Water stopping method for single-layer Larsen steel sheet pile cofferdam in shallow sea tidal region

Abstract

The invention relates to a shallow sea tidal region single-layer Larsen steel sheet pile cofferdam water stopping method which comprises the following steps: firstly, constructing a Larsen steel sheet pile cofferdam main body structure and pouring cofferdam bottom sealing concrete; secondly, under the low tide level, a foaming agent is used for conducting first water stop construction on the gaps of the steel sheet piles, and the foaming agent is embedded into the gaps through seawater pressure to form a primary water stop layer; then, the water stop wall is poured through quick-setting concrete, gaps between the bottom sealing concrete and the Larsen steel sheet piles are blocked, the water stop effect is enhanced, and the steel sheet piles are stabilized; and after the water stop wall is completed, the half-section PVC pipe is fixed between the seams, quick-setting mortar is poured for second water stop construction, water leakage between the steel sheet pile seams is thoroughly blocked, and the water stop performance of the cofferdam in the construction period is ensured. The method has the effects of shortening the construction period, reducing the cost and guaranteeing the project quality.

Description

Technical Field

[0001] The present invention relates to the field of water-crossing cofferdam engineering, and specifically to a method for water-stop of a single-layer Larssen steel sheet pile cofferdam in a shallow sea tidal area. Background Art

[0002] With the acceleration of the urbanization process and the continuous development of coastal beach areas, the construction of coastal landscape bridges and wharves is increasing day by day. In the construction of these projects, the construction of underwater bridge piers and foundations often involves the construction of temporary water-blocking cofferdams. The single-layer Larssen steel sheet pile cofferdam occupies an important position in various underwater cofferdam constructions due to its unique advantages, such as fast construction speed, reusable materials, and relatively low cost.

[0003] However, in the special environment of the shallow sea tidal area, the water-stop problem of the single-layer Larssen steel sheet pile cofferdam is particularly prominent. Due to the tidal action of the sea water, the water levels inside and outside the cofferdam change continuously. Especially at high tide, the water pressure is extremely high, and it is very easy for water leakage to occur between the Larssen steel sheet piles. This kind of water leakage not only affects the construction safety of the structure inside the cofferdam, but also may lead to a decline in the quality of concrete pouring, and even cause safety accidents.

[0004] Traditional water-stop methods for Larssen steel sheet pile cofferdams often fail to meet the special requirements of the shallow sea tidal area. For example, some methods may rely on complex construction techniques or expensive water-stop materials, increasing the construction cost and difficulty; while other methods may not be able to effectively resist the water pressure impact at high tide due to poor water-stop effects.

[0005] After retrieval: CN117090188A: This patent proposes a construction method for plugging water between Larssen steel sheet piles, which realizes water-stop by making an outer U-shaped plugging groove and pouring concrete into the plugging groove in sections. Although this method can solve the water leakage problem to a certain extent, in the high water pressure environment of the shallow sea tidal area, the concrete in the plugging groove may not harden in time, resulting in poor plugging effects.

[0006] CN113622434B: This patent discloses a construction method for water-stop of Larssen steel sheet pile support in a deep foundation pit, which realizes water-stop by setting a water-stop grip and a water-stop sea belt at both ends of the Larssen steel sheet pile. This method has good effects in the deep foundation pit environment, but in the shallow sea tidal area, due to the influence of water pressure and tidal changes, it is difficult to ensure the water-stop effects of the water-stop grip and the water-stop sea belt. Summary of the Invention

[0007] The present invention aims to overcome the defects of the prior art and provides a method for water-stop of a single-layer Larssen steel sheet pile cofferdam in a shallow sea tidal area, so as to solve the water-stop problem of the single-layer Larssen steel sheet pile cofferdam in the shallow sea tidal area.

[0008] In order to solve the above technical problems, the present invention is realized as follows: A method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, characterized by the following steps: First, construct the main structure of the Larssen steel sheet pile cofferdam and pour the bottom - sealing concrete of the cofferdam; Second, at low tide, use a foaming agent to conduct the first - stage water - stoppage construction on the gaps between the steel sheet piles. The foaming agent is embedded into the gaps by the seawater pressure to form a preliminary water - stoppage layer; Then, pour a rapid - setting concrete water - stop wall to seal the gap between the bottom - sealing concrete and the Larssen steel sheet piles, so as to enhance the water - stoppage effect and stabilize the steel sheet piles; After the water - stop wall is completed, use a semi - cut PVC pipe to be fixed in the gap and pour rapid - setting mortar for the second - stage water - stoppage construction to completely seal the water leakage between the steel sheet piles and ensure the water - stoppage performance of the cofferdam during construction.

[0009] For the method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, it is characterized in that: during the first - stage water - stoppage construction, the foaming agent is applied both inside and outside the gaps between the steel sheet piles, and the foaming agent is embedded into the gaps by the seawater pressure to form a preliminary water - stoppage layer.

[0010] For the method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, it is characterized in that: the specific construction method of pouring the rapid - setting concrete water - stop wall is: at the gap between the bottom - sealing concrete of the cofferdam and the Larssen steel sheet piles, pour a rapid - setting concrete water - stop wall with a thickness of 30 cm and a height of 1 - 2 m, and add a rapid - setting agent to the concrete to ensure that the concrete can quickly harden under high pressure.

[0011] For the method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, it is characterized in that: during the second - stage water - stoppage construction, cut a 10 - cm - diameter PVC pipe in half, fix it at the position of the steel sheet pile gap with a U - shaped steel hoop, and then pour rapid - setting mortar to completely stop the water leakage between the gaps.

[0012] For the method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, it is characterized in that: after the second - stage water - stoppage construction is completed, construct the cap structure. After the cap structure is completed and before the pier column construction, remove the second - stage steel support of the cofferdam, transfer the support to between the lower cap and the water - stop wall, and use the water - stop wall as a temporary waling to enhance the overall stability of the cofferdam.

[0013] For the method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, it is characterized in that: the foaming agent is a high - molecular polymer foaming agent with good expansibility and sealing performance.

[0014] For the method for water stoppage of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, it is characterized in that: the rapid - setting mortar is ordinary mortar added with a rapid - setting agent, and its hardening time is controlled within 30 minutes.

[0015] The beneficial effects of the present invention are as follows: As can be seen from the above technical solutions, the present application provides a method for water stop of a single-layer Larssen steel sheet pile cofferdam in the shallow sea tidal area. The construction operation is simple, and the plugging materials are all common materials. The first water stop is by foaming agent, and the second is by PVC pipe + quick-setting mortar. The gap between the bottom concrete and the steel sheet pile is blocked by a water stop wall, which can not only effectively stop water but also stabilize the Larssen steel sheet pile. At the same time, when the pile cap is completed and the pier column is being constructed, the water stop wall can also act as a temporary purlin when the second support of the cofferdam is converted. Compared with the traditional construction process, this method is simple in construction and good in water stop effect. When constructing the structure inside the cofferdam, there is no need for underwater operation, which speeds up the construction progress and ensures the quality of concrete pouring. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The present invention will be further described in detail below with reference to the drawings and embodiments: Figure 1 It is a schematic diagram of a single-layer Larssen steel sheet pile cofferdam; Figure 2 It is a schematic diagram of the construction of foaming agent on the inner and outer sides of the gap of a single-layer Larssen steel sheet pile cofferdam; Figure 3 It is a plan view of the water stop wall at the gap between the bottom concrete and the steel sheet pile of a single-layer Larssen steel sheet pile cofferdam; Figure 4 It is a sectional view of the water stop wall at the gap between the bottom concrete and the steel sheet pile of a single-layer Larssen steel sheet pile cofferdam; Figure 5 It is a schematic diagram of plugging the gap with PVC pipe + quick-setting mortar on the inner side of the gap of a single-layer Larssen steel sheet pile cofferdam; Figure 6 It is a schematic diagram of setting the second support of the cofferdam by using the water stop wall and the pile cap structure during the construction of the pier column after the construction of the pile cap is completed, and the water stop wall acts as a temporary purlin. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings. Obviously, the described embodiments are some of the embodiments of the present application, rather than all of them. Based on the embodiments in the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope claimed by the present application. As Figures 1-6Shown: A method for water stoppage of a single-layer Larsen steel sheet pile cofferdam in the shallow sea tidal area. This method aims at the water stoppage problem of the single-layer Larsen steel sheet pile cofferdam in the shallow sea tidal area and realizes effective water stoppage through the following technical solutions: First, construct the main structure of the single-layer Larsen steel sheet pile cofferdam and pour the cofferdam bottom concrete; Subsequently, at low tide, use foam agent to plug the gaps between the steel sheet piles inside and outside, forming the first water stoppage barrier; Then, install water pumps inside the cofferdam to pump water, and pour a rapid-setting concrete water stoppage wall at the gap between the cofferdam bottom concrete and the Larsen steel sheet piles to deal with high-pressure water leakage at the bottom; After that, carry out the second water stoppage construction between the steel sheet piles. Fix the half-section PVC pipe in the gap and pour rapid-setting mortar to further strengthen the water stoppage effect; Finally, during the construction of the internal structure of the cofferdam, adjust the water pump as needed to maintain a safe water level, and carry out support conversion after the completion of the pile cap structure. Set the support between the water stoppage wall and the pile cap to enhance the overall stability of the cofferdam, thus comprehensively solving the water stoppage problem of the single-layer Larsen steel sheet pile cofferdam in the shallow sea tidal area.

[0018] Specific operation steps: Process 1: Construction of the main structure of the single-layer Larsen steel sheet pile cofferdam. In the shallow sea tidal area, the geological conditions are complex, the overburden layer is thin, and the depth of the steel sheet piles inserted into the seabed is insufficient. Under the impact of sea waves, there are slight deformations in the entire Larsen steel sheet pile cofferdam system, which is also the key factor for water leakage at the joint between the cofferdam bottom and the Larsen steel sheet piles.

[0019] Process 2: Pour the cofferdam bottom concrete. The pouring quality of the bottom concrete is the key to ensuring the overall stability of the cofferdam and no water leakage at the bottom of the cofferdam. This method aims to solve the water leakage between the steel sheet piles, so the pouring method and quality of the bottom concrete will not be elaborated in detail.

[0020] Process 3: At low tide, carry out the first water stoppage construction between the steel sheet piles (using foam agent to plug the gaps).

[0021] The sea water has tides. Taking advantage of the low tide time interval, quickly plug the gaps between the steel sheet piles with foam agent. Inject foam agent both inside and outside. After the sea water rises, the foam will be tightly embedded into the gaps under the pressure of the sea water. This is the first water stoppage between the gaps, which can block 80% of the water leakage.

[0022] Process 4: Install water pumps inside the cofferdam to pump water. With the first water stoppage, large water pumps can be put into use to pump the water inside the cofferdam to the bottom of the cofferdam. The quantity is calculated according to the time required for pumping water.

[0023] Step 5: Use a quick-setting concrete waterstop wall to seal the gap between the bottom concrete and the Larsen steel sheet piles. As explained in Step 1, this area experiences high water pressure, and any gaps are a key factor in bottom leakage. The high water pressure also causes significant leakage between the Larsen steel sheet piles. Therefore, a 30cm thick and 1-2m high waterstop wall is used to seal the gap. Because pouring the waterstop wall takes time, high water pressure prevents the concrete from hardening quickly, so an accelerating setting agent is added to the concrete.

[0024] Step 6: Perform a second round of waterstopping between the steel sheet piles (fixing half a PVC pipe between the seams and caulking them with quick-setting mortar). Immediately after the waterstop wall is completed, the second round of waterstopping is performed. Because the first round of waterstopping has a limited lifespan, it is necessary to reinforce the waterstopping to ensure the cofferdam is leak-proof for 2-3 months. A 10cm diameter PVC pipe is split in half and welded to the steel sheet pile seams using U-shaped steel hoops. Quick-setting mortar is then poured to completely stop any leaks.

[0025] Process 7: Remove the large water pump, install a small water pump to discharge small leaks in the cofferdam, and quickly construct the foundation structure.

[0026] Process 8: After the foundation structure is completed and before the pier construction, the second steel support of the cofferdam is removed, and the support is transferred to between the lower foundation and the water stop wall. The pier construction is carried out quickly. After the pier construction is completed, the steel sheet pile cofferdam is removed.

[0027] This application effectively addresses the interstitial leakage problem of a single-layer Larsen steel sheet pile cofferdam in shallow tidal areas by implementing a phased waterstop construction process, including an initial caulking process using a foam agent at low tide, followed by a second caulking process using PVC pipes and pouring rapid-setting mortar. The application of a rapid-setting concrete waterstop also effectively prevents leakage between the cofferdam's bottom concrete and the Larsen steel sheet piles, thereby comprehensively improving the cofferdam's waterstop performance.

[0028] Through a rational construction sequence and water-stopping measures, this approach avoids the downtime and waiting time associated with traditional construction techniques due to water leaks, thereby accelerating the construction process. This is particularly true in shallow tidal areas, where tidal forces impose strict time constraints on construction. The effective implementation of this technical solution allows critical construction work to be carried out during low tide periods, further shortening the overall construction period.

[0029] This application has no specific requirements for the age of the Larsen steel sheet piles, making construction simple. The sealing materials used are commonly available (such as foam, PVC pipe, and quick-setting mortar), reducing material costs. Furthermore, the improved water-stopping effect reduces the additional repair and reinforcement costs associated with leaks, further reducing overall construction costs.

[0030] Through the implementation of the quick-setting concrete water-stop wall and the water-stop measures between two steel sheet piles, the quality problems of concrete pouring caused by water leakage inside the cofferdam are effectively prevented. At the same time, the support conversion carried out after the completion of the cap structure also enhances the overall stability of the cofferdam, providing a reliable guarantee for the subsequent construction of the superstructure.

[0031] Moreover, through effective water-stop, the potential safety hazards caused by water leakage inside the cofferdam are reduced. Especially in the shallow sea tidal area, the water pressure at high tide is extremely high, and water leakage between joints may trigger safety accidents. By implementing this technical solution, the safety during the construction process can be significantly improved, ensuring the life safety of construction workers.

[0032] The above are only the embodiments provided by this application and are not used to limit this application. Although this application has been described in detail with reference to the embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. However, any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this application shall be included within the protection scope of this application.

Claims

1. A method for water stop of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone, characterized in that, It includes the following steps: First, construct the main structure of the L-shaped steel sheet pile cofferdam and pour the concrete for the bottom sealing of the cofferdam; Second, at low tide, use a foaming agent to conduct the first-stage water stop construction on the gaps between the steel sheet piles, and make the foaming agent embed into the gaps under the seawater pressure to form a preliminary water stop layer; After that, pour a rapid-setting concrete water stop wall to seal the gaps between the bottom-sealing concrete and the L-shaped steel sheet piles, so as to enhance the water stop effect and stabilize the steel sheet piles; After the completion of the water stop wall, fix a semi-sectioned PVC pipe in the gaps and pour rapid-setting mortar for the second-stage water stop construction to completely seal the water leakage between the steel sheet piles and ensure the water stop performance of the cofferdam during construction.

2. The single - layer Larssen steel sheet pile cofferdam water - stop method in the shallow - sea tidal zone according to claim 1, wherein: During the first-stage water stop construction, the foaming agent is applied both inside and outside the gaps between the steel sheet piles, and the foaming agent is made to embed into the gaps under the seawater pressure to form a preliminary water stop layer.

3. The method for stopping water in a shallow sea tidal area using a single-layer Larsen steel sheet pile cofferdam according to claim 1, characterized in that: The specific construction method for pouring the rapid-setting concrete water stop wall is: at the gaps between the bottom-sealing concrete of the cofferdam and the L-shaped steel sheet piles, pour a rapid-setting concrete water stop wall with a thickness of 30 cm and a height of 1 - 2 m, and add a rapid-setting agent to the concrete to ensure that the concrete can quickly harden under high pressure.

4. A method for preventing water leakage of a single - layer Larssen steel sheet pile cofferdam in a shallow - sea tidal area according to claim 1, characterized in that: During the second-stage water stop construction, a 10-cm diameter PVC pipe is cut in half, fixed at the positions of the gaps between the steel sheet piles with U-shaped steel hoops, and then rapid-setting mortar is poured to completely stop the water leakage between the gaps.

5. The method for stopping water in a shallow sea tidal area using a single-layer Larsen steel sheet pile cofferdam according to claim 1, characterized in that: After the completion of the second-stage water stop construction, construct the pile cap structure. After the completion of the pile cap structure and before the construction of the pier column, remove the second-stage steel support of the cofferdam, transfer the support to between the lower pile cap and the water stop wall, and use the water stop wall as a temporary waling to enhance the overall stability of the cofferdam.

6. A method for water stop of a single - layer Larssen steel sheet pile cofferdam in the shallow - sea tidal zone according to claim 1, characterized in that: The foaming agent is a polymer foaming agent, which has good expansibility and sealing performance.

7. The method for stopping water in a shallow sea tidal area using a single-layer Larsen steel sheet pile cofferdam according to claim 1, characterized in that: The rapid-setting mortar is ordinary mortar added with a rapid-setting agent, and its hardening time is controlled within 30 minutes.

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