Earthquake motion field simulation method based on river valley field terrain effect

Abstract

The invention relates to a ground motion field simulation method based on a river valley site terrain effect, which is mainly applied to the field of slope anti-seismic analysis of water-power engineering. The method comprises the following steps: firstly, aiming at topographic features of a symmetric V-shaped river valley, constructing a planar model by combining a cylindrical SH wave theory, obtaining a seismic wave propagation rule and scattering characteristics by solving a wave field structure, and verifying a topographic amplification effect by utilizing actually measured data; and carrying out seismic oscillation execution foundation terrain simulation, flood discharge tunnel outlet slope simulation and landslide accumulation body simulation in three stages. According to the method, three types of simulation results are integrated, and the most unfavorable seismic oscillation input scheme for engineering anti-seismic analysis is determined, wherein seismic oscillation peak acceleration data of the wave-facing side during horizontal incidence are adopted by a flood discharge tunnel outlet slope and a landslide accumulation body. By means of the method, efficient coupling simulation of the river valley terrain effect and the non-uniform seismic oscillation field is achieved, and theoretical support is provided for aseismic design of complex site slopes.

Description

Technical Field

[0001] This application relates to the field of seismic wave simulation technology, and in particular to a method for simulating seismic ground motion based on the topographic effects of river valley sites. Background Technology

[0002] The downstream spillway outlet of the Gushui Hydropower Station passes through the lower part of the Zhenggang landslide deposit. The outlet slope is adjacent to the Zhenggang landslide deposit, which has a massive volume. Currently, under heavy rainfall conditions, the slope is close to its limit equilibrium state. As this area is located in a typical high mountain valley, the dynamic stability of the slope under strong seismic loads requires close attention.

[0003] To analyze the topographic effects caused by valley site factors during seismic motion, there is an urgent need for a seismic motion simulation method for valley sites that can analyze the seismic wave propagation model and seismic wave scattering law for symmetrical V-shaped valley sites and consider the topographic amplification effect. It is necessary to obtain a better topographic fusion model in the topographic effects of the spillway outlet slope and the landslide deposit, so as to realize a reasonable and efficient simulation of the non-uniform seismic field of valley sites that takes into account the topographic effect, and provide seismic motion input for slope seismic analysis. Summary of the Invention

[0004] To achieve the above objectives, this application provides the following technical solution: According to a first aspect of the present invention, the present invention claims protection for a method for simulating seismic fields based on the topographic effects of a river valley site, comprising: Based on the properties of the symmetrical V-shaped valley site, a planar model of the symmetrical V-shaped valley site is constructed to obtain the seismic wave propagation model and scattering law of the symmetrical V-shaped valley site. Based on the topographic amplification effect, a first ground motion simulation was performed on the valley site; a second ground motion simulation was performed on the valley site based on the topographic effect of the spillway outlet slope; and a third ground motion simulation was performed on the valley site based on the topographic effect of the Zhenggang landslide deposit. Based on the simulation results of the first, second, and third ground motion simulations, the ground motion input for the ground motion field simulation is constructed.

[0005] Furthermore, the process of constructing a planar model of the symmetrical V-shaped valley site based on its attribute characteristics to obtain the seismic wave propagation model and scattering law of the symmetrical V-shaped valley site also includes: Based on the property characteristics of the symmetrical V-shaped valley site, and combined with the cylindrical SH wave, a planar model of the symmetrical V-shaped valley site is constructed. Obtain the wave field structure of the planar model, and solve the wavelength structure to obtain the theoretical solution of the boundary value problem; The theoretical solution is degenerate-verified based on the asymptotic equivalence between far-field cylindrical waves and plane waves, and the amplification factor is obtained. The amplification effect of the measured earthquakes in the sample river valley is used to verify the amplification factor; The seismic wavefront bending effect of the valley site is obtained based on the verified amplification factor, which serves as the scattering law of the valley site.

[0006] Furthermore, the step of simulating the first seismic motion of the valley site based on the topographic amplification effect also includes: First ground motion data of bedrock ground motion is obtained, and fast Fourier transform is performed on the first acceleration time history and the second displacement time history of the first ground motion data to obtain the Fourier spectrum. The theory of seismic wave propagation in valley sites is obtained, and the frequency domain topographic effect transfer function is calculated by combining the Fourier spectrum. The second seismic data of the valley site is obtained, and combined with the frequency domain topographic effect transfer function, a fast Fourier transform is performed to obtain the second displacement time history and the second acceleration time history, thus completing the first seismic simulation of the valley site.

[0007] Furthermore, the second seismic motion simulation of the valley site based on the topographic effect of the spillway outlet slope also includes: Obtain the slope engineering characteristics of the outlet of the flood discharge tunnel, and obtain the slope instability and failure mode of the valley site based on the slope engineering characteristics; A slope calculation model of the spillway outlet is constructed, and the sample collection points of the slope and the ground motion time history and PGA magnification of the sample collection points are obtained. The first calculation results for horizontal and oblique incidence of seismic waves are calculated sequentially to determine the peak ground acceleration amplification factor and the third acceleration time history of each sample collection point.

[0008] Furthermore, the third ground motion simulation of the valley site based on the topographic effect of the landslide deposit also includes: Obtain the engineering characteristics of the landslide deposit, and based on the engineering characteristics of the landslide, obtain the landslide geomorphological characteristics of the valley site; A computational model of the landslide deposit was constructed to obtain the sample collection points and the ground motion time history and PGA magnification of the sample collection points. The second calculation results for horizontal and oblique incidence of seismic waves are calculated sequentially to determine the peak ground acceleration amplification factor and the fourth acceleration time history of each sample collection point.

[0009] Furthermore, the step of constructing the seismic input for the seismic field simulation based on the simulation results of the first, second, and third seismic motion simulations also includes: When the seismic waves are incident horizontally or obliquely, and the exit slope is located on the wave-facing side, determine the difference in peak ground acceleration at each sample collection point compared to a flat site, and determine the seismic motion input to be used in the project: The seismic input used to determine the location of each sample collection point on the exit slope was the wavefront result under horizontal incidence. When seismic waves are incident horizontally and obliquely, determine the difference in peak ground acceleration at the calculation point location on the wave-facing side of the landslide debris slope compared to a flat site, and determine the seismic input to be used in the project: The seismic input at all sample collection points on the slope of the Zhenggang landslide deposit was based on the wave-facing side results under horizontal incidence.

[0010] This invention relates to a seismic ground motion simulation method based on the topographic effects of river valley sites, primarily applied to the seismic analysis of slopes in hydropower engineering projects. The method first constructs a planar model based on the topographic features of a symmetrical V-shaped river valley, combining cylindrical SH wave theory. By solving the wavefield structure, the propagation laws and scattering characteristics of seismic waves are obtained. Measured data are used to verify the topographic amplification effect. The method implements three stages of seismic ground motion simulation: foundation topography simulation, spillway outlet slope simulation, and landslide accumulation body simulation. This invention integrates the results of these three types of simulations to determine the most unfavorable seismic ground motion input scheme for engineering seismic analysis: peak ground acceleration data on the wave-facing side of both the spillway outlet slope and the landslide accumulation body are used during horizontal incidence. This method achieves efficient coupling simulation of river valley topographic effects and non-uniform seismic ground motion fields, providing theoretical support for the seismic design of slopes in complex sites. Attached Figure Description

[0011] Figure 1 A flowchart illustrating the seismic field simulation method based on the topographic effect of a river valley site, as claimed in this application. Figure 2 A symmetrical V-shaped valley model excited by a line source cylindrical wave, which is a ground motion field simulation method based on the topographic effect of a valley site, as claimed in the embodiments of this application. Figure 3 Force diagram of a unit thickness micro-element in cylindrical coordinates for a seismic field simulation method based on valley site topography effect claimed in this application embodiment; Figure 4 A schematic diagram of the time history of a sample valley ground motion acceleration simulation method based on the topographic effect of a valley site, as claimed in an embodiment of this application. Figure 5Snapshots of a symmetrical V-shaped valley at different times, representing a seismic field simulation method based on valley site topography effects claimed in this application. Figure 6 A simplified V-shaped valley calculation model of the outlet slope of a ground motion field simulation method based on valley site topography, which is claimed in the embodiments of this application. Detailed Implementation

[0012] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0013] The terms "first," "second," and "third" in this application are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movements between components in a specific orientation (as shown in the figures). If the specific orientation changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or devices.

[0014] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0015] According to a first aspect of the present invention, the present invention claims protection for a method for simulating seismic fields based on the topographic effects of a river valley site, referring to... Figure 1 ,include: Based on the properties of the symmetrical V-shaped valley site, a planar model of the symmetrical V-shaped valley site is constructed to obtain the seismic wave propagation model and scattering law of the symmetrical V-shaped valley site. Based on the topographic amplification effect, a first ground motion simulation was performed on the valley site; a second ground motion simulation was performed on the valley site based on the topographic effect of the spillway outlet slope; and a third ground motion simulation was performed on the valley site based on the topographic effect of the Zhenggang landslide deposit. Based on the simulation results of the first, second, and third ground motion simulations, the ground motion input for the ground motion field simulation is constructed.

[0016] Furthermore, the process of constructing a planar model of the symmetrical V-shaped valley site based on its attribute characteristics to obtain the seismic wave propagation model and scattering law of the symmetrical V-shaped valley site also includes: Based on the property characteristics of the symmetrical V-shaped valley site, and combined with the cylindrical SH wave, a planar model of the symmetrical V-shaped valley site is constructed. In this embodiment, the considered symmetrical V-shaped valley two-dimensional model is as follows: Figure 2 As shown, the half-width of the valley is b Depth is d The model medium is assumed to be elastic, isotropic, and homogeneous, i.e., with a shear modulus of... G and shear wave velocity Vs It is a constant.

[0017] For simple valley terrains whose shape can be directly described using polar coordinates, such as semi-circular valleys, after considering the boundary conditions to form a definite solution problem, the homogeneous Helmholtz equation can be directly solved using the general method of separation of variables to obtain the solution. However, for symmetrical V-shaped valleys, neither rectangular coordinates nor polar coordinates can directly describe them.

[0018] To address this problem, we propose a two-step strategy of region decomposition and region matching. The solution involves first decomposing the entire region into several sub-regions conforming to a polar coordinate system. In each sub-region, the equations of motion are solved to obtain the corresponding wavefield (containing unknown coefficients). Then, the wavefields of each sub-region are matched at the boundary, and the unknown coefficients are solved using the boundary conditions, thereby obtaining the wavefield solution for the entire region.

[0019] The displacement response at any location in the valley site under excitation by cylindrical SH waves of different frequencies was obtained. u ( r,θ,ω This is a complex number containing both amplitude and phase information. To examine the terrain effect, its amplitude is divided by the amplitude of the free field in a terrain-free half-space, thus obtaining the amplification factor. u | / | u fDefine the dimensionless frequency of the incident wave in a symmetric V-shaped valley model. η = 2 b / λ s ( λ s (representing the incident wave wavelength), in depth d = 1km, half width b Taking a symmetrical V-shaped valley of 1 km as an example, with a dimensionless frequency of η = 1 different source locations ( x 0, y 0) The generated cylindrical waves and different angles α Under plane wave excitation, the calculated ground motion amplification factor is as follows: Figure 3 As shown in the figure. The results indicate that, under vertical incidence, the cylindrical wave generated by a source at a depth of 100 km agrees well with the plane wave results. Under oblique incidence, the cylindrical wave at an epicentral distance of 50 km and a source depth of 50 km is consistent with the plane wave. Under horizontal incidence, the cylindrical wave at an epicentral distance of 20 km and a source depth of 1 km is consistent with the plane wave. However, when the source is closer to the valley, the results for the cylindrical wave (dashed line) differ from those for the plane wave (solid line). This suggests that the wave field in the valley under plane wave incidence is a special case of cylindrical wave incidence.

[0020] The amplification effect of the measured earthquakes in the sample river valley is used to verify the amplification factor; In this embodiment, a ground motion array consisting of six strong-motion meters was installed at a cross-section of the sample valley approximately 300m from the Emerald Dam. Figure 4 The earthquake had a magnitude of ML of 5.5, a focal depth of 50 km, and an epicentral distance of approximately 130 km. Significant differences were found in the SH waves measured by the six seismographs. Specifically, strong-motion seismograph SC1 was located on the left side of the valley, at an altitude of 170 m above the valley floor; strong-motion seismograph SC4 was located on the right side of the valley, at an altitude of 70 m above the valley floor. The peak ground acceleration recorded by SC1 was 2.69 times that of SC4.

[0021] The sample valley can be simplified into a symmetrical V-shaped valley. Figure 4 According to data reported by Huang&Chiu, the model parameters are as follows: width 2 b = 1500m, depth d = 350m, medium density ρ = 2.67 g / cm3, shear wave velocity V s = 1500m / s, the location of the earthquake source is ( x 0, y 0) = (-130km, 50km).

[0022] Reference Figure 4 Due to the lack of sample earthquake input, the nearby Jiji earthquake input was used, and the ground motion acceleration time histories at sample valleys SC1 and SC4 were calculated based on our model.

[0023] The seismic wavefront bending effect of the valley site is obtained based on the verified amplification factor, which serves as the scattering law of the valley site. In this embodiment, the displacement amplification factor at any location in the valley site under excitation by cylindrical SH waves of different frequencies is obtained. u | / | u f Using the topographic amplification factor as the frequency domain transfer function and the bedrock ground motion time history as the incident signal, the ground motion time history at any location on the site, considering the valley amplification effect, can be obtained using the inverse fast Fourier transform technique.

[0024] To reveal the wavefront bending effect of cylindrical wave incidence, the time-domain incident signal was taken as a Ricker wavelet with characteristic frequencies... f c = 1.0 Hz. Calculated frequency. f = w The range of / 2π is within 4.0 Hz, with a step size of 1 / 24 Hz. The shape parameter of the symmetrical V-shaped valley is taken as... b = 1.0 km, d = 0.5 km, shear wave velocity assumed to be V s = 1 km / s. Figure 5 The corresponding hypocenter location (x0, y0) = (0 km, 10 km), half-width b = 1.0 km, and depth d = 0.5 km are in x 1 [-4 km, 4 km], y 1 The seismic response time histories of 81 × 41 points uniformly distributed within a rectangular space of [0 km, 4 km] are presented. The wavefields at six time points from 9.5 s to 13.0 s are given, demonstrating the propagation and scattering process of cylindrical waves near a symmetrical V-shaped valley. It can be seen that when direct waves and reflected waves from the horizontal surface encounter the V-shaped valley, the upper left and upper right corners of the valley and the valley floor continuously generate scattered waves as new wave sources, and the wavefront exhibits significant bending.

[0025] Furthermore, the step of simulating the first seismic motion of the valley site based on the topographic amplification effect also includes: First ground motion data of bedrock ground motion is obtained, and fast Fourier transform is performed on the first acceleration time history and the second displacement time history of the first ground motion data to obtain the Fourier spectrum. The theory of seismic wave propagation in valley sites is obtained, and the frequency domain topographic effect transfer function is calculated by combining the Fourier spectrum. The second seismic data of the valley site is obtained, and combined with the frequency domain topographic effect transfer function, a fast Fourier transform is performed to obtain the second displacement time history and the second acceleration time history, thus completing the first seismic simulation of the valley site.

[0026] In this embodiment, the amplification factor of valley topography on ground motion (relative to flat sites) is calculated using the proposed seismic propagation theory, yielding the ground motion at the valley site and providing input seismic waves that consider topographic effects for bridge seismic analysis. To obtain the spatially varying ground motion at the valley site given a flat site ground motion acceleration time history input, a time history synthesis method for valley site ground motions that considers topographic amplification effects is established. The key to this method lies in understanding and applying the topographic amplification factor caused by the valley, as explained below: The wave function series solution of a V-shaped valley uses a unit amplitude steady-state plane SH wave as the incident wave. If there were no valley (free field), the horizontal surface displacement amplitude at different locations would always be equal to 2. However, the valley topographic effect causes the surface displacement amplitude at different locations to fluctuate around 2. That is, at a certain frequency, if the displacement amplitude at a certain point on the surface is greater than 2, then the ground motion at that point is amplified relative to the free field; conversely, if it is less than 2, the ground motion is reduced. Based on this principle, dividing the valley surface displacement amplitude given by these wave function series solutions by 2 yields the seismic amplitude amplification factor of the valley topography. Similarly, dividing the valley surface displacement phase by the free field phase yields the seismic phase adjustment factor of the valley topography. The amplitude amplification factor and the phase adjustment factor are collectively referred to as the frequency domain topography amplification factor.

[0027] Based on bedrock ground motion and frequency domain topographic amplification factor, the ground motion acceleration, velocity and displacement time history of each point on the surface of the valley site are further obtained according to the procedure.

[0028] Furthermore, the second seismic motion simulation of the valley site based on the topographic effect of the spillway outlet slope also includes: Obtain the slope engineering characteristics of the outlet of the flood discharge tunnel, and obtain the slope instability and failure mode of the valley site based on the slope engineering characteristics; A slope calculation model of the spillway outlet is constructed, and the sample collection points of the slope and the ground motion time history and PGA magnification of the sample collection points are obtained. The first calculation results for horizontal and oblique incidence of seismic waves are calculated sequentially to determine the peak ground acceleration amplification factor and the third acceleration time history of each sample collection point.

[0029] In this embodiment, the mouth slope area is located in the downstream section of the river, which is a longitudinal valley. Most of the bedrock on the surface is exposed, and the exposed rock strata include: P1j 2 P1j 3 P1j 4 P1j 5 P1j 6 T3hn, the rock strata generally dip steeply upstream, with normal rock strata dip at N15°~35°W and SW∠50°~75°. Due to the river section being located in a longitudinal valley with deep incision, both banks exhibit varying degrees of toppling deformation. After the rock strata toppled, the surface rock strata on both banks dip towards the mountains, resulting in a "pseudo-anticline" phenomenon in the upstream and downstream sections of the river. The rocks in the outlet slope area are weakly weathered and weakly unloaded, with some areas experiencing strong toppling. They are mostly fragmented to interbedded structures. The slope instability failure mode is mainly small-scale block sliding collapse formed by structural plane combinations. The slope rock mass is classified as Class IV, with some areas classified as Class V, indicating poor stability conditions.

[0030] Based on the outlet slope profile, establish as follows Figure 6 The V-shaped valley calculation model is shown. The V-shaped valley has a width of 1275.79m and a depth of 497.58m. The model is excited by five seismic waves, including the Wenchuan-Maoxian wave and three artificial seismic waves (wave_acc_111 modified, wave_acc_222 modified, and wave_acc_333 modified). The seismic waves are incident horizontally, obliquely, and vertically, with the spillway outlet slope located on the wave-facing side. Twenty-one points are evenly selected from the top to the bottom of the slope as calculation points, numbered sequentially from #1 to #21. The seismic motion time histories and PGA amplification factors at these 21 calculation points are calculated as required.

[0031] When five seismic waves are incident horizontally and the exit slope is located on the wave-facing side, obtain the peak ground acceleration amplification factor of each calculation point and the acceleration time history at each calculation point on the exit slope when all four seismic waves are incident horizontally.

[0032] When four seismic waves are vertically incident, obtain the peak ground acceleration amplification factor at each calculation point; Under vertically incident seismic waves, the acceleration time history of each monitoring point on the exit slope was obtained; Furthermore, the third ground motion simulation of the valley site based on the topographic effect of the landslide deposit also includes: Obtain the engineering characteristics of the landslide deposit, and based on the engineering characteristics of the landslide, obtain the landslide geomorphological characteristics of the valley site; In this embodiment, it further includes: The Zhenggang landslide deposits are distributed on the eastern slope of the Zhenggang ridge, located on the right bank of the Lancang River between Yagong Gully and Gully No. 7. The landslide deposits range in elevation from 2180m to 3220m, with a width of nearly 1300m. Above elevation 2300m, surface vegetation is relatively well-developed. The slope exhibits well-developed gullies, including Zhenggang Gully, Yagong Gully, Gully No. 8, Gully No. 9, Gully No. 10, Gully No. 11, and a series of smaller gullies. Zhenggang Gully and Yagong Gully have deeper incisions, while the remaining smaller gullies are shallower and mostly distributed below elevation 2500m.

[0033] Landslide deposits above 2750m elevation have intact topography with steep slopes, generally 30°–35°; between 2250m and 2750m elevations, the topography is relatively intact and mostly consists of dry land cultivated by local villagers, with gentler slopes, generally 20°–30°; below 2250m elevation, the topography is poorly intact due to gully cutting, with steep banks, generally around 40°, and bedrock exposure is visible below 2200m elevation. The surface of the landslide deposits generally has 3m–5m of colluvial deposits (Q...). dl The plant roots are relatively well-developed, and below them is a layer of glacial water deposits (Q). dl ) and landslide deposits (Q del Below this is bedrock that has been severely overturned. The surface of the Zhenggang landslide deposit contains several small terraces, but due to later alterations, most of these terraces are no longer clearly visible. There are four levels of platforms on the landslide deposit, at elevations of 2850m, 2750m, 2480m, and 2350m. The slopes of these platforms are generally 10°–20°. Except for the 2850m platform, which has a relatively large exposed area, the others are generally smaller.

[0034] The landslide exhibits distinct landform features, with a tongue-shaped plan view and a chair-shaped rear edge. A fault platform of approximately 1m to 3m is visible at the rear edge, and tensile cracks of 2m to 4m in width have penetrated the entire rear edge slope of the landslide. The front edge of the landslide is generally a slightly convex arc shape, with an exposed height of 2200m to 2210m.

[0035] A computational model of the landslide deposit was constructed to obtain the sample collection points and the ground motion time history and PGA magnification of the sample collection points. In this embodiment, a V-shaped valley calculation model is established based on the cross-sectional diagram of the Zhenggang landslide deposit. The V-shaped valley has a width of 3816m and a depth of 1016m. The model is excited by six seismic waves, including three artificial seismic waves (wave_acc_111 modified, wave_acc_222 modified, and wave_acc_333 modified), the Wenchuan Maoxian wave, and two Jiuzhaigou waves (THN1 and THN2). The seismic waves are incident horizontally, obliquely, and vertically, with the slope of the Zhenggang landslide deposit located on the wave-facing side. Twenty-one points are evenly selected from the top to the bottom of the slope as calculation points, numbered sequentially from #1 to #21. The seismic motion time history and PGA amplification factor at these 21 calculation points are calculated as required. The second calculation results for horizontal and oblique incidence of seismic waves are calculated sequentially to determine the peak ground acceleration amplification factor and the fourth acceleration time history of each sample collection point.

[0036] In this embodiment, it further includes: The Zhenggang landslide deposits are distributed on the eastern slope of the Zhenggang ridge, located on the right bank of the Lancang River between Yagong Gully and Gully No. 7. The landslide deposits range in elevation from 2180m to 3220m, with a width of nearly 1300m. Above elevation 2300m, surface vegetation is relatively well-developed. The slope exhibits well-developed gullies, including Zhenggang Gully, Yagong Gully, Gully No. 8, Gully No. 9, Gully No. 10, Gully No. 11, and a series of smaller gullies. Zhenggang Gully and Yagong Gully have deeper incisions, while the remaining smaller gullies are shallower and mostly distributed below elevation 2500m.

[0037] Landslide deposits above 2750m elevation have intact topography with steep slopes, generally 30°–35°; between 2250m and 2750m elevations, the topography is relatively intact and mostly consists of dry land cultivated by local villagers, with gentler slopes, generally 20°–30°; below 2250m elevation, the topography is poorly intact due to gully cutting, with steep banks, generally around 40°, and bedrock exposure is visible below 2200m elevation. The surface of the landslide deposits generally has 3m–5m of colluvial deposits (Q...). dl The plant roots are relatively well-developed, and below them is a layer of glacial water deposits (Q). dl ) and landslide deposits (Q del Below this is bedrock that has been severely overturned. The surface of the Zhenggang landslide deposit contains several small terraces, but due to later alterations, most of these terraces are no longer clearly visible. There are four levels of platforms on the landslide deposit, at elevations of 2850m, 2750m, 2480m, and 2350m. The slopes of these platforms are generally 10°–20°. Except for the 2850m platform, which has a relatively large exposed area, the others are generally smaller.

[0038] The landslide exhibits distinct landform features, with a tongue-shaped plan view and a chair-shaped rear edge. A fault platform of approximately 1m to 3m is visible at the rear edge, and tensile cracks of 2m to 4m in width have penetrated the entire rear edge slope of the landslide. The front edge of the landslide is generally a slightly convex arc shape, with an exposed height of 2200m to 2210m.

[0039] When 7 seismic waves are incident horizontally and the slope of the Zhenggang landslide deposit is located on the wave-facing side, obtain the peak ground acceleration amplification factor of each calculation point; When the seven seismic waves are obliquely incident and the slope of the Zhenggang landslide deposit is located on the wave-facing side, the peak ground acceleration amplification factor of each calculation point is obtained. When seven seismic waves are incident vertically, the peak ground acceleration amplification factor at each calculation point is... Furthermore, the step of constructing the seismic input for the seismic field simulation based on the simulation results of the first, second, and third seismic motion simulations also includes: When the seismic waves are incident horizontally or obliquely, and the exit slope is located on the wave-facing side, determine the difference in peak ground acceleration at each sample collection point compared to a flat site, and determine the seismic motion input to be used in the project: The seismic input used to determine the location of each sample collection point on the exit slope was the wavefront result under horizontal incidence. When seismic waves are incident horizontally and obliquely, determine the difference in peak ground acceleration at the calculation point location on the wave-facing side of the landslide debris slope compared to a flat site, and determine the seismic input to be used in the project: The seismic input at all sample collection points on the slope of the Zhenggang landslide deposit was based on the wave-facing side results under horizontal incidence.

[0040] In this embodiment, when the seismic waves are incident horizontally and obliquely, and the exit slope is located on the wavefront side, the peak ground acceleration (PGA) at each calculation point is significantly amplified compared to a flat site. The amplification effect is strongest when the seismic waves are incident horizontally, with a maximum amplification factor of 2.42 times. When the seismic waves are incident vertically, the amplification of PGA at each calculation point is not significant. It is recommended that the most unfavorable seismic motion input be used for this project: the seismic motion input at each calculation point on the exit slope should use the wavefront side results under horizontal incidence.

[0041] When seismic waves are incident horizontally or obliquely, the peak ground acceleration (PGA) at the calculation points on the wavefront side of the Zhenggang landslide slope is significantly amplified compared to flat sites. The amplification effect is strongest with horizontal incidence, reaching up to 2.38 times. When seismic waves are incident vertically, the PGA amplification at the calculation points on the Zhenggang landslide slope is not significant. It is recommended that the most unfavorable seismic input be used for this project: the seismic input at all calculation points on the Zhenggang landslide slope should use the wavefront results under horizontal incidence.

[0042] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces, or indirect coupling or communication connection between apparatuses or units, and may be electrical, mechanical, or other forms.

[0043] Furthermore, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated units described above can be implemented in hardware or as software functional units. The above are merely embodiments of this application and do not limit the patent scope of this application. Any equivalent structural or procedural transformations made based on the description and drawings of this application, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

[0044] The specific embodiments of the invention have been described in detail above, but they are only examples, and this application is not limited to the specific embodiments described above. For those skilled in the art, any equivalent modifications or substitutions to the invention are also within the scope of this application. Therefore, all equivalent changes, modifications, and improvements made without departing from the spirit and principles of this application should be covered within the scope of this application.

Claims

1. A method for simulating seismic ground motion based on the topographic effect of a river valley site, characterized in that, include: Based on the properties of the symmetrical V-shaped valley site, a planar model of the symmetrical V-shaped valley site is constructed to obtain the seismic wave propagation model and scattering law of the symmetrical V-shaped valley site. Based on the topographic amplification effect, a first ground motion simulation was performed on the valley site; a second ground motion simulation was performed on the valley site based on the topographic effect of the spillway outlet slope; and a third ground motion simulation was performed on the valley site based on the topographic effect of the Zhenggang landslide deposit. Based on the simulation results of the first, second, and third ground motion simulations, the ground motion input for the ground motion field simulation is constructed.

2. The seismic field simulation method based on valley site topographic effects according to claim 1, characterized in that, Based on the attribute characteristics of the symmetrical V-shaped valley site, a planar model of the symmetrical V-shaped valley site is constructed to obtain the seismic wave propagation model and scattering law of the symmetrical V-shaped valley site, which also includes: Based on the property characteristics of the symmetrical V-shaped valley site, and combined with the cylindrical SH wave, a planar model of the symmetrical V-shaped valley site is constructed. Obtain the wave field structure of the planar model, and solve the wavelength structure to obtain the theoretical solution of the boundary value problem; The theoretical solution is degenerate-verified based on the asymptotic equivalence between far-field cylindrical waves and plane waves, and the amplification factor is obtained. The amplification effect of the measured earthquakes in the sample river valley is used to verify the amplification factor; The seismic wavefront bending effect of the valley site is obtained based on the verified amplification factor, which serves as the scattering law of the valley site.

3. The seismic field simulation method based on valley site topography effect according to claim 1, characterized in that, The method of simulating the first seismic motion of the valley site based on the topographic amplification effect also includes: First ground motion data of bedrock ground motion is obtained, and fast Fourier transform is performed on the first acceleration time history and the second displacement time history of the first ground motion data to obtain the Fourier spectrum. The theory of seismic wave propagation in valley sites is obtained, and the frequency domain topographic effect transfer function is calculated by combining the Fourier spectrum. The second seismic data of the valley site is obtained, and combined with the frequency domain topographic effect transfer function, a fast Fourier transform is performed to obtain the second displacement time history and the second acceleration time history, thus completing the first seismic simulation of the valley site.

4. The seismic field simulation method based on valley site topography effect according to claim 1, characterized in that, The second ground motion simulation of the valley site based on the topographic effect of the spillway outlet slope also includes: Obtain the slope engineering characteristics of the outlet of the flood discharge tunnel, and obtain the slope instability and failure mode of the valley site based on the slope engineering characteristics; A slope calculation model of the spillway outlet is constructed, and the sample collection points of the slope and the ground motion time history and PGA magnification of the sample collection points are obtained. The first calculation results for horizontal and oblique incidence of seismic waves are calculated sequentially to determine the peak ground acceleration amplification factor and the third acceleration time history of each sample collection point.

5. The seismic field simulation method based on valley site topography effect according to claim 4, characterized in that, The third ground motion simulation of the valley site based on the topographic effect of the landslide deposit also includes: Obtain the engineering characteristics of the landslide deposit, and based on the engineering characteristics of the landslide, obtain the landslide geomorphological characteristics of the valley site; A computational model of the landslide deposit was constructed to obtain the sample collection points and the ground motion time history and PGA magnification of the sample collection points. The second calculation results for horizontal and oblique incidence of seismic waves are calculated sequentially to determine the peak ground acceleration amplification factor and the fourth acceleration time history of each sample collection point.

6. The seismic field simulation method based on valley site topography effect according to claim 4, characterized in that, The method of constructing the seismic input for seismic field simulation based on the simulation results of the first, second, and third seismic ground motion simulations further includes: When the seismic waves are incident horizontally or obliquely, and the exit slope is located on the wave-facing side, determine the difference in peak ground acceleration at each sample collection point compared to a flat site, and determine the seismic motion input to be used in the project: The seismic input used to determine the location of each sample collection point on the exit slope was the wavefront result under horizontal incidence. When seismic waves are incident horizontally and obliquely, determine the difference in peak ground acceleration at the calculation point location on the wave-facing side of the landslide debris slope compared to a flat site, and determine the seismic input to be used in the project: The seismic input at all sample collection points on the slope of the Zhenggang landslide deposit was based on the wave-facing side results under horizontal incidence.

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