Method and system for calculating reflectivity of railway gravel slope protection covered by accumulated snow

Abstract

The invention discloses a reflectivity calculation method and system for railway gravel slope protection covered by accumulated snow, and particularly relates to the field of solar radiation reflectivity calculation. Comprising the following steps: S1, acquiring data of length, width, height, gradient ratio and gravel particle size of a gravel slope protection; s2, estimating an accumulated snow coverage rate; s3, calculating the direct reflectivity; s4, calculating the internal refractive index of the gravel; s5, the influence of the inclination angle of the gravel slope protection on the reflectivity is corrected; and S6, combining the steps S2-S4 to obtain the reflectivity of the gravel slope protection after snow accumulation. By adopting the technical scheme, the problem that the short-wave reflectivity of the broken stone slope protection cannot be obtained after snow accumulation due to the lack of a calculation method for the short-wave reflectivity of the broken stone slope protection under the snow coverage condition is solved, the calculation method is simple and clear, and the calculation cost is low.

Description

Technical Field

[0001] The present invention relates to the field of solar radiation reflectivity calculation, and particularly relates to a method and system for calculating the reflectivity of a railway ballast slope under snow cover. Background Art

[0002] In railway engineering in permafrost regions, ballast slopes are widely used to protect the thermal stability of slopes. The ballast is piled up with large voids, which mainly has three effects on railway engineering: (1) When the railway passes by, the voids provide space for the relative movement of the ballast, thereby releasing the kinetic energy generated by vibration, keeping the overall geometric shape of the slope change small, and making the thermal stability boundary stable. (2) The voids provide a channel for external air to flow in and the air inside the ballast slope to flow out, realizing the convective heat exchange. In summer, the air density gradient inside the ballast slope is stable, and it is difficult for external heat to enter. The cold air is restricted at the bottom, slowing down the warming of the slope surface. In winter, the unstable air density gradient is generated by the temperature difference between the top and the bottom, forcing the internal air to convect and circulate under the drive of gravity, and transporting the heat flow upward, playing a role in cooling the slope surface. (3) The optical form of the voids is generally an irregular black hole, which absorbs solar radiation, reduces the short-wave reflectivity of the ballast slope, and promotes the warming of the ballast slope. It can be seen that the ballast slope has both advantages and disadvantages in maintaining thermal stability. Only when the energy obtained by satisfying (1)+(2)-(3) of the above three influencing conditions is negative, the ballast slope can play a role in cooling the slope surface, thereby protecting the thermal stability of the slope surface.

[0003] However, in winter or severe cold climate conditions, snow often fills the voids of the ballast slope and further covers the slope surface. The snow cover not only changes the short-wave reflectivity of the slope surface, but also may affect the overall energy balance of the slope through complex optical processes such as multiple refractions and reflections inside. These changes will directly affect the freeze-thaw environment and stability of the slope surface. After snow accumulation, the voids of the ballast slope are filled, weakening the cooling effect on the slope surface in (1) and (2) of the above influences, but the short-wave reflectivity in (3) becomes larger and the solar radiation absorption decreases, making it difficult to determine whether the energy calculation of (1)+(2)-(3) is negative. It is necessary to obtain the short-wave reflectivity after snow accumulation for calculation. At present, there is a lack of a calculation method for the short-wave reflectivity of the ballast slope under snow cover, and the value of the short-wave reflectivity of the ballast slope after snow accumulation cannot be obtained.

[0004] In view of this, in order to realize energy balance analysis and quantify the influence of the change in snow cover rate on the short-wave reflectivity of the slope, for the process of snow gradually covering the ballast slope, a method for calculating the reflectivity of a railway ballast slope under snow cover is established to quantitatively describe the change in the short-wave reflectivity of the slope during the process of snow gradually filling the voids until complete coverage. Provide reflectivity parameter input for the railway engineering design in permafrost regions, and assist in the thermal analysis and energy balance calculation of the slope. Summary of the Invention

[0005] The present invention aims to provide a method and system for calculating the reflectivity of a railway ballast slope under snow cover, which solves the problem of lacking a calculation method for the short-wave reflectivity of the ballast slope without snow cover, and thus the short-wave reflectivity of the ballast slope after snow cannot be obtained.

[0006] To achieve the above object, a technical solution provided by the present invention is as follows: A method for calculating the reflectivity of a railway ballast slope under snow cover, comprising the following steps:

[0007] S1. Obtain the data of the length, width, height, slope ratio, and ballast particle size of the ballast slope;

[0008] S2. Estimate the snow cover rate;

[0009] S3. Calculate the direct reflectivity;

[0010] S4. Calculate the refractive index inside the ballast;

[0011] S5. Correct the influence of the inclination angle of the ballast slope on the reflectivity;

[0012] S6. Combine steps S2 - S4 to obtain the reflectivity of the ballast slope after snow.

[0013] Further, the specific method of step S3 is as follows:

[0014] For the case where the snow completely covers the surface of the slope:

[0015] f 积雪 = 1;

[0016] For the case where the snow gradually fills the voids:

[0017]

[0018] where h 积雪 is the snow thickness, P is the porosity of the ballast slope, and H 碎石 is the total thickness of the ballast layer;

[0019] Direct reflection refers to the primary reflection of light at the snow - air surface, which is determined by the snow cover rate f 积雪 , and is a weighted average of the reflectivities of snow and ballast. The calculation formula is:

[0020] α 直接 = f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 ;

[0021] where f 积雪is the snow cover rate, defined as the ratio of the snow-covered area to the total area; α 积雪 is the reflectivity of the snow surface, α 碎石 is the reflectivity of the gravel surface.

[0022] Furthermore, the specific method of step S4 is as follows: Internal reflection occurs after the snow fills the voids. After the light enters the snow-void cavity-gravel interface in the voids, it undergoes multiple refractions and scatterings. The effective reflectivity α 内部 is used for calculation:

[0023] α 内部 = (1 - f 积雪 ) · T 积雪 · α 空腔 ;

[0024] where T 积雪 is the transmittance of the snow, representing the ability of light to penetrate the snow surface; the transmittance of the snow is determined by the reflectivity, absorptivity, and scattering rate:

[0025] T 积雪 = 1 - α 积雪 - A 积雪 ;

[0026] In the formula, A 积雪 is the absorptivity of the snow, depending on the cleanliness of the snow;

[0027] α 空腔 is the internal effective reflectivity of light in the voids;

[0028] The reflectivity inside the voids is determined by the behavior of light between the air, gravel, and snow interfaces; based on the Fresnel equation for the interface refractive index, it can be expressed as:

[0029]

[0030] where n1 and n2 are the refractive indices of the media on both sides of the interface respectively;

[0031] The reflectivity R x described by the interface represents the reflection contribution on a specific interface,

[0032] α 空腔 = R 空气-碎石 + (1 - R 空气-碎石 ) · R 碎石-空气 ;

[0033] where,

[0034] n 空气 = 1.0, n 碎石 is the refractive index of the gravel, taken as 1.6.

[0035] Further, the specific method of step S5 is as follows: The inclination angle θ of the crushed stone slope protection 坡 will change the angle of the incident light, thereby affecting the actual reflectivity. After considering the inclination angle, the total reflectivity is corrected to:

[0036]

[0037] where θ i is the incident angle and is related to the slope inclination angle; α 总 (θ i ) is the angular dependence of the total reflectivity;

[0038] In actual calculation, assuming that the angles of light are evenly distributed, it is simplified to:

[0039]

[0040] Another technical solution provided by the present invention is as follows: A reflectivity calculation system for a railway crushed stone slope protection under snow cover, comprising:

[0041] A collection module, which is used to collect data on the length, width, height, slope ratio, and crushed stone particle size of the crushed stone slope protection;

[0042] A snow cover rate estimation module, which estimates through the data collected by the collection module;

[0043] A first calculation module, which is used to calculate the direct reflectivity and the internal refractive index through the snow cover rate and the data collected by the collection module;

[0044] A correction module, which is used to correct the influence of the inclination angle of the crushed stone slope protection on the change of the incident light angle;

[0045] A second calculation module, which calculates the total reflectivity through the values obtained by the first calculation module and the correction module.

[0046] Further, the direct reflectivity is obtained by weighted calculation of the snow cover rate and the surface reflectivities of two materials, and the internal refractive index is calculated using a combination of the snow transmittance and the cavity reflectivity.

[0047] Further, the calculation method of the direct reflectivity is as follows:

[0048] For the case where the snow completely covers the slope surface:

[0049] f 积雪 = 1;

[0050] For the case where the snow gradually fills the voids:

[0051]

[0052] Among them, h 积雪 is the snow depth, P is the porosity of the crushed stone slope protection, and H 碎石 is the total thickness of the crushed stone layer;

[0053] Direct reflection refers to the initial reflection of light at the snow - air surface, which is determined by the snow cover rate f 积雪 and is the weighted average of the reflectivities of snow and crushed stone. The calculation formula is:

[0054] α 直接 = f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 ;

[0055] Among them, f 积雪 is the snow cover rate, defined as the ratio of the snow - covered area to the total area; α 积雪 is the reflectivity of the snow surface, and α 碎石 is the reflectivity of the crushed stone surface.

[0056] Furthermore, the calculation method of the internal refractive index is as follows: Internal reflection occurs after the snow fills the voids. When light enters the snow - air cavity - crushed stone interface in the voids, it undergoes multiple refractions and scatterings, and is calculated using the effective reflectivity α 内部 :

[0057] α 内部 =(1 - f 积雪 )·T 积雪 ·α 空腔 ;

[0058] Among them, T 积雪 is the transmittance of the snow, indicating the ability of light to penetrate the snow surface; the transmittance of the snow is determined by the reflectivity, absorptivity, and scattering rate:

[0059] T 积雪 = 1 - α 积雪 - A 积雪 ;

[0060] In the formula, A 积雪 is the absorptivity of the snow, which depends on the cleanliness of the snow;

[0061] α 空腔 is the internal effective reflectivity of light in the voids;

[0062] The reflectivity inside the voids is determined by the behavior of light between the air, crushed stone, and snow interfaces; based on the Fresnel equation of the interface refractive index, it can be expressed as:

[0063]

[0064] Among them, n1 and n2 are the refractive indices of the media on both sides of the interface respectively;

[0065] The reflectivity R x The interface describes the reflection contribution on a specific interface.

[0066] α 空腔 = R 空气-碎石 +(1 - R 空气-碎石 )·R 碎石-空气 ;

[0067] Among them,

[0068] n 空气 = 1.0, n 碎石 is the refractive index of the crushed stone, taken as 1.6.

[0069] Furthermore, the correction method adopted by the correction module is as follows: The inclination angle θ of the crushed stone slope protection 坡 will change the angle of the incident light, thereby affecting the actual reflectivity. After considering the inclination angle, the total reflectivity is corrected to:

[0070]

[0071] Among them, θ i is the incident angle, related to the slope inclination angle; α 总 (θ i ) is the angular dependence of the total reflectivity;

[0072] During actual calculation, assuming a uniform distribution of the light angle, it is simplified to:

[0073]

[0074] Compared with the prior art, the beneficial effects of this solution:

[0075] This solution provides a method for calculating the reflectivity of a railway crushed stone slope protection under snow cover, solving the problem of the lack of a calculation method for the short-wave reflectivity of the crushed stone slope protection without snow cover, and thus being unable to obtain the short-wave reflectivity of the crushed stone slope protection after snow. At the same time, this solution is easy to understand, has clear logic, is simplified and easy to calculate, and has low calculation costs; all the required calculated values can be obtained by mature measurement techniques, without the need to obtain unknown values through theoretical models; and through step-by-step calculation, it can cope with various actual conditions. Even when a step cannot be calculated, an empirical value can be obtained for actual use. Description of the Drawings

[0076] Figure 1 is a flowchart of a method for calculating the reflectivity of a railway crushed stone slope protection under snow cover according to the present invention;

[0077] Figure 2 is a schematic diagram of direct reflection in Embodiment 1;

[0078] Figure 3 is a schematic diagram of internal refraction in Embodiment 1;

[0079] Figure 4 is a schematic diagram of the inclination angle of the riprap slope in Embodiment 1. Specific Embodiments

[0080] The present invention will be further described in detail below through specific embodiments:

[0081] Relevant situation description: The particle size of the riprap determines the roughness of the slope surface, and the roughness in turn affects the reflection behavior of light.

[0082] Small particle size: The particle surface is close to smooth, and light is more inclined to specular reflection with a higher reflectivity.

[0083] Large particle size: The particle surface is rough, and light is more inclined to diffuse reflection or be absorbed by voids, resulting in a reduced reflectivity.

[0084] When other conditions of a railway engineering section are similar, and only the particle size of the riprap slope changes, the reflectivity of riprap slopes with different particle sizes in the same section can be obtained by correcting the particle size of the riprap. If the influence of roughness on reflectivity is small (such as the particle size distribution of the riprap is relatively uniform and the inclination angle is not large), the influence of roughness can be represented by an overall correction coefficient. This method implies that the roughness coefficient has a consistent correction effect on all reflection components (snow reflection, riprap reflection, multiple reflections in voids, etc.).

[0085] Correction formula (roughness correction):

[0086] α′ 总 = α 总 ·C r ;

[0087] C r represents the roughness coefficient, usually with a value range of 0 - 1. The rougher the surface, the smaller the value.

[0088] Source of the roughness coefficient:

[0089] 1. Obtained by fitting through actual measurement of reflectivity under different roughness conditions.

[0090] 2. For a specific scenario (such as the commonly used materials for riprap slopes), typical values from existing research can be used. For example: for a smooth surface C r = 1, for medium roughness: C r = 0.8, for highly rough: C r = 0.5.

[0091] Basic definitions and parameters:

[0092] (1) Optical properties of crushed stone slope protection and snow cover

[0093]

[0094] (2) Geometric properties of crushed stone slope protection

[0095]

[0096] Example 1

[0097] A method for calculating the reflectivity of a railway crushed stone slope protection under snow cover, comprising the following steps:

[0098] S1. Obtain the data of the length, width, height, slope ratio and crushed stone particle size of the crushed stone slope protection.

[0099] S2. Estimate the snow cover rate, which is calculated by various methods such as porosity, snow depth, and slope protection geometric structure. The specific method is as follows:

[0100] Snow cover rate (S): It refers to the area ratio of snow cover per unit area. It can be estimated according to the distribution of snow cover and different physical properties. The snow cover rate can be expressed as:

[0101]

[0102] 1. The mass (M) of the snow cover can be calculated by the volume and density of the snow cover:

[0103] M = ρ·V

[0104] 2. Adjust the coverage rate according to the geometric structure of the snow cover layer

[0105] The geometric structure of the slope protection will affect the distribution of the snow cover. Especially when the slope is relatively large, the snow cover may slide down or be compacted along the slope surface. Therefore, geometric structure adjustment is required. Set the influence factor f slope (such as slope angle, slope surface flatness, etc.), and the following formula can be used to correct the snow cover area:

[0106] S adj = S·f slope

[0107] where S is the uncorrected snow cover rate, and f slope is adjusted according to the specific situation of the slope protection. For example, a larger slope will result in a decrease in the snow cover rate.

[0108] 3. Consider the change of snow depth

[0109] The snow depth also affects the final coverage rate. Especially in the case of uneven snow accumulation, areas with relatively thin snow depth may not fully cover the ground. At this time, the overall snow coverage rate can be adjusted by the average snow depth:

[0110]

[0111] Where:

[0112] H avg : The actual average snow depth;

[0113] H max : The maximum snow depth, usually in flat areas or places with less shelter.

[0114] Assume:

[0115] The snow depth H = 0.5m;

[0116] The porosity is 30%, thus calculating that the density of the snow is approximately 300 kg / m;

[0117] The slope protection influence factor f slope = 0.85;

[0118] The average snow depth H avg = 0.4m, the maximum snow depth H max = 0.5m;

[0119] The preliminary calculation shows that the snow coverage rate is 0.6 (60%).

[0120] Then, the final snow coverage rate is:

[0121]

[0122] That is, the final snow coverage rate is 40.8%.

[0123] At the same time, the porosity can be obtained from the particle size and stacking method of the crushed stone for slope protection. According to the grading theory, the relationship between the porosity and the particle size distribution can be expressed by the following formula:

[0124]

[0125] Where ε is the porosity;

[0126] V s is the particle volume of the crushed stone;

[0127] V t is the stacking volume of the crushed stone.

[0128] S3. Calculate the direct reflectance. The direct reflectance is obtained by weighting the coverage rate and the surface reflectance of the two materials. For example Figure 2As shown below, the specific method is as follows:

[0129] For the case where the snow cover completely covers the slope protection surface:

[0130] f 积雪 = 1;

[0131] For the case where the snow gradually fills the voids:

[0132]

[0133] where h 积雪 is the snow depth, P is the porosity of the crushed stone slope protection, and H 碎石 is the total thickness of the crushed stone layer;

[0134] Direct reflection refers to the initial reflection of light at the snow - air surface, and its contribution is determined by the snow cover rate f 积雪 , which is the weighted average of the reflectivities of snow and crushed stone. The reflectivities of the snow surface and the crushed stone surface can be obtained by querying or directly measured using professional measuring instruments such as total radiation meters, four - component instruments, and ultraviolet spectrometers. The calculation formula is:

[0135] α 直接 = f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 ;

[0136] where f 积雪 is the snow cover rate, defined as the ratio of the snow - covered area to the total area; α 积雪 is the reflectivity of the snow surface (typical value 0.8), and α 碎石 is the reflectivity of the crushed stone surface (typical value 0.2).

[0137] S4. Calculate the refractive index inside the crushed stone. The refractive index inside the crushed stone is calculated using a combination of the snow transmittance and the cavity reflectivity. As Figure 3 shown below, the specific method is as follows: Internal reflection occurs after the snow fills the voids. After the light enters the snow - void cavity - crushed stone interface in the voids, it undergoes multiple refractions and scatterings, and the effective reflectivity α 内部 is used for calculation:

[0138] α 内部 =(1 - f 积雪 )·T 积雪 ·α 空腔 ;

[0139] where T 积雪 is the transmittance of the snow, indicating the ability of light to penetrate the snow surface. The transmittance of the snow is determined by the reflectivity, absorptivity, and scattering rate:

[0140] T 积雪 = 1 - α 积雪 -A 积雪 ;

[0141] In the formula, A 积雪 is the absorption rate of snow cover, which depends on the cleanliness of the snow, and the typical value is 0.05 - 0.1.

[0142] α 空腔 is the internal effective reflectivity of light in the voids.

[0143] The reflectivity inside the voids is determined by the behavior of light between the interfaces of air, gravel, and snow cover; based on the Fresnel equation for the interface refractive index, it can be expressed as:

[0144]

[0145] where n1 and n2 are the refractive indices of the media on both sides of the interface. For example, the media on both sides of the interface of the gravel pile are gravel and air; the media on both sides of the interface of the gravel - snow pile are gravel and snow cover; if the snow cover does not cover all the voids, there are three cases: snow cover and air, snow cover and gravel, and gravel and air.

[0146] The reflectivity R x described by the interface represents the reflection contribution on a specific interface.

[0147] α 空腔 = R 空气碎石 +(1 - R 空气碎石 )·R 碎石空气 ;

[0148] where

[0149] n 空气 = 1.0 (refractive index of air), n 碎石 is the refractive index of gravel, taken as 1.6.

[0150] S5. Modify the influence of the inclination angle of the gravel slope protection on the reflectivity. Among them, the inclination angle of the gravel slope protection and the total thickness of the gravel layer can be calculated from design values such as the design height and thickness, or directly measured on - site. As Figure 4 shown, the specific method is as follows: The inclination angle θ 坡 of the gravel slope protection will change the incident light angle, thus affecting the actual reflectivity. After considering the inclination angle, the total reflectivity is corrected to:

[0151]

[0152] where θ i is the incident angle, which is related to the slope inclination angle; α 总 (θi ) is the angular dependence of the total reflectance;

[0153] In actual calculation, if it is assumed that the light is uniformly distributed in terms of angle, it can be simplified to:

[0154]

[0155] S6. Combine the reflectance of the crushed stone slope protection after snow accumulation obtained in steps S2 - S4. The formula is as follows:

[0156] α 总 = f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 +(1 - f 积雪 )·T 积雪 ·α 空腔 ;

[0157] All the above values can be obtained through measurement or calculation.

[0158] The formula after considering the tilt angle correction is:

[0159] α 总 =(f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 +(1 - f 积雪 )·T 积雪 ·α 空腔 )·cosθ 坡 .

[0160] Example 2

[0161] A reflectance calculation system for a railway crushed stone slope protection under snow cover, including:

[0162] A collection module, which is used to collect data on the length, width, height, slope ratio, and crushed stone particle size of the crushed stone slope protection;

[0163] A snow cover rate estimation module, which estimates through the data collected by the collection module. The specific method is as follows:

[0164] Snow cover rate (S): It refers to the proportion of the area covered by snow per unit area. It can be estimated according to the distribution of snow and different physical properties. The snow cover rate can be expressed as:

[0165]

[0166] 1. The mass (M) of the snow can be calculated from the volume and density of the snow:

[0167] M = ρ·V

[0168] 2. Adjust the coverage rate according to the geometric structure of the snow cover layer

[0169] The geometric structure of the slope protection affects the distribution of snow cover. Especially when the slope is relatively large, the snow cover may slide down or be compacted along the slope surface. Therefore, it is necessary to adjust the geometric structure. Set the influence factor f slope (such as slope angle, slope surface flatness, etc.) of the slope protection, and the following formula can be used to correct the snow cover area:

[0170] S adj = S·f slope

[0171] where S is the uncorrected snow cover rate, and f slope is adjusted according to the specific situation of the slope protection. For example, a larger slope will lead to a decrease in the snow cover rate.

[0172] 3. Consider the change in snow depth

[0173] The snow depth also affects the final coverage rate. Especially in the case of uneven snow cover, areas with relatively thin snow depth may not completely cover the ground. At this time, the overall snow cover rate can be adjusted by the average snow depth:

[0174]

[0175] where:

[0176] H avg : the actual average snow depth;

[0177] H max : the maximum snow depth, usually in flat areas or places with less shielding.

[0178] Assume:

[0179] The snow depth H = 0.5m;

[0180] The porosity is 30%, so the density of the snow cover is approximately 300 kg / m;

[0181] The influence factor f of the slope protection slope = 0.85;

[0182] The average snow depth H avg = 0.4m, the maximum snow depth H max = 0.5m;

[0183] The preliminary calculated snow cover rate is 0.6 (60%).

[0184] Then, the final snow cover rate is:

[0185]

[0186] That is, the final snow cover rate is 40.8%.

[0187] Meanwhile, the void ratio can be obtained from the gravel particle size and stacking method of the gravel slope protection. According to the grading theory, the relationship between the void ratio and the particle size distribution can be expressed by the following formula:

[0188]

[0189] where ε is the void ratio;

[0190] V s is the particle volume of the gravel;

[0191] V t is the stacking volume of the gravel.

[0192] The first calculation module is used to calculate the direct reflectivity and the internal refractive index through the snow cover rate and the data collected by the acquisition module. Among them, the direct reflectivity is obtained by weighted calculation of the snow cover rate and the surface reflectivities of two materials, and the internal refractive index is calculated using the combination of the snow transmittance and the cavity reflectivity.

[0193] The calculation method of the direct reflectivity is as follows:

[0194] For the case where the snow completely covers the surface of the slope protection:

[0195] f 积雪 = 1;

[0196] For the case where the snow gradually fills the voids:

[0197]

[0198] where h 积雪 is the snow thickness, P is the void ratio of the gravel slope protection, and H 碎石 is the total thickness of the gravel layer;

[0199] The direct reflection refers to the initial reflection of light at the snow-air surface, which is determined by the snow cover rate f 积雪 and is the weighted average of the reflectivities of the snow and the gravel. The calculation formula is:

[0200] α 直接 = f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 ;

[0201] where f 积雪 is the snow cover rate, defined as the ratio of the snow-covered area to the total area; α 积雪is the reflectivity of the snow surface, α 碎石 is the reflectivity of the gravel surface.

[0202] The method for calculating the internal refractive index is as follows: Internal reflection occurs after the snow fills the voids. When light enters the snow-air cavity-gravel interface in the voids, it undergoes multiple refractions and scatterings. The effective reflectivity α 内部 is used for the calculation:

[0203] α 内部 =(1 - f 积雪 )·T 积雪 ·α 空腔 ;

[0204] where T 积雪 is the transmittance of the snow, representing the ability of light to penetrate the snow surface; the transmittance of the snow is determined by the reflectivity, absorptivity, and scattering rate:

[0205] T 积雪 = 1 - α 积雪 - A 积雪 ;

[0206] In the formula, A 积雪 is the absorptivity of the snow, which depends on the cleanliness of the snow;

[0207] α 空腔 is the internal effective reflectivity of light in the voids;

[0208] The reflectivity inside the voids is determined by the behavior of light between the interfaces of air, gravel, and snow; based on the Fresnel equation for the interface refractive index, it can be expressed as:

[0209]

[0210] where n1 and n2 are the refractive indices of the media on both sides of the interface. For example, the media on both sides of the interface of the gravel pile are gravel and air; the media on both sides of the interface of the gravel-snow pile are gravel and snow; if the snow does not cover all the voids, there are three cases: snow and air, snow and gravel, and gravel and air.

[0211] The reflectivity R x described by the interface represents the reflection contribution on a specific interface,

[0212] α 空腔 = R 空气-碎石 +(1 - R 空气-碎石 )·R 碎石-空气 ;

[0213] where,

[0214] n 空气 = 1.0, n 碎石is the refractive index of the crushed stones, taken as 1.6

[0215] Correction module. The correction module is used to correct the influence of the inclination angle of the crushed stone slope protection on the incident light angle. The correction method adopted by the correction module is as follows: the inclination angle θ of the crushed stone slope protection 坡 will change the angle of the incident light, thereby affecting the actual reflectivity. After considering the inclination angle, the total reflectivity is corrected to:

[0216]

[0217] where θ i is the incident angle, related to the slope inclination angle; α 总 (θ i ) is the angular dependence of the total reflectivity;

[0218] In actual calculation, if it is assumed that the light angles are evenly distributed, it can be simplified to:

[0219]

[0220] Second calculation module. The second calculation module calculates the total reflectivity based on the values obtained by the first calculation module and the correction module. The specific calculation method is as follows:

[0221] α 总 = f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 +(1 - f 积雪 )·T 积雪 ·α 空腔 ;

[0222] All the above values can be obtained through measurement or calculation.

[0223] The formula after considering the inclination angle correction is:

[0224] α 总 =(f 积雪 ·α 积雪 +(1 - f 积雪 )·α 碎石 +(1 - f 积雪 )·T 积雪 ·α 空腔 )·cosθ 坡 .

[0225] The above are only embodiments of the present invention, and common general knowledge of specific structures and / or characteristics in the solution is not described in detail herein. It should be noted that for those skilled in the art, without departing from the structure of the present invention, several modifications and improvements can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the implementation effect of the present invention and the practicability of the patent. The protection scope required by this application shall be subject to the content of its claims, and the specific implementation manners and the like recorded in the specification can be used to interpret the content of the claims.

Claims

1. A method for calculating the reflectivity of a railway gravel slope protection under snow cover, characterized in that: The steps include: S1. Obtain the data of length, width, height, slope ratio and crushed stone particle size of the gravel slope protection; S2, estimate snow cover; S3, calculate direct reflectivity; S4, calculating the internal refractive index of the gravel; S5. Correct the effect of the inclination angle of the gravel slope protection on the reflectivity; S6. Combine steps S2-S4 to obtain the reflectivity of the gravel slope protection after snow accumulation.

2. The method for calculating the reflectivity of a railway gravel slope protection under snow cover according to claim 1 is characterized in that: The specific method of step S3 is as follows: For the case where snow completely covers the slope surface: f 积雪 ＝1； For the case where snow gradually fills the gaps: Among them, h 积雪 is the thickness of snow, P is the porosity of gravel slope protection, H 碎石 is the total thickness of the gravel layer; Direct reflection refers to the initial reflection of light at the surface of snow and air, which is determined by the snow cover f. 积雪 The decision is the weighted average of the reflectivity of snow and gravel, calculated as: a 直接 =f 积雪 ·a 积雪 +(1-f 积雪 )·a 碎石 ; Among them, f 积雪 is the snow cover ratio, defined as the ratio of the snow-covered area to the total area; α 积雪 is the reflectivity of the snow surface, α 碎石 is the reflectivity of the gravel surface.

3. The method for calculating the reflectivity of a railway gravel slope protection under snow cover according to claim 2 is characterized in that: The specific method of step S4 is as follows: internal reflection occurs after the snow fills the gap, and the light enters the snow-gap cavity-gravel interface in the gap and is refracted and scattered multiple times. 内部 Perform the calculation: a 内部 =(1-f 积雪 )·T 积雪 ·a 空腔 ; Among them, T 积雪 is the transmittance of snow, which indicates the ability of light to penetrate the snow surface; the transmittance of snow is determined by reflectivity, absorptivity and scattering: T 积雪 =1-a 积雪 -A 积雪 ; In the formula, A 积雪 is the absorption rate of snow, which depends on the cleanliness of the snow; α 空腔 is the internal effective reflectivity of light in the gap; The reflectivity inside the void is determined by the behavior of light at the interface between air, gravel, and snow; based on the Fresnel equation for the refractive index of the interface, it can be expressed as: Among them, n1 and n2 are the refractive indices of the media on both sides of the interface; Reflectivity R x Interface describes the reflection contribution at a specific interface, a 空腔 =R 空气-碎石 +(1-R 空气-碎石 )·R 碎石-空气 ; in, n 空气 =1.0,n 碎石 is the refractive index of gravel, which is taken as 1.

6.

4. The method for calculating the reflectivity of a railway gravel slope protection under snow cover according to claim 3 is characterized by: The specific method of step S5 is as follows: the inclination angle θ of the gravel slope protection 坡 It will change the angle of the incident light, thus affecting the actual reflectivity. After considering the tilt angle, the total reflectivity is corrected to: Among them, θ i is the angle of incidence, which is related to the slope inclination angle; α 总 (θ i ) is the angular dependence of the total reflectivity; In actual calculation, it is assumed that the light angle is evenly distributed, which can be simplified to:

5. A reflectivity calculation system for railway gravel slope protection under snow cover, characterized in that: include: A collection module, the collection module is used to collect and obtain data on the length, width, height, slope ratio and crushed stone particle size of the crushed stone slope protection; A snow cover ratio estimation module, wherein the snow cover ratio estimation module estimates the snow cover ratio through the data collected by the collection module; A first calculation module, the first calculation module is used to calculate the direct reflectivity and the internal refractive index through the snow coverage rate and the data collected by the collection module; A correction module, the correction module is used to correct the influence of the inclination angle of the gravel slope protection on the change of the incident light angle; The second calculation module calculates the total reflectivity through the values ​​obtained by the first calculation module and the correction module.

6. The reflectivity calculation system for railway gravel slope protection under snow cover according to claim 5, characterized in that: The direct reflectivity is calculated by weighting the snow cover with the surface reflectivity of the two materials, and the internal refractive index is calculated using a combination of snow transmittance and cavity reflectivity.

7. The reflectivity calculation system for railway gravel slope protection under snow cover according to claim 6, characterized in that: The direct reflectivity is calculated as follows: For the case where snow completely covers the slope surface: f 积雪 ＝1； For the case where snow gradually fills the gaps: Among them, h 积雪 is the thickness of snow, P is the porosity of gravel slope protection, H 碎石 is the total thickness of the gravel layer; Direct reflection refers to the initial reflection of light at the surface of snow and air, which is determined by the snow cover f. 积雪 The decision is the weighted average of the reflectivity of snow and gravel, calculated as: a 直接 =f 积雪 ·a 积雪 +(1-f 积雪 )·a 碎石 ; Among them, f 积雪 is the snow cover ratio, defined as the ratio of the snow-covered area to the total area; α 积雪 is the reflectivity of the snow surface, α 碎石 is the reflectivity of the gravel surface.

8. The method for calculating the reflectivity of a railway gravel slope protection under snow cover according to claim 6, characterized in that: The calculation method of the internal refractive index is as follows: internal reflection occurs after the snow fills the gap, and the light enters the snow-air cavity-gravel interface in the gap and is refracted and scattered multiple times. The effective reflectivity α is used 内部 Perform the calculation: a 内部 =(1-f 积雪 )·T 积雪 ·a 空腔 ; Among them, T 积雪 is the transmittance of snow, which indicates the ability of light to penetrate the snow surface; the transmittance of snow is determined by reflectivity, absorptivity and scattering: T 积雪 =1-a 积雪 -A 积雪 ; In the formula, A 积雪 is the absorption rate of snow, which depends on the cleanliness of the snow; α 空腔 is the internal effective reflectivity of light in the gap; The reflectivity inside the void is determined by the behavior of light at the interface between air, gravel, and snow; based on the Fresnel equation for the refractive index of the interface, it can be expressed as: Among them, n1 and n2 are the refractive indices of the media on both sides of the interface; Reflectivity R x Interface describes the reflection contribution at a specific interface, a 空腔 =R 空气-碎石 +(1-R 空气-碎石 )·R 碎石-空气 ; in, n 空气 =1.0,n 碎石 is the refractive index of gravel, which is taken as 1.

6.

9. The method for calculating the reflectivity of a railway gravel slope protection under snow cover according to claim 5, characterized in that: The correction method adopted by the correction module is as follows: the inclination angle θ of the gravel slope protection 坡 It will change the angle of the incident light, thus affecting the actual reflectivity. After considering the tilt angle, the total reflectivity is corrected to: Among them, θ i is the angle of incidence, which is related to the slope inclination angle; α 总 (θ i ) is the angular dependence of the total reflectivity; In actual calculation, it is assumed that the light angle is evenly distributed, which can be simplified to:

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