A discontinuous construction method for a steel dam gate

Abstract

The application discloses a kind of steel dam lock section discontinuous construction method, adopt section construction, left and right section are divided into first phase and second phase, first phase and second phase construction period are separated by one flood season, after first phase structure construction is completed, structure construction is carried out to protect first phase built structure safety flood season and prepare for second phase cofferdam dewatering, specific construction steps include: S1, determine left and right section construction boundary line and construction sequence;S2, first phase construction;S3, structure construction of flood season;S4, first phase construction is finished;S5, second phase construction;Wherein, the structure of flood season in step S3 includes boundary protection, water interception curtain, thickened cushion, concrete strip, concrete panel, blind ditch and water collecting well.The application can effectively protect the right section built structure, safely pass through the flood season, and continuously monitor the settlement amount at the junction of left and right sections, so as to adjust the structure parameters in time when the left section is constructed, and solve the problem that the left section cofferdam cannot be pumped and drained due to being partially built on gabion section and riprap section.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering, and in particular to a method for discontinuous construction of steel dam gates. Background Technology

[0002] A certain water conservancy project has a steel dam gate with 9 openings, each with a span of 35 meters and a maximum width of 420 meters. The river channel is 395 meters wide. Construction requires continuous flow, so segmented construction is necessary. However, due to the massive scale of the project, it cannot be completed within a single year, so discontinuous construction across the flood season is required.

[0003] The project requires navigating two dry seasons and one flood season, with a six-month interval between the construction of the right and left spans, each spanning a flood season. The main construction challenges are: 1. After the right span structure is completed, the cofferdam will be removed. At this point, the right span structure is finished, but all relevant interfaces are exposed. Without protective measures, this will adversely affect the already constructed waterproof structure; 2. The gate at the junction of the left and right spans could not be completed in the first phase, preventing the construction of permanent structures for the corridor, the second phase of the bottom axis concrete, and the gate chamber roof. This could pose a significant risk during the flood season. 1. Floods exceeding standard levels pose a risk of channel inundation, which could cause significant damage to automated equipment in the metal structure; 2. The riverbed of the right-side constructed structure is rigid, while the riverbed of the left-side unconstructed structure is silty. During the flood season, there is a risk of scouring the riverbed at the junction of the left and right sides, leading to the risk of settlement of the right-side constructed structure; 3. When constructing the left-side structure during the dry season of the following year, the left-side cofferdam needs to be partially built on top of the right-side constructed structure and cannot be driven into the riverbed. Furthermore, the existing gabion section and riprap anti-scour section lack water-blocking capabilities, increasing the difficulty of dewatering construction within the right-side cofferdam.

[0004] Most existing technologies involve continuous construction, meaning that the construction of both sides is completed within a single dry season. However, for large-scale projects that require construction across the flood season, when constructing the second phase after the flood season, the overlapping portion of the second-phase cofferdam with the existing first-phase structure cannot be directly driven to the riverbed, resulting in the cofferdam's bottom lacking water-blocking capacity. Existing construction methods include two options: one is to demolish a portion of the existing structure during cofferdam construction and replace it with a sheet pile cofferdam driven to the riverbed; the other is to underwater seal the bottom of the second-phase cofferdam after its construction. Both approaches significantly increase the amount of underwater construction, extending the construction period and increasing costs.

[0005] Therefore, how to create a new method for the discontinuous construction of steel dam gates has become a goal that the industry urgently needs to improve. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for discontinuous construction of steel dam gates in sections, which can fully protect the existing structure in the first phase, ensure safe flood control, continuously monitor the settlement at the junction of the left and right sections so as to adjust the structural parameters in a timely manner during the second phase construction, and carry out the construction of water-cutting curtains, concrete strips, blind ditches and collection wells during the first phase construction to prepare for the second phase construction after the flood season, solve the problem that the second phase cofferdam cannot block water and that it is difficult to pump out water from inside the cofferdam, thereby overcoming the shortcomings of the existing technology.

[0007] To address the aforementioned technical problems, this invention provides a method for discontinuous construction of a steel dam gate, employing segmented construction, dividing the left and right sections into Phase I and Phase II, with a flood season interval between Phase I and Phase II construction. After the completion of Phase I structural construction, flood control structure construction is carried out to protect the existing Phase I structure during the flood season and to prepare for dewatering of the Phase II cofferdam. Specific construction steps include: Step S1: Determine the construction boundary line and construction sequence for the left and right lanes; Step S2: Phase I construction; Step S3: Construction of flood control structures; The flood control structure includes a water-cutting curtain, which is constructed in a row along the river direction from the boundary line between the left and right construction sections. Within the gabion and riprap sections, concrete strips are laid along the river at the top of the cutoff curtain, and concrete panels extending towards the existing structure are constructed on top of the concrete strips. In the cover section and stilling basin section, a thickened cushion layer is constructed on top of the cutoff curtain to connect the cutoff curtain with the existing structure. Within the gate chamber section, a blind ditch is constructed along the river at the bottom of the foundation pit between the existing structure and the cutoff curtain. A water collection well is constructed at the end of the blind ditch. After the blind ditch and water collection well are completed, the foundation pit is backfilled. Step S4: Finalization of Phase I construction; After the first phase of metal structure is installed, the cofferdam will be dismantled to prepare for the flood season. Step S5: Phase II construction; The second-phase cofferdam was constructed. In the gabion and riprap sections, it was built on concrete strips and concrete panels. In the cover section and stilling basin section, it was built on the existing concrete base slab and connected to the guide piers of the existing gate chamber.

[0008] Furthermore, in step S1, the construction boundary line between the left and right lanes is located between two adjacent gate chambers in the center of the river channel, with the right lane undergoing phase one construction and the left lane undergoing phase two construction.

[0009] Furthermore, the flood control structure in step S3 also includes boundary protection, which includes sealing of the corridor and sluice chamber, waterstop protection, and gravel backfilling; Corridor and gate chamber sealing: Brick walls are built inside the maintenance corridor, empty box, pipeline corridor and outside the template at the bottom axis position. Waterproof mortar layer, SBS asphalt waterproof membrane and pressure strip are applied to the outside of the brick wall in sequence. Waterstop protection: A wooden box is installed outside the exposed waterstop, and the wooden box is fixed to the main structure with cement nails; Crushed stone backfill: The foundation pit outside the gate chamber section is backfilled with the original riverbed soil to the top elevation of the gallery, and then compacted with crushed stone on top; the upstream and downstream connecting sections are backfilled with crushed stone to be flush with the existing concrete base slab.

[0010] Furthermore, the water-cutting curtain in step S3 is a three-axis mixing pile.

[0011] Furthermore, the top elevation of the triaxial mixing pile extends to below the already constructed structure.

[0012] Furthermore, in step S3, a steel mesh is arranged inside the concrete panel, and geotextile and waterproof cloth are laid underneath.

[0013] Furthermore, in step S5, after the second-phase cofferdam is built, the water level is lowered, the second-phase structure is constructed and the metal structure is installed, and the second-phase cofferdam is dismantled after completion.

[0014] Furthermore, during steps S2 to S5, real-time monitoring points are set up for sinking, and the monitoring targets are switched in stages, as follows: Phase 1: Monitoring will begin 15 days after the completion of the bottom slab of the gate chamber closest to the boundary in Phase 1. A total of 3 monitoring points will be set up on the bottom slab of the gate chamber, numbered BM1, BM2 and BM3 respectively. The monitoring targets are BM1, BM2 and BM3. Phase Two: Starting 15 days after the completion of the gate chamber sidewall pouring, two new monitoring points will be set up above the gate chamber sidewall, numbered BM4 and BM5 respectively, with BM1, BM2, BM3, BM4 and BM5 as the monitoring targets; Phase 3: After the first phase of cofferdam removal, the flood season begins. Only BM4 and BM5 will remain as monitoring targets. Monitoring will continue until the second phase of construction of the gate chamber bottom slab closest to the boundary is completed. Phase Four: Starting 15 days after the completion of the bottom slab of the gate chamber closest to the boundary in Phase II, three monitoring points will be set up on the bottom slab of the gate chamber, numbered BM6, BM7, and BM8, with BM4, BM5, BM6, BM7, and BM8 as the monitoring targets. Phase 5: Starting 15 days after the completion of the pouring of the gate chamber sidewall closest to the boundary in Phase 2, two new monitoring points will be set up above the gate chamber sidewall, numbered BM9 and BM10 respectively. The monitoring targets are BM4, BM5, BM9 and BM10. Monitoring will continue until step S5. Subsequently, permanent settlement monitoring points will be set up according to the design requirements.

[0015] With this design, the present invention has at least the following advantages.

[0016] 1. After the completion of the first phase of the gate chamber section construction, the corridor and gate chamber were sealed and the exposed waterstop was protected, which solved the problems of flooding risk in the gate chamber and corridor and damage risk in the exposed waterstop, ensuring the safety of the constructed structure during the flood season.

[0017] 2. Backfilling with crushed stone at the junction of the left and right lanes solved the problem of uneven foundation hardness at the junction, which could lead to deep erosion by the river during the flood season and cause unexpected settlement of the existing structure.

[0018] 3. During the first phase of construction, triple-axis mixing piles will be installed. These piles, integrated with the existing structure, will provide further protection at the junction of the left and right sections during the flood season, ensuring the stability of the foundation soil beneath the existing structure and preventing settlement caused by flood erosion. They will also serve as a cutoff wall for the second phase of construction, blocking lateral seepage, increasing seepage paths, and preventing excessive settlement caused by lateral seepage carrying away fine sand beneath the first phase structure. Furthermore, triple-axis mixing piles are a dry construction method. Compared to other later-stage above-water or underwater construction methods for blocking lateral seepage, this avoids the structural isolation issues associated with steel cofferdams and significantly reduces construction costs and difficulty.

[0019] 4. During the first phase of construction, concrete strips, concrete panels, thickened cushion layers, sump pits, and blind drains were constructed, which solved the problem of water blockage caused by the second phase cofferdam being partially built on top of the first phase structure. The advantage is that the three-axis mixing piles, concrete panels, thickened cushion layers, sump pits, and blind drains were all dry-trenched within the first phase cofferdam, and water could be successfully dewatered after the second phase cofferdam was built, which greatly reduced the amount of underwater construction and saved time and costs. The construction principle is: when one side of the triple-axis mixing pile can be connected to the existing structure (located in the paving section and stilling basin section), the top of the triple-axis mixing pile is connected to the existing structure by thickening the cushion layer; When there is no structure on one side of the three-axis mixing pile (located in the gabion section and the riprap section), a concrete strip is constructed on the top of the three-axis mixing pile and a concrete panel is constructed on the top of the gabion and riprap, so that the left cofferdam of the second phase can be built on the concrete strip and the concrete panel, solving the problem that the gabion and riprap cannot block water. When there is a structure on one side of the triple-axis mixing pile but it cannot be connected (located in the gate chamber section, the foundation pit trench has not been backfilled when the triple-axis mixing pile is constructed), the construction sump and blind ditch will ensure that the left side can be fully pumped out during construction.

[0020] 5. Set up real-time settlement monitoring points during construction and switch monitoring targets in stages to monitor the settlement of the gate chambers on both sides of the left and right lane boundary line in real time. Attached Figure Description

[0021] The above is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0022] Figure 1 This is a flowchart illustrating the present invention.

[0023] Figure 2 This is a plan view showing the location of the construction boundary line between the left and right lanes, the cofferdam on the left lane, and the cofferdam on the right lane in this invention.

[0024] Figure 3 This is a schematic diagram of the construction structure inside the right-side cofferdam.

[0025] Figure 4 yes Figure 3 A schematic diagram of the structure of section AA.

[0026] Figure 5 yes Figure 3 A schematic diagram of the structure of the BB section.

[0027] Figure 6 yes Figure 3 A schematic diagram of the CC section.

[0028] Figure 7 This is a schematic diagram of a partial structure for sealing the bottom shaft of the gate.

[0029] Figure 8 This is a schematic diagram showing the location of monitoring points during the first stage of subsidence.

[0030] Figure 9 This is a schematic diagram showing the location of monitoring points during the second phase of sedimentation.

[0031] Figure 10 This is a schematic diagram showing the location of monitoring points during the third stage of sedimentation.

[0032] Figure 11 This is a schematic diagram showing the location of monitoring points during the fourth stage of sedimentation.

[0033] Figure 12 This is a schematic diagram showing the location of monitoring points during the fifth stage of sedimentation.

[0034] Explanation of reference numerals in the attached diagram: 1. Right cofferdam; 2. Left cofferdam; 3. Construction boundary between left and right cofferdams; 4. Fourth gate chamber; 5. Fifth gate chamber; 6. Upstream connecting section; 7. Gate chamber section; 8. Downstream connecting section; 9. Pavement section; 10. Stilling basin section; 11. Gabion section; 12. Rockfill section; 13. Concrete base slab; 14. Triaxial mixing pile; 15. Thickened cushion layer; 16. Concrete strip; 17. Concrete panel; 18. Blind drain; 19. Sump; 20. Waterproof cloth; 21. Crushed stone; 22. Original riverbed soil; 23. Brick wall; 24. Buttress wall; 25. Waterstop; 26. Wooden box; 27. Formwork. Detailed Implementation

[0035] This invention provides a method for discontinuous construction of steel dam gates, which has been practically applied in the Xinggezhuang Gate project of the Chaobai River Comprehensive Management and Ecological Restoration Project (Tongzhou Section). Taking the actual situation of this project as an example, the construction method described in this application is further elaborated in the specific implementation method.

[0036] This construction method adopts a phased construction approach, with the left and right sections divided into Phase I and Phase II. A flood season separates the Phase I and Phase II construction periods. After the Phase I structural construction is completed, the flood control structure construction will commence to protect the existing Phase I structure during the flood season and prepare for the Phase II cofferdam dewatering. The specific construction steps are as follows.

[0037] Step S1: Determine the boundary line between the left and right construction sections and the construction sequence.

[0038] All construction work on the steel dam gate is divided into sections in the middle of the river channel, with the boundary line 3 between the left and right sections located between two adjacent gate chambers in the middle of the river channel.

[0039] In this embodiment, a total of 8 lock chambers are constructed, numbered sequentially from the right bank to the left bank of the river as Lock Chamber 1 to Lock Chamber 8. The construction boundary line 3 between the left and right lanes is located between Lock Chamber 4 and Lock Chamber 5. Based on the on-site road and site handover situation, the construction sequence is determined as follows: Phase I construction of the right lane, with a construction period from after the first flood season to before the following flood season; Phase II construction of the left lane, with a construction period from after the following flood season to before the next flood season.

[0040] In other embodiments, the construction sequence of the left and right sections can be adjusted according to the site conditions. It should be noted that... Figure 2 The direction of the middle arrow indicates the direction of river flow. Both the "right" and "left" views use the direction of river flow as the observation direction, which is opposite to the left-right direction shown in the attached diagram.

[0041] As can be seen from the diagram, the construction boundary line 3 between the left and right sections is not a straight line. The rectangular grids located in the paving section 9 and the stilling basin section 10 represent individual construction blocks. Construction joints are set between the blocks according to the design requirements. The concrete base slabs 13 at different locations differ slightly in structure (whether or not they are reinforced with steel bars) and material (concrete grade), but in general, they are all composed of a lower concrete cushion layer and an upper concrete surface layer, poured in layers. The rectangular grids represent the dimensions of a single construction operation. The principle for dividing the construction boundary line 3 between the left and right sections is to avoid disrupting the dimensions of the single construction blocks.

[0042] Step S2: Phase I construction.

[0043] Construct the right-side cofferdam 1 according to the design location and carry out the first phase of construction.

[0044] The steel dam gate comprises an onshore structure and a riverbed structure. The riverbed structure consists of three parts: the upstream connecting section 6, the gate chamber section 7, and the downstream connecting section 8. The upstream connecting section 6 includes a protective connecting section and a cover section 9. The downstream connecting section includes a stilling basin section 10, a seawall section, a scour protection section, and a reverse slope section. The main structure in the upstream protective connecting section, the downstream seawall section, and the reverse slope section is gabion, collectively referred to as gabion section 11 in this embodiment. The main structure in the scour protection section is riprap, referred to as riprap section 12 in this embodiment.

[0045] The first phase of construction includes the right bank structure and the upstream connecting section 6, the lock chamber section 7, and the downstream connecting section 8 within the right channel.

[0046] Step S3: Construction of flood control structures.

[0047] The flood control structure includes boundary protection and water-cutting curtain.

[0048] The boundary protection includes sealing of the corridor and gate chamber, protection with waterstops, and backfilling with crushed stone.

[0049] Sealing of corridors and gate chambers: Construct 37cm thick brick walls 23 inside the maintenance corridor, empty box, and pipeline corridor. Do not remove the formwork 27 at the bottom axis position. Construct 37cm thick brick walls 23 outside the formwork 27. Construct 10mm waterproof mortar, 4mm thick SBS asphalt waterproof membrane, and pressure strips on the outside of all brick walls 23 in sequence.

[0050] In this embodiment, buttress walls 24 are built on the left and right sides of the inner side of the brick wall 23 facing the corridor to strengthen the support of the brick wall 23. The slope of the buttress walls 24 is 1:1.

[0051] Waterstop protection: A wooden box 26 is made of wooden squares and wooden templates and is placed over the exposed waterstop 25. The wooden box 26 is fixed to the main structure with cement nails.

[0052] Crushed stone backfill: outside the gate chamber section 7, the original riverbed soil 22 is used for backfilling to the top elevation of the gallery, and then crushed stone 21 with a particle size of 200-300mm is compacted to a thickness of 500mm on the surface.

[0053] Within 5m of the upstream connecting section 6 and the downstream connecting section 8, crushed stone 21 with a particle size of 200-300mm is used for backfilling until it is flush with the existing concrete base slab 13.

[0054] The aforementioned boundary protection is used to protect existing structures and ensure safe passage through the flood season.

[0055] During the construction of the right span, in order to ensure that the cofferdam 2 of the left span of the second phase can be drained smoothly, it is necessary to construct the water cut-off curtain, thickened cushion layer 15, concrete strip 16, concrete panel 17, blind ditch 18 and water collection well 19 in advance within the right span.

[0056] In this embodiment, the cutoff wall is a three-axis mixing pile 14. In other embodiments, the cutoff wall can also be a high-pressure jet grouting pile or a plastic concrete anti-seepage wall.

[0057] The three-axis mixing piles 14 are driven in a row along the construction boundary line 3 of the left and right sides in the direction of the river. In this embodiment, the bottom elevation of the three-axis mixing piles 14 is -1m, the top elevation is below the original structure, and the distance between them and the already constructed concrete base plate 13 of the right side is greater than 2m.

[0058] Within gabion section 11 and riprap section 12, concrete strips 16 are laid along the river direction on the top of the three-axis mixing piles 14. The top elevation of the concrete strips 16 is 5cm higher than the adjacent structure, and the bottom elevation is 5cm lower than the adjacent structure.

[0059] A concrete panel 17 is constructed on top of the concrete strip 16. The concrete panel 17 extends towards the existing structure and is located above the gabion and riprap. The concrete panel 17, the concrete strip 16, and the triaxial mixing pile 14 are integrated into one unit. In this embodiment, the concrete panel 17 is 20cm thick and 6m wide, with a 100*100 steel mesh with a diameter of 10mm inside. A 6m wide geotextile and waterproof fabric 20 are laid underneath.

[0060] Within the paving section 9 and the stilling basin section 10, a thickened cushion layer 15 is constructed on the top of the three-axis mixing pile 14. The thickened cushion layer 15 extends towards the existing structure (i.e., the concrete base slab 13), connecting the top of the three-axis mixing pile 14 with the existing structure.

[0061] Within gate chamber section 7, a blind ditch 18 is constructed along the river at the bottom of the foundation pit between the existing structure (i.e., the fourth gate chamber 4) and the three-axis mixing pile 14. A sump well 19 is constructed at the end of the blind ditch 18. Because the top of the three-axis mixing pile 14 cannot be connected to the structure at the top of the deep foundation pit of the gate chamber, the blind ditch 18 and the sump well 19 are set up here for continuous pumping and drainage during the second phase of construction.

[0062] After the blind drain 18 and the water collection well 19 are completed, the foundation pit will be backfilled to the ground surface, and riprap will be placed along the edge of the structure for protection to prevent the bottom foundation of the constructed structure from being washed away during the flood season.

[0063] In this embodiment, the blind drain 18 is 0.5m away from the edge of the existing structural foundation, 0.5m deep, 0.5m wide at the bottom, and 1m wide at the top.

[0064] The three-axis mixing pile 14 serves two purposes: firstly, to protect the junction of the left and right sections during the flood season, and secondly, to act as a water-cutting curtain to prevent groundwater seepage during the second phase of construction.

[0065] Step S4: Finalization of Phase I construction.

[0066] Except for the gate between the fourth gate chamber 4 and the fifth gate chamber 5, which could not be installed, the remaining metal structures on the right side were all installed before the flood season of the following year. After installation, the right side cofferdam was removed for one flood season.

[0067] It should be noted that the installation of metal structures can also be carried out simultaneously with the construction of flood control structures.

[0068] Step S5: Phase II construction.

[0069] Construction of the left cofferdam 2 will begin after the flood season, and the left cofferdam 2 will overlap with the existing right cofferdam structure.

[0070] Within gabion section 11 and riprap section 12, the left-side cofferdam 2 is built on concrete strips 16 and concrete panels 17.

[0071] Within the paving section 9 and the stilling basin section 10, the left cofferdam 2 is built on the existing concrete base slab 13 and connected to the guide pier of the existing gate chamber.

[0072] After the left cofferdam 2 was constructed, the water level was lowered, and construction of the left side and left bank structure began. During the construction of the upstream connecting section 6 and the downstream connecting section 8, the gravel 21 was removed, and the concrete base slab 13, gabions, and riprap were constructed according to the design elevation. During the construction of the gate chamber section, the foundation pit was excavated and the three-axis mixing piles 14 in the area were broken down to the bottom elevation of the gallery. During the construction period, water was continuously pumped out from the sump well 19. The gallery and gate chamber sealing and waterstop protection of the fourth gate chamber 4 were removed, and the left and right gallery corridors were connected. Subsequent construction continued until the left side structure, left bank structure, and metal structure were all completed, after which the left cofferdam 2 was demolished.

[0073] During the construction of steps S2 to S5 above, it is also necessary to set up settlement monitoring points to monitor the settlement of the fourth gate chamber 4 and the fifth gate chamber 5 in stages, and switch the monitoring targets in stages. The specific methods are as follows.

[0074] Phase 1: Monitoring began 15 days after the completion of the bottom slab pouring of the gate chamber closest to the boundary in Phase 1 (i.e., the fourth gate chamber 4). A total of 3 monitoring points were set up on the bottom slab of the gate chamber, numbered BM1, BM2, and BM3, with BM1, BM2, and BM3 as the monitoring targets. In this phase, since the side walls of the fourth gate chamber 4 had not yet been constructed, only 3 monitoring points were set up on the bottom slab to monitor the settlement of the bottom slab.

[0075] Phase Two: Starting 15 days after the completion of the gate chamber sidewall pouring, two new monitoring points, numbered BM4 and BM5, will be set up above the gate chamber sidewall. The monitoring targets are BM1, BM2, BM3, BM4, and BM5. During this phase, the construction of the fourth gate chamber's four sidewalls will be completed, and joint monitoring of the bottom slab and sidewalls will begin.

[0076] Phase Three: After the removal of the first-phase cofferdam (i.e., right-side cofferdam 1) and the onset of the flood season, BM1, BM2, and BM3 are located underwater and cannot be monitored. Monitoring will then focus solely on BM4 and BM5, continuing until the construction of the bottom slab of the second-phase gate chamber closest to the boundary (i.e., the fifth gate chamber 5). During this phase, BM4 and BM5 will be used to monitor the settlement of the fourth gate chamber's sidewalls in real time during the flood season. If unexpected settlement occurs, emergency measures can be implemented and the structural parameters of the fifth gate chamber 5 can be adjusted. Although BM1, BM2, and BM3 are no longer in use, the data recorded in Phase One and Phase Two will provide a reference for the construction of the fifth gate chamber's bottom slab.

[0077] Phase Four: Starting 15 days after the completion of the bottom slab pouring of the gate chamber closest to the boundary in Phase II (i.e., the fifth gate chamber 5), three monitoring points will be set up on the bottom slab of the gate chamber, numbered BM6, BM7, and BM8, with BM4, BM5, BM6, BM7, and BM8 as the monitoring targets. During this phase, the side walls of the fifth gate chamber 5 have not yet been constructed. Therefore, the three monitoring points set up on the bottom slab, together with the two monitoring points on the side walls of the fourth gate chamber 4, will provide a reference for the construction of the side walls of the fifth gate chamber 5.

[0078] Phase Five: Starting 15 days after the completion of the sidewall pouring of the gate chamber closest to the boundary in Phase II (i.e., Gate Chamber 5), two new monitoring points, numbered BM9 and BM10, will be added above the sidewall of the gate chamber. The monitoring targets are BM4, BM5, BM9, and BM10. Monitoring will continue until step S5, after which permanent settlement monitoring points will be set up according to design requirements. During this phase, the sidewalls of Gate Chamber 4 and Gate Chamber 5 will be continuously monitored until construction is completed to ensure the smooth installation and normal operation of the gates.

[0079] The construction method provided by this invention can effectively protect the existing foundation of the right span structure, avoid excessive erosion at the junction of soft (original riverbed) and hard (concrete slab) ground during the flood season, prevent the river water from creating erosion channels that could affect the existing foundation structure, and ensure safe flood control. It also continuously monitors the settlement at the junction of the left and right span construction, so that structural parameters can be adjusted in time during the construction of the left span, and prevent the metal structure gate of the closure section from being affected by uneven settlement, thus ensuring its opening and closing operation. Furthermore, it solves the problem of the left span cofferdam being unable to pump water due to leakage in the gabion and riprap sections, and blocks the lateral seepage from the bottom of the existing structure into the left cofferdam, ensuring the dry trench construction within the second phase of the left span cofferdam.

[0080] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes, or alterations made by those skilled in the art using the disclosed technical content shall fall within the protection scope of the present invention.

Claims

1. A method for discontinuous construction of a steel dam gate, characterized in that, The construction is carried out in sections, with the left and right sections divided into Phase I and Phase II. A flood season separates the construction periods for Phase I and Phase II. After the completion of Phase I structural construction, flood control structure construction will commence to protect the existing Phase I structure during the flood season and prepare for dewatering of the Phase II cofferdam. The boundary between the left and right construction sections is located in the center of the river channel between two adjacent gate chambers. Phase I construction is on the right section, and Phase II construction is on the left section. Specific construction steps include: Step S1: Determine the construction boundary line and construction sequence for the left and right lanes; The lock chambers are numbered sequentially from the right bank to the left bank of the river, from the first to the eighth lock chamber. The construction boundary between the left and right banks is located between the fourth and fifth lock chambers. Step S2: Phase I construction; Construct the right-side cofferdam according to the design location and carry out the first phase of structure construction; The steel dam gate includes the onshore structure and the river channel structure. The river channel structure includes three parts: the upstream connecting section, the gate chamber section, and the downstream connecting section. The upstream connecting section includes the protective connecting section and the cover section. The downstream connecting section includes the stilling basin section, the apron section, the scour prevention section, and the reverse slope section. The upstream protective connecting section, the downstream apron section, and the reverse slope section are collectively referred to as the gabion section, and the scour prevention section is referred to as the rock-filled section. The first phase of construction includes the right bank structure and the upstream connecting section, lock chamber section and downstream connecting section within the right channel; Step S3: Construction of flood control structures; The flood control structure includes a water-cutting curtain, which is constructed in a row along the river direction from the boundary line between the left and right construction sections. Within the gabion section and the riprap section, concrete strips are laid along the river at the top of the cutoff curtain, and concrete panels extending towards the existing structure A are constructed at the top of the concrete strips. Within the cover section and stilling basin section, a thickened cushion layer is constructed on top of the cutoff curtain to connect the cutoff curtain with the existing structure B. Within the gate chamber section, a blind ditch is constructed along the river at the bottom of the foundation pit between the fourth gate chamber and the cutoff curtain. A water collection well is constructed at the end of the blind ditch. After the blind ditch and water collection well are constructed, the foundation pit is backfilled. Step S4: Finalization of Phase I construction; After the first phase of metal structure is installed, the cofferdam will be dismantled to allow for flood control. Step S5: Phase II construction; The second-phase cofferdam was constructed. In the gabion and riprap sections, it was built on concrete strips and concrete panels. In the cover section and stilling basin section, it was built on the existing concrete base slab and connected to the guide piers of the existing gate chamber.

2. The method for discontinuous construction of a steel dam gate according to claim 1, characterized in that, The medium-flood structure in step S3 also includes boundary protection, which includes sealing of the corridor and sluice chamber, waterstop protection and gravel backfilling. Corridor and gate chamber sealing: Brick walls are built inside the maintenance corridor, empty box, pipeline corridor and outside the template at the bottom axis position. Waterproof mortar layer, SBS asphalt waterproof membrane and pressure strip are applied to the outside of the brick wall in sequence. Waterstop protection: Install a wooden box on the outside of the exposed waterstop; Crushed stone backfill: The foundation pit outside the gate chamber section is backfilled with the original riverbed soil to the top elevation of the gallery, and then compacted with crushed stone on top; the upstream and downstream connecting sections are backfilled with crushed stone to be flush with the existing concrete base slab.

3. The method for discontinuous construction of a steel dam gate according to claim 1, characterized in that, The water-cutting curtain in step S3 is a three-axis mixing pile.

4. The method for discontinuous construction of a steel dam gate according to claim 1, characterized in that, In step S3, a steel mesh is installed inside the concrete panel, and geotextile and waterproof fabric are laid underneath.

5. The method for discontinuous construction of a steel dam gate according to claim 1, characterized in that, In step S5, after the second-phase cofferdam is built, the water level is lowered, the second-phase structure is constructed and the metal structure is installed, and the second-phase cofferdam is dismantled after completion.

6. A method for discontinuous construction of a steel dam gate according to any one of claims 1-5, characterized in that, During steps S2 to S5, temporary monitoring points are set up for sinking, and the monitoring targets are switched in stages, as follows: Phase 1: Monitoring will begin 15 days after the completion of the bottom slab of the gate chamber closest to the boundary in Phase 1. A total of 3 monitoring points will be set up on the bottom slab of the gate chamber closest to the boundary in Phase 1, numbered BM1, BM2 and BM3 respectively. The monitoring targets are BM1, BM2 and BM3. Phase Two: Starting 15 days after the completion of the pouring of the gate chamber sidewall closest to the boundary in Phase I, two new monitoring points will be set up above the gate chamber sidewall closest to the boundary in Phase I, numbered BM4 and BM5 respectively, and the monitoring targets will be BM1, BM2, BM3, BM4 and BM5. Phase 3: After the first phase of cofferdam removal, the flood season begins. Only BM4 and BM5 will remain as monitoring targets. Monitoring will continue until the second phase of construction of the gate chamber bottom slab closest to the boundary is completed. Phase 4: Starting 15 days after the completion of the pouring of the bottom slab of the gate chamber closest to the boundary in Phase 2, three monitoring points will be set up on the bottom slab of the gate chamber closest to the boundary in Phase 2, numbered BM6, BM7 and BM8 respectively, and the monitoring targets will be BM4, BM5, BM6, BM7 and BM8. Phase 5: Starting 15 days after the completion of the pouring of the gate chamber sidewall closest to the boundary in Phase 2, two new monitoring points will be set up above the gate chamber sidewall closest to the boundary in Phase 2, numbered BM9 and BM10 respectively. The monitoring targets are BM4, BM5, BM9 and BM10. Monitoring will continue until step S5. Subsequently, permanent settlement monitoring points will be set up according to the design requirements.

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