Prediction method and prediction model for geometrical morphology of blocking river and forming dam by debris flow

Abstract

The invention relates to the technical field of disaster prevention and reduction engineering, in particular to a method and a model for predicting the geometrical morphology of river blocking and dam forming by debris flow. According to the prediction method, original data are collected according to the debris flow property, the main river hydrodynamic condition, the boundary resistance, the main river morphology and the debris flow gully morphology, the debris flow weir dam accumulation height, the debris flow weir dam accumulation length and the debris flow weir dam volume are predicted, and the prediction precision is high.

Description

Technical Field

[0001] The present invention relates to the technical field of disaster prevention and reduction engineering, and in particular to a prediction method and a prediction model for the geometric form of a debris flow blocking a river and forming a dam. Background Art

[0002] Debris flow is a special fluid between Newtonian fluid and non-Newtonian fluid. It has the characteristics of suddenness, high energy and high destructive power, high solid matter and block content, making it a very dangerous natural disaster, seriously threatening the safety of life and property of local people. When a large amount of debris flow flows into the main river, it will also block the main river and form a barrier lake of a certain size, which will cause flooding disasters in the barrier lake reservoir area and downstream disasters of the barrier dam burst flood, further amplifying the losses of debris flow disasters.

[0003] At present, some studies have summarized and published some empirical formulas for predicting the possibility of river blockage after debris flow breaks out; some studies, such as the Chinese invention patent with patent publication number CN116401746A, disclose a method for predicting the geometric parameters of a dam, obtain physical parameters and topographic parameters to establish a calculation model of the dam formation process, and analyze the influence of landslide volume, sliding surface inclination, natural repose angle of landslide body and landslide body velocity on the geometric parameters of the dam through data simulation to obtain a fitting formula. However, this type of prior art does not take into account the influence of the main river flow on the movement of the debris flow after the debris flow enters the main river, which leads to a decrease in the accuracy of the prediction of the geometric parameters of the dam. Summary of the invention

[0004] In view of the deficiency that the accuracy of the prediction of the geometric form of existing landslide dams needs to be improved, the present invention provides a prediction method and prediction model for the geometric form of debris flow blocking a river and forming a dam, which considers the effects of debris flow properties, main river hydrodynamic conditions, and boundary resistance on the movement and accumulation process of debris flow, and derives the dam height, dam length, and dam volume of the debris flow landslide dam based on the theorem of conservation of momentum, predicts the geometric form of debris flow blocking a river and forms a dam, and improves the prediction accuracy.

[0005] The present invention provides a method for predicting the geometrical morphology of debris flow blocking a river and forming a dam. Original data are collected based on the properties of the debris flow, the hydrodynamic conditions of the main river, the boundary resistance, the main river morphology, and the debris flow ditch morphology to predict the accumulation height, accumulation length, and volume of the debris flow dam.

[0006] Furthermore, in order to better implement the present invention, when predicting the accumulation height of the debris flow dam, the maximum accumulation height of the dam top is first calculated, and then the maximum accumulation height of the dam top is calculated according to the river blocking determination coefficient. C rThe numerical value of is used to judge whether there is a high-rise phenomenon after the debris flow reaches the other side, and the minimum accumulation height of the dam top is calculated to predict the accumulation height of the debris flow dam.

[0007] Furthermore, in order to better implement the present invention, the river blocking determination coefficient C r The calculation is based on the flow rate of the debris flow, the flow rate of the main river, the flow velocity of the debris flow, the flow velocity of the main river, the total amount of material flushed out by a debris flow, the specific gravity of the debris flow, the water depth of the main river, the width of the main river channel, the width of the debris flow ditch, the yield stress of the debris flow, the roughness of the main riverbed, the debris flow ditch outlet, and the angle of the main river channel.

[0008] Furthermore, in order to better realize the present invention, the minimum accumulation height of the dam top and the maximum accumulation height of the dam top are calculated based on the debris flow discharge distance, the siltation slope of the accumulation body surface, the longitudinal slope of the main river channel along the direction of debris flow movement, and the width of the main river channel.

[0009] Furthermore, the minimum accumulation height at the dam top and the maximum accumulation height at the dam top are calculated based on the debris flow discharge distance, the siltation slope on the surface of the accumulation body, the longitudinal slope of the main river channel along the direction of debris flow movement, and the width of the main river channel.

[0010] The present invention also provides a prediction model for the geometrical form of debris flow blocking a river and forming a dam, including a debris flow dam accumulation height calculation unit, a debris flow dam accumulation length calculation unit and a debris flow dam volume calculation unit; Based on the original data collected from the properties of debris flow, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow ditch morphology as input, the debris flow dam accumulation height is predicted by the debris flow dam accumulation height calculation unit, the debris flow dam accumulation length is predicted by the debris flow dam accumulation length calculation unit, and the debris flow dam volume is predicted by the debris flow dam volume calculation unit.

[0011] The beneficial effects of the present invention are as follows.

[0012] (1) The present invention provides a method for predicting the geometric shape of debris flow blocking a river and forming a dam. The method takes into account the effects of debris flow properties, main river hydrodynamic conditions, and boundary resistance on the movement and accumulation process of debris flow, thereby improving the prediction accuracy and making the calculation results more reliable.

[0013] (2) The present invention provides a method for predicting the geometric shape of debris flow dams. Based on the law of conservation of momentum, the height, length and volume of debris flow dams are deduced. This method is simpler and faster than the calculation process of physical model experiments and numerical simulation methods.

[0014] (3) The present invention provides a method for predicting the geometric shape of debris flow dams. The predicted parameters involve key parameters of the geometric shape of debris flow dams, including the height, total length, upstream dam length, downstream dam length and volume of the debris flow dam, which provides important basic data for the risk assessment of debris flow dams.

[0015] (4) The geometric shape prediction model of debris flow blocking a river and forming a dam provided by the present invention has the advantages of strong theoretical basis, clear calculation process and fast solution speed.

[0016] (5) The present invention provides a method and model for predicting the geometric shape of debris flow blocking a river and forming a dam, which is mainly used for predicting the river blocking and forming a dam before a debris flow disaster occurs, and is an important part of risk assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a plan view of the debris flow dam in Example 2.

[0018] Figure 2 for Figure 1 Longitudinal section of the TT surface of the medium debris flow dam.

[0019] Figure 3 for Figure 1 Longitudinal section of the MM surface of the medium debris flow dam.

[0020] In the figure: 1. Debris flow ditch; 2. Debris flow dam; 3. Main river channel; 4. Debris flow. DETAILED DESCRIPTION

[0021] The above contents of the present invention are further described in detail below in conjunction with the specific implementation methods of the embodiments. However, this should not be understood as the scope of the above subject matter of the present invention being limited to the following examples. Various substitutions or changes made according to common technical knowledge and customary means in the art without departing from the above technical ideas of the present invention should be included in the scope of the present invention.

[0022] Embodiment 1: The debris flow blocking the river and forming a dam is recorded as a debris flow dam. The predicted debris flow blocking the river and forming a dam geometry in this embodiment mainly involves the height, length and volume of the debris flow dam.

[0023] Therefore, this embodiment provides a method for predicting the geometric shape of debris flow dams, which collects original data based on the properties of the debris flow, the hydrodynamic conditions of the main river, the boundary resistance, the main river morphology, and the debris flow ditch morphology, and predicts the accumulation height, accumulation length, and volume of the debris flow dam.

[0024] Furthermore, the prediction model constructed based on the technical ideas disclosed in the prediction method includes three modules: a debris flow dam accumulation height calculation unit, a debris flow dam accumulation length calculation unit and a debris flow dam volume calculation unit. After the original data collected according to the debris flow properties, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow ditch morphology are input into the prediction model, the prediction results of the debris flow dam accumulation height, debris flow dam accumulation length, and debris flow dam volume are output.

[0025] First of all, the method for predicting the geometric shape of debris flow blocking a river and forming a dam provided in this embodiment is different from the prior art in that it simultaneously considers the effects of factors such as the nature of the debris flow, the flow of the main river, the boundary resistance, and the ditch morphology on the process of river blocking and forming a dam, and reconstructs a prediction model for the geometric shape of debris flow blocking a river and forming a dam, that is, a prediction model for the geometric shape of debris flow blocking a river and forming a dam.

[0026] Secondly, the existing calculation of dam height can be achieved by analyzing the volume, accumulation angle and cross-sectional morphology of debris flow accumulation, but such methods are only applicable to post-disaster scene investigations, for example: obtaining actual dam parameters through remote sensing and drone aerial survey technology, and investigating the already formed barrier dams. However, the risk assessment of debris flow blocking the river emphasizes accurate prediction and assessment in advance, so it is necessary to predict the geometric morphology of the debris flow before it blocks the river and forms a dam.

[0027] Furthermore, the prior art with patent publication number CN116401746A in the background technology is predicted by a method combining physical model experiments and numerical simulations; the prediction method for the geometric shape of debris flow blocking the river and forming a dam provided in this embodiment not only takes into account the influence of the main river flow on the movement of the debris flow after entering the main river, but also derives the accumulation length of the debris flow dam based on the principle of conservation of momentum, which is more theoretical. Compared with physical model experiments and numerical simulation methods, the prediction based on the technical ideas described in this embodiment is faster.

[0028] 1. Describe in detail the method for predicting the accumulation height of debris flow dams.

[0029] Taking into account the influence of debris flow properties, main river hydrodynamic conditions, and boundary resistance on the movement and accumulation process of debris flow, the calculation expression of debris flow discharge distance is derived based on the momentum conservation theorem: (Formula 1) (Formula 2) (Formula 3) In the formula, L df To clear the distance for the debris flow; U ,G All are intermediate variables; u df , h df They are the average velocity and average depth of debris flow, respectively, and are usually calculated according to the formula in Appendix J of the Standard for Engineering Investigation of Debris Flow Prevention and Control (T / CAGHP 006-2018); i t , i m They are the average longitudinal slope of the debris flow channel and the average slope of the main riverbed, which are usually obtained through actual investigation or remote sensing. g is the acceleration due to gravity, take 9.8 m / s 2 ; r w , r df They are the bulk density of the main river flow and the bulk density of debris flow, which are usually calculated based on actual measurements or existing theoretical or empirical formulas; h w The depth of the main river, usually obtained by actual measurement; x The distance of debris flow accumulation in the main river, usually the width of the main river channel; C D is the resistance coefficient, usually taken as 0.003; s is the density of the solid matter in the debris flow, which can be obtained by actual measurement, or 2650 kg / m 3 ; r is the density of the liquid in the debris flow, usually based on the density of clean water 1000 kg / m 3 calculate; C df is the solid volume fraction of debris flow, usually obtained from actual measurements; f k It is the kinematic friction angle of debris flow, which is usually obtained through case inversion analysis of similar basins, or is taken within the range of 15°-31° based on experience.

[0030] The distance of the above debris flow L dfIt is the calculation result under the assumption that there is no constraint on the opposite bank of the river (infinite width). In order to obtain the actual debris flow accumulation height in the channel, it is assumed that the axial direction of the branch channel is backfilled with the same slope. The backfill slope of the accumulation body surface is recorded as i df .

[0031] The siltation slope of the debris flow accumulation area or the residual body in the flow area can be directly measured through field investigation as the siltation slope of the accumulation body surface. i df , or it can be calculated based on existing theoretical formulas or experience. For example, in the absence of field survey data, the formula recommended in Article 8.1.2.6 of the Code for Design of Debris Flow Prevention and Control Engineering (Trial) (T / CAGHP021-2018) can be used for calculation: (Formula 4) In the formula, i df The siltation slope of the accumulation surface; i The original slope of the channel. In a blocked river, the longitudinal slope of the main channel along the direction of debris flow is usually taken. i mx ; f It is the internal friction angle of debris flow; the angle is generally 4~10° for viscous debris flow and 1~3° for dilute debris flow.

[0032] Furthermore, according to the distance of the debris flow, L df and the siltation slope of the accumulation surface i df The maximum accumulation height of the debris flow dam is calculated to be located at the intersection of the branch ditch and the main river, and it satisfies: H max = L df ×tan( i df - i mx ) (Formula 5) In the formula, H max is the maximum accumulation height on the dam crest; L df To clear the distance for the debris flow; i df It is the slope of siltation; i mx It is the longitudinal slope of the main river channel along the direction of debris flow movement.

[0033] Before determining the minimum accumulation height of debris flow dam, it is necessary to calculate the river blocking determination coefficient according to formula 6: C r : (Formula 6) In the formula, C r is the river blocking determination coefficient; Q df is the flow rate of debris flow, usually calculated based on field surveys; Q m The flow rate of the main river is usually calculated based on field surveys; u df is the velocity of the debris flow, usually obtained from field investigation or calculation; u m The flow rate of the main river is usually obtained from field surveys or calculations; V df The total amount of material flushed out by a debris flow, usually calculated according to the formula in Appendix J of the Standard for Engineering Investigation of Debris Flow Prevention and Control (T / CAGHP 006-2018); r df is the bulk density of debris flow, which is usually calculated based on actual measurements or existing theoretical or empirical formulas; g is the acceleration due to gravity, which is 9.8 m / s 2 ; h w The depth of the main river, usually obtained by actual measurement; B m The width of the main channel, usually obtained from field measurements or remote sensing images; B t is the width of the debris flow gully, usually obtained from field measurements or remote sensing images; t d is the yield stress of debris fluid, which is usually obtained by field survey or calculation based on empirical formula; n The roughness of the main riverbed is usually obtained from the roughness coefficient table in the Hydraulic Calculation Manual; i mt It is the angle between the debris flow channel and the main river channel, usually obtained from field measurements or remote sensing images.

[0034] Formula 6 is established based on a large amount of experimental data after regression analysis.

[0035] The minimum and maximum stacking heights on the dam crest can be expressed as H min = y × H max express.

[0036] Determination coefficient of river blocking C r When it is less than 5.3, it indicates that there is no obvious upwelling phenomenon after the debris flow reaches the other side, and the minimum accumulation height of the dam top H min Located on the other side of the river, y<1.

[0037] More specifically, the proportionality factor y = - ( B m / sin i mt )×tan( i df - i mx ).

[0038] Determination coefficient of river blocking C r When ≥5.3, it indicates that after the debris flow reaches the other side, there is an obvious upsurge phenomenon, and the slope of the dam top is close to a flat slope. At this time, the ratio coefficient of the minimum accumulation height of the dam top to the maximum accumulation height of the dam top is y =1, that is, the minimum accumulation height of the dam top H min Directly take the maximum accumulation height of the dam crest calculated by formula 5 H max .

[0039] The definition of dam height in this field is: the vertical distance from the lowest point of the dam crest to the dam bottom. H min As the accumulation height of debris flow dam H d The predicted value output is H min = H d .

[0040] After sorting, the accumulation height of debris flow dam is calculated according to formula 7: (Formula 7) In the formula, H d is the accumulation height of debris flow dam; H max is the maximum accumulation height on the dam crest; H min is the minimum accumulation height on the dam crest; L df To clear the distance for the debris flow; i df is the siltation slope of the accumulation surface; i mt It is the angle between the debris flow channel and the main river channel, usually obtained from field measurements or remote sensing images; i mx is the longitudinal slope of the main river channel along the direction of debris flow movement; y is the ratio coefficient between the minimum accumulation height on the dam crest and the maximum accumulation height on the dam crest, and y ≤1.

[0041] It should be noted that the longitudinal slope of the main river channel along the direction of debris flow movement is i mx The actual value of is relatively small, generally not exceeding 1°, and is usually regarded as 0° in simplified calculations, thereby simplifying the calculations of Equations 5 and 7; however, if the siltation slope of the accumulation surface is i df When it is not obtained through field measurement but calculated through Equation 4, the longitudinal slope of the main river channel along the direction of debris flow movement is i mx Substitute the specific values ​​measured on site.

[0042] 2. Describe in detail the method for predicting the accumulation length of debris flow dams.

[0043] When predicting the accumulation length of debris flow dam, the width of the debris flow ditch is used as the dam crest width of the debris flow dam, and the sum of the downstream dam length of the debris flow dam, the upstream dam length of the debris flow dam and the dam crest width of the debris flow dam is the accumulation length of the debris flow dam.

[0044] According to the mechanical balance analysis, the hydrostatic pressure of the reservoir water body is considered in the upstream of the dam body, while the water body effect is not considered in the downstream dam body. In addition to the gravity, lateral pressure, shear force, etc. of the debris flow, the accumulation length of the downstream and upstream dam bodies along the river channel is established. L d , L u Expressions 8, 9, 10, and 11: (Formula 8) (Formula 9) (Formula 10) (Formula 11) In the formula, L d is the downstream dam length of the debris flow dam; L u is the upstream dam length of the debris flow dam; C 1 , C 2 is the integration constant; K is the lateral pressure coefficient of debris flow accumulation body, which is 0.95~0.98; r df is the bulk density of debris flow, which is usually calculated based on actual measurements or existing theoretical or empirical formulas; r w The bulk density of the main river water, usually calculated based on actual measurements or existing theoretical or empirical formulas; g is the acceleration due to gravity, which is 9.8 m / s 2 ; i m The average slope of the bed of the main channel; t d is the yield stress of debris fluid; h w For the river of the Lord is deep; h is the debris flow accumulation height, and the debris flow dam accumulation height is taken as H d Perform calculations.

[0045] Furthermore, the width of the debris flow ditch is regarded as the crest width of the debris flow dam. The length of the debris flow dam along the river is the sum of the downstream dam length of the debris flow dam, the upstream dam length of the debris flow dam, and the crest width of the debris flow dam, which is also the accumulation length of the debris flow dam.

[0046] Therefore, the length of debris flow dam accumulation L The expression 12 is: L=L d +L u +Bt (Formula 12) In the formula, L is the accumulation length of debris flow dam; L d is the downstream dam length of the debris flow dam; L u is the upstream dam length of the debris flow dam; B t It is the crest width of the debris flow dam.

[0047] 3. Describe in detail the method for predicting the volume of debris flow dam.

[0048] When predicting the volume of debris flow dam, based on the idea of ​​integration and through regression analysis, calculation is performed according to the maximum accumulation height on the dam crest, the minimum accumulation height on the dam crest, the downstream dam length of the debris flow dam, the upstream dam length of the debris flow dam, the width of the debris flow ditch, the width of the main river channel, and the longitudinal section area of ​​the debris flow dam.

[0049] A large number of field and indoor water tank experiments show that the longitudinal section of the debris flow dam is curved. By extracting the longitudinal section data and performing regression analysis, the calculation formula for the accumulation volume of the debris flow dam was established, as shown in Equation 13 and Equation 14: (Formula 13) (Formula 14) In the formula, V is the volume of debris flow dam; S is the longitudinal section area of ​​the debris flow dam; H a is the average height of the crest of the debris flow dam, H a =( H min + H max ) / 2; H d is the accumulation height of debris flow dam; L d is the downstream dam length of the debris flow dam; L u is the upstream dam length of the debris flow dam; l u , l dare the integral lengths of the upstream and downstream dam bodies respectively; B t is the width of the debris flow gully; B m The width of the main river channel.

[0050] The target parameters output by the prediction model have an important impact on the risk assessment of the debris flow blocking river disaster chain. It is mainly reflected in the following three aspects: 1) The geometric shape formed by the debris flow dam directly affects the stability of the dam. If the dam is higher or the length along the river is shorter, the overall stability of the dam body is lower, the risk of breach is higher, and the erosion rate and peak flow during the breach process are greater; 2) The higher the debris flow dam, the greater the flooding range and depth upstream, and the greater the losses caused; 3) The higher the dam, the greater the flood flow formed after the breach, and the greater the flood impact and flooding degree downstream.

[0051] In summary, the prediction results obtained by the prediction method and prediction model provided in this embodiment are more accurate, thereby improving the accuracy of risk assessment of the debris flow blocking river disaster chain.

[0052] Embodiment 2: This embodiment describes in detail the method for predicting the accumulation height of debris flow dam on the basis of the first embodiment.

[0053] First, in order to explain the main structural parameters of debris flow dam, such as Figure 1 , Figure 2 , Figure 3 , which illustrates the structure of a debris flow dam. In the process of debris flow blocking the river and forming a dam, debris fluid 4 rushes into the main river channel 3 from the debris flow ditch 1 and accumulates continuously at the intersection of the debris flow ditch 1 and the main river channel 3, thus forming a debris flow dam 2.

[0054] During the risk assessment of a debris flow gully, it was found that the debris flow gully was at risk of a large-scale debris flow. In order to further assess the risk of the debris flow in the gully blocking the river and bursting, it was necessary to predict the geometric shape of the dam.

[0055] After field investigation, the following basic parameters were obtained: average flow velocity of debris flow ( u df ) is 9.75 m / s, and the average mud depth ( h df ) is 3.88 m, and the bulk density of debris flow ( r df ) is 1.86 t / m 3 , median particle size of debris flow ( d 50 ) is 120 mm, the yield stress of debris fluid ( td ) is 2593.63 Pa, and the average longitudinal slope of the debris flow channel is ( i t ) is 4°, the peak flow rate of debris flow ( Q df ) is 755.5m 3 / s, debris flow channel width ( B t ) is 20m, the volume concentration of debris flow ( C df ) is 0.521, the flow of the main river ( Q m ) is 751 m 3 / s, the total amount of material flushed out by a debris flow ( V df ) is 8.5×10 5 m 3 , the width of the main channel ( B m ) is 80m, the main riverbed roughness ( n ) is 0.045, the main river depth ( h w ) is 2.0 m, the main river flow density ( r w ) is 1000 kg / m 3 , the average flow velocity of the main river ( u m ) is 5 m / s, and the siltation slope of the debris flow deposit is ( i df ) is 3.90°, and the angle between the debris flow channel and the main river channel ( i mt ) is 90°, and the average slope of the bottom of the main river channel is ( i m ) is 0.57°, and the longitudinal slope of the main river channel along the direction of debris flow movement ( i mx ) is 0°.

[0056] The method described in Example 1 is now used to predict the geometric shape of the debris flow dam in the ditch.

[0057] First, u df = 9.75 m / s; h df = 3.88 m; i t = 4°; i m = 0.57°; g = 9.8 m / s 2 ; rw = 1000kg / m 3 ; r df = 1.86 t / m 3 ; h w = 2.0 m; x = B m =80m; C D =0.003; s =2650 kg / m 3 ; r =1000 kg / m 3 ; f k =18°; C df = 0.521 Substitute into equation 1, equation 2, and equation 3 to calculate the movement distance of the debris flow in the main river, that is, the distance of the debris flow out is calculated. L df =89.4m.

[0058] Further, L df =89.4m; i df = 3.90°; i mx = 0° Substitute into formula 5 to calculate the maximum accumulation height on the dam crest H max =6.26 m.

[0059] Further, according to the above parameters, Q df = 755.5 m 3 / s; Q m = 751 m 3 / s; u df = 9.75 m / s; u m = 5 m / s; V df = 8.5 × 10 5 m 3 ; r df = 1.86 t / m 3 ; h w = 2.0 m; B m = 80 m; B t= 20 m; t d = 2593.63 Pa; n =0.045; i mt = 90° Substituting into formula 6, we get C r =19.1.

[0060] Since the river blocking determination coefficient C r is greater than 5.3, and is substituted into formula 7 to obtain the accumulation height of the debris flow dam. H d is 6.26 m.

[0061] Secondly, the length of the downstream dam of the debris flow dam is calculated according to equations 8, 9, 10 and 11: L d , the length of the upstream dam of the debris flow dam L u 180.4 m and 130.2 m respectively. B t Assuming it as the dam crest width, substitute it into formula 12 to calculate the accumulation length of the debris flow dam L It is 334.6 m.

[0062] Furthermore, the volume of the debris flow dam is calculated according to equations 13 and 14: V is 13.52×10 4 m³.

[0063] The other parts of this embodiment are the same as those of Embodiment 1, and thus will not be described in detail.

[0064] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification or equivalent change made to the above embodiment according to the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for predicting the geometric shape of debris flow blocking a river and forming a dam, characterized in that: The original data are collected based on the properties of debris flow, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow ditch morphology to predict the accumulation height, accumulation length, and volume of the debris flow dam.

2. A method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 1, characterized in that: When predicting the accumulation height of debris flow dam, the maximum accumulation height of the dam top is calculated first, and then the maximum accumulation height of the dam top is calculated according to the river blocking determination coefficient. C r The numerical value of is used to judge whether there is a high-rise phenomenon after the debris flow reaches the other side, and the minimum accumulation height of the dam top is calculated to predict the accumulation height of the debris flow dam.

3. A method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 2, characterized in that: The river blocking determination coefficient C r The calculation is based on the flow rate of the debris flow, the flow rate of the main river, the flow velocity of the debris flow, the flow velocity of the main river, the total amount of material flushed out by a debris flow, the specific gravity of the debris flow, the water depth of the main river, the width of the main river channel, the width of the debris flow ditch, the yield stress of the debris flow, the roughness of the main riverbed, the debris flow ditch outlet, and the angle of the main river channel.

4. A method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 3, characterized in that: The river blocking determination coefficient C r The calculation formula is as follows: In the formula, C r is the river blocking determination coefficient; Q df is the flow rate of debris flow; Q m for the flow of the main river; u df is the velocity of the debris flow; u m The flow rate of the main river; V df The total amount of material flushed out by a debris flow; ρ df is the bulk density of debris flow; g is the acceleration due to gravity; h w For the river of the Lord is deep; B m The width of the main channel; B t is the width of the debris flow gully; τ d is the yield stress of debris fluid; n Main riverbed roughness; θ mt It is the angle between the debris flow channel and the main river channel.

5. The method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 2, characterized in that: The minimum accumulation height on the dam top and the maximum accumulation height on the dam top are calculated based on the distance of the debris flow, the siltation slope on the surface of the accumulation body, the longitudinal slope of the main river channel along the direction of debris flow movement, and the width of the main river channel.

6. A method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 5, characterized in that: The calculation formula for the maximum accumulation height of the dam top is as follows: H max = L df ×tan( θ df - θ mx ); The calculation formula for the minimum accumulation height of the dam top is as follows: H min = y × H max ； In the formula, H max is the maximum accumulation height on the dam crest; H min is the minimum accumulation height on the dam crest; L df Distance for debris flow; θ df is the siltation slope of the accumulation surface; θ mx is the longitudinal slope of the main river channel along the direction of debris flow movement; y is the ratio coefficient between the minimum accumulation height on the dam crest and the maximum accumulation height on the dam crest, and y ≤1.

7. A method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 6, characterized in that: When the river blocking determination coefficient is greater than the river blocking determination empirical value, the debris flow will surge after reaching the other side. y =1; When the river blocking determination coefficient is less than or equal to the river blocking determination empirical value, there will be no high-rise phenomenon after the debris flow reaches the other side. y <1 and satisfies: y = - ( B m / sin θ mt )×tan( θ df - θ mx ); In the formula, B m The width of the main channel; θ mt It is the angle between the debris flow channel and the main river channel.

8. The method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 1, characterized in that: When predicting the accumulation length of debris flow dam, the width of the debris flow ditch is used as the dam crest width of the debris flow dam, and the sum of the downstream dam length of the debris flow dam, the upstream dam length of the debris flow dam and the dam crest width of the debris flow dam is the accumulation length of the debris flow dam.

9. The method for predicting the geometric shape of debris flow blocking a river and forming a dam according to claim 1, characterized in that: When predicting the volume of debris flow dam, based on the idea of ​​integration and through regression analysis, calculation is performed according to the maximum accumulation height on the dam crest, the minimum accumulation height on the dam crest, the downstream dam length of the debris flow dam, the upstream dam length of the debris flow dam, the width of the debris flow ditch, the width of the main river channel, and the longitudinal section area of ​​the debris flow dam.

10. A prediction model for the geometric shape of debris flow blocking a river and forming a dam, characterized in that: It includes a debris flow dam accumulation height calculation unit, a debris flow dam accumulation length calculation unit and a debris flow dam volume calculation unit; Based on the original data collected from the properties of debris flow, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow ditch morphology as input, the debris flow dam accumulation height is predicted by the debris flow dam accumulation height calculation unit, the debris flow dam accumulation length is predicted by the debris flow dam accumulation length calculation unit, and the debris flow dam volume is predicted by the debris flow dam volume calculation unit.

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