CN101245603B - Floating arch cofferdam and its construction method - Google Patents

Abstract

The invention provides a float arch cofferdam which can float and submerge in water as well as is convenient for being dragged and can be used for a plurality of times. The invention also provides the construction method of the float arch cofferdam. The float arch cofferdam is mainly used for maintaining and rebuilding various large dams and water conservancy projects, which can be utilized to surround the upstream face of the large dam, keeps off the water in a reservoir and discharge the downstream water of a cofferdam; dry operating environment is created on the upstream face of the large dam; the cofferdam is made by adopting steel plates and reinforced concrete material, the shape of the circle arch cofferdam lead the outer wall to bear upstream water pressure, but the outer wall does not need to be too thick, and due to the design of more than two cabins on the transverse surface, the posture of the cofferdam in the water can be more flexibly adjusted by controlling the water injection and water draining in all the cabins when in floating. The construction of the cofferdam can be carried out on the water, but a foundation bed is sealed with the main body of the cofferdam to stop water so as to collect the sewage generated in the construction; after the construction, the sewage is discharged after being purified and treated, thus reducing pollution to water quality. In addition, when in construction, the reservoir does not need emptying and only needs to lower the water level properly, thereby avoiding the loss caused by emptying the reservoir.

Description

Floating arch cofferdam and its construction method

technical field

The invention relates to a water conservancy cofferdam, and in particular provides a floating arch cofferdam which can be floated and sunk in water, is convenient to move, and can be used multiple times and its construction method.

Background technique

"The Seventeenth International Conference on Large Dams" provides a kind of semi-circular steel cylinder floating cofferdam 1 with a diameter of 2.75 meters as shown in Figure 1 used in the repair of Mactaquac Power Station in Canada and its The construction method is that it is made of thin steel plates, and the interior is reinforced with steel plates. A grouting bag 2 is installed on both ends of the cofferdam 1. When the cofferdam and the dam are aligned, concrete is poured into the grouting bag to stop water, and then use the surrounding The water pump 4 at the bottom of the weir pumps out the water between the cofferdam and the dam 3 to form a dry work construction area. The cofferdam is welded and formed on the shore.

Another kind of floating reinforced concrete cofferdam 5 shown in Figure 2 used in the U.S. General Joseph Dam Elevation Project adopts a concave shape structure, and the interior is divided into 20 cabins, which are interconnected with pipelines. The floating cofferdam is constructed in a dry dock. When pouring concrete, it lies flat on the bottom of the dry dock. The dry dock is located on the beach beside the reservoir. The horizontal dike between the dry dock and the reservoir protects the construction site of the floating cofferdam. After the construction is completed, the embankment is broken and water is released to fill the dry dock, so as to float and transport the built cofferdam structure. First use the tugboat to drag the floating cofferdam into the reservoir, and after arriving at the designated place, carry out selective subsidence work on each ballast of the cofferdam to erect the cofferdam. Then it is dragged to the vicinity of the dam by a tugboat, positioned by a tugboat, a winch, and a boom, and clings to the dam. Utilize the rubber water stop on the J-shaped side support 6, and then pump the water between the cofferdam and the dam to form a dry work construction area.

Although the first type of steel cylinder cofferdam has the advantages of convenient installation, less underwater operations, and multiple uses, but because it is welded by all steel materials, this type of cofferdam will show its rigidity when the span is large Not enough, easy deformation and engineering difficulty, and many disadvantages such as high cost.

Another kind of concave concrete cofferdam, there is a row of 20 cabins in the reinforced concrete cofferdam. Because it adopts a concave shape structure, the front of the cofferdam must be able to bear strong water pressure, so the thickness of the reinforced concrete There are high requirements for quality and quality, and because the 20 cabins used to control the attitude of the cofferdam are distributed in a single row during hauling in water, the cofferdam is easy to roll over during hauling, and it takes a lot of time to adjust the cofferdam when installing at the next location However, there are still many disadvantages such as high engineering difficulty and high cost.

In addition, neither of the above two cofferdams involves the treatment of underwater foundations, and their application range is relatively limited.

Contents of the invention

In order to solve the above-mentioned problems existing in the prior art, the present invention provides a floating arch cofferdam and its construction method.

Floating arch cofferdam, made of steel plate and reinforced concrete, has a cabin inside and adopts a circular arch shape structure. It is divided into several layers in the height direction, and each layer is divided into several sections in the horizontal direction. Each section is from the inner arc of the arch to the arch. There are at least two cabins distributed in the outer arc direction, and the cabins are not connected to each other. Each cabin is connected to the control switch and the water pump through the pipeline, and the water pump is connected to the outside of the cofferdam. The floating state and equilibrium state of the arch cofferdam can be adjusted by filling and draining.

The thickness of the upstream surface of the arch cofferdam is constant or gradually thickens with the water depth, and the downstream surface of the arch cofferdam is gradually thickened, constant or stepped. It also includes the base at the bottom of the floating arched cofferdam, the base is an arched shell structure with an open top surface, the concrete main body of the cofferdam is placed in the shell, and the bottom of the base has two arched steel Blade foot, the steel blade foot is flush with the outside of the cofferdam, the lower edge of the two steel blade feet is a small acute angle inward, and the two steel blade feet form a water-stop room, and the top of the water-stop room is provided with a grouting pipe connected to the Cofferdam pre. After the two steel blade feet are pierced into the river bed, the space between the arch cofferdam and the river bed can be poured with underwater non-dispersible concrete through the preset steel pipe for water stop treatment.

The two ends of the arch cofferdam and the junction of the dam are provided with abutments, and the dam contact surface of the abutments is consistent with the shape of the dam, and a soft mold bag is installed, and the junction surface of the abutment and the arch cofferdam is also provided with a soft mold bag. The soft mold bag is connected with a pouring pipe leading to the crest of the weir.

The construction method of the floating arch cofferdam comprises the following steps:

1. Remove sundries at the bottom and level the foundation: Large dredgers are used to excavate the covering layer and foundation pit to level the foundation. If there is a prominent uneven rock surface, blast it in the water at a fixed elevation before excavating.

2. Assemble the floating platform and gantry-shaped lifting tower on the water surface: assemble the floating platform on the water surface where the cofferdam needs to be set up. There are several gate-shaped lifting towers, which are fixed on the floating platform and can be lifted and lowered to form steel molds with hooks.

3. Assemble the base of the cofferdam and the outer formwork plate in the work area: the base customized in the factory will be assembled in the work area, the outer formwork plate and the base will be sealed and connected to form a box structure, and the door-shaped lifting tower will be used to lift the The base and the outer mold are continuously lowered into the water to reduce the load gravity of the floating platform.

4. Bundling of steel bars and pouring concrete: the outer wall of the arch cofferdam and the steel bars in the partition are bound and formed on special molds, and then hoisted into the mold separately, and plastic pads are set to ensure the thickness of the concrete protective layer outside the steel bars. Then install the inner mold steel plate, the inner mold steel plate is a hydraulic segmented structure. The demolition adopts the shrinkage method, and the hoist is used to pull out the concrete. The concrete is poured in layers. After the concrete of the lower layer reaches 80% of the design strength, the upper layer of concrete is poured. Water, always keep the buoyancy of the cofferdam and the pulling force of the hook greater than the weight of the transfer weir.

5. The arch cofferdam is in place and the water is sealed and the dry work area is completed: Prefabricate the arch seats at both ends of the arch cofferdam on the ground. C ₃₀ first grade concrete is poured into the soft mold bags on both sides, and plasticizer and early strength agent are mixed in. The arch cofferdam and abutment are close to the dam by hoist and rope, and the arch cofferdam base edge is also passed through the grouting pipe. Concrete is poured into the water stop between the feet to seal the water at the bottom of the cofferdam, and finally the water in the space between the cofferdam and the dam is drained from the top of the cofferdam to complete the dry work area.

The beneficial effects of the present invention are: the cofferdam is made of reinforced concrete, the shape of the arched cofferdam enables the outer wall of the cofferdam to withstand the upstream water pressure without being too thick, and the design of more than two cabins on the transverse plane can pass through the Control the water injection and drainage of each cabin, adjust the posture of the cofferdam in the water more flexibly, prevent rollover and make the alignment faster. Although the cofferdam construction is carried out on the water, the base and the outer formwork steel plate have been sealed before pouring. The sewage generated during construction can be collected, and after the construction is completed, the sewage is purified and treated before being discharged, which can reduce water pollution. There is no need to empty the reservoir during construction, but only need to lower the water level appropriately, so as to avoid the loss of economic and social benefits caused by emptying the reservoir.

Description of drawings

Fig. 1 is a schematic structural diagram of one of the existing cofferdams.

Fig. 2 is the structural diagram of the second existing cofferdam.

Fig. 3 is a schematic diagram of the overall structure of the floating arch cofferdam of the present invention.

Fig. 4 is a three-dimensional exploded schematic diagram of the present invention.

Figures 5a-c are schematic diagrams of the vertical section structure of the floating arch cofferdam of the present invention.

Fig. 6 is a sectional view of cabin A-A of the present invention.

Fig. 7 is a cross-sectional view of the waterproof room of the base of the present invention.

Figure 8a-b is a step-by-step diagram of construction on the floating platform of the present invention.

in:

1 Existing steel cylinder cofferdam 2 Grouting package 3 Dam

4 Water pump 5 Existing concrete weir 6 Concrete weir side support

7 floating arch cofferdam 8 working area 9 cabins

71 outer wall 72 partition 10 abutment

11 Base 12 Steel blade foot 13 Grouting pipe

14 outer formwork steel plate 15 inner formwork steel plate 16 bagged concrete

17 River bed 23 Operation area 19 Floating platform

20 door-shaped lifting tower 21 water 22 water-stop

Detailed ways

As shown in Fig. 3 and Fig. 4, the floating arch cofferdam 7 of the present invention is made of steel plates and reinforced concrete materials, the main body can adopt ordinary concrete, and the outer layer is an outer formwork steel plate made of thin steel plates; The water pressure varies with the water depth, so from a structural point of view, the width and thickness of the arch cofferdam can vary with the water depth. Generally, it can gradually become smaller from deep to shallow. As shown in Figure 5a and Figure 5b, the thickness of the upstream surface of the arch cofferdam remains constant with the water depth, and the thickness of the downstream surface of the arch cofferdam is gradually thickened, constant or stepped with the water depth. The surface can also gradually thicken with water depth like the downstream surface. However, considering the construction process and the use of the internal cabin 9, the vertical section should be selected to have the same width up and down as shown in Figure 5c, but the thickness of the outer wall 71 gradually becomes thicker with the water depth from shallow to deep.

As shown in Figure 3, Figure 4, and Figure 6, the concrete main body is divided into several layers in the height direction, and the height of each layer is generally 1-3 meters. The thickness of the partition 72 and the outer wall 71 should be 200-500 mm. The horizontal direction is divided into 6-10 sections, and at least two compartments 9 are distributed from the inner arc of the arch to the outer arc of the arch in each section. The compartments 9 are not connected to each other, and each compartment 9 is connected to a control switch and a water pump through a pipeline. The water pump communicates with the outside of the cofferdam. The subsidence and floating of the cofferdam and the adjustment of the balance posture in the water are realized by injecting water and draining water into each compartment 9 through the water pump.

In addition, external prestressed cables are arranged along the tangent point of the outer circle of the cofferdam. The external prestressed cables are made of high-strength and low-relaxation steel strands, and the steel strands are covered with epoxy resin coating. layer of high density polyethylene sheath.

As shown in Figure 7, a base 11 is installed at the bottom of the floating arched cofferdam. The base 11 is an arched shell structure with an open top surface, and the concrete main body of the cofferdam is placed in the shell. Water-tight, the base 11 has two arched steel blade feet 12 on the bottom surface, the steel blade feet 12 are flush with the outer side of the cofferdam, similar to the skirt of the cofferdam, and the lower sides of the two steel blade feet 12 face inward It is a small and acute angle, and the height of the blade foot is 1.0-1.5m. The steel plate needs to be thickened to 15-20mm within the height range of about 0.5m at the blade tip, and the interior needs to be filled with C50 fine stone concrete. After the two steel blade feet 12 are inserted into the riverbed 17, a water stop 22 is formed in the middle. The top of the water stop 22 is provided with a grouting pipe 13 connected to the top of the cofferdam. Buried steel pipes with a spacing of 1-3 meters. The arched cofferdam has a large plane size and is in the shape of a thin circular arc on the plane. Generally speaking, the bottom of the riverbed 17 is always uneven. There is still a height difference of plus or minus 0.5m in the inner foundation, and it is also possible that individual parts may be supported by protruding rocks. Therefore, the effect of accidental factors on the bottom arch cofferdam should be considered, and stiffening should be set on the back of the steel blade foot 12 The beam bears the supporting force and gravity, so that the bottom of the arch cofferdam will not be damaged. At the same time, the stiffening beam should have a certain rigidity, which can ensure the overall shape of the arch cofferdam during construction. In fact, the stiffening beam is a part of the concrete or steel formwork at the bottom of the arch cofferdam, which can meet the strength and stiffness required by the load during the construction of the lower arch cofferdam.

The two ends of the arch cofferdam and the junction of the dam 3 are provided with an abutment 10, and the contact surface between the abutment 10 and the dam 3 is combined with the shape of the dam 3 and a soft mold bag is installed. Because the power generation diversion dam section, overflow dam section and The upstream dam surface of the retaining dam section is not a vertical smooth plane, and the two arch ends of the arch cofferdam are standard butt joint structures with the vertical plane, so the abutment 10 is set on the upstream surface of the dam 3 and the two arches of the arch cofferdam. The transition structure abutment 10 between the ends and the joint surface of the arch cofferdam are also provided with a soft mold bag, and the soft mold bag is connected with a pouring pipe leading to the crest of the weir, and can be poured with concrete combined with water stop.

The construction method of the floating arch cofferdam comprises the following steps:

1. Remove sundries at the bottom of the water and level the foundation: due to previous repairs to the dam, a large amount of wood garbage, ballast and concrete blocks have accumulated near the heel of the dam. The crane hangs the grab bucket to excavate debris such as wood and stone ballast, and then uses a high-pressure water pump to send high-pressure water through the water inlet pipe to the high-pressure water gun and hydraulic dredger in the cofferdam, and uses the high-pressure water jet from the high-pressure water gun to wash away the gravel and sand. The sludge is formed into a certain consistency of mud, and the mud is sucked out by a hydraulic dredge or an air dredge. Then use a large dredger to excavate the covering layer and foundation pit to level the foundation. If there is a prominent uneven rock surface, it will be blasted in the water at a fixed height before excavation, so that the foundation can be controlled to only have a height difference of plus or minus 0.5m .

2. As shown in Figure 8, the floating platform 19 and the gate-shaped lifting tower 20 are assembled on the water surface: the floating platform 19 is assembled on the water surface where the cofferdam needs to be set up, and the floating platform 19 completed by splicing is arched, and the width of the middle operation area is 7 It is about 6 meters long and connects to form a water surface operation area 7. There are several door-shaped lifting towers 20 on the operation area 7. The supporting feet of the door-shaped lifting towers 20 are fastened on the floating platform 19. The door-shaped lifting towers 20 The steel mold can be raised and lowered by ropes to form a suspension buoyancy method to build the cofferdam.

3. Assemble the base 11 and the outer formwork steel plate 14 in the operation area 7: assemble the lowermost outer formwork steel plate 14 on the floating platform 19, the thickness of the steel plate is 6-20mm, it is made in the factory, and it is decomposed into several parts, so as to be transported to the floating platform platform19. The assembly and welding of the bottom outer steel formwork 14 are to be welded as a whole on the floating platform 19. In the gap time before entering the water after integral steel box is hoisted, the support beam on the floating platform 19 can be removed. In order to increase the rigidity of the base 11, stiffeners are welded at the bottom. This method has rich experience in bridge installation, and it will not be difficult in principle when applied to the construction of arch cofferdams. The outer formwork steel plate 14 is sealed and connected with the base 11. To form a box structure, the pedestal 11 and the outer formwork steel plate 14 can be continuously lowered into water to reduce the load gravity of the floating platform 19 by using the gantry lifting tower 20 .

4. Pour concrete with binding steel bars: the steel bars in the outer wall 71 of the arch cofferdam and the steel bars in the spacers 72 are all bound and formed on special molds, and then hoisted into the mold respectively, and plastic pads are set to ensure the concrete protective layer outside the steel bars. Thickness, then install the inner mold steel plate 15, the inner mold steel plate 15 is a hydraulic segmented structure. The demolition adopts the contraction method, and is pulled out with a hoist. In addition, steel pipes must be embedded along the centerline of the entire semi-circular arch cofferdam with a distance of 1-3 meters. In addition to pouring concrete, it is also used as a grouting pipe 13. As shown in Figure 8, the concrete is poured in layers, and after the lower concrete reaches 80% of the design strength, the upper layer of concrete is poured. When pouring, adopt continuous pouring, oblique segmentation, and horizontal layering pouring method. The thickness of the horizontal layering is controlled within 40cm. The interval between two layers of concrete should not exceed the initial setting time; Vibration is matched; after the dividing plate 72 has been poured, concrete is poured on the inner and outer walls 71 to the symmetrical positions on both sides respectively, so as to prevent the great difference in height of the concrete surfaces on both sides from causing inclination. Each layer of arch ring is formed by one-time continuous pouring. Construction joints must be chiseled, blown and cleaned, and then concrete should be poured after laying high-strength cement mortar. Layered pouring, layered sinking. This construction method must always use buoyancy and hook lifting force to adjust the balance of the arch cofferdam. Repeatedly, until the design height is reached. The cofferdam during construction can be continuously lowered into water by using the gantry lifting tower 20 to keep the sum of the buoyancy of the cofferdam and the pulling force of the hook greater than the dead weight of the cofferdam all the time.

5. The arch cofferdam is in place and the water is sealed and the dry work area is completed: prefabricated the abutment 10 at both ends of the arch cofferdam on the ground, and after the concrete pouring of the arch cofferdam 7 is completed, respectively haul and install the abutment 10 at both ends, and Pour C ₃₀ first-mix concrete into the flexible mold bags on both sides through the conduit, which is mixed with plasticizer and early strength agent, and use hoist and rope to make the arch cofferdam 7 and abutment 10 close to the dam 3, and also through grouting The pipe 13 pours concrete into the water-stop room 22 between the steel edge feet 12 of the arch cofferdam base to seal the water at the bottom of the cofferdam, and finally drains the water in the space between the cofferdam and the dam from the top of the cofferdam to complete the dry work area.

The present invention is mainly suitable for maintenance and reconstruction of various dams, water conservancy projects and other underwater projects without releasing water. However, if the two of the present inventions are assembled into a circle and fixed with steel piles, a circular dry work area can be formed. , so that it can be used in the foundation construction or restoration projects of various cross-river bridge piers, and can also be used in the exploration and development of some shallow seas and lake bottoms, as well as other projects that require dry operations in water.

Claims (9)

1. floating arch cofferdam, it is characterized in that: make by steel plate and Reinforced Concrete Materials, integral body is dome-shaped, short transverse is divided into several layers within it, every layer of horizontal plane direction is divided into several sections again, by encircleing inner arc at least two cabins of arch outer arc direction distribution, be not communicated with mutually between the cabin in every section, each cabin all is communicated with gauge tap and water pump by pipeline;

Also comprise the pedestal of being located at bottom, floating arch cofferdam, pedestal is the arch shell structure of end face opening, there are two arch steel sword pin the bottom surface of pedestal, steel sword pin is concordant with the outside, cofferdam, article two, limit, steel sword underfooting inwardly is the low-angle acute angle, article two, steel sword pin forms between a sealing, and the top is provided with grout pipe and is connected to the top, cofferdam between sealing.

2. according to the described floating arch cofferdam of claim 1, it is characterized in that: arch cofferdam upstream face thickness with the depth of water constant or gradually the thickening, the arch cofferdam downstream face for the depth of water thicken gradually, constant or step-like.

3. according to the described floating arch cofferdam of claim 1, it is characterized in that: floating arch cofferdam two ends and dam joint portion are provided with abut, the dam contact surface and the dam profile of abut match, itself and dam contact surface are equipped with the soft mode bag, abut and floating arch cofferdam bonding surface also are provided with the soft mode bag, and the soft mode bag is connected with builds pipe and lead to weir crest.

4. the job practices of the described floating arch cofferdam of claim 1 is characterized in that comprising the following steps:

One, water-bed foreign material and the levelling basis of removing;

Two, the water surface is assembled swim platform and door shape hoist tower;

Three, at operation area assembling pedestal and external mold steel plate;

Four, assembling reinforcement concreting;

Five, floating arch cofferdam is in place finishes the district that works with the sealing sealing.

5. according to the job practices of the described floating arch cofferdam of claim 4, it is characterized in that: water-bed remove foreign material and the levelling basis is to adopt large-scale dredge boat to excavate covering layer and foundation ditch operation levelling basis, if any outstanding uneven scar then in water with excavation again after the mode explosion of decide elevation.

6. according to the job practices of the described floating arch cofferdam of claim 4, it is characterized in that: the water surface is assembled swim a platform and a door shape hoist tower, set up on the part water surface of cofferdam the assembling platform that swims at need, the platform that swims that splicing is finished is arch, its operation area, middle part is run through and is communicated with formation one water surface operation area, several shape hoist towers are arranged on the operation area, and hoist tower is fixed on the platform that swims, and can utilize the suspension hook shaping steel die that rises and falls.

7. according to the job practices of the described floating arch cofferdam of claim 4, it is characterized in that: at operation area assembling cofferdam pedestal and external mold steel plate is to finish assembly unit in the workspace at the pedestal of factory's customization, external mold steel plate and pedestal are tightly connected and constitute the casing junction structure, and utilize door shape hoist tower that pedestal and external mold are constantly transferred in the entry, to alleviate the platform institute load gravity that swims.

8. according to the job practices of the described floating arch cofferdam of claim 4; it is characterized in that: the assembling reinforcement concreting is with the outer wall of arch cofferdam and all colligation shapings on special mold of the reinforcing bar in the dividing plate; mould is gone in lifting respectively then; and plastic cushion is set; to guarantee the thickness of the outer concrete cover of reinforcing bar; the internal mold steel plate is installed subsequently; the internal mold steel plate is hydraulic segmented formula structure; remove and adopt shrinkage method; draw with hoist engine; concrete is a placement layer by layer; after lower-layer concrete reaches more than 80% design strength; build the last layer concrete again, can utilize a shape hoist tower will construct in the cofferdam constantly transfer entry, remain cofferdam buoyancy and suspension hook pulling force greater than changeing the weir deadweight.

9. according to the job practices of the described floating arch cofferdam of claim 4, it is characterized in that: floating arch cofferdam in place with sealing sealing and the finishing district's step of working be the prefabricated floating arch cofferdam two ends abut on ground earlier, after treating that floating arch cofferdam concreting is finished, the two ends abut is installed in haul respectively, and wherein mix fluidizer and early strength admixture by conduit concrete perfusion in the soft mode bag of both sides, utilize hoist engine and rope that arch cofferdam and abut are close to dam, equally by conduit between arch cofferdam base steel sword pin between sealing in concrete perfusion carry out the water shutoff of cofferdam bottom, outwards drain the water in cofferdam and the dam space at last from the top, cofferdam, finish the district that works.

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