Railway debris flow prevention target planning method and beam-type grid dam design method

Abstract

The present application discloses a railway debris flow prevention target planning method and a beam type grid dam design method. In view of the defects that the existing technology has not refined technical problems and developed technical solutions, the present application provides a railway debris flow blocking prevention scheme planning method, which combines the blocking prevention engineering and railway civil engineering as a functional combination, and considers the railway civil engineering type, debris flow channel topography, spatial position relationship between railway engineering and channel and other factors in planning, so as to improve the adaptability of the planning scheme from the aspects of geological disaster prevention and railway function exertion. The method first proposes the technical concept of channel-railway combination form classification and prevention planning target classification. The beam type grid dam design method provides three mathematical calculation models corresponding to the design of the grid dam beam spacing under the three prevention targets of peak reduction, flow reduction, and blocking and storing of mud and sand. The technical solution improves the integrity and effectiveness of the railway blocking prevention scheme from two levels of prevention target planning and prevention engineering design.

Description

TECHNICAL FIELD

[0001] The present application relates to a mountainous environment management technology for a transportation line, in particular to a railway debris flow prevention target planning and a debris flow blocking engineering method cooperating with the target planning, and belongs to the field of mountainous environment management technology for a transportation line, geological disaster prevention engineering and building engineering design. BACKGROUND

[0002] The construction and normal operation of a railway line in a mountainous area always rely on the safety of the mountainous environment. Various geological activities in the mountains constitute an important threat to the safety of the mountainous environment, among which debris flow damage is the most serious. Debris flow often causes great damage to the railway line, and the post-disaster recovery is also extremely difficult.

[0003] Engineering countermeasures have always been the main means of railway disaster prevention and mitigation, and blocking engineering is an important form. Blocking dams can be divided into solid dams and penetrating dams. In the practice of railway debris flow prevention, solid dams have limitations such as easy siltation, high cost, short service life, and easy to be washed out. Penetrating dams mainly play the role of blocking coarse and discharging fine, and there are two types of plane grating and framework grating. Due to the development of grating dams towards lightness and assembly, transportation, assembly and maintenance are relatively convenient, so they are more adaptable.

[0004] Although railway debris flow prevention engineering has its own characteristics, various types of prevention engineering are widely used in railway debris flow prevention and have played an important role. However, the existing technology lacks a systematic technology. Most existing researches are still at the stage of case demonstration, result sharing and experience summary, and the normative documents (such as "Debris Flow Prevention Engineering Design Specification" (T / CAGHP021-2018)) only suggest that such engineering may have speciality, and the technical manual only lists the design reference of individual structural parameters of dam and other structures.

[0005] Penetrating dams have proven advantages in existing railway debris flow prevention engineering practices, including avoiding damage to railway buildings by large stones, extending the service life of the engineering, and reducing the pressure of sand and stone transport in the downstream channel. However, the existing technology lacks guidance on structural design, only including individual structural parameter design references, such as "Based on the operation of existing projects, it is recommended that the safety factor of dam body with a height of <15m be controlled at 1.1-1.2, and the safety factor of dam body with a height of >15m be controlled at 1.2-1.5".

[0006] Overall, for the problem of railway debris flow prevention, the existing technology neither has a targeted solution to the problem of prevention target planning nor has a targeted solution to the problem of blocking engineering structure design. SUMMARY

[0007] The present application aims at the deficiencies of the prior art, and provides a technical solution for solving the problem of railway debris flow prevention and control, which can comprehensively consider railway civil engineering and debris flow prevention and control specifications, and provide a technical solution from target planning to blocking engineering structure design.

[0008] To achieve the above-mentioned object, the present application first provides a railway debris flow blocking prevention target planning method, and the technical solution thereof is as follows.

[0009] A railway debris flow blocking prevention scheme planning method, characterized in that for a railway debris flow blocking prevention project, the following steps are implemented:

[0010] Step S100, acquiring railway debris flow prevention project basic data;

[0011] Step S200, completing the construction site selection P i of a transparent blocking dam.

[0012] Step S300, planning debris flow blocking prevention targets at each construction site P i , and the following steps are implemented:

[0013] At each construction site P i , the railway civil engineering type, the debris flow channel topography, and the spatial position relationship between the railway engineering and the channel are combined to determine the channel-railway combination form, which includes the flow-through area-bridge type, the accumulation area-bridge or bridge+subgrade type, and the accumulation area-subgrade type. According to the channel-railway combination form and the basic data of the railway debris flow blocking prevention project, the railway debris flow blocking prevention target at each construction site P i is determined.

[0014] For the flow-through area-bridge type:

[0015] If the flow capacity of the railway bridge is less than the peak flow Q D of the debris flow under the design standard DC, the blocking prevention target is peak reduction.

[0016] If the channel longitudinal gradient J4 at the railway bridge crossing is small, or the debris flow specific gravity γ is large, the blocking prevention target is specific gravity reduction.

[0017] For the accumulation area-bridge or bridge+subgrade type:

[0018] If the flow-through area channel bed longitudinal gradient J2 is large, the accumulation area longitudinal gradient J3 is small, and the accumulation area steep and gentle slope change amplitude is large, the blocking prevention target is debris sand storage.

[0019] If the flow capacity of the railway bridge is less than the peak flow Q D of the debris flow under the design standard DC., or the area Z and downstream exist the damming-river-blocking lake-bursting flood disaster chain hidden danger, the blocking prevention and control target is to cut peak and reduce flow,

[0020] If the longitudinal gradient J4 of the channel at the railway bridge crossing is small and the debris flow specific gravity γ is large, or the drainage groove slope J dc is small and the debris flow specific gravity γ is large, the blocking prevention and control target is to adjust and reduce the specific gravity, and for the accumulation area-roadbed type:

[0021] If the maximum solid amount W c allowed to be discharged by the railway passing section is less than the total amount V s of solid materials under the design standard DC, the blocking prevention and control target is to block and store mud and sand,

[0022] If the railway roadbed culvert flow capacity is less than the peak flow Q D of the debris flow under the design standard DC, the blocking prevention and control target is to cut peak and reduce flow.

[0023] The above-mentioned railway debris flow blocking prevention and control scheme planning method specifically considers that in the debris flow prevention and control planning, due to different regions in the debris flow channel, the physical and motion characteristics of the debris flow are different, so the blocking prevention and control points of the debris flow are different; at the same time, due to different railway civil engineering, the balance and emphasis factors of the protection of the railway structure and / or function are different, thus, by first dividing the channel-railway combination form, the miscellaneous factors in the planning can be simplified, and the gist of the planning target is highlighted. On this basis, further, for different blocking prevention and control points, more specific debris flow and channel environment indexes are selected, which are compared with different capacity indexes of the railway, the prevention and control planning target is divided into three types of cutting peak and reducing flow, adjusting and reducing specific gravity, and blocking and storing mud and sand, so that the scientific planning of the railway line debris flow blocking prevention and control target in service is finally realized.

[0024] In the above-mentioned railway debris flow blocking prevention and control scheme planning method, the channel-railway combination form specifically has three types: flow-through area-bridge type, which means that the blocking engineering is located in the flow-through area of the debris flow channel, and the railway civil engineering as the protection object belongs to the bridge or mainly to the bridge. Accumulation area-bridge or bridge+roadbed type, which means that the blocking engineering is located in the accumulation area of the debris flow channel, and the railway civil engineering as the protection object belongs to the bridge or mainly to the bridge, or simultaneously includes the bridge and the roadbed. Accumulation area-roadbed type, which means that the blocking engineering is located in the accumulation area of the debris flow channel, and the railway civil engineering as the protection object belongs to the roadbed.

[0025] For the planning project that needs to consider multi-site prevention and control due to the great threat and high risk of the debris flow disaster or hidden danger in the debris flow channel, there may be many optional construction sites P i , and from the engineering practical point of view, it is impossible to build blocking engineering at each place. The present application provides an optimization scheme. Specifically as follows.

[0026] In step S200, the railway crossing area in the channel is delineated by using the basic data, and the layout area Z of the retaining project is planned in the crossing area according to the debris flow prevention specification; in the area Z, the construction site of the through-type retaining dam is preliminarily screened as the primary dam site PP according to the debris flow prevention project design specification i , the reservoir capacity V of the through-type retaining dam that can be constructed at each PP i is determined i , each PP i is numbered in sequence i along the downstream to upstream of the channel, i.e. i = 1, 2, …, n; the PP i combination that meets the condition of formula 1 and has the least number of PP i is screened from all PP i , and the PP i combination is the construction site P of the through-type retaining dam i , or the PP i combination that meets the condition of formula 1 and has the least number of PP i is screened from all PP i , and when the PP i combination is not unique, the most suitable one is further screened as the construction site P of the through-type retaining dam by combining the debris flow disaster prevention project design specification and / or the site construction condition i . In the engineering practice, the further screening can generally be completed based on the specification, construction condition, construction experience, etc. For example, the PP i combination at the bottleneck of the channel with good geological condition, narrow mouth and wide belly can be specifically selected to determine the construction site P i .

[0027]

[0028] In the formula, V s is the total amount of solid matter of the next debris flow under the design standard DC, and V dis is the maximum allowable discharge amount under the safety condition of the downstream railway engineering facilities, which are determined according to the basic data of the railway debris flow prevention project.

[0029] The above railway debris flow retaining prevention scheme planning method can also be optimized as follows. The channel longitudinal gradient J4 at the railway bridge crossing is J4 < J c , J c is the gradient of the area Z that is not scoured and not silted, which is determined according to the basic data, the debris flow specific gravity γ is γ > γ c , γ c is the critical debris flow specific gravity of the area Z that is not scoured and not silted, which is determined according to the basic data. J c can be determined by simulation experiment or according to formula 2, wherein γs is the specific gravity of solid material in debris flow, unit kN / m 3 , which is determined according to basic data.

[0030]

[0031] The large longitudinal slope J2 of the channel bed in the flow area is J2>200‰, the small longitudinal slope J3 of the channel bed in the accumulation area is J3<100‰, and the large variation range of steep and gentle slopes is the slope drop ratio of the steep slope to the gentle slope section>2.

[0032] The hidden danger of the disaster chain of river blocking, dammed lake and flood bursting is that the regional Z debris flow directly discharges to the main river channel through the channel in the accumulation area.

[0033] The slope J of the drainage groove dc is J dc < J c .

[0034] Another object of the present application is to further solve the method for designing the beam-type grid dam according to the prevention and control target after determining the prevention and control target of the railway debris flow at the construction site P i . The beam-type grid dam is a kind of blocking structure with simple structure, material saving and high stability, and has good prevention and control effect and application prospect in the debris flow prevention and control engineering system, especially in the prevention and control of railway, highway and scenic area debris flow. The structural parameters of the beam-type grid dam and the dam height and the beam spacing are two key parameters, the former controls the volume of the dam, and the latter controls the permeability of the dam. Both of them jointly determine the blocking performance of the beam-type grid dam. The present application provides the following design method.

[0035] A beam-type grid dam design method, characterized in that: the railway debris flow prevention and control scheme planning method determines the blocking and prevention target of each permeable-type blocking dam construction site P i ; the dam height H of the beam-type grid dam is determined by using the basic data of the railway debris flow prevention and control project, and the blocking and prevention target is to block and store mud and sand; the sand blocking rate R t of the beam-type grid dam is taken as the design target, and the beam spacing δh is designed according to equation group 3,

[0036]

[0037] In the formula, R t is the sand blocking rate of the beam-type grid dam,

[0038] γ D is the specific gravity of debris flow under the design standard DC, unit kN / m 3 , which is determined according to the design standard DC,

[0039] γ s , γ w- the specific weight of solid material in the debris flow, the specific weight of water, respectively, in kN / m 3 , determined according to the basic data,

[0040] d 95 - the characteristic grain size of the debris flow, in m, determined according to the basic data,

[0041] W c - the maximum amount of solids allowed to be discharged in the railway section, in m 3 , determined according to the basic data.

[0042] The above-mentioned design method of the beam-type grid dam, further, for the target of blocking and preventing is to reduce the peak flow, taking the peak reduction rate Δ Q of the beam-type grid dam as the design target, the horizontal beam spacing δh is designed according to equation group 4,

[0043]

[0044] In the formula, Δ Q - the peak reduction rate of the beam-type grid dam,

[0045] Q D - the peak flow of the debris flow under the design standard DC, in m 3 , determined according to the design standard DC,

[0046] Q c - the maximum flow of the debris flow allowed in the railway section, in m 3 , determined according to the basic data.

[0047] Further, for the target of blocking and preventing is to adjust and reduce the specific weight, taking the specific weight reduction rate Δ γ of the beam-type grid dam as the design target, the horizontal beam spacing δh is designed according to equation group 5,

[0048]

[0049] In the formula, Δ γ - the specific weight reduction rate of the beam-type grid dam,

[0050] γ D - the specific weight of the debris flow under the design standard DC, in kN / m 3 , determined according to the design standard DC,

[0051] γ c - the critical specific weight of the debris flow that does not wash away or silt in the railway section, in kN / m 3 , determined according to the basic data.

[0052] The above-mentioned design method of the beam-type grid dam, if the construction site P iWhen the blocking prevention target is at least two, different design targets are determined according to different blocking prevention targets, different beam spacings δh are designed according to the formula, and the minimum value is taken as the final design value.

[0053] The technical scheme of the present application, the railway debris flow blocking prevention scheme planning method or the beam type grid dam design method, the applicable conditions include: the mud type debris flow, and the debris flow specific gravity γ D = 13kN / m 3 ~ 21kN / m 3 , the average longitudinal slope J of the channel = 100 ‰ ~ 300 ‰, the debris flow Froude number F r = 0.5 ~ 10.

[0054] The field investigation in the present technology includes various data collection, remote sensing interpretation, topographic survey and engineering geological mapping, geological environment investigation, exploration, engineering geophysical exploration, as well as existing simulation experiments, test experiments, observation experiments, analysis experiments in the field, and historical disaster record acquisition, and related technical specifications, and experience methods and data acquisition with reference to the role of experience methods and data acquisition. Investigate the formation conditions, activity characteristics, damage range, etc. of the debris flow, find out the main source characteristics (distribution, quantity and scale) of the debris flow and the engineering geological conditions of the proposed management engineering site, analyze the nature, development process and evolution trend of the debris flow, and focus on analyzing the comprehensive characteristics of civil engineering and topography and geology at the junction of the railway and the channel environment, the influence and threat of the debris flow movement on the railway. The data obtained from the field investigation are collectively referred to as the basic data of the present technical scheme.

[0055] Compared with the prior art, the beneficial effects of the present application are: (1) The debris flow prevention and control engineering measures are specifically applied to the mountain environment governance and disaster prevention of railway transportation lines, and there are many engineering practices, but it still stays at the level of case experience summary sharing and individual parameter reference value of engineering construction, and lacks a technical solution based on the debris flow disaster environment and railway civil engineering background. The present application provides a targeted solution to the problem of railway debris flow prevention and control, so that the debris flow prevention and control scheme planned around the railway transportation line can directionally retrieve comprehensive basic data from the two projects of disaster prevention and railway engineering, and then screen the prevention and control target of the blocking project through a clear technical route, so as to scientifically select various specific targets in the relatively vague "protection purpose" and improve the integrity and effectiveness of the blocking prevention scheme. (2) The railway debris flow blocking prevention scheme planning method of the present application combines the blocking prevention project with the railway civil engineering as a functional combination, and factors such as the type of railway civil engineering, the terrain of debris flow channel, and the spatial position relationship between railway engineering and channel are all included in the specific planning of the blocking prevention project, so as to improve the adaptability of the planning scheme from the aspects of geological disaster prevention and railway function exertion. The classification of channel-railway combination form and the selection of more specific debris flow and channel environment indexes based on this classification and the comparison with different capacity indexes of railway, and the division of prevention and control planning targets into three categories of peak reduction, intensity reduction and sediment storage are all first proposed in this technical field. (3) The beam grid dam design method of the present application solves the technical problem of how to complete the main parameter design of the beam grid dam around the prevention and control target under the condition that different blocking prevention targets are determined. Based on the previous research, the design method provides three mathematical calculation models corresponding to the three prevention and control targets of peak reduction, intensity reduction and sediment storage, respectively, to complete the design of beam spacing. (4) The technical solution of the present application formally proposes a technical problem that has not been proposed in the prior art, and solves the technical problem from two levels of prevention and control target planning and prevention and control engineering design, which is a debris flow prevention and control technology based on railway transportation line in a true sense. BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 is a railway debris flow blocking prevention scheme planning method schematic diagram.

[0057] Figure 2 is a schematic diagram of the accumulation area-bridge or bridge+subgrade type.

[0058] Figure 3 is a railway debris flow blocking prevention target planning schematic diagram.

[0059] The numerical markers in the drawings are: 1 debris flow channel; 2 railway line; 3 bridge; 4 subgrade; 5 main river channel. DETAILED DESCRIPTION

[0060] The preferred embodiments of the present application are further described below with reference to the accompanying drawings.

[0061] Example One

[0062] The method is used for planning a railway debris flow blocking prevention scheme. Figure 1 It is a schematic diagram of a railway debris flow blocking prevention scheme planning method.

[0063] A railway line passes through a debris flow channel. During railway operation, the water and soil conditions of the channel are greatly changed due to the influence of the comprehensive environment, and the frequency of debris flow disasters increases. It is necessary to construct debris flow prevention engineering measures to govern the mountain environment and ensure the safety of railway operation. The method is used for planning a railway debris flow blocking prevention project.

[0064] 1. Obtain data and determine design standard DC

[0065] Carry out on-site investigation of the railway debris flow prevention project to obtain basic data of the railway debris flow prevention project. The project basic data includes railway engineering basic data, basin and debris flow channel basic data, debris flow characteristic data, project engineering design standard DC, and railway engineering and debris flow prevention specification and / or guideline documents.

[0066] Since the railway in this example is located in the Sichuan-Tibet mountainous area and belongs to the Sichuan-Tibet railway network, the selected reference specification and / or guideline documents mainly include three documents: Railway Engineering Bad Geological Survey Regulations TB10027-2022, Debris Flow Prevention Engineering Design Specification TCAGHP021-2018, and Sichuan-Tibet Railway Debris Flow Prevention Technical Guidelines 2021. The project engineering design standard DC is determined according to the safety grade of the project engineering. Specifically, the debris flow prevention engineering with a safety grade of one is considered to occur once every 100 years, the debris flow prevention engineering with a safety grade of two or three is considered to occur not less than once every 20 years, and if necessary, it is considered to occur once every 50 years. The safety grade of the project engineering is determined according to the degree of harm shown by the historical records of the project site debris flow disasters and the importance of the prevention engineering facilities, according to the engineering design specification.

[0067] Some of the basic data is shown in Table 1. Among them, V dis The value of W c .

[0068] Table 1 Some of the basic data

[0069]

[0070] In Table 1, the area Z is not a debris flow channel with a slope J c The value is determined by using the empirical formula (formula 2).

[0071]

[0072] In this case, the debris flow is of the debris type, and the debris flow severity γ under the design standard DC D =13kN / m 3 ~21kN / m 3 , average longitudinal gradient of channel J = 100‰ ~ 300‰, debris flow Froude number F r =0.5~10, so the conditions for completing the blocking prevention and control planning by adopting the method of the present invention are met.

[0073] 2. Complete the site selection for the construction of the permeable retaining dam i

[0074] Using basic data, the railway crossing area in the debris flow channel is delineated. Within the crossing area, the barrier engineering layout area Z is planned according to the debris flow prevention and control specifications. Within area Z, the site for the construction of a permeable barrier dam is preliminarily selected as the primary dam site PP according to the debris flow prevention and control engineering design specifications. i , determine each PP i The height H of the permeable retaining dam that can be constructed i , according to H i Determine the storage capacity V i . Each PP i From the downstream to the upstream of the channel, the numbers are i, i = 1, 2, ..., n. i The filter satisfies the conditions of formula 1 and PP i The smallest number of PP i Combination, the resulting PP i The combination is the site selection for the construction of a permeable retaining dam P i .

[0075]

[0076] In this example, in region Z, the primary site PP for the see-through retaining dam is i There are 3 locations in total, namely PP1: H1=10m, V1=7.5*10 4 m 3 , PP2: H2=12m, V2=1*10 5 m 3 , PP3: H3=5m, V3=4.5*10 4 m 3 According to the conditions of formula 1, it is determined that only one permeable debris flow barrier dam is needed at PP2 to meet the railway disaster prevention requirements.

[0077] 3. Plan the construction site P i The goal of debris flow prevention and control

[0078] At each selected permeable retaining dam construction site Pi The channel-railway combination form is determined by combining the railway civil engineering type, debris flow channel topography, and the spatial relationship between the railway engineering and the channel. Channel-railway combination forms include flow area-bridge type, accumulation area-bridge type, or bridge + roadbed type ( Figure 2 The P is the accumulation area-bridge or bridge + roadbed type diagram), accumulation area-roadbed type; and then the construction site P is determined based on the channel-railway combination form and the basic data of the railway debris flow prevention and control project. i The railway debris flow prevention and control target is at the site.

[0079] Figure 3 This is a schematic diagram of the target planning for preventing and controlling railway debris flows. In the figure, ① the flow capacity of the railway bridge is less than the peak flow rate Q of the debris flow under the design standard DC. D ; ② The longitudinal gradient J4 of the ditch where the railway bridge crosses is small, or the debris flow severity γ is large; ③ The longitudinal gradient J2 of the ditch bed in the flow area is large, the longitudinal gradient J3 in the accumulation area is small, and the steep and gentle slopes in the accumulation area vary greatly; ④ The flow capacity of the railway bridge culvert is less than the peak flow rate Q of the debris flow under the design standard DC D ⑤ The longitudinal gradient J4 of the channel where the railway bridge crosses is small and the debris flow severity γ is large, or the drainage channel slope J dc The maximum amount of solids allowed to be discharged from the railway section is W. c Less than the total amount of solid matter V in the next debris flow under the design standard DC s ⑦ The flow capacity of the railway embankment culvert is less than the peak flow rate Q of the debris flow under the design standard DC D .

[0080] In this case, the dam site has been screened and determined to be PP2. Combining the data in Table 1 with the data in Table 2, the blocking and prevention target of the permeable debris flow dam at this location is determined according to the above rules. First, it is determined that the channel-railway combination form at this location is the accumulation area-bridge + roadbed type. The basic data of the watershed and debris flow channel at PP2 are determined, see Table 2. Since J2=207‰>200‰, J3=92‰<100‰, and the steep and gentle slopes in the accumulation area vary greatly (the slope ratio of the steep slope to the gentle slope section = 3>2), the blocking and prevention target of the railway debris flow at this location should meet the requirements of intercepting mud and sand; and because the flow capacity of the railway bridge and culvert (Q c =150.60m 3 / s)<DC under the peak flow rate of debris flow (Q D =250.75m 3 / s), so the goal of preventing and controlling the debris flow at this railway section should be to reduce the peak flow. Therefore, the goal of preventing and controlling the debris flow at PP2 should be to take into account both the interception of mud and sand and the reduction of peak flow. Calculate R according to formula 3-2 and formula 4-2 respectively. t= 0.71, Δ Q = 0.60.

[0081] Table 2 is the partial basic data of PP2 (part of the river basin and debris flow channel)

[0082]

[0083] Example Two

[0084] Based on the planning of the permeable debris flow dam completed in Example One, the dam is designed based on the target of the dam.

[0085] The beam grid dam is designed as the specific form of the permeable debris flow dam, and the beam grid dam spacing δh is designed by using the target of the dam.

[0086] Continue to take PP2 in Example One as an example. It has been determined that the target of the dam is to consider the retention of mud and sand (R t = 0.71) and peak reduction (Δ Q = 0.60), so R t ≥ 0.71 and Δ Q ≥ 0.60 should be designed. The average longitudinal slope J of the channel at the dam site PP2 is 120 ‰.

[0087] The target of R t ≥ 0.71 is designed, and the beam spacing δh is designed according to formula 3-1, and the beam spacing δh = 1.25 m; the target of Δ Q ≥ 0.60 is designed, and the beam spacing δh is designed according to formula 4-1, and δh = 1.59 m. The smaller value is taken, so the beam spacing δh of the beam grid dam is designed to be 1.25 m.

Claims

1. A method for planning a railway debris flow blocking prevention scheme, characterized in that: For the railway debris flow blocking prevention project, the following steps are implemented: Step S100, obtaining the basic data of the railway debris flow prevention project; Step S200, completion of the construction site selection P of the through-type dam i ; Step S300, planning each construction site P i of debris flow blocking prevention target, is implemented according to the following steps: At each construction site P i , in combination with the railway civil engineering type, the debris flow channel topography, the spatial position relationship between the railway engineering and the channel, the channel-railway combination form at the site is determined, which includes the flow passage area-bridge type, the accumulation area-bridge or bridge+subgrade type, and the accumulation area-subgrade type; according to the channel-railway combination form and the basic data of the railway debris flow blocking prevention project, the railway debris flow blocking prevention target at each construction site P i is determined. For the flow area-bridge type: If the flow capacity of the railway bridge is less than the peak flow Q of the debris flow under the design standard DC D , the blocking prevention target is to reduce the peak flow. If the longitudinal gradient J4 of the channel at the railway bridge crossing is small, or the debris flow specific gravity γ is large, the blocking prevention target is to adjust and reduce the specific gravity; For the accumulation area-bridge or bridge+subgrade type: If the three conditions of large longitudinal gradient J2 of the channel bed in the flow area, small longitudinal gradient J3 of the channel bed in the accumulation area, and large change amplitude of steep and gentle slopes in the accumulation area are met at the same time, the blocking prevention target is to block and store the mud and sand, If the flow capacity of the railway bridge and culvert is less than the peak flow Q of the debris flow under the design standard DC D , or there is a hidden danger of the damming-yazoo lake-bursting flood disaster chain in the region Z and downstream, the blocking prevention target is to reduce peak flow and reduce flow, If the railway bridge crosses the channel with small longitudinal gradient J4 and large debris flow specific gravity γ, or the drainage ditch slope J dc is small and the debris flow specific gravity γ is large, the blocking prevention target is to reduce the specific gravity. For the accumulation area-subgrade type: W - the maximum amount of solids allowed to be discharged by the railway section c V - the total amount of solids in the next debris flow under the design criterion DC s , the blocking prevention target is to block and store the mud and sand, and if the flow capacity of the railway subgrade culvert is less than the peak flow Q of the debris flow under the design criterion DC D , the blocking prevention target is to reduce the peak flow.

2. The planning method of claim 1, wherein: The step S200, using the basic data to delimit the channel railway crossing area, in the crossing area according to the debris flow prevention specification planning blocking engineering layout area Z;In the area Z, according to the debris flow prevention engineering design specification preliminary screening through type blocking dam construction site as the initial selection dam site PP i , determine the reservoir capacity V i The through type blocking dam that can be built at each PP i , each PP i Along the downstream to upstream of the channel i, i=1, 2, …, n;From all PP i Screening meets the condition of formula 1 and the least number of PP i PP i Combination, the PP i Combination is the through type blocking dam construction site P i , or from all PP i Screening meets the condition of formula 1 and the least number of PP i PP i Combination, and when PP i Combination is not unique, further screening the most suitable one according to the debris flow disaster prevention engineering design specification and / or site construction conditions as the through type blocking dam construction site P i ; In the formula, V s V is the total amount of solid materials of the next debris flow under the design standard DC dis The maximum allowable discharge under the safety conditions of downstream railway engineering facilities is determined based on the basic data of the railway debris flow prevention project.

3. The planning method according to claim 2, characterized in that: The railway bridge across the channel longitudinal slope is small J4 < J c , c The area Z is not washed and not silted slope, which is determined by the basic data. The mudslide specific gravity γ is large γ > γ c , c The critical specific gravity of mudslide in the area Z is not washed and not silted, which is determined by the basic data. The large longitudinal gradient J2 of the channel bed in the flow area is J2>200‰, the small longitudinal gradient J3 of the channel bed in the accumulation area is J3<100‰, the large change amplitude of steep and gentle slopes is the slope gradient ratio of steep slope to gentle slope segment>2, and the damming-river blocking-lake breaching-flood disaster chain hidden danger is that the regional Z debris flow is directly discharged into the main river channel through the accumulation area channel. The drain groove slope J dc Small is J dc <J c .

4. The planning method of claim 3, wherein: J c determined according to Formula 2, In the formula, γs is the specific gravity of solid materials in the debris flow, in kN / m 3 , which is determined according to basic data.

5. A method of designing a beam-type grid dam, characterized by: The railway debris flow prevention and control program planning method according to claim 4 is used to determine the construction site P of each permeable retaining dam. i The blocking and prevention target is to use the basic data of the railway debris flow prevention project to determine the height H of the beam grid dam. The blocking and prevention target is to intercept and store mud and sand. The sand interception rate R of the beam grid dam is t As the design goal, the beam spacing δh is designed according to the equation group 3, In the formula, R t - the percentage of sand retention of the beam-type grid dam, γ D - Design standard DC of the debris flow specific weight, in kN / m 3 , determined in accordance with the design standard DC, γ s , γ w - specific weight of solid material and water in the debris flow, kN / m 3 , determined depending on the basic data d 95 - Debris flow characteristic grain size, in m, determined from base data, W c - Maximum amount of solids allowed to be discharged by the railway passing section, in m 3 , determined from the basic data.

6. The design method of claim 5, wherein: For the said barrier, the control target is to reduce peak flow and peak discharge, and the peak reduction rate Δ Q The beam spacing δh is designed according to the equation group of formula 4, where Δ Q - crest reduction ratio of the beam-type grid dam, Q D - Design standard DC debris flow peak flow, in m 3 , determined in accordance with the design standard DC, Q c - Maximum debris flow flow allowed by the railway section, in m 3 , determined from the basic data.

7. The design method of claim 6, wherein: For the said barrier control target is to reduce the severity, with beam type grid dam weight reduction rate Δ γ For the design target, the beam spacing δh is designed by equation 5 where Δ γ - weight reduction rate of the beam-type grid dam, γ D - Design standard debris flow specific weight, in kN / m 3 , determined in accordance with the design standard DC, γ c - critical degree of non-avalanche and non-deposition of the railway section, in kN / m 3 , determined on the basis of the basic data.

8. The design method of claim 7, wherein: If the construction site P i is selected, the target of the blocking prevention is at least two kinds, different design targets are determined according to different blocking prevention targets, and the distance between the beams δh is designed according to the formula, and the minimum value is the final design value.

9. The planning method according to any one of claims 1 to 4 or the designing method according to any one of claims 5 to 8, characterized in that: Applicable conditions include debris flow of mud type, and at the same time meet the design standard DC of debris flow specific weight γ D = 13 kN / m 3 ~ 21 kN / m 3 , channel average longitudinal gradient J = 100 ~ 300 ‰, debris flow Froude number F r = 0.5 ~ 10.

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