A slope seismic motion comprehensive risk assessment method considering slope-gradient-incidence-angle-fore-and-aft-slope coupling

Abstract

The present application relates to the field of earthquake engineering and geological disaster prevention technology, disclose a kind of slope seismic motion comprehensive risk assessment method considering gradient-incidence angle-back slope surface three-dimensional coupling, by constructing three-dimensional double slope dynamic response model, monitoring point is arranged in the flat ground before slope and two sides slope surface, free field boundary is set around the model, input the seismic wave after polynomial baseline correction processing, the peak acceleration amplification coefficient under different gradient, incidence angle and slope orientation condition is calculated;On this basis, introduce sensitive incidence angle threshold weight and back slope asymmetric weight, and combined with normalized amplification coefficient, construct gradient-incidence angle-back slope surface three-dimensional coupling comprehensive risk index, realize the unified quantification and hierarchical evaluation of risk intensity under different gradient, different incidence angle and different slope conditions.The method can systematically reveal the coupling law of double slope seismic amplification effect, and provide scientific basis for mountainous engineering seismic design and regional seismic risk assessment.

Description

Technical Field

[0001] This invention belongs to the field of earthquake engineering and geological disaster prevention technology, specifically involving a method for assessing the amplification effect of seismic motion based on three-dimensional two-sided slope dynamic numerical simulation, and particularly involving a method for constructing a comprehensive risk index that couples and characterizes slope gradient, seismic wave incident angle, and facing / backward slope orientation. Background Technology

[0002] Mountain slopes often exhibit a significant topographic amplification effect under seismic loading, with increased peak ground acceleration at the slope crest and adjacent areas, potentially triggering secondary disasters such as landslides and collapses. Current technologies generally suffer from the following shortcomings:

[0003] 1. Most studies focus on a single slope range (commonly 30°–60°), with insufficient research on gentle and steep slopes;

[0004] 2. Although the difference in response between the uphill and downhill sides of a double-sided slope has been observed, there is a lack of unified quantitative indicators that can be implemented in engineering.

[0005] 3. The incident angle is significantly affected by the location of the earthquake source and the propagation path. Existing methods often analyze the incident angle and slope separately, which cannot reflect the coupling mechanism and makes it difficult to uniformly compare the risk intensity of different slopes, different incident angles, and different slope surfaces.

[0006] Therefore, there is an urgent need for a unified evaluation method that can simultaneously take into account the three-dimensional factors of "slope, angle of incidence, and uphill and downhill slopes" to support seismic design of engineering projects and earthquake damage assessment in mountainous areas. Summary of the Invention

[0007] This invention aims to overcome the shortcomings of existing technologies and provide a comprehensive risk assessment method for slope ground motion that considers the three-dimensional coupling of slope, incident angle, and facing / backward slope surfaces. It involves constructing a three-dimensional dynamic response model of a two-sided slope, setting corresponding monitoring points on the flat ground in front of the slope and on both sides, establishing free-field boundaries around the model, inputting baseline-corrected seismic waves, and calculating the seismic response at different slope angles. Angle of incidence and slope orientation (Welcoming slope) Back slope The peak ground acceleration (PGA) amplification factor is calculated. Based on this, a threshold weight for sensitive incident angle and an asymmetric weight for the upslope and downslope are introduced. Combined with the normalized amplification factor, a comprehensive risk index is constructed to achieve a three-dimensional coupled risk assessment of slope, incident angle, and upslope and downslope, providing a scientific basis for regional earthquake prevention and disaster reduction.

[0008] To achieve the above objectives, this invention provides a comprehensive risk assessment method for slope seismic ground motion that takes into account the three-dimensional coupling of slope, incident angle, and uphill and downhill surfaces, comprising the following steps:

[0009] S1. Construct a three-dimensional double-sided slope model, with the two sides of the slope symmetrically distributed; set the slope height. ,slope and grid size and define the slope. and back slope A rectangular platform representing flat ground is set at the bottom of the slope; a ground reference point is set on the platform in front of the slope. Multiple monitoring points were set up at equal intervals along the slope on both the uphill and downhill sides. The monitoring points on the uphill side were denoted as follows: The monitoring points on the back slope are recorded as ;

[0010] S2, Selecting the seismic wave acceleration time history As the input load for the model, the original acceleration time history is subjected to second-order polynomial baseline correction before input, so that the integrated velocity and displacement are zero at the end of the recording:

[0011] ;

[0012] ;

[0013] in, For correction functions, and For correction factor, For time, This is the corrected acceleration time history;

[0014] S3. The explicit finite difference method is adopted, and dynamic calculations are performed based on the three-dimensional fast Lagrangian analysis software FLAC3D. The dynamics at each monitoring point are automatically recorded. When performing dynamic calculations on the model, different incident angles are input from the bottom of the model. Seismic waves;

[0015] S4. Calculate the values ​​at each monitoring point on the uphill and downhill slopes respectively. Reference point on flat ground place The ratio of the two slopes is used to obtain the ratio of the slopes on both sides. Magnification factor :

[0016] ;

[0017] in, , indicating the orientation of the slope; Number the monitoring points;

[0018] S5. Calculate the sensitive incident angle weights respectively. Asymmetric weighting of front and back slopes In addition to the normalized amplification factor, the three are coupled to obtain a comprehensive risk index. And based on this, risk classification is carried out.

[0019] Furthermore, in step S1, the model uses the Mohr–Coulomb constitutive model to simulate the mechanical response characteristics of the slope rock mass under the action of seismic waves. The model material parameters are set according to the typical mechanical properties of sandstone. The slope surface that is consistent with the horizontal projection direction of the seismic wave is defined as the back slope, and the slope surface that is opposite to the horizontal projection direction of the seismic wave is defined as the up slope.

[0020] Furthermore, in step S3, a free-field boundary is set around the model to avoid significant reflection or distortion of upward-propagating seismic waves at the boundary; and Rayleigh damping is used to characterize the energy dissipation characteristics of the system under dynamic load, wherein the critical damping ratio is taken as 0.5% commonly used in engineering, and the minimum center frequency is approximated by the natural frequency of the model.

[0021] Furthermore, step S5 specifically includes the following steps:

[0022] S5.1, For each group Using the largest magnification factor in this group Using this as a benchmark, and taking 80% and 90% of this benchmark as thresholds respectively, the incident angles corresponding to the magnification factor within the threshold range are considered as the sensitive incident angles of the slope;

[0023] S5.2 Based on the two thresholds calculated in step S5.1, assign weights to each incident angle according to the following formula, i.e., sensitive incident angle weights. :

[0024] ;

[0025] S5.3 For each slope condition, take the average value of each incident angle on the uphill and downhill surfaces respectively. and Therefore, the asymmetric weights of the uphill and downhill slopes are calculated. ;in:

[0026] ;

[0027] ;

[0028] in, Angle of incidence The number of groups; =1,2,3… , is the monitoring point number; The number of monitoring points; These are calibration coefficients;

[0029] S5.4 Divide the PGA amplification factor by the maximum PGA amplification factor among all operating conditions. The normalized amplification factor was calculated. :

[0030] ;

[0031] S5.5. Sensitive incident angle weights obtained from steps S5.2, S5.3, and S5.4. Asymmetric weighting of front and back slopes With normalized amplification factor The three-dimensional coupled comprehensive risk index of slope, incident angle, and uphill and downhill slopes was calculated. :

[0032] ;

[0033] S5.6. Based on the magnitude of the comprehensive risk index, the corresponding slope area is divided into three levels of risk: low, medium, and high.

[0034] .

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] This invention provides a comprehensive risk assessment method for slope ground motion considering the three-dimensional coupling of slope, incident angle, and uphill and downhill surfaces. It constructs a three-dimensional dynamic response model of a two-sided slope, sets up monitoring points on the flat ground in front of the slope and on both sides, establishes free-field boundaries around the model, inputs seismic waves processed by polynomial baseline correction, and calculates the seismic response at different slope angles. Angle of incidence and slope properties (Welcoming slope) Back slope Peak acceleration under the condition of ) Amplification factor. Based on this, a sensitive incident angle threshold weight and an asymmetric weight for the uphill and downhill slopes are introduced, and combined with a normalized amplification factor, a three-dimensional coupled comprehensive risk index of slope-incident angle-uphill and downhill slope is constructed to achieve unified quantification and graded evaluation of risk intensity under different slope, incident angle, and slope surface conditions. This invention overcomes the shortcomings of existing technologies in multi-factor coupling analysis and constructs a comprehensive risk assessment method for slope ground motion with uniformity, comparability, and engineering feasibility. This method can systematically reveal the coupling law of ground motion amplification effect on two-sided slopes, providing a scientific basis for seismic design of mountainous engineering and regional seismic risk assessment. Specifically:

[0037] 1. This invention creatively incorporates slope Angle of incidence and slope orientation By incorporating a unified evaluation framework, a comprehensive index with three-dimensional coupling of slope, incident angle, and facing and back slopes was constructed, achieving comparability and consistent expression of risk intensity among different working conditions. Furthermore, this invention is applicable to various slope conditions, including gentle slopes, medium slopes, and steep slopes, and is not limited to the common 30° to 60° range. It can comprehensively reflect the seismic motion amplification law under different terrain conditions and improve the coverage of engineering applications.

[0038] 2. This invention sets a threshold weight for the sensitive incident angle. By assigning higher weight to incident angle conditions that are close to the maximum amplification effect, the most unfavorable earthquake incident direction can be highlighted, thereby improving the pertinence and precision of risk identification.

[0039] 3. This invention can quantitatively characterize the asymmetric response features of the upslope and backslope by introducing an asymmetric weighting coefficient for the upslope and backslope. It can effectively quantify the response differences of two-sided slopes under different slope and incident angle conditions, making the evaluation results more meaningful for engineering guidance.

[0040] 4. This invention constructs a hierarchical comprehensive risk index system. The proposed comprehensive risk index T value can be used to divide low, medium and high risk areas, which facilitates earthquake damage zoning and disaster prevention priority ranking at the regional scale and has good engineering operability.

[0041] In addition to the objectives, features, and advantages described above, the present invention has other objectives, features, and advantages. The invention will now be described in further detail with reference to the accompanying drawings. Attached Figure Description

[0042] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0043] Figure 1 This is a flowchart illustrating a preferred embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the model setup and monitoring point layout in a preferred embodiment of the present invention; wherein, (a) is a three-dimensional side view of the model, and (b) is a front view of the model and the bottom input load situation;

[0045] Figure 3 This is a schematic diagram of the process for calculating the comprehensive risk index in a preferred embodiment of the present invention. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the embodiments shown in the accompanying drawings. However, it should be noted that these embodiments are not intended to limit the present invention. Equivalent transformations or substitutions in function, method, or structure made by those skilled in the art based on these embodiments are all within the scope of protection of the present invention.

[0047] Please see Figure 1 This embodiment provides a comprehensive risk assessment method for slope seismic ground motion that takes into account the three-dimensional coupling of slope, incident angle, and uphill and downhill surfaces. Firstly... The model is built and the corresponding deployment is completed within the software. The monitoring points were then used to perform baseline correction on the input El Centro seismic wave acceleration time history using polynomial fitting to remove the influence of low-frequency noise. During the model dynamics calculation, free-field boundaries were set around the model, and Rayleigh damping was applied. After the calculation, the PGA amplification factor at each monitoring point was calculated, and the sensitive incident angle weights were then calculated accordingly. Asymmetric weighting of front and back slopes and normalized amplification factor By coupling the three factors, a comprehensive risk index is obtained. The method involves classifying slopes into low, medium, and high risk levels based on comprehensive risk indicators. Specifically, the method includes the following steps:

[0048] S1. Construct a three-dimensional double-sided slope model, such as Figure 2 As shown, the model consists of two wedge-shaped bodies of equal length and width, L, symmetrically distributed on both sides of the slope. The Mohr-Coulomb constitutive model is used to simulate the mechanical response characteristics of the slope rock mass under seismic wave action, and the model material parameters reference the typical mechanical properties of sandstone. The slope height of the model is set sequentially. =200m, slope =26.6°, 33.7°, 45°, 53.1°, 63.4°, 76°, 81.5°, the mesh size of the model. =10m, and define the slope surface aligned with the horizontal projection direction of the seismic wave as the back slope. The slope opposite to the horizontal projection direction of the seismic wave is the upslope. At the bottom of the slope, there is a rectangular platform representing flat ground, measuring 4L × 3L × 100m. A ground reference point is set on the platform in front of the slope. Eleven monitoring points were evenly spaced along the slope on both the uphill and downhill sides. The monitoring points on the uphill side were denoted as follows: The monitoring points on the back slope are recorded sequentially as follows: .

[0049] S2, Selecting the El Centro seismic wave acceleration time history As the input load for the model, to eliminate baseline drift caused by low-frequency noise, a second-order polynomial baseline correction is performed on the original acceleration time history before input, so that the integrated velocity and displacement are zero at the end of the recording:

[0050] ;

[0051] ;

[0052] in, For correction functions, and For correction factor, For time, This is the corrected acceleration time history.

[0053] S3. The explicit finite difference method is adopted, and dynamic calculations are performed based on the three-dimensional fast Lagrangian analysis software FLAC3D. The dynamics at each monitoring point are automatically recorded. The model is designed with free-field boundaries to prevent significant reflection or distortion of upward-propagating seismic waves at these boundaries. Rayleigh damping is employed to characterize the energy dissipation of the system under dynamic loads, with the critical damping ratio set at 0.5%, a common engineering practice. The minimum center frequency is approximated by the model's natural frequency. During dynamic calculations, different incident angles are input sequentially from the bottom of the model. = Seismic waves at 0°, 10°, 20°, 30°, 40°, 50°, 60°, 70°, and 80°.

[0054] S4. Calculate the PGA and the reference point on flat ground at each monitoring point on the uphill and downhill slopes respectively. The ratio of PGA at each point yields the PGA amplification factor for both slopes. :

[0055] ;

[0056] in, , indicating the orientation of the slope; , is the monitoring point number.

[0057] S5. Calculate the sensitive incident angle weights respectively. Asymmetric weighting of front and back slopes and normalized amplification factor By coupling the three factors, a comprehensive risk index is obtained. This is followed by a risk classification process: low / medium / high risk. The specific steps include:

[0058] S5.1, For each group Using the largest magnification factor in this group Using this as a benchmark, 80% and 90% of this benchmark were used as thresholds. The incident angle corresponding to the magnification factor within the threshold range was considered the sensitive incident angle of the slope, meaning that the magnification effect was significantly enhanced at this incident angle, which required attention. Each group... Includes all of the corresponding numerical simulation experiments and For example, at (26.6°, (This refers to the slope gradient) When the angle of incidence is 26.6°, Take the uphill angles of 0°, 10°, ..., 80° respectively. All the information at each monitoring point. Slope The maximum amplification factor in the numerical simulation experiment corresponding to different values, i.e., each slope gradient. One .

[0059] S5.2 Based on the two thresholds calculated in step S5.1, assign weights to each incident angle according to the following formula, i.e., sensitive incident angle weights. :

[0060] ;

[0061] S5.3 For each slope condition, take the average value of each incident angle on the uphill and downhill surfaces respectively. and Therefore, the asymmetric weights of the uphill and downhill slopes are calculated. ;in:

[0062] ;

[0063] in, , is the angle of incidence. The number of groups; , is the monitoring point number.

[0064] ;

[0065] in, This is the calibration factor, which is usually taken as 0.2 to 0.5.

[0066] S5.4, will The magnification factor divided by the maximum value among all operating conditions Magnification factor ( The maximum value that appears in all numerical simulation experiments The magnification factor, that is It is all The normalized amplification factor is calculated by taking the maximum value in the range. :

[0067] .

[0068] S5.5, The sensitive incident angle weights obtained by combining steps S5.2, S5.3, and S5.4 Asymmetric weighting of front and back slopes With normalized amplification factor The three-dimensional coupled comprehensive risk index of slope, incident angle, and uphill and downhill slopes was calculated. :

[0069] ;

[0070] S5.6. Based on the magnitude of the three-dimensional coupled comprehensive risk index, the corresponding slope area is divided into three levels of risk: low, medium, and high.

[0071] .

[0072] In the embodiments of the present invention, by establishing a unified three-dimensional coupled comprehensive index, the following results are obtained: the slope amplification effect is concentrated at the top of the slope and in the adjacent area; the overall amplification effect of the back slope is stronger than that of the front slope, and the risk is higher; low-slope slopes exhibit a strong amplification effect near a small incident angle, while medium- and high-slope slopes are at higher risk under high incident angle conditions; it is difficult to accurately describe and assess the risk level of a slope area using only a single parameter, while the comprehensive risk index in the present invention can achieve quantitative characterization and risk classification evaluation of the slope seismic amplification effect.

[0073] This invention presents a comprehensive risk assessment method for slope seismic ground motion. By constructing a three-dimensional dynamic numerical model of a two-sided slope, it systematically calculates the amplification factor under different slope angles, seismic wave incident angles, and slope properties. Based on this, it introduces sensitive incident angle weights and asymmetric weights for the uphill and backhill slopes, and combines these with normalization processing to establish a unified three-dimensional coupled comprehensive index. This enables quantitative characterization and risk classification assessment of the slope seismic ground motion amplification effect. It can realistically reflect the response differences of two-sided slopes under complex seismic input conditions, overcoming the shortcomings of multi-factor separation analysis in existing technologies. It has strong engineering applicability and promotional value, and can provide reliable technical support for seismic design of mountainous engineering projects, seismic hazard risk zoning, and disaster prevention and mitigation decision-making.

[0074] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A comprehensive risk assessment method for slope seismic motion considering the three-dimensional coupling of slope, incident angle, and uphill / downhill surfaces, characterized in that, Includes the following steps: S1. Construct a three-dimensional double-sided slope model, with the two sides of the slope symmetrically distributed; set the slope height. ,slope and grid size and define the slope. and back slope A rectangular platform representing flat ground is set at the bottom of the slope; a ground reference point is set on the platform in front of the slope. Multiple monitoring points were set up at equal intervals along the slope on both the uphill and downhill sides. The monitoring points on the uphill side were denoted as follows: The monitoring points on the back slope are recorded as ; S2, Selecting the seismic wave acceleration time history As the input load for the model, the original acceleration time history is subjected to second-order polynomial baseline correction before input, so that the integrated velocity and displacement are zero at the end of the recording: ； ； in, For correction functions, and For correction factor, For time, This is the corrected acceleration time history; S3. The explicit finite difference method is adopted, and dynamic calculations are performed based on the three-dimensional fast Lagrangian analysis software FLAC3D. The dynamics at each monitoring point are automatically recorded. When performing dynamic calculations on the model, different incident angles are input from the bottom of the model. Seismic waves; S4. Calculate the values ​​at each monitoring point on the uphill and downhill slopes respectively. Reference point on flat ground place The ratio of the two slopes is used to obtain the ratio of the slopes on both sides. Magnification factor: ； in, , indicating the orientation of the slope; Number the monitoring points; S5. Calculate the sensitive incident angle weights respectively. Asymmetric weighting of front and back slopes In addition to the normalized amplification factor, the three are coupled to obtain a comprehensive risk index. And based on this, risk classification is carried out.

2. The method for comprehensive risk assessment of slope ground motion according to claim 1, characterized in that, In step S1, the model uses the Mohr–Coulomb constitutive model to simulate the mechanical response characteristics of the slope rock mass under the action of seismic waves. The model material parameters are set according to the typical mechanical properties of sandstone. The slope surface that is consistent with the horizontal projection direction of the seismic wave is defined as the back slope, and the slope surface that is opposite to the horizontal projection direction of the seismic wave is defined as the up slope.

3. The method for comprehensive risk assessment of slope ground motion according to claim 1, characterized in that, In step S3, a free-field boundary is set around the model to avoid significant reflection or distortion of upward-propagating seismic waves at the boundary; and Rayleigh damping is used to characterize the energy dissipation characteristics of the system under dynamic load.

4. The method for comprehensive risk assessment of slope ground motion according to claim 1, characterized in that, Step S5 specifically includes the following steps: S5.1, For each group Using the largest magnification factor in this group Using this as a benchmark, and taking 80% and 90% of this benchmark as thresholds respectively, the incident angles corresponding to the magnification factor within the threshold range are considered as the sensitive incident angles of the slope; S5.2 Based on the two thresholds calculated in step S5.1, assign weights to each incident angle according to the following formula, i.e., sensitive incident angle weights. : ； S5.3 For each slope condition, take the average value of each incident angle on the uphill and downhill sides respectively. and Therefore, the asymmetric weights of the uphill and downhill slopes are calculated. ;in: ； ； in, Angle of incidence The number of groups; =1,2,3… , is the monitoring point number; The number of monitoring points; These are calibration coefficients; S5.4 Divide the PGA amplification factor by the maximum PGA amplification factor among all operating conditions. The normalized amplification factor was calculated. : ； S5.

5. Sensitive incident angle weights obtained from steps S5.2, S5.3, and S5.

4. Asymmetric weighting of front and back slopes With normalized amplification factor The three-dimensional coupled comprehensive risk index of slope, incident angle, and uphill and downhill slopes was calculated. : ； S5.

6. Based on the magnitude of the comprehensive risk index, the corresponding slope area is divided into three levels of risk: low, medium, and high. 。

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