A Probabilistic Analysis-Based Method for Assessing the Risk of Dam Foundation Liquefaction Damage

Abstract

This invention discloses a probabilistic analysis-based method for assessing the risk of liquefaction damage to dam foundations. The method includes establishing seismic motion parameter hazard curves for the dam foundation surface under different working conditions, based on on-site seismic safety assessment reports and considering the compaction effect of crushed stone piles on the dam foundation and the amplification effect of overlying stress on ground stress; plotting spatial distribution maps of soil parameters in the dam foundation soil under different working conditions; selecting a suitable simplified calculation model for liquefaction damage; and performing dam foundation liquefaction damage analysis based on the seismic motion parameter hazard curves and the spatial distribution maps of soil parameters, combined with the simplified calculation model, to obtain seismic liquefaction probability distribution maps of each soil layer under different working conditions. The seismic liquefaction risk of the soil is then assessed based on these probability distribution maps. This invention can effectively guide the seismic design and risk management of dam foundations, comprehensively consider the uncertainties of earthquake, geological, and soil parameters, and contribute to improving the safety and reliability of water conservancy projects.

Description

Technical Field

[0001] This invention belongs to the field of liquefaction identification of saturated sandy soil foundations with deep overburden in earthquake sites, and specifically relates to a method for risk assessment of earthquake damage caused by liquefaction of dam foundations based on probability analysis. Background Technology

[0002] Constructing earth-rock dams directly on thick overburden in high-intensity earthquake zones has become a common practice in water resource development and utilization in western my country. Liquefaction caused by earthquakes is a significant factor leading to dam foundation instability and failure. Historical earthquake events demonstrate that liquefaction can cause significant ground subsidence, cracking, and uneven settlement of the dam body, resulting in severe engineering disasters. Earth-rock dams built on thick overburden are large in scale, with a wide spatial span of the bearing stratum soil. The soil types and their distribution are complex and random, exhibiting strong spatial variability in soil physical and mechanical parameters. Furthermore, the non-uniformity of seismic wave propagation and topographic effects cause complex reflection, refraction, and focusing of seismic waves within the site, resulting in temporal and spatial variations in the seismic motion parameter hazard curve.

[0003] Traditional methods for assessing dam foundation liquefaction risk are primarily based on deterministic analysis. Deterministic dam foundation liquefaction risk assessment algorithms are widely used due to their simplicity and regulatory support. These methods typically rely on empirical or semi-empirical approaches, utilizing soil physical properties and historical earthquake data to evaluate the likelihood and potential impact of liquefaction. However, they fail to consider the spatial variability of soil physical and mechanical parameters and the uncertainty of seismic motion. The determined soil parameter values ​​are generally conservative, and the assumptions regarding external effects such as dam construction, water storage, and earthquakes are overly extreme. Therefore, deterministic analysis methods may lead to significant biases in dam foundation liquefaction risk assessment, offering limited reference value for the liquefaction resistance design of earth-rock dams.

[0004] Given the complexity and uncertainty of earthquake liquefaction, it is particularly important to assess the risk of liquefaction damage to dam foundations using probabilistic analysis methods. Probabilistic analysis can quantify the probability of liquefaction and the potential damage, providing a more scientific and reasonable basis for risk management and decision-making. To more rationally design liquefaction-resistant structures, considering the spatial variability of soil physical and mechanical parameters and the uncertainty of seismic motion, a new spatial analysis method for dam foundation liquefaction damage risk is urgently needed. Summary of the Invention

[0005] In order to address the problems existing in the background art, the purpose of this invention is to provide a method for assessing the risk of dam foundation liquefaction damage based on probability analysis, so as to solve the problem that existing methods for assessing the risk of dam foundation liquefaction cannot reasonably consider the uncertainties of earthquake, geological and soil parameters.

[0006] The technical solution adopted in this invention is as follows, including the following steps:

[0007] Step S1: First, based on the on-site seismic safety assessment report, and considering the compaction effect of the crushed stone piles on the dam foundation and the increase of the overlying stress on the ground stress, establish the hazard curves of the ground motion parameters of the dam foundation surface under different working conditions.

[0008] Step S2: Next, draw the spatial distribution map of soil parameters of the dam foundation soil under different working conditions;

[0009] Step S3: Then, based on the site conditions and the centrifuge shaking table model test, select a suitable simplified calculation model for liquefaction damage.

[0010] Step S4: Based on the hazard curve of the ground motion parameters of the dam foundation surface in Step S1 and the spatial distribution map of the soil parameters obtained in Step S2, and combined with the simplified calculation model of liquefaction damage, the spatial analysis of dam foundation liquefaction damage is carried out using Monte Carlo simulation in the geographic information analysis software GIS, and the mean distribution map and variance distribution map of the seismic liquefaction probability of each layer of soil in the site under different working conditions are obtained.

[0011] Step S5: Finally, using the seismic liquefaction probability P l The mean and variance distribution plots were used to assess the seismic liquefaction risk of soil layers in different real-world conditions.

[0012] Step S1 specifically includes the following steps:

[0013] Step S1.1: Based on the annual average exceedance probability of bedrock peak ground acceleration in the earthquake safety assessment report, plot the bedrock ground motion parameter hazard curve. The vertical axis of the bedrock ground motion parameter hazard curve is the bedrock peak ground acceleration, and the horizontal axis is the annual average exceedance probability corresponding to the bedrock peak ground acceleration.

[0014] Step S1.2: Construct a dam foundation-bedrock model. Use crushed stone piles, overlying stress, and water level to simulate the external environment of the dam foundation-bedrock model under different working conditions to obtain dam foundation-bedrock models under different working conditions. Then, conduct numerical simulation or centrifuge shaking table model tests on the dam foundation-bedrock models under different working conditions. Combined with the bedrock seismic motion parameter hazard curve, plot the dam foundation surface seismic motion parameter hazard curve under different working conditions. The vertical axis of the dam foundation surface seismic motion parameter hazard curve is the peak horizontal acceleration of the dam foundation surface, and the horizontal axis is the annual average exceedance probability corresponding to the peak horizontal acceleration of the dam foundation surface.

[0015] The specific steps of step S2 are as follows:

[0016] Step S2.1: First, obtain the location of each borehole point in the site. Then, conduct geotechnical tests on the soil at each borehole point to obtain the soil layer thickness d and groundwater level z at each borehole point. wThe mean and variance of the soil static and dynamic parameters, including soil density ρ and shear wave velocity V. s The mean and variance of the static and dynamic parameters of the soil layer are obtained by averaging and calculating the variance of the static and dynamic parameters of the soil at different depths in the same soil layer, respectively.

[0017] Step S2.2: Record the soil layer thickness d and groundwater level z at each borehole point. w The mean and variance of the soil static and dynamic parameters were imported into the geographic information analysis software GIS. Using the Kriging interpolation method in GIS, the soil layer thickness d and groundwater level z at all locations on the site were obtained. w The mean and variance of soil static and dynamic parameters are calculated, and a spatial distribution map of soil parameters for each soil layer in the natural site is drawn. The spatial distribution map of soil parameters includes a soil layer thickness distribution map, a groundwater level distribution map, a distribution map of the mean of soil static and dynamic parameters, and a distribution map of the variance of soil static and dynamic parameters.

[0018] Step S2.3: Construct a natural dam foundation-bedrock model. Use crushed stone piles, overlying stress, and water level to simulate the external environment of the dam foundation-bedrock model under different working conditions to obtain dam foundation-bedrock models under different working conditions. Then, conduct numerical simulation or centrifuge shaking table model tests on the dam foundation-bedrock models under different working conditions. Combined with the soil parameter distribution map of each soil layer in the natural site obtained in step S2.2, obtain the spatial distribution map of soil parameters of each soil layer in the site under different working conditions.

[0019] In step S3, the simplified calculation model for liquefaction earthquake damage is expressed as follows:

[0020]

[0021]

[0022]

[0023]

[0024] Among them, P l The soil layer represents the probability of seismic liquefaction; FS represents the soil layer's liquefaction resistance safety factor; CRR is the cyclic stress ratio of the soil layer; CSR is the cyclic resistance ratio of the soil layer; a max σ is the peak horizontal acceleration of the dam foundation surface; g is the gravitational acceleration; σ vc σ represents the total vertical stress experienced by the soil layer. vc ' is the effective stress of the overlying layer; γ d V is the stress stiffness reduction factor for the soil layer. s1 The shear wave velocity is corrected for overlying stress; Vs1 'V' represents the upper limit shear wave velocity for soil liquefaction, when the average clay content FC ≤ 5%. s1 'Take 215 m / s, when FC ≥ 35%, V s1 Take 200 m / s; when 5% < FC < 35%, V s1 It can be calculated using linear interpolation; MSF represents the magnitude scale factor.

[0025] Step S4 specifically involves: First, inputting the hazard curve of the dam foundation surface seismic parameters from step S1 and the spatial distribution map of the soil parameters obtained in step S2 into the geographic information analysis software GIS. Then, in the GIS software, the simplified calculation model for liquefaction damage from step S3 is selected. The simplified calculation model for liquefaction damage is based on the input peak horizontal acceleration of the dam foundation surface, soil layer thickness d, and groundwater level z. w The seismic liquefaction probability P of the soil layer was obtained by processing the static and dynamic parameters of the soil and combining them with Monte Carlo simulation. l Based on the mean and variance of the seismic liquefaction probability of each soil layer at all locations on the site under different working conditions, mean distribution maps and variance distribution maps of the seismic liquefaction probability under different working conditions were drawn respectively.

[0026] Monte Carlo simulation is a numerical method based on random sampling that estimates the probability distribution and statistical properties of the results by simulating the system behavior under different input conditions multiple times.

[0027] The working conditions of the dam foundation-bedrock model include the crushed stone pile construction period, the dam construction period, and the dam service and water storage period. The dam foundation-bedrock model during the crushed stone pile construction period is obtained by simulating the dam foundation in the natural dam foundation-bedrock model by adding crushed stone piles. The dam foundation-bedrock model during the dam construction period is obtained by simulating the dam foundation surface of the crushed stone pile construction dam foundation-bedrock model by applying a given overburden stress. The dam foundation-bedrock model during the dam service and water storage period is obtained by simulating the dam foundation-bedrock model during the dam construction period by applying a given water level.

[0028] In the simplified calculation model for liquefaction earthquake damage, the stress stiffness reduction factor γ of the soil layer is... d The following formula is used to obtain the result:

[0029]

[0030] Where z represents the average depth of the soil layer;

[0031] Shear wave velocity V after overburden stress correction s1 The expression for the magnitude scaling factor (MSF) is as follows:

[0032]

[0033]

[0034] In the formula, V s P is the shear wave velocity; a Atmospheric pressure; M w It is a moment magnitude earthquake.

[0035] This invention considers the uncertainty of seismic motion and the spatial variability of soil parameters. It uses numerical simulation or centrifuge shaking table model tests to study the influence of topographic effects, the inconsistency of seismic motion, and high overburden stress on the static and dynamic parameters of dam foundation soil, as well as the evolution of mechanical properties in the crushed stone pile treatment area of ​​the dam foundation. It statistically analyzes the mean and variance of each parameter at different borehole locations and depths, and establishes the probabilistic spatial distribution of parameters such as soil thickness, groundwater level, soil density, and shear wave velocity in GIS. This invention overcomes the limitation that the original deterministic seismic liquefaction assessment method for sandy soil cannot be applied to dam foundations with deep overburden layers. It provides accurate spatial analysis of the seismic liquefaction risk of dam foundation, improving the accuracy and effectiveness of seismic liquefaction risk assessment for dam foundation soils with deep overburden layers.

[0036] This invention relates to the field of liquefaction assessment of saturated sandy soil dam foundations with deep overburden in earthquake-prone sites. It aims to comprehensively consider the uncertainty of seismic motion, the spatial variability of soil parameters in the dam foundation overburden, and changes in external conditions such as crushed stone pile construction, dam building, and water impoundment to effectively assess the liquefaction risk of dam foundations. The method constructs a time-varying seismic motion parameter hazard curve for the dam foundation surface using probabilistic analysis; establishes a spatiotemporal distribution probability model of the static and dynamic parameters of the dam foundation overburden soil; and, combined with a simplified calculation model for liquefaction damage, establishes a liquefaction damage risk assessment algorithm based on probabilistic analysis, conducts spatial analysis of dam foundation liquefaction damage, and maps the dam foundation seismic liquefaction risk.

[0037] The beneficial effects of this invention are as follows:

[0038] 1. The present invention can quantify the probability of liquefaction by using the probability analysis of seismic motion parameter hazard curves, and can more comprehensively assess the risk of liquefaction damage to dam foundations.

[0039] 2. This invention considers the uncertainty of earthquake motion and the spatial variability of soil parameters. It uses numerical simulation or centrifuge shaking table model tests to study the influence of topographic effects, the inconsistency of earthquake motion, and the high overburden stress on the static and dynamic parameters of dam foundation soil, as well as the evolution of mechanical properties in the crushed stone pile treatment area of ​​dam foundation. This allows us to obtain the static and dynamic parameters of dam foundation under different working conditions (periods), overcoming the limitation that the original deterministic earthquake liquefaction assessment method for sandy soil cannot be applied to dam foundations with deep overburden layers.

[0040] 3. The method of this invention provides a precise spatial analysis of the risk of dam foundation liquefaction damage and introduces the mean and variance of soil static and dynamic parameters. It can effectively guide the seismic design and risk management of dam foundation, and can more comprehensively consider the uncertainties of earthquake, geological and soil parameters. It provides a more scientific and accurate means of assessing the risk of dam foundation liquefaction damage, which helps to improve the safety and reliability of water conservancy projects. Attached Figure Description

[0041] Figure 1 Flowchart of spatial analysis method for dam foundation liquefaction earthquake damage;

[0042] Figure 2 This is an example diagram illustrating the seismic liquefaction risk of each soil layer in the dam foundation during the construction of crushed stone piles in a specific embodiment of the present invention. Detailed Implementation

[0043] The present invention will be described in detail below with reference to specific implementation examples. These examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way.

[0044] A probability analysis-based method for assessing the risk of liquefaction damage to dam foundations is proposed. The main technical approach is as follows: using numerical simulation or centrifuge shaking table model tests to study the topographic effects and inconsistencies of ground motion, the influence of high overburden stress on the static and dynamic parameters of the dam foundation soil, and the evolution of mechanical properties in the crushed stone pile treatment area of ​​the dam foundation. When drawing GIS maps, based on the mean and variance distribution maps of soil parameters, combined with Monte Carlo simulation methods, considering the uncertainty of ground motion and the spatiotemporal variability of soil parameters, the mean and variance distribution maps of the liquefaction risk index are obtained.

[0045] like Figure 1 As shown, the steps of this embodiment of the invention are as follows:

[0046] like Figure 1 As shown in the flowchart, the method of the present invention includes the following steps:

[0047] Step S1: Collect historical earthquake records, geological survey reports, and geotechnical test data of the bedrock in the dam site area; compile the collected historical earthquake records into an earthquake safety assessment report; based on the earthquake safety assessment report, and considering the compaction effect of the crushed stone piles on the dam foundation and the effect of the overlying stress on the increase of the ground stress, establish the hazard curves of the ground motion parameters of the dam foundation surface under different working conditions.

[0048] Step S2: Next, draw the spatial distribution map of soil parameters of the dam foundation soil under different working conditions;

[0049] Step S3: Then, based on the site conditions and the centrifuge shaking table model test, select a suitable simplified calculation model for liquefaction damage.

[0050] Step S4: Based on the hazard curve of the ground motion parameters of the dam foundation surface in Step S1 and the spatial distribution map of the soil parameters obtained in Step S2, and combined with the simplified calculation model of liquefaction damage, the spatial analysis of dam foundation liquefaction damage is carried out using Monte Carlo simulation in the geographic information analysis software GIS, and the mean distribution map and variance distribution map of the seismic liquefaction probability of each layer of soil in the site under different working conditions are obtained.

[0051] Step S5: Finally, using the seismic liquefaction probability P l The mean and variance distribution plots were used to assess the seismic liquefaction risk of soil layers in different working conditions.

[0052] Step S5.1: Based on the seismic liquefaction probability P of the dam foundation under each working condition generated in the above steps... l The mean and variance distribution plots were used to assess the liquefaction of the dam foundation. The assessment principles are as follows:

[0053] 0≤P l <0.3, does not liquefy;

[0054] 0.3≤P l <0.7, may liquefy;

[0055] 0.7≤P l <1.0, liquefaction;

[0056] Step S5.2: Based on the evaluation results of step S5.1, focus on the liquefaction location (0.7 ≤ P). l <1.0), propose reinforcement measures and earthquake emergency management plans.

[0057] Step S1 specifically includes the following steps:

[0058] Step S1.1: Based on the annual average exceedance probability of bedrock peak ground acceleration in the earthquake safety assessment report, plot the bedrock ground motion parameter hazard curve. The vertical axis of the bedrock ground motion parameter hazard curve is the bedrock peak ground acceleration, and the horizontal axis is the annual average exceedance probability corresponding to the bedrock peak ground acceleration.

[0059] Step S1.2: Construct a dam foundation-bedrock model. Use crushed stone piles, overlying stress, and water level to simulate the external environment of the dam foundation-bedrock model under different working conditions to obtain dam foundation-bedrock models under different working conditions. Then, conduct numerical simulation or centrifuge shaking table model tests on the dam foundation-bedrock models under different working conditions. Combined with the bedrock seismic motion parameter hazard curve, plot the dam foundation surface seismic motion parameter hazard curve under different working conditions. The vertical axis of the dam foundation surface seismic motion parameter hazard curve is the peak horizontal acceleration of the dam foundation surface, and the horizontal axis is the annual average exceedance probability corresponding to the peak horizontal acceleration of the dam foundation surface.

[0060] Specifically, adding crushed stone piles to the dam foundation in the natural dam foundation-bedrock model can simulate the compaction effect of the crushed stone piles on the dam foundation, thus obtaining the dam foundation-bedrock model during the crushed stone pile construction period. By conducting numerical simulations or centrifuge shaking table model tests on the dam foundation-bedrock models under the above different working conditions, the propagation law of seismic ground acceleration with different annual average exceedance probabilities under different working conditions in the dam foundation soil can be obtained. Then, based on the propagation law of seismic ground acceleration in the dam foundation soil, the peak ground acceleration at the dam foundation surface under different working conditions can be obtained, and the seismic ground motion parameter hazard curve of the dam foundation surface can be plotted.

[0061] Step S2 is as follows:

[0062] Step S2.1: First, obtain the location of each borehole point in the site. Then, conduct geotechnical tests on the soil at each borehole point to obtain the soil layer thickness d and groundwater level z at each borehole point. w The mean and variance of the soil's static and dynamic parameters, including soil density ρ and shear wave velocity V. s The mean and variance of the static and dynamic parameters of the soil layer are obtained by calculating the average and variance of the static and dynamic parameters of the soil at different depths in the same soil layer, respectively.

[0063] Geotechnical test data includes soil thickness d and groundwater level z. w Soil density ρ, shear wave velocity V s Parameters such as soil thickness z and groundwater level z w Generally, the data is obtained directly from borehole data. Soil density ρ and shear wave velocity Vs are generally obtained from multiple sets of indoor and outdoor tests. These soil parameters obtained from different borehole locations and depths are statistically analyzed to obtain the mean and variance of soil density ρ and shear wave velocity Vs at different borehole locations and depths. The data are then imported into GIS and Kriging interpolation is used to generate the mean and variance distribution maps of natural dam foundation soil parameters at different depths.

[0064] Step S2.2: Record the soil layer thickness d and groundwater level z at each borehole point. w The mean and variance of the soil static and dynamic parameters were imported into the geographic information analysis software GIS. Using the Kriging interpolation method in GIS, the soil layer thickness d and groundwater level z at all locations on the site were obtained. w The mean and variance of soil static and dynamic parameters are calculated, and a spatial distribution map of soil parameters for each soil layer in the natural site is drawn. The spatial distribution map of soil parameters includes a soil layer thickness distribution map, a groundwater level distribution map, a distribution map of the mean of soil static and dynamic parameters, and a distribution map of the variance of soil static and dynamic parameters.

[0065] Specifically, the soil parameter distribution map is an RGB two-dimensional image. Each pixel in the image represents the horizontal position of each soil layer in the site, and color represents the soil layer thickness, groundwater level, and the mean / variance values ​​of the soil static and dynamic parameters. The compaction effect of the crushed stone piles during the stone pile construction process affects the static and dynamic parameters of the dam foundation soil. The high overburden stress generated during dam construction and water impoundment during the dam's service life also increases the ground stress, affecting the static and dynamic parameters of the dam foundation soil. This influence is studied through numerical simulation or centrifuge shaking table model tests. Considering the effects of crushed stone pile construction, dam construction, and water impoundment, based on the mean and variance distribution maps of the natural dam foundation soil static and dynamic parameters established in the above steps, mean and variance distribution maps of the dam foundation soil static and dynamic parameters are established for each stage of crushed stone pile construction, dam construction, and water impoundment during the dam's service life.

[0066] Step S2.3: Construct a natural dam foundation-bedrock model. Use crushed stone piles, overlying stress, and water level to simulate the external environment of the dam foundation-bedrock model under different working conditions to obtain dam foundation-bedrock models under different working conditions. Then, conduct numerical simulation or centrifuge shaking table model tests on the dam foundation-bedrock models under different working conditions. Combined with the soil parameter distribution map of each soil layer in the natural site obtained in step S2.2, obtain the spatial distribution map of soil parameters of each soil layer in the site under different working conditions.

[0067] In step S3, the simplified calculation model for liquefaction earthquake damage is expressed as follows:

[0068]

[0069]

[0070]

[0071]

[0072] Among them, P l The soil layer represents the probability of seismic liquefaction; FS represents the soil layer's liquefaction resistance safety factor; CRR is the cyclic stress ratio of the soil layer; CSR is the cyclic resistance ratio of the soil layer; a max σ is the peak horizontal acceleration of the dam foundation surface; g is the gravitational acceleration; σ vc σ represents the total vertical stress experienced by the soil layer. vc ' is the effective stress of the overlying layer; γ d V is the stress stiffness reduction factor for the soil layer. s1 The shear wave velocity is corrected for overlying stress; V s1 'V' represents the upper limit shear wave velocity for soil liquefaction, when the average clay content FC ≤ 5%. s1 'Take 215 m / s, when FC ≥ 35%, V s1Take 200 m / s; when 5% < FC < 35%, V s1 It can be calculated using linear interpolation; MSF represents the magnitude scale factor.

[0073] In the simplified calculation model for liquefaction earthquake damage, the stress stiffness reduction factor γ of the soil layer is... d The following formula is used to obtain the result:

[0074]

[0075] Where z represents the average depth of the soil layer;

[0076] Shear wave velocity V after overburden stress correction s1 The expression for the magnitude scaling factor (MSF) is as follows:

[0077]

[0078]

[0079] In the formula, V s P is the shear wave velocity; a Atmospheric pressure; M w It is a moment magnitude earthquake.

[0080] Step S4 specifically involves: First, inputting the hazard curve of the dam foundation surface seismic parameters from step S1 and the spatial distribution map of the soil parameters obtained in step S2 into the geographic information analysis software GIS. Then, in the GIS software, the simplified calculation model for liquefaction damage from step S3 is selected. The simplified calculation model for liquefaction damage is based on the input peak horizontal acceleration of the dam foundation surface, soil layer thickness d, and groundwater level z. w The seismic liquefaction probability P of the soil layer was obtained by processing the static and dynamic parameters of the soil and combining them with Monte Carlo simulation. l Based on the mean and variance of the seismic liquefaction probability of each soil layer at all locations under different working conditions, mean distribution maps and variance distribution maps of the seismic liquefaction probability under different working conditions were drawn, such as... Figure 2 As shown, Figure 2 The left figure shows the distribution of the mean liquefaction probability. Figure 2 The right figure shows the variance distribution of the liquefaction probability, where the soil density is used to calculate the total vertical stress σ on the soil layer. vc .

[0081] The working conditions of the dam foundation-bedrock model include the crushed stone pile construction period, the dam construction period, and the dam service and water storage period. The dam foundation-bedrock model during the crushed stone pile construction period is obtained by simulating the dam foundation in the natural dam foundation-bedrock model by adding crushed stone piles. The dam foundation-bedrock model during the dam construction period is obtained by simulating the dam foundation surface of the crushed stone pile construction dam foundation-bedrock model by applying a given overburden stress. The dam foundation-bedrock model during the dam service and water storage period is obtained by simulating the dam foundation-bedrock model during the dam construction period by applying a given water level.

[0082] The above description is merely a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for assessing the risk of dam foundation liquefaction earthquake damage based on probabilistic analysis, characterized in that, Includes the following steps: Step S1: First, based on the on-site seismic safety assessment report, and considering the compaction effect of the crushed stone piles on the dam foundation and the increase of the overlying stress on the ground stress, establish the hazard curves of the ground motion parameters of the dam foundation surface under different working conditions. Step S2: Next, draw the spatial distribution map of soil parameters of the dam foundation soil under different working conditions; Step S3: Then, based on the site conditions and the centrifuge shaking table model test, select a suitable simplified calculation model for liquefaction damage. Step S4: Based on the hazard curve of the ground motion parameters of the dam foundation surface in Step S1 and the spatial distribution map of the soil parameters obtained in Step S2, and combined with the simplified calculation model of liquefaction damage, the spatial analysis of dam foundation liquefaction damage is carried out using Monte Carlo simulation in the geographic information analysis software GIS, and the mean distribution map and variance distribution map of the seismic liquefaction probability of each layer of soil in the site under different working conditions are obtained. Step S5: Finally, using the seismic liquefaction probability P l The mean and variance distribution plots are used to assess the seismic liquefaction risk of soil layers in different working conditions. In step S3, the simplified calculation model for liquefaction earthquake damage is expressed as follows: Among them, P l The soil layer represents the probability of seismic liquefaction; FS represents the soil layer's liquefaction resistance safety factor; CRR is the cyclic stress ratio of the soil layer; CSR is the cyclic resistance ratio of the soil layer; a max σ is the peak horizontal acceleration of the dam foundation surface; g is the gravitational acceleration; σ vc σ represents the total vertical stress experienced by the soil layer. vc ' is the effective stress of the overlying layer; γ d V is the stress stiffness reduction factor for the soil layer. s1 The shear wave velocity is corrected for overburden stress; V s1 ' represents the upper limit of shear wave velocity at which soil liquefaction occurs; MSF represents the magnitude scale factor.

2. The method for assessing the risk of dam foundation liquefaction earthquake damage based on probabilistic analysis according to claim 1, characterized in that: Step S1 specifically includes the following steps: Step S1.1: Based on the annual average exceedance probability of bedrock peak ground acceleration in the earthquake safety assessment report, plot the bedrock ground motion parameter hazard curve. The vertical axis of the bedrock ground motion parameter hazard curve is the bedrock peak ground acceleration, and the horizontal axis is the annual average exceedance probability corresponding to the bedrock peak ground acceleration. Step S1.2: Construct a dam foundation-bedrock model. Use crushed stone piles, overlying stress, and water level to simulate the external environment of the dam foundation-bedrock model under different working conditions to obtain dam foundation-bedrock models under different working conditions. Then, conduct numerical simulation or centrifuge shaking table model tests on the dam foundation-bedrock models under different working conditions. Combined with the bedrock seismic motion parameter hazard curve, plot the dam foundation surface seismic motion parameter hazard curve under different working conditions. The vertical axis of the dam foundation surface seismic motion parameter hazard curve is the peak horizontal acceleration of the dam foundation surface, and the horizontal axis is the annual average exceedance probability corresponding to the peak horizontal acceleration of the dam foundation surface.

3. The method for assessing the risk of dam foundation liquefaction earthquake damage based on probabilistic analysis according to claim 1, characterized in that: The specific steps of S2 are as follows: Step S2.1: First, obtain the location of each borehole point in the site. Then, conduct geotechnical tests on the soil at each borehole point to obtain the soil layer thickness d and groundwater level z at each borehole point. w The mean and variance of the soil static and dynamic parameters, including soil density ρ and shear wave velocity V. s The mean and variance of the static and dynamic parameters of the soil layer are obtained by averaging and calculating the variance of the static and dynamic parameters of the soil at different depths in the same soil layer, respectively. Step S2.2: Record the soil layer thickness d and groundwater level z at each borehole point. w The mean and variance of the soil static and dynamic parameters were imported into the geographic information analysis software GIS. Using the GIS software, the soil layer thickness d and groundwater level z of each soil layer at all locations of the site were obtained. w The mean and variance of soil static and dynamic parameters are calculated, and a spatial distribution map of soil parameters for each soil layer in the natural site is drawn. The spatial distribution map of soil parameters includes a soil layer thickness distribution map, a groundwater level distribution map, a distribution map of the mean of soil static and dynamic parameters, and a distribution map of the variance of soil static and dynamic parameters. Step S2.3: Construct a natural dam foundation-bedrock model. Use crushed stone piles, overlying stress, and water level to simulate the external environment of the dam foundation-bedrock model under different working conditions to obtain dam foundation-bedrock models under different working conditions. Then, conduct numerical simulation or centrifuge shaking table model tests on the dam foundation-bedrock models under different working conditions. Combined with the soil parameter distribution map of each soil layer in the natural site obtained in step S2.2, obtain the spatial distribution map of soil parameters of each soil layer in the site under different working conditions.

4. The method for assessing the risk of dam foundation liquefaction earthquake damage based on probabilistic analysis according to claim 1, characterized in that: Step S4 specifically involves: First, inputting the hazard curve of the dam foundation surface seismic parameters from step S1 and the spatial distribution map of the soil parameters obtained in step S2 into the geographic information analysis software GIS. Then, in the GIS software, the simplified calculation model for liquefaction damage from step S3 is selected. The simplified calculation model for liquefaction damage is based on the input peak horizontal acceleration of the dam foundation surface, soil layer thickness d, and groundwater level z. w The seismic liquefaction probability P of the soil layer was obtained by processing the static and dynamic parameters of the soil. l Based on the mean and variance of the seismic liquefaction probability of each soil layer at all locations on the site, mean distribution maps and variance distribution maps of the seismic liquefaction probability under different working conditions were drawn.

5. The method for assessing the risk of dam foundation liquefaction earthquake damage based on probabilistic analysis according to claim 2, characterized in that: The working conditions of the dam foundation-bedrock model include the crushed stone pile construction period, the dam construction period, and the dam service and water storage period. The dam foundation-bedrock model during the crushed stone pile construction period is obtained by simulating the dam foundation in the natural dam foundation-bedrock model by adding crushed stone piles. The dam foundation-bedrock model during the dam construction period is obtained by simulating the overburden stress on the dam foundation surface of the dam foundation-bedrock model during the crushed stone pile construction period. The dam foundation-bedrock model during the dam service and water storage period is obtained by simulating the dam foundation-bedrock model during the dam construction period by applying a given water level.

6. The method for assessing the risk of dam foundation liquefaction earthquake damage based on probabilistic analysis according to claim 1, characterized in that: In the simplified calculation model for liquefaction earthquake damage, the stress stiffness reduction factor γ of the soil layer is... d The following formula is used to obtain the result: Where z represents the average depth of the soil layer; Shear wave velocity V after overburden stress correction s1 The expression for the magnitude scaling factor (MSF) is as follows: In the formula, V s P is the shear wave velocity; a Atmospheric pressure; M w It is a moment magnitude earthquake.

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