Simplified loess earthquake landslide risk evaluation method

Abstract

The invention discloses a simplified loess earthquake landslide risk evaluation method, which comprises the following steps: determining first-level evaluation factors which are necessary conditions for occurrence of landslide and are mutually independent, setting at least one second-level evaluation factor for each first-level evaluation factor, grading the second-level evaluation factors, and assigning risk values to the second-level evaluation factors, and carrying out normalization processing on the risk degree value to calculate a risk index of the loess earthquake landslide, and dividing risk grades. According to the method, the secondary evaluation factor and the risk value and the weight thereof are determined in an open mode, and during specific implementation, the secondary evaluation factor and the risk value and the weight thereof for loess earthquake landslide risk evaluation are autonomously determined according to factors such as evaluation requirements, current research situations, current situations and trends of local earthquake geological disasters, experience of evaluators and the like; reliability, simplicity, convenience and rapidness are realized; the value of the loess earthquake landslide risk index is limited in an interval [0, 1] after the loess earthquake landslide risk index is normalized twice, so that loess earthquake landslide risk evaluation results in different areas have transverse comparability.

Description

Technical Field

[0001] The present invention relates to the field of geological disaster engineering, and in particular to a simplified loess earthquake landslide hazard assessment method. Technical Background

[0002] Loess regions are widely distributed across the globe, particularly in China's Loess Plateau, which boasts the world's largest, thickest, and most complex loess region. Loess slopes inherently present a high landslide risk under natural conditions, and seismic activity significantly exacerbates this risk. A single moderate-to-strong earthquake or greater can trigger numerous loess landslides. Rapidly, reliably, and relatively simply assessing the stability and hazard of loess earthquake landslides is a key challenge in mitigating earthquake hazards in these regions.

[0003] Currently, the evaluation of the risk of loess earthquake landslides and other natural disasters is carried out either through artificial intelligence methods based on statistics or combined with statistical data, or through mechanical calculation methods. Although the methods based on mechanical calculations can obtain results that are more in line with reality, the calculation process is complicated and tedious, highly professional, and not convenient for engineering applications. The methods based on statistics and artificial intelligence either consider too few factors, resulting in distorted results, or consider too many factors, resulting in a complicated process and not convenient for widespread application. For example, Chinese patent document CN202310390150.7 discloses a probabilistic earthquake landslide hazard assessment method considering fault and earthquake motion characteristics. The method calculates the earthquake slope permanent displacement DN of the study area by establishing an earthquake slope permanent displacement model considering the fault properties and earthquake motion characteristics. Then, an earthquake landslide probability-permanent displacement model is established. Then, the earthquake landslide probability value corresponding to the study area DN is calculated to judge the danger of landslide in the study area. The method can be applied to probabilistic earthquake landslide hazard assessment, improve the accuracy of regional earthquake landslide hazard judgment, and provide a basis for slope disaster prevention and mitigation work near (cross) fault areas. However, the calculation process of this method is complicated and tedious, and it is highly professional and inconvenient for engineering applications. Therefore, there is currently no evaluation method that can guarantee a certain degree of reliability and is simple and fast. Summary of the Invention

[0004] The purpose of the present invention is to provide a simplified loess earthquake landslide hazard assessment method to solve the problems of the existing loess earthquake landslide hazard assessment method, such as multiple evaluation factors, cumbersome and complicated evaluation process, and inconvenience in engineering application.

[0005] The method comprises the following steps:

[0006] S1. Determine primary evaluation factors, which are necessary conditions for landslide occurrence and must be independent of each other, wherein the primary evaluation factors include geomorphic conditions, geological conditions, and inducing factors;

[0007] S2. Determine secondary evaluation factors, with each primary evaluation factor having at least one secondary evaluation factor. The secondary evaluation factors are determined based on evaluation requirements, research status, the current status and trend of earthquake and geological hazards in the evaluation area, and the experience of the evaluator.

[0008] S3. Classify the secondary evaluation factors according to their impact on landslide occurrence and assign a hazard value;

[0009] S4. Determine the weights of the primary and secondary rating factors. The primary evaluation factors are equally weighted, i.e., all weights are 1. The secondary evaluation factors are determined using an open weighting method, which can be determined by expert scoring, empirical determination, reference to other research results, or average weighting.

[0010] S5. Calculate the loess earthquake landslide hazard index by normalizing the hazard value, and classify the landslide hazard level according to the loess earthquake landslide hazard index. The loess earthquake landslide hazard index calculation formula is:

[0011]

[0012] Among them, HZ is the loess earthquake landslide hazard index, a ij is the weight of the jth secondary evaluation factor of the i-th first-level evaluation factor, x ij is the risk value of the jth secondary evaluation factor of the ith first-level evaluation factor, n is the number of first-level evaluation factors, and m is the number of second-level evaluation factors.

[0013] Furthermore, in step S2, slope gradient and slope height are selected as secondary evaluation factors of geomorphic conditions, at least one of soil cohesion strength, soil internal friction angle, soil density, soil layer structure, and soil layer age is selected as secondary evaluation factor of geological conditions, and earthquake intensity is selected as secondary evaluation factor of inducing factor, wherein seismic peak acceleration or earthquake intensity is used to represent earthquake intensity, and the coupling effect of earthquake and rainfall can also be selected as secondary evaluation factor of inducing factor.

[0014] Preferably, the hazard value assignment method of the secondary evaluation factor slope gradient is: the slope gradient ≤ 20° has a low hazard level, and is assigned a hazard value of 1; the slope gradient is between 21-40° has a medium hazard level, and is assigned a hazard value of 2; the slope gradient > 40° has a high hazard level, and is assigned a hazard value of 3.

[0015] Preferably, the method for assigning the risk value of the secondary evaluation factor of slope height is as follows: when the slope height ≤ 10m, the risk level is low, and the risk value is assigned 1; when the slope height is between 10 - 50m, the risk level is medium, and the risk value is assigned 2; when the slope height > 50m, the risk level is high, and the risk value is assigned 3.

[0016] Preferably, the method for assigning the risk value of the secondary evaluation factor of soil cohesion strength is as follows: when the soil cohesion strength > 30KPa, the risk level is low, and the risk value is assigned 1; when the soil cohesion strength is between 10 - 30KPa, the risk level is medium, and the risk value is assigned 2; when the soil cohesion strength ≤ 10, the risk level is high, and the risk value is assigned 3.

[0017] Preferably, the method for assigning the risk value of the secondary evaluation factor of soil internal friction angle is as follows: when the soil internal friction angle > 45°, the risk level is low, and the risk value is assigned 1; when the soil internal friction angle is between 10 - 45°, the risk level is medium, and the risk value is assigned 2; when the soil internal friction angle ≤ 10°, the risk level is high, and the risk value is assigned 3.

[0018] Preferably, the method for assigning the risk value of the secondary evaluation factor of soil layer age is as follows: for Q1 loess, the risk level is low, and the risk value is assigned 1; for Q2 loess, the risk level is medium, and the risk value is assigned 2; for Q3 and Q4 loess, the risk level is high, and the risk value is assigned 3.

[0019] Preferably, the method for assigning the risk value of the secondary evaluation factor of earthquake intensity is as follows: when the peak ground acceleration ≤ 0.046g or the seismic intensity ≤ V, the risk level is low, and the risk value is assigned 1; when the peak ground acceleration is between 0.046 - 0.2g or the seismic intensity is between VI - VII, the risk level is medium, and the risk value is assigned 2; when the peak ground acceleration is between 0.2 - 0.41g or the seismic intensity is VIII, the risk level is high, and the risk value is assigned 3; when the peak ground acceleration > 0.41g or the seismic intensity is IX, the risk level is extremely high, and the risk value is assigned 4.

[0020] Furthermore, the risk level of loess earthquake landslides can be determined as three - level or five - level according to the need by using the linear zoning method. If the five - level form is adopted and the interval value is 0.2, the risk levels are shown in Table 4:

[0021] Furthermore, the risk level of the landslide is determined by the linear zoning method and can be divided into three levels or five levels.

[0022] Preferably, the risk level of the landslide is divided into five levels, specifically: 0 < HZ ≤ 0.2 is level 1, 0.2 < HZ ≤ 0.4 is level 2, 0.4 < HZ ≤ 0.6 is level 3, 0.6 < HZ ≤ 0.8 is level 4, 0.8 < HZ ≤ 1 is level 5.

[0023] The beneficial effects of the present invention compared with the prior art:

[0024] In the loess earthquake landslide hazard evaluation method disclosed in the present invention, the secondary evaluation factors are determined based on factors such as the evaluator's needs, research status, local earthquake geological disaster status and trends, and the evaluator's experience, and the weights of the secondary evaluation factors are determined using an open determination method, making the selected evaluation factors and corresponding weights more reliable and convincing; in addition, the hazard value of the primary evaluation factor adopts the form of cumulative and normalized hazard values ​​of the secondary factors, and the loess earthquake landslide hazard index adopts the form of cumulative and normalized primary evaluation factors. After two normalizations, the loess earthquake landslide hazard index value is limited to between 0 and 1. As the value increases, the loess earthquake landslide hazard increases. Therefore, the loess earthquake landslide hazard evaluation results of different regions are horizontally comparable, that is, the evaluation results have a unified scale. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure is a flow chart of the loess earthquake landslide hazard assessment method that can be simplified by the present invention. DETAILED DESCRIPTION

[0026] The present invention is further described below with reference to the accompanying drawings and examples. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those commonly understood by those of ordinary skill in the art to which this application belongs. The use of similar words such as "include" or "comprising" in the present invention means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0027] like Figure 1 As shown, the present invention discloses a simplified method for evaluating the risk of loess earthquake landslides, which includes the following steps:

[0028] S1. Determine the first-level evaluation factors. The first-level evaluation factors are necessary conditions for landslide occurrence and must be independent of each other. The first-level evaluation factors include geomorphic conditions, geological conditions, and inducing factors.

[0029] S2. Determine the secondary evaluation factors. Each primary evaluation factor is set with at least one secondary evaluation factor. The secondary evaluation factors are determined based on the evaluation needs, the current status of research, the current status and trend of earthquake and geological hazards in the evaluation area, and the experience of the evaluator.

[0030] In this embodiment, slope gradient and slope height are selected as the secondary evaluation factors of the first-level rating factor geomorphological conditions, soil cohesion strength and soil internal friction angle are selected as the secondary evaluation factors of the first-level rating factor geological conditions, and earthquake intensity is selected as the secondary evaluation factor of the first-level rating factor inducing factors, where seismic peak acceleration or earthquake intensity is used to represent earthquake intensity.

[0031] S3. Classify the secondary evaluation factors corresponding to the primary rating factors according to their impact on landslide occurrence and assign hazard values, as shown in Tables 1 to 6:

[0032] Geomorphic condition factors:

[0033] Table 1: Slope gradient factor hazard value table

[0034]

[0035]

[0036] Table 2: Slope height factor hazard value table

[0037]

[0038] Geological condition factors:

[0039] Table 3: Hazard degree assignment table for soil cohesion strength factor

[0040]

[0041] Table 4: Hazard value assignment table for soil internal friction angle factor:

[0042]

[0043] If there are no soil cohesion strength and soil internal friction angle values ​​during evaluation, the age of the soil layer can be used as a secondary evaluation factor of the geological conditions. The hazard value is assigned according to the lithologic age of the soil layer. The hazard value of Q1 loess is 1, the hazard value of Q2 loess is 2, and the hazard values ​​of Q3 and Q4 loess are 3, as shown in Table 5:

[0044] Table 5: Hazard value assignment table for soil layer age factors:

[0045]

[0046] Predisposing factors:

[0047] Table 6: Earthquake factor risk assignment table

[0048]

[0049] S4. Determine the weights of the secondary rating factors. The secondary evaluation factors adopt an open - ended weight determination method, and are determined by one of the methods of expert scoring, determination based on experience, reference to other research results, and average weight.

[0050] In this embodiment, the average - weight method is adopted. For the secondary evaluation factors of the geomorphic conditions, only the slope gradient and the slope height are considered, so the weights of the slope gradient and the slope height are both set to 0.5; for the secondary evaluation factors of the geological conditions, only the cohesive strength of the soil mass and the internal friction angle are considered, so the weights of the cohesive strength of the soil mass and the internal friction angle are both set to 0.5; when only the earthquake intensity is considered as the inducing factor, the weight of the earthquake intensity is 1.

[0051] S5. Calculate the loess earthquake landslide hazard index, and divide the landslide hazard level according to the loess earthquake landslide hazard index. The formula for calculating the loess earthquake landslide hazard index is:

[0052]

[0053] where \(H_Z\) is the loess earthquake landslide hazard index, \(a\) ij is the weight of the \(j\) - th secondary evaluation factor of the \(i\) - th primary evaluation factor, \(x\) ij is the hazard degree value of the \(j\) - th secondary evaluation factor of the \(i\) - th primary evaluation factor, \(n\) is the number of primary evaluation factors, and \(m\) is the number of secondary evaluation factors.

[0054] In this embodiment, the landslide hazard level is determined by a linear zoning method, and the landslide hazard level is divided into 5 levels, specifically: \(0\lt H_Z\leq0.2\) is level 1, \(0.2\lt H_Z\leq0.4\) is level 2, \(0.4\lt H_Z\leq0.6\) is level 3, \(0.6\lt H_Z\leq0.8\) is level 4, \(0.8\lt H_Z\leq1\) is level 5, as shown in Table VI:

[0055] Table VI: Loess earthquake landslide hazard level division table

[0056]

[0057] It should be noted that in the embodiments of the present invention, the selection, classification, assignment of hazard degree values, and determination of weights of the secondary evaluation factors are all determined based on the inventor's own cognition, and are the recommended values of the present invention. The present invention adopts an open - ended method to determine the weights and hazard degree values of the secondary evaluation factors. All users of the present invention can independently determine the secondary evaluation factors, their weights, and hazard degree values of the loess earthquake landslide hazard according to factors such as evaluation requirements, research status, local earthquake geological disaster status and trends, and the experience of evaluators.

[0058] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A simplified loess earthquake landslide hazard assessment method, characterized in that: The method comprises the following steps: S1. Determine the primary evaluation factors: the primary evaluation factors are necessary conditions for the occurrence of landslides and must be independent of each other, including geomorphic conditions, geological conditions, and inducing factors; S2. Determine the secondary evaluation factors: set at least one secondary evaluation factor for each primary evaluation factor; S3. Classify the secondary evaluation factors according to their impact on landslide occurrence and assign hazard values; S4. Determine the weights of the primary evaluation factors and the secondary rating factors. The primary evaluation factors are equally weighted, i.e., all are set to 1. The secondary evaluation factors are determined in an open weight determination method, i.e., through expert scoring, determination based on experience, reference to other research results, or average weight determination; S5. Normalize the hazard values ​​of the secondary evaluation factors, calculate the loess earthquake landslide hazard index, and classify the landslide hazard levels according to the loess earthquake landslide hazard index. The calculation formula of the loess earthquake landslide hazard index is: Among them, HZ is the loess earthquake landslide hazard index, a ij is the weight of the jth secondary evaluation factor of the ith first-level evaluation factor, x ij is the hazard value of the jth secondary evaluation factor of the ith first-level evaluation factor, n is the number of first-level evaluation factors, and m is the number of second-level evaluation factors.

2. The loess earthquake landslide hazard assessment method according to claim 1, characterized in that: In step S2, slope gradient and slope height are selected as secondary evaluation factors of geomorphic conditions, at least one of soil cohesion strength, soil internal friction angle, soil density, soil layer structure and soil layer age is selected as secondary evaluation factor of geological conditions, and earthquake intensity is selected as secondary evaluation factor of inducing factor, wherein seismic peak acceleration or earthquake intensity is used to represent earthquake intensity.

3. The loess earthquake landslide hazard assessment method according to claim 2, characterized in that: The method for assigning the hazard value of the secondary evaluation factor slope gradient is as follows: if the slope gradient is ≤20°, the hazard level is low and a hazard value of 1 is assigned; if the slope gradient is between 21-40°, the hazard level is medium and a hazard value of 2 is assigned; if the slope gradient is greater than 40°, the hazard level is high and a hazard value of 3 is assigned.

4. The loess earthquake landslide hazard assessment method according to claim 2, characterized in that: The method for assigning the hazard value of the secondary evaluation factor slope height is as follows: if the slope height is ≤10m, the hazard level is low and a hazard value of 1 is assigned; if the slope height is between 10-50m, the hazard level is medium and a hazard value of 2 is assigned; if the slope height is greater than 50m, the hazard level is high and a hazard value of 3 is assigned.

5. The method for evaluating the hazard level of loess earthquake landslide according to claim 2, characterized in that: The hazard value assignment method for the secondary evaluation factor soil cohesion strength is as follows: if the soil cohesion strength is greater than 30 KPa, the hazard level is low and a hazard value of 1 is assigned; if the soil cohesion strength is between 10-30 KPa, the hazard level is medium and a hazard value of 2 is assigned; if the soil cohesion strength is ≤10, the hazard level is high and a hazard value of 3 is assigned.

6. The loess earthquake landslide hazard assessment method according to claim 2, characterized in that: The hazard value assignment method for the secondary evaluation factor soil internal friction angle is as follows: when the soil internal friction angle is greater than 45°, the hazard level is low and a hazard value of 1 is assigned; when the soil internal friction angle is between 10-45°, the hazard level is medium and a hazard value of 2 is assigned; when the soil internal friction angle is ≤10°, the hazard level is high and a hazard value of 3 is assigned.

7. The loess earthquake landslide hazard assessment method according to claim 2, characterized in that: The hazard value assignment method for the secondary evaluation factor soil layer age is as follows: Q1 loess has a low hazard level and is assigned a hazard value of 1; Q2 loess has a medium hazard level and is assigned a hazard value of 2; Q3 and Q4 loess have a high hazard level and are assigned a hazard value of 3.

8. The loess earthquake landslide hazard assessment method according to claim 2, characterized in that: The method for assigning the risk value of the secondary evaluation factor of earthquake intensity is as follows: when the peak ground acceleration ≤ 0.046g or the seismic intensity ≤ V, the risk level is low, and the risk value is assigned as 1; when the peak ground acceleration is between 0.046 - 0.2g or the seismic intensity is between VI - VII, the risk level is medium, and the risk value is assigned as 2; when the peak ground acceleration is between 0.2 - 0.41g or the seismic intensity is VIII, the risk level is high, and the risk value is assigned as 3; when the peak ground acceleration > 0.41g or the seismic intensity is IX, the risk level is extremely high, and the risk value is assigned as 4.

9. The method for evaluating the hazard of corpus luteum earthquake landslide according to any one of claims 1 to 8, characterized in that: The landslide risk level is determined by a linear zoning method and is divided into 5 levels: 0 < HZ ≤ 0.2 is level 1, 0.2 < HZ ≤ 0.4 is level 2, 0.4 < HZ ≤ 0.6 is level 3, 0.6 < HZ ≤ 0.8 is level 4, and 0.8 < HZ ≤ 1 is level 5.

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