Method for determining ground motion in geotechnical engineering disaster assessment near thrust active faults

Abstract

The present invention discloses a method for determining seismic motion for evaluating geotechnical engineering disasters near a thrust active fault, comprising the following steps: S1: investigating a target work site to determine the site category and seismic motion level of the target work site; S2: determining seismic motion parameters; S3: considering the influence of the multi-directionality of seismic motion near a thrust active fault, the hanging wall effect, and the mutual relationship between the slope strike and the fault orientation on the determination of seismic motion, determining the seismic force at the target work site; S4: determining the seismic pulse velocity peak and pulse period at the target work site; S5: selecting measured seismic records and adjusting the proportional coefficient of the measured seismic records; S6: determining the seismic motion at the target work site using a time history analysis method. The present invention considers the influence of the multi-directionality of seismic motion near a thrust active fault, the hanging wall effect, and the mutual relationship between the slope strike and the fault orientation on the determination of seismic motion, can more accurately determine seismic motion, and provides technical support for slope seismic stability evaluation.

Description

Technical Field

[0001] The present invention relates to the technical field of slope seismic stability evaluation, and in particular to a method for determining earthquake motion for disaster evaluation of geotechnical engineering near-thrust active fault. Background Art

[0002] my country lies between the Eurasian seismic belt and the Pacific Rim seismic belt, prone to frequent earthquakes and numerous secondary hazards. Landslides are the most significant of these disasters, causing significant loss of life and property, as well as ecological degradation, due to their large number and widespread distribution. However, with the gradual westward expansion of transportation, numerous engineering structures are located near active faults, or even directly cross multiple faults. This presents a challenging challenge for engineers in determining the seismic motions required for geotechnical engineering disaster assessments near active faults.

[0003] Compared with far-field earthquakes, earthquake motions near active faults often have characteristics such as long-period velocity pulses, directional effects, hanging wall effects, surface ruptures, and permanent displacements. Currently, when evaluating slope stability, methods for determining earthquake motions include pseudo-static, pseudo-dynamic, and time-history analysis. Among them, the traditional pseudo-static method simplifies irregular earthquake loads into static loads that act directly on the center of gravity of the slope sliding block. This method cannot reflect the dynamic characteristics of earthquakes and the dynamic response of slopes. The traditional pseudo-dynamic method uses a sinusoidal wave curve to simulate earthquake waves. This method takes into account the dynamic characteristics of earthquakes, but because it does not consider the dynamic characteristics and damping characteristics of the slope material, it cannot reflect the dynamic characteristics of the slope under earthquake loads. The time-history analysis method can truly describe the earthquake acceleration in all directions during an earthquake. This method is often combined with computer numerical simulation to perform earthquake time-history analysis. At the same time, traditional methods for determining seismic motions do not take into account the particularity of seismic motions near active faults, and different seismic motion determination methods have not yet been adopted for different fault types. How to select input seismic motions suitable for geotechnical engineering disaster assessment near thrust active faults for time-history response analysis has not yet been clearly explained in the corresponding specifications.

[0004] At the same time, numerous earthquake damage surveys have shown that earthquake-induced landslides exhibit a significant directional effect, with slopes perpendicular to the fault direction being more susceptible to damage under earthquake action. However, traditional methods for determining ground motions do not adequately consider the relationship between slope inclination and the orientation of the seismogenic fault. Therefore, a method for determining ground motions suitable for geotechnical engineering disaster assessment near active thrust faults is needed. Summary of the Invention

[0005] In view of the above problems, the present invention aims to provide a method for determining seismic motion for disaster assessment of geotechnical engineering near-thrust active faults.

[0006] The technical solutions of the present invention are as follows:

[0007] A method for determining earthquake motion for disaster assessment of geotechnical engineering near-thrust active faults comprises the following steps:

[0008] S1: Investigate the target work site to determine the site type of the target work site and the seismic level of the target work site;

[0009] S2: determining the seismic parameters of the target construction site according to the site type and the seismic level;

[0010] S3: determining the seismic force at the target working point based on the seismic motion parameters and taking into account the multidirectionality of the seismic motion near the thrust active fault, the hanging wall effect, and the influence of the relationship between the slope strike and the fault orientation on the determination of the seismic motion;

[0011] S4: determining the seismic pulse velocity peak value and pulse period at the target work point according to the seismic parameters of the target work point;

[0012] S5: selecting a measured seismic record and adjusting a proportional coefficient of the measured seismic record according to the peak value and pulse period of the seismic pulse velocity at the target working point;

[0013] S6: Determine the seismic motion of the target construction site using a time history analysis method based on the seismic force and the adjusted measured seismic record.

[0014] Preferably, in step S1, when investigating the target work site, the investigation content includes the fault type and strike at the target work site, site conditions, earthquake intensity, historical maximum magnitude, and the distance between the target work site and the fault.

[0015] Preferably, in step S1, when determining the site category of the target work point, the site category of the target work point is determined according to the shear wave velocity and the thickness of the site cover layer and in accordance with the China Seismic Parameter Zoning Map, wherein the shear wave velocity is the equivalent shear wave velocity of the soil layer or the shear wave velocity of the rock.

[0016] Preferably, in step S2, the seismic parameters include seismic peak acceleration and characteristic period.

[0017] Preferably, in step S2, when determining the earthquake parameters of the target construction site:

[0018] If the site category of the target work site is a Class II site and the target work site is applicable to the China Earthquake Motion Parameter Zoning Map, determining the earthquake motion parameters of the target work site according to the China Earthquake Motion Parameter Zoning Map;

[0019] If the site category of the target construction site is Class II and the target construction site is not applicable to the China Earthquake Motion Parameter Zoning Map, the earthquake motion parameters of the target construction site are determined according to the earthquake safety evaluation report;

[0020] If the site category of the target work point is a non-Class II site, the Class II site seismic parameters are adjusted to the seismic parameters of the target work point using the site seismic adjustment coefficient.

[0021] Preferably, in step S3, the seismic force at the target working point is determined by the following formula:

[0022] Q eh =η1η2α h G (1)

[0023] Q ehi =η1η2α h G i (2)

[0024] Q ev =η1η2α v G (3)

[0025] Q evi =η1η2α v G i (4)

[0026] Where: Q eh , Q ehi are the horizontal seismic forces per unit width of the sliding body, the i-th calculation strip or unit, kN / m; Q ev , Q evi are the vertical seismic force per unit width of the sliding body, the i-th calculation strip or unit, respectively, in kN / m; η1 is the orientation coefficient between the slope and the potential seismogenic fault; η2 is the hanging wall correction coefficient between the slope and the potential seismogenic fault; α h , α v is the comprehensive horizontal and vertical seismic coefficient of the slope; G, G i are the self-weight of the sliding body, the i-th calculation bar or unit width, kN / m respectively.

[0027] Preferably, when the inclination of the potential sliding surface of the slope is perpendicular to the fault strike at ±45°, the orientation coefficient η1 of the slope and the potential seismic fault is taken as 1.2, and the rest is taken as 1.0; when the potential sliding surface of the slope is located on the hanging wall of the fault, the correction coefficient η2 of the slope and the hanging wall of the potential seismic fault is taken as 1.4, and the rest is taken as 1.0.

[0028] Preferably, in step S5, when selecting measured earthquake records, no less than 11 historical strong earthquake records are selected, and the historical strong earthquake records of the target work site are used preferentially.

[0029] Preferably, when the number of measured earthquake records is insufficient, artificially simulated earthquake motions are used to obtain measured earthquake records; when artificially simulated earthquake motions are used:

[0030] If the influence of horizontal and vertical earthquake motion is considered, the earthquake coefficient k in the main horizontal direction is h1 : Vertical seismic coefficient k v =The ratio of 1:0.65 determines the seismic coefficient;

[0031] If the influence of three-dimensional earthquake motion is considered, the main horizontal direction earthquake coefficient k h1 : Secondary horizontal seismic coefficient k h2 : Vertical seismic coefficient k v =The seismic coefficient is determined by the ratio of 1:0.85:0.65.

[0032] Preferably, when artificially simulating earthquake motion, for slopes within 10 km on both sides of the earthquake-generating fault, the peak ground acceleration is multiplied by the amplification coefficient, so that the earthquake influence coefficient curve takes into account the influence of the near-fault effect and the earthquake motion parameters are taken into account the near-field effect.

[0033] The beneficial effects of the present invention are:

[0034] The present invention combines the pseudo-static method with the time-history analysis method. By considering the multi-directionality of the seismic motion near the thrust active fault, the hanging wall effect, and the influence of the relationship between the slope strike and the fault orientation on the determination of the seismic motion, the seismic motion of the near-thrust active fault can be determined more accurately, providing technical support for the geotechnical engineering disaster evaluation of the near-thrust active fault. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 The figure is a flow chart of the method for determining earthquake motion for disaster assessment of geotechnical engineering near-thrust active fault according to the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described below with reference to the accompanying drawings and examples. It should be noted that, in the absence of conflict, the embodiments in this application and the technical features in the embodiments can be combined with each other. It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meanings as those commonly understood by those of ordinary skill in the art to which this application belongs. The use of similar words such as "include" or "comprising" in the present invention means that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0038] like Figure 1 As shown, the present invention provides a method for determining earthquake motion for disaster assessment of geotechnical engineering near-thrust active fault, comprising the following steps:

[0039] S1: Investigate the target work site to determine the site type of the target work site and the seismic level of the target work site.

[0040] In one specific embodiment, the investigation of the target work site includes the type and strike of the fault at the target work site, site conditions, earthquake intensity, historical maximum magnitude, and the distance between the target work site and the fault. The site category of the target work site is determined based on the shear wave velocity and the thickness of the overburden, using the China Seismic Parameter Zoning Map. The shear wave velocity is the equivalent shear wave velocity of the soil layer or the rock shear wave velocity.

[0041] S2: Determine the seismic parameters of the target construction site according to the site type and the seismic level.

[0042] In a specific embodiment, the seismic parameters include seismic peak acceleration and characteristic period. When determining the seismic parameters of the target work point:

[0043] If the site category of the target work site is a Class II site and the target work site is applicable to the China Earthquake Motion Parameter Zoning Map, determining the earthquake motion parameters of the target work site according to the China Earthquake Motion Parameter Zoning Map;

[0044] If the site category of the target construction site is Class II and the target construction site is not applicable to the China Earthquake Motion Parameter Zoning Map, the earthquake motion parameters of the target construction site are determined according to the earthquake safety evaluation report;

[0045] If the site category of the target work point is a non-Class II site, the Class II site seismic parameters are adjusted to the seismic parameters of the target work point using the site seismic adjustment coefficient.

[0046] In the above embodiment, the China Earthquake Motion Parameter Zoning Map optionally uses the latest version of the "China Earthquake Motion Parameter Zoning Map." The specific method for adjusting the Class II site seismic parameters to the seismic parameters of the target worksite using the site seismic adjustment coefficient is prior art and will not be further described here. Furthermore, if the latest version of the "China Earthquake Motion Parameter Zoning Map" does not meet the seismic level at the target worksite, the corresponding seismic parameters can be obtained by consulting Tables 1 and 2.

[0047] Table 1 Earthquake type classification

[0048]

[0049] Table 1 Peak seismic acceleration corresponding to Class II site / g

[0050]

[0051]

[0052] It should be noted that Tables 1 and 2 provide the peak acceleration and characteristic period for Class II sites based on different seismic types with a 50-year reference period. If the reference period is not 50 years, further conversion is required based on the 50-year period. The specific conversion method is based on existing techniques and will not be detailed here.

[0053] S3: Determine the seismic force of the target working point based on the seismic motion parameters and taking into account the multidirectionality of the seismic motion near the thrust active fault, the hanging wall effect, and the influence of the relationship between the slope strike and the fault orientation on the determination of the seismic motion.

[0054] In a specific embodiment, when verifying the seismic stability of a slope, the rigid body limit equilibrium method and the static numerical calculation method are used to calculate the stability of a slope without important buildings (structures) in the landslide area. The seismic action of the sliding body, strip, or unit is simplified to a static force acting outside the center of gravity of the sliding body, strip, or unit and pointing outward from the slope (in the direction of sliding). The seismic force at the target working point is determined by the following formula:

[0055] Q eh =η1η2α h G (1)

[0056] Q ehi =η1η2α h G i (2)

[0057] Q ev =η1η2α v G (3)

[0058] Q evi =η1η2α v G i (4)

[0059] Where: Q eh , Q ehi are the horizontal seismic forces per unit width of the sliding body, the i-th calculation strip or unit, kN / m; Q ev , Q evi are the vertical seismic force per unit width of the sliding body, the i-th calculation strip or unit, respectively, in kN / m; η1 is the orientation coefficient between the slope and the potential seismogenic fault; η2 is the hanging wall correction coefficient between the slope and the potential seismogenic fault; α h , αv is the comprehensive horizontal and vertical seismic coefficient of the slope; G, G i are the self-weight of the sliding body, the i-th calculation bar or unit width, kN / m respectively.

[0060] Optionally, when the inclination of the potential sliding surface of the slope is perpendicular to the fault strike at ±45°, the orientation coefficient η1 of the slope and the potential seismic fault is taken as 1.2, and the rest is taken as 1.0; when the potential sliding surface of the slope is located on the hanging wall of the fault, the correction coefficient η2 of the slope and the hanging wall of the potential seismic fault is taken as 1.4, and the rest is taken as 1.0.

[0061] Optionally, the slope comprehensive horizontal and vertical seismic coefficient α h , α v The peak acceleration zoning of the earthquake motion in the area where the target construction site is located is determined according to Table 3:

[0062] Table 3 Comprehensive seismic coefficient of slope

[0063]

[0064] S4: Determine the seismic pulse velocity peak value and pulse period at the target work point according to the seismic parameters of the target work point.

[0065] It should be noted that the speed can be obtained according to the acceleration through integration, and the specific algorithm will not be described here.

[0066] S5: Selecting a measured seismic record and adjusting a proportional coefficient of the measured seismic record according to the seismic pulse velocity peak value and pulse period at the target working point.

[0067] In the prior art, acceleration is typically used to select measured seismic records. However, when applied to near-thrust active faults, this method can result in very small acceleration but significant damage. Consequently, the measured seismic records selected in this manner are inaccurate and cannot accurately determine the seismic motion for geotechnical engineering disaster assessment near-thrust active faults. The present invention uses the peak acceleration and characteristic period of the seismic motion at the worksite to determine the peak pulse velocity and pulse period of the seismic motion at the worksite. These peak pulse velocity and pulse period are then used to select measured seismic records, thereby overcoming the drawback of the prior art that using acceleration for selection is not suitable for near-thrust active faults.

[0068] In a specific embodiment, when selecting measured earthquake records, no less than 11 historical strong earthquake records are selected, and the historical strong earthquake records of the target work site are used preferentially.

[0069] Optionally, when strong earthquake records cannot be obtained at the target work site, strong earthquake records from a site with geological conditions similar to those of the target work site can be selected as input. The parameters such as magnitude, peak ground acceleration (PGA), focal depth, seismic fault type and distance of the measured earthquake records of the selected similar site are similar to those of the historical earthquakes at the target work site.

[0070] Optionally, when the number of measured earthquake records is insufficient, artificially simulated earthquake motions may be used to obtain measured earthquake records.

[0071] In a specific embodiment, when artificially simulated earthquake motion is used, the number of actual strong earthquake records should not be less than 2 / 3 of the total. A maximum of two strong earthquake records measured at different measuring points of the same earthquake should be selected. The strong earthquake records of the same earthquake event or the same station should not exceed 1 / 3 of the total number. When artificially simulated earthquake motion is used, if the horizontal seismic coefficient kh needs to be distinguished between the main (generally perpendicular to the fault direction), secondary and vertical directions, if the influence of horizontal and vertical earthquake motion is considered, the main horizontal direction seismic coefficient k h1 : Vertical seismic coefficient k v =1:0.65 ratio to determine the seismic coefficient; if the influence of three-dimensional earthquake motion is considered, the seismic coefficient k in the main horizontal direction is used. h1 : Secondary horizontal seismic coefficient k h2 : Vertical seismic coefficient k v =1:0.85:0.65 to determine the seismic coefficient. The horizontal seismic coefficient is determined based on the engineering fortification level and site type. This is conventional technology and will not be elaborated on here.

[0072] In one specific embodiment, for slopes within 10 km of a seismic fault, the seismic influence coefficient curve is factored into the near-fault effect by multiplying the peak ground acceleration by an amplification factor, thereby accounting for near-field effects on the seismic motion parameters. Optionally, the amplification factor increases the closer to the seismic fault. In one specific embodiment, the peak ground acceleration of slopes within 5 km of a seismic fault is multiplied by an amplification factor of 1.5, while the peak ground acceleration of slopes within 5-10 km of a seismic fault is multiplied by an amplification factor of 1.25.

[0073] In a specific embodiment, the scaling factor of the measured seismic record can be adjusted by scaling the peak acceleration, peak velocity, or peak displacement. For example, if the peak acceleration of a measured seismic record is 0.01 and the determined peak acceleration is 0.05, the acceleration curve of the measured seismic record is amplified by multiplying it by 5 times.

[0074] In a specific embodiment, considering the near-fault effect and selecting ground motion records that conform to the site characteristics, the near-fault ground motion records provided in Table 4 can be selected.

[0075] Table 4 Near-fault ground motion records

[0076]

[0077] In Table 4, the fault properties are classified according to the slip angle. Among them, normal faults represent: -120° < Rake < -60°; reverse faults represent: 60° < Rake < 120°; reverse oblique-slip faults represent: 30° < Rake < 60°, 120° < Rake < 150°. Among them, Rake represents the fault slip angle, -180° ≤ Rake ≤ 180°, measured relative to the reference strike of the fault plane, and the angle counterclockwise to the slip direction is positive, and clockwise is negative.

[0078] S6: According to the seismic force and the adjusted measured seismic record, use the time history analysis method to determine the ground motion of the target construction site.

[0079] Using the time history analysis method to determine the ground motion is a prior art, and the specific method will not be elaborated here.

[0080] In summary, when the present invention conducts ground motion determination for the geotechnical disaster evaluation of near-thrust active faults, it considers the multi-directionality and velocity pulse characteristics of ground motion, the dynamic response of high-steep slopes, the hanging wall effect, and the mutual relationship between the slope strike and the fault orientation, making the results of the present invention more accurate. Compared with the prior art, the present invention has significant progress.

[0081] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for determining earthquake motion for disaster assessment of geotechnical engineering near-thrust active fault, characterized in that: The following steps are involved: S1: Investigate the target work site to determine the site type of the target work site and the seismic level of the target work site; S2: determining the seismic parameters of the target construction site according to the site type and the seismic level; S3: determining the seismic force at the target working point based on the seismic motion parameters and taking into account the multidirectionality of the seismic motion near the thrust active fault, the hanging wall effect, and the influence of the relationship between the slope strike and the fault orientation on the determination of the seismic motion; S4: determining the seismic pulse velocity peak value and pulse period at the target work point according to the seismic parameters of the target work point; S5: selecting a measured seismic record and adjusting a proportional coefficient of the measured seismic record according to the peak value and pulse period of the seismic pulse velocity at the target working point; S6: Determine the seismic motion of the target construction site using a time history analysis method based on the seismic force and the adjusted measured seismic record.

2. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 1, characterized in that: In step S1, when investigating the target work site, the investigation content includes the fault type and strike at the target work site, site conditions, earthquake intensity, historical maximum magnitude, and the distance between the target work site and the fault.

3. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 1, characterized in that: In step S1, when determining the site category of the target work point, the site category of the target work point is determined according to the shear wave velocity and the thickness of the site cover layer, according to the China Earthquake Motion Parameter Zoning Map. The shear wave velocity is the equivalent shear wave velocity of the soil layer or the shear wave velocity of the rock.

4. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 1, characterized in that: In step S2, the seismic parameters include seismic peak acceleration and characteristic period.

5. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 4 is characterized in that: In step S2, when determining the earthquake parameters of the target construction site: If the site category of the target work site is a Class II site and the target work site is applicable to the China Earthquake Motion Parameter Zoning Map, determining the earthquake motion parameters of the target work site according to the China Earthquake Motion Parameter Zoning Map; If the site category of the target construction site is Class II and the target construction site is not applicable to the China Earthquake Motion Parameter Zoning Map, the earthquake motion parameters of the target construction site are determined according to the earthquake safety evaluation report; If the site category of the target work point is a non-Class II site, the Class II site seismic parameters are adjusted to the seismic parameters of the target work point using the site seismic adjustment coefficient.

6. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 1, characterized in that: In step S3, the seismic force at the target working point is determined by the following formula: Q eh =η1η2α h G (1) Q ehi =η1η2α h G i (2) Q ev =η1η2α v G (3) Q evi =η1η2α v G i (4) Where: Q eh , Q ehi are the horizontal seismic forces per unit width of the sliding body, the i-th calculation strip or unit, kN / m; Q ev , Q evi are the vertical seismic force per unit width of the sliding body, the i-th calculation strip or unit, kN / m; η1 is the azimuth coefficient between the slope and the potential seismogenic fault; η2 is the correction coefficient between the slope and the hanging wall of the potential seismogenic fault; α h , α v is the comprehensive horizontal and vertical seismic coefficient of the slope; G, G i are the self-weight of the sliding body, the i-th calculation bar or unit width, kN / m respectively.

7. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 6, characterized in that: When the inclination of the potential sliding surface of the slope is perpendicular to the fault strike at ±45°, the orientation coefficient η1 between the slope and the potential seismic fault is taken as 1.2, and the rest is taken as 1.0; when the potential sliding surface of the slope is located on the hanging wall of the fault, the correction coefficient η2 between the slope and the hanging wall of the potential seismic fault is taken as 1.4, and the rest is taken as 1.

0.

8. The method for determining seismic motion for geotechnical engineering disaster assessment near-thrust active fault according to any one of claims 1 to 7, characterized in that: In step S5, when selecting measured earthquake records, no less than 11 historical strong earthquake records are selected, and the historical strong earthquake records of the target work site are used preferentially.

9. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 8, characterized in that: When the number of measured earthquake records is insufficient, artificially simulated earthquake motions are used to obtain measured earthquake records. When artificially simulated earthquake motions are used: If the influence of horizontal and vertical earthquake motion is considered, the earthquake coefficient k in the main horizontal direction is h1 : Vertical seismic coefficient k v =The ratio of 1:0.65 determines the seismic coefficient; If the influence of three-dimensional earthquake motion is considered, the main horizontal direction earthquake coefficient k h1 : Secondary horizontal seismic coefficient k h2 : Vertical seismic coefficient k v =The seismic coefficient is determined by the ratio of 1:0.85:0.

65.

10. The method for determining earthquake motion for geotechnical engineering disaster assessment near-thrust active fault according to claim 9, characterized in that: When artificially simulating earthquake motion, for slopes within 10 km on both sides of the earthquake-generating fault, the peak ground acceleration is multiplied by the amplification coefficient, so that the earthquake influence coefficient curve takes into account the influence of the near-fault effect and the earthquake motion parameters are taken into account the near-field effect.

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