A construction method for the bottom sealing of a cofferdam

Abstract

The present invention provides a construction method for the bottom sealing of a cofferdam, which includes the following steps: dredging the riverbed inside the steel cofferdam; piling up sandbags at the concrete placing points of the steel cofferdam, and arranging anti-segregation conduits on the upper side of the sandbags for concrete pouring and bottom sealing; arranging floating boxes on the water surface, arranging concrete detectors on the floating boxes, lowering the probes of the concrete detectors through plumb lines, and monitoring the concrete pouring height in real time to control the top elevation and the position of the placing points until the bottom sealing operation of the cofferdam is completed. By piling up sandbags at the placing points, the concrete falling from the anti-segregation conduits can be buffered, preventing the concrete from being mixed with ultra-thick silt due to the impact force, resulting in the concrete being unable to form a dense whole, thus affecting the construction quality. Further, through the mobile detection method combining the floating boxes, the concrete detectors and the plumb bobs, the accuracy of controlling the bottom sealing elevation of the cofferdam is improved, the secondary leveling process is reduced, the construction period is accelerated, and at the same time, the position of the placing points is easy to control, ensuring the construction quality.

Description

Technical Field

[0001] The present invention relates to the technical field of cofferdam construction, and particularly relates to a construction method for cofferdam bottom sealing. Background Art

[0002] A cofferdam refers to a temporary enclosure structure built during the construction of water conservancy projects for the construction of permanent water conservancy facilities. Its function is to prevent water and soil from entering the construction location of the building, so as to drain water within the cofferdam, excavate the foundation pit, and build the building.

[0003] In the prior art, for the underwater bottom sealing construction project of a steel cofferdam, due to the complex underwater environment and limited visible distance, it is impossible to monitor and control the top elevation of the bottom-sealing retarder concrete. At the same time, due to the different specific gravities of the ultra-thick silt layer and concrete, during the bottom-sealing process, the silt layer will accumulate with the self-flow effect of the bottom-sealing concrete. When the accumulation is too high, the top surface of the bottom-sealing concrete will form a wave shape, with a locally high elevation and insufficient effective thickness at some positions, affecting the construction quality. Summary of the Invention

[0004] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a construction method for cofferdam bottom sealing, aiming to solve the technical problem of poor construction quality in the prior art.

[0005] To achieve the above purpose, the present invention is realized through the following technical solutions: A construction method for cofferdam bottom sealing, which is applied to the underwater cofferdam construction in a thick silt layer, includes the following steps:

[0006] Carry out dredging treatment on the riverbed inside the steel cofferdam;

[0007] Stack sandbags at the concrete placement points of the steel cofferdam, and set an anti-segregation conduit on the upper side of the sandbags for concrete pouring and bottom sealing;

[0008] Set a floating box on the water surface, set a concrete detector on the floating box, lower the probe of the concrete detector through a plumb line, and based on the lowering length of the plumb line and the detection result of the concrete detector, monitor the height of the concrete in real time during the concrete pouring and bottom sealing process until the height of the concrete at the concrete placement point reaches a preset standard value;

[0009] Move the plumb line, measure the height of the concrete in the nearby area where the height of the concrete reaches the preset standard value, move the anti-segregation conduit to the concrete placement point where the height of the concrete reaches the preset value, and insert it into the concrete at a preset depth for concrete pouring and bottom sealing until the height of the concrete at the concrete placement point reaches the preset standard value. Repeat the above steps of moving the anti-segregation conduit and concrete pouring and bottom sealing until the cofferdam bottom sealing operation is completed.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: Firstly, by dredging the riverbed, it is convenient for subsequent concrete pouring for bottom sealing. Before pouring, by piling up sandbags at the batching points, the concrete falling from the anti-segregation conduit can be buffered, preventing the concrete from mixing with the ultra-thick silt due to the impact force, which may cause the concrete to fail to form a dense whole and thus affect the construction quality. Further, by setting up floating boxes on the water surface and installing concrete detectors on the floating boxes, and lowering the probes of the concrete detectors along the plumb lines, the height of the concrete during the concrete pouring for bottom sealing can be detected in real time based on the lowering length of the plumb lines and the detection results of the concrete detectors, so as to control the top surface height of the concrete to meet the design requirements. Further, by using the above method of lowering the plumb lines to detect the height of the concrete near the above wiring points, and at the same time finding the corresponding secondary batching points based on the pouring height of the already poured concrete, it is avoided that due to the long distance between the two batching points, silt accumulates due to extrusion between the two concrete pourings and mixes into the bottom sealing concrete layer, resulting in local concrete failure. By inserting the concrete to a preset depth before batching, it can also prevent the concrete from mixing with the ultra-thick silt and ensure the construction quality.

[0011] According to one aspect of the above technical solution, repeating the steps of moving the anti-segregation conduit to the batching point where the concrete height reaches the preset value and inserting it into the concrete to a preset depth for concrete pouring for bottom sealing, the method further includes:

[0012] Setting up a slag bucket to detect the silt at the edge of the concrete in real time and cleaning it through a mud suction pump.

[0013] According to one aspect of the above technical solution, before the step of completing the cofferdam bottom sealing operation, the method further includes:

[0014] Setting up a dredging pump pipe on the side of the steel cofferdam away from the batching point to clean the accumulated silt at a fixed point.

[0015] According to one aspect of the above technical solution, the method further includes:

[0016] Setting a retarder in the concrete.

[0017] According to one aspect of the above technical solution, the step of dredging the riverbed inside the steel cofferdam specifically includes:

[0018] Large-area cleaning of the silt inside the steel cofferdam by a long-arm excavator, a grab bucket and a hydraulic dredging pump;

[0019] When the hydraulic dredging pump stirs the silt inside the steel cofferdam, cleaning the silt inside the steel cofferdam through a high-pressure air-lift circulation device.

[0020] According to one aspect of the above technical solution, after the step of cleaning the silt in the steel cofferdam through the high-pressure gas lift circulation device, the method includes:

[0021] Clean the silt on the outer wall of the steel casing and the inner wall of the steel cofferdam with a high-pressure water gun shovel.

[0022] According to one aspect of the above technical solution, after the step of cleaning the silt on the outer wall of the steel casing and the inner wall of the steel cofferdam with a high-pressure water gun shovel, the method further includes:

[0023] Lower the plumb line along the outer wall of the steel casing and the inner wall of the steel cofferdam, and detect the cleaning result according to the lowering height of the plumb line.

[0024] According to one aspect of the above technical solution, a conical buffer plate is provided on one side of the discharge port of the anti-segregation conduit, and the slope ratio of the conical buffer plate is 2%.

[0025] According to one aspect of the above technical solution, the preset value a satisfies: 0.75b > a > 0.25b; where b is the preset standard value.

[0026] According to one aspect of the above technical solution, the preset depth c satisfies: c > 30 cm. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a flowchart of the construction method for the bottom sealing of the cofferdam in an embodiment of the present invention;

[0028] Figure 2 It is a position distribution diagram of the cloth points and the material discharging points in an embodiment of the present invention;

[0029] Figure 3 It is a schematic diagram of the bottom sealing operation in an embodiment of the present invention;

[0030] The following specific embodiments will further illustrate the present invention in conjunction with the above drawings. SPECIFIC EMBODIMENTS

[0031] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0032] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for illustrative purposes.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0034] Please refer to Figure 1 , which shows a flowchart of the cofferdam bottom sealing construction method in an embodiment of the present invention, including the following steps:

[0035] Step S100, dredge the riverbed inside the steel cofferdam. Specifically, in this step, during the falling process of the concrete, due to its impact force, it will be mixed with the ultra-thick silt, resulting in the concrete not being able to form a dense whole and affecting the construction quality. Therefore, after the steel cofferdam is completed and the first layer of steel support is installed, it is necessary to clean the silt in the cofferdam.

[0036] Preferably, in this embodiment, the above step S100 specifically includes:

[0037] Step S101, conduct large-area cleaning of the silt inside the steel cofferdam through a long-arm excavator, a grab bucket and a hydraulic dredging pump;

[0038] Step S102, when the hydraulic dredging pump stirs the silt inside the steel cofferdam, clean the silt inside the steel cofferdam through a high-pressure air-lift circulation device. For the ultra-thick silt geological layer, the three types of dredging methods, namely the long-arm excavator, the hydraulic dredging pump and the grab bucket, can jointly provide a good working environment for the high-pressure air-lift circulation dredging. Its function is not only to clean the silt but also to stir the silt inside the steel cofferdam so that the high-pressure air-lift circulation device can clean the silt and improve the working efficiency of the high-pressure air-lift circulation device.

[0039] Furthermore, in some application scenarios of this embodiment, due to dead corners in the cleaning of the inner side wall of the steel sheet pile and the outer wall of the water pile foundation casing and other structures during the dredging process, which cannot be cleaned, it is easy to cause the bottom-sealing concrete to have a low bonding degree with the structure, insufficient anti-floating capacity of the cofferdam, and safety production accidents such as sudden upwelling of the cofferdam after pumping water from the cofferdam. In this embodiment, the above step S100 further includes:

[0040] Step S103, clean the silt on the outer wall of the steel casing and the inner wall of the steel cofferdam by using a high-pressure water gun shovel. Specifically, in this embodiment, the above cleaning operation is mainly achieved by a diver controlling the high-pressure water gun shovel. Preferably, in this embodiment, to ensure the cleaning effect, after step S103, the method further includes:

[0041] Step S104, lower the plumb line along the outer wall of the steel casing and the inner wall of the steel cofferdam, and detect the cleaning result according to the lowering height of the plumb line. Inspect the outer wall of the steel casing and the inner wall of the steel sheet pile by using the plumb line. Only after passing the inspection can the pouring of the underwater concrete be organized and started.

[0042] Step S110, stack sandbags at the placing point of the steel cofferdam, and set a segregation-preventing conduit on the upper side of the sandbags for concrete pouring for underwater sealing. Specifically, in this step, to further prevent the concrete from being mixed with the ultra-thick silt due to the impact force, sandbags are set at the placing point for buffering before the feeding operation of the concrete pouring for underwater sealing. Preferably, in this embodiment, the laying diameter of the above sandbags is 3m. At the same time, to ensure that the effective thickness of the underwater concrete meets the requirements, the stacking height of the sandbags shall not intrude into the bottom elevation of the underwater concrete.

[0043] Preferably, in this embodiment, to reduce the impact force of the concrete during lowering, a conical buffer plate is provided on one side of the outlet of the segregation-preventing conduit, and the slope ratio of the conical buffer plate is 2%.

[0044] Step S120, set a floating box on the water surface, set a concrete detector on the floating box, lower the probe of the concrete detector through the plumb line, and monitor the height of the concrete in the process of concrete pouring for underwater sealing in real time based on the lowering length of the plumb line and the detection result of the concrete detector until the height of the concrete at the placing point reaches the preset standard value. Specifically, in the prior art, the height of the underwater sealing in the process of concrete pouring for underwater sealing is usually controlled by the traditional plumb bob method, with low accuracy and mainly relying on construction experience. By cooperating with a concrete detector on the basis of the traditional plumb bob method, the accuracy of controlling the height of the underwater concrete in the process of concrete pouring can be greatly improved, and the construction quality can be improved. In some application scenarios of this embodiment, the plumb bob and the concrete detector are used to pass through the middle of the annular floating box, and by controlling the water level elevation and positioning the elongation length of the plumb bob and the concrete detector, the control of the underwater concrete elevation can be achieved. The concrete detector locates the concrete elevation by showing red when contacting the concrete and yellow when contacting the mud.

[0045] Step S130: Move the plumb line to measure the concrete height in the vicinity of the area where the concrete height reaches the preset standard value. Move the segregation prevention conduit to the placing point where the concrete height reaches the preset value, and insert it into the concrete at a preset depth for concrete pouring and bottom sealing until the concrete height at the placing point reaches the preset standard value. Specifically, in the traditional cofferdam bottom sealing construction operation, it is necessary to move the concrete placing conduit multiple times to complete the concrete pouring of the entire bottom surface. In traditional construction operations, the setting of the placing points is usually based on experience. Since the underwater bottom sealing is not visible, improper arrangement of the placing point positions is likely to cause local failure of the concrete. If the distance between two placing points is too close, it will cause the local concrete to exceed the standard height. If the distance between two placing points is too far, it may lead to insufficient local concrete thickness. In this step, the above-mentioned preset standard value is the preset top surface height of the bottom-sealing concrete, which can be obtained by the horizontal plane - fixed height. By setting the plumb line and the concrete detector to detect the concrete height, the accuracy of the cofferdam bottom sealing elevation control is improved, the secondary leveling process is reduced, the construction period is accelerated. When the height of the placing point reaches the preset standard value, the position of the next placing point is determined based on the height of the already poured concrete top surface (preset value), reducing the depth of underwater silt cleaning and the crushed stone replacement process, reducing the mixed thickness of the bottom-sealing concrete and the silt, increasing the effective thickness of the bottom-sealing concrete, and ensuring the construction quality while increasing the economic benefits. Preferably, in this embodiment, the above-mentioned preset value a satisfies: 0.75b > a > 0.25b; where b is the preset standard value, and the preset depth c satisfies: c > 30 cm.

[0046] Step S140: Repeat the above steps of moving the segregation prevention conduit to the placing point where the concrete height reaches the preset value and inserting it into the concrete at a preset depth for concrete pouring and bottom sealing until the cofferdam bottom sealing operation is completed. For easy understanding, the approximate distribution and movement path of the above-mentioned placing points are as Figure 2 shown.

[0047] It should be noted that, as Figure 3 shown, during the bottom sealing construction process in the ultra-thick silt layer, in the later stage of the bottom sealing construction in the ultra-thick silt layer, the ultra-thick silt will be squeezed above the concrete or wrapped and covered by the concrete. The self-weight of the concrete will balance with the self-weight of the ultra-thick silt, resulting in a situation where the local concrete pouring surface is too high and the local effective thickness is insufficient. As a result, after the bottom sealing is completed, the bottom sealing surface will be wavy or the effective thickness of the bottom sealing is insufficient.

[0048] In this embodiment, to solve the above problems, in step S140, the method further includes:

[0049] Step S150: Set up a slag bucket to detect the silt at the edge of the concrete in real time and clean it up through a sludge suction pump. The above-mentioned fabricating point with sandbags is set on one side of the cofferdam. During the later stage of bottom sealing, the slag bucket set on the side of the cofferdam area away from the fabricating point is used to detect the silt formed by the compaction at the corner of the cofferdam, and the detected compacted silt is promptly and fixedly cleaned up by using the sludge suction pump and the dredging pump pipe, so as to achieve the purpose of bottom sealing, detecting, and cleaning simultaneously, releasing the pressure outside the self-leveling concrete, and reducing the occurrence of situations such as mud inclusion, improving the stability and quality of the cofferdam bottom sealing. In addition, in this embodiment, in order to gain time for the dredging operation, a retarder can be added to the concrete to achieve the effect of prolonging the initial setting time of the concrete.

[0050] In summary, for the cofferdam bottom sealing construction method in the above embodiments of the present invention, by dredging the riverbed, it is convenient for subsequent concrete pouring and bottom sealing. Specifically, by cleaning the silt attached to the outer wall of the steel casing and the inner wall of the steel cofferdam, the adhesion between the bottom-sealing concrete and the steel casing and the inner wall of the steel cofferdam is increased, the probability of local upwelling after the cofferdam is pumped is reduced, and the safety of the cofferdam bottom sealing is improved. By setting up an anti-segregation conduit and adding a conical buffer plate for concrete pouring, the depth of underwater silt cleaning and the process of replacing with crushed stones are reduced, the mixed thickness of the bottom-sealing concrete and the silt is reduced, the effective thickness of the bottom-sealing concrete is increased, and the economic benefit is increased. Before pouring, by piling up sandbags at the fabricating point, the concrete falling from the anti-segregation conduit can be buffered to prevent the concrete from mixing with the ultra-thick silt due to the impact force, resulting in the concrete being unable to form a dense whole and affecting the construction quality. Further, by setting up a floating box on the water surface and a concrete detector on the floating box, and lowering the probe of the concrete detector through a plumb line, the height of the concrete during the concrete pouring and bottom-sealing process is detected in real time based on the lowering length of the plumb line and the detection result of the concrete detector, so as to control the top surface height of the concrete to meet the design requirements. Further, the height of the concrete near the above-mentioned wiring point is detected by the method of lowering the above-mentioned plumb line, and at the same time, the corresponding secondary feeding point is found based on the pouring height of the already poured concrete, avoiding the situation that due to the long distance between the two feeding points, silt accumulates due to extrusion between the two poured concretes and mixes into the bottom-sealing concrete layer, resulting in local concrete failure. By inserting into the concrete to a preset depth and then feeding, the concrete can also be prevented from mixing with the ultra-thick silt and the construction quality can be guaranteed. During the bottom-sealing process, by adding a retarder to prolong the initial setting time of the concrete, time is gained for cleaning the silt during the bottom-sealing process, and then the position of the bottom-sealing concrete is detected by a slag bucket, and the dredging pump pipe is erected in advance to fixedly remove the compacted silt, preventing the situation that the ultra-thick silt is squeezed above the concrete or covered by the concrete, resulting in a wavy bottom-sealing surface, causing the bottom-sealing surface to be too high or the effective thickness of the bottom-sealing to be insufficient.

[0051] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0052] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A construction method for the bottom sealing of a cofferdam, which is applied to the construction of an underwater cofferdam in a thick silt layer, is characterized in that The method includes the following steps: Dredge the riverbed inside the steel cofferdam; Stack sandbags at the concrete placing points of the steel cofferdam, and set a segregation prevention conduit on the upper side of the sandbags for concrete pouring and bottom sealing; Set a floating box on the water surface, set a concrete detector on the floating box, lower the probe of the concrete detector through a plumb line, and monitor the height of the concrete in real time during the concrete pouring and bottom sealing process based on the lowering length of the plumb line and the detection result of the concrete detector until the height of the concrete at the placing point reaches the preset standard value; Move the plumb line, measure the height of the concrete in the area near where the concrete height reaches the preset standard value, move the segregation prevention conduit to the placing point where the concrete height reaches the preset value, and insert it into the concrete at a preset depth for concrete pouring and bottom sealing until the height of the concrete at the placing point reaches the preset standard value; Repeat the above steps of moving the segregation prevention conduit to the placing point where the concrete height reaches the preset value and inserting it into the concrete at a preset depth for concrete pouring and bottom sealing until the bottom sealing operation of the cofferdam is completed.

2. The cofferdam bottom sealing construction method according to claim 1, characterized in that, Among the steps of repeating the above steps of moving the segregation prevention conduit to the placing point where the concrete height reaches the preset value and inserting it into the concrete at a preset depth for concrete pouring and bottom sealing, the method further includes: Set a slag bucket to detect the silt at the edge of the concrete in real time and clean it through a mud suction pump.

3. The cofferdam bottom sealing construction method according to claim 1, characterized in that, Before the step of completing the bottom sealing operation of the cofferdam, the method further includes: Set a dredging pump pipe on the side of the steel cofferdam far from the placing point to clean the accumulated silt at a fixed point.

4. The cofferdam bottom sealing construction method according to claim 1, characterized in that, The method further includes: Set a retarder in the concrete.

5. The cofferdam bottom sealing construction method according to claim 1, characterized in that, The step of dredging the riverbed inside the steel cofferdam specifically includes: Large-area clean the silt inside the steel cofferdam through a long-arm excavator, a grab bucket and a hydraulic dredging pump; When the hydraulic dredging pump stirs the silt inside the steel cofferdam, clean the silt inside the steel cofferdam through a high-pressure air-lift circulation device.

6. The cofferdam bottom sealing construction method according to claim 5, characterized in that After the step of cleaning the silt inside the steel cofferdam through the high-pressure air-lift circulation device, the method includes: Clean the silt on the outer wall of the steel casing and the inner wall of the steel cofferdam through a high-pressure water gun shovel.

7. The cofferdam bottom sealing construction method according to claim 6, characterized in that, After the step of cleaning the silt on the outer wall of the steel casing and the inner wall of the steel cofferdam through the high-pressure water gun shovel, the method further includes: Lower the plumb line along the outer wall of the steel casing and the inner wall of the steel cofferdam, and detect the cleaning result according to the lowering height of the plumb line.

8. The cofferdam bottom sealing construction method according to claim 1, characterized in that A conical buffer plate is provided on the discharge port side of the segregation prevention conduit, and the slope ratio of the conical slope of the conical buffer plate is 2%.

9. The cofferdam bottom sealing construction method according to claim 1, characterized in that, The preset value a satisfies: 0.75b > a > 0.25b; where b is the preset standard value.

10. The cofferdam bottom sealing construction method according to claim 1, characterized in that, The preset depth c satisfies: c > 30 cm.

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