A method for calculating the risk of landslide surge and dam-break flood in earth-rockfill dam reservoir area

Abstract

The present invention discloses a method for calculating the risk of landslide surge dam-break floods in earth-rock dam reservoir areas, including: calculating the peak flow and peak duration of a conventional overtopping dam-break flood in an earth-rock dam; collecting information on landslide bodies in the earth-rock dam reservoir area, including but not limited to the volume, height, and location of the landslide bodies; calculating a peak flow amplification factor and a peak duration amplification factor; multiplying the peak flow amplification factor by the conventional overtopping dam-break flood peak flow of an earth-rock dam to obtain the peak flow of an earth-rock dam break flood under the action of landslide surge; and multiplying the peak duration amplification factor by the conventional overtopping dam-break flood peak duration of an earth-rock dam to obtain the peak duration of an earth-rock dam break flood under the action of landslide surge. The present invention establishes a disaster amplification effect evaluation model with multi-factor correlation, which can avoid repetitive conventional physical model experiments and adapt to the disaster prediction needs of reservoirs of different sizes.

Description

Technical Field

[0001] The present invention belongs to the technical field of flood risk assessment, and in particular relates to a method for calculating landslide surge and dam-break flood risks in earth-rock dam reservoir areas. Background Art

[0002] Periodic fluctuations in reservoir water levels increase the risk of instability in the rock and soil near the dam bank. The surge waves generated by the high-speed entry of landslides into the water have a significant disaster-amplifying effect. When faced with multiple surge waves, the erosion rate of earth-rock dams, which are relatively weak in disaster resistance, increases nonlinearly. After repeated surge erosion, overtopping and failure may occur. Compared to conventional flood overtopping, surge waves can exacerbate the erosion process, accelerate the arrival of peak flows, and further amplify the disaster. Therefore, uncovering the evolution of earth-rock dam failure floods under surge impacts and the hazard amplification mechanisms has become a key topic in the field of disaster prevention and mitigation.

[0003] There are many methods to study the movement process of landslide surge in reservoir areas, including physical model tests and numerical simulations. Numerical simulation technology can better simulate the physical movement process of fluid under fluid-solid coupling, has strong repeatability, and can be used as an important tool to supplement field investigation and experimental data. Many scholars have carried out a large number of numerical simulation studies on the landslide disaster chain process in reservoir areas, such as Huang Jinlin et al. Study on the impact of reservoir bank landslide surge on dam body [D]. Tianjin University, 2012, which studied the process of surge generation caused by high-speed landslide sliding into water, and Li Yuqian et al. Study on the influence of landslide surge pressure distribution in front of dam on the damage of earthquake-damaged arch dam [J]. Journal of Hydraulic Engineering, 2024, 55(02): 214-225, which analyzed the distribution law of surge height in front of dam and the influence of different surge pressure distribution in front of dam on the damage of earthquake-damaged arch dam.

[0004] Currently, there is a lack of research in the existing technology on the erosion and destruction process of earth-rock dams caused by landslide surges. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for calculating the risk of dam-break flood caused by landslide surge in the reservoir area of ​​an earth-rock dam, to study the erosion and destruction process of earth-rock dams caused by landslide surge, and to quickly and quantitatively calculate the risk of dam-break flood caused by landslide surge.

[0006] The technical solution adopted in the present invention is:

[0007] A method for calculating the risk of landslide surge and dam-break flood in an earth-rock dam reservoir area comprises the following steps:

[0008] Step 1: Calculate the peak flow and peak duration of a conventional overtopping dam failure of an earth-rockfill dam;

[0009] Step 2: Collect landslide information in the earth-rock dam reservoir area, including but not limited to landslide volume, height, and location information; calculate the peak flow amplification factor using the following formula: K Q :

[0010]

[0011] Step 3: Calculate the flood peak duration amplification factor using the following formula: K T :

[0012]

[0013] Where β is the slope angle in front of the dam, V w The reservoir capacity above the breach bottom at the time of dam failure; V s is the volume of the landslide, H s is the height of the landslide, W d is the dam crest width, D s is the distance between the landslide body and the dam site, H d is the reservoir water level.

[0014] Step 4: multiplying the peak flow amplification factor in step 2 by the conventional overtopping and dam-break peak flow of the earth-rock dam in step 1 to obtain the peak flow of the earth-rock dam break under the action of landslide surge;

[0015] Step 5: multiply the flood peak duration amplification coefficient in step 3 by the conventional overtopping and dam-break flood peak duration in step 1 to obtain the flood peak duration of the earth-rock dam break under the action of landslide surge.

[0016] The method for calculating the conventional overtopping and dam-break flow process of earth-rock dams in step 1 belongs to the existing technology. Please refer to the literature: Qiming Zhong et al. New Empirical Model for Breaching of Earth-Rock Dams.

[0017] Furthermore, the formula for calculating the peak flow in step 1 is:

[0018]

[0019] Where: Q P is the peak flow; V w The reservoir capacity above the breach bottom at the time of dam failure; g is the acceleration due to gravity, take 9.8m / s 2 ;h w The water depth above the bottom of the breach when the dam breaks; h d The height of the earth-rock dam; h b The depth of the breach.

[0020] Furthermore, the calculation formula for the flood peak duration in step 1 is:

[0021]

[0022] Where: T f It is the duration of the flood peak caused by earth-rock dam burst.

[0023] Furthermore, the collection of landslide information in the earth-rock dam reservoir area in step 2 includes: combining three-dimensional laser scanning and drone oblique photography technology to obtain the spatial coordinates and volume parameters of the landslide body, and then obtaining physical and mechanical parameters such as the landslide body density and internal friction angle through drilling sampling and other methods; the obtained heterogeneous data are standardized to mainly extract the volume, height and location information of the landslide body.

[0024] Physical and mechanical parameters such as landslide density and internal friction angle can be used to calculate peak flow using other methods.

[0025] Furthermore, the calculation formulas for the flood peak flow amplification factor in step 2 and the flood peak duration amplification factor in step 3 are obtained by the following method:

[0026] Conduct integrated physical model tests of small-scale earth-rock dam landslide surge dam failures and record image, water level, and wave height data;

[0027] The numerical model was set up using the same parameters as the physical model test, including the geometric parameters and boundary conditions of the landslide model, earth-rock dam model, and reservoir model. The landslide material and dam material properties in the numerical model were the same as those in the physical model test. The water level, wave height, and flow rate collection points in the numerical simulation were the same as those in the physical model test.

[0028] Taking landslide volume, landslide height, dam crest width, dam front slope angle, and landslide distance as influencing factors, multiple sets of numerical simulation tests were carried out. The reservoir water level was set at the overtopping level. Numerical simulations were conducted on two types of tests: landslide surge-induced dam failure and conventional overtopping dam failure. The landslide surge dam failure and conventional overtopping dam failure processes were calculated under various working conditions.

[0029] Based on the numerical simulation results, the dam-break flood process is extracted, including the peak flow and duration of the earth-rock dam break under the action of landslide surge and natural overtopping. Based on the extracted flow characteristics, the peak flow amplification factor and the peak duration amplification factor are calculated.

[0030] Using multiple dimensionless parameters including but not limited to relative landslide volume, relative landslide height, relative dam crest width, dam front slope angle and relative landslide distance, under different flow conditions, the power function form is used to fit the dam break peak flow, peak duration, peak flow amplification coefficient and peak duration amplification coefficient respectively. By calculating the determination coefficient and correlation coefficient, the calculation expressions of the peak duration amplification coefficient and the peak flow amplification coefficient are finally determined.

[0031] The beneficial effects of the present invention are:

[0032] The present invention proposes a dual-parameter disaster amplification coefficient based on flood peak flow and flood peak duration, and establishes a disaster amplification effect calculation model with multi-factor correlation, which can avoid repetitive conventional physical model experiments. The proposed dimensionless parameter correlation model takes into account both theoretical rigor and engineering practicality, can adapt to the disaster prediction needs of reservoirs of different sizes, and provide reliable technical support for the formulation of emergency plans. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flow chart of Example 1;

[0034] Figure 2 is a schematic diagram of the numerical model boundary;

[0035] Figure 3 It is a schematic diagram of the distribution of water level and flow collection points in numerical simulation and physical model test;

[0036] Figure 4 This is a schematic diagram of the outburst flow process of an earth-rock dam under the action of landslide surge, obtained through numerical simulation and physical model tests;

[0037] Figure 5 is a parameter ( V w ) 1 / 3 / D s Peak flow amplification factor K Q and the fitting effect of peak discharge;

[0038] Figure 6 is the peak flow amplification factor of each flood in Example 1 K Q comparison. DETAILED DESCRIPTION

[0039] The method of the present invention is described below with reference to the accompanying drawings and specific embodiments:

[0040] Example 1: This example takes a landslide in a mountainous area of ​​an earth-rock dam reservoir as an example to evaluate the dam-break flow process after the landslide. The specific steps are as follows: Figure 1 As shown, including:

[0041] Step 1: Conduct a small-scale integrated physical model test of landslide surge dam failure in the earth-rock dam reservoir area, and record data such as images, water levels, and wave heights in detail.

[0042] The specific method of conducting the integrated physical model test of small-scale earth-rock dam landslide surge dam breach in step 1 belongs to the existing technology. Please refer to the method disclosed in the literature: Experimental analysis on breaching mechanism of earth-rockdam induced by landslide generated waves.

[0043] like Figure 2 As shown, the length of the tank L 2 is 5m wide W 0.4m high H 2 is 0.6m; the slope of the chute is the same as the slope of the water trough, α 45°; the projection length of the chute in the horizontal direction L 1 is 2m, high H 1 is 2m. After being completely air-dried and dried, the dam material is divided into 6 particle size groups, namely <0.5 mm, 0.5-1 mm, 1-2 mm, 2-4 mm, 4-6 mm and 6-10 mm. In order to achieve better test results, the landslide body is generally generalized into a rigid rectangular block in this test. The landslide body is made of concrete with a dry density of 2200kg / m 3 .

[0044] A preset earth-rock dam model is placed in a water tank, and the landslide body slides freely along the chute under the action of its own weight. The test is considered to be over when the dam body is destabilized by the landslide surge and the upstream water level no longer changes. Characteristic data such as image video, wave height, and flow are recorded and extracted.

[0045] Step 2: Use the same parameters as the physical model test in step 1 to set up the numerical model. The numerical model setting includes setting the geometric parameters of the landslide model, earth-rock dam model, and reservoir model, as well as the boundary conditions such as Figure 2 As shown, boundary A is a free boundary for inflow and free sliding of the landslide body, boundaries B and C are solid constraint boundaries, and boundary D is a free boundary for outflow. The volume of the landslide body is set to 0.008 (0.4×0.2×0.1) m 3The height of the landslide body is set to be in the chute 1.4m above the ground; the water level of the reservoir is set to 0.38m; the height of the dam model is set to 0.4m, the width is 0.4m, and the slope ratio before and after the dam is set to 1:1.5, that is, the length before and after the dam is 0.6m, the top surface width is set to 0.04m, and the cross-section is in the shape of a regular trapezoid.

[0046] In both the physical model test and the numerical model simulation, the landslide body is made of concrete with a dry density of 2200 kg / m 3 The dam material properties of the numerical model are set to be the same as those of the physical model test, including gradation composition, density and angle of repose, as shown in Table 1.

[0047] Table 1. Material properties in physical model tests and numerical models

[0048]

[0049] Figure 3 The distribution of water level, wave height and flow collection points in numerical simulation and physical model test is shown. Three wave height recording points are set at 0.1m where the landslide enters the water, 0.7m in the middle of the reservoir area and 1.5m in front of the dam, namely Figure 3 Points a, b, and c.

[0050] Based on the aforementioned numerical model, the present invention performs numerical simulation in the CFD software Flow3D (Flow Science, 2023) based on the finite volume method. The aforementioned geometric structure parameters and material characteristic parameters are input into the software, the boundary conditions and time step are set, and the calculation program is iterated; the time, flow field information of each grid, water depth of each recording point and flow process data are output, and the calculation results are compared with the image, wave height and water level data actually measured by the physical model test in step 1, so as to verify the accuracy of the established numerical model erosion process.

[0051] By calculating the water level, Figure 4 A comparison was made between the breach flow processes of the physical model test and the numerical simulation calculations. The results showed that the peak flow differed by only 4%. Therefore, the water level data, breach flow, development process and other characteristics of the numerical simulation were in good agreement with the results of the physical model test, indicating that the numerical model established by the present invention has a good simulation effect.

[0052] Compared with conventional (natural) overtopping dam failure, landslide surge dam failure has a certain amplification effect on the consequences of disasters. This amplification is mainly reflected in the increase of dam failure peak flow and the shortening of the peak flow arrival time. Based on the numerical simulation results, the dam failure flood process is extracted, including the peak flow and arrival time of earth-rock dam failure under the action of landslide surge and conventional overtopping, and the start time of violent earth-rock dam failure under the action of landslide surge and conventional overtopping; based on the extracted flow characteristic results, the disaster amplification coefficient is calculated, including the peak flow amplification coefficient K Q and flood peak duration amplification factor K T , which can be expressed as:

[0053]

[0054] in, Q ps Refers to the peak flow of earth-rock dam burst caused by landslide surge. Q pi Refers to the peak flow of earth-rock dam burst under natural overtopping. T ps Refers to the arrival time of the flood peak flow of the earth-rock dam under the action of landslide surge. T pi Refers to the arrival time of the peak flow of earth-rock dam break under natural overtopping; T bs Refers to the time when the earth-rock dam begins to break violently due to the action of landslide surge. T bi Refers to the time when the earth-rock dam begins to collapse violently due to natural overtopping.

[0055] According to the numerical simulation calculation results of this embodiment, the peak flow rate under the action of landslide surge and the peak flow rate under the action of conventional (natural) overtopping, as well as the peak duration under the action of landslide surge and the peak duration under the action of conventional overtopping are fitted into curves. It is found that the relationship between them basically conforms to the simplest linear correlation, where K Q =1.228, coefficient of determination R 2 is 0.804; K T =0.738, coefficient of determination R 2 It is 0.81.

[0056] Step 3: To further analyze the influencing factors and severity of landslide surge dam failure, 31 numerical simulation tests were conducted, focusing primarily on five factors: landslide volume, landslide height, dam crest width, dam front slope angle, and landslide distance, as shown in Table 2. These simulations included two types of dam failure: one driven by landslide surge and the other by conventional overtopping. Under identical dam conditions and initial water levels, one simulation involved a natural overtopping-driven dam failure and the other involved a landslide surge-driven overtopping-driven dam failure. Conditions marked with an asterisk (*) represent benchmark tests; Group 0 represents the laboratory validation conditions.

[0057] Table 2 Experimental conditions during numerical simulation

[0058]

[0059] The reservoir water level was set at the overtopping level, and numerical simulations were carried out using two types of tests: dam failure caused by landslide surge and dam failure caused by conventional overtopping. The landslide surge dam failure and conventional overtopping dam failure processes were calculated under various working conditions, and the dam failure flow processes of the earth-rock dams under various working condition groups were compared, as well as the dam failure flow processes of the earth-rock dams under different incoming flows.

[0060] Further exploration of the influence of different parameters to quantify the disaster amplification factor, multiple dimensionless parameters were selected for quantitative analysis, including but not limited to relative landslide volume ( V s / V w ), relative landslide height ( H s / H w ), relative dam crest width ( W d / H d ), dam front slope angle (tan β ) and relative landslide distance (( V w ) 1 / 3 / D s ), these parameters affect the landslide surge dam break disaster chain process.

[0061] The degree of disaster amplification varies under different variables. Table 3 records the multi-factor amplification coefficients obtained from 31 sets of numerical simulation experiments.

[0062] Table 3 Main dimensionless parameters of landslide surge dam-break flood process

[0063]

[0064] The dam-break peak flow is the most critical parameter to characterize the severity of earth-rock dam failure disasters, which is mainly affected by factors such as the width of the dam longitudinal axis, the reservoir capacity and the incoming flow process. The dam-break peak flow of earth-rock dams is better fitted with a multi-parameter power function. In this invention, the power function is used to fit the dam-break peak flow under different incoming flows, and the power function is used to fit the influence of different factors on the dam-break peak flow and the amplification coefficient. K Q degree of impact.

[0065] The results show that the parameters have an impact on the peak flow Q The fitting effect is generally good, and the determination coefficient is higher than 0.75, and generally above 0.9. K Q ,parameter( V w ) 1 / 3 / D s The fitting effect is not good, such as Figure 5 As shown in the figure, the location of the landslide has no significant amplification effect on the surge dam failure. However, the landslide surge in the reservoir area is characterized by short duration, strong excitation, and high frequency. The influence of the distance from the landslide to the dam site is more on the temporal variation, and has little effect on the amplification of the peak flow.

[0066] To obtain the peak flow amplification factor K Q Function expression, using multivariate analysis to study the effect of various factors on K Q The degree of influence of the multivariate nonlinear formula can be expressed as:

[0067]

[0068] in, y is the dependent variable, which is characterized by the peak flow amplification factor in the present invention; x i Represents different dimensionless parameters.

[0069] The number of independent variables in regression analysis significantly affects the results. In order to further simplify the formula, we further calculated y and x i Pearson correlation coefficient between ρ and Spearman correlation coefficient p , as shown in Table 4 below:

[0070] Table 4 Correlation coefficients between disaster amplification factors and various parameters

[0071]

[0072] According to the results of correlation coefficient calculation, if the correlation coefficient is less than 0.2, it is considered that the two are not correlated. Therefore, considering the correlation coefficient and goodness of fit, the peak flow amplification factor K Q The parameters such as relative landslide volume, relative landslide height, dam front slope angle and relative dam crest width are used to express it as follows:

[0073]

[0074] Figure 6 The K calculated by the above fitting formula Q value, K obtained by fitting the above simulation calculation results Q =1.228 and compared with the simulation values ​​in Table 3. The results show that compared with simple linear regression, multi-parameter nonlinear regression has a better fitting effect and is dimensionless. If it is difficult to obtain various parameters in a short time during the project, the most basic linear formula can still be used to estimate the severity of the disaster.

[0075] The arrival time of a flood peak is both a primary driver of the physical process in earth-rock dam failures and a key constraint on emergency management. It is primarily related to the incoming flood process and the earth-rock dam's ability to withstand the impact of the water flow. A power function was used to fit the influence of different factors on the time of the flood peak and the amplification coefficient. The results showed that the fitting effect of dam crest width was poor, with a coefficient of determination of only 0.09. The results in Table 3 also show that there is no significant correlation between dam crest width and flood peak time. The influence of dam crest width is more inclined to the possibility of earth-rock dam failure. However, the premise of this study is that the dam has already failed, so the disaster amplification effect on flood peak duration is not obvious.

[0076] Flood peak duration amplification factor K T The relative landslide volume, relative landslide height, dam front slope angle and relative landslide distance are expressed as:

[0077]

[0078] Step 4: The normal water storage level of the earth-rock dam project is 1492.53 m, the design flood level is 1494.57 m, the verification flood level is 1496.43 m, and the total storage capacity is 6.779 million m 3 , flood control reservoir capacity 2.1993 million m 3 The maximum dam height is 41 m. The following formula is used to calculate the peak discharge of the conventional overtopping dam break of this earth-rock dam:

[0079]

[0080] Where: Q P is the peak flow, m 3 / s;V w The reservoir capacity above the breach bottom at the time of dam failure; g is the acceleration due to gravity, take 9.8 m / s 2 ; h w The water depth above the bottom of the breach when the dam breaks, which is 41m; h d The height of the earth-rock dam; h b is the breach depth, which is 32.2m. The calculated peak flow rate after the earth-rock dam is conventionally overtopping and breaching is 4381.56 m 3 / s.

[0081] The calculation formula for flood peak duration is:

[0082]

[0083] Where: T f Characterizes the duration of the flood peak after the earth-rock dam burst, h; the flood peak duration after the earth-rock dam overtopping and burst calculated in this embodiment is 0.47h.

[0084] Step 5: The landslide volume in the reservoir area of ​​the earth-rock dam is about 3 million m 3 The center of the landslide is 30m high and 0.5km away from the dam site. The flood peak flow amplification coefficient can be obtained by calculating the disaster amplification formula in step 3. K Q The flood peak duration amplification factor is 1.27. K T Combined with the conventional overtopping dam burst peak flow and peak duration obtained in step 4, the peak flow of the earth-rock dam burst under the action of landslide surge is 6167.25 m 3 / s (i.e. 1.27×4856.1 m 3 / s), and the peak duration was 0.26h (i.e. 0.55×0.47h).

[0085] Example 2

[0086] The numerical model described in Example 1 is a scaled three-dimensional refined integrated numerical model of landslide surge and dam failure established based on the physical model in step 1. The numerical model includes three modules: a hydrodynamic model, a landslide movement model, and a dam material erosion model, which are:

[0087] Hydrodynamic model: RANS equations are used to simulate the motion of three-dimensional incompressible fluids, while the ratio of fluid volume to unit volume is introduced. V F To describe the free flow interface between fluid and dam material, its continuity equation and momentum equation can be expressed as:

[0088]

[0089] Where: ρ w is the density of water; t For time; u , v , w They are x , y , z Flow velocity in direction; A x , A y , A z They are x , y , z The proportion of flow area in the direction; u i for i Flow velocity vector under the coordinate axis; P is pressure; g i for i Mass acceleration in the direction; f i for i Viscous acceleration in the direction.

[0090] Landslide motion model: The landslide entering water process is a complex fluid-solid coupling problem. Source terms are added to the continuity equation and VOF transport equation to explain the influence of the moving object on the fluid displacement. For incompressible fluid, it can be expressed as:

[0091]

[0092] Where: It is the divergence term of the product of velocity u and flow area fraction A, indicating that the area fraction A changes with the flow velocity u in space, representing the convective transport term; S m is the source term of the physical quantity of the fluid; ρ is the density, which represents the mass density of the phase under consideration; compared with the continuity equation in the stationary obstacle problem, Can be considered as an additional source term, representing the volume fraction V F The local rate of change over time.

[0093] When using the control volume method, the The source term exists only in the grid cells around the boundary of the moving object and can be expressed as:

[0094]

[0095] Where: V c Refers to the grid cell volume; S o 、 u o , n are the surface area, velocity, and unit normal vector of the moving object in the grid cell respectively.

[0096] Sediment erosion model:

[0097] During the collapse of an earth-rock dam, the earth and rock materials move with the flow. Earth and rock materials in the flow can be divided into bedload and suspended load, which can be converted into each other under different hydrodynamic conditions. Their movement can be mainly divided into sediment settling, sediment entrainment, and bedload transport. The law of conservation of dam material mass can be expressed as:

[0098]

[0099] Where: z is the bottom elevation; Φ is the maximum accumulation fraction; q bx and q by They are x , y Directional single-width volume bedload transport rate; D is the weighted average of the sedimentation rates of particles of different sizes, E It is the weighted average of the upward entrainment velocities of particles of different sizes.

[0100] During entrainment, the rate of transfer of soil and rock from bedload to suspended load can be determined by the following formula:

[0101]

[0102] Where: α is the entrainment coefficient of different dam materials; n s is the normal vector of the breach bed; is the dimensionless particle size parameter; θ is the dimensionless Shields number; θ cr To correct the critical Shields number; ρ s is the density of dam material; g is the acceleration due to gravity; d 50 is the median particle size of dam material.

[0103] In sedimentation, the settling rate of suspended matter can be expressed as the product of the effective settling rate and the suspended matter concentration:

[0104]

[0105] Where: v f is the kinematic viscosity of the fluid; c is the suspended matter concentration of different particle sizes.

[0106] The bed load erosion rate can be expressed as:

[0107]

[0108] Where: K is the bed load coefficient; d is the particle size of the dam material.

[0109] This embodiment constructs an integrated numerical simulation framework for the entire process of landslide movement, surge propagation, and dam breach, breaking through the limitations of traditional single disaster simulation. It fully reproduces the nonlinear transmission of surge impact loads, the multi-frequency superposition characteristics, and the spatiotemporal evolution of breach development, providing a high-precision simulation tool for the mechanism analysis of chain disasters.

Claims

1. A method for calculating the risk of landslide surge and dam-break flood in earth-rock dam reservoir area, characterized by: include: Step 1: Calculate the peak flow and peak duration of a conventional overtopping dam failure of an earth-rockfill dam; The formula for calculating peak flow is: ； Where: Q P is the peak flow; g is the acceleration due to gravity, take 9.8 m / s 2 ; h w The depth of water above the bottom of the breach when the dam breaks; h d The height of the earth-rock dam; h b is the depth of the breach; The calculation formula for flood peak duration is: ； Where: T f is the flood peak duration of earth-rock dam failure; Step 2: Collect landslide information in the earth-rock dam reservoir area, including but not limited to landslide volume, height, and location information; calculate the peak flow amplification factor using the following formula: K Q : ； Step 3: Calculate the flood peak duration amplification factor using the following formula: K T : ； Where β is the slope angle in front of the dam, V w The reservoir capacity above the breach bottom at the time of dam failure; V s is the volume of the landslide, H s is the height of the landslide, W d is the dam crest width, D s is the distance between the landslide body and the dam site, H d is the reservoir water level; Step 4: multiplying the peak flow amplification factor in step 2 by the conventional overtopping dam-break peak flow of the earth-rock dam in step 1 to obtain the peak flow of the earth-rock dam-break under the action of landslide surge; Step 5: multiply the flood peak duration amplification factor in step 3 by the conventional overtopping and dam-break flood peak duration of the earth-rock dam in step 1 to obtain the flood peak duration of the earth-rock dam break under the action of landslide surge.

2. The method for calculating the risk of landslide surge and dam-break flood in earth-rockfill dam reservoir area according to claim 1 is characterized in that: The calculation formulas for the flood peak flow amplification factor in step 2 and the flood peak duration amplification factor in step 3 are obtained by the following method: Conduct integrated physical model tests of small-scale earth-rock dam landslide surge dam failures and record image, water level, and wave height data; The numerical model was set up using the same parameters as the physical model test, including the geometric parameters and boundary conditions of the landslide model, earth-rock dam model, and reservoir model. The landslide material and dam material properties in the numerical model were the same as those in the physical model test. The water level, wave height, and flow rate collection points in the numerical simulation were the same as those in the physical model test. Taking landslide volume, landslide height, dam crest width, dam front slope angle, and landslide distance as influencing factors, multiple sets of numerical simulation tests were carried out. The reservoir water level was set at the overtopping level. Numerical simulations were conducted on two types of tests: landslide surge-induced dam failure and conventional overtopping dam failure. The landslide surge dam failure and conventional overtopping dam failure processes were calculated under various working conditions. Based on the numerical simulation results, the dam-break flood process is extracted, including the peak flow and duration of the earth-rock dam break under the action of landslide surge and natural overtopping. Based on the extracted flow characteristics, the peak flow amplification factor and the peak duration amplification factor are calculated. Using multiple dimensionless parameters including but not limited to relative landslide volume, relative landslide height, relative dam crest width, dam front slope angle and relative landslide distance, under different flow conditions, the power function form is used to fit the dam break peak flow, peak duration, peak flow amplification coefficient and peak duration amplification coefficient respectively. By calculating the determination coefficient and correlation coefficient, the calculation expressions of the peak duration amplification coefficient and the peak flow amplification coefficient are finally determined.

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