A method for predicting ice-water accumulation body bank collapse based on limit equilibrium method

Abstract

The application provides an ice-water accumulation body bank collapse prediction method based on the limit equilibrium method, relates to the technical field of reservoir safety, and obtains a complete topographic profile by topographic surveying on an ice-water accumulation body slope, constructs an MP model in combination with the mechanical parameters of the ice-water accumulation body slope, analyzes the stability of the ice-water accumulation body slope in the MP model by the limit equilibrium method, obtains an analysis result, and if the part with the stability less than 1 in the analysis result is located on water, the part with the stability less than 1 located on water is accumulated under water according to the underwater stability slope angle, bank collapse is simulated, a new topographic profile is obtained, the MP model is reconstructed, iteration is carried out, until the ice-water accumulation body slope cannot collapse, the overall width of the part with the stability less than 1 located on water is counted as the predicted bank collapse width, the problem that the existing ice-water accumulation body bank collapse prediction error is large is solved, and the application is suitable for ice-water accumulation body bank collapse prediction.

Description

Technical Field

[0001] This invention relates to the field of reservoir safety technology, and in particular to a method for predicting bank collapse of ice-water deposits based on the limit equilibrium method. Background Technology

[0002] The size of a reservoir is a crucial indicator of a hydropower station's regulation and power generation capabilities. Rapid water level fluctuations during reservoir impoundment impact the hydrogeological conditions within the reservoir area. Reservoir slopes, as a special type of water-bearing slope, are affected by rising or falling water levels. Previously unsubmerged slopes undergo soaking, erosion, and wet-dry cycles, gradually deteriorating the physical and mechanical properties of the slope's soil and rock, leading to shoreline retreat. After impoundment, unstable deposits can cause bank collapses. Reservoir bank collapses have adverse effects on the project and the surrounding socio-economic development. For example, bank collapses at the hydropower station's inlet and outlet can cause blockages; roads and railways along the reservoir banks within the collapsed area can be damaged; large amounts of soil can collapse, accumulating silt and reducing reservoir capacity, affecting normal operation; and bank collapses can also trigger other geological disasters such as landslides and debris flows, and cause surges, resulting in serious consequences.

[0003] Therefore, accurately predicting the location and width of bank collapse, such as the reservoir bank collapse prediction and erosion balance method disclosed in CN103310288A, allows for targeted measures to address bank collapse and ensure the safe operation of the reservoir.

[0004] Currently, there are many methods for predicting the width of bank collapses, but each has specific applicable conditions. Furthermore, current methods for predicting the width of reservoir bank collapses all predict from the perspective of the bank slope after it has already collapsed, only able to study the final width of the collapse and unable to reflect the characteristics of the collapse process.

[0005] Currently used methods for predicting bank collapse are mostly designed for loess areas, and their prediction errors for bank collapses caused by glacial meltwater deposition are relatively large. For example, the Kachukin method does not consider the stability of the bank slope below the prediction starting point; the Zolotarev method considers the impact of underwater deposition after bank collapse, but this method requires too many parameters, and the heterogeneous composition of glacial meltwater deposits makes it difficult to determine the appropriate parameter values; the two-stage method requires determining the stable slope angle above water, but the heterogeneous composition of glacial meltwater deposits also makes it difficult to determine the appropriate value. Glacial meltwater deposits are usually well cemented and difficult to stratify longitudinally, making bank slope structure methods unsuitable. Summary of the Invention

[0006] The technical problem solved by this invention: This invention provides a method for predicting the collapse of ice-water deposits based on the limit equilibrium method, which solves the problem of large prediction errors in existing ice-water deposits.

[0007] The technical solution adopted by this invention to solve the above-mentioned technical problems is: a method for predicting bank collapse of ice-water deposits based on the limit equilibrium method, comprising the following steps:

[0008] S1. Conduct topographic surveys on the slope of the glacial-water deposit to obtain a complete topographic profile. The slope of the glacial-water deposit includes the above-water portion and the underwater portion.

[0009] S2. Determine the mechanical parameters of the ice-water accumulation slope based on the experiment;

[0010] S3. Based on the complete topographic profile and the mechanical parameters of the glacial meltwater slope, construct the MP model;

[0011] S4. Stability analysis of the ice-water accumulation slope in the MP model is performed using the limit equilibrium method, and the analysis results are obtained.

[0012] S5. If the analysis results show that there is no part with stability less than 1 or that all parts with stability less than 1 are underwater, the ice-water deposit slope will not collapse. If the analysis results show that there is a part with stability less than 1 located above water, the part with stability less than 1 located above water will be deposited underwater according to the underwater stability slope angle to simulate the collapse, obtain a new topographic profile, and reconstruct the MP model.

[0013] S6. Repeat S4 and S5 until the ice-water deposit slope does not collapse.

[0014] S7. Calculate the overall width of the portion of the bank with a stability of less than 1 on the water surface, and use this as the width of the collapsed bank.

[0015] Furthermore, in S2, the mechanical parameters of the ice-water body include the cohesion of the ice-water accumulation, the internal friction angle, and the underwater stability slope angle.

[0016] Furthermore, in S4, the underwater stability slope angle is 1 to 3 degrees smaller than the internal friction angle.

[0017] Furthermore, in S4, the underwater stability slope angle is determined by the internal friction angle and the composition of the ice-water deposit.

[0018] Furthermore, in S4, the stability analysis of the ice-water accumulation slope in the MP model is performed using the limit equilibrium method and slope stability analysis software.

[0019] Furthermore, in S5, the step of stacking the unstable part underwater according to the underwater stability slope angle includes: obtaining the underwater volume of the unstable part by multiplying the volume of the unstable part by the stacking coefficient.

[0020] Furthermore, the packing factor is 0.7.

[0021] The beneficial effects of this invention are as follows: This invention provides a method for predicting bank collapse of glacial deposits based on the limit equilibrium method. By conducting topographic measurements on the slope of the glacial deposit, a complete topographic profile is obtained. An MP model is constructed based on the mechanical parameters of the glacial deposit slope. The stability of the glacial deposit slope in the MP model is analyzed using the limit equilibrium method. If the analysis results show no part with a stability less than 1, or if all parts with a stability less than 1 are underwater, the glacial deposit slope will not collapse. If the analysis results show parts with a stability less than 1 located above water, these parts are accumulated underwater according to the underwater stability slope angle to simulate bank collapse, obtaining a new topographic profile. The MP model is then reconstructed and iterated until the glacial deposit slope will not collapse. The overall width of the parts with a stability less than 1 located above water is counted as the predicted bank collapse width. This method solves the problem of large prediction errors in existing glacial deposit bank collapse prediction methods. Attached Figure Description

[0022] Figure 1 This is a flowchart illustrating a method for predicting bank collapse of ice-water deposits based on the limit equilibrium method provided by the present invention.

[0023] Figure 2 This is a schematic diagram showing that, in a method for predicting the collapse of ice-water deposits based on the limit equilibrium method provided by this invention, the portion with a stability of less than 1 is located on the water.

[0024] Figure 3 This invention provides a schematic diagram showing that the slope of a glacial deposit will not collapse in the stability analysis results of a method for predicting the collapse of a glacial deposit based on the limit equilibrium method.

[0025] In this context, ① represents the ice-water deposit, ② represents the bedrock, ③ represents the water, ④ represents the most unstable part of the analysis results, and ⑤ represents the part with a stability of less than 1 when deposited underwater according to the underwater stability slope angle. Detailed Implementation

[0026] This invention addresses the problem of large errors in existing prediction methods for glacial meltwater deposits by providing a method for predicting glacial meltwater deposit bank collapse based on the limit equilibrium method. Figure 1 As shown, it includes the following steps:

[0027] S1. Conduct topographic surveys on the slope of the glacial-water deposit to obtain a complete topographic profile. The slope of the glacial-water deposit includes the above-water portion and the underwater portion.

[0028] S2. Determine the mechanical parameters of the ice-water accumulation slope based on the experiment.

[0029] Specifically, the mechanical parameters of the ice-water body include the cohesion of the ice-water deposit, the internal friction angle, and the underwater stable slope angle. The value of the underwater stable slope angle mainly considers the soil particle composition factor, as shown in Table 1.

[0030] Table 1. Range of underwater stable slope angles for different soil types in ice-water deposits.

[0031]

[0032] This allows us to determine the range of values ​​for the underwater stable slope angle. To obtain a more accurate underwater stable slope angle, the value of the underwater stable slope angle should be 1 to 3 degrees smaller than the internal friction angle, provided that it meets the requirements of Table 1.

[0033] S3. Based on the complete topographic profile and the mechanical parameters of the glacial-water deposit slope, construct the MP model.

[0034] Specifically, the MP model is a profile model of the topographic environment of the slope of the glacial water deposit.

[0035] S4. The stability of the ice-water accumulation slope in the MP model is analyzed using the limit equilibrium method, and the analysis results are obtained.

[0036] Specifically, the stability analysis of the ice-water deposit slope in the MP model is carried out using the limit equilibrium method. Slope stability analysis software, such as Slide software, is used. The cohesion and internal friction angle of the ice-water deposit are input into the MP model, the limit equilibrium method is selected, and the software will use the limit equilibrium method as the calculation logic to search for the unstable parts.

[0037] The cohesion of a certain ice-water deposit is 35 kPa, the internal friction angle is 32 degrees, and the underwater stability slope angle is 30 degrees. Its stability analysis results are as follows: Figure 2 As shown, ① represents the ice-water deposit, ② represents the bedrock, ③ represents the water, and ④ represents the most unstable part of the analysis results, with a stability coefficient of 0.956.

[0038] S5. If the analysis results show that there is no part with stability less than 1 or that all parts with stability less than 1 are underwater, the ice-water deposit slope will not collapse. If the analysis results show that there is a part with stability less than 1 located above water, then the part with stability less than 1 located above water will be deposited underwater according to the underwater stability slope angle to simulate the collapse, obtain a new topographic profile, and reconstruct the MP model.

[0039] Specifically, Figure 2The analysis results show that the most unstable part has a stability coefficient of 0.956, which is less than 1, and includes a portion located above water. Therefore, there is a risk of bank collapse. The portion with a stability coefficient less than 1 located above water is deposited underwater according to the underwater stability slope angle to simulate bank collapse, obtain a new topographic profile, and reconstruct the MP model. The process of depositing the unstable part underwater according to the underwater stability slope angle includes obtaining the underwater volume of the unstable part by multiplying its volume by the deposit coefficient. The deposit coefficient is 0.7.

[0040] S6. Repeat S4 and S5 until the ice-water deposit slope does not collapse.

[0041] Specifically, stability iterative analysis is performed on the reconstructed MP model until the glacial meltwater slope does not collapse. The analysis results when the glacial meltwater slope does not collapse are as follows: Figure 3 As shown, the most unstable part in the analysis results has a stability coefficient of 1.014. Parts with a stability coefficient less than 1 and located above water accumulate underwater, as shown in the diagram. Figure 3 Therefore, since ⑤ in the equation, the bank collapse will not occur again, and the iteration terminates.

[0042] S7. Calculate the overall width of the portion of the bank with a stability of less than 1 on the water surface, and use it as the predicted bank collapse width.

[0043] Specifically, the overall width of all parts with stability less than 1 on the water during the iteration process is statistically determined, which is the simulated bank collapse width, and used as the predicted bank collapse width.

[0044] For a certain hydropower station reservoir, there are five ice-water accumulation bodies, denoted as T1, T2, T3, T4 and T5 respectively. The collapse width obtained by the ice-water accumulation body collapse prediction method based on the limit equilibrium method provided by this invention, the collapse width obtained by the existing two-segment method and the actual collapse width are shown in Table 2.

[0045] Table 2. Data on predicted and actual bank collapse widths.

[0046]

[0047] As shown in Table 2, the bank collapse width predicted by the present invention is closer to the actual bank collapse width.

Claims

1. A method for predicting bank collapse of ice-water deposits based on the limit equilibrium method, characterized in that, Includes the following steps: S1. Conduct topographic surveys on the slope of the glacial-water deposit to obtain a complete topographic profile. The slope of the glacial-water deposit includes the above-water portion and the underwater portion. S2. Determine the mechanical parameters of the ice-water accumulation slope based on the experiment; S3. Based on the complete topographic profile and the mechanical parameters of the glacial meltwater slope, construct the MP model; S4. Stability analysis of the ice-water accumulation slope in the MP model is performed using the limit equilibrium method, and the analysis results are obtained. S5. If the analysis results show that there is no part with stability less than 1 or that all parts with stability less than 1 are underwater, then the ice-water deposit slope will not collapse. If the analysis results show that the part with stability less than 1 is located above water, then the part with stability less than 1 located above water will be accumulated underwater according to the underwater stability slope angle to simulate bank collapse, obtain a new topographic profile, and reconstruct the MP model. S6. Repeat S4 and S5 until the ice-water deposit slope does not collapse. S7. Calculate the overall width of the portion of the bank with a stability of less than 1 on the water surface, and use it as the predicted bank collapse width.

2. The method for predicting bank collapse of ice-water deposits based on the limit equilibrium method according to claim 1, characterized in that, In S2, the mechanical parameters of the ice-water body include the cohesive force of the ice-water accumulation, the internal friction angle, and the underwater stable slope angle.

3. The method for predicting bank collapse of ice-water deposits based on the limit equilibrium method according to claim 2, characterized in that, In S4, the underwater stability slope angle is 1 to 3 degrees smaller than the internal friction angle.

4. The method for predicting bank collapse of ice-water deposits based on the limit equilibrium method according to claim 2, characterized in that, In S4, the underwater stability slope angle is determined by the internal friction angle and the composition of the ice-water deposit.

5. The method for predicting bank collapse of ice-water deposits based on the limit equilibrium method according to claim 1, characterized in that, In S4, the stability analysis of the ice-water accumulation slope in the MP model is performed using the limit equilibrium method and slope stability analysis software.

6. The method for predicting bank collapse of ice-water deposits based on the limit equilibrium method according to claim 1, characterized in that, In S5, the step of stacking the unstable part underwater according to the underwater stability slope angle includes: obtaining the volume of the unstable part underwater by multiplying the volume of the unstable part by the stacking coefficient.

7. A method for predicting bank collapse of ice-water deposits based on the limit equilibrium method according to claim 6, characterized in that, The packing factor is 0.7.

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