Mine underground debris flow risk quantitative analysis and evaluation method

Abstract

The application discloses a kind of mine underground debris flow risk quantitative analysis and evaluation method, belong to metal mine disaster prevention technical field.It includes calculating the 24 hours rainfall under different storm frequency;Determine the sand critical hydraulic gradient, collapse sand critical hydraulic gradient, calculate sand water level height, collapse sand water level height;Calculate the upper boundary storm infiltration of quaternary sand and gravel layer under the most unfavorable condition, calculate the sand storm leakage and collapse sand storm leakage of the lower boundary of quaternary sand and gravel layer;Compare the leakage and infiltration, preliminary determine sand or collapse sand risk, calculate the time required for water level to rise to sand water level height or collapse sand water level height, finally determine sand or collapse sand risk;Using the same method to analyze the sand, collapse sand risk under short-time heavy rainfall condition.The application realizes quantitative analysis of underground debris flow risk under different rainfall intensity, can determine the disaster trigger mechanism, give the critical criterion of mine underground debris flow formation, provide prevention and control decision basis.

Description

Technical Field

[0001] This invention belongs to the field of metal mine disaster prevention and control technology, and specifically relates to a method for quantitative analysis and evaluation of debris flow risk in underground mines. Background Technology

[0002] Mineral resources are the core strategic resources for national industrial development. With the increasing depletion of shallow resources, the mining depth of underground mines is constantly increasing. Due to its advantages of low cost and high efficiency, the caving method has become the mainstream mining method for underground metal mines (such as Chengchao Iron Mine and Pulang Copper Mine) and some coal mines.

[0003] However, while natural caving is a highly efficient underground mining method, its implementation severely disturbs the geological structure of the mining area, easily triggering large-scale surface collapses and violent fracturing of the overlying rock mass, fundamentally disrupting the static and hydrogeological balance of the original rock. Particularly serious is the fact that during the rainy season, abundant rainfall mixes with loose surface deposits (such as loess and glacial till) generated by the collapse, creating a rich source of material. Driven by gravity, this mixture readily migrates rapidly into underground tunnels with high potential energy along dominant channels such as collapse fissures and faults, or directly through the goaf, transforming into highly destructive underground debris flows. Such disasters are characterized by their significant suddenness, high destructiveness, and complex formation mechanisms; their risk evolution process is hidden and difficult to predict, posing a major threat to the safe and efficient production of mines.

[0004] Current research on underground debris flows still faces several challenges: First, at the risk analysis level, although existing studies have identified three basic formation conditions—solid material sources, water channels, and mining disturbances—most findings remain at the qualitative descriptive stage, lacking systematic quantitative indicators and thus failing to provide precise guidance for mine safety. For example, Chinese invention patent application number 202510508060.2 discloses a debris flow prevention method applicable to caving mining, capable of controlling the material source of underground debris flows at their origin, thereby preventing their occurrence. However, this method suffers from large-scale engineering implementation, high costs, and its effectiveness depends on the accuracy of geological exploration and the quality control of grouting processes. Furthermore, it may struggle to form a uniform and effective consolidated body under complex geological conditions. Second, regarding triggering mechanisms and initiation criteria, the mechanical mechanisms and dynamic evolution processes of debris flow initiation remain unclear due to the concealment of underground spaces and the difficulty of observation, severely impacting the accuracy of disaster prediction and the effectiveness of prevention and control measures. From a research perspective, existing work has focused on static analysis, with insufficient research on the transport process and dynamic mechanism after debris flow is initiated. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a quantitative analysis and evaluation method for debris flow risks in mines. This method overcomes the limitations of existing qualitative research, constructs a quantitative analysis model for underground debris flow disasters, clarifies the disaster triggering mechanism and criteria, and develops mature and reliable risk assessment and precise prevention technologies. This provides decision-making basis and methods for the prevention and control of debris flows in mines and the prediction of their occurrence risks.

[0006] To achieve the above objectives, this application provides the following solution:

[0007] A method for quantitative analysis and evaluation of debris flow risk in underground mines, comprising:

[0008] Step 1: Obtain the digital elevation model (DEM) of the study area to determine the conditions for debris flow formation;

[0009] Step 2: Calculate the 24-hour rainfall under different rainstorm frequencies P in the study area;

[0010] Step 3: Determine the thickness L and permeability coefficient K of the Quaternary gravel layer's fine sand layer through sieving and permeability tests; determine the critical hydraulic gradient for sand extrusion through indoor seepage and sand-breaking experiments. Critical hydraulic gradient for sand erosion Then, the sand level height and the sand runoff level height can be calculated.

[0011] Step 4: Calculate the infiltration rate of the upper boundary of the Quaternary gravel layer under the most unfavorable working condition. ;

[0012] Step 5: Calculate the sand-producing rainwater infiltration at the lower boundary of the Quaternary gravel layer. and sandstorm seepage ;

[0013] Step 6: By comparison and and And whether the time required for the water level to rise to the sand discharge level and the sand breach level exceeds 24 hours, to determine whether there is a risk of sand discharge or sand breach under each rainstorm frequency P.

[0014] Step 7: Use the same method to determine whether there is a risk of sand production or sand collapse under the frequency P of each rainstorm under short-term heavy rainfall.

[0015] Furthermore, step 2 specifically involves: querying the historical average 24-hour maximum rainfall within the mining area. Modulus Calculate 24-hour rainfall under different P values. :

[0016] (1).

[0017] Furthermore, in step 3, the particle size distribution of the Quaternary gravel layer in the study area is obtained through particle sieving and permeability testing. The range of solid particle size in the weathered rock layer in the study area is obtained by querying the data. The weathered rock layer particles are regarded as ideal equigranular spherical particles. The range of pore throat and pore belly under cubic arrangement conditions and the range of pore throat under tetrahedral arrangement conditions are calculated respectively. The minimum value among these three range values ​​is taken as the maximum fine particle size that can pass through the overall downward-moving layer. Combined with the particle size distribution of the Quaternary gravel layer, the proportion of solid particles with a particle size smaller than the maximum fine particle size in the Quaternary gravel layer is determined, which is used to determine the amount of material source for debris flow in the well.

[0018] Furthermore, in step 3, the volume percentage of sand in the sand discharge stage and the volume percentage of sand in the sand inrush stage are obtained through indoor seepage and sand inrush experiments, which serve as the basis for the mine to take sand control measures.

[0019] Furthermore, in step 3, the hydraulic gradient is calculated according to the following formula to achieve... and At that time, the water level of the Quaternary gravel layer needs to be raised by a certain height, namely the sand discharge water level and the sand collapse water level:

[0020] (2);

[0021] In the formula, For hydraulic gradient, The height to which the water level rises above the soil layer.

[0022] Furthermore, step 4 specifically involves selecting a single ore-collecting trough within the study area as the most unfavorable working condition, and using rainfall within the subsidence pit in the surface influence area of ​​this single ore-collecting trough as the water source condition. The projected area A of the single ore-collecting trough in the study area and the area of ​​the subsidence area it forms on the surface are then retrieved. Area of ​​the surrounding fracture zone and the rainwater infiltration coefficient in the subsidence area and the infiltration coefficient of rainstorms in the fissure zone The following formula was used to calculate the rainwater infiltration at the upper boundary of the Quaternary gravel layer under different rainstorm frequencies P. :

[0023] (3).

[0024] Furthermore, step 5 specifically includes:

[0025] The following formulas are used to calculate the sand discharge and sand erosion stormwater infiltration at the lower boundary of the Quaternary gravel layer:

[0026] (4);

[0027] (5).

[0028] Furthermore, step 6 specifically involves... , With different p-values Comparison, such as and All greater than If the P-value indicates no risk of sand production or sand collapse, then it is determined that there is no risk of sand production or sand collapse at that P-value. If so, it is preliminarily determined that there is a risk of sand production. If so, it is preliminarily determined that there is a risk of sand production and sand collapse.

[0029] When a preliminary assessment indicates a risk of sand production or sand runoff, calculate the time required for the water level to rise to the corresponding P-value and sand production / sand runoff levels. and ;like , If the rainfall is less than 24 hours, there is a risk of sand outflow or sand collapse; otherwise, there is no risk. Record the frequency P of rainstorms that indicate a risk of sand outflow or sand collapse; monitor the 24-hour rainfall in the mining area in real time. When a rainstorm with a frequency P indicating a risk of sand outflow or sand collapse occurs, it is determined that the mining area is at risk of debris flow.

[0030] Furthermore, calculate using the following formula and :

[0031] (6);

[0032] (7);

[0033] (8);

[0034] In the formula, V is the pore volume within the projected column of a single aggregate ore bin. The porosity is the porosity within the projected column of a single aggregate ore bin.

[0035] Furthermore, step 7 specifically involves repeating steps 2 and 4 to calculate the 6-hour rainfall and the rainwater infiltration at the upper boundary of the Quaternary gravel layer under different rainstorm frequencies P in the study area, and repeating step 6 to analyze the risk of sand production and sand intrusion under different rainstorm frequencies P during short-term heavy rainfall.

[0036] The beneficial effects of this invention are:

[0037] This invention provides a quantitative analysis and evaluation method for debris flow risk in mines, which can overcome the limitations of existing qualitative research, quantify the risk of debris flow in mines, clarify the triggering mechanism and criteria of the disaster, and form a mature and reliable risk assessment and precise prevention and control technology, providing decision-making basis and method for the prevention and control of debris flow in mines and the prediction of occurrence risks. Attached Figure Description

[0038] Figure 1 This is a flowchart of a method for quantitative analysis and evaluation of debris flow risk in underground mines according to the present invention;

[0039] Figure 2 This is a schematic diagram of the indoor seepage and sand-bursting test channel in an embodiment of the present invention; wherein, (a) is a schematic diagram of the indoor “Z”-shaped channel seepage and sand-bursting test, and (b) is a schematic diagram of the cross-crack grid seepage and sand-bursting test.

[0040] Figure 3 This is a schematic diagram illustrating the magnitude of the absorption and leakage of the Quaternary gravel layer based on theoretical calculations in an embodiment of the present invention. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0042] To address some remaining issues in current research on underground debris flows, this invention proposes a quantitative analysis and evaluation method for underground debris flow risk in mines. This method combines indoor seepage and sand-collapse experiments with theoretical calculations, taking into account factors such as the "material source (topography), channel, and water source." This embodiment further illustrates this approach using the collapse area of ​​the Shuangjianshan silver-lead-zinc mine in Inner Mongolia as the study area.

[0043] A quantitative analysis and evaluation method for debris flow risk in underground mines, such as Figure 1 As shown, it includes:

[0044] Step 1: Obtain the surface DEM of the study area, establish a 3D solid model of the Quaternary gravel layer, surrounding rocks, and ore body group, and accurately determine the formation conditions of debris flows, including the direction of water flow, distance between the water source and the mining area, surface undulation, distribution of the Quaternary gravel layer, and fracture channel conditions. Specifically:

[0045] Step 1.1: Based on the site conditions of the mine, a joint surface and underground survey was conducted, and UAV oblique photography technology was used to obtain DEM data of the study area to determine the distribution range of the Quaternary gravel layer, the direction of water flow, the distance between the water source and the mining area, and the surface undulation. Specifically, in this embodiment, the direction of water flow, the distance between the water source and the mining area, and the surface undulation are as follows: the terrain in the area is high in the northwest and low in the southeast, with large topographic relief, which is not conducive to the storage of surface water. The Ganzhiga River flows from west to east 2 km south of the mining area, and there is no obvious catchment basin on the surface.

[0046] Step 1.2: By collecting and reviewing mine geological survey data, combined with borehole database, and using 3D geological modeling software (Rhnio), a 3D solid model of the Quaternary gravel layer, surrounding rock, and ore body group is established.

[0047] Step 2: Calculate the 24-hour rainfall under different rainstorm recurrence periods (i.e., different rainstorm frequencies P) in the study area. Specifically:

[0048] Based on the rainfall statistics data in the "Hydrological Handbook of Inner Mongolia Autonomous Region", the average 24-hour maximum rainfall over the years within the mining area was obtained. The maximum 24-hour rainfall is 60 mm. The coefficient of variation (Cv) for the largest 24-hour rainstorm in history is 0.56, and the coefficient of variation (Cs) is 3.5Cv. The 24-hour rainfall in the study area under different rainstorm return periods (i.e., different rainstorm frequencies P) is calculated using the following formula. :

[0049] (1);

[0050] In the formula: The modulus ratio is obtained by referring to the Pearson Type III curve value table based on the frequency of rainstorm occurrence P, combined with the Cv value and the relationship between Cv and Cs. Specifically, in this embodiment, four different rainstorm occurrence frequencies P were selected, including P=1%, P=2%, P=5% and P=10%. The 24-hour rainstorm amounts under different P values ​​were calculated using formula (1) as 180.42 mm / d (P=1%), 157.44 mm / d (P=2%), 126.96 mm / d (P=5%), and 103.86 mm / d (P=10%).

[0051] Step 3: Samples of the Quaternary gravel layer were collected on-site and subjected to particle sieving and permeability tests to determine the particle size distribution, fine sand layer thickness L, and permeability coefficient K of the Quaternary gravel layer in the study area. The particle size range of the solid particles constituting the main components of the debris flow was also analyzed. Indoor seepage and sand-breaking experiments were conducted to analyze seepage characteristics. The critical hydraulic gradient of the sand was determined based on the two-phase transport characteristics of water and sand and the time-varying relationship curves of water and sand phase flow rates. Critical hydraulic gradient for sand erosion The proportions of sand production and sand runoff are used to calculate the sand production water level and sand runoff water level of the Quaternary gravel layer. Specifically:

[0052] Step 3.1: Sample the Quaternary gravel layer on site and conduct particle sieving and permeability tests to determine the particle size distribution, fine sand layer thickness L and permeability coefficient K of the layer, and analyze the particle size range of the solid particles that make up the main components of the debris flow.

[0053] Specifically, in this embodiment, the permeability coefficient K of the Quaternary gravel layer was measured to be 0.006 cm / s (5.18 m / d) through particle sieving and permeability testing. The particle size distribution of the Quaternary gravel layer was determined to be: the vast majority of particles are less than 10 mm in diameter (91.35% by mass), of which the median particle size is about 5 mm. Gravel particles smaller than 5 mm, i.e., fine sand, account for 52% by mass, sand particles smaller than 2 mm in diameter account for 32.5% by mass, fine particles smaller than 0.075 mm account for 0.6%, clay content is extremely low, and the thickness L of the fine sand layer is 3 m.

[0054] The range of solid particle size D in the weathered rock strata of the study area was obtained by consulting relevant literature. Figure 3 Based on the pore geometry analysis of the ideal equigranular sphere model in porous media theory, weathered rock particles are considered as ideal equigranular spherical particles. The pore throat and pore belly ranges under cubic arrangement conditions and the pore throat range under tetrahedral arrangement conditions are calculated respectively. The minimum value among these three ranges is taken as the maximum fine particle size that can penetrate the overall descending layer. Particles in the Quaternary gravel layer with a size smaller than this maximum fine particle size are the solid particles that can flow into the well. Thus, the particle size range of solid particles constituting the main component of debris flow is obtained. Combined with the particle gradation of the Quaternary gravel layer, the proportion of solid particles constituting the main component of debris flow in the Quaternary gravel layer is determined. This proportion is used to determine the amount of debris flow material sourced underground. Among them:

[0055] Under cubic arrangement conditions, the throat d and the belly d of the pore / The calculation formula is:

[0056] ;

[0057] ;

[0058] In the formula, |AB| represents the face diagonal of the cube, |BC| represents the side length of the cube, and |AC| represents the solid diagonal of the cube.

[0059] Under the condition of tetrahedral arrangement, the formula for calculating the throat d is:

[0060] d= =0.155D;

[0061] Specifically, in this embodiment, using mine geological survey data and borehole database data, it was found that the solid particle size D of the weathered rock layer in the collapse area of ​​the Shuangjianshan silver-lead-zinc mine in Inner Mongolia ranges from 40mm to 80mm. Figure 3 Substitute the minimum value of D, 40 mm, into the values ​​of d for the throat and d for the belly of the pore. / The calculation formula yields a minimum throat d of 16.6 mm and a pore belly d of 16.6 mm under cubic arrangement conditions. / The minimum value is 29.3 mm, and the minimum value of pore throat d under the condition of tetrahedral arrangement is 6.2 mm. Taking the minimum value of 6.2 mm among the three, it is the maximum fine particle size that can penetrate the overall downward-moving layer in the Quaternary sand layer of this study area. Combined with the particle size distribution data of the Quaternary sand and gravel layer in this study area, it is found that the proportion of solid particles that constitute the main component of debris flow in the Quaternary sand and gravel layer of this study area is about 52%. Therefore, it can be determined that solid particles with a particle size of less than 6.2 mm (accounting for about 52%) in the Quaternary sand and gravel layer of this study area may flow into the well and are the main source of debris flow.

[0062] Step 3.2: Conduct indoor seepage and sand-breaking experiments on the samples taken from the site to analyze the seepage characteristics, obtain the two-phase transport characteristics of water and sand, the time-varying relationship curves of water and sand phase flow rates, and then obtain the volume proportion of sand in the sand discharge stage, the volume proportion of sand in the sand-breaking stage, and the critical hydraulic gradient for sand discharge. and critical hydraulic gradient of sand erosion Then, the water level at the sand outlet and the water level at the sand intrusion of the Quaternary gravel layer are calculated. The indoor seepage and sand intrusion experiments include indoor "Z"-shaped channel and cross-fracture grid seepage and sand intrusion experiments (see...). Figure 2 The volume percentages of sand obtained during the sand production stage and the sand collapse stage are used to help mines design sand control and reinforcement measures, avoid disasters such as roadway blockage and ground subsidence, and ensure safe production in the mine.

[0063] Specifically, in this embodiment, based on the fracture channel conditions determined in step 1, a cross-fracture grid seepage and sand-breaking experiment was conducted. This revealed that in the Quaternary gravel layer of the study area, the volume percentage of sand in the sand-producing stage was approximately 3%–5%, and the volume percentage of sand in the sand-breaking stage was approximately 10%–15%. The critical hydraulic gradient for sand-producing was determined. The critical hydraulic gradient for sand erosion is 1.83. It is 2.94.

[0064] Based on the following hydraulic gradient calculation formula, the calculation reaches... and At that time, the water level of the Quaternary gravel layer needs to be raised by a certain height, namely the sand discharge water level and the sand collapse water level:

[0065] (2);

[0066] In the formula, For hydraulic gradient, This refers to the height above the soil layer where the water level rises. Specifically, in this embodiment, based on the hydraulic gradient calculation formula, the calculated sand-exiting water level of the Quaternary gravel layer in the study area is 5.49m, and the sand-collapse water level is 8.82m. Only when the water level rises to these two heights can the critical hydraulic gradient for sand exit be reached. and critical hydraulic gradient of sand erosion .

[0067] Step 4: Calculate the infiltration rate of the upper boundary of the Quaternary gravel layer under the most unfavorable working condition. Specifically:

[0068] The most unfavorable working condition refers to the analysis of a single ore-gathering trough in the study area, and the rainfall in the subsidence pit within the surface impact area of ​​the single ore-gathering trough during the ore discharge process is taken as the water source condition.

[0069] The projected area A of the single-gathering ore basin in the study area and the area of ​​the subsidence zone it formed on the surface were obtained by consulting relevant data. Area of ​​the surrounding fracture zone and the rainwater infiltration coefficient in the subsidence area and the infiltration coefficient of rainstorms in the fissure zone .

[0070] The following formula is used to calculate the rainwater infiltration at the upper boundary of the Quaternary gravel layer under different rainstorm frequencies P. :

[0071] (3);

[0072] Specifically, in this embodiment, the query yields... 309.4m 2 , 35155.25m 2 Rainfall infiltration coefficient in the subsidence area The infiltration coefficient of rainwater in the water-conducting fracture zone is 0.4. The value is 0.25. Then, using formula (3), the frequency P of the four types of rainstorms is calculated at the upper boundary of the Quaternary gravel layer. The values ​​were 1608.0 m³ / d (P=1%), 1403.2 m³ / d (P=2%), 1131.5 m³ / d (P=5%), and 925.7 m³ / d (P=10%), respectively.

[0073] Step 5: Calculate the sand-producing rainwater infiltration at the lower boundary of the Quaternary gravel layer. and sandstorm seepage Specifically:

[0074] The following formulas are used to calculate the sand discharge and sand erosion stormwater infiltration at the lower boundary of the Quaternary gravel layer:

[0075] (4);

[0076] (5);

[0077] In the formula, and These represent the seepage rates during sand discharge storms and sand collapse storms, respectively. K is the permeability coefficient, and A is the projected area of ​​the ore-accumulating trough.

[0078] Specifically, in this embodiment, the amount of rainstorm infiltration at the lower boundary of the Quaternary gravel layer was calculated. and They are 1848.5m respectively. 3 / d and 2969.7m 3 / d.

[0079] Step 6: Compare the seepage volume of sand-producing storms and sand-breaking storms with the seepage volume of storms at each storm frequency P to preliminarily determine whether there is a risk of sand production or sand breaking. For cases where there is a risk of sand production or sand breaking, calculate the time required for the water level to rise to the sand production level or sand breaking level. If the time is less than or equal to 24 hours, there is a risk of sand production or sand breaking; otherwise, there is no risk. Specifically:

[0080] Will , With different p-values Comparison, such as and All greater than If the P-value indicates no risk of sand production or sand collapse, then it is determined that there is no risk of sand production or sand collapse at that P-value. If so, it is preliminarily determined that there is a risk of sand production. If so, it is preliminarily determined that there is a risk of sand production and sand collapse.

[0081] When a preliminary assessment indicates a risk of sand discharge or sand intrusion, the following formula can be used to calculate the time required for the water level to rise to the sand discharge level and the sand intrusion level during the infiltration of the Quaternary gravel layer by rainwater at the corresponding P value. and :

[0082] (6);

[0083] (7);

[0084] (8);

[0085] In the formula, V is the pore volume within the projected column of a single aggregate ore bin. The porosity within the projected column of the single-aggregate ore bin is obtained from research data; specifically in this embodiment... It is 0.4.

[0086] like , If the rainfall is less than 24 hours, there is a risk of sand outflow or sand collapse; otherwise, there is no risk. Record the frequency P of rainstorms that indicate a risk of sand outflow or sand collapse; monitor the 24-hour rainfall in the mining area in real time. When a rainstorm with a frequency P indicating a risk of sand outflow or sand collapse occurs, it is determined that the mining area is at risk of debris flow.

[0087] Specifically, in this embodiment, through comparison, the study area under the four values ​​of P... and All greater than Therefore, the study area does not have the risk of sand discharge or sand collapse, and there is no risk of debris flow.

[0088] Step 7, further analyze the risk of debris flow under short-term heavy rainfall: The average value of the 24-hour maximum rainfall in Step 2... Replace with the 6-hour maximum rainfall average. Calculate the 6-hour rainfall under different frequencies P of rainstorm occurrence. Repeat step 4 to calculate the frequency P of different rainstorms. Repeat step 5 to calculate. and Repeat step 6 to analyze the risk of sand production and sand collapse under different rainstorm frequencies P.

[0089] Specifically, in this embodiment, the average 6-hour maximum rainfall over the years within the mining area was obtained by querying the data. Using formula (1), the 6-hour rainfall in the study area under four P values ​​was calculated to be 114.9 mm (P=1%), 100.2 mm (P=2%), 80.8 mm (P=5%), and 66.1 mm (P=10%), respectively; using formula (3), the upper boundary of the Quaternary gravel layer under the four working conditions was calculated. The values ​​are 170.7 m³ / h (P=1%), 148.8 m³ / h (P=2%), 120.0 m³ / h (P=5%), and 98.2 m³ / h (P=10%), respectively. Formula (5) is used to calculate the lower boundary of the Quaternary gravel layer above a single ore-accumulating trough under the four working conditions. =77.1 m³ / h, =123.8 m³ / h; and With different p-values By comparison, it was initially determined that there was a risk of sand production when the P value was 1%, 2%, 5%, and 10%, and a risk of sand collapse when the P value was 1% and 2%. For cases where there was a risk of sand production or sand collapse, the time required for the water level to rise to the sand production level or sand collapse level was further calculated using formulas (6) to (8). It was found that when the P value was 1%, 2%, 5%, and 10%, the time required for the water level to rise to the sand production level was 4.6h (P=1%), 6.0h (P=2%), 10.0h (P=5%), and 20.3h (P=10%), respectively. Among them, the time required for the water level to rise to the sand production level was less than or equal to 6h. Therefore, there was a risk of sand production in the well when the P value was 1% and 2%. When the P value was 1% and 2%, the time required for the water level to rise to the sand collapse level was 14.7h and 27.5h, respectively, which were much greater than 6h. Therefore, there was no risk of sand collapse when the P value was 1% and 2%.

[0090] The above description represents a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for quantitative analysis and evaluation of debris flow risk in underground mines, characterized in that, include: Step 1: Obtain the digital elevation model (DEM) of the study area to determine the conditions for debris flow formation; Step 2: Calculate the 24-hour rainfall under different rainstorm frequencies P in the study area; Step 3: Determine the thickness L and permeability coefficient K of the Quaternary gravel layer's fine sand layer through sieving and permeability tests; determine the critical hydraulic gradient for sand extrusion through indoor seepage and sand-breaking experiments. Critical hydraulic gradient for sand erosion Then, the sand level height and the sand runoff level height can be calculated. Step 4: Calculate the infiltration rate of the upper boundary of the Quaternary gravel layer under the most unfavorable working condition. ; Step 5: Calculate the sand-producing rainwater infiltration at the lower boundary of the Quaternary gravel layer. and sandstorm seepage ; Step 6: By comparison and and And whether the time required for the water level to rise to the sand discharge level and the sand breach level exceeds 24 hours, to determine whether there is a risk of sand discharge or sand breach under each rainstorm frequency P. Step 7: Use the same method to determine whether there is a risk of sand production or sand collapse under the frequency P of each rainstorm under short-term heavy rainfall.

2. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, Step 2 specifically involves: querying the historical average maximum 24-hour rainfall within the mining area. Modulus Calculate 24-hour rainfall under different P values. : （1）。 3. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, In step 3, the particle size distribution of the Quaternary gravel layer in the study area is obtained through particle sieving and permeability testing. The range of solid particle size of the weathered rock layer in the study area is obtained by querying the data. The weathered rock layer particles are regarded as ideal equigranular spherical particles. The range of pore throat and pore belly under cubic arrangement and the range of pore throat under tetrahedral arrangement are calculated respectively. The minimum value among these three range values ​​is taken as the maximum fine particle size that can pass through the overall downward layer. Combined with the particle size distribution of the Quaternary gravel layer, the proportion of solid particles with a particle size smaller than the maximum fine particle size in the Quaternary gravel layer is determined, which is used to determine the source amount of debris flow material in the well.

4. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, In step 3, the volume percentage of sand in the sand discharge stage and the volume percentage of sand in the sand inrush stage are obtained through indoor seepage and sand inrush experiments, which serve as the basis for the mine to take sand control measures.

5. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, In step 3, the hydraulic gradient is calculated according to the following formula to achieve... and At that time, the water level of the Quaternary gravel layer needs to be raised by a certain height, namely the sand discharge water level and the sand collapse water level: （2）； In the formula, For hydraulic gradient, The height to which the water level rises above the soil layer.

6. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, Step 4 specifically involves selecting a single ore-collecting trough within the study area as the most unfavorable working condition, and using rainfall within the subsidence pit in the surface influence area of ​​this single ore-collecting trough as the water source condition; then, the projected area of ​​the single ore-collecting trough in the study area is obtained. The area of ​​the subsidence zone it forms on the ground Area of ​​the surrounding fracture zone and the rainwater infiltration coefficient in the subsidence area and the infiltration coefficient of rainstorms in the fissure zone The following formula was used to calculate the rainwater infiltration at the upper boundary of the Quaternary gravel layer under different rainstorm frequencies P. : （3）。 7. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, Step 5 specifically includes: The following formulas are used to calculate the sand discharge and sand erosion stormwater infiltration at the lower boundary of the Quaternary gravel layer: （4）； （5）； In the formula, K is the permeability coefficient and A is the projected area of ​​a single aggregate ore bin.

8. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, Specifically, step 6 involves... , With different p-values Comparison, such as and All greater than If the P-value indicates no risk of sand production or sand collapse, then it is determined that there is no risk of sand production or sand collapse at that P-value. If so, it is preliminarily determined that there is a risk of sand production. If so, it is preliminarily determined that there is a risk of sand production and sand collapse; When a preliminary assessment indicates a risk of sand production or sand runoff, calculate the time required for the water level to rise to the corresponding P-value and sand production / sand runoff levels. and ;like , If the rainfall is less than 24 hours, there is a risk of sand discharge or sand collapse; otherwise, there is no risk of sand discharge or sand collapse. Record the frequency P of rainstorms that indicate a risk of sand discharge or sand collapse. Monitor the 24-hour rainfall in the mining area in real time. When the frequency P of rainstorms that indicate a risk of sand discharge or sand collapse occurs, it is determined that there is a risk of debris flow in the mining area.

9. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 8, characterized in that, Calculated using the following formula and : （6）； （7）； （8）； In the formula, V is the pore volume within the projected column of a single aggregate ore bin. The porosity is the projected value within the single-celled ore bin. A represents the height above the soil layer where the water level rises, and A is the projected area of ​​a single aggregate ore bin.

10. The method for quantitative analysis and evaluation of debris flow risk in underground mines according to claim 1, characterized in that, Specifically, step 7 involves repeating steps 2 and 4 to calculate the 6-hour rainfall and the rain infiltration amount at the upper boundary of the Quaternary gravel layer under different rainstorm frequencies P in the study area, and repeating step 6 to analyze the risk of sand production and sand intrusion under different rainstorm frequencies P during short-term heavy rainfall.

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