Method for testing and calculating wave pressure on inclined dam surface under action of landslide surge

Abstract

The application provides a method for testing and calculating wave pressure of an inclined dam surface under the action of a landslide surge, comprising the following steps: (1) according to the Froude similarity criterion, a large-scale three-dimensional physical model containing complex terrain, a river channel, an inclined dam body and a hydraulic gate is constructed in proportion; (2) the hydraulic control system is used to simulate the landslide body entering water under different working conditions to carry out the test; (3) the test data are processed to obtain the characteristics that the wave pressure above the water surface sharply attenuates and the wave pressure below the water surface is relatively uniform; (4) a dimensionless mathematical model is established; (5) the test data of each working condition are substituted into the mathematical model to carry out multiple nonlinear regression analysis, and a calculation coefficient is fitted to finally establish an explicit calculation formula for calculating the maximum wave pressure of the inclined dam surface. The application solves the technical problem that the existing empirical formula is inaccurate in predicting the landslide surge wave pressure because it is based on a vertical dam body or a wind wave condition, and provides a reliable basis for evaluating the safety threat of the surge to the dam and the protection design.

Description

Technical Field

[0001] This invention relates to the field of landslide surge chain disaster research in the fields of hydraulic rock mechanics and disaster prevention and mitigation, and particularly to a method for testing and calculating wave pressure on inclined dam surfaces under the action of landslide surges. Technical Background

[0002] With the rapid development of hydropower and water conservancy projects in my country, a number of large-scale and technologically complex high dams and reservoirs have been built in the southwest region. The geological environment of this area is extremely complex, with frequent and intense earthquakes, abundant rainfall, and frequent and significant fluctuations in reservoir water levels, making it prone to geological disasters such as landslides.

[0003] Compared to general landslide disasters, the consequences of reservoir-type landslide instability are particularly severe. In particular, landslides on land often possess high gravitational potential energy, which, upon entering the reservoir area, strongly compresses the water, transferring enormous kinetic energy to the water and generating swells that propagate along the river channel. Because reservoirs are semi-enclosed water bodies, the narrow river channels restrict the rapid dissipation of swell energy, causing the swells to maintain high peaks even as they reach near-shore areas, severely hindering navigation.

[0004] Furthermore, landslide sources are usually close to the dam site or the opposite bank, resulting in limited wave height and energy attenuation during the propagation of the resulting surge. When the surge reaches the dam, it will exert a strong impact on hydraulic structures, seriously threatening the safety and stability of the dam. For example, the Malpasset dam collapse in France on December 2, 1959, caused by continuous heavy rainfall, led to a rapid rise in the reservoir water level to its limit. The gates failed to open in time to release floodwaters, and the presence of weak interlayers and fault zones in the dam foundation ultimately resulted in the dam's instability and collapse, causing a major disaster that claimed 423 lives. Therefore, accurately measuring the wave pressure generated by landslide surges on inclined dam surfaces is of significant practical importance for revealing the causes of disasters and achieving disaster prediction.

[0005] Currently, the problems include: ① Research on the impact of landslide surges on structural loads mainly focuses on hydrostatic pressure; ② Existing empirical formulas are based on the assumption of a vertical dam or wind and wave conditions; ③ Existing physical experiments mostly rely on two-dimensional flume tests to obtain data, which are often based on simplified assumptions and cannot accurately reflect the complexity of actual terrain and river conditions. In summary, existing methods do not fully consider the nonlinear and long-period characteristics of landslide surges and the influence of dam face inclination angles, resulting in significant deviations between theoretical predictions and actual conditions, and failing to meet the design and evaluation requirements for high dam safety protection. Summary of the Invention

[0006] The purpose of this invention is to provide a method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges, which addresses the problems existing in the prior art. This method can accurately predict the wave pressure distribution on the inclined dam surface under the action of surges, and can be directly used to evaluate the surge resistance of existing dams. It also provides key technical parameters and theoretical support for the safety design and risk prevention of new dams.

[0007] Therefore, the present invention adopts the following technical solution:

[0008] A method for testing and calculating wave pressure on an inclined dam surface under the action of landslide surge, characterized by the following steps:

[0009] (1) Based on the Froude similarity criterion, a large-scale three-dimensional physical model of landslide surge considering complex terrain is constructed according to the scale. The model includes a landslide test platform, a river channel model, a dam model, a hydraulic gate model and a control platform. The dam surface inclination angle and roughness of the dam model are simulated according to the actual engineering.

[0010] (2) The test was carried out by simulating the landslide body entering the water under different working conditions through the hydraulic control system. The wave pressure time history data during the generation, propagation and impact of the dam surface were collected synchronously using a high-precision water pressure sensor array deployed on the inclined dam surface.

[0011] (3) Process the test data, obtain the vertical distribution law of wave pressure along the dam axis, and analyze the characteristics of the wave pressure attenuating sharply above the water surface and the wave pressure distribution being relatively uniform below the water surface;

[0012] (4) Define relative wave pressure as the dependent variable and Froude number of the sliding body entering the water, relative wave amplitude, relative run-up, and wave incident angle as independent variables to establish a dimensionless mathematical model;

[0013] (5) Substitute the test data of each working condition into the mathematical model to perform multivariate nonlinear regression analysis, fit the calculated coefficients, and finally establish the explicit calculation formula for calculating the maximum wave pressure on the inclined dam surface.

[0014] This invention first constructs a large-scale three-dimensional physical model testing system capable of highly reproducing the engineering prototype. This system is the foundation for achieving accurate testing, and its core lies in the detailed simulation of complex terrain and dam structures. Furthermore, the model adopts the following scheme:

[0015] (1) Model similarity criterion: Strictly follow the Froude similarity criterion and select a geometric scale of 1:100 to 1:200 (preferably 1:150) to ensure that the model and the prototype are similar in fluid motion under gravity.

[0016] (2) Topographic Reproduction Technology: The river model adopts a composite construction process combining the cross-section panel method and the contour line method. First, cross-section panels are set at 0.5m intervals to outline the main contour of the river channel; then, in key areas such as abrupt topographic changes, the opposite bank of landslides, and in front of dams, contour lines are drawn at 0.05m intervals, and highly malleable materials are used for fine shaping to ensure the authenticity of micro-topography such as underwater slopes and riverbed undulations. The river model is mainly constructed of cement, yellow sand, red bricks, and steel bars. The inner wall of the river channel is plastered with white cement to reduce the impact of the model's side wall roughness on the water flow and ensure the similarity of wave propagation.

[0017] (3) Precise simulation of dam body and structure: The dam model is cast strictly according to the mix ratio of the actual project (such as C25 concrete) to ensure that its surface roughness is consistent with the prototype, thereby accurately reflecting the interaction between waves and the dam surface, such as friction and rolling. The hydraulic gate model and the dam body adopt a one-time positioning and casting technology, which eliminates leakage and structural strength problems caused by joints, and ensures the stability and authenticity of the model under repeated impacts.

[0018] (4) Multi-parameter controllable landslide simulation device: The core of the landslide test platform is an adjustable sliding box driven by a hydraulic control system. The system can precisely control the lifting angle of the sliding box (simulating the sliding surface inclination angle) and the opening speed of the gate, thereby achieving precise control of the speed at which the sliding body enters the water and the initial acceleration, so as to simulate landslide scenarios with different degrees of agitation.

[0019] Furthermore, the experiment includes the following steps:

[0020] (1) The sliding material that slid into the water in the previous test was retrieved and repositioned on the landslide test platform. The sliding box was placed horizontally and the gate was closed. The accumulation pattern of the sliding material was set according to the test conditions, and the sliding box was adjusted to the predetermined tilt angle by the hydraulic oil pump.

[0021] (2) Adjust the river water level to the specified depth for the test. After the water surface stabilizes, calibrate and zero all wave pressure sensors.

[0022] (3) Calibrate and start the high-speed camera system, and start synchronous recording after focusing is completed;

[0023] (4) Start the motor and open the sliding box stop door. The slide body begins to slide down, and the test is officially started.

[0024] (5) The data acquisition system will automatically stop recording for one period of time, and the camera equipment will be manually stopped after the test.

[0025] (6) Clean up the test site, prepare for the next set of tests, and process and analyze the collected data.

[0026] This invention also establishes a multi-dimensional, high-response wave pressure data acquisition scheme.

[0027] (1) In order to capture the instantaneous and high-frequency dynamic pressure response of the surge impact, the present invention further designed a multi-dimensional sensor deployment scheme: Sensor selection and layout: a water pressure sensor array is installed in a slot on the inclined dam surface of the dam model. The sensor array includes two types of layout: horizontal layout along different water level lines and vertical layout along the dam axis. In order to reduce data discrepancy errors during the test and verify the validity of the data, two sensors are installed at each position for comparative measurement. The sensors are densely distributed in the area above the still water level to monitor the wave pressure changes above the still water surface.

[0028] A combination of conventional and miniature water pressure sensors is used. Conventional sensors (range -5~5kPa, frequency 50Hz, accuracy ±0.05%) are arranged horizontally along different design water levels on the dam face to obtain the distribution pattern of wave pressure along the dam axis. In areas with drastic changes in wave pressure gradient, such as the maximum impact zone, near the water surface line, and at points where the dam's geometry changes abruptly (such as slope break points), miniature sensors are densely deployed to capture the localized and refined pressure characteristics.

[0029] (2) Data synchronous acquisition: All sensors are connected to the computer control terminal through a dynamic signal acquisition instrument. The acquisition frequency is uniformly set to 50Hz, and the acquisition is triggered by the control platform at the moment the slider starts to start synchronously. The data is continuously recorded for 300s to ensure the synchronization and integrity of the data.

[0030] Based on a large amount of high-precision experimental data, this invention proposes an innovative theoretical calculation method:

[0031] (1) Key parameter identification: For the first time, we systematically identified the key parameters affecting the wave pressure on the inclined dam face. Six key parameters: sliding body entry velocity Initial water depth Volume of the sliding body Vs, maximum amplitude of the initial swell Maximum Climb on the Dam Wave incident angle ;

[0032] (2) Model establishment: Through dimensional analysis, the above parameters are combined into a highly general dimensionless mathematical model:

[0033]

[0034] (3) Coefficient Fitting and Formula Determination: Substituting the test data for all operating conditions into the above model, regression analysis was performed using the multivariate nonlinear least squares method. Finally, a set of optimal coefficients was obtained: a = 0.6185, b = 0.2880, c = 0.0217, d = 0.1467, e = 0.7613. The correlation coefficient R² of this fitting result is as high as 0.994, indicating that the formula has a very high interpretability of the experimental data and excellent prediction accuracy.

[0035] This invention obtains reliable surge pressure data by conducting prototype model tests that are closer to actual engineering conditions. Based on this, it constructs a surge pressure distribution model and calculation method for inclined dam faces applicable to surge effects on landslides, thereby accurately predicting the surge pressure on inclined dam faces. This data can be directly used to assess the surge resistance of existing dams and provide key technical parameters and theoretical support for the safety design and risk prevention of new dams.

[0036] To verify the superiority of this invention, the prediction results of the calculation formula of this invention were compared with the recommended method in the "Standard for Loads on Hydraulic Structures" (GB / T 51394-2020) and traditional methods such as Xiang Jin's formula. The results show that existing methods, due to their reliance on ideal assumptions or wind and wave conditions, suffer from systematic biases (either generally too high or too low) or large dispersion in their predicted values. The formula proposed in this invention exhibits a high degree of agreement with experimental data under different working conditions and demonstrates good stability, significantly improving the accuracy and reliability of wave pressure calculation for inclined dam surfaces under special loads such as landslide surges. This method can be directly used for safety assessment and risk control in the engineering design phase. Attached Figure Description

[0037] Figure 1 To consider large-scale landslide surge three-dimensional physical models for complex terrain;

[0038] Figure 2(a) and Figure 2(b) show the dynamic signal acquisition instrument and water pressure sensor of the wave pressure measurement equipment, respectively;

[0039] Figure 3 Schematic diagram of dam face slotting and wave pressure sensor installation;

[0040] Figure 4 This shows the vertical distribution of the maximum wave pressure along the dam axis.

[0041] Figure 5 Models for dam surface wave pressure distribution under non-overflow and overflow conditions;

[0042] Figure 6 Comparison of the experimental and predicted values ​​of the maximum wave pressure relative to the dam surface;

[0043] Figure 7This is to compare the experimental value of the maximum wave pressure relative to the dam surface with the empirically calculated value. Detailed Implementation

[0044] The invention will now be described in further detail with reference to the accompanying drawings.

[0045] Based on the Froude similarity criterion, this invention constructs a large-scale three-dimensional physical model of landslide surge waves at a scale of 1:150, using an actual landslide as a prototype. The model is characterized by its ability to accurately reflect the impact of complex terrain conditions on the experimental results. For example... Figure 1 As shown, the model includes a landslide test platform, a river channel model, a dam model, a hydraulic gate model, and a control platform.

[0046] The landslide test platform is equipped with a sliding box and a hydraulic control system to accurately simulate the landslide initiation and sliding process.

[0047] The river model is constructed primarily of cement, yellow sand, red bricks, and steel reinforcement, with the inner walls finished with white cement to ensure similarity in roughness. The terrain model employs a combination of panel cutting and contour line methods. The panel cutting is spaced 0.5m apart, while contour lines are denser in areas of dramatic terrain change, with a spacing of approximately 0.05m, to achieve precise simulation of complex terrain.

[0048] The dam model was constructed using concrete, aggregate, and water according to the actual engineering mix proportions to ensure that the dam surface roughness was consistent with the prototype. The left and right bank hydraulic gates were integrally formed with the dam body through positioning and casting, ensuring consistency between the model and the actual terrain.

[0049] The control platform is used to integrate and collect various types of test data.

[0050] The wave pressure testing system includes a computer control terminal, a dynamic signal acquisition instrument, and a water pressure sensor, as shown in Figure 2. The sensor comes in two types: conventional and miniature, with a measurement range of -5 kPa to 5 kPa, a sampling frequency of 50 Hz, and a resolution better than ±0.05%.

[0051] Figure 3 The diagram shows a dam face with slotted sensors installed. Conventional sensors are arranged in two ways: horizontally along different water levels, and vertically along the dam axis. Miniature sensors are densely distributed above the still water level to monitor wave pressure changes above the still water surface, ensuring measurement accuracy.

[0052] The specific experimental testing method of this invention is implemented according to the following steps:

[0053] (1) The sliding material that slid into the water in the previous test was retrieved and repositioned on the landslide test platform. The sliding box was placed horizontally and the gate was closed. The accumulation pattern of the sliding material was set according to the test conditions, and the sliding box was adjusted to the predetermined tilt angle by the hydraulic pump.

[0054] (2) Adjust the river water level to the specified depth for the test. After the water surface stabilizes, calibrate and zero all wave pressure sensors.

[0055] (3) Calibrate and start the high-speed camera system, and start synchronous recording after focusing is completed;

[0056] (4) Start the motor and open the sliding box stop door. The slide body begins to slide down, and the test is officially started.

[0057] (5) The data acquisition system will automatically stop recording after 300 seconds of continuous recording, and the camera equipment will be manually stopped after the test.

[0058] (6) Clean up the test site, prepare for the next set of tests, and process and analyze the collected data.

[0059] Experimental tests revealed that the overall wave pressure along the horizontal plane at different water levels was relatively small and the distribution was relatively uniform, without showing obvious regularity. Therefore, further detailed discussion is not required.

[0060] Conversely, the maximum wave pressure of the surge along the vertical direction of the dam axis differs significantly above and below the initial still water level. For example... Figure 4 As shown, above the water surface, wave pressure decreases rapidly with increasing height above the water surface, eventually reaching zero. Below the water surface, wave pressure does not decrease with water depth, but rather maintains a relatively stable amplitude.

[0061] Based on this phenomenon, assuming the dam surface is a smooth inclined plane and the dam body cross-section is a regular trapezoid, a simplified wave pressure distribution model is proposed: above the still water level, the wave pressure is distributed in a triangular pattern; below the still water level, it is considered to be uniformly distributed; the maximum wave pressure is located at the still water surface, such as... Figure 5 As shown in (a). To further study the overflow condition, an extended system was established. Figure 5 The model shown in (b)

[0062] It is worth noting that, Figure 4 A significant abrupt change in wave pressure occurred at position d0, which can be attributed to the platform region located precisely between the dam and the cofferdam. The presence of the platform disrupted the distribution of wave pressure, significantly altering its local characteristics. This abrupt change is a local effect of structural form on wave pressure and is unrelated to the conventional distribution pattern.

[0063] The key to the distribution model lies in accurately determining the magnitude of the maximum wave pressure. To quantitatively characterize the maximum wave pressure, a dimensionless wave pressure calculation formula is established by summarizing the results of various experimental conditions as follows:

[0064]

[0065] In the formula, This represents the maximum wave pressure on the dam surface. The density of the water body; It is the acceleration due to gravity; This is the initial water depth; The velocity of the sliding body upon entering the water; This represents the maximum amplitude of the initial swell. This represents the maximum elevation gain on the dam. For the wave incident angle, , , , , and These are coefficients to be determined.

[0066] Based on the operating condition data listed in Table 1, the coefficients obtained through multivariate nonlinear fitting are: a = 0.6185, b = 0.2880, c = 0.0217, d = 0.1467, e = 0.7613, f = 0.0076. The correlation coefficient of the fitting results is R0. 2 It is 0.994.

[0067]

[0068] Verification showed that the predicted values ​​of this formula matched the experimental values ​​well, such as... Figure 6 As shown, it can be used for reliable prediction of the wave pressure on the inclined dam face caused by landslide surges in practical engineering.

[0069] Finally, the calculated values ​​of this invention are compared with existing standard methods (including the recommended methods of GB / T 51394-2020, JTS145-2015, road regulation formulas, and Xiangjin formulas). Figure 7 The results show that the method provided by the present invention has higher accuracy and wider applicability, and is especially suitable for calculating the wave pressure on inclined dam surfaces under the action of large wave pressure and long-period surge waves.

Claims

1. A method for testing and calculating wave pressure on an inclined dam face under the action of landslide surge, characterized in that, Includes the following steps: (1) Based on the Froude similarity criterion, a large-scale three-dimensional physical model of landslide surge considering complex terrain is constructed according to the scale. The model includes a landslide test platform, a river channel model, a dam model, a hydraulic gate model and a control platform. The dam surface inclination angle and roughness of the dam model are simulated according to the actual engineering. (2) The test was carried out by simulating the landslide body entering the water under different working conditions through the hydraulic control system. The wave pressure time history data during the generation, propagation and impact of the dam surface were collected synchronously using a high-precision water pressure sensor array deployed on the inclined dam surface. (3) Process the test data, obtain the vertical distribution law of wave pressure along the dam axis, and analyze the characteristics of the wave pressure attenuating sharply above the water surface and the wave pressure distribution being relatively uniform below the water surface; (4) Define relative wave pressure as the dependent variable and Froude number of the sliding body entering the water, relative wave amplitude, relative run-up, and wave incident angle as independent variables to establish a dimensionless mathematical model; (5) Substitute the test data of each working condition into the mathematical model to perform multivariate nonlinear regression analysis, fit the calculated coefficients, and finally establish the explicit calculation formula for calculating the maximum wave pressure on the inclined dam surface.

2. The method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges as described in claim 1, characterized in that, The river model is mainly constructed of cement, yellow sand, red bricks and steel bars. The inner wall is treated with white cement plaster to ensure roughness similarity. The terrain construction adopts a combination of the panel method and the contour line method. The panel spacing is 0.5 m, and the contour lines are denser in areas with drastic terrain changes, with a spacing of about 0.05 m, in order to achieve a detailed simulation of complex terrain.

3. The method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges as described in claim 1, characterized in that, The dam model and hydraulic gate model are made of concrete, aggregate and water according to the actual engineering mix ratio to ensure that the surface roughness of the dam is consistent with the prototype; the hydraulic gates on the left and right banks are formed as a whole with the dam body through positioning and casting to ensure the consistency between the model and the actual terrain.

4. The method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges as described in claim 1, characterized in that, A water pressure sensor array is installed in a slot on the inclined dam surface of the dam model. The sensor array includes two types of arrangements: horizontal arrangement along different water level lines and vertical arrangement along the dam axis. In order to reduce data discrepancy errors during the test and to verify the validity of the data, two sensors are installed at each location for comparative measurement. The sensors are densely distributed in the area above the still water level to monitor the wave pressure changes above the still water surface.

5. The method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges as described in claim 1, characterized in that, The experiment includes the following steps: (1) The sliding material that slid into the water in the previous test was retrieved and repositioned on the landslide test platform. The sliding box was placed horizontally and the gate was closed. The accumulation pattern of the sliding material was set according to the test conditions, and the sliding box was adjusted to the predetermined tilt angle by the hydraulic oil pump. (2) Adjust the river water level to the specified depth for the test. After the water surface stabilizes, calibrate and zero all wave pressure sensors. (3) Calibrate and start the high-speed camera system, and start synchronous recording after focusing is completed; (4) Start the motor and open the sliding box stop door. The slide body begins to slide down, and the test is officially started. (5) The data acquisition system will automatically stop recording for one period of time, and the camera equipment will be manually stopped after the test. (6) Clean up the test site, prepare for the next set of tests, and process and analyze the collected data.

6. The method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges as described in claim 1, characterized in that, The dimensionless mathematical model and calculation formula are as follows: In the formula, This represents the maximum wave pressure on the dam surface. The density of the water body; It is the acceleration due to gravity; This is the initial water depth; The velocity of the sliding body upon entering the water; This represents the maximum amplitude of the initial swell. This represents the maximum elevation gain on the dam. The angle of incidence of the wave. , , , , and These are coefficients to be determined.

7. The method for testing and calculating wave pressure on an inclined dam surface under the action of landslide surges as described in claim 1, characterized in that, The sensors are available in two types: conventional and miniature. Their measurement range is -5 kPa to 5 kPa, the acquisition frequency is 50 Hz, and the resolution is better than ±0.05%.

8. The method for testing and calculating the wave pressure on an inclined dam surface under the action of landslide surges as described in claim 6, characterized in that, The coefficients to be determined were determined by fitting experimental data and their values ​​are: a = 0.6185, b = 0.2880, c = 0.0217, d = 0.1467, e = 0.7613, f = 0.0076.

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