situations. For example, in some cases, the riverbed geology includes weathered rock layers with high hardness, and the steel sheet piles cannot be normally driven to the designed elevation. It is necessary to change to a hole-driving method for construction. The steel sheet pile hole driving disturbs the original geology, resulting in water seepage around the steel sheet piles. Therefore, the water seepage problem is a technical problem that must be solved for deep-water steel sheet pile cofferdams in this case. On the other hand, due to the high hardness and basically impermeable weathered rock layers, the foundation pit cannot be cleaned to the designed elevation, and the bottom seal thickness needs to be reduced. How to ensure the bottom seal quality after the bottom seal thickness is reduced is also a technical problem that must be solved for the construction of deep-water steel sheet pile cofferdams in this case. Summary of the invention

[0003] In view of the above problems, the present invention provides a method for plugging the bottom of a deepwater steel sheet pile cofferdam, comprising the following steps:

[0004] S1, dividing the cofferdam foundation pit into the steel sheet pile edge and the support ring beam projection surface area and the remaining area, the steel sheet pile edge and the support ring beam projection surface area are excavated and cleaned to a first depth, and the remaining area is excavated and cleaned to a second depth;

[0005] S2, setting a plurality of supporting points between the steel sheet pile and the pile foundation casing, and making a plurality of bottom sealing concrete reinforcements accordingly;

[0006] S3, lowering the bottom concrete reinforcement to the corresponding support point position, and pouring the bottom concrete underwater;

[0007] S4, after the bottom concrete is strengthened, the steel bars, formwork and support rods of the concrete wall are lowered, the pouring points are arranged and the concrete wall is poured;

[0008] S5, draining water from the concrete wall and other strong rear cofferdams, and removing the formwork and support rods;

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

[0010] S7, carry out subsequent conventional installation and disassembly of the cofferdam ring beam and pouring of the foundation.

[0011] As a further explanation of the present invention, the bottom sealing concrete reinforcement is designed according to the on-site working conditions, and during construction, the bottom sealing concrete reinforcement is lowered to its corresponding designed position at a set angle direction.

[0012] Furthermore, the bottom concrete reinforcement includes stirrups and main reinforcements, and the stirrups pass through the main reinforcements and are welded to each other to form an integral component to form the bottom concrete reinforcement.

[0013] Furthermore, before pouring the bottom sealing concrete in step S3, a camera is used to take photos of the periphery of the steel sheet piles and the edge of the pile foundation casing.

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

[0015] Furthermore, in the step S4, the pouring points and the conduit arrangement points are prepared in advance, and the concrete wall is poured by underwater pouring.

[0016] Furthermore, the reinforcement and formwork of the concrete wall are divided into a plurality of sections, which are installed and closed in a combination of sections.

[0017] Furthermore, each side of the concrete wall includes a closing section, and the closing section is located at a hypotenuse position.

[0018] Furthermore, the steps of installing the reinforcement and formwork of the concrete wall include:

[0019] S401, the divers cooperate underwater to install the corner steel bar templates of the two long sides in place as a whole. After installation, the second steel bar is also lowered to the designed position according to the original idea;

[0020] S402, the third and fourth sections of the subsections were assembled on shore, and then lowered to the designed position by divers underwater;

[0021] S403, cutting the excess length of the closing section according to the actual situation on site, firstly let the diver measure the length below, then cut the length on the shore, and then lower the whole to the designed position to close the long side or the short side;

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

[0023] S405, in line with the short side direction, a closing section needs to be set, and the closing section is cut according to the actual length on site;

[0024] S406, arrange the conduits in advance, and then pour the concrete wall according to the conduits.

[0025] The present invention adopts a reinforced concrete bottom sealing method to solve the problem that the excavation depth of the cofferdam cannot reach the designed elevation due to geological reasons, and the thickness of the bottom sealing needs to be reduced. A steel skeleton is added between the steel sheet pile and the pile foundation casing for support to ensure the quality of the bottom sealing concrete. On the other hand, since the steel sheet piles are bored and the holes are drilled, the original geology is disturbed, which makes the surrounding areas of the steel sheet piles prone to water seepage. The present invention adopts a method of setting a bottom sealing concrete wall to solve the problem of water seepage around the steel sheet piles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a flow chart of the bottom plugging method of deepwater steel sheet pile cofferdam according to the present invention;

[0027] Figure 2 This is a schematic diagram of the concrete wall arrangement 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 steel bars and formwork on the long side of a 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 steel bars and formwork on the long side of a concrete wall according to an embodiment of the present invention;

[0030] Figure 5 This is a schematic diagram of the arrangement of the long side closing section of a concrete wall according to an embodiment of the present invention;

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

[0032] Figure 7 This is a schematic diagram of the relative positions of the pouring points, the steel skeleton, and the inner support of the ring beam according to an embodiment of the present invention;

[0033] Figure 8 A diagram showing the arrangement of the bottom concrete pouring conduit and the setting of the pouring points according to an embodiment of the present invention;

[0034] Fig. 9 This is a schematic diagram of the bottom concrete reinforcement structure of an embodiment of the present invention;

[0035] Fig.10 It is a schematic diagram of the top connection between the bottom concrete reinforcement and the pile foundation casing according to an embodiment of the present invention.

[0036] Figure numerals: steel sheet pile 1, supporting ring beam 2, pile foundation casing 3, bottom sealing concrete reinforcement 4, concrete wall 5, crawler crane 6, support rod 7. DETAILED DESCRIPTION

[0037] Example:

[0038] The following is a detailed description of the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments.

[0039] In the description of the present invention, it is necessary to understand that the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0040] like Figure 1 As shown, a method for plugging the bottom of a deepwater steel sheet pile cofferdam comprises the following steps:

[0041] S1, dividing the cofferdam foundation pit into the steel sheet pile edge and the support ring beam projection surface area and the remaining area, the steel sheet pile edge and the support ring beam projection surface area are excavated and cleaned to a first depth, and the remaining area is excavated and cleaned to a second depth;

[0042] S2, setting a plurality of supporting points between the steel sheet pile 1 and the pile foundation casing 3, and making a plurality of bottom sealing concrete steel bars 4 accordingly;

[0043] S3, lowering the bottom concrete reinforcement to the corresponding support point position, and pouring the bottom concrete underwater;

[0044] S4, after the bottom concrete is strengthened, the steel 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, draining water from the concrete wall and other strong rear cofferdams, and removing the formwork and support rods;

[0046] S6, cutting off the casing, breaking the pile head, and secondary bottom sealing and leveling;

[0047] S7, carry out subsequent conventional installation and disassembly of the cofferdam ring beam and pouring of the foundation.

[0048] The present invention adopts a reinforced concrete bottom sealing method to solve the problem that the excavation depth of the cofferdam cannot reach the designed elevation due to geological reasons, and the thickness of the bottom sealing needs to be reduced. A steel skeleton is added between the steel sheet pile and the pile foundation casing for support to ensure the quality of the bottom sealing concrete. On the other hand, since the steel sheet pile holes are inserted and drilled, the original geology is disturbed after the holes are drilled, which makes the surrounding areas of the steel sheet piles prone to water seepage. The present invention specially adopts a method of setting a bottom sealing concrete wall to solve the problem of easy water seepage around the steel sheet pile holes.

[0049] Specifically, in this embodiment, the bottom concrete reinforcement is designed according to the on-site working conditions, and during construction, the bottom concrete reinforcement is lowered to its corresponding designed position at a set angle. In this way, the quality of the bottom concrete can be guaranteed, and a peripheral water stop can be played, thereby reducing the mud wall between the steel sheet pile and the steel casing, and ensuring the quality of the bottom concrete between the steel sheet pile and the bottom concrete, and between the steel casing and the concrete. In practical applications, a truck crane or crawler crane can be used to hoist the steel cage on the shore, and divers can cooperate to lower the bottom concrete reinforcement to the designed position.

[0050] Specifically, the bottom concrete reinforcement of this embodiment includes stirrups and main reinforcement. The stirrups pass through the main reinforcement and are welded to each other to form an integral component to form the bottom concrete reinforcement. The specific processing process is: first, prepare the material in the reinforcement factory according to the design drawings; use a flatbed truck to pull the reinforcement processed by the reinforcement factory to the site, and then process it into an integral component on site; process the bottom concrete reinforcement into a whole according to the design drawings. In actual applications, the main reinforcement can be neatly arranged on the ground according to the angle of the design drawings, and then stirrups are used to pass through the main reinforcement, and then spot welding is performed. See attached. Figure 7 As shown, in this embodiment, the underwater casting of the bottom concrete wall requires the installation of related components such as steel bars, formwork, and support rods underwater, and the materials need to be divided into sections in advance. The bottom concrete steel bars can be lowered by using a car crane or a crawler crane to hoist the steel cage on shore, and then divers cooperate to lower it to the designed position.

[0051] Specifically, in this embodiment, before pouring the bottom concrete in step S3, a camera is used to take pictures of the periphery of the steel sheet piles and the edge of the pile foundation casing.

[0052] Specifically, in this embodiment, during the pouring of the bottom sealing concrete in step S3, the pouring periphery is vibrated using an underwater vibrating rod.

[0053] Specifically, in this embodiment, in step S4, the concrete wall is cast by underwater casting. Since the thickness of the bottom cover of this embodiment is only 78 cm, it is necessary to prepare the casting points, conduit layout points, etc. in advance. For details, see the attached Figure 8As shown, the specific pouring sequence is as follows: Step 1: Use sky pumps 2 and 3 in conjunction with two crawler cranes 6 to shear the ball at point 1# shown in the figure. When the height of the pouring surface near the pile foundation casing is higher than -2.8m, stop pouring (concrete cannot obviously flow out of the casing edge); Step 2: Move the hopper to point 2#, and three sky pumps simultaneously shear the ball at point 2#. When the height of the concrete surface in the 1.5m range nearby reaches -2.4m, re-measure the surrounding area, and after confirming that the difference in the surrounding concrete surface is less than 10cm, continue pouring these points to -2.22m without pulling out the guide tube. Pour point 3# in the same way. Measure the concrete surface of the surrounding areas of points 2 and 3# again, and after confirming that the pouring surface has reached -2.22m (deviation <5cm), move the guide tubes at point 2# and point 3# on the small pile side to points 6 and 7# for arrangement and fixation; Step 3: Sky pump 3 retracts its legs and stops on the shore for standby. Use sky pumps 1 and 2 in conjunction with two crawler cranes to perform ball shearing at point 4# as shown in the figure. When the height of the pouring surface near the pile foundation casing is higher than -2.8m, stop pouring (concrete cannot obviously flow out of the casing edge); Step 4: Move the hopper to point 5#, and two sky pumps will simultaneously perform ball shearing on point 5#. When the height of the concrete surface in the 1.5m range nearby reaches -2.4m, re-measure the surrounding area, and continue pouring these points to -2.22m after confirming that the difference in the surrounding concrete surface is less than 10cm, without pulling out the conduit. Pour points 6 and 7# in the same way; Step 5: Move the hopper to point 8# and close it, re-measure the height of the concrete surface of its accessories, control the bottom of the conduit to be 10cm higher than the concrete surface, and insert the bottom of the conduit to the bottom of the riverbed 5s after ball shearing and continue pouring to -2.22m (not less than -2.4m).

[0054] Specifically, in this embodiment, the steel bars and formwork of the concrete wall are divided into a plurality of sections, which are installed and closed in a combination of sections.

[0055] Specifically, in this embodiment, each side of the concrete wall includes a closing section, and the closing section is located at the hypotenuse position.

[0056] Specifically, the steps of installing the steel bars and formwork of the concrete wall include:

[0057] S401, the divers cooperate underwater to install the corner steel bar templates of the two long sides in place as a whole. After installation, the second steel bar is also lowered to the designed position according to the original idea;

[0058] S402, the third and fourth sections of the subsections were assembled on shore, and then lowered to the designed position by divers underwater;

[0059] S403, cutting the excess length of the closing section according to the actual situation on site, firstly let the diver measure the length below, then cut the length on the shore, and then lower the whole to the designed position to close the long side or the short side;

[0060] S404, using the method steps of steps S401-S403, start to symmetrically lower the concrete wall steel bar template in the short side direction;

[0061] S405, in line with the short side direction, a closing section needs to be set, and the closing section is cut according to the actual length on site;

[0062] S406, arrange the conduits in advance, and then pour the concrete wall according to the conduits.

[0063] In one embodiment of a specific application, during a cofferdam construction process, after the main pier cap cofferdam is cleaned to -3m to -3.5m (strongly weathered rock surface), it is difficult to clean to the designed foundation pit bottom (elevation -4.17m), and some of the slag samples fished out are medium-weathered sandstone with high strength. If the existing cofferdam construction process is used to continue construction, it will bring many construction difficulties and may affect the progress of the project. In order to enable the steel sheet piles to be driven to the set elevation depth, the steel sheet piles are driven by the hole insertion construction, but the hole is disturbed after the hole is drawn, and the problem of easy water seepage around the steel sheet piles is caused. For this reason, the bottom plugging method of the deep-water steel sheet pile cofferdam of the present invention is used to continue construction, and its specific construction process is as follows:

[0064] The cofferdam continues to be excavated until the rock surface at the bottom of the foundation pit is below the elevation of -3.0m (the projection surface of the steel sheet pile edge and the supporting ring beam is controlled to be no less than -3.0m, and the rest of the area is controlled to be no less than -3.5m) and the mud residue around the steel sheet pile and the pile head is cleaned → underwater pouring of 78cm thick bottom concrete (top elevation is -2.22m) to reach the design strength → after the strength is equal, the steel bars, formwork, and support rods of the 1m×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 change B1 version plan. Only because the size of the pedestal is reduced by 25cm, the first section of the pedestal is poured to 2.25m, and the concrete wall is used as a template, so the backfill sand only needs to be 0.75m thick, as follows:

[0065] After reaching the strength, drain the water in the cofferdam, remove the formwork and support rod 7 → cut off the casing, break the pile head, and level the bottom for the second time → install the first layer of the pedestal formwork and formwork support, then tie the steel bars → pour the first layer of pedestal concrete (2.25m) → remove the formwork when the pedestal concrete reaches the design strength → first backfill 0.75m thick with sand, then pour a 50cm thick concrete ring beam around the pedestal → remove the fourth ring beam → install the second section of the formwork and formwork support, then tie the steel bars → pour the second layer of pedestal concrete (3.5m) → backfill 3m thick with sand, then pour a 50cm thick concrete ring beam around the pedestal → pour the pier body out of the water (6m per section, pour two sections) → remove the third layer of ring beam → release the connection between the first and second layer of ring beams → return water to the internal and external water balance → pull out the two diagonal corner piles → remove the first layer of ring beam → lift the second layer of ring beam to +12m and fix it on the steel sheet piles → remove the second layer of ring beam and pull out the remaining steel sheet piles.

[0066] The above only describes the preferred embodiments of the present invention, but it cannot be understood as limiting the claims. The present invention is not limited to the above embodiments, and its specific structure is allowed to be changed. In short, all changes made within the protection scope of the independent claims of the present invention are within the protection scope of the present invention.

Claims

1. A method for plugging the bottom of a deepwater steel sheet pile cofferdam, characterized in that: The following steps are involved: S1, dividing the cofferdam foundation pit into the steel sheet pile edge and the support ring beam projection surface area and the remaining area, the steel sheet pile edge and the support ring beam projection surface area are excavated and cleaned to a first depth, and the remaining area is excavated and cleaned to a second depth; S2, setting a plurality of supporting points between the steel sheet pile and the pile foundation casing, and making a plurality of bottom sealing concrete reinforcements accordingly; S3, lowering the bottom concrete reinforcement to the corresponding support point position, and pouring the bottom concrete underwater; S4, after the bottom concrete is strengthened, the steel bars, formwork and support rods of the concrete wall are lowered, the pouring points are arranged and the concrete wall is poured; S5, draining water from the concrete wall and other strong rear cofferdams, and removing the formwork and support rods; S6, cutting off the casing, breaking the pile head, and secondary bottom sealing and leveling; S7, carry out subsequent conventional installation and disassembly of the cofferdam ring beam and pouring of the foundation.

2. The bottom plugging method of deepwater steel sheet pile cofferdam according to claim 1 is characterized by: The bottom sealing concrete reinforcement is designed according to the on-site working conditions, and during construction, the bottom sealing concrete reinforcement is lowered to its corresponding designed position according to a set angle direction.

3. The bottom plugging method of deepwater steel sheet pile cofferdam according to claim 2 is characterized by: The bottom-sealed concrete reinforcement includes stirrups and main reinforcements. The stirrups pass through the main reinforcements and are welded to each other to form an integral component to form the bottom-sealed concrete reinforcement.

4. The bottom plugging method of deepwater steel sheet pile cofferdam according to claim 2 is characterized in that: In the step S3, before pouring the bottom sealing concrete, a camera is used to take photos of the periphery of the steel sheet piles and the edge of the pile foundation casing.

5. The bottom plugging method of deepwater steel sheet pile cofferdam according to claim 2 is characterized by: During the pouring of the bottom sealing concrete in step S3, the pouring periphery is vibrated using an underwater vibrating rod.

6. The bottom plugging method of deepwater steel sheet pile cofferdam according to claim 2 is characterized by: In the step S4, the pouring points and the conduit arrangement points are prepared in advance, and the concrete wall is poured by underwater pouring.

7. The bottom plugging method of deepwater steel sheet pile cofferdam according to claim 6 is characterized by: The steel bars and formwork of the concrete wall are divided into a plurality of sections, which are installed and closed in a section-by-section combination.

8. The method for plugging the bottom of a deepwater steel sheet pile cofferdam according to claim 7, characterized in that: Each side of the concrete wall includes a closing section, and the closing section is located at a hypotenuse position.

9. The method for plugging the bottom of a deepwater steel sheet pile cofferdam according to claim 8, characterized in that: The steps of installing the reinforcement and formwork of the concrete wall include: S401, the divers cooperate underwater to install the corner steel bar templates of the two long sides in place as a whole. After installation, the second steel bar is also lowered to the designed position according to the original idea; S402, the third and fourth sections of the subsections were assembled on shore, and then lowered to the designed position by divers underwater; S403, cutting the excess length of the closing section according to the actual situation on site, firstly let the diver measure the length below, then cut the length on the shore, and then put the whole thing down to the designed position to close the long side or the short side; S404, using the method steps of steps S401-S403, start to symmetrically lower the concrete wall steel bar template in the short side direction; S405, in line with the short side direction, a closing section needs to be set, and the closing section is cut according to the actual length on site; S406, arrange the conduits in advance, and then pour the concrete wall according to the conduits.

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