Hydraulic dam group operation method for controlling large-amplitude erosion and deposition of riverbed in compound river channel

Abstract

The invention provides an operation method of a hydraulic dam group for controlling a riverbed to greatly scour and deposit in a compound channel, which comprises the following steps of: alternately adopting a dynamic operation mode of dam collapse in a flood season, dam lifting in a non-flood season, dam lifting in a main channel and dam collapse in a beach land on the interyear by combining the interannual deposition characteristic and hydrological cycle of channel silt, and establishing a graded dredging mechanism at the same time; and regular monitoring and desilting are conducted on the upstream reach of the hydraulic dam located on the upstream, and normalized maintenance and desilting are conducted on the surface of the hydraulic dam structure. According to the running mode of dam collapse in the annual flood season and dam rising in the non-flood season, water conservation in the non-flood season with relative water shortage can be guaranteed, manual intervention is not adopted in the flood season with relatively abundant water, flood discharge and sand flushing of the riverway are relatively natural, it is guaranteed that the annual water amount of the riverway is considerable, and the water quality of the riverway is improved. A natural means is utilized to ensure that riverbed siltation is not excessively developed; the running mode of the full-year main groove dam rising and beach land dam collapse ensures that the water source is reserved in the flat water year or the dry water year, and meanwhile, the easily-deposited beach land part is subjected to water flushing. By adopting the hydraulic dam group operation mode provided by the invention, great erosion and deposition of a riverbed can be relieved.

Description

Technical Field

[0001] The invention relates to the technical field of hydraulic sediment removal in water conservancy projects, and in particular to a method for operating a hydraulic dam group in a compound river channel for controlling large-scale scouring and silting of a riverbed. Background Art

[0002] The construction of dams is a common engineering measure used in the management of small and medium-sized rivers. While providing flood control and water supply for irrigation, they also create landscape effects and improve the ecological environment of water systems. In recent years, a number of new low-head dams have emerged, including steel dams, flap gates, air shield gates, hydraulic dams, and hinged dams. Each gate of flap gates, hydraulic dams, and hinged dams can be raised and lowered independently, allowing for operation in various combinations. From the perspective of river habitat health, the construction and operation of new dams on alluvial rivers will inevitably disrupt the long-established water-sediment balance, leading to changes in the evolution of the riverbed. These changes in the patterns of water and sediment movement may not only affect the safety of river flood flow and the operation of dams, but may also impact the river's habitat.

[0003] Different from non-overflow, bottom-opening high-head dams and traditional fixed weirs for drainage and sand removal, the new weirs are rotating flat gates that can quickly raise the dam to store water and overflow water, or lower all (dam collapse) or part of the gates (segmented dam collapse) to be flush with the riverbed to discharge floodwater and flush sand. Therefore, alluvial rivers may show riverbed evolution characteristics different from those under the action of traditional weirs, but there is currently little research on operation plans. In fact, local riverbed siltation will affect the flood control safety of the river channel, and riverbed scouring and silting near the local hydraulic dam area is related to the normal and safe operation of the hydraulic dam. Therefore, it is necessary to fully study the riverbed scouring and silting conditions under different operation modes of the hydraulic dam group, whether it is the entire river section or a local key area, and based on the consideration of river flood control safety and hydraulic dam operation safety, a hydraulic dam group operation mode that controls large-scale riverbed scouring and silting is proposed. Summary of the Invention

[0004] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is to provide a method for operating a hydraulic dam group in a compound river channel to control large-scale scouring and silting of the riverbed, so that the impact of the scouring and silting of the riverbed caused during the operation of the hydraulic dam group on river flood control, habitat protection and the normal operation of the hydraulic dam is minimized to the greatest extent.

[0005] A method for operating a hydraulic dam group in a complex river channel to control large-scale scouring and silting of the riverbed.

[0006] It includes: combining the inter-annual sedimentation characteristics of the river channel with the hydrological cycle, and adopting a dynamic operation mode of collapsing the dam in the flood season and raising the dam in the non-flood season, and raising the dam in the main channel and collapsing the dam on the beach in alternating years. At the same time, a graded dredging mechanism is established, and regular monitoring and dredging of the upstream river section of the hydraulic dam located upstream is carried out, and routine maintenance and dredging of the surface of the hydraulic dam structure is carried out.

[0007] Furthermore, warning thresholds for sediment content and siltation are set during operation. If a flood with a large sediment content occurs and the warning threshold is triggered, and significant sedimentation occurs in local or entire river sections, local precision dredging will be given priority. If the siltation range exceeds 30% of the entire river section, a full-section dam collapse method will be used during the flood season to flush sediment in the river channel, and the flushing effect will be monitored simultaneously.

[0008] Furthermore, the inter-annual alternation adopts the operation mode of dam collapse in flood season and dam raising in non-flood season, and dam raising in main channel and dam collapse in beach land, which specifically includes:

[0009] In the first year of operation, the dam will be collapsed during the flood season and raised during the non-flood season. The flood season is defined as June to September each year. During the non-flood season, the dam elevation must be controlled at 0.5m below the design flood level.

[0010] In the second year of operation, the main channel dam will be raised and the beach dam will collapse. The main channel dam will be raised to a height that meets the requirements for navigation or irrigation water intake. After the beach dam collapses, the beach surface water velocity must be maintained at ≥ 0.3 m / s to prevent sediment retention.

[0011] Repeat the operation mode from the first to the second year from the third to the fourth year, and so on for the subsequent years;

[0012] The alternating effects of the two operating modes will be evaluated every five years, and the operating cycle or parameters will be dynamically adjusted according to changes in riverbed scouring and deposition.

[0013] Furthermore, the hydraulic dam group adopts cascade linkage control, and the operating status of the upstream dam body and the downstream dam body has a linkage response relationship. When the upstream dam body performs the dam collapse operation, the downstream dam body needs to complete the dam collapse preparation 1-2 hours in advance to avoid the formation of instantaneous water level difference between the dams and cause abnormal accumulation of sediment.

[0014] Furthermore, the graded dredging mechanism is divided into three levels according to the degree of siltation. The first-level dredging targets the surface of the hydraulic dam structure and the area within 5 meters around it, and is carried out once a quarter; the second-level dredging targets the main channel area of ​​the upstream river section, and is carried out once every six months; the third-level dredging targets the beaches and tributary confluences of the entire river section, and is carried out once a year during the non-flood season. After dredging, it is necessary to ensure that the flow section of the main channel is restored to more than 90% of the design standard.

[0015] Furthermore, during the main channel dam raising operation, the water flow velocity in the main channel needs to be monitored in real time. When the flow velocity is lower than 0.8m / s, the diversion holes reserved in the dam body are opened to reduce the siltation of the main channel by locally increasing the flow velocity. The number of diversion holes opened is dynamically adjusted according to the flow velocity monitoring data.

[0016] Furthermore, during the full-section dam collapse process, a segmented and gradual dam collapse method is required, with the dam collapsed from upstream to downstream at intervals of 30 minutes. At the same time, a sediment monitoring point is set downstream of the dam body. When the average sediment content of the section is monitored to drop to 5kg / m 3 When the scouring pressure is below 30000, the scouring is judged to have reached the standard and the dam collapse operation is stopped.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] If the hydraulic dam group continues to collapse, the project benefits will be almost unattainable. If it continues to raise the dam, it will cause riverbed siltation, especially siltation in the sub-river section where the upstream hydraulic dam is located. The operation mode of collapsing the dam during the flood season and raising the dam during the non-flood season can ensure that water sources are conserved during the relatively water-scarce non-flood season, and no artificial intervention is taken during the flood season when the water volume is relatively abundant, allowing the river channel to discharge floodwaters and flush sand relatively naturally, which not only ensures that the water volume in the river channel is relatively considerable throughout the year, but also uses natural means to ensure that riverbed siltation does not develop excessively; the operation mode of raising the dam in the main channel and collapsing the dam in the beach throughout the year ensures that water sources are retained in normal water years or dry water years, and at the same time, water is flushed on the beach areas that are prone to siltation; on this basis, artificial silt removal is carried out on key areas, namely the river section in front of the upstream hydraulic dam and the surface of the hydraulic dam structure. Therefore, the operation mode of the hydraulic dam group proposed in the present invention is conducive to alleviating the significant scouring and silting of the riverbed. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings illustrate various embodiments generally by way of example and not limitation, and together with the description and claims, serve to explain embodiments of the invention. Where appropriate, the same reference numerals are used throughout the drawings to refer to the same or similar parts. Such embodiments are illustrative and are not intended to be exhaustive or exclusive of the embodiments of the present apparatus or method.

[0020] Figure 1 The cumulative riverbed scouring and deposition volumes predicted by mathematical simulations for the following projects using different single operation modes are as follows: (a) the entire river section; (b) the surface of the hydraulic dam structure; (c) the beach; and (d) the main channel. The dashed lines with hollow circles in the figure represent the continuous dam collapse mode; the dashed lines with hollow diamonds represent the continuous dam raise mode; the dashed lines with plus signs represent the continuous dam collapse mode (flood season and non-flood season raise mode); and the dashed lines with hollow triangles represent the main channel raise mode (flood dam raise mode).

[0021] Figure 2Figure 2 is the cumulative riverbed scouring and silting volume predicted by mathematical simulation when the following projects adopt the combined operation mode of the embodiments of the present invention (i.e., the operation mode of alternating annually adopting the dam collapse during the flood season and dam raising during the non-flood season, and the dam raising in the main channel and collapsing on the beach): (a) the entire river section; (b) the surface of the hydraulic dam structure; (c) the beach; (d) the main channel; the dotted and dashed lines with hollow circles in the figure indicate the operation mode of adopting the dam collapse during the flood season and dam raising during the non-flood season in the first year, and the main channel raising and collapsing on the beach in the second year; the dotted and dashed lines with plus signs indicate the operation mode of adopting the main channel raising and collapsing on the beach in the first year, and the flood season and dam raising during the non-flood season in the second year. DETAILED DESCRIPTION

[0022] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0023] Taking a hydraulic dam group (1# to 15# hydraulic dams, a total of 15 dams) built on a plain river with a compound section as an example, the technical solution of the present invention is further described in detail.

[0024] The 15 hydraulic dams are located along a river section approximately 80 km long. This stretch of river is winding and has numerous bends; it is a typical duplex channel, with a main channel width of approximately 20 to 80 meters and a combined width of 150 to 290 meters on both sides of the river. The flood season is from June to September, and the non-flood season is from October to May. Each of the 15 hydraulic dams consists of 6-meter-wide gates connected in series. The gates installed in the main channel are 3.5 to 5 meters high, while the gates in the riverbed are all 2 meters high, with gate thicknesses ranging from 0.12 to 0.40 meters. Each hydraulic dam primarily consists of a main channel protection section, an upstream cover section, a hydraulic dam section, a stilling basin section, and a downstream floodplain section.

[0025] Data from hydrological stations along the main stream show that this section of the river exhibits riverbed scour under relatively natural conditions (no hydraulic dams built or collapsed). However, continuous dam collapse prevents the hydraulic dams from fully utilizing their water storage function.

[0026] By establishing a two-dimensional mathematical model and using the measured data of the river channel to calibrate and verify the model parameters, the model was used to predict the scouring and silting of the riverbed under different operating modes. The complex river channel was divided into three parts: the main channel, the beach, and the surface of the hydraulic dam structure to consider the specific scouring and silting distribution of the river channel. The prediction results show (see Figure 1 ):

[0027] (1) When the continuous dam collapse mode is adopted, the river channel shows net scouring (most significant), among which the main channel scouring (most significant), beach siltation (most significant), and hydraulic dam structure surface siltation (most significant);

[0028] (2) When the continuous dam raising operation mode is adopted, the river channel shows net siltation (most significant), among which the main channel is silted, the beach is slightly silted, and the surface of the hydraulic dam structure is slightly silted;

[0029] (3) When the dam collapses during flood season and rises during non-flood season, the riverbed shows net scouring, including scouring of the main channel, silting of the beach, and silting of the surface of the hydraulic dam structure (significant);

[0030] (4) When the continuous main channel dam raising and beach collapse mode is adopted, the riverbed shows net siltation, among which the main channel siltation (most significant), beach scouring (most significant), and slight siltation on the surface of the hydraulic dam structure.

[0031] When the composite river channel is divided into sub-river sections along the locations of the hydraulic dams in the hydraulic dam group:

[0032] (1) When the continuous dam collapse mode is adopted, there is no obvious pattern among the sub-sections of the river;

[0033] (2) When the continuous dam raising operation mode was adopted, the upstream sub-river section was significantly silted up, and the siltation in the sub-river section where the No. 1 hydraulic dam was located was the most significant;

[0034] (3) When the dam collapses during the flood season and rises during the non-flood season, there is no obvious pattern among the various sub-sections of the river;

[0035] (4) When the main channel dam-raising and beach collapse operation mode is adopted, the upstream sub-river section is obviously silted up, among which the siltation of the sub-river section where the No. 1 hydraulic dam is located is the most significant.

[0036] Based on the above results, we can know that: (1) Although the continuous dam raising operation mode can make the most of the hydraulic dam group, this operation mode will lead to the siltation of the riverbed of the entire river section (including the beach and the main channel), especially the siltation of the upstream sub-river section of the 1# hydraulic dam is significant, thereby increasing the flood control pressure of the river channel. Therefore, from a long-term perspective, this operation mode is not ideal; (2) Although the operation mode of the main channel dam raising and the beach collapse, and the dam collapse in the flood season and the dam raising in the non-flood season still causes siltation of the entire river section or sediment accumulation on the surface of the hydraulic dam structure, the scouring and silting trends of the main channel and the beach are exactly opposite under these two operation modes, and they can compensate each other under certain conditions. This indirectly verifies that the alternating operation of the flood season dam collapse and the non-flood season dam raising, and the main channel dam raising and the beach collapse, and the silt removal and dredging of the surface of the hydraulic dam structure and the upstream sub-river section can reasonably control the large-scale scouring and silting of the riverbed.

[0037] In addition, the above mathematical model was used to predict the riverbed evolution process of alternating the "dam collapse in flood season and dam raising in non-flood season" and "dam raising in main channel and dam collapse on beach" operation modes for one year each, and the water and sediment conditions were consistent in the two years. Figure 2 The cumulative riverbed scouring and deposition volume changes under the above two working conditions are shown.

[0038] Depend on Figure 2 It can be seen that when the operation mode of “dam collapse during flood season and dam raising during non-flood season” was adopted in the first year, the amount of riverbed sedimentation in the first year was about 33,000 cubic meters; when the operation mode of “dam raising in main channel and dam collapse in beach area” was adopted in the first year, the amount of riverbed sedimentation in the first year was about 66,000 cubic meters, and the total sedimentation was about 99,000 cubic meters. It should be noted here that the reason why the overall riverbed sedimentation occurred when the “dam collapse during flood season and dam raising during non-flood season” was adopted in the first year was that there was a flood with significant water and sand in the non-flood season (October). The dam was raised to store water during the non-flood season, resulting in sedimentation in the main channel, and significant sedimentation also occurred in the upstream sub-river section of the 1# hydraulic dam in the longitudinal direction of the river. Although under such circumstances, Figure 2 The superiority of the "alternating annual operation method of collapsing the dam during flood season and raising it during non-flood season, and raising the dam in the main channel and collapsing it on the beach" was demonstrated. Under these two operating conditions, the cumulative riverbed sedimentation over the entire river section over the two years was approximately 79,000 cubic meters and 95,000 cubic meters, respectively. This reduced riverbed sedimentation by a maximum of 20%, effectively controlling significant erosion and sedimentation. This was without considering desilting the upstream hydraulic dams, particularly the upstream section of the first hydraulic dam, or the surfaces of the hydraulic dam structures.

[0039] First, we analyze the operating conditions of "collapse the dam during the flood season and raise the dam during the off-flood season in the first year, and raise the main channel and collapse the dam on the beach in the second year." The hydraulic dam structure experienced significant siltation in the first year, but only minor siltation in the second year. The beach accumulated approximately 28,000 cubic meters of silt in the first year, but only about 11,000 cubic meters in the second year. The main channel experienced scouring of approximately 14,000 cubic meters in the first year, but about 33,000 cubic meters in the second year. Overall, the extent of scouring and silting in various sections of the riverbed decreased in the second year, or even shifted from scouring to siltation, indicating the effectiveness of alternating these two operating modes. The main riverbed siltation during these two years occurred primarily on the hydraulic dam structure surface and the beach, with the most severe siltation occurring in the upstream subsection of the 1# hydraulic dam. Consideration should be given to desilting and dredging the hydraulic dam structure surface and this subsection.

[0040] Next, we analyzed the operating conditions of "raising the main channel and collapsing the beach in the first year, and collapsing the dam during the flood season and raising the dam during the off-flood season" in the second year. Approximately 5,000 cubic meters of sedimentation accumulated on the surface of the hydraulic dam structure in the first year, but only 4,000 cubic meters in the second year, with the cumulative riverbed sedimentation following a similar pattern to the first year. Approximately 51,000 cubic meters of scour occurred on the beach in the first year, but only approximately 9,000 cubic meters in the second year. Approximately 113,000 cubic meters of siltation accumulated in the main channel in the first year, but only approximately 35,000 cubic meters in the second year. The extent of scouring and sedimentation in each of these sections of the riverbed was effectively controlled in the second year, demonstrating the effectiveness of alternating the two operating modes. However, under these operating conditions, significant sedimentation, totaling approximately 76,000 cubic meters, continued over two years in the upstream section of the 1# hydraulic dam. This was due to the riverbed rising in the upstream section after the first year of operation, which led to a rise in the erosion base level in the upstream section. This reduced the longitudinal gradient of the riverbed in some sections, and decreased the sediment-carrying capacity of the water flow. Consequently, despite the hydraulic dam collapse during the second flood season, significant sedimentation still occurred, and the sediment load of the floodwaters propagating downstream was reduced. During these two years, riverbed sedimentation primarily occurred in the upstream section of the 1# hydraulic dam, necessitating manual dredging of this section.

[0041] In summary, alternating annual dam collapse during flood season and dam raising during non-flood season, and dam raising in the main channel and collapsing in the beach, can effectively control riverbed erosion and sedimentation. Considering the significant negative impact of riverbed sedimentation on flood control, and the ease of dredging and desilting, regular desilting and dredging of the hydraulic dam structure and the upstream sub-river section of the No. 1 hydraulic dam can be conducted, if conditions permit. Therefore, the following specific operational recommendations can be obtained:

[0042] How the first year will run:

[0043] If the hydraulic dam group is activated during the flood season (June to September), it will be operated by dam collapse;

[0044] After entering the non-flood season (October to May of the following year), the dam is raised for operation;

[0045] During the non-flood season, if a flood is predicted upstream of the No. 1 hydraulic dam, with a peak flow greater than 80m 3 / s and a sediment concentration exceeding 3kg / m 3, the dam will be collapsed;

[0046] During the non-flood season, if a flood occurs upstream of the No. 1 hydraulic dam, and the peak flow is greater than 80m³ / s and the sediment concentration exceeds 3kg / m³, but the dam collapse operation is not carried out in time due to untimely forecasts, the full-section dam collapse operation will be carried out during the flood season of the following year to achieve sediment flushing along the entire river channel.

[0047] During the non-flood season, based on on-site monitoring, if necessary, dredging will be carried out on the upstream river section of the No. 1 hydraulic dam and the surface of the 15 hydraulic dam structures.

[0048] How the second year will run:

[0049] From the beginning of the flood season to the end of the non-flood season (June to May of the following year), the main channel raising dam and beach collapse dam operation mode is adopted;

[0050] After entering the non-flood season, if necessary, the river section upstream of the No. 1 hydraulic dam will be dredged.

[0051] How the third year will run:

[0052] Repeat the operation method of the first year;

[0053] If the third-year monitoring reveals that the siltation level of the entire river channel affects flood control safety, the full-section dam collapse operation will be adopted during the flood season until the riverbed siltation level no longer affects flood control safety. The dam will still be raised during the non-flood season.

[0054] The recommended operating mode for the first year's non-flood season still applies.

[0055] The fourth year operation mode:

[0056] Repeat the operation method for the second year.

[0057] If the monitoring in the fourth year finds that the siltation level of the entire river channel affects flood control safety, the full-section dam collapse operation will be adopted during the flood season until the riverbed siltation level has no impact on flood control safety. In the non-flood season, the main channel dam raising and beach dam collapse operation mode will still be adopted.

[0058] The above is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with this technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the scope of protection of the present invention.

Claims

1. A method for operating a hydraulic dam group in a complex river channel to control large-scale scouring and silting of the riverbed, characterized in that: include: In combination with the inter-annual sedimentation characteristics of the river channel and the hydrological cycle, a dynamic operation mode of dam collapse in flood season and dam raising in non-flood season, and dam raising in the main channel and dam collapse on the beach is adopted in alternating years. At the same time, a graded dredging mechanism is established, and regular monitoring and dredging are carried out on the upstream river section of the hydraulic dam located upstream, and routine maintenance and dredging are carried out on the surface of the hydraulic dam structure.

2. The method for operating a hydraulic dam group for controlling large-scale scouring and silting of the riverbed in a complex river channel according to claim 1, characterized in that: During operation, warning thresholds for sediment content and siltation are set. If a flood with a high sediment content occurs and the warning threshold is triggered, and significant sedimentation occurs in local or entire river sections, local precision dredging will be given priority. If the siltation range exceeds 30% of the entire river section, a full-section dam collapse method will be used during the flood season to flush sediment in the river channel, and the flushing effect will be monitored simultaneously.

3. The method for operating a hydraulic dam group for controlling large-scale scouring and silting of the riverbed in a complex river channel according to claim 1, characterized in that: The inter-annual alternation adopts the operation mode of dam collapse in flood season and dam raising in non-flood season, and dam raising in main channel and dam collapse in beach land, specifically including: In the first year of operation, the dam will be collapsed during the flood season and raised during the non-flood season. The flood season is defined as June to September each year. During the non-flood season, the dam elevation must be controlled at 0.5m below the design flood level. In the second year of operation, the main channel dam will be raised and the beach dam will collapse. The main channel dam will be raised to a height that meets the requirements for navigation or irrigation water intake. After the beach dam collapses, the beach surface water velocity must be maintained at ≥ 0.3 m / s to prevent sediment retention. Repeat the operation mode from the first to the second year from the third to the fourth year, and so on for the subsequent years; The alternating effects of the two operating modes will be evaluated every five years, and the operating cycle or parameters will be dynamically adjusted according to changes in riverbed scouring and deposition.

4. The method for operating a hydraulic dam group for controlling large-scale scouring and silting of the riverbed in a complex river channel according to claim 1, characterized in that: The hydraulic dam group adopts cascade linkage control, and the operating status of the upstream dam body and the downstream dam body has a linkage response relationship. When the upstream dam body performs the dam collapse operation, the downstream dam body needs to complete the dam collapse preparation 1-2 hours in advance to avoid the formation of instantaneous water level difference between the dams and cause abnormal accumulation of sediment.

5. The method for operating a hydraulic dam group for controlling large-scale scouring and silting of the riverbed in a complex river channel according to claim 1, characterized in that: The graded dredging mechanism is divided into three levels according to the degree of siltation. The first level dredging targets the surface of the hydraulic dam structure and the area within 5 meters around it, and is carried out once a quarter; the second level dredging targets the main channel area of ​​the upstream river section, and is carried out once every six months; the third level dredging targets the beaches and tributary confluences of the entire river section, and is carried out once a year during the non-flood season. After dredging, it is necessary to ensure that the main channel flow section is restored to more than 90% of the design standard.

6. The method for operating a hydraulic dam group for controlling large-scale scouring and silting of the riverbed in a complex river channel according to claim 1, characterized in that: During the main channel dam raising operation, the water flow velocity in the main channel needs to be monitored in real time. When the flow velocity is lower than 0.8m / s, the diversion holes reserved in the dam body are opened to reduce the siltation of the main channel by locally increasing the flow velocity. The number of diversion holes opened is dynamically adjusted according to the flow velocity monitoring data.

7. The method for operating a hydraulic dam group for controlling large-scale scouring and silting of the riverbed in a complex river channel according to claim 1, characterized in that: During the full-section dam collapse process, a step-by-step dam collapse method is required, with the dam collapsed from upstream to downstream every 30 minutes. At the same time, a sediment monitoring point is set up downstream of the dam body. When the average sediment content of the section is monitored to drop to 5kg / m 3 When the scouring pressure is below 30000, the scouring is judged to have reached the standard and the dam collapse operation is stopped.

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