A prediction method and prediction model for the geometric shape of debris flow damming a river

Abstract

The present invention relates to the technical field of disaster prevention and mitigation engineering, and particularly relates to a prediction method and a prediction model for the geometric shape of a debris flow dam formed by blocking a river. The prediction method collects original data according to the properties of the debris flow, the hydrodynamic conditions of the main river, the boundary resistance, the morphology of the main river, and the morphology of the debris flow gully, and predicts the accumulation height, the accumulation length, and the volume of the debris flow barrier dam, with high prediction accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of disaster prevention and mitigation engineering, and particularly relates to a method and a prediction model for predicting the geometric shape of a debris flow blocking a river to form a dam. Background Technique

[0002] Debris flow is a special fluid between Newtonian fluid and non-Newtonian fluid, with characteristics such as suddenness, high energy and high destructiveness, high solid matter and boulder content, making debris flow a highly dangerous natural disaster, seriously threatening the lives and property safety of local people. When a large amount of debris flow flows into the main river, it will also block the main river, forming a barrier lake of a certain scale, and then causing inundation disasters in the reservoir area of the barrier lake and downstream disasters of the flood caused by the breach of the barrier dam, further amplifying the losses of debris flow disasters.

[0003] At present, some studies have summarized and disclosed some empirical formulas for predicting the possibility of a river being blocked after a debris flow outbreak; there are also some studies, such as: a Chinese invention patent with the patent publication number CN116401746A, which discloses a method for predicting the geometric shape parameters of a barrier dam, obtains physical parameters and topographic and geomorphic parameters to establish a calculation model for the formation process of the barrier dam, and analyzes the influence of landslide volume, sliding surface inclination angle, natural angle of repose of the landslide body, and landslide body speed on the geometric shape parameters of the barrier dam through data simulation to obtain a fitting formula. However, such existing technologies do not consider the influence of the main river flow on the movement of debris flow after the debris flow enters the main river, resulting in a reduction in the prediction accuracy of the geometric shape of the barrier dam. Summary of the Invention

[0004] Aiming at the deficiency that the prediction accuracy of the geometric shape of the existing barrier dam needs to be improved, the present invention provides a method and a prediction model for predicting the geometric shape of a debris flow blocking a river to form a dam, considering the influence of debris flow properties, main river hydrodynamic conditions, and boundary resistance on the movement and accumulation process of debris flow, and deriving the dam height, dam length, and dam body volume of the debris flow barrier dam based on the momentum conservation theorem to predict the geometric shape of the debris flow blocking a river to form a dam and improve the prediction accuracy.

[0005] The present invention provides a method for predicting the geometric shape of a debris flow blocking a river to form a dam, collects original data according to debris flow properties, main river hydrodynamic conditions, boundary resistance, main river topography, and debris flow gully topography, and predicts the accumulation height of the debris flow barrier dam, the accumulation length of the debris flow barrier dam, and the volume of the debris flow barrier dam.

[0006] Further, in order to better implement the present invention, when predicting the accumulation height of the debris flow barrier dam, first calculate the maximum accumulation height at the dam crest, and then according to the river-blocking determination coefficient C rDetermine numerically whether there is a phenomenon of overtopping after the debris flow reaches the opposite bank, so as to calculate the minimum accumulated height of the dam crest, and thus predict the accumulated height of the debris flow barrier dam.

[0007] Further, in order to better implement the present invention, the river-blocking determination coefficient C r is calculated through 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 debris flushed out by a single debris flow, the unit weight of the debris flow, the depth of the main river water, the width of the main river channel, the width of the debris flow ditch, the yield stress of the debris flow body, the roughness coefficient of the main river bed, the angle between the debris flow outlet and the main river channel.

[0008] Further, in order to better implement the present invention, the minimum accumulated height of the dam crest and the maximum accumulated height of the dam crest are both calculated according to the debris flow flushing distance, the back-silting slope of the surface of the accumulation body, the longitudinal slope of the main river channel along the movement direction of the debris flow, and the width of the main river channel.

[0009] Further, the minimum accumulated height of the dam crest and the maximum accumulated height of the dam crest are both calculated according to the debris flow flushing distance, the back-silting slope of the surface of the accumulation body, the longitudinal slope of the main river channel along the movement direction of the debris flow, and the width of the main river channel.

[0010] The present invention also provides a prediction model for the geometric shape of a debris flow river-blocking dam, including a debris flow barrier dam accumulated height calculation unit, a debris flow barrier dam accumulated length calculation unit, and a debris flow barrier dam volume calculation unit;

[0011] Taking the original data collected according to the debris flow properties, the main river hydrodynamic conditions, the boundary resistance, the main river morphology, and the debris flow ditch morphology as inputs, predicting the accumulated height of the debris flow barrier dam through the debris flow barrier dam accumulated height calculation unit, predicting the accumulated length of the debris flow barrier dam through the debris flow barrier dam accumulated length calculation unit, and predicting the volume of the debris flow barrier dam through the debris flow barrier dam volume calculation unit.

[0012] The beneficial effects of the present invention are as follows.

[0013] (1) The prediction method for the geometric shape of a debris flow river-blocking dam provided by the present invention considers the influence of debris flow properties, main river hydrodynamic conditions, and boundary resistance on the movement and accumulation process of the debris flow, improves the prediction accuracy, and the calculation results are more reliable.

[0014] (2) The prediction method for the geometric shape of a debris flow river-blocking dam provided by the present invention derives the dam height, dam length, and dam body volume of the debris flow barrier dam based on the momentum conservation theorem, and the calculation process is simpler and faster than that of physical model experiments and numerical simulation methods.

[0015] (3) A prediction method for the geometric shape of a debris flow dam formed by blocking a river provided by the present invention, the predicted parameters involve the key parameters of the geometric shape of the debris flow barrier dam, including the dam height, total dam length, upstream dam length, downstream dam length, and volume of the debris flow barrier dam, providing important basic data for the risk assessment of the debris flow barrier dam.

[0016] (4) A prediction model for the geometric shape of a debris flow dam formed by blocking a river provided by the present invention has the advantages of strong theory, clear calculation process, and fast solution speed.

[0017] (5) A prediction method and prediction model for the geometric shape of a debris flow dam formed by blocking a river provided by the present invention are mainly used for predicting the dam formation by blocking a river before the occurrence of a debris flow disaster, which is an important link in risk assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a plan view of the debris flow barrier dam in Embodiment 2.

[0019] Figure 2 is Figure 1 the longitudinal sectional view of the debris flow barrier dam at the T-T section in

[0020] Figure 3 is Figure 1 the longitudinal sectional view of the debris flow barrier dam at the M-M section in

[0021] In the figure: 1. Debris flow gully; 2. Debris flow barrier dam; 3. Main river channel; 4. Debris flow body. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0022] The following further details the above content of the present invention in conjunction with the specific implementation manners of the embodiments. However, this should not be construed as limiting the scope of the above subject matter of the present invention to the following examples. Without departing from the above technical ideas of the present invention, various substitutions or changes made according to ordinary technical knowledge and conventional means in the art shall be included within the scope of the present invention.

[0023] Embodiment 1:

[0024] The debris flow dam formed by blocking a river is denoted as a debris flow barrier dam. In this embodiment, the predicted geometric shape of the debris flow dam formed by blocking a river mainly involves the height, length, and volume of the debris flow barrier dam.

[0025] Thus, this embodiment provides a prediction method for the geometric shape of a debris flow dam formed by blocking a river, which collects original data according to the debris flow properties, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow gully morphology, and predicts the accumulated height, accumulated length, and volume of the debris flow barrier dam.

[0026] Further, the prediction model constructed based on the technical idea disclosed by the prediction method includes three major modules: a debris flow barrier dam accumulation height calculation unit, a debris flow barrier dam accumulation length calculation unit, and a debris flow barrier 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 gully morphology are input into the prediction model, the prediction results of the debris flow barrier dam accumulation height, debris flow barrier dam accumulation length, and debris flow barrier dam volume are output.

[0027] First of all, the prediction method for the geometric shape of debris flow blocking the river to form a dam provided in this embodiment, compared with the prior art, the most important difference is that it simultaneously considers the influence of debris flow properties, main river flow, boundary resistance, and river gully morphology on the process of blocking the river to form a dam, and reconstructs the prediction model for the geometric shape of debris flow blocking the river to form a dam, that is, the prediction model for the geometric shape of debris flow blocking the river to form a dam.

[0028] Secondly, the existing calculation of the dam height can be achieved by analyzing the volume, accumulation angle of the debris flow deposit, and the river channel cross-section morphology. However, such methods are only applicable to the investigation of post-disaster scenarios. For example, the actual dam body parameters are obtained through remote sensing and UAV aerial survey technologies to investigate the formed barrier dam. However, the risk assessment of debris flow blocking the river and bursting emphasizes accurate prediction and assessment before the event. Therefore, it is necessary to predict the geometric shape of the debris flow blocking the river to form a dam before it occurs.

[0029] Furthermore, the prior art with the patent publication number CN116401746A in the background technology predicts by combining physical model experiments and numerical simulations; the prediction method for the geometric shape of debris flow blocking the river to form a dam provided in this embodiment not only considers the influence of the main river flow on the movement of the debris flow after entering the main river, but also derives the debris flow barrier dam accumulation length based on the principle of conservation of momentum, which has stronger theoreticality. Compared with the physical model experiment and numerical simulation methods, the prediction based on the technical idea described in this embodiment is faster.

[0030] I. Describe in detail the prediction method for the accumulation height of the debris flow barrier dam.

[0031] Comprehensively considering the influence of debris flow properties, main river hydrodynamic conditions, and boundary resistance on the debris flow movement and accumulation process, the calculation expression for the debris flow runout distance is derived based on the theorem of conservation of momentum:

[0032] (Equation 1)

[0033] (Equation 2)

[0034] (Equation 3)

[0035] In the formula, Ldf is the scouring distance of debris flow;

[0036] U 、 G are all intermediate variables;

[0037] u df 、 h df are the average flow velocity and average flow depth of debris flow respectively, usually calculated according to the formula in Appendix J of the "Code for Investigation of Debris Flow Control Engineering Standards" (T / CAGHP 006 - 2018);

[0038] θ t 、 θ m are the average longitudinal slope of the debris flow channel and the average slope of the main riverbed respectively, usually obtained by means of on - site investigation or remote sensing, etc.;

[0039] g is the acceleration due to gravity, taking 9.8 m / s 2 ;

[0040] ρ w 、 ρ df are the unit weight of the main river water flow and the unit weight of debris flow respectively, usually calculated according to actual measurement or existing theories or empirical formulas;

[0041] h w is the water depth of the main river, usually obtained by actual measurement;

[0042] x is the deposition distance of debris flow in the main river, usually taking the width of the main river channel;

[0043] C D is the resistance coefficient, usually taking 0.003;

[0044] σ is the density of the solid matter of debris flow, obtained by actual measurement, or taking 2650 kg / m 3 ;

[0045] ρ is the density of the liquid in debris flow, usually calculated according to the density of clear water 1000 kg / m 3 ;

[0046] C df is the solid volume fraction of debris flow, usually obtained by actual measurement;

[0047] φ k is the movement friction angle of the debris flow body, which is usually obtained through inverse analysis of cases in similar river basins or is taken within the range of 15°-31° according to experience.

[0048] The above-mentioned debris flow runout distance L df is the calculation result under the assumption that there is no constraint on the opposite bank of the river channel (infinite width). In order to obtain the debris flow accumulation height in the actual channel, it is assumed that the back-silting and accumulation occur along the same slope in the direction of the branch channel axis. The back-silting slope of the accumulation body surface is denoted as θ df .

[0049] The back-silting slope of the accumulation body surface can be directly measured through on-site inspection of the back-silting slope of the remaining body in the debris flow accumulation area or the flow-through area. θ df It can also be calculated according to existing theoretical formulas or experience. For example, in the case of no on-site inspection data, the formula recommended in Clause 8.1.2.6 of the "Design Code for Debris Flow Prevention and Control Engineering (Trial)" (T / CAGHP021-2018) can be used for calculation:

[0050] (Equation 4)

[0051] In the formula, θ df is the back-silting slope of the accumulation body surface;

[0052] θ is the original slope of the channel, and in the Du River, the longitudinal slope of the main river channel along the direction of debris flow movement is usually taken. θ mx ;

[0053] φ is the internal friction angle of the debris flow; generally, it is 4~10° for viscous debris flow and 1~3° for dilute debris flow.

[0054] Furthermore, based on the debris flow runout distance L df and the back-silting slope θ df of the accumulation body surface, it can be calculated that the maximum accumulation height of the debris flow barrier dam is located at the confluence of the branch channel and the main river and satisfies:

[0055] H max = L df ×tan( θ df - θ mx ) (Equation 5)

[0056] In the formula, H max is the maximum stacking height at the dam crest;

[0057] L df is the outrush distance of debris flow;

[0058] θ df is the silting slope;

[0059] θ mx is the longitudinal slope of the main river channel along the direction of debris flow movement.

[0060] Before determining the minimum stacking height of the debris flow barrier dam, it is necessary to calculate the river-blocking judgment coefficient according to Equation 6 C r :

[0061] (Equation 6)

[0062] In the formula, C r is the river-blocking judgment coefficient;

[0063] Q df is the flow rate of the debris flow, usually obtained by on-site investigation and calculation;

[0064] Q m is the flow rate of the main river, usually obtained by on-site investigation and calculation;

[0065] u df is the flow velocity of the debris flow, usually obtained by on-site investigation or calculation;

[0066] u m is the flow velocity of the main river, usually obtained by on-site investigation or calculation;

[0067] V df is the total amount of debris flow outrush material at one time, usually calculated according to the formula in Appendix J of the "Code for Investigation of Debris Flow Control Engineering" (T / CAGHP 006-2018);

[0068] ρ df is the debris flow density, usually calculated according to actual measurement or existing theoretical or empirical formulas;

[0069] g is the acceleration due to gravity, which is 9.8 m / s 2 ;

[0070] h w The main river depth is usually obtained through actual measurement;

[0071] B m The width of the main river channel is usually obtained based on on-site measurement or remote sensing images;

[0072] B t The width of the debris flow gully is usually obtained based on on-site measurement or remote sensing images;

[0073] τ d The yield stress of the debris flow body is usually obtained through field investigation measurement or calculation using empirical formulas;

[0074] n The roughness coefficient of the main riverbed is usually obtained by referring to the roughness coefficient table in the "Hydraulic Calculation Manual";

[0075] θ mt The angle between the debris flow gully and the main river channel is usually obtained based on on-site measurement or remote sensing images.

[0076] Equation 6 is established based on a large amount of experimental data through regression analysis.

[0077] The minimum accumulation height and the maximum accumulation height of the dam crest can be represented by H min = y × H max indicated.

[0078] When the river-blocking judgment coefficient C r <5.3, it indicates that after the debris flow reaches the opposite bank, there is no obvious overtopping phenomenon, and the minimum accumulation height of the dam crest H min is located on the opposite bank of the river channel, and at this time y < 1.

[0079] More specifically, the proportional coefficient y = - ( B m / sin θ mt )×tan( θ df - θ mx ).

[0080] When the river-blocking judgment coefficient C rWhen it is ≥ 5.3, it indicates that after the debris flow reaches the opposite bank, there is an obvious phenomenon of rushing up, and the slope of the dam crest is close to a flat slope. At this time, the proportional coefficient of the minimum accumulation height to the maximum accumulation height of the dam crest y = 1, that is, the minimum accumulation height of the dam crest H min directly takes the maximum accumulation height of the dam crest calculated by Equation 5 H max .

[0081] In this field, the definition of the dam height is: the vertical distance from the lowest point of the dam crest to the dam bottom. Therefore, taking the predicted minimum accumulation height of the dam crest H min as the predicted value of the accumulation height of the debris flow barrier dam output, that is H d = H min = H d .

[0082] After sorting, calculate the accumulation height of the debris flow barrier dam according to Equation 7:

[0083] (Equation 7)

[0084] In the formula, H d is the accumulation height of the debris flow barrier dam;

[0085] H max is the maximum accumulation height of the dam crest;

[0086] H min is the minimum accumulation height of the dam crest;

[0087] L df is the rushing-out distance of the debris flow;

[0088] θ df is the back-silting slope of the surface of the accumulation body;

[0089] θ mt is the included angle between the debris flow channel and the main river channel, usually obtained according to on-site measurement or remote sensing images;

[0090] θ mx is the longitudinal slope of the main river channel along the movement direction of the debris flow;

[0091] y is the proportional coefficient of the minimum accumulation height to the maximum accumulation height of the dam crest, and y ≤ 1.

[0092] It should be noted that the longitudinal slope of the main river channel along the direction of debris flow movement θ mx has a relatively small actual value, generally not exceeding 1°, and is usually regarded as 0° in simplified calculations, so as to simplify the calculations of Equation 5 and Equation 7; however, if the silting slope θ df of the accumulation body surface is not obtained through on-site measurement but through calculation using Equation 4, the longitudinal slope of the main river channel along the direction of debris flow movement θ mx shall be substituted with the specific measured value.

[0093] II. The prediction method of the accumulation length of the debris flow barrier dam is described in detail.

[0094] When predicting the accumulation length of the debris flow barrier dam, the width of the debris flow gully is used as the crest width of the debris flow barrier dam, and the sum of the downstream dam body length, the upstream dam body length, and the crest width of the debris flow barrier dam is the accumulation length of the debris flow barrier dam.

[0095] Based on the mechanical equilibrium analysis, considering the hydrostatic pressure of the water body in the reservoir area for the upstream dam body and not considering the water body effect for the downstream dam body, together with the self-gravity, lateral pressure, shear force, etc. of the debris flow, the expressions 8, 9, 10, and 11 for the accumulation lengths of the downstream and upstream dam bodies in the direction along the river channel are established: L d 、 L u of the downstream and upstream dam bodies in the direction along the river channel are established:

[0096] (Equation 8)

[0097] (Equation 9)

[0098] (Equation 10)

[0099] (Equation 11)

[0100] In the formula, L d is the downstream dam body length of the debris flow barrier dam;

[0101] L u is the upstream dam body length of the debris flow barrier dam;

[0102] C 1、 C 2 is the integral constant;

[0103] K is the lateral pressure coefficient of the debris flow accumulation body, taking 0.95 - 0.98;

[0104] ρ df is the debris flow unit weight, usually calculated based on actual measurements or existing theories or empirical formulas;

[0105] ρ w is the main river flow unit weight, usually calculated based on actual measurements or existing theories or empirical formulas;

[0106] g is the acceleration due to gravity, which is 9.8 m / s 2 ;

[0107] θ m is the average slope of the bottom bed of the main river channel;

[0108] τ d is the yield stress of the debris flow body;

[0109] h w is the depth of the main river;

[0110] h is the debris flow accumulation height, taking the accumulation height of the debris flow dam H d for calculation.

[0111] Furthermore, the width of the debris flow gully is regarded as the crest width of the debris flow dam. The length of the debris flow dam blocking the river in the downstream direction is the sum of the downstream dam body length of the debris flow dam, the upstream dam body length of the debris flow dam, and the crest width of the debris flow dam, and is also the accumulation length of the debris flow dam.

[0112] Therefore, the accumulation length L of the debris flow dam is expressed by Equation 12 as:

[0113] L = L d +L u +B (Equation 12)

[0114] In the formula, L is the accumulation length of the debris flow dam;

[0115] L d is the downstream dam body length of the debris flow dam;

[0116] L u is the upstream dam body length of the debris flow dam;

[0117] B is the crest width of the debris flow barrier dam.

[0118] III. Detailed description of the method for predicting the volume of the debris flow barrier dam.

[0119] When predicting the volume of the debris flow barrier dam, based on the integral idea, through regression analysis, it is calculated according to the maximum accumulation height at the dam crest, the minimum accumulation height at the dam crest, the downstream dam body length of the debris flow barrier dam, the upstream dam body length of the debris flow barrier dam, the width of the debris flow gully, the width of the main river channel, and the longitudinal profile area of the debris flow barrier dam.

[0120] Through a large number of field and indoor flume experiments, it shows that the longitudinal section of the debris flow barrier dam is curved. By extracting the longitudinal section data and through regression analysis, the calculation formulas for the accumulated volume of the debris flow barrier dam are established, Formula 13 and Formula 14:

[0121] (Formula 13)

[0122] (Formula 14)

[0123] In the formula, V is the volume of the debris flow barrier dam;

[0124] S is the longitudinal profile area of the debris flow barrier dam;

[0125] H a is the average height at the dam crest of the debris flow barrier dam, H a =( H min + H max ) / 2;

[0126] H d is the accumulation height of the debris flow barrier dam;

[0127] L d is the downstream dam body length of the debris flow barrier dam;

[0128] L u is the upstream dam body length of the debris flow barrier dam;

[0129] l u 、 l d are the integral lengths of the upstream and downstream dam bodies respectively;

[0130] B t is the width of the debris flow gully;

[0131] B m is the width of the main river channel.

[0132] The target parameters output by the prediction model have an important impact on the risk assessment of debris flow damming disasters. It is mainly reflected in the following three aspects: 1) The geometric shape formed by the debris flow barrier dam directly affects the stability of the barrier dam. If the dam height is higher or the length in the river flow direction is shorter, the overall stability of the dam body is lower, the risk of breach is higher, and the erosion rate and peak flood flow during the breach process are larger; 2) The higher the debris flow barrier dam, the larger the inundation range and depth upstream, resulting in greater losses; 3) The higher the dam height, the larger the flood flow formed after the breach, and the greater the flood impact and inundation degree downstream.

[0133] 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 the risk assessment of debris flow damming disasters.

[0134] Embodiment 2:

[0135] This embodiment details the prediction method for the accumulation height of the debris flow barrier dam on the basis of Embodiment 1.

[0136] First, in order to facilitate the description of the main structural parameters of the debris flow barrier dam, such as Figure 1 , Figure 2 , Figure 3 , the structure of a debris flow barrier dam is schematically shown. During the process of debris flow damming the river to form a dam, the debris flow mass 4 rushes from the debris flow gully 1 into the main river channel 3 and continuously accumulates at the intersection of the debris flow gully 1 and the main river channel 3, thus forming the debris flow barrier dam 2.

[0137] When conducting a risk assessment on a certain debris flow gully, it is found that there is a risk of large-scale debris flow outbreaks in this debris flow gully. In order to further evaluate the risk of damming and breaching of the debris flow in this gully, it is necessary to predict the geometric shape of its damming the river to form a dam.

[0138] After on-site investigation, the following basic parameters are obtained: the average flow velocity of the debris flow ( u df ) is 9.75 m / s, the average mud depth ( h df ) is 3.88 m, the debris flow density ( ρ df ) is 1.86 t / m 3 , the median particle size of the debris flow ( d 50 ) is 120 mm, the yield stress of the debris flow mass ( τ d ) is 2593.63 Pa, the average longitudinal slope of the debris flow gullyθ t is 4°, the peak discharge of the debris flow ( Q df is 755.5 m 3 / s, the width of the debris flow gully ( B t is 20 m, the volume concentration of the debris flow ( C df is 0.521, the discharge of the main river ( Q m is 751 m 3 / s, the total amount of materials scoured by one debris flow ( V df is 8.5×10 5 m 3 , the width of the main river channel ( B m is 80 m, the roughness coefficient of the main river bed ( n is 0.045, the water depth of the main river ( h w is 2.0 m, the unit weight of the main river flow ( ρ w is 1000 kg / m 3 , the average velocity of the main river ( u m is 5 m / s, the back-silting slope of the debris flow deposit ( θ df is 3.90°, the included angle between the debris flow gully and the main river channel ( θ mt is 90°, the average slope of the bottom bed of the main river channel ( θ m is 0.57°, the longitudinal slope of the main river channel along the direction of debris flow movement ( θ mx is 0°.

[0139] Now, the geometric shape of the debris flow barrier dam in this gully is predicted using the method described in Example 1.

[0140] First, set u df = 9.75 m / s; h df = 3.88 m; θ t = 4°; θ m = 0.57°; g = 9.8 m / s 2 ; ρ w = 1000kg / m 3 ;ρ df = 1.86 t / m 3 ; h w = 2.0 m; x = B m =80m; C D =0.003; σ =2650 kg / m 3 ; ρ =1000 kg / m 3 ; φ k =18°; C df = 0.521 is substituted into Equation 1, Equation 2, and Equation 3 to calculate the movement distance of the debris flow in the main river, that is, the runout distance of the debris flow is calculated L df =89.4m.

[0141] Furthermore, L df =89.4m; θ df = 3.90°; θ mx = 0° is substituted into Equation 5 to calculate the maximum accumulation height at the dam crest H max =6.26 m.

[0142] Furthermore, 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 ; ρ df = 1.86 t / m 3 ; h w = 2.0 m; B m = 80 m; B t = 20 m; τ d= 2593.63 Pa; n = 0.045; θ mt Substitute = 90° into Equation 6 and calculate to obtain C r = 19.1.

[0143] Since the river-blocking determination coefficient C r is greater than 5.3, substitute it into Equation 7 to obtain the accumulated height of the debris flow barrier dam H d which is 6.26 m.

[0144] Secondly, calculate the length of the downstream dam body of the debris flow barrier dam and the length of the upstream dam body of the debris flow barrier dam according to Equations 8, 9, 10, and 11 L d , respectively. Then, consider the width of the debris flow channel L u as the crest width of the debris flow barrier dam B t and substitute it into Equation 12 to calculate the accumulated length of the debris flow barrier dam B which is 334.6 m. L

[0145] Furthermore, calculate the volume of the debris flow barrier dam according to Equations 13 and 14 V which is 13.52×10 4 m³.

[0146] The other parts of this embodiment are the same as those of Embodiment 1, so they will not be described in detail.

[0147] As described above, the above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention falls within the protection scope of the present invention.​

Claims

1. A prediction method for the geometric shape of a debris flow dam formed by blocking a river, characterized in that, Collect original data according to the debris flow properties, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow gully morphology, and predict the accumulation height, accumulation length, and volume of the debris flow barrier dam. When predicting the accumulation height of a debris flow dam, first calculate the maximum accumulation height of the dam crest, and then judge whether there is a phenomenon of overtopping after the debris flow reaches the opposite bank according to the value of the river-blocking judgment coefficient C r to estimate the minimum accumulation height of the dam crest, so as to predict the accumulation height of the debris flow dam; Both the minimum accumulation height and the maximum accumulation height of the dam crest are calculated based on the debris flow runout distance, the back-silting slope of the accumulation body surface, the longitudinal slope of the main river channel along the debris flow movement direction, and the width of the main river channel. The method for predicting the accumulation height of the debris flow barrier dam is as follows: When the river-blocking judgment coefficient < the river-blocking judgment empirical value, H d = H min = ( L df - B m / sin θ mt ) × tan( θ df - θ mx ) ; When the river-blocking judgment coefficient ≥ the river-blocking judgment empirical value, H d = H min = H max = L df ×tan( θ df - θ mx ); In the formula, H d is the accumulation height of the debris flow dam; H max is the maximum stacking height at the dam crest; H min is the minimum stacking height at the dam crest; L df is the outrush distance of debris flow; B m is the width of the main river channel; θ mt is the included angle between the debris flow channel and the main river channel; θ df is the back-silting slope on the surface of the accumulation body; θ mx is the longitudinal slope of the main river channel along the direction of debris flow movement; The downstream and upstream dam body accumulation lengths in the river channel direction L d 、 L u The expressions are as follows: In the formula, L d is the downstream dam body length of the debris flow barrier dam; L u is the upstream dam body length of the debris flow barrier dam; C 1、 C 2 is an integration constant; K is the lateral pressure coefficient of debris flow deposits, taking values of 0.95 to 0.98; ρ df where γ is the debris flow unit weight, which is calculated according to actual measurement or existing theory or empirical formula; ρ w is the unit weight of the main river flow, calculated based on actual measurements or existing theories or empirical formulas; g is the acceleration due to gravity, which is 9.8 m / s 2 ; θ m is the average slope of the bottom bed of the main river channel; τ d is the yield stress of the mudstone fluid; h w Main river depth; h is the accumulation height of debris flow, taking the accumulation height of the debris flow dam H d for calculation; Accumulation length of debris flow barrier dam L The expression is as follows: L = L d + L u + B ; In the formula, L is the accumulation length of the debris flow dam; B is the crest width of the debris flow dam, and is determined according to the width of the debris flow gully B t for value-taking.

2. The prediction method of the geometric shape of debris flow damming a river to form a dam according to claim 1, characterized in that, The blocking river determination coefficient C r It is calculated through the flow rate of debris flow, the flow rate of the main river, the flow velocity of debris flow, the flow velocity of the main river, the total amount of debris flushed out by a single debris flow, the density of debris flow, the water depth of the main river, the width of the main river channel, the width of the debris flow gully, the yield stress of the debris flow body, the roughness coefficient of the main river bed, the outlet of the debris flow gully, and the included angle of the main river channel.

3. A prediction method for the geometric morphology of debris flow damming a river to form a dam according to claim 2, characterized in that, The blocking river judgment coefficient C r is calculated as follows: In the formula, C r is the coefficient for judging river blocking; Q df is the flow rate of debris flow; Q m is the flow rate of the main river; u df is the flow velocity of the debris flow; u m is the flow velocity of the main river; V df is the total amount of materials washed out by a debris flow; ρ df is the debris flow unit weight; g is the acceleration due to gravity; h w Depth of the main river water; B m is the width of the main river channel; B t is the width of the debris flow gully; τ d is the yield stress of the mud-rock flow; n is the roughness coefficient of the main riverbed; θ mt It is the included angle between the debris flow channel and the main river channel.

4. A prediction method for the geometric morphology of a debris flow damming a river to form a dam according to claim 1, characterized in that, When predicting the volume of the debris flow barrier dam, based on the integral idea and through regression analysis, calculate according to the maximum accumulation height of the dam crest, the minimum accumulation height of the dam crest, the downstream dam body length of the debris flow barrier dam, the upstream dam body length of the debris flow barrier dam, the width of the debris flow gully, the width of the main river channel, and the longitudinal sectional area of the debris flow barrier dam.

5. A prediction model for the geometric shape of a debris flow dam formed by blocking a river, which is used to implement a prediction method for the geometric shape of a debris flow dam formed by blocking a river as described in claim 1, characterized in that, The prediction model includes a debris flow barrier dam accumulation height calculation unit, a debris flow barrier dam accumulation length calculation unit, and a debris flow barrier dam volume calculation unit. Using the original data collected according to the debris flow properties, main river hydrodynamic conditions, boundary resistance, main river morphology, and debris flow gully morphology as input, predict the accumulation height of the debris flow barrier dam through the debris flow barrier dam accumulation height calculation unit, predict the accumulation length of the debris flow barrier dam through the debris flow barrier dam accumulation length calculation unit, and predict the volume of the debris flow barrier dam through the debris flow barrier dam volume calculation unit.

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