Multi - level stacked retaining prevention and control method for debris flow

Abstract

The present invention discloses a multi-level cascade blocking prevention and control method for debris flows, which includes the following steps: obtaining the terrain of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the threat objects of the debris flow disaster in the debris flow prevention and control area; determining the grade of the debris flow blocking structure building; selecting the construction location of a single-stage flexible debris flow blocking structure; determining the structural parameters of the single-stage flexible debris flow blocking structure; establishing a single-stage flexible debris flow blocking structure, and the single-stage prevention and control work is completed; continuing to establish a single-stage flexible debris flow blocking structure to obtain a multi-level flexible debris flow blocking structure, and the multi-level prevention and control work is completed. For the multi-level cascade blocking prevention and control method for debris flows, the present invention establishes a flexible debris flow blocking structure in the channel area with frequent debris flows. After the debris flow solids in the blocking structure are filled up, there is no need to clean them. A new flexible debris flow blocking structure is established again upstream of the original blocking structure filled with debris flow solids, which is beneficial to the treatment work in the area with frequent debris flows.

Description

Technical Field

[0001] The present invention belongs to the technical field of debris flow prevention and control, and relates to a multi-stage stacked debris flow blocking and prevention method. Background Art

[0002] Debris flow is a type of mountain natural disaster, characterized by sudden outbreak, short duration, high speed, large energy, strong destructive power, etc. For debris flow prevention and control, a comprehensive debris flow prevention and control system mainly based on "stabilization, blocking, and drainage" has gradually formed so far. Usually, various types of retaining dams are built in the debris flow channel to intercept the solid matter of the debris flow. However, the debris flow retaining dams generally have problems such as complex construction, loss of interception ability after being silted up in front of the dam, and difficult silt cleaning.

[0003] In summary, the existing technology has problems such as complex debris flow blocking structure, long construction time, and difficult post-construction silt cleaning. Summary of the Invention

[0004] The purpose of the present invention is to provide a multi-stage stacked debris flow blocking and prevention method, which solves the problems of complex debris flow blocking structure, long construction time, and difficult post-construction silt cleaning in the existing technology.

[0005] The technical solution adopted by the present invention is a multi-stage stacked debris flow blocking and prevention method, including the following steps:

[0006] S1. Obtain the topography of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the threat objects of the debris flow disaster in the debris flow prevention and control area;

[0007] S2. Determine the safety level of the debris flow prevention and control project according to the threat objects of the debris flow disaster;

[0008] S3. Determine the grade of the debris flow blocking structure building according to the safety level of the debris flow prevention and control project;

[0009] S4. Select the construction location of a single-stage flexible debris flow blocking structure in combination with the topography of the debris flow channel and the geological conditions of the channel;

[0010] S5. Determine the structural parameters of the single-stage flexible debris flow blocking structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow blocking structure;

[0011] S6. Build a single-stage flexible debris flow blocking structure according to the structural parameters and construction location of the single-stage flexible debris flow blocking structure, and the single-stage prevention work is completed;

[0012] S7. According to the siltation situation in the single-stage flexible debris flow blocking structure, continue to build a single-stage flexible debris flow blocking structure upstream of it to obtain a multi-stage flexible debris flow blocking structure, and the multi-stage prevention work is completed.

[0013] The characteristics of the present invention also lie in:

[0014] The main parameters of debris flow include the maximum particle size D of debris flow, the flood volume v of debris flow, the occurrence frequency of debris flow, the specific gravity γ of debris flow, the internal friction angle ф of debris flow deposits, and the cohesion C of debris flow deposits.

[0015] The safety level of debris flow prevention and control projects is determined based on the threat objects of debris flow disasters in combination with the design specifications for debris flow prevention and control projects; the safety levels of debris flow prevention and control projects include Safety Level I, Safety Level II, Safety Level III, and Safety Level IV.

[0016] The grade of debris flow blocking and retaining structure buildings is determined based on the safety level of debris flow prevention and control projects in combination with the safety level information in the design specifications for debris flow prevention and control projects and the building grade information in the design specifications for rolled earth-rock dams; the corresponding relationship between the safety level of debris flow prevention and control projects and the grade of debris flow blocking and retaining structure buildings is as follows: Safety Level I corresponds to Grade I buildings, Safety Level II corresponds to Grade II buildings, Safety Level III corresponds to Grade III buildings, and Safety Level IV corresponds to Grade IV buildings.

[0017] The structural parameters of a single-stage flexible debris flow blocking and retaining structure include the vertical height H of the blocking net, the inclination angle A of the blocking net, and the horizontal length L of the blocking net;

[0018] The ratio of the vertical height H of the blocking net to the maximum particle size D of debris flow is (1.5 - 2):1.

[0019] The inclination angle A of the blocking net and the horizontal length L of the blocking net in the structural parameters of a single-stage flexible debris flow blocking and retaining structure are obtained through the following steps:

[0020] A1. Combine the internal friction angle ф of debris flow deposits, the cohesion C of debris flow deposits, and design experience to determine the preliminary inclination angle A0 of the blocking net. Combine the topography and geological conditions of the debris flow channel, the construction location of the single-stage flexible debris flow blocking and retaining structure, the flood volume v of debris flow, the occurrence frequency of debris flow, and the grade of debris flow blocking and retaining structure buildings to obtain the set solid object blocking volume V0;

[0021] A2. Combine the construction location of the single-stage flexible debris flow blocking and retaining structure, the topography and geological conditions of the debris flow channel, the vertical height H of the blocking net, the preliminary inclination angle A0 of the blocking net, and the set solid object blocking volume V0 to obtain the theoretical horizontal length L0 of the blocking net and the designed length L1 of the blocking net interception margin;

[0022] A3. Add the theoretical horizontal length L0 of the blocking net and the designed length L1 of the blocking net interception margin to obtain the preliminary horizontal length L2 of the blocking net;

[0023] A4. Calculate the safety factor of the accumulation body under the control condition based on the rigid body limit equilibrium method. The value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is not less than 0 and not greater than 0.2. The inclination angle A of the retaining net is taken as the initial inclination angle A0 of the retaining net, and the horizontal length L of the retaining net is taken as the initial horizontal length L2 of the retaining net. If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is less than 0 or greater than 0.2, adjust the initial inclination angle A0 of the retaining net.

[0024] If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is less than 0, it means that the safety factor of the accumulation body under the control condition does not meet the requirements of the design code for rolled earth-rock dams, and the initial inclination angle A0 of the retaining net should be reduced. If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is greater than 0.2, it means that the safety margin of the design scheme is large and the economy is low, and the initial inclination angle A0 of the retaining net should be increased.

[0025] The safety factor of the accumulation body under the control condition is calculated respectively for the normal operation condition, the extraordinary operation condition I, and the extraordinary operation condition II by using the rigid body limit equilibrium method according to the analysis method of dam slope stability calculation in the design code for rolled earth-rock dams SL274 or the design code for rolled earth-rock dams NB / T10872. The safety factor of the accumulation body under the normal operation condition is the safety factor of the accumulation body under the normal operation condition, the safety factor of the accumulation body under the extraordinary operation condition I is the safety factor of the accumulation body under the rainstorm condition, and the safety factor of the accumulation body under the extraordinary operation condition II is the safety factor of the accumulation body under the earthquake condition.

[0026] Specifically, in S7, when the terrain of the debris flow channel and the threat objects of the debris flow disaster situation remain unchanged and the accumulated amount of solids in the established single-stage flexible debris flow retaining structure reaches the set solid retaining amount or the distance between the siltation surface in front of the retaining net and the top of the retaining net is 0.5m - 1.0m, repeat steps S4 - S6 to continue to establish a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed. If the terrain of the debris flow channel and the threat objects of the debris flow disaster situation change and the accumulated amount of solids in the established single-stage flexible debris flow retaining structure reaches the set solid retaining amount or the distance between the siltation surface in front of the retaining net and the top of the retaining net is 0.5m - 1.0m, repeat steps S1 - S6 to continue to establish a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

[0027] The beneficial effects of the present invention are as follows: A flexible debris flow retaining structure is established in the gully area with frequent debris flows. Through this retaining structure, the solid debris in the debris flow is intercepted and fixed. After the retaining structure is filled with the solid debris in the debris flow, it does not need to be cleaned. A new flexible debris flow retaining structure is established again upstream of the original retaining structure filled with the solid debris in the debris flow, which is beneficial to the treatment work in the area with frequent debris flows. The flexible debris flow retaining structure in the present invention has a simple structure, convenient construction, low construction difficulty, fast construction speed and low cost, and can be quickly built to play the role of debris flow treatment; the retaining structure of the present invention ensures that the debris flow reaches a self-stabilized state after deposition, ensuring the safety and reliability of the retaining measures; the present invention avoids the loss of the interception ability after the retaining dam is filled, and reduces the debris flow prevention and control pressure because the solid debris deposited in the retaining dam does not need to be cleaned, and multiple retaining measures can be flexibly set according to the site conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic flow chart of the multi-stage stacked retaining and prevention method for debris flows of the present invention;

[0029] Figure 2 is a schematic diagram of the process of a flexible debris flow retaining structure retaining debris flow in an embodiment of the present invention;

[0030] Figure 3 is a schematic structural diagram of a single-stage flexible debris flow retaining unit in an embodiment of the present invention.

[0031] In the figure, 1, retaining net; 2, first fixed extended foundation; 3, second fixed extended foundation; 4, third fixed extended foundation; 5, ground; 6, first support mechanism; 7, second support mechanism; 8, bottom fixing mechanism; 9, single-stage flexible debris flow retaining structure. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] The multi-stage stacked retaining and prevention method for debris flows, as Figure 1 shown, includes the following steps:

[0034] S1. Obtain the terrain of the debris flow gully, the geological conditions of the gully, the main parameters of the debris flow, and the threat objects of the debris flow disaster in the debris flow prevention and control area;

[0035] The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris flow deposit, and the cohesion C of the debris flow deposit;

[0036] S2. Determine the safety level of the debris flow prevention and control project according to the threat objects of the debris flow disaster;

[0037] The safety level of debris flow control projects is determined based on the threat targets of debris flow disasters in combination with the design specifications for debris flow control projects; the safety levels of debris flow control projects include Safety Level I, Safety Level II, Safety Level III, and Safety Level IV;

[0038] S3. Determine the grade of the debris flow retaining structure buildings based on the safety level of the debris flow control project;

[0039] The grade of the debris flow retaining structure buildings is determined based on the safety level of the debris flow control project in combination with the safety level information in the design specifications for debris flow control projects and the building grade information in the design specifications for rolled earth-rock dams; the corresponding relationship between the safety level of the debris flow control project and the grade of the debris flow retaining structure buildings is as follows: Safety Level I corresponds to Grade I buildings, Safety Level II corresponds to Grade II buildings, Safety Level III corresponds to Grade III buildings, and Safety Level IV corresponds to Grade IV buildings;

[0040] S4. Select the construction location of the single-stage flexible debris flow retaining structure in combination with the terrain and geological conditions of the debris flow gully;

[0041] S5. Determine the structural parameters of the single-stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow retaining structure;

[0042] The structural parameters of the single-stage flexible debris flow retaining structure include the vertical height H of the retaining net, the inclination angle A of the retaining net, and the horizontal length L of the retaining net;

[0043] The ratio of the vertical height H of the retaining net to the maximum particle size D of the debris flow is (1.5 - 2):1;

[0044] The inclination angle A of the retaining net and the horizontal length L of the retaining net in the structural parameters of the single-stage flexible debris flow retaining structure are obtained through the following steps:

[0045] A1. Determine the preliminary inclination angle A0 of the retaining net in combination with the internal friction angle ф of the debris flow deposits, the cohesion C of the debris flow deposits, and design experience. Obtain the set solid object retaining volume V0 in combination with the terrain and geological conditions of the debris flow gully, the construction location of the single-stage flexible debris flow retaining structure, the debris flow flood volume v, the debris flow occurrence frequency, and the grade of the debris flow retaining structure buildings;

[0046] A2. Obtain the theoretical horizontal length L0 of the retaining net and the designed length L1 of the retaining net interception allowance in combination with the construction location of the single-stage flexible debris flow retaining structure, the terrain and geological conditions of the debris flow gully, the vertical height H of the retaining net, the preliminary inclination angle A0 of the retaining net, and the set solid object retaining volume V0;

[0047] A3. Add the theoretical horizontal length L0 of the retaining net and the designed length L1 of the retaining net interception allowance to obtain the preliminary horizontal length L2 of the retaining net;

[0048] A4. Calculate the safety factor of the accumulation body under the control condition according to the rigid body limit equilibrium method. The value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is not less than 0 and not greater than 0.2. The inclination angle A of the retaining net is taken as the preliminary inclination angle A0 of the retaining net, and the horizontal length L of the retaining net is taken as the preliminary horizontal length L2 of the retaining net. If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is less than 0 or greater than 0.2, adjust the preliminary inclination angle A0 of the retaining net.

[0049] If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is less than 0, it means that the safety factor of the accumulation body under the control condition does not meet the requirements of the design code for rolled earth-rock dams, and the preliminary inclination angle A0 of the retaining net should be reduced. If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is greater than 0.2, it means that the safety margin of the design scheme is large and the economy is low, and the preliminary inclination angle A0 of the retaining net should be increased.

[0050] The safety factor of the accumulation body under the control condition is calculated according to the analysis method of dam slope stability calculation in the design code for rolled earth-rock dams SL274 or the design code for rolled earth-rock dams NB / T10872 and by using the rigid body limit equilibrium method to calculate the safety factor of the accumulation body under normal operation conditions, extraordinary operation conditions I, and extraordinary operation conditions II respectively. The safety factor of the accumulation body under normal operation conditions is the safety factor of the accumulation body under normal operation conditions, the safety factor of the accumulation body under extraordinary operation conditions I is the safety factor of the accumulation body under rainstorm conditions, and the safety factor of the accumulation body under extraordinary operation conditions II is the safety factor of the accumulation body under earthquake conditions.

[0051] S6. Establish a single-stage flexible debris flow retaining structure based on the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and the single-stage prevention work is completed.

[0052] S7. According to the siltation situation inside the single-stage flexible debris flow retaining structure, continue to establish a single-stage flexible debris flow retaining structure upstream of it to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention work is completed.

[0053] When the terrain of the debris flow channel and the objects threatened by the debris flow disaster remain unchanged and the accumulated amount of solids in the established single-stage flexible debris flow retaining structure reaches the set solid retaining amount, or the distance between the siltation surface in front of the retaining net and the top of the retaining net is 0.5 m - 1.0 m, repeat steps S4 - S6 to continue establishing a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure, obtaining a multi-stage flexible debris flow retaining structure, and completing the multi-stage prevention and control work; if the terrain of the debris flow channel and the objects threatened by the debris flow disaster change and the accumulated amount of solids in the established single-stage flexible debris flow retaining structure reaches the set solid retaining amount, or the distance between the siltation surface in front of the retaining net and the top of the retaining net is 0.5 m - 1.0 m, repeat steps S1 - S6 to continue establishing a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure, obtaining a multi-stage flexible debris flow retaining structure, and completing the multi-stage prevention and control work.

[0054] Example 1

[0055] This example proposes a multi-stage stacked retaining prevention and control method for debris flows, including the following steps:

[0056] S1. Obtain the terrain of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the objects threatened by the debris flow disaster within the debris flow prevention and control area;

[0057] S2. Determine the safety level of the debris flow prevention and control project based on the objects threatened by the debris flow disaster;

[0058] S3. Determine the building level of the debris flow retaining structure based on the safety level of the debris flow prevention and control project;

[0059] S4. Select the construction location of the single-stage flexible debris flow retaining structure in combination with the terrain of the debris flow channel and the geological conditions of the channel;

[0060] S5. Determine the structural parameters of the single-stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow retaining structure;

[0061] S6. Establish a single-stage flexible debris flow retaining structure based on the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and complete the single-stage prevention and control work;

[0062] S7. According to the siltation situation in the single-stage flexible debris flow retaining structure, continue to establish a single-stage flexible debris flow retaining structure upstream of it to obtain a multi-stage flexible debris flow retaining structure, and complete the multi-stage prevention and control work;

[0063] When there are changes in the terrain of the debris flow channel and the objects threatened by the debris flow disaster, and the distance between the siltation surface in front of the retaining net and the top of the retaining net in the established single-stage flexible debris flow retaining structure is 1.0 m, repeat steps S1 - S6 to continue building a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure, obtaining a multi-stage flexible debris flow retaining structure, and completing the multi-stage prevention and control work.

[0064] Embodiment 2

[0065] This embodiment proposes a multi-stage stacked retaining prevention and control method for debris flows, including the following steps:

[0066] S1. Obtain the terrain of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the objects threatened by the debris flow disaster within the debris flow prevention and control area;

[0067] The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris flow deposit, and the cohesion C of the debris flow deposit;

[0068] S2. Determine the safety level of the debris flow prevention and control project based on the objects threatened by the debris flow disaster;

[0069] The safety level of the debris flow prevention and control project is determined by combining the objects threatened by the debris flow disaster with the design specifications of the debris flow prevention and control project; the safety levels of the debris flow prevention and control project include safety level I, safety level II, safety level III, and safety level IV;

[0070] S3. Determine the building level of the debris flow retaining structure based on the safety level of the debris flow prevention and control project;

[0071] The building level of the debris flow retaining structure is determined by combining the safety level of the debris flow prevention and control project with the safety level information in the design specifications of the debris flow prevention and control project and the building level information in the design specifications of the rolled earth-rock dam; the corresponding relationship between the safety level of the debris flow prevention and control project and the building level of the debris flow retaining structure is as follows: safety level I corresponds to grade I buildings, safety level II corresponds to grade II buildings, safety level III corresponds to grade III buildings, and safety level IV corresponds to grade IV buildings;

[0072] S4. Select the construction location of the single-stage flexible debris flow retaining structure in combination with the terrain of the debris flow channel and the geological conditions of the channel;

[0073] S5. Determine the structural parameters of the single-stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow retaining structure;

[0074] S6. Build a single-stage flexible debris flow retaining structure based on the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and complete the single-stage prevention and control work;

[0075] S7. According to the siltation situation inside the single - stage flexible debris flow retaining structure, continue to build a single - stage flexible debris flow retaining structure upstream of it to obtain a multi - stage flexible debris flow retaining structure, and the multi - stage prevention and control work is completed.

[0076] When the terrain of the debris flow channel and the threat objects of the debris flow disaster situation change and the distance between the siltation surface in front of the retaining net and the top of the retaining net in the already built single - stage flexible debris flow retaining structure is 0.5 m, repeat steps S1 - S6 to continue building a single - stage flexible debris flow retaining structure upstream of the already built single - stage flexible debris flow retaining structure to obtain a multi - stage flexible debris flow retaining structure, and the multi - stage prevention and control work is completed.

[0077] Embodiment 3

[0078] This embodiment proposes a multi - stage stacked retaining prevention and control method for debris flows, including the following steps:

[0079] S1. Obtain the terrain of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the threat objects of the debris flow disaster situation within the debris flow prevention and control area.

[0080] The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris flow deposit, and the cohesion C of the debris flow deposit.

[0081] S2. Determine the safety level of the debris flow prevention and control project based on the threat objects of the debris flow disaster situation.

[0082] The safety level of the debris flow prevention and control project is determined by combining the threat objects of the debris flow disaster situation with the design specifications of the debris flow prevention and control project; the safety levels of the debris flow prevention and control project include safety level one, safety level two, safety level three, and safety level four.

[0083] S3. Determine the building grade of the debris flow retaining structure based on the safety level of the debris flow prevention and control project.

[0084] The building grade of the debris flow retaining structure is determined by combining the safety level of the debris flow prevention and control project with the safety level information in the design specifications of the debris flow prevention and control project and the building grade information in the design specifications of rolled - fill earth dams; the corresponding relationship between the safety level of the debris flow prevention and control project and the building grade of the debris flow retaining structure is as follows: safety level one corresponds to grade - one buildings, safety level two corresponds to grade - two buildings, safety level three corresponds to grade - three buildings, and safety level four corresponds to grade - four buildings.

[0085] S4. Select the construction location of the single - stage flexible debris flow retaining structure in combination with the terrain of the debris flow channel and the geological conditions of the channel.

[0086] S5. Determine the structural parameters of the single - stage flexible debris - flow retaining structure by combining the main parameters of the debris flow and the construction location of the single - stage flexible debris - flow retaining structure;

[0087] The structural parameters of the single - stage flexible debris - flow retaining structure include the vertical height H of the retaining net, the inclination angle A of the retaining net, and the horizontal length L of the retaining net;

[0088] The ratio of the vertical height H of the retaining net to the maximum particle size D of the debris flow is 1.5:1;

[0089] S6. Establish a single - stage flexible debris - flow retaining structure based on the structural parameters and construction location of the single - stage flexible debris - flow retaining structure, and the single - stage prevention work is completed;

[0090] S7. According to the siltation situation inside the single - stage flexible debris - flow retaining structure, continue to build a single - stage flexible debris - flow retaining structure upstream of it to obtain a multi - stage flexible debris - flow retaining structure, and the multi - stage prevention work is completed;

[0091] When the terrain of the debris - flow channel and the threatened objects of the debris - flow disaster situation change and the accumulated amount of solids in the established single - stage flexible debris - flow retaining structure reaches the set solid - retaining amount, repeat steps S1 - S6 to continue building a single - stage flexible debris - flow retaining structure upstream of the established single - stage flexible debris - flow retaining structure to obtain a multi - stage flexible debris - flow retaining structure, and the multi - stage prevention work is completed.

[0092] Embodiment 4

[0093] This embodiment proposes a multi - stage stacked retaining prevention method for debris flows, including the following steps:

[0094] S1. Obtain the terrain of the debris - flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the threatened objects of the debris - flow disaster situation within the debris - flow prevention area;

[0095] The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris - flow deposit, and the cohesion C of the debris - flow deposit;

[0096] S2. Determine the safety level of the debris - flow prevention project according to the threatened objects of the debris - flow disaster situation;

[0097] The safety level of the debris - flow prevention project is determined by combining the threatened objects of the debris - flow disaster situation with the design specifications of the debris - flow prevention project; the safety levels of the debris - flow prevention project include Safety Level 1, Safety Level 2, Safety Level 3, and Safety Level 4;

[0098] S3. Determine the building grade of the debris - flow retaining structure according to the safety level of the debris - flow prevention project;

[0099] The grade of the debris flow retaining structure building is determined based on the safety grade of the debris flow prevention project, combined with the safety grade information in the Design Code for Debris Flow Prevention Engineering and the building grade information in the Design Code for Rolled Earth-Rock Dams; the corresponding relationship between the safety grade of the debris flow prevention project and the grade of the debris flow retaining structure building is as follows: the first-level safety grade corresponds to the first-level building, the second-level safety grade corresponds to the second-level building, the third-level safety grade corresponds to the third-level building, and the fourth-level safety grade corresponds to the fourth-level building;

[0100] S4. Select the construction location of the single-stage flexible debris flow retaining structure in combination with the topography and geological conditions of the debris flow channel;

[0101] S5. Determine the structural parameters of the single-stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow retaining structure;

[0102] The structural parameters of the single-stage flexible debris flow retaining structure include the vertical height H of the retaining net, the inclination angle A of the retaining net, and the horizontal length L of the retaining net;

[0103] The ratio of the vertical height H of the retaining net to the maximum particle size D of the debris flow is 1.75:1;

[0104] In the structural parameters of the single-stage flexible debris flow retaining structure, the inclination angle A of the retaining net and the horizontal length L of the retaining net are obtained through the following steps:

[0105] A1. Determine the preliminary inclination angle A0 of the retaining net in combination with the internal friction angle ф of the debris flow deposit, the cohesion C of the debris flow deposit, and design experience. Obtain the set solid retaining volume V0 in combination with the topography and geological conditions of the debris flow channel, the construction location of the single-stage flexible debris flow retaining structure, the debris flow flood volume v, the debris flow occurrence frequency, and the grade of the debris flow retaining structure building;

[0106] A2. Obtain the theoretical horizontal length L0 of the retaining net and the designed length L1 of the retaining margin of the retaining net in combination with the construction location of the single-stage flexible debris flow retaining structure, the topography and geological conditions of the debris flow channel, the vertical height H of the retaining net, the preliminary inclination angle A0 of the retaining net, and the set solid retaining volume V0;

[0107] A3. Add the theoretical horizontal length L0 of the retaining net and the designed length L1 of the retaining margin of the retaining net to obtain the preliminary horizontal length L2 of the retaining net;

[0108] A4. Calculate the safety factor of the control condition accumulation body according to the rigid body limit equilibrium method. The value obtained by subtracting the safety factor required by the Design Code for Rolled Earth-Rock Dams from the safety factor of the control condition accumulation body is not less than 0 and not greater than 0.2. The inclination angle A of the retaining net is taken as the preliminary inclination angle A0 of the retaining net, and the horizontal length L of the retaining net is taken as the preliminary horizontal length L2 of the retaining net;

[0109] S6. Establish a single-stage flexible debris flow retaining structure based on the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and the single-stage prevention and control work is completed;

[0110] S7. According to the siltation situation inside the single-stage flexible debris flow retaining structure, continue to establish a single-stage flexible debris flow retaining structure upstream of it to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed;

[0111] When the terrain of the debris flow channel and the threat objects of the debris flow disaster situation remain unchanged and the distance between the siltation surface in front of the retaining net and the top of the retaining net in the established single-stage flexible debris flow retaining structure is 1.0 m, repeat steps S4 - S6 to continue to establish a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

[0112] Embodiment 5

[0113] This embodiment proposes a multi-stage cascade retaining prevention and control method for debris flows, including the following steps:

[0114] S1. Obtain the terrain of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the threat objects of the debris flow disaster situation within the debris flow prevention and control area;

[0115] The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris flow deposit, and the cohesion C of the debris flow deposit;

[0116] S2. Determine the safety level of the debris flow prevention and control project based on the threat objects of the debris flow disaster situation;

[0117] The safety level of the debris flow prevention and control project is determined based on the threat objects of the debris flow disaster situation in combination with the design specifications of the debris flow prevention and control project; the safety levels of the debris flow prevention and control project include safety level I, safety level II, safety level III, and safety level IV;

[0118] S3. Determine the building grade of the debris flow retaining structure based on the safety level of the debris flow prevention and control project;

[0119] The building grade of the debris flow retaining structure is determined based on the safety level of the debris flow prevention and control project in combination with the safety level information in the design specifications of the debris flow prevention and control project and the building grade information in the design specifications of rolled earth-rock dams; the corresponding relationship between the safety level of the debris flow prevention and control project and the building grade of the debris flow retaining structure is as follows: safety level I corresponds to grade I buildings, safety level II corresponds to grade II buildings, safety level III corresponds to grade III buildings, and safety level IV corresponds to grade IV buildings;

[0120] S4. Select the construction location of the single - stage flexible debris flow retaining structure in combination with the terrain and geological conditions of the debris flow channel;

[0121] S5. Determine the structural parameters of the single - stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single - stage flexible debris flow retaining structure;

[0122] The structural parameters of the single - stage flexible debris flow retaining structure include the vertical height H of the retaining net, the inclination angle A of the retaining net, and the horizontal length L of the retaining net;

[0123] The ratio of the vertical height H of the retaining net to the maximum particle size D of the debris flow is 1.5:1;

[0124] In the structural parameters of the single - stage flexible debris flow retaining structure, the inclination angle A of the retaining net and the horizontal length L of the retaining net are obtained through the following steps:

[0125] A1. Determine the preliminary inclination angle A0 of the retaining net in combination with the internal friction angle ф of the debris flow deposit, the cohesion C of the debris flow deposit, and design experience. Obtain the set solid retaining volume V0 in combination with the terrain and geological conditions of the debris flow channel, the construction location of the single - stage flexible debris flow retaining structure, the debris flow flood volume v, the debris flow occurrence frequency, and the building grade of the debris flow retaining structure;

[0126] A2. Obtain the theoretical horizontal length L0 of the retaining net and the design length L1 of the intercepting margin of the retaining net in combination with the construction location of the single - stage flexible debris flow retaining structure, the terrain and geological conditions of the debris flow channel, the vertical height H of the retaining net, the preliminary inclination angle A0 of the retaining net, and the set solid retaining volume V0;

[0127] A3. Add the theoretical horizontal length L0 of the retaining net and the design length L1 of the intercepting margin of the retaining net to obtain the preliminary horizontal length L2 of the retaining net;

[0128] A4. Calculate the safety factor of the control - condition accumulation body according to the rigid - body limit equilibrium method. The value obtained by subtracting the safety factor required by the design code for rolled - earth and rock dams from the safety factor of the control - condition accumulation body is not less than 0 and not greater than 0.2. The inclination angle A of the retaining net takes the value of the preliminary inclination angle A0 of the retaining net, and the horizontal length L of the retaining net takes the value of the preliminary horizontal length L2 of the retaining net; if the value obtained by subtracting the safety factor required by the design code for rolled - earth and rock dams from the safety factor of the control - condition accumulation body is less than 0 or greater than 0.2, adjust the preliminary inclination angle A0 of the retaining net;

[0129] If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is less than 0, it means that the safety factor of the accumulation body under the control condition does not meet the requirements of the design code for rolled earth-rock dams, and the initially proposed inclination angle A0 of the retaining net is reduced; if the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulation body under the control condition is greater than 0.2, it means that the safety margin of the design scheme is large and the economy is low, and the initially proposed inclination angle A0 of the retaining net is increased.

[0130] S6. Establish a single-stage flexible debris flow retaining structure based on the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and the single-stage prevention and control work is completed.

[0131] S7. According to the siltation situation inside the single-stage flexible debris flow retaining structure, continue to establish a single-stage flexible debris flow retaining structure upstream of it to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

[0132] When the terrain of the debris flow channel and the threat objects of the debris flow disaster situation remain unchanged and the distance between the siltation surface in front of the retaining net and the top of the retaining net in the established single-stage flexible debris flow retaining structure is 0.5 m, repeat steps S4 - S6 to continue establishing a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

[0133] Embodiment 6

[0134] This embodiment proposes a multi-stage stacked retaining prevention and control method for debris flows, including the following steps:

[0135] S1. Obtain the terrain of the debris flow channel, the geological conditions of the channel, the main parameters of the debris flow, and the threat objects of the debris flow disaster situation within the debris flow prevention and control area.

[0136] The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris flow accumulation, and the cohesion C of the debris flow accumulation.

[0137] S2. Determine the safety level of the debris flow prevention and control project based on the threat objects of the debris flow disaster situation.

[0138] The safety level of the debris flow prevention and control project is determined based on the threat objects of the debris flow disaster situation in combination with the design code for the debris flow prevention and control project; the safety levels of the debris flow prevention and control project include safety level I, safety level II, safety level III, and safety level IV.

[0139] S3. Determine the building grade of the debris flow retaining structure based on the safety level of the debris flow prevention and control project.

[0140] The grade of the debris flow retaining structure building is determined based on the safety grade of the debris flow prevention project, combined with the safety grade information in the design code for debris flow prevention projects and the building grade information in the design code for rolled earth-rock dams; the corresponding relationship between the safety grade of the debris flow prevention project and the grade of the debris flow retaining structure building is as follows: the first-level safety grade corresponds to the first-level building, the second-level safety grade corresponds to the second-level building, the third-level safety grade corresponds to the third-level building, and the fourth-level safety grade corresponds to the fourth-level building;

[0141] S4. Select the construction location of the single-stage flexible debris flow retaining structure in combination with the topography and geological conditions of the debris flow channel;

[0142] S5. Determine the structural parameters of the single-stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow retaining structure;

[0143] The structural parameters of the single-stage flexible debris flow retaining structure include the vertical height H of the retaining net, the inclination angle A of the retaining net, and the horizontal length L of the retaining net;

[0144] The ratio of the vertical height H of the retaining net to the maximum particle size D of the debris flow is 2:1;

[0145] Among the structural parameters of the single-stage flexible debris flow retaining structure, the inclination angle A of the retaining net and the horizontal length L of the retaining net are obtained through the following steps:

[0146] A1. Determine the preliminary inclination angle A0 of the retaining net in combination with the internal friction angle ф of the debris flow deposit, the cohesion C of the debris flow deposit, and design experience. Obtain the set solid retaining volume V0 in combination with the topography and geological conditions of the debris flow channel, the construction location of the single-stage flexible debris flow retaining structure, the debris flow flood volume v, the debris flow occurrence frequency, and the grade of the debris flow retaining structure building;

[0147] A2. Obtain the theoretical horizontal length L0 of the retaining net and the designed length L1 of the retaining margin of the retaining net in combination with the construction location of the single-stage flexible debris flow retaining structure, the topography and geological conditions of the debris flow channel, the vertical height H of the retaining net, the preliminary inclination angle A0 of the retaining net, and the set solid retaining volume V0;

[0148] A3. Add the theoretical horizontal length L0 of the retaining net and the designed length L1 of the retaining margin of the retaining net to obtain the preliminary horizontal length L2 of the retaining net;

[0149] A4. Calculate the safety factor of the accumulated body under the control condition according to the rigid body limit equilibrium method. The value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulated body under the control condition is not less than 0 and not more than 0.2. The inclination angle A of the retaining net is taken as the initial inclination angle A0 of the retaining net, and the horizontal length L of the retaining net is taken as the initial horizontal length L2 of the retaining net. If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulated body under the control condition is less than 0 or greater than 0.2, adjust the initial inclination angle A0 of the retaining net.

[0150] If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulated body under the control condition is less than 0, it means that the safety factor of the accumulated body under the control condition does not meet the requirements of the design code for rolled earth-rock dams, and the initial inclination angle A0 of the retaining net should be reduced. If the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the accumulated body under the control condition is greater than 0.2, it means that the safety margin of the design scheme is large and the economy is low, and the initial inclination angle A0 of the retaining net should be increased.

[0151] Calculate the safety factor of the accumulated body under the control condition according to the calculation analysis method of dam slope stability in the design code for rolled earth-rock dams SL274 or the design code for rolled earth-rock dams NB / T10872 and use the rigid body limit equilibrium method to calculate the safety factor of the accumulated body under normal operation conditions, extraordinary operation conditions I, and extraordinary operation conditions II respectively. The safety factor of the accumulated body under normal operation conditions is the safety factor of the accumulated body under normal operation conditions, the safety factor of the accumulated body under extraordinary operation conditions I is the safety factor of the accumulated body under rainstorm conditions, and the safety factor of the accumulated body under extraordinary operation conditions II is the safety factor of the accumulated body under earthquake conditions.

[0152] S6. Establish a single-stage flexible debris flow retaining structure based on the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and the single-stage prevention and control work is completed.

[0153] S7. According to the siltation situation inside the single-stage flexible debris flow retaining structure, continue to establish a single-stage flexible debris flow retaining structure upstream of it to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

[0154] When the terrain of the debris flow channel and the threat objects of the debris flow disaster situation remain unchanged and the accumulated amount of solids in the established single-stage flexible debris flow retaining structure reaches the set solid retention amount, repeat steps S4 - S6 to continue to establish a single-stage flexible debris flow retaining structure upstream of the established single-stage flexible debris flow retaining structure to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

[0155] The multi-stage flexible debris flow retaining structure in the embodiment of the present invention, as Figure 2 shown, includes three single-stage flexible debris flow retaining structures 9 arranged in sequence along the debris flow flow direction, as Figure 3As shown in the figure, the single - stage flexible debris flow retaining structure 9 includes a second fixed spread foundation 3. The second fixed spread foundation 3 is embedded in the ground 5. On both sides of the second fixed spread foundation 3, a first fixed spread foundation 2 and a third fixed spread foundation 4 are respectively embedded in the ground 5. A first support mechanism 6 is fixedly connected to the first fixed spread foundation 2. A second support mechanism 7 is fixedly connected to the second fixed spread foundation 3. A bottom fixing mechanism 8 is fixedly connected to the third fixed spread foundation 4. One end of a retaining net 1 is fixedly connected to the bottom fixing mechanism 8, and the other end of the retaining net 1 is fixedly connected to the first support mechanism 6.

[0156] The second support mechanism 7 is located between the first support mechanism 6 and the bottom fixing mechanism 8, and the second support mechanism 7 is fixedly connected to the retaining net 1. The absolute elevation of the first fixed spread foundation 2 is greater than the absolute elevation of the second fixed spread foundation 3, and the absolute elevation of the second fixed spread foundation 3 is greater than the absolute elevation of the third fixed spread foundation 4. One end of the bottom fixing mechanism 8 is fixedly connected and embedded in the third fixed spread foundation 4, and the other end is fixedly connected to one end of the retaining net 1.

[0157] The difference in absolute elevation between the end of the retaining net 1 where the bottom fixing mechanism 8 is fixed and the outer wall of the side of the third fixed spread foundation 4 where the bottom fixing mechanism 8 is arranged is the vertical height H of the retaining net. The angle between the retaining net 1 and the horizontal plane is the inclination angle A of the retaining net. The projected length of the retaining net 1 on the horizontal plane is the horizontal length L of the retaining net.

[0158] In the present invention, the retaining net 1 intercepts the debris flow solids carried in the debris flow and discharges the water to the downstream. By adjusting the inclination angle of the retaining net, the self - stability of the debris flow solid accumulation is achieved. The set solid interception amount reserves a large safety margin, ensuring the safety and reliability of the interception measures. If the solid accumulation amount in the single - stage flexible debris flow retaining structure reaches the set solid interception amount, a single - stage flexible debris flow retaining structure can be built again upstream of the original single - stage flexible debris flow retaining structure to form a multi - stage retaining structure. The single - stage flexible debris flow retaining structure has the advantages of simple structure, flexible layout, and avoiding silt cleaning. The single - stage flexible debris flow retaining structure in the present invention can be adjusted according to actual needs to adapt to the on - site environment.

[0159] In the present invention, if the vertical height of the retaining net is too small, there will be an overhead phenomenon under the retaining net. If it is too large, it will affect the self - stability of the debris flow accumulation. Therefore, its value needs to be determined by referring to the particle size of the debris flow solids. Appropriately setting the inclination angle of the retaining net can ensure that after the debris flow occurs, under the protection of the retaining net 1, the sediment in the retaining net 1 is in a stable state. The flexible single - stage debris flow retaining structure should be built at a relatively flat location with good bedrock conditions.

[0160] The retaining net 1 is mainly used to intercept the solid substances in the debris flow and drain the water to the downstream; the first support mechanism 6 and the second support mechanism 7 are rigid support structures, which mainly play the role of fixing the retaining net 1, and their strength can withstand the weight of the retaining net 1 itself and the impact of the debris flow; as Figure 2 shown, if the accumulation amount of solid substances in the single-stage flexible debris flow retaining structure reaches the set solid substance retaining amount, a single-stage flexible debris flow retaining structure can be set again upstream, so as to form a multi-stage flexible debris flow retaining structure as a whole. Each single-stage flexible debris flow retaining structure intercepts the upstream debris flow through the retaining net 1, drains the water in the debris flow to the downstream, and the solid substances in the net form a self-stable state. When the debris flow comes, the retaining structure mainly plays the role of intercepting the debris flow; after the debris flow occurs, the retaining net only plays the role of safety reserve, and the accumulated substances in the net can reach a self-stable state.

Claims

1. Method for preventing and controlling debris flow by multi-level cascade barrier, characterized in that, It includes the following steps: S1. Obtain the terrain of the debris flow gully, the geological conditions of the gully, the main parameters of the debris flow, and the objects threatened by the debris flow disaster in the debris flow prevention and control area; The main parameters of the debris flow include the maximum particle size D of the debris flow, the flood volume v of the debris flow, the occurrence frequency of the debris flow, the specific gravity γ of the debris flow, the internal friction angle ф of the debris flow deposit, and the cohesion C of the debris flow deposit; S2. Determine the safety level of the debris flow prevention and control project based on the objects threatened by the debris flow disaster; S3. Determine the grade of the debris flow retaining structure building according to the safety level of the debris flow prevention and control project; S4. Select the construction location of the single-stage flexible debris flow retaining structure in combination with the terrain of the debris flow gully and the geological conditions of the gully; S5. Determine the structural parameters of the single-stage flexible debris flow retaining structure in combination with the main parameters of the debris flow and the construction location of the single-stage flexible debris flow retaining structure; The inclination angle A and the horizontal length L of the retaining net in the structural parameters of the single-stage flexible debris flow retaining structure are obtained through the following steps: A1. Determine the preliminary inclination angle A0 of the retaining net in combination with the internal friction angle ф of the debris flow deposit, the cohesion C of the debris flow deposit and the design experience, and obtain the set solid retaining volume V0 in combination with the terrain of the debris flow gully and the geological conditions of the gully, the construction location of the single-stage flexible debris flow retaining structure, the flood volume v of the debris flow, the occurrence frequency of the debris flow and the grade of the debris flow retaining structure building; A2. Obtain the theoretical horizontal length L0 of the retaining net and the designed length L1 of the intercepting surplus of the retaining net in combination with the construction location of the single-stage flexible debris flow retaining structure, the terrain and geological conditions of the debris flow gully, the vertical height H of the retaining net, the preliminary inclination angle A0 of the retaining net and the set solid retaining volume V0; A3. Add the theoretical horizontal length L0 of the retaining net and the designed length L1 of the intercepting surplus of the retaining net to obtain the preliminary horizontal length L2 of the retaining net; A4. Calculate the safety factor of the control condition accumulation body according to the rigid body limit equilibrium method. The value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the control condition accumulation body is not less than 0 and not greater than 0.

2. The inclination angle A of the retaining net is taken as the preliminary inclination angle A0 of the retaining net, and the horizontal length L of the retaining net is taken as the preliminary horizontal length L2 of the retaining net; if the value obtained by subtracting the safety factor required by the design code for rolled earth-rock dams from the safety factor of the control condition accumulation body is less than 0 or greater than 0.2, adjust the preliminary inclination angle A0 of the retaining net; S6. Establish a single-stage flexible debris flow retaining structure according to the structural parameters and construction location of the single-stage flexible debris flow retaining structure, and the single-stage prevention and control work is completed; S7. According to the siltation situation in the single-stage flexible debris flow retaining structure, continue to establish a single-stage flexible debris flow retaining structure upstream of it to obtain a multi-stage flexible debris flow retaining structure, and the multi-stage prevention and control work is completed.

2. The debris flow multi-stage stacked retaining prevention and control method according to claim 1, wherein The safety level of the debris flow prevention and control project is determined in combination with the objects threatened by the debris flow disaster according to the design code for debris flow prevention and control projects; the safety levels of the debris flow prevention and control projects include safety level I, safety level II, safety level III, and safety level IV.

3. The debris flow multi-stage stacked retaining prevention and control method according to claim 2, wherein The building grade of the debris flow blocking structure is determined based on the safety grade of the debris flow prevention project, combined with the safety grade information in the Design Code for Debris Flow Prevention Projects and the building grade information in the Design Code for Rolled Earth-Rock Dams; the corresponding relationship between the safety grade of the debris flow prevention project and the building grade of the debris flow blocking structure is as follows: safety grade I corresponds to grade I buildings, safety grade II corresponds to grade II buildings, safety grade III corresponds to grade III buildings, and safety grade IV corresponds to grade IV buildings.

4. The debris flow multi-level cascade retaining and control method according to claim 3, characterized in that The structural parameters of the single-stage flexible debris flow blocking structure include the vertical height H of the blocking net, the inclination angle A of the blocking net, and the horizontal length L of the blocking net. The ratio of the vertical height H of the blocking net to the maximum particle size D of the debris flow is (1.5 - 2):

1.

5. The debris flow multi-stage cascade retaining prevention and control method according to claim 4, characterized in that If the value obtained by subtracting the safety factor required by the Design Code for Rolled Earth-Rock Dams from the safety factor of the accumulation body under the control condition is less than 0, then the safety factor of the accumulation body under the control condition does not meet the requirements of the Design Code for Rolled Earth-Rock Dams, and the initially assumed inclination angle A0 of the blocking net is reduced; if the value obtained by subtracting the safety factor required by the Design Code for Rolled Earth-Rock Dams from the safety factor of the accumulation body under the control condition is greater than 0.2, then the safety margin of the design scheme is large and the economy is low, and the initially assumed inclination angle A0 of the blocking net is increased.

6. The multi - level stacked retaining prevention and control method for debris flow according to claim 5, wherein, The safety factor of the accumulation body under the control condition is calculated respectively for the normal operation condition, the extraordinary operation condition I, and the extraordinary operation condition II by using the rigid body limit equilibrium method according to the method for calculating and analyzing the stability of the dam slope in the Design Code for Rolled Earth-Rock Dams SL274 or the Design Code for Rolled Earth-Rock Dams NB / T10872. The safety factor of the accumulation body under the normal operation condition is the safety factor of the accumulation body under the normal operation condition, the safety factor of the accumulation body under the extraordinary operation condition I is the safety factor of the accumulation body under the rainstorm condition, and the safety factor of the accumulation body under the extraordinary operation condition II is the safety factor of the accumulation body under the earthquake condition.

7. The debris flow multi-level stacked retaining prevention and control method according to any one of claims 1-6, characterized in that Specifically, when the terrain of the debris flow channel and the threatened objects of the debris flow disaster situation remain unchanged and the solid matter accumulation amount in the established single-stage flexible debris flow blocking structure reaches the set solid matter blocking amount or the distance between the siltation surface in front of the blocking net and the top of the blocking net is 0.5 m - 1.0 m, repeat steps S4 - S6 to continue building a single-stage flexible debris flow blocking structure upstream of the established single-stage flexible debris flow blocking structure to obtain a multi-stage flexible debris flow blocking structure, and the multi-stage prevention and control work is completed; if the terrain of the debris flow channel and the threatened objects of the debris flow disaster situation change and the solid matter accumulation amount in the established single-stage flexible debris flow blocking structure reaches the set solid matter blocking amount or the distance between the siltation surface in front of the blocking net and the top of the blocking net is 0.5 m - 1.0 m, repeat steps S1 - S6 to continue building a single-stage flexible debris flow blocking structure upstream of the established single-stage flexible debris flow blocking structure to obtain a multi-stage flexible debris flow blocking structure, and the multi-stage prevention and control work is completed.

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