Analysis method, verification method and test device for critical starting flow velocity of moraine dike irregular dimension stone

Abstract

The invention provides an analysis method, a verification method and a test device for the critical starting flow velocity of moraine dike irregular dimension stones, and relates to the technical field of hydraulic engineering, and the method comprises the following steps: obtaining the sphericity coefficient and the flatness coefficient of the irregular dimension stones; calculating a correction coefficient of the irregular block stone according to the sphericity coefficient and the flatness coefficient; correcting a plurality of initial static forces borne by the irregular block stone and the initial force arm corresponding to each initial static force according to the correction coefficient so as to obtain a plurality of corrected static forces and a corrected force arm corresponding to each corrected static force; and according to the plurality of corrected static forces and the plurality of corrected force arms, constructing a critical starting flow velocity prediction model of the irregular block stone based on a moment balance principle. According to the method, geometric characteristics and stress complexity of irregular dimension stones are fully considered, the irregular dimension stones are correspondingly corrected, and an accurate prediction model is constructed in combination with a moment balance principle, so that a prediction result is closer to an actual situation, and the reliability of an analysis result can be improved.

Description

Technical Field

[0001] The present application relates to the technical field of water conservancy engineering, and in particular to an analysis method, a verification method and a test device for the critical starting velocity of irregular boulders on moraine dikes. Background Art

[0002] Moraine dikes are formed by the natural accumulation of coarse boulders of various shapes, with a low content of fine particles. They were formed after the Little Ice Age (1500 AD) and lack bonding and consolidation properties. In summer or rainy seasons, overflow will erode the fine particles in the moraine dike, gradually forming an armor layer composed of coarse boulders. Once a single coarse boulder starts moving, it may cause the armor layer structure to become unstable, triggering the complete collapse of the moraine dike, forming a large amount of floods and triggering secondary disasters, posing a great threat to downstream areas. Therefore, it is very important to study the critical conditions for the collapse of moraine dikes.

[0003] Existing studies divide the failure mechanisms of moraine dikes into two categories: one is the piping failure of the moraine dike body, and the other is the surge overflow failure caused by the rising water level of the moraine dike lake. However, both of these studies calculate the starting velocity of uniform or non-uniform sediment particles based on the assumption that the object under study is a sphere. This method is not suitable for calculating the starting velocity of coarse boulders of different sizes and poor roundness in moraine dikes. Summary of the invention

[0004] The purpose of this application is to provide an analysis method, a verification method and a test device for the critical starting flow velocity of irregular blocks on moraine dikes in response to the above-mentioned deficiencies in the prior art.

[0005] To achieve the above purpose, the technical solution adopted in the embodiment of the present application is as follows:

[0006] The embodiment of the present application provides a method for analyzing the critical starting flow velocity of irregular boulders on a moraine embankment. Irregular boulders are placed on the back slope of the moraine embankment, and the method comprises the following steps:

[0007] Obtain the sphericity coefficient and flatness coefficient of irregular blocks;

[0008] Calculate the correction factor of irregular block stone based on the sphericity coefficient and flatness coefficient;

[0009] Correcting a plurality of initial static forces on the irregular block of stone and an initial force arm corresponding to each initial static force according to a correction coefficient to obtain a plurality of corrected static forces and a corrected force arm corresponding to each corrected static force;

[0010] According to multiple corrected static forces and multiple corrected lever arms, a critical starting velocity prediction model for irregular rocks is constructed based on the moment balance principle.

[0011] Optionally, obtaining the sphericity coefficient and the flatness coefficient of the irregular block stone includes:

[0012] in, is the sphericity coefficient, is the flattening coefficient, d1, d2, d3, and h are the major axis, middle axis, minor axis, and thickness of the irregular block, respectively.

[0013] Optionally, the correction factor for calculating the irregular block stone based on the sphericity coefficient and the flatness coefficient includes:

[0014] in, is the correction factor.

[0015] Optionally, correcting a plurality of initial static forces exerted on the irregular block of stone and an initial force arm corresponding to each initial static force according to the correction coefficient to obtain a plurality of corrected static forces and a corrected force arm corresponding to each corrected static force comprises:

[0016] Among them, F D is the drag force of water flow, C D is the drag coefficient, d0 is the screening diameter of the irregular stone, u b is the critical starting velocity of irregular rocks, ρ is the density of water, L D is the force arm of the water flow drag force, R is the correction radius of the irregular stone, b is the distance between the point of action of the water drag force and the center of gravity of the irregular block, θ is the angle between the line connecting the contact point of the irregular block and the downstream block and the center of gravity of the irregular block and the vertical direction, Δ is the exposure, β is the slope of the backslope of the moraine bank;

[0017] F L is the lifting force, C L is the lifting force coefficient, L L is the arm of the lifting force, a is the distance between the point of action of the lifting force and the center of gravity of the irregular stone;

[0018] L w =Rsinθ, W is the effective gravity of the irregular stone, γ s is the bulk density of irregular stone, γ s =ρ s g,ρ s is the density of the irregular stone, g is the acceleration of gravity, γ is the specific gravity of water, L W is the moment arm of effective gravity;

[0019] L m=δR,F m is the additional mass force of the upstream and downstream rocks on the irregular rocks, α m is the area coefficient of the additional mass force, ξ is the exposure coefficient, L m is the force arm of the additional mass force, and δ is the force arm coefficient of the additional mass force.

[0020] Optionally, constructing a critical starting velocity prediction model for irregular rocks based on a plurality of corrected static forces and a plurality of corrected lever arms and a moment balance principle includes:

[0021] F D L D +F L L L +F m L m =WL w ;

[0022]

[0023] Optionally, d0=max{d3,h}.

[0024] Optionally,

[0025] Optionally,

[0026] The present application also provides a method for verifying the critical starting flow velocity of irregular boulders on moraine dikes. Irregular boulders are placed on the back slope of a moraine dike test object, and the method comprises the following steps:

[0027] Obtain the actual critical starting velocity of irregular rocks;

[0028] Obtaining geometric parameters of the irregular block of stone that has been started;

[0029] Substituting the geometric parameters into any of the above analytical methods for the critical starting velocity of irregular boulders on moraine embankments, the predicted critical starting velocity of irregular boulders is calculated;

[0030] The verification result is obtained based on the actual critical starting flow rate and the predicted critical starting flow rate.

[0031] An embodiment of the present application also provides a test device for the critical starting flow velocity of irregular rocks on a moraine embankment, which is used to implement the above-mentioned verification method for the critical starting flow velocity of irregular rocks on a moraine embankment, comprising a water trough, a slide plate placed in the water trough, an ice avalanche test object placed on the slide plate, and a moraine embankment test object placed in the water trough, irregular rocks are placed on the back slope of the moraine embankment test object, and the ice avalanche test object is driven to slide along the slide plate to the water trough to drive the liquid in the water trough to impact the moraine embankment test object and the irregular rocks.

[0032] The beneficial effects of this application include:

[0033] The present application provides an analysis method for the critical starting velocity of irregular rocks in moraine dikes. Irregular rocks are placed on the back slope of the moraine dike, and the method includes the following steps: obtaining the sphericity coefficient and the flattening coefficient of the irregular rocks; calculating the correction coefficient of the irregular rocks according to the sphericity coefficient and the flattening coefficient; correcting the multiple initial static forces and the initial force arms corresponding to each initial static force of the irregular rocks according to the correction coefficient to obtain multiple corrected static forces and the corrected force arms corresponding to each corrected static force; and constructing a prediction model for the critical starting velocity of the irregular rocks based on the principle of moment balance according to the multiple corrected static forces and the multiple corrected force arms. The method fully considers the geometric characteristics and force complexity of the irregular rocks, makes corresponding corrections to them, and then combines the principle of moment balance to construct an accurate prediction model, so that the prediction results are closer to the actual situation, improves the reliability of the analysis results, and can be applied to a variety of irregular rock shapes and complex water flow conditions, providing a reliable basis for the stability analysis and protection design of moraine dikes under complex working conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 A flow chart of a method for analyzing the critical starting velocity of irregular boulders on moraine dikes provided in an embodiment of the present application;

[0036] Figure 2 A force analysis diagram of an irregular block stone provided in an embodiment of the present application;

[0037] Figure 3 A front view of an irregular block stone provided in an embodiment of the present application;

[0038] Figure 4 A side view of an irregular block stone provided in an embodiment of the present application;

[0039] Figure 5 A flow chart of a method for verifying the critical starting velocity of irregular boulders on moraine dikes provided in an embodiment of the present application;

[0040] Figure 6 A schematic diagram of the structure of a test device for the critical starting flow velocity of irregular blocks of moraine embankment provided in an embodiment of the present application;

[0041] Figure 7It is a comparison chart of the actual critical starting flow rate and the predicted critical starting flow rate.

[0042] Icons: 10- irregular block; 21- flume; 22- slide; 23- ice avalanche test object; 24- moraine embankment test object; 25- reservoir; 26- triangular weir; 27- waste pool; 28- flow meter; 29- video recorder. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all the embodiments. The components of the embodiments of the present application described and shown in the drawings here can be arranged and designed in various different configurations.

[0044] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. It should be noted that, in the absence of conflict, the various features in the embodiments of the present application can be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0045] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0046] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the product of the application is usually placed when in use. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific position, be constructed and operated in a specific position, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0047] In addition, the terms "horizontal", "vertical" and the like do not mean that the components are required to be absolutely horizontal or suspended, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0048] In the description of this application, it should also be noted that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0049] The embodiment of the present application provides an analysis method for the critical starting velocity of irregular blocks of moraine dikes. Irregular blocks 10 are placed on the back slope of the moraine dike. By quantifying and correcting the geometric parameters of the irregular blocks 10 and combining the moment balance principle, an accurate prediction model is constructed to provide an efficient technical means for the stability analysis of moraine dikes under complex working conditions. Figure 1 As shown, the following steps are included:

[0050] S1: Obtaining the sphericity coefficient and flatness coefficient of the irregular block stone 10;

[0051] S2: Calculate the correction coefficient of the irregular block 10 based on the sphericity coefficient and the flatness coefficient;

[0052] S3: correcting the multiple initial static forces on the irregular block 10 and the initial force arm corresponding to each initial static force according to the correction coefficient to obtain multiple corrected static forces and the corrected force arm corresponding to each corrected static force;

[0053] S4: constructing a critical starting flow velocity prediction model of the irregular block 10 according to a plurality of corrected static forces and a plurality of corrected lever arms and based on the moment balance principle.

[0054] Specifically, first, the sphericity coefficient and the flattening coefficient of the irregular block 10 are calculated based on the geometric parameters of the irregular block 10. The sphericity coefficient reflects the degree to which the block is close to a sphere, while the flattening coefficient describes the flatness of the block in a certain direction. These parameters can intuitively quantify the irregularity of the block and provide basic data for subsequent analysis.

[0055] Secondly, based on these geometric parameters, the correction coefficient of the irregular block 10 is further calculated. The correction coefficient can take into account the irregular shape of the irregular block 10 and its influence on the force and stability, effectively solve the error caused by the over-idealization of the morphological assumption in the traditional model, and enable the prediction model to more accurately evaluate the critical starting flow velocity of the irregular block 10.

[0056] Then, combined with the correction coefficient, the multiple initial static forces and their corresponding initial lever arms on the irregular block 10 are adjusted to obtain the corrected static force and the corrected lever arm. The static force represents the external force on the irregular block 10 in a static state. The lever arm is the distance between the line of action of each force and the center of mass of the irregular block 10, which can determine the influence of each force on the movement of the irregular block 10. Through the correction, the comprehensive influence of the shape of the irregular block 10 and the fluid environment can be fully considered to ensure the accuracy of the force analysis.

[0057] Finally, based on multiple corrected static forces and multiple corrected lever arms, a critical starting velocity prediction model is constructed using the moment balance principle. The model determines the critical condition for the irregular block 10 to start to leave its original position by analyzing the resultant torque acting on the irregular block 10. By applying the moment balance principle in the model, the critical starting velocity required for the irregular block 10 can be accurately evaluated, thereby improving the reliability of the prediction.

[0058] In general, this method can accurately calculate the critical starting velocity of irregular rocks 10 by fully considering the geometric characteristics and force complexity of irregular rocks 10, making the prediction results closer to the actual situation, thus effectively making up for the limitations of traditional analysis based on uniform sand or ideal rocks. This method can be applied to the starting analysis of irregular rocks 10 in moraine dikes under different working conditions, such as overtopping overflow and surge, which can improve the applicability and accuracy and provide a reliable basis for the stability assessment and protection design of moraine dikes.

[0059] Optionally, obtaining the sphericity coefficient and the flatness coefficient of the irregular block stone 10 includes:

[0060] in, is the sphericity coefficient, is the flattening coefficient, such as Figures 2 to 4 As shown, d1, d2, d3, and h are the major axis, middle axis, minor axis, and thickness of the irregular block 10, respectively.

[0061] Optionally, the correction coefficient of the irregular block 10 is calculated according to the sphericity coefficient and the flatness coefficient, including:

[0062] in, is the correction factor.

[0063] Optionally, correcting a plurality of initial static forces exerted on the irregular block 10 and an initial force arm corresponding to each initial static force according to the correction coefficient to obtain a plurality of corrected static forces and a corrected force arm corresponding to each corrected static force comprises:

[0064] Among them, F D is the drag force of water flow, CD is the drag coefficient, d0 is the screening diameter of the irregular block 10, u b is the critical starting velocity of the irregular stone 10, ρ is the density of water, L D is the force arm of the water flow drag force, R is the correction radius of the irregular stone 10, b is the distance between the point of action of the water drag force and the center of gravity of the irregular block 10, θ is the angle between the line connecting the contact point between the irregular block 10 and the downstream block and the center of gravity of the irregular block 10 and the vertical direction, Δ is the exposure, β is the slope of the backslope of the moraine bank;

[0065] F L is the lifting force, C L is the lifting force coefficient, L L is the arm of the lifting force, and a is the distance between the point of action of the lifting force and the center of gravity of the irregular block 10;

[0066] L w =Rsinθ, W is the effective gravity of the irregular block 10, γ s is the bulk density of the irregular block 10, γ s =ρ s g,ρ s is the density of the irregular block 10, g is the acceleration of gravity, γ is the specific gravity of water, L W is the moment arm of effective gravity;

[0067] L m =δR,F m is the additional mass force of the upstream and downstream rocks on the irregular rock 10, α m is the area coefficient of the additional mass force, ξ is the exposure coefficient, L m is the force arm of the additional mass force, and δ is the force arm coefficient of the additional mass force.

[0068] Specifically, if Figure 2 As shown, the multiple modified static forces include water flow drag force, lifting force, effective gravity, upstream rocks and additional mass force. The calculation formulas of the multiple modified static forces and the modified lever arms corresponding to each modified static force are as above. D and the lifting force F L The concepts of are proposed by "River Sediment Engineering". This application modifies them through correction coefficients to make them suitable for the force analysis of irregular blocks 10. It should be noted that in the correction process, the density of water ρ and the bulk density of irregular blocks 10 γ s , the bulk density γ of water is the measured value of the required research area.

[0069] It should be understood that since multiple irregular blocks 10 are naturally deposited on the back slope of the moraine embankment, each irregular block 10 will be exposed and concealed. Therefore, the embodiment of the present application adopts the exposure degree Δ proposed by the "Research on Exposure Degree and Equivalent Particle Size of Sediment Particles". The exposure degree Δ is the vertical distance between the lowest point of the irregular block 10 under study and the contact point with the downstream block.

[0070] In addition, the embodiment of the present application defines the ratio of the exposure degree to the modified radius R of the irregular block 10 as the relative exposure degree Δ', that is, The relative exposure Δ' can not only reflect the position of each irregular rock 10 on the backslope of the moraine embankment, but also reflect the position of the upstream rock or downstream rock adjacent to it on the backslope of the moraine embankment. The position relationship between adjacent rocks can reflect the interaction relationship between rocks, and further reflect the position characteristics of the irregular rock 10 on the backslope of the moraine embankment, that is, it is necessary to consider the additional mass force F of the upstream rock and the downstream rock on the irregular rock 10. m .

[0071] Among them, it is used to calculate the additional mass force F m The value of the exposure coefficient ξ in the formula is related to the relative exposure Δ'. The size of the relative exposure Δ' will affect the value of the exposure coefficient ξ. Generally, the value range of the exposure coefficient ξ is 0 to 1. The value range of the arm coefficient δ of the additional mass force is generally 0 to 1, which is used to adjust the contribution of the additional mass force in the moment calculation.

[0072] Optionally, constructing a critical starting velocity prediction model of the irregular block 10 based on a plurality of corrected static forces and a plurality of corrected lever arms and the moment balance principle includes:

[0073] F D L D +F L L L +F m L m =WL w ;

[0074]

[0075] Optionally, d0=max{d3,h}.

[0076] Optionally, the drag coefficient C D And the lifting force coefficient C L Usually take the empirical value, drag force coefficient C D Usually 0.78 is taken.

[0077] Optionally,

[0078] The present application also provides a method for verifying the critical starting flow velocity of irregular blocks of moraine dikes. Irregular blocks 10 are placed on the back slope of a moraine dike test object 24. Figure 5 As shown, the following steps are included:

[0079] S100: obtaining the actual critical starting flow velocity of the irregular stone 10;

[0080] S200: Acquiring geometric parameters of the irregular block 10 that has been started;

[0081] S300: Substitute the geometric parameters into any of the above-mentioned analysis methods for the critical starting flow velocity of irregular boulders on moraine dikes to calculate the predicted critical starting flow velocity of the irregular boulders 10;

[0082] S400: Obtaining a verification result according to the actual critical starting flow rate and the predicted critical starting flow rate.

[0083] Specifically, firstly, under test conditions, the irregular block 10 is placed at a specific position of the backslope of the moraine embankment, and the actual critical starting velocity of the irregular block 10 is obtained by testing various surges stimulated by different ice avalanche test objects 23. Among them, the test conditions need to ensure that the characteristic parameters of the surge (such as amplitude, wavelength, wave speed, energy, etc.), the backslope slope of the moraine embankment test object 24, and the surrounding environment match the actual geological conditions, so as to be as close to the actual working conditions as possible.

[0084] Secondly, for the irregular block 10 that has been started in the test, its geometric parameters are measured by three-dimensional scanning or traditional measurement tools, including the major axis, middle axis, minor axis and thickness, etc. These parameters can reflect the shape characteristics of the irregular block 10 and its stress state in the stacking environment, and are important input variables for subsequent analysis.

[0085] Then, the geometric parameters measured in the experiment were brought into the critical starting velocity analysis method of irregular blocks on moraine embankments. Based on the principle of moment balance, the effects of water drag, lifting force, effective gravity and additional mass force were corrected by correction coefficients, and the predicted critical starting velocity of the irregular blocks 10 was calculated in combination with the correction lever arm.

[0086] Finally, the actual critical starting flow rate obtained from the test was compared with the predicted critical starting flow rate calculated theoretically, the error between the two was analyzed, and the accuracy and applicability of the prediction model were evaluated.

[0087] In general, this verification method combines theory with experiment, is suitable for the verification of the critical starting flow velocity of irregular blocks 10 under various working conditions, and can improve the reliability and practical guidance value of theoretical analysis results by calibrating the prediction model through experimental data, thereby providing a theoretical basis for the back slope design of moraine embankments and the stability evaluation of irregular blocks 10, and effectively improving the disaster prevention and mitigation capabilities and design reliability of moraine embankments.

[0088] The present application also provides a test device for the critical starting flow velocity of irregular blocks of moraine embankment, which is used to implement the above-mentioned verification method for the critical starting flow velocity of irregular blocks of moraine embankment, such as Figure 6 As shown, it includes a water trough 21, a slide plate 22 placed in the water trough 21, an ice avalanche test object 23 placed on the slide plate 22, and a moraine dam test object 24 placed in the water trough 21. Irregular blocks of stone 10 are placed on the back slope of the moraine dam test object 24. The ice avalanche test object 23 is driven to slide along the slide plate 22 to the water trough 21 to drive the liquid in the water trough 21 to impact the moraine dam test object 24 and the irregular blocks of stone 10.

[0089] Specifically, the test device uses a glass water tank 21 with a length of 10m, a width of 0.28m, and a height of 0.55m, which is divided into a slope end, a front end section of the slope, and a rear end section of the slope. Among them, the longitudinal slope of the rear end section of the slope is 1°, and the dimensions are 6.3m long, 0.28m wide, and 0.55m high. The two sides of the glass water tank 21 are transparent plexiglass, and a ruler is pasted on the outside of the glass. The test phenomenon in the glass water tank 21 can be directly observed through the transparent plexiglass, and it is convenient for the high-speed camera to record the wave height and the changes in the reservoir water level during the test. Then, a moraine embankment test object 24 is arranged at the rear end section of the slope of the glass water tank 21 to simulate the shape of moraine embankments in nature. The moraine embankment test object 24 is located 1.5m downstream of the foot of the slope. The moraine embankment test object 24, the glass water tank 21 and the slope are surrounded to form a reservoir capacity of 0.18m 3 A reservoir 25 and a triangular weir 26 are arranged at the upstream end of the glass water tank 21 to precisely control the flow and velocity parameters of the water flow, thereby realizing the impact test under different surge conditions. A waste pool 27 is arranged at the downstream end of the glass water tank 21 to collect irregular blocks 10, realize multiple recycling of materials, and ensure the economic efficiency and sustainability of the test.

[0090] It should be noted that the Don Muang Lake moraine embankment is 75m wide and 40m high, with an aspect ratio of 1.875. The aspect ratio of moraine embankment test object 24 is set to 1.8 with reference to the Don Muang Lake moraine embankment. Although different moraine dams may have different aspect ratios, due to the limitations of the glass water tank 21, a larger aspect ratio cannot be simulated in the test. The dam body of moraine embankment test object 24 adopts trapezoidal accumulation, with a designed dam height of 0.3m, a dam bottom length of 1.2m, and a dam top length of 0.1m.

[0091] It should also be noted that this test is to study the start of the irregular block 10 in the armor layer, so it is necessary to avoid the collapse of the dam body itself as much as possible, so the moraine embankment test object 24 needs to have no seepage inside and good stability. Therefore, in order to ensure that there is no seepage inside the moraine embankment test object 24, a no-hidden-ice design can be adopted, and a 2-cm thick waterproof layer with 10% cement content can be laid on the outermost layer to play a waterproof role.

[0092] In addition, since the irregular blocks 10 constituting the armor layer of the moraine embankment have the characteristics of poor roundness, high surface roughness, and angular and sub-angular shapes, the irregular blocks 10 selected for the test must also have the above characteristics. After the base and waterproof layer are laid, the density of 2.8g / cm 3 The irregular blocks 10 are mixed with fine particles of the same particle size composition as the base, laid on the back slope of the moraine bank test object 24 and compacted.

[0093] In order to simulate ice avalanche conditions of different intensities, the test can use ice avalanche test objects 23 of various sizes, as shown in Table 1, to generate a series of surges to impact the moraine bank test object 24 and the irregular block 10, so as to obtain the actual critical starting flow rate of the irregular block 10. It should be noted that in order to ensure that the ice avalanche test object 23 enters the water at the same position in each test, the embodiment of the present application uses a 120 cm long rectangular thin wooden board as the slide 22, and fixes one end of the slide 22 to the foot of the slope section of the glass water tank 21, and controls the angle between the slide 22 and the water surface and the distance between the ice avalanche test object 23 and the water surface to stimulate different initial surge heights.

[0094] Table 1. Ice avalanche test specimen dimensions

[0095]

[0096] In order to collect test data, the embodiment of the present application uses two flow rate measuring instruments 28 (such as UltraLab SVR surface flow meters), three video recorders 29 (such as high-speed cameras) and a set of high-precision micro-force sensors. The two UltraLabSVR surface flow meters are respectively placed at the front end section and slope section of the moraine embankment test object 24, and are used to measure the flow velocity of the water flow in front of the dam and the flow velocity of the water flow on the back slope; the three cameras are placed on the side of the water tank 21 of the front end section of the moraine embankment test object 24, the side of the back slope and the top, and are used to record the wave morphology in front of the moraine embankment test object 24 and the test phenomenon on the back slope; the receiver of the high-precision micro-force sensor is placed at the bottom of the water tank 21 of the front end section of the moraine embankment test object 24, and is used to record the height of the wave.

[0097] Specific test process: After the test starts, the water reservoir 25 and the triangular weir 26 work together to form a 2×10 -5 m3 / s was used to inject water into the moraine bank test object 24. The water level continued to rise during the injection process. When the freeboard was 1 cm, the flow rate was reduced to 1×10 -5 m 3 / s. When the reservoir water level exceeds the dam top, overflow occurs. The backwater slope carries away the fine particles on the surface under the action of the water flow, causing the armor layer irregular blocks 10 to accumulate naturally. When the armor layer accumulation is relatively stable, stop injecting water into the reservoir 25, and a relatively stable armor layer is formed. Then, the actual critical starting flow rate of the irregular blocks 10 under ice avalanche conditions of different intensities is obtained through the above-mentioned data acquisition equipment, and the irregular blocks 10 that have started are removed in time.

[0098] Then, the geometric parameters of the irregular block 10 that starts are measured, and the geometric parameters are brought into the above-mentioned analysis method, so that the predicted critical starting flow rate can be calculated. In the embodiment of the present application, the values ​​of each parameter are as follows: C D =0.78, C L =0.1,γ s =2.8g / m 3 ,γ=1g / m 3 , g = 9.8 m / s 2 , θ=40°, β=24.18°, ξ=0.7, δ=0.87, α m =π / 6.

[0099] As shown in Table 2 and Figure 7 As shown, the predicted critical starting velocity of the irregular rock 10 obtained by the above analysis method is basically consistent with the actual critical starting velocity of the irregular rock 10 obtained by the test. However, due to the influence of the shape and position of the irregular rock 10 itself, the starting has a certain randomness, so there will be different sizes of irregular rocks 10 starting at the same measured flow rate, but the deviation between different dynamic flow rates and the prediction model is not large. Therefore, the above analysis method is highly applicable and practical, and can solve the starting mechanism of the irregular rock 10 in the armor layer of the moraine embankment overflow port, and is applicable to the calculation of the starting of irregular rocks 10 under conditions such as overtopping overflow and surge.

[0100] Table 2 Starting flow rate calculation table

[0101]

[0102] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A method for analyzing the critical starting velocity of irregular rocks on moraine embankments, characterized in that: Irregular blocks (10) are placed on the back slope of the moraine embankment, comprising the following steps: Obtaining the sphericity coefficient and the flatness coefficient of the irregular block stone (10); Calculating a correction coefficient of the irregular block stone (10) according to the sphericity coefficient and the flatness coefficient; Correcting a plurality of initial static forces exerted on the irregular block of stone (10) and an initial force arm corresponding to each of the initial static forces according to the correction coefficient to obtain a plurality of corrected static forces and a corrected force arm corresponding to each of the corrected static forces; According to the plurality of modified static forces and the plurality of modified force arms, and based on the moment balance principle, a critical starting flow velocity prediction model of the irregular block (10) is constructed.

2. The method according to claim 1, characterized in that The step of obtaining the sphericity coefficient and the flatness coefficient of the irregular block stone (10) comprises: in, is the sphericity coefficient, is the flattening coefficient, d1, d2, d3, and h are respectively the major axis, the middle axis, the minor axis, and the thickness of the irregular block (10).

3. The method according to claim 2, characterized in that The correction coefficient of the irregular block (10) calculated according to the sphericity coefficient and the flatness coefficient comprises: in, is the correction factor.

4. The method according to claim 3, characterized in that The method of correcting the plurality of initial static forces exerted on the irregular block (10) and the initial force arm corresponding to each of the initial static forces according to the correction coefficient to obtain a plurality of corrected static forces and the corrected force arm corresponding to each of the corrected static forces comprises: Among them, F D is the drag force of water flow, C D is the drag coefficient, d0 is the screening diameter of the irregular block (10), u b is the critical starting velocity of the irregular block (10), ρ is the density of water, L D is the force arm of the water flow drag force, R is the modified radius of the irregular block (10), b is the distance between the point of action of the water flow drag force and the center of gravity of the irregular block (10), θ is the angle between the vertical direction and the line connecting the contact point between the irregular block (10) and the downstream block and the center of gravity of the irregular block (10), Δ is the exposure, β is the slope of the backslope of the moraine bank; F L is the lifting force, C L is the lifting force coefficient, L L is the force arm of the lifting force, and a is the distance between the point of action of the lifting force and the center of gravity of the irregular block (10); L w =Rsinθ, W is the effective gravity of the irregular block (10), γ s is the bulk density of the irregular block (10), γ s =ρ s g,ρ s is the density of the irregular block (10), g is the acceleration of gravity, γ is the specific gravity of the water, L W is the moment arm of the effective gravity; L m =δR,F m is the additional mass force of the upstream stone and the downstream stone on the irregular stone (10), α m is the area coefficient of the additional mass force, ξ is the exposure coefficient, L m is the force arm of the additional mass force, and δ is the force arm coefficient of the additional mass force.

5. The method according to claim 4, characterized in that The critical starting flow velocity prediction model of the irregular block (10) is constructed based on the plurality of the modified static forces and the plurality of the modified lever arms and the moment balance principle, and includes: F D L D +F L L L +F m L m =WL w ; 6. The method according to claim 4 or 5, characterized in that: d0=max{d3,h}.

7. The method according to claim 4 or 5, characterized in that:

8. The method according to claim 4 or 5, characterized in that:

9. A method for verifying the critical starting velocity of irregular boulders on moraine dikes, characterized in that: Irregular blocks (10) are placed on the back slope of the moraine embankment test object (24), including the following steps: Obtaining an actual critical starting flow velocity of the irregular stone (10); Acquiring geometric parameters of the irregular block (10) that has been started; Substituting the geometric parameters into the analysis method of the critical starting flow velocity of the irregular boulders of moraine embankment as claimed in any one of claims 1 to 8, and calculating the predicted critical starting flow velocity of the irregular boulders (10); A verification result is obtained according to the actual critical starting flow rate and the predicted critical starting flow rate.

10. A test device for critical starting flow velocity of irregular blocks on moraine embankments, characterized in that: A verification method for realizing the critical starting flow velocity of irregular blocks of moraine dyke as claimed in claim 9, comprising a water trough (21), a slide plate (22) placed in the water trough (21), an ice avalanche test object (23) placed on the slide plate (22), and a moraine dyke test object (24) placed in the water trough (21), wherein irregular blocks (10) are placed on the back slope of the moraine dyke test object (24), and the ice avalanche test object (23) is driven to slide along the slide plate (22) to the water trough (21) to drive the liquid in the water trough (21) to impact the moraine dyke test object (24) and the irregular blocks (10).

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