Comprehensive risk assessment method for dangerous rockfall of highway in mountainous area in operation period

Abstract

The invention relates to a comprehensive risk assessment method for dangerous rockfall of an expressway in a mountainous area in an operation period, and belongs to the technical field of disaster prevention and reduction. The method comprises the seven steps of preliminary investigation of highway dangerous rock falling risk sections, fine investigation of highway dangerous rock falling important risk sections, highway dangerous rock falling risk current situation assessment, highway dangerous rock falling risk prediction assessment, highway dangerous rock falling risk comprehensive assessment and the like. According to the method, the risk assessment of the dangerous rock falling development section in the operation stage of the highway in the mountainous area is realized, and the blank of the technology in China is filled. The method can effectively support the mountain area highway dangerous rock falling prevention and control decision in the operation period, carries out grading prevention and control on risks, further guarantees the operation safety of the mountain area highway, and improves the use efficiency of operation management and maintenance funds.

Description

Technical Field

[0001] The invention belongs to the technical field of disaster prevention and reduction, and specifically relates to a comprehensive risk assessment method for dangerous rockfall on mountain highways during operation. Background Art

[0002] During the operation period, the canyon sections of mountain highways have steep slopes and complex geological environmental conditions. The rock mass on the upper part of the slope has been affected by weathering for a long time. Under the influence of factors such as earthquakes, heavy rainfall or continuous rainfall, it is very easy to collapse and fall rocks, which seriously threatens the normal operation of the highway. The collapse of dangerous rocks on mountain highways is characterized by suddenness, concealment, high-level strong disaster-causing, and difficulty in treatment. Once it occurs, it will not only damage infrastructure and cause casualties, but also affect transportation. The social economy in the affected area will face huge losses, and the harm is very significant.

[0003] Since dangerous rockfalls on mountain highways are sudden, hidden, and highly catastrophic, highway operation and maintenance work faces great challenges. Prevention and rapid treatment of dangerous rockfalls are particularly important. However, for mountain highways during the operation period, maintenance funds are limited. Operation and maintenance units need to make scientific and effective decisions and use limited funds where they are most needed. Therefore, it is particularly important to carry out comprehensive risk assessment of dangerous rockfalls along highways. Through risk assessment, the risk level of dangerous rockfalls along the road is evaluated and the degree of urgency is determined, thereby providing technical support for treatment decisions on each section of the road.

[0004] At present, there is no relevant research and current standards for the risk assessment of dangerous rockfall on mountain highway slopes in the domestic highway industry. The current "Geological Hazard Hazard Assessment Standard" (GB / T40112) of the natural resources department lacks risk assessment methods and processes for existing projects. In addition, the Oregon Department of Transportation developed the Rockfall Hazard Rating System (RHRS) in 1984 to determine the risk level of collapse along the road, thereby determining the economic level of emergency repair projects for each section of the road.

[0005] The "Geological Hazard Hazard Assessment Specification" (GB / T40112) in the existing technical solutions is a standard specially formulated to regulate the geological hazard assessment work of engineering construction and planning in geological hazard prone areas. This standard stipulates the contents of geological environmental conditions investigation, geological disaster investigation, geological hazard status assessment, predictive assessment, comprehensive assessment and construction land suitability assessment. However, this standard cannot be fully applied to the operation period projects, and cannot meet the needs of scientific decision-making for operation and maintenance of mountain highways and disaster treatment during the operation period. It does not provide sufficient support for the urgency and graded treatment of disasters. The Oregon Department of Transportation's Rockfall Hazard Rating System (RHRS) takes into account both the rockfall hazard and the dynamic vulnerability of the road in the evaluation. The method is divided into three steps: the first step is on-site investigation, the second step is expert preliminary assessment, and the third step is detailed evaluation. The system takes into account the characteristics of the collapse slope hazards (slope height, structural surface morphology, geological structure, collapse volume), rockfall inducing factors (climate and water presence), rockfall frequency, and the vulnerability of property in time and space (ditch effectiveness, average vehicle risk, decision sight distance percentage, road width). The system considers many factors, but does not consider factors such as slope morphology, vegetation development, slope material composition, earthquake inducing factors, and carrier type. It has a great impact on the movement trajectory and movement characteristics of dangerous rockfall on mountain highways, and is more critical to the assessment of danger. In addition, the system has many and complex parameters, and is difficult to apply and has poor adaptability to emergency situations in post-disaster assessment of mountain highways. In view of this, it is particularly important to propose a method for comprehensive risk assessment of dangerous rockfall on mountain highways that is easy to operate, quick to evaluate, comprehensive, reliable, and adaptable to the operation period. Summary of the invention

[0006] The purpose of the present invention is to solve the deficiencies of the prior art and provide a comprehensive risk assessment method for dangerous rockfall on mountain highways during operation. The present invention is easy to operate, quick to assess, comprehensive and highly reliable, and can be used for comprehensive risk assessment of dangerous rockfall on mountain highways during operation.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0008] A comprehensive risk assessment method for dangerous rockfall on mountain highways during operation period comprises the following steps:

[0009] Step 1. Preliminary investigation of highway sections with dangerous rockfall risks: Obtain images of highway corridors and geological environment, collapse history and disaster damage information of the highway sections to be assessed; select sections with collapse history and disaster damage and determine them as key assessment sections for dangerous rockfall;

[0010] Step 2. Detailed investigation of important risk sections of dangerous rockfall on highways: Take close-up drone photos of dangerous rock masses in key assessment sections of dangerous rockfall and build a three-dimensional model, then extract the characteristic parameters of dangerous rock masses from the three-dimensional model; determine the distribution elevation, shape and volume of each dangerous rock mass, and analyze based on the data obtained in Step 1 to find out the existing protection measures in the direction of movement of the dangerous rock mass, the type of threatened object, the type of slope material, the type and growth of vegetation, and determine the main collapse type of the dangerous rock mass;

[0011] Step 3. Assessment of the current status of dangerous rockfall hazards on highways: Based on the information obtained in Step 1 and the data obtained in Step 2, the dangerous rock susceptibility, development degree and hazard degree of the key assessment sections of dangerous rockfall are qualitatively graded, and the qualitative classification of dangerous rock susceptibility, development degree and hazard degree are analyzed to obtain the hazard status assessment and classification results;

[0012] Step 4. Prediction and assessment of the hazard of dangerous rockfall on highways: Calculate the stability of dangerous rock masses and estimate the impact range of dangerous rockfalls, and then determine the hazard prediction and assessment level results for each section of the assessment section;

[0013] Step 5. Comprehensive assessment of highway dangerous rockfall risk: The risk of highway dangerous rockfall is assessed by using the index system method, the expert assessment method based on the index system, and the expert survey method. Finally, the assessment results of highway dangerous rockfall risk obtained by the three methods are used to determine the risk level of collapse and rockfall in the assessment section.

[0014] Step 6. Based on the data obtained in Step 1 and the results of Step 2 to Step 5, mark the location and impact range of dangerous rock masses in each section of the assessment section in the highway geological plan and draw them as closed areas. Fill them with red according to the risk level, yellow according to the risk level, and green according to the risk level. Complete the drawing of the comprehensive assessment map of dangerous rockfall risks on the highway; according to the comprehensive risk assessment results of Step 5, the higher the risk level, the higher the degree of urgency, and determine different prevention and control measures according to the risk level;

[0015] Step 7. Based on the data obtained in Step 1 and the results of Step 2 to Step 6, prepare a comprehensive assessment report on the risk of dangerous rock falls on highways to complete the assessment work.

[0016] Further, preferably, the specific steps of step 1 are:

[0017] 101. Take drone aerial photos of the highway sections to be evaluated and use oblique photogrammetry to obtain images of the highway corridors;

[0018] 102. Conduct geological environmental surveys on the expressway sections to be assessed and collect geological environmental data; the geological environmental data include topography, meteorology and hydrology, stratum lithology, geological structure, earthquakes, vegetation development and human engineering activities;

[0019] 103. Collect data on the collapse history and damage of the highway section to be assessed;

[0020] 104. Based on the impact data obtained from 101 to 103, we screened out sections with a history of collapse and disaster damage and identified them as key assessment sections for dangerous rock falls.

[0021] Further, preferably, the specific steps of step 2 are:

[0022] 201. Carry out drone close-up photogrammetry in the key assessment section for dangerous rockfalls, photograph the dangerous rock mass and construct a three-dimensional model; the first-level terrain watershed above the assessment section is the upper boundary of the dangerous rock mass, and the terrain turning point below the assessment section is the lower boundary of the dangerous rock mass;

[0023] The characteristic parameters of dangerous rock mass are extracted through the constructed three-dimensional model; the characteristic parameters of dangerous rock mass include the occurrence of rock and soil structure surface, the inclination of the slope free surface and the slope angle; finally, the occurrence of dominant joints and fissures in each key section is counted;

[0024] 202. Using the three-dimensional model constructed in step 201, find out the structural surface combination, crack filling and opening of the dangerous rock mass, identify the distribution of dangerous rock masses in key sections of dangerous rockfall, mark and number the identified dangerous rock masses, and measure the distribution elevation, shape and volume of each dangerous rock mass through the model;

[0025] 203. Using the three-dimensional model constructed in step 201, find out the existing protective measures in the direction of movement of the dangerous rock mass, and determine whether there are any protective measures. If so, obtain the effectiveness of the existing protective measures;

[0026] Identify the types of threatened objects in the direction of movement of the dangerous rock mass; the types of threatened objects are classified into roadbed, bridge, tunnel or other structures;

[0027] Identify the slope material type and divide the slope into different sections according to the slope material type;

[0028] Among them, the slope material types are divided into rock, soil or other loose accumulations;

[0029] Find out the vegetation types and their growth conditions. Vegetation types are divided into shrubs, grasses and trees;

[0030] 204. According to the Engineering Geology Manual, the main types of collapse of dangerous rock masses are analyzed according to the characteristics of the structural surface and the properties of the lower rock mass of the dangerous rock mass; among them, the main types of collapse of dangerous rock masses include tipping type, sliding type and tensile type.

[0031] Further, preferably, the specific steps of step 3 are:

[0032] 301. Use Table 1 to carry out qualitative classification of dangerous rock susceptibility in key assessment sections for dangerous rockfall;

[0033] Table 1 Classification of dangerous rock mass susceptibility

[0034]

[0035] 302. Based on the classification results of step 301, the development degree of the key assessment section of dangerous rockfall is classified:

[0036] If the dangerous rock susceptibility is classified as extremely high or high, and the dangerous rock is in an unstable or unstable state, the development degree is classified as strong development;

[0037] If the susceptibility of dangerous rock is classified as low or medium, and the dangerous rock is in an unstable state, the development degree is classified as medium;

[0038] If the susceptibility of dangerous rock is classified as low susceptibility and the dangerous rock is in an unstable or unstable state, the development degree is classified as weak development;

[0039] Specifically, Table 2 is used to classify the development degree of the key assessment sections of dangerous rockfalls:

[0040] Table 2 Classification of collapse development degree

[0041]

[0042] 303. Based on Table 3 and in accordance with the principle of going higher rather than lower, the hazard level of the key assessment areas of dangerous rockfall is graded:

[0043] Table 3 Hazard level classification table

[0044]

[0045] 304. Based on the classification results of step 302 and step 303, the dangerous status assessment and classification of the key assessment sections of dangerous rockfall are carried out using Table 4:

[0046] Table 4 Hazard classification table

[0047]

[0048]

[0049] Further, preferably, the specific steps of step 4 are:

[0050] 401. According to the main collapse types of dangerous rock mass, refer to the stability calculation formula of the Engineering Geology Manual, and use the relevant parameters of dangerous rock mass obtained in Step 2 to carry out stability calculation and analysis of dangerous rock mass;

[0051] 402. According to the topography of the dangerous rock mass, the type of slope material, existing protective measures, the type and growth of vegetation, and the movement traces of the fallen rocks, the motion parameters of different sections of the slope rolling path are inverted using the Rocfall rockfall analysis software; then, the inverted motion parameters are used to carry out the motion path and impact capacity analysis of the dangerous rockfall collapse, and the impact range of the dangerous rockfall is estimated; among them, the motion parameters include the tangential restitution coefficient, the normal restitution coefficient and the friction coefficient;

[0052] 403. Referring to Table 5, based on the calculation and analysis results of the dangerous rock mass stability and the impact range of dangerous rockfall, combined with the spatial position relationship between the road and the dangerous rock mass, analyze the possibility, degree of hazard impact, and degree of development of highway facilities being harmed by dangerous rockfall, and determine the hazard prediction assessment level.

[0053] Further, preferably, the specific steps of step 5 are:

[0054] 501. Use the index system method to assess the risk of dangerous rockfall on highways:

[0055] (1) An index system consisting of six indicators, namely, the current status assessment results of dangerous rockfall hazards, the prediction assessment results, the disaster scale, the complexity of geological environmental conditions, the socio-economic attributes of the disaster targets, and the difficulty of geological disaster prevention and control, was constructed. The weights of each indicator were obtained according to Table 6;

[0056] (2) According to the situation of each section, the above six indicators are evaluated and scored according to Table 6, and the risk index P is calculated. 1 , see formula (1);

[0057]

[0058] Where: P 1 is the risk index;

[0059] γ i is the weight coefficient of the evaluation index;

[0060] X i is the score of the evaluation index;

[0061] i is the serial number of the evaluation index;

[0062] n is the number of evaluation indicators, n = 6;

[0063] (3) According to the risk index P, the risk level of rockfall in the assessment section is determined to be G according to Table 7. 1 ;

[0064] Table 7 Risk level classification standards

[0065] <![CDATA[Risk level G 1 > Risk color Risk Situation Risk Index Level I red Severe rockfall and landslides, high risk Risk index ≥ 20 Level II yellow Landslides and rockfalls are common, with medium risk 10≤Risk Index<20 Grade III green The rockfall is minor and the risk is low. Risk index <10

[0066] 502. Use expert evaluation method based on index system to assess the risk of dangerous rockfall on highways:

[0067] (1) Invite experts to conduct on-site research, the number of experts n ≥ 5, n is an odd number;

[0068] (2) The experts' years of experience and professional titles were counted, and the years of experience were divided into three levels: 1 point for less than 10 years, 2 points for more than 10 years and 3 points for more than 20 years. At the same time, it was stipulated that experts with intermediate professional titles were awarded 1 point, 2 points for associate senior professional titles and 3 points for senior professional titles. The scores of each expert were calculated by adding the scores of years of experience and professional titles, and the sum of all experts' scores was further calculated. Finally, the ratio of each expert's score to the sum of all experts' scores was calculated, that is, the expert's weight was obtained;

[0069] (3) The experts ranked the importance of the six elements of each slope according to the evaluation object, and thus calculated the weights of the six elements of each object by each expert;

[0070] The weight coefficient calculation formula of the indicator importance ranking method is as follows:

[0071]

[0072] Where: γ ij is the weight coefficient of expert i for the jth evaluation index;

[0073] m is the importance ranking of evaluation indicators by experts, 1≤m≤6;

[0074] (4) Calculate the risk factor P assessed by the expert group 2 , the calculation formula is as follows:

[0075]

[0076] Where: i is the expert number;

[0077] j is the index number;

[0078] W i is the weight of the i-th expert;

[0079] γ ij is the weight of the i-th expert on the j-th indicator;

[0080] X ij is the score given by the i-th expert on the j-th indicator.

[0081] (5) According to Table 7, determine the risk level of collapse and rockfall in the assessment section G 2 ;

[0082] 503. Use expert survey method to conduct risk assessment of dangerous rockfall on highways:

[0083] (1) Invite the experts in step 502 to directly assess the risk of dangerous rockfall in the assessment section;

[0084] (2) The evaluation results of each expert are counted and the principle of minority obeys majority is adopted to determine the risk level of collapse and rockfall in the evaluation section G. 3 ;

[0085] 504. Adopt the principle of high risk rather than low risk, take the highest risk rating, and determine the collapse and rockfall risk level G of the assessment section, as follows:

[0086] G=MAX(G 1 , G 2 , G 3 ) (4).

[0087] In step 101 of the present invention, drone aerial photography is performed on the highway section to be evaluated, and an oblique photogrammetry method is used to obtain images of the highway corridor to understand the terrain characteristics, vegetation development, and dangerous rock mass distribution of the highway corridor.

[0088] In the present invention, the expressway section is existing and the present invention does not divide it.

[0089] In step 201 of the present invention, the terrain turning point is a river or a trough.

[0090] In step 301 of the present invention, dangerous rocks or dangerous rock groups, isolated rocks or isolated rock groups are conventionally interpreted according to existing geological terms, and the present invention does not make special limitations on this, wherein dangerous rocks are dangerous bodies on steep cliffs or slopes, dangerous rock groups are multiple dangerous rocks, and isolated rocks or isolated rock groups are in the middle of the slope, which are generally completely or partially separated from the parent rock.

[0091] Compared with the prior art, the present invention has the following beneficial effects:

[0092] The present invention proposes to conduct a preliminary investigation of dangerous rockfall risk sections on highways and a detailed investigation of important risk sections on highways, conduct a status assessment and a predictive assessment of the danger of dangerous rockfall on highways, consider the status assessment results, predictive assessment results, disaster scale, complexity of geological environmental conditions, socio-economic attributes of disaster targets, difficulty of geological disaster prevention and control and other evaluation indicators, and adopt an indicator system method, an expert evaluation method based on the indicator system and an expert investigation method to combine the comprehensive assessment method of dangerous rockfall risks on mountainous highways during the operation period, thus realizing the risk assessment of dangerous rockfall development sections during the operation period of mountainous highways, filling the gap in this technology in China. This technology can effectively support the decision-making of dangerous rockfall prevention and control on mountainous highways during the operation period, conduct graded prevention and control of risks, further ensure the operational safety of mountainous highways, and improve the efficiency of the use of operation and maintenance funds. BRIEF DESCRIPTION OF THE DRAWINGS

[0093] Figure 1 The present invention is a flow chart of a comprehensive risk assessment method for dangerous rockfall on mountain highways during operation.

[0094] Figure 2 This is a comprehensive assessment diagram of dangerous rockfall risks on a highway in an application example of the present invention. DETAILED DESCRIPTION

[0095] The present invention is further described in detail below in conjunction with embodiments.

[0096] Those skilled in the art will appreciate that the following examples are only used to illustrate the present invention and should not be considered to limit the scope of the present invention. If no specific techniques or conditions are specified in the examples, the techniques or conditions described in the literature in the art or the product specifications are used. If the manufacturer of the materials or equipment used is not specified, they are all conventional products that can be purchased.

[0097] See also Figure 1 A comprehensive risk assessment method for dangerous rockfall on mountain highways during operation period includes the following steps:

[0098] Step 1. Preliminary investigation of dangerous rockfall risk sections on highways

[0099] Conduct a preliminary investigation on the main dangerous rockfall sections of the expressway during operation, with the aim of obtaining a detailed understanding of the main distribution of collapses, background conditions, inducing factors, and damage, so as to conduct a segmented assessment of the route and highlight key sections. In Step 1, the preliminary investigation of the dangerous rockfall risk sections of the highway includes:

[0100] Step 101, use drones to take aerial photos of the expressway section to be evaluated, and use oblique photogrammetry to obtain images of the expressway corridor. This technology can be used to grasp the terrain characteristics, vegetation development, and main distribution of dangerous rock masses in the expressway corridor in a short period of time. Since the dangerous rock masses around expressways during operation in mountainous areas are highly concealed, and a large number of dangerous rock masses are distributed at high positions that cannot be directly contacted, drones are needed. It should be noted that the orientation of drone image collection should be 500m upstream of the expressway line, and reaching the terrain watershed is more conducive to improving the reliability of the assessment;

[0101] In order to analyze the factors inducing collapse of dangerous rock masses along the line, further, step 102 conducts a geological environment survey on the highway section to be evaluated, collects data on topography, meteorology and hydrology, stratum lithology, geological structure, earthquakes, vegetation development, human engineering activities, etc., and analyzes them.

[0102] Step 103: Since collapses are characterized by group development, it is necessary to collect collapse history and disaster damage data of the highway section to be evaluated. On the one hand, it is used to analyze the probability of disaster occurrence, and on the other hand, it is used to analyze the disaster damage to further understand the degree of harm and support the next step of current status assessment.

[0103] Step 104, based on the above three steps, according to the terrain conditions, the concentration of collapse events, and the disaster damage, select the sections with collapse history and disaster damage, determine them as the key assessment sections for dangerous rock falls, and take the key assessment sections as the objects of the next detailed investigation.

[0104] Step 2. Detailed investigation of important risk sections of dangerous rocks and rockfalls on highways

[0105] Based on Step 1, a detailed investigation is conducted on the key assessment sections to find out the characteristics and distribution of dangerous rock masses in each key assessment section, providing data support for the next step of stability and hazard analysis. The main steps include the following:

[0106] 201. Carry out drone close-up photogrammetry in the key assessment section for dangerous rockfalls, photograph the dangerous rock mass and construct a three-dimensional model; the first-level terrain watershed above the assessment section is the upper boundary of the dangerous rock mass, and the terrain turning point below the assessment section is the lower boundary of the dangerous rock mass;

[0107] The characteristic parameters of dangerous rock mass are extracted through the constructed three-dimensional model; the characteristic parameters of dangerous rock mass include the occurrence of rock and soil structure surface, the inclination of the slope free surface and the slope angle; finally, the occurrence of dominant joints and fissures in each key section is counted;

[0108] 202. Using the three-dimensional model constructed in step 201, find out the structural surface combination, crack filling and opening of the dangerous rock mass, identify the distribution of dangerous rock masses in key sections of dangerous rockfall, mark and number the identified dangerous rock masses, and measure the distribution elevation, shape and volume of each dangerous rock mass through the model;

[0109] 203. Using the three-dimensional model constructed in step 201, find out the existing protective measures in the direction of movement of the dangerous rock mass, and determine whether there are any protective measures. If so, obtain the effectiveness of the existing protective measures;

[0110] Identify the types of threatened objects in the direction of movement of the dangerous rock mass; the types of threatened objects are classified into roadbed, bridge, tunnel or other structures;

[0111] Identify the slope material type and divide the slope into different sections according to the slope material type; the slope material type is divided into rock, soil or other loose accumulations;

[0112] Find out the vegetation types and their growth conditions. Vegetation types are divided into shrubs, grasses and trees;

[0113] 204. According to the Engineering Geology Manual, the main types of collapse of dangerous rock masses are analyzed according to the characteristics of the structural surface and the properties of the lower rock mass of the dangerous rock mass; among them, the main types of collapse of dangerous rock masses include tipping type, sliding type and tensile type.

[0114] Step 3. Assessment of the current status of dangerous rockfall on highways:

[0115] In Step 3, an assessment of the current status of dangerous rockfall on highways is conducted from several aspects, including the susceptibility of dangerous rockfall on highways, the degree of development, and the degree of hazard.

[0116] 301. Based on the structural surface, vegetation, terrain slope and Table 1, a qualitative classification of the susceptibility of dangerous rocks to falling rocks is carried out on the dangerous rock sections of the highway.

[0117] Table 1 Classification of dangerous rock mass susceptibility

[0118]

[0119]

[0120] 302. According to the stability state of dangerous rocks, distribution of dangerous rock masses and collapse history, the collapse development degree of dangerous rock falling sections of highway is classified according to Table 2.

[0121] Table 2 Classification of collapse development degree

[0122]

[0123] 303. Based on casualties, direct economic losses, possible direct economic losses, and in accordance with the principle of taking higher rather than lower risks, the degree of hazard for dangerous rockfall sections on highways is graded according to Table 3.

[0124] Table 3 Hazard level classification table

[0125]

[0126]

[0127] 304. Based on the results of steps 302 and 303, conduct a hazard status assessment and classification of the dangerous rock and rockfall sections of the highway according to Table 4.

[0128] Table 4 Hazard classification table

[0129]

[0130] Step 4. Prediction and assessment of the risk of dangerous rockfall on highways

[0131] Based on the current situation assessment, the step 4 highway dangerous rockfall hazard prediction assessment is further carried out, including the following steps:

[0132] 401. According to the main collapse types of dangerous rock mass, refer to the stability calculation formula of the Engineering Geology Manual, and use the relevant parameters of dangerous rock mass obtained in Step 2 to carry out stability calculation and analysis of dangerous rock mass;

[0133] 402. According to the topography of the dangerous rock mass, the type of slope material, existing protective measures, the type and growth of vegetation, and the movement traces of the fallen rocks, the motion parameters of different sections of the slope rolling path are inverted using the Rocfall rockfall analysis software; then, the inverted motion parameters are used to carry out the motion path and impact capacity analysis of the dangerous rockfall collapse, and the impact range of the dangerous rockfall is estimated; among them, the motion parameters include the tangential restitution coefficient, the normal restitution coefficient and the friction coefficient;

[0134] 403. Referring to Table 5, based on the calculation and analysis results of the dangerous rock mass stability and the impact range of dangerous rockfall, combined with the spatial position relationship between the road and the dangerous rock mass, analyze the possibility, degree of hazard impact, and degree of development of highway facilities being harmed by dangerous rockfall, and determine the hazard prediction assessment level.

[0135] Table 5 Hazard prediction assessment levels

[0136]

[0137]

[0138] Step 5. Comprehensive assessment of the risk of dangerous rockfall on highways

[0139] In Step 5, the indicator system method, the expert evaluation method based on the indicator system, and the expert investigation method are used to conduct a comprehensive assessment of the risk of dangerous rockfall on highways:

[0140] 501. Use the index system method to assess the risk of dangerous rockfall on highways:

[0141] (1) An index system consisting of six indicators, namely, the current status assessment results of dangerous rockfall hazards, the prediction assessment results, the disaster scale, the complexity of geological environmental conditions, the socio-economic attributes of the disaster targets, and the difficulty of geological disaster prevention and control, was constructed. The weights of each indicator were obtained according to Table 6;

[0142] (2) According to the situation of each section, the above six indicators are evaluated and scored according to Table 6 to calculate the risk index P 1 , see formula (1);

[0143] Table 6. Table of quantitative indexes for collapse and rockfall risk.

[0144]

[0145] (3) Based on the risk index P, combined with the investigation results, and comprehensive comparative analysis, the risk level of collapse and rockfall in the assessment section is determined to be G 1 , the risk level classification standards are shown in Table 7.

[0146] Table 7 Risk level classification standards

[0147]

[0148] 502. Use expert evaluation method based on index system to assess the risk of dangerous rockfall on highways:

[0149] (1) Invite experts in highway design, engineering geology, and construction to conduct on-site investigations. The number of experts is n ≥ 5, where n is an odd number.

[0150] (2) The experts' years of experience and professional titles were counted, and the years of experience were divided into three levels: 1 point for less than 10 years, 2 points for more than 10 years and 3 points for more than 20 years. At the same time, it was stipulated that experts with intermediate professional titles were awarded 1 point, 2 points for associate senior professional titles and 3 points for senior professional titles. The scores of each expert were calculated by adding the scores of years of experience and professional titles, and the sum of all experts' scores was further calculated. Finally, the ratio of each expert's score to the sum of all experts' scores was calculated, that is, the expert's weight was obtained;

[0151] (3) The experts ranked the importance of the six elements of each slope according to the evaluation object, and thus calculated the weights of the six elements of each object by each expert;

[0152] The weight coefficient calculation formula of the indicator importance ranking method is as follows:

[0153]

[0154] Where: γ ij is the weight coefficient of expert i for the jth evaluation index;

[0155] m is the importance ranking of evaluation indicators by experts, 1≤m≤6;

[0156] (4) Calculate the risk factor P assessed by the expert group 2 , the calculation formula is as follows:

[0157]

[0158] Where: i is the expert number;

[0159] j is the index number;

[0160] W i is the weight of the i-th expert;

[0161] γ ij is the weight of the i-th expert on the j-th indicator;

[0162] X ij is the score given by the i-th expert on the j-th indicator.

[0163] (5) Determine the collapse and rockfall risk level G2 in the assessment section based on Table 7.

[0164] 503. Use expert survey method to conduct risk assessment of dangerous rockfall on highways:

[0165] (1) Invite all experts in the expert group in step 502 to directly assess the risk of dangerous rockfall in the assessment section;

[0166] (2) The evaluation results of each expert are counted and the principle of minority obeys majority is adopted to determine the risk level of collapse and rockfall in the evaluation section G. 3 .

[0167] 504. Compare G1, G2 and G3, and adopt the principle of taking higher risk rather than lower risk, and take the one with the highest risk among the three as the collapse and rockfall risk level G of the assessment section.

[0168] Step 6. Divide the highway dangerous rockfall risk sections and draw a comprehensive assessment map of highway dangerous rockfall risk. According to the comprehensive risk assessment results, the higher the risk level, the higher the degree of urgency. Different prevention and control measures are determined according to Table 8;

[0169] Table 8 Risk classification and prevention and control measures

[0170]

[0171] Step 7. Based on the results of Step 1 to Step 6, prepare a comprehensive assessment report on the risk of dangerous rock falls on highways to complete the assessment work.

[0172] Application Examples

[0173] On May 2, 2023, a 5.2-magnitude earthquake occurred near a highway in western Yunnan, inducing rockfalls, resulting in damage or destruction of 7 kilometers of infrastructure along the highway. After the earthquake, a risk assessment of dangerous rockfalls is required. The above-mentioned comprehensive risk assessment method for dangerous rockfalls on mountain highways during operation is adopted as follows:

[0174] 1. Preliminary investigation of dangerous rockfall risk sections on the highway: Use the patented method of this invention to evaluate the highway. Investigate the rockfall history of this section of highway from May 2, 2023 to August 29, 2023, and determine that 13 sections need to be evaluated, that is, determine these 13 sections as the key evaluation sections for dangerous rockfall;

[0175] 2. Detailed investigation of important risk sections of dangerous rockfall on highways: For 13 key assessment sections of dangerous rockfall, carry out drone close-up photogrammetry and build a three-dimensional model, and then extract the characteristic parameters of dangerous rock masses from the three-dimensional model; determine the distribution elevation, shape and volume of each dangerous rock mass, find out the existing protection measures in the direction of movement of the dangerous rock mass, the type of threatened object, the type of slope material, the type and growth of vegetation, and determine the main collapse type of the dangerous rock mass;

[0176] 3. Assessment of the current status of dangerous rockfall on highways: Based on the data obtained in Step 1 and the data from Step 2, the dangerous rockfall assessment section is qualitatively classified for the susceptibility to dangerous rockfall, the degree of development, and the degree of hazard. The results of the current status of dangerous rockfall assessment are analyzed based on the qualitative classification of the susceptibility to dangerous rockfall, the degree of development, and the degree of hazard. The assessment results of this example are shown in Table 9.

[0177] 4. Prediction and assessment of the hazard of dangerous rockfall on highways: Calculate the stability of dangerous rock masses and estimate the impact range of dangerous rockfalls, and then determine the hazard prediction and assessment level results of each section in the assessment area; the assessment results of this example are shown in Table 9;

[0178] 5. Comprehensive assessment of highway dangerous rockfall risk: The risk of highway dangerous rockfall was assessed by using the index system method, the expert assessment method based on the index system, and the expert survey method. Finally, the assessment results of highway dangerous rockfall risk obtained by the three methods were used to determine the risk level of collapse and rockfall in the assessment section. The assessment results of this example are shown in Table 9. After assessment, among the 13 sections, 3 sections had a high risk of rockfall, 4 sections had a medium risk, and 6 sections had a low risk.

[0179] Table 9 Evaluation results

[0180]

[0181] 6. According to Table 9, mark the location and impact range of dangerous rock masses in each section of the assessment section in the highway geological plan and draw them as closed areas. Fill them with red for high risk, yellow for major risk, and green for low risk, and complete the drawing of the comprehensive assessment map of dangerous rockfall risks on highways; see Figure 2 ; According to Table 9, the higher the risk level, the higher the urgency level. Different prevention and control measures are determined according to the risk level, see Table 10;

[0182] 7. Based on the above results, prepare a comprehensive assessment report on the risk of dangerous rock falls on highways and complete the assessment work.

[0183] Table 10 List of measures to prevent and control dangerous rockfall in the assessed projects

[0184]

[0185]

[0186] The application in the risk assessment of dangerous rockfall on a highway in western Yunnan shows that the invention is scientifically reliable, highly credible, and feasible, and provides strong support for maintenance and treatment decisions.

[0187] Compared with the existing technology, the patent of this invention realizes the risk assessment of dangerous rockfall development sections during the operation stage of mountain highways, filling the gap of this technology in China. This technology can effectively support the decision-making of dangerous rockfall prevention and control on mountain highways during the operation period, carry out graded risk prevention and control, and further ensure the safety of mountain highway operations.

[0188] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A comprehensive risk assessment method for dangerous rockfall on mountain highways during operation, characterized in that: The steps include: Step 1. Preliminary investigation of highway sections with dangerous rockfall risks: Obtain images of highway corridors and geological environment, collapse history and disaster damage information of the highway sections to be assessed; select sections with collapse history and disaster damage and determine them as key assessment sections for dangerous rockfall; Step 2. Detailed investigation of important risk sections of dangerous rockfall on highways: Take close-up drone photos of dangerous rock masses in key assessment sections of dangerous rockfall and build a three-dimensional model, then extract the characteristic parameters of dangerous rock masses from the three-dimensional model; determine the distribution elevation, shape and volume of each dangerous rock mass, and analyze based on the data obtained in Step 1 to find out the existing protection measures in the direction of movement of the dangerous rock mass, the type of threatened object, the type of slope material, the type and growth of vegetation, and determine the main collapse type of the dangerous rock mass; Step 3. Assessment of the current status of dangerous rockfall hazards on highways: Based on the information obtained in Step 1 and the data obtained in Step 2, the dangerous rock susceptibility, development degree and hazard degree of the key assessment sections of dangerous rockfall are qualitatively graded, and the qualitative classification of dangerous rock susceptibility, development degree and hazard degree are analyzed to obtain the hazard status assessment and classification results; Step 4. Prediction and assessment of the hazard of dangerous rockfall on highways: Calculate the stability of dangerous rock masses and estimate the impact range of dangerous rockfalls, and then determine the hazard prediction and assessment level results for each section of the assessment section; Step 5. Comprehensive assessment of highway dangerous rockfall risk: The risk of highway dangerous rockfall is assessed by using the index system method, the expert assessment method based on the index system, and the expert survey method. Finally, the assessment results of highway dangerous rockfall risk obtained by the three methods are used to determine the risk level of collapse and rockfall in the assessment section. Step 6. Based on the data obtained in Step 1 and the results of Step 2 to Step 5, mark the location and impact range of each dangerous rock mass in the assessment section in the highway geological plan and draw it as a closed area. Fill it with red according to the risk of high risk, yellow according to the risk of major risk, and green according to the risk of small risk, and complete the drawing of the comprehensive assessment map of dangerous rockfall risks on the highway; According to the comprehensive risk assessment results of Step 5, the higher the risk level, the higher the urgency level, and different prevention and control measures are determined according to the risk level; Step 7. Based on the data obtained in Step 1 and the results of Step 2 to Step 6, prepare a comprehensive assessment report on the risk of dangerous rock falls on highways to complete the assessment work.

2. The comprehensive risk assessment method for dangerous rockfall on mountain highways during operation according to claim 1 is characterized in that: The specific steps of Step 1 are:

101. Take drone aerial photos of the highway sections to be evaluated and use oblique photogrammetry to obtain images of the highway corridors; 102. Conduct geological environmental surveys on the expressway sections to be assessed and collect geological environmental data; the geological environmental data include topography, meteorology and hydrology, stratum lithology, geological structure, earthquakes, vegetation development and human engineering activities; 103. Collect data on the collapse history and damage of the highway section to be assessed; 104. Based on the impact data obtained from 101 to 103, we screened out sections with a history of collapse and disaster damage and identified them as key assessment sections for dangerous rock falls.

3. The comprehensive risk assessment method for dangerous rockfall on mountain highways during operation according to claim 1 is characterized in that: The specific steps of Step 2 are:

201. Carry out drone close-up photogrammetry in the key assessment section for dangerous rockfalls, photograph the dangerous rock mass and construct a three-dimensional model; the first-level terrain watershed above the assessment section is the upper boundary of the dangerous rock mass, and the terrain turning point below the assessment section is the lower boundary of the dangerous rock mass; The characteristic parameters of dangerous rock mass are extracted through the constructed three-dimensional model; the characteristic parameters of dangerous rock mass include the occurrence of rock and soil structure surface, the inclination of the slope free surface and the slope angle; finally, the occurrence of dominant joints and fissures in each key section is counted; 202. Using the three-dimensional model constructed in step 201, find out the structural surface combination, crack filling and opening of the dangerous rock mass, identify the distribution of dangerous rock masses in key sections of dangerous rockfall, mark and number the identified dangerous rock masses, and measure the distribution elevation, shape and volume of each dangerous rock mass through the model; 203. Using the three-dimensional model constructed in step 201, find out the existing protective measures in the direction of movement of the dangerous rock mass, and determine whether there are any protective measures. If so, obtain the effectiveness of the existing protective measures; Identify the types of threatened objects in the direction of movement of the dangerous rock mass; the types of threatened objects are classified into roadbed, bridge, tunnel or other structures; Identify the slope material type and divide the slope into different sections according to the slope material type; the slope material type is divided into rock, soil or other loose accumulations; Find out the vegetation types and their growth conditions. Vegetation types are divided into shrubs, grasses and trees; 204. According to the characteristics of the structural surface and the properties of the lower rock mass of the dangerous rock mass, the main collapse types of the dangerous rock mass are analyzed; among them, the main collapse types of the dangerous rock mass include tipping type, sliding type and tensile type.

4. The comprehensive risk assessment method for dangerous rockfall on mountain highways during operation according to claim 1 is characterized in that: The specific steps of Step 3 are:

301. Use the following table to carry out qualitative classification of dangerous rock susceptibility in key assessment areas for dangerous rockfalls; 302. Based on the classification results of step 301, the development degree of the key assessment section of dangerous rockfall is classified: If the dangerous rock susceptibility is classified as extremely high or high, and the dangerous rock is in an unstable or unstable state, the development degree is classified as strong development; If the susceptibility of dangerous rock is classified as low or medium, and the dangerous rock is in an unstable state, the development degree is classified as medium; If the susceptibility of dangerous rock is classified as low susceptibility and the dangerous rock is in an unstable or unstable state, the development degree is classified as weak development; 303. Based on the following table and in accordance with the principle of going higher rather than lower, the hazard level of the key assessment areas of dangerous rockfall is graded:

304. Based on the classification results of step 302 and step 303, the following subscripts are used to carry out the current status evaluation and classification of the dangerous rockfall key assessment sections:

5. The comprehensive risk assessment method for dangerous rockfall on mountain highways during operation according to claim 1 is characterized in that: The specific steps of Step 4 are:

401. According to the main collapse types of dangerous rock mass, the stability calculation and analysis of dangerous rock mass is carried out using the dangerous rock mass related parameters obtained in Step 2; 402. According to the topography of the dangerous rock mass, the type of slope material, existing protective measures, the type and growth of vegetation, and the movement traces of the fallen rocks, the motion parameters of different sections of the slope rolling path are inverted; then, the motion parameters obtained by inversion are used to carry out the motion path and impact capacity analysis of the dangerous rock fall collapse, and the impact range of the dangerous rock fall is estimated; among them, the motion parameters include the tangential restitution coefficient, the normal restitution coefficient and the friction coefficient; 403. Based on the results of stability analysis of dangerous rock masses and the impact range of dangerous rockfalls, combined with the spatial relationship between roads and dangerous rock masses, the possibility, degree of impact, and degree of development of highway facilities being harmed by dangerous rockfalls are analyzed to determine the hazard prediction and assessment level.

6. The comprehensive risk assessment method for dangerous rockfall on mountain highways during operation according to claim 1 is characterized in that: The specific steps of Step 5 are:

501. Use the index system method to assess the risk of dangerous rockfall on highways: (1) Construct an index system consisting of six indicators, namely, the current status assessment results of dangerous rockfall hazards, the forecast assessment results, the disaster scale, the complexity of geological environmental conditions, the socio-economic attributes of the disaster targets, and the difficulty of geological disaster prevention and control, and obtain the weight of each indicator; (2) According to the situation of each section, the above six indicators are evaluated and scored to calculate the risk index P1, see formula (1); Where: P1 is the risk index; γ i is the weight coefficient of the evaluation index; X i is the score of the evaluation index; i is the serial number of the evaluation index; n is the number of evaluation indicators, n = 6; (3) According to the risk index P, the risk level of rockfall and collapse in the assessment section is determined to be G1 according to the table below; 502. Use expert evaluation method based on index system to assess the risk of dangerous rockfall on highways: (1) Invite experts to conduct on-site research, the number of experts n ≥ 5, n is an odd number; (2) The experts' years of experience and professional titles were counted, and the years of experience were divided into three levels: 1 point for less than 10 years, 2 points for more than 10 years and 3 points for more than 20 years. At the same time, it was stipulated that experts with intermediate professional titles were awarded 1 point, 2 points for associate senior professional titles and 3 points for senior professional titles. The scores of each expert were calculated by adding the scores of years of experience and professional titles, and the sum of all experts' scores was further calculated. Finally, the ratio of each expert's score to the sum of all experts' scores was calculated, that is, the expert's weight was obtained; (3) The experts ranked the importance of the six elements of each slope according to the evaluation object, and thus calculated the weights of the six elements of each object by each expert; The weight coefficient calculation formula of the indicator importance ranking method is as follows: Where: γ ij is the weight coefficient of expert i for the jth evaluation index; m is the importance ranking of evaluation indicators by experts, 1≤m≤6; (4) Calculate the risk factor P2 assessed by the expert group. The calculation formula is as follows: Where: i is the expert number; j is the index number; W i is the weight of the i-th expert; γ ij is the weight of the i-th expert on the j-th indicator; X ij is the score given by the i-th expert to the j-th indicator. (5) Determine the risk level of rockfall and collapse in the assessment section to be G2; 503. Use expert survey method to conduct risk assessment of dangerous rockfall on highways: (1) Invite the experts in step 502 to directly assess the risk of dangerous rockfall in the assessment section; (2) The evaluation results of all experts are collected and the collapse and rockfall risk level G3 of the evaluation section is determined by the principle of minority obeying majority; 504. Adopt the principle of high risk rather than low risk, take the highest risk rating, and determine the collapse and rockfall risk level G of the assessment section, as follows: G=MAX(G1,G2,G3) (4)。

Images