Construction method of anti-seepage environment-friendly cofferdam in water source protection area

Abstract

The invention discloses a water source protection area anti-seepage environment-friendly cofferdam construction method which comprises the steps that a filter strip is constructed on the outer side of a cofferdam construction area, the top of the filter strip is located on the horizontal plane of a reservoir, the bottom of the filter strip sinks to the water bottom, and the two ends of the filter strip are connected with bank slopes; then steel trestles are constructed on the outer side of the cofferdam construction area and the inner side of the filter belt to serve as an operation platform and a channel during cofferdam construction; a cofferdam is constructed on the inner side of the trestle, two rows of steel sheet piles are driven into the cofferdam construction position, the head ends and the tail ends of the two rows of steel sheet piles are connected with the bank slope, water stopping treatment is conducted on the inner sides of the two rows of steel sheet piles, and a gap exists between the two rows of steel sheet piles; after construction of the two rows of steel sheet piles is completed, backfilling materials are used for backfilling gaps of the two rows of steel sheet piles, and therefore pollution to water quality of a water source is reduced on the basis that it is guaranteed that the cofferdam has the anti-seepage capacity.

Description

Technical Field

[0001] The present application relates to the field of cofferdam construction, and in particular to a method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area. Background Art

[0002] The raw water pipe project of the water plant is mainly to solve the problem of insufficient water supply in the city. By setting up a water intake tower at the location of the reservoir, constructing shafts at multiple locations in the city and connecting them with pipes, the water intake tower pumps water to the adjacent shaft, and transports the water source to the shafts in various locations in the city through pipes. Pump stations are arranged in the vertical reinforcement to pump out the water in the shaft and use it for urban water use. Before constructing the water intake tower, it is necessary to construct a cofferdam first. Since the water intake tower is located close to the shore, the shore terrain can be used in conjunction with a semi-open cofferdam to form a construction area with a closed side. However, in the current cofferdam construction technology, in order to improve the anti-seepage ability and structural strength of the cofferdam itself, underwater concrete pouring is required, which affects the quality of the water source. In addition, when the cofferdam is subsequently dismantled, the concrete structure needs to be broken, and the concrete fragments cause water pollution. Therefore, there is still room for improvement. Summary of the invention

[0003] In order to reduce the pollution to the water source and water quality while ensuring that the cofferdam has anti-seepage capabilities, the present application provides a method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area.

[0004] The present application provides a water source protection area anti-seepage environmental protection cofferdam construction method using the following technical solutions: A method for constructing an anti-seepage environmental protection cofferdam in a water source protection area comprises the following steps: A filter belt is constructed outside the cofferdam construction area, with the top of the filter belt located on the horizontal plane of the reservoir, the bottom of the filter belt sinking to the bottom of the water, and the two ends of the filter belt connected to the bank slope; Construct steel trestle bridges on the outside of the cofferdam construction area and on the inside of the filter belt to serve as operating platforms and passages during cofferdam construction; A cofferdam is constructed on the inner side of the trestle. Two rows of steel sheet piles are driven into the cofferdam construction position. Both ends of the two rows of steel sheet piles are connected to the bank slope. Water stopping treatment is performed on the inner side of the two rows of steel sheet piles. There is a gap between the two rows of steel sheet piles. After the construction of the two rows of steel sheet piles is completed, the gaps between the two rows of steel sheet piles are backfilled with backfill materials.

[0005] By adopting the above technical solution, the filter belt is set outside the construction area of ​​the cofferdam to form a filtration barrier, so as to block the debris produced by the subsequent cofferdam construction. In addition, double rows of steel sheet piles are used as the main structure of the cofferdam. By performing water-stopping treatment on the inner side of the steel sheet piles and using backfill materials instead of traditional concrete structures, the structural strength of the cofferdam can be improved, and the problem of water source pollution can be improved. On the basis of ensuring that the cofferdam has anti-seepage capabilities, the pollution of water source water quality can be reduced.

[0006] Preferably, in the filter belt construction steps, the filter belt includes a plurality of positioning piles, a plurality of buoys and a geotextile, which are first fixed at the corner positions of the filter belt by inserting and driving the positioning piles, and then a plurality of buoys are strung together with ropes to form a buoy chain, which is arranged along the extension direction of the filter belt and fixed to a plurality of positioning piles in sequence, and then the top of the geotextile is fixed to the buoy chain, and blocks of stone are arranged at the bottom of the geotextile to sink the bottom of the geotextile to the bottom of the water.

[0007] By adopting the above technical solution, the positioning piles play a positioning role, and the buoy chain composed of multiple buoys is stabilized on the water surface through the positioning piles. The geotextile serves as the main filtering structure, and its bottom sinks to the bottom through stones, thereby forming a filtering barrier in the water, which has the advantages of simple structure and high installation efficiency.

[0008] Preferably, the trestle construction and the cofferdam construction are carried out simultaneously and in the same direction, and the cofferdam construction is carried out using the trestle bridge section that has been built first as a construction platform.

[0009] By adopting the above technical solution, the trestle construction and the cofferdam construction are carried out synchronously and in the same direction, so that the cofferdam construction can be carried out by using the trestle bridge section built in advance as a construction platform, which is conducive to shortening the construction period.

[0010] Preferably, before constructing two rows of steel sheet piles, two rows of auxiliary piles are first driven at the cofferdam construction position, the two rows of auxiliary piles are spaced apart along the arrangement direction of the steel sheet piles, and guide steels are respectively installed on the outer sides of the two rows of auxiliary piles, the guide steels are horizontally arranged and extend along the arrangement direction of the steel sheet piles, and after the construction of the guide steels is completed, the two rows of steel sheet piles are driven with the guide steels as the guide structure.

[0011] By adopting the above technical solution, the auxiliary piles play a role in positioning and supporting the guide steel. The guide steel extends along the arrangement direction of the steel sheet piles. Using the guide steel as a guide is beneficial to improving the driving quality of the steel sheet piles.

[0012] Preferably, after the two rows of steel sheet piles are driven in, tension rods are arranged between the positions where the two rows of steel sheet piles are above the water level.

[0013] By adopting the above technical solution, the pull rods are used to pull the upper ends of the two rows of steel sheet piles, which is beneficial to improving the overall stability of the two rows of steel sheet piles.

[0014] Preferably, when taking water-stopping measures for steel sheet piles, a waterproof membrane is used as a water-stopping structure to cover the inner side of the steel sheet piles, and after the backfill material is backfilled in the gaps between the two rows of steel sheet piles, the waterproof membrane is tightly attached to the inner side of the steel sheet piles.

[0015] By adopting the above technical solution, the waterproof membrane plays a water-stopping role. After the backfill material is backfilled, the waterproof membrane is tightly attached to the steel sheet piles under the squeezing effect of the backfill material, which is beneficial to improve the water-stopping effect of the waterproof membrane.

[0016] Preferably, before backfilling the backfill material, several rows of steel sheet piles are inserted between two rows of steel sheet piles to divide the gaps between the two rows of steel sheet piles into several compartments.

[0017] By adopting the above technical solution, several vertical rows of steel sheet piles divide the gap between two rows of steel sheet piles into multiple compartments, which is beneficial to increase the overall stability of the cofferdam, facilitate safe construction, minimize water pollution, and can be landfilled one by one, which is conducive to the orderly progress of the backfill material backfilling steps.

[0018] Preferably, while backfilling the inner side of the double-row steel sheet piles with backfill material, slag backfill is also used on the outer side of the double-row steel sheet piles to apply back pressure to the steel sheet piles.

[0019] By adopting the above technical solution, slag is backfilled on the outside of the steel sheet pile to counter-press the steel sheet pile, provide support force for the outside of the steel sheet pile, which is beneficial to improve the stability of the steel sheet pile.

[0020] In summary, the present application includes at least one of the following beneficial technical effects: 1. By setting up the filter belt outside the construction area of ​​the cofferdam to form a filter barrier, the debris produced by the subsequent cofferdam construction can be blocked. In addition, double-row steel sheet piles are used as the main structure of the cofferdam. By doing water-stopping treatment on the inside of the steel sheet piles and using backfill materials instead of traditional concrete structures, the structural strength of the cofferdam can be improved, and the water source pollution problem can be improved. On the basis of ensuring that the cofferdam has anti-seepage ability, the pollution to the water source water quality can be reduced; 2. A number of positioning piles, a number of buoys and geotextiles are used as the filter belt structure. The positioning piles play a positioning role. The buoy chain composed of multiple buoys is stabilized on the water surface through the positioning piles. The geotextile is used as the main filtering structure, and its bottom is sunk to the bottom through stones, thereby forming a filtering barrier in the water. It has the advantages of simple structure and high installation efficiency; 3. By arranging a waterproof membrane on the inner side of the steel sheet pile, the waterproof membrane plays a water-stopping role. After the backfill material is backfilled, the waterproof membrane is tightly attached to the steel sheet pile under the squeezing effect of the backfill material, which is beneficial to improve the water-stopping effect of the waterproof membrane. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1It is a schematic diagram of the overall structure of a method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area in an embodiment of the present application.

[0022] Figure 2 yes Figure 1 A magnified schematic diagram of center A.

[0023] Explanation of the reference numerals: 1. Bank slope; 2. Steel sheet pile; 3. Pier; 4. Filter belt; 41. Positioning pile; 42. Buoy; 43. Geotextile; 5. Auxiliary pile; 6. Guide steel; 7. Tie rod. DETAILED DESCRIPTION

[0024] The following is combined with Figure 1-2 This application is described in further detail.

[0025] The present application embodiment discloses a method for constructing an anti-seepage environmental protection cofferdam in a water source protection area, referring to Figure 1 and Figure 2 , including the following steps: The filter belt 4 is constructed outside the cofferdam construction area, the top of the filter belt 4 is located on the horizontal plane of the reservoir, the bottom of the filter belt 4 sinks to the bottom of the water, and the two ends of the filter belt 4 are connected to the bank slope 1. In this embodiment, the filter belt 4 includes a plurality of positioning piles 41, a plurality of buoys 42 and a geotextile 43. The positioning piles 41 are first inserted and fixed at the corners of the filter belt 4, and then a plurality of buoys 42 are strung together with ropes to form a buoy chain. The buoy chain is arranged along the extension direction of the filter belt 4 and fixed to a plurality of positioning piles 41 in sequence, and then the top of the geotextile 43 is fixed to the buoy chain, and a stone is set at the bottom of the geotextile 43 to sink the bottom of the geotextile 43 to the bottom of the water. Among them, the buoy 42 uses a 0.5m×0.8m pollution-blocking net plastic buoy 42, which is set at an interval of 3m. The material specification of the geotextile 43 is 300g / m². Before hanging, a φ18 steel wire rope is installed at the top of the geotextile 43. In order to prevent the geotextile 43 from falling off, a transverse support rope is added in the middle of the geotextile 43 to form a net. The support rope uses a φ10 nylon rope and is laid at an interval of 3m. The geotextile 43 is about 12m high. When laying, it is appropriately adjusted according to the on-site terrain. The geotextile 43 is pulled into the water after the bank slope 1 is spliced. After the laying in the water is completed, the steel wire rope is fixed to the positioning pile 41, which is conducive to improving the stability of the geotextile 43. In other embodiments, a double-row filter belt 4 can be set to further improve the filtering effect.

[0026] A steel trestle 3 is constructed outside the cofferdam construction area and inside the filter belt 4 as an operating platform and passage during cofferdam construction. The steel trestle 3 is erected 1m outside the cofferdam construction area and is erected from right to left. The steel trestle 3 consists of four parts: foundation, lower structure, upper structure, and bridge deck. The trestle 3 is 10m wide and the net width of the bridge deck is 9m.

[0027] During the construction of the steel trestle 3, the first span of steel pipe piles is first driven in from one side of the bank slope 1, and then the distribution beams are welded, the longitudinal beams and Bailey beams are laid, and then the bridge deck is laid. After the single span is completed, the completed trestle 3 platform is used to drive forward and install the next span until the construction is completed.

[0028] In this embodiment, when the construction of the pier 3 is halfway done, the construction of the pier 3 and the cofferdam are carried out synchronously and in the same direction, and the cofferdam construction is carried out using the previously built section of the pier 3 as a construction platform, which is conducive to shortening the construction period.

[0029] Then, the cofferdam is constructed on the inner side of the trestle 3. Two rows of auxiliary piles 5 are inserted and driven at the cofferdam construction position. The two rows of auxiliary piles 5 are spaced along the arrangement direction of the steel sheet piles 2. The auxiliary piles 5 are φ630mm and 18m long. I36b I-beam corbels are set between the positioning piles 41 and the steel sheet piles 2. Multiple guide steels 6 are installed on the outer sides of the two rows of auxiliary piles 5. The guide steels 6 are arranged horizontally and spliced ​​and extended along the arrangement direction of the steel sheet piles 2. The guide steels 6 are erected on the corbels. The guide steels 6 are I36b I-beams and 12m long. The auxiliary piles 5 are rigidly reinforced by steel pipe parallel joints and steel pipe diagonal braces. The steel pipe parallel joints are φ400mm and 10m long. The diagonal brace steel pipes are φ350mm and 12m long.

[0030] After the construction of the guide steel 6 is completed, two rows of steel sheet piles 2 are driven in using the guide steel 6 as a guide structure. According to the plane layout, in order to ensure the safety of the cofferdam structure and facilitate construction, the length of the steel sheet piles 2 is uniformly 2 types, 9.0m and 18.0m respectively. During the construction of the steel sheet piles 2, they can be appropriately trimmed according to the plane arc turning section layout. After trimming or welding, the steel sheet piles 2 should be subjected to a lock test and inspection.

[0031] The bottom of the steel sheet pile 2 penetrates into the middle and upper part of the fully weathered granite at the bottom of the water. In actual construction, if the strong / weakly weathered granite surface is elevated, the depth of the steel sheet pile 2 into the strong / weakly weathered granite shall not be less than 0.5m. The permeability coefficient of the fully weathered granite layer is 6.5×10-5cm / s.

[0032] By driving two rows of steel sheet piles 2 at the cofferdam construction position, both ends of the two rows of steel sheet piles 2 are connected to the bank slope 1, thereby forming the main structure of the cofferdam, and then the inner sides of the two rows of steel sheet piles 2 are water-stopped, and there is a gap between the two rows of steel sheet piles 2.

[0033] In order to increase the overall stability of the cofferdam, facilitate safe construction, and minimize water pollution, a row of steel sheet piles 2 is set every 25m along the arrangement direction of the two rows of steel sheet piles 2 to form multiple compartments in the gap, and corner piles are set at the connection between the transverse steel sheet piles 2 and the longitudinal steel sheet piles 2.

[0034] It should be noted that in order to ensure that the steel sheet pile 2 can be driven smoothly and reduce the quality factor of the steel sheet pile 2 itself, a slow driving method is adopted during driving to reduce the deformation of the steel sheet pile 2 caused by blind brute force. When the steel sheet pile 2 is tilted at a small angle, the driven steel sheet pile 2 can be tightened with a hand winch to avoid the pile driven in front from tilting in the forward direction during driving; when the steel sheet pile 2 is tilted at a large angle, a wedge-shaped special-shaped pile is used to correct the deviation.

[0035] After the two rows of steel sheet piles 2 are driven in, a tension rod 7 is arranged between the positions of the two rows of steel sheet piles 2 above the water level, which is beneficial to improving the overall stability of the two rows of steel sheet piles 2 .

[0036] When taking water-stopping measures for the steel sheet piles 2, a waterproof membrane is used as a water-stopping structure to cover the inner side of the steel sheet piles 2. After the backfill material is backfilled in the gap between the two rows of steel sheet piles 2, the waterproof membrane is tightly attached to the inner side of the steel sheet piles 2 under the extrusion of the backfill material. This is beneficial to improving the water-stopping effect of the waterproof membrane. When arranging the waterproof membrane, first measure the water depth, and process the waterproof membrane according to the measured water depth. The length of the waterproof membrane is the measured water depth + 1m. Then fold the waterproof membrane as a whole into a line according to the fan surface, and fix the upper part of the waterproof membrane to the pull rod 7 with a nylon rope, with a fixed point every 2m. Then use a mesh bag to wrap the stones at the bottom of the waterproof membrane, with a stone mesh bag every 5m, and unify the stone mesh bags under the waterproof membrane, so that the waterproof membrane extends to the bottom of the water along the gravity of the stones.

[0037] After the construction of the two rows of steel sheet piles 2 is completed, backfill materials are used to backfill the gaps between the two rows of steel sheet piles 2. It should be noted that after the construction of the waterproof membrane is completed, the pouring and backfilling of gravel should be carried out slowly and not too fast.

[0038] In addition, the backfill material is gravel and crushed stone. When the backfill operation is carried out, the 12m³ muck truck uses the trestle 3 as a transportation channel to transport it to the cofferdam construction location. When the vehicle is transported to the cofferdam unloading point through the temporary steel trestle 3, the backfill material is dumped into the cofferdam through the steel plate chute (size 4*3m), and the long-arm excavator is used to assist in leveling the gravel in the cofferdam and backfilling to the designed elevation.

[0039] While backfilling gravel and crushed stones inside the double-row steel sheet piles 2, slag is also backfilled outside the double-row steel sheet piles 2 to counter-pressure the steel sheet piles 2. The backfill height is about 5.5m, the top width is 6m, and the back-pressure slope is 1:1.5. The backfill is performed by a long-arm excavator standing on the steel trestle 3, which stabilizes the cofferdam structure combining double-row steel sheet piles 2 with gravel and crushed stones. By replacing the traditional concrete structure with gravel and crushed stones, the structural strength of the cofferdam can be improved, and the problem of water source pollution can be improved. On the basis of ensuring that the cofferdam has anti-seepage ability, the pollution of water source water quality can be reduced.

[0040] After the main structure of the water intake tower is completed on the inner side of the cofferdam, the cofferdam dismantling construction is carried out. The steel trestle 3 is used as a construction platform, and a long-arm excavator is used to excavate the gravel backfilled inside the steel sheet pile 2 and the slag backfilled outside the steel sheet pile 2. Then, an 85t crawler crane equipped with a 90 vibration hammer is used to dismantle the cofferdam steel sheet pile 2 purlin and tie rod 7 and other components from far to near on the steel trestle 3 platform, and finally the steel sheet pile 2 and auxiliary pile 5 are removed. After the cofferdam is dismantled, the bridge deck, secondary distribution beam, Bailey frame, and main distribution beam are dismantled in a backward manner from top to bottom, and finally the double-row geotextile 43 filter belt 4 is dismantled by a crawler crane equipped with a pontoon.

[0041] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for constructing an anti-seepage environmental protection cofferdam in a water source protection area, characterized in that: The following steps are involved: A filter belt (4) is constructed outside the cofferdam construction area, the top of the filter belt (4) is located on the horizontal plane of the reservoir, the bottom of the filter belt (4) sinks to the bottom of the water, and both ends of the filter belt (4) are connected to the bank slope (1); A steel trestle (3) is constructed on the outside of the cofferdam construction area and on the inside of the filter belt (4) to serve as an operating platform and passage during cofferdam construction; A cofferdam is constructed on the inner side of the trestle (3), and two rows of steel sheet piles (2) are driven into the cofferdam construction position. Both ends of the two rows of steel sheet piles (2) are connected to the bank slope (1), and water stopping treatment is performed on the inner sides of the two rows of steel sheet piles (2), and there is a gap between the two rows of steel sheet piles (2); After the construction of the two rows of steel sheet piles (2) is completed, the gaps between the two rows of steel sheet piles (2) are backfilled with backfill materials.

2. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: In the construction steps of the filter belt (4), the filter belt (4) includes a plurality of positioning piles (41), a plurality of buoys (42) and a geotextile (43). The positioning piles (41) are first inserted and fixed at the corner positions of the filter belt (4), and then a plurality of buoys (42) are strung together by ropes to form a buoy chain. The buoy chain is arranged along the extension direction of the filter belt (4) and is fixed to the plurality of positioning piles (41) in sequence. Then, the top of the geotextile (43) is fixed to the buoy chain, and a stone is arranged at the bottom of the geotextile (43) to sink the bottom of the geotextile (43) to the bottom of the water.

3. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: The construction of the trestle (3) and the cofferdam are carried out simultaneously and in the same direction, and the cofferdam construction is carried out using the first completed trestle (3) bridge section as a construction platform.

4. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: Before constructing two rows of steel sheet piles (2), two rows of auxiliary piles (5) are first driven in at the cofferdam construction position. The two rows of auxiliary piles (5) are spaced apart along the arrangement direction of the steel sheet piles (2). Guide steels (6) are respectively installed on the outer sides of the two rows of auxiliary piles (5). The guide steels (6) are arranged horizontally and extend along the arrangement direction of the steel sheet piles (2). After the construction of the guide steels (6) is completed, the two rows of steel sheet piles (2) are driven in using the guide steels (6) as a guide structure.

5. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: After the two rows of steel sheet piles (2) are driven in, a tension rod (7) is arranged between the positions of the two rows of steel sheet piles (2) above the water level.

6. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: When taking water-stopping measures for the steel sheet piles (2), a waterproof membrane is used as a water-stopping structure to cover the inner side of the steel sheet piles (2). After the backfill material is backfilled in the gaps between the two rows of steel sheet piles (2), the waterproof membrane is tightly attached to the inner side of the steel sheet piles (2).

7. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: Before backfilling the backfill material, a plurality of rows of steel sheet piles (2) are inserted between two rows of steel sheet piles (2) to separate the gaps between the two rows of steel sheet piles (2) into a plurality of compartments.

8. The method for constructing an anti-seepage and environmentally friendly cofferdam in a water source protection area according to claim 1, characterized in that: While backfilling the inner side of the double-row steel sheet piles (2) with backfill material, slag is also backfilled on the outer side of the double-row steel sheet piles (2) to apply back pressure to the steel sheet piles (2).

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