Method for identifying earthquake response rule of slope containing ductile shear zone in vibration table test

Abstract

The invention discloses a method for identifying a seismic response rule of a side slope containing a ductile shear zone in a vibration table test, and belongs to the technical field of side slope seismic response monitoring. Comprising the following steps: S1, carrying out a vibration table similar material test according to rock mass mechanical parameters and a Buckingham Pi similarity theorem, and constructing a slope physical model containing a ductile shear zone; s2, acceleration sensors are arranged from the slope surface to the interior of the slope in the horizontal direction and the vertical direction; s3, carrying out a vibration table experiment until the model is completely damaged, and recording original data; and S4, processing and analyzing the original data, and carrying out acceleration response analysis. According to the method and the device, the defect that the conventional earthquake damage mode for the tough shear band edge / landslide is not considered from the monitoring physical quantity in the tough shear band edge / landslide slope body and the characteristic parameters of the landslide body is overcome.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of slope seismic response monitoring, and particularly relates to a method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test. BACKGROUND

[0002] Water and electricity resources are increasingly in demand. Some areas become the focus of water and electricity development due to their rich water resources, large altitude difference, and steep terrain. Many large-scale water and electricity projects have been built or planned in the region. However, under the action of strong tectonic activity, structural surfaces such as ductile shear zones develop in the region, and the region is frequently seismically active. A large number of seismic activities induce slope instability, deformation, and damage, which has a huge impact on local production and people's lives. Therefore, it is very important to study the stability of high and steep slopes containing ductile shear zones under seismic action.

[0003] Early research mainly analyzed monitoring data to understand and study the dynamic response characteristics of slopes under seismic action. Davis (1971, 1973) observed that the seismic acceleration at the top of Kagel Mountain increased significantly relative to the foot of the mountain, and the increase in acceleration, velocity, and displacement was different.

[0004] In terms of theoretical summary, Louis Geli (1988) first summarized the theoretical and observational research results of topographic amplification and drew a comprehensive conclusion. Ashford and Sitar (1997) defined three important parameters based on free-field, slope-top free-field, and peak acceleration data at the slope top: topographic amplification, site amplification, and surface amplification. These parameters have important guiding significance for subsequent seismic research. Academician Wang Sijing (1977) explored the dynamic friction characteristics of single slip surfaces through seismic simulation tests and conducted a detailed dynamic analysis of the stability of rock slopes. Hu Yuxian et al. (1980) analyzed the site response of the 1970 Tonghai earthquake in Yunnan and the 1976 Tangshan earthquake in Hebei. The results showed that compared to bedrock, the soil in these areas showed higher acceleration extremes and longer vibration durations. Wang Cunyu (1987) observed that the acceleration of rock slopes under seismic action not only had significant amplification in the vertical direction, but also showed an enhancement effect in the horizontal direction during the dynamic model test of the double-curvature arch dam of the Ertan Hydropower Station.

[0005] In recent years, shaking table test has become a key technology for analyzing the deformation and failure mechanism of slopes. Liang Qingguo and Tsesarsky (2005) used this technology to deeply explore the failure behavior of layered rock slope under the action of earthquake, highlighting the key influence of rock mass structure on the stability of slope under dynamic conditions; Professor Huang Runqiu and his team studied the seismic dynamic response of anti-inclined and bedding structure rock mass slope under strong earthquake conditions through large-scale shaking table model test; Xu Qiang et al. (2011) designed a large-scale shaking table test with a scale of 1:100 on a typical slope in the "5.12" Wenchuan earthquake disaster area, and completed a large-scale shaking table test on a conceptual model of upper soft and lower hard and upper hard and lower soft horizontal layered rock mass; Li Zhensheng (2012) combined with the secondary geological disasters caused by the "5.12" Wenchuan earthquake, discussed the similarity relationship of shaking table test and the related problems of model design scheme through a 1:100 scale slope shaking table test; Dong Jinyu et al. (2012) used orthogonal experiment to study the influence of iron powder, barite powder, gypsum and binder concentration on various physical quantity parameters through uniaxial compression, splitting test and direct shear test, and used quartz sand, barite powder and iron powder as similar material skeleton, and used gypsum and rosin alcohol as adhesive to build the model.

[0006] Many scholars in various countries have carried out shaking table tests with different influencing factors such as wave shape, amplitude, frequency, loading direction, different models such as soft and hard interbedded slope model, bedding slope model, interlayer containing slope model, and a lot of matching research on shaking table test similar materials, and have obtained certain conclusions and results. In addition, scholars at home and abroad also use finite element analysis method, finite difference method and discrete element analysis method to model and simulate different types of slopes, and have obtained many summary conclusions, and long-term research has verified the reliability of numerical simulation. The present application will verify the laws obtained by physical simulation through Flac3D numerical software after physical test, and calculate and analyze the actual engineering slope. SUMMARY

[0007] Specifically, the present application provides a method for identifying the seismic response law of a slope containing a ductile shear band in a shaking table test, comprising the following steps: S1. According to the rock mass mechanical parameters and the Buckingham π similarity theorem, a shaking table similar material test is carried out to construct a slope physical model containing a ductile shear band; S2. Acceleration sensors are arranged along the horizontal and vertical directions from the slope surface to the slope interior; S3. The shaking table test is carried out until the model is completely destroyed, and the original data are recorded; S4. The original data are processed and analyzed, and acceleration response analysis is carried out.

[0008] Preferably, in the S1, the rock mass mechanical parameters include: conducting a conventional triaxial compression test on the micro-new dacite, weakly unloading dacite, strongly unloading dacite and ductile shear zone rock samples in the research area by field sampling, and combining the existing actual situation to propose the mechanical parameter recommended values of various rock masses in the research area.

[0009] Preferably, according to the Buckingham similarity theorem, materials are selected, and a cast-in-place method is adopted to pour from bottom to top in stages, tamp every 10 cm of pouring, and then pour the next layer. Before pouring the next layer, the tamped part of the first layer is scraped and quartz sand is laid on the bottom layer of the model box.

[0010] Preferably, in the S2, the acceleration sensor arrangement includes arranging a plurality of slope surface monitoring points along the ductile shear zone line, and then drawing a slope surface monitoring line along the intersection surface of the ductile shear zone and the dacite.

[0011] Preferably, the S3 includes loading a plurality of groups of artificial fitting ground motions, and after the artificial fitting ground motion loading is completed, inputting waves in the order of low frequency and low amplitude to high frequency and high amplitude until the slope physical model is completely destroyed and the original data is recorded.

[0012] Preferably, the input wave adopts two types of fitting ground motion data and sine wave in the research area, and loads sine waves with different frequencies and different amplitudes in the excitation direction.

[0013] Preferably, the excitation direction includes X direction and Z direction; the different frequencies include 5 Hz, 15 Hz and 25 Hz; and the different amplitudes include 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g and 0.8g.

[0014] Preferably, the original data is processed by 50 Hz low-pass filtering, and the filtered data is corrected by baseline correction of initial acceleration incompatibility by using spectr software.

[0015] Preferably, the baseline correction includes the following steps: Define the acceleration, velocity and displacement time histories before correction, the acceleration, velocity and displacement time histories after correction, and then obtain the corresponding trend polynomials; Integrate the acceleration signal before correction once to obtain the velocity time history, fit the velocity time history by using a polynomial with a constant term of 0 to obtain the correction trend polynomial of the velocity time history; According to the derivative relationship between velocity and acceleration, derive the correction trend polynomial of the velocity time history to obtain the acceleration trend polynomial considering the baseline offset trend of the velocity time history; Substitute the acceleration trend polynomial considering the baseline offset trend of the velocity time history into the acceleration before correction to complete the baseline correction of the acceleration signal considering the curve offset of the velocity time history. The displacement time history is obtained by twice integrating the acceleration signal before correction, the correction trend polynomial of the displacement time history is obtained by fitting with a polynomial with constant term and first order term being 0, and the acceleration trend polynomial considering the baseline shift trend of the displacement time history is obtained by twice differentiating the correction trend polynomial of the displacement time history; The acceleration trend polynomial considering the baseline shift trend of the displacement time history is substituted into the acceleration before correction, and the baseline correction of the acceleration signal considering the curve shift of the displacement time history is completed.

[0016] Preferably, the correction trend polynomial of the velocity time history is specifically expressed as: In the formula, t is the current time, is the initial value of time, i is the i th point, and M is the highest order of the acceleration trend polynomial; is the coefficient of the fitting polynomial; The acceleration trend polynomial considering the baseline shift trend of the velocity time history is specifically expressed as: The correction trend polynomial of the displacement time history is specifically expressed as: The acceleration trend polynomial considering the baseline shift trend of the displacement time history is specifically expressed as:

[0017] Compared with the prior art, the present application has the following beneficial effects: The present application overcomes the drawbacks of the prior art that the seismic failure mode of the slope with a ductile shear band is not considered from the monitoring physical quantity inside the slope and the characteristic parameters of the slope; the prior art fails to analyze the slope reinforcement from the energy transmission point of view; the present application identifies the seismic failure mode of the slope with a tunnel from the energy transmission point of view, and provides a new method for the research on the slope with a ductile shear band.

[0018] The present application breaks through the traditional statics analysis framework, and for the first time, deeply integrates geomechanics, seismic dynamics and energy dissipation theory, identifies the seismic failure mode of the slope with a ductile shear band from the time-frequency-energy point of view. The array sensor network (accelerometer) inside the slope and the numerical simulation of ground deformation are used to realize the stereoscopic collaborative observation of the "internal energy field-surface deformation field". The research is started from the characteristic parameters of the slope and the monitoring physical quantity inside the slope, especially the influence of the seismic energy of the rock and soil mass on the dynamic parameters thereof. ​​​​

[0019] This approach pioneered a Fourier transform-based time-frequency energy decoupling algorithm, visualizing the energy transfer path of the seismic wave-rock-soil-ductile shear zone system, overcoming the frequency-domain limitations of traditional response spectrum analysis. A correlation model between seismic motion parameters and slope instability thresholds was established, revealing the local deformation and dynamic evolution of the ductile shear zone. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flow chart of the method of the present invention; Figure 2 This is a schematic diagram of a vibration table test model according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the arrangement of an acceleration sensor according to an embodiment of the present invention; Figure 4 This is a graph showing the acceleration time history before seismic wave filtering according to an embodiment of the present invention; Figure 5 This is a time history curve of acceleration after seismic wave filtering according to an embodiment of the present invention; Figure 6 This is the third group of manually fitted seismic wave time history curves in an embodiment of the present invention; Figure 7 This is a flowchart of baseline correction for incompatible initial acceleration according to the present invention. DETAILED DESCRIPTION

[0021] Example 1: Figures 1-7 As shown in Figure 2, the identification method of the seismic response law of the slope containing the ductile shear zone in the shaking table test includes: S1. Based on the rock mass mechanical parameters and Buckingham π similarity theorem, a shaking table similarity material test was conducted to construct a physical model of the slope containing a ductile shear zone.

[0022] In S1, the rock mass mechanical parameters include: conventional triaxial compression tests are carried out on the micro-neodacite, weak unloading dacite, strong unloading dacite, and ductile shear zone rock samples in the study area through on-site sampling, and recommended values ​​of mechanical parameters are proposed for various rock masses in the study area based on existing actual conditions.

[0023] 1) Slope model production: Materials were selected based on Buckinham's π similarity theorem. Cast-in-place was used, pouring the material step by step from bottom to top. The material was compacted every 10 cm before pouring the next layer. Before pouring the next layer, the compacted portion of the first layer was scraped to ensure a tight connection. To prevent relative displacement at the bottom of the model, a layer of 20-mesh coarse quartz sand was laid on the bottom of the model box to increase friction and prevent relative sliding.

[0024] S2. Arrange acceleration sensors in the horizontal and vertical directions from the slope surface to the inside of the slope.

[0025] In S2, the arrangement of the acceleration sensor includes arranging a plurality of slope surface monitoring points along the ductile shear zone line, and then drawing a slope surface monitoring line along the interface between the ductile shear zone and the dacite.

[0026] The slope surface monitoring points (A1-A7-A12-A16-A19-A20) are named as the slope surface monitoring line. The monitoring points on the four horizontal detection lines with different elevations in the slope (A1-A2-A3-A4-A5-A6, A7-A8-A9-A10-A11, A12-A13-A14-A15, A16-A17-A18) are named as No. 1 horizontal monitoring line, No. 2 horizontal detection line, No. 3 horizontal monitoring line, and No. 4 horizontal monitoring line from low elevation to high elevation, respectively, and are marked as SP1, SP2, SP3, and SP4, respectively. The monitoring points on the four detection lines along the interface between the ductile shear zone and the dacite (A6-A11-A15-A18-A20, A4-A9-A13-A16, A4-A9-A13-A16, A3-A8-A12) are named as No. 1 interface detection line, No. 2 interface monitoring line, No. 3 interface monitoring line, and No. 4 interface detection line from inside to outside, respectively, and are marked as J1, J2, J3, and J4, respectively.

[0027] In S3, the shaking table test is performed until the model is completely destroyed, and the original data are recorded.

[0028] S3 includes loading a plurality of groups of artificial fitting seismic waves. After the loading of the artificial fitting seismic waves is completed, the input waves are loaded in the order from low frequency and low amplitude to high frequency and high amplitude until the slope physical model is completely destroyed, and the original data are recorded. The input waves adopt two types of fitting seismic wave data and sinusoidal wave in the research area. The sinusoidal wave with different frequencies and different amplitudes is loaded in the X direction and the Z direction. The different frequencies include 5 Hz, 15 Hz, and 25 Hz. The different amplitudes include 0.1g, 0.2g, 0.3g, 0.4g, 0.5g, 0.6g, and 0.8g.

[0029] In S4, the original data are processed and analyzed, and the acceleration response analysis is performed.

[0030] The frequency similarity coefficient of the shaking table and the working frequency range of the shaking table are 100 Hz. Therefore, the original data are subjected to 50 Hz low-pass filtering to avoid distortion of the input data caused by external vibration or noise.

[0031] Baseline correction: the filtered data are subjected to baseline correction of initial acceleration incompatibility by using spectr software; The detailed steps of the baseline correction are as follows: The acceleration, velocity, and displacement time histories before correction are respectively defined as , and , the corrected acceleration, velocity and displacement time histories are , and ; The corresponding trend polynomials are , and ; they have the following relationships: ; (1) ; (2) ; (3) First step: integrate the uncorrected acceleration signal once to get the velocity time history , and fit the polynomial with zero constant term to get the corrected trend polynomial of the velocity time history as follows: ; (4) In equation (4), t is the current time, is the initial value of time, i is the i-th point, and M is the highest order of the acceleration trend polynomial, i.e., the correction order; is the coefficient of the fitting polynomial; According to the derivative relationship between velocity and acceleration, the acceleration trend polynomial considering the baseline offset trend of the velocity time history can be obtained by differentiating equation (4); ; (5) Substitute equation (5) into equation (1) to complete the baseline correction of the acceleration signal considering the curve offset of the velocity time history; here, the trend polynomial with zero constant term is used to avoid eliminating the fitting trend information by the above differentiation operation; Second step: integrate the uncorrected acceleration signal twice to get the displacement time history , and fit the polynomial with zero constant term and first-order term to get the corrected trend polynomial of the displacement time history as follows: ; (6) where is the coefficient of the fitting polynomial; twice differentiation of the above equation can obtain the acceleration trend polynomial considering the baseline offset trend of the displacement time history ; ; (7) The baseline correction of the acceleration signal considering the displacement time history curve offset can be completed by substituting formula (7) into formula (1), where the constant term and the first-order term of the trend polynomial are 0, and the purpose is to avoid the derivative operation eliminating the trend information of the fitting.

[0032] Acceleration response analysis With the increase of frequency and amplitude, the dynamic response of the slope model is stronger. Under the same frequency and amplitude, the horizontal dynamic response is stronger than the vertical dynamic response, and the difference increases with the increase of amplitude and frequency.

[0033] The dynamic response of the excavation slope containing ductile shear zone under seismic action has obvious elevation amplification effect and surface tendency effect. Under horizontal seismic load, the maximum RPHA on the surface of the slope reaches 1.89. Under vertical seismic load, the maximum RPVA at about 4 / 9 height of the slope surface reaches 1.163. Under horizontal seismic wave loading, the ductile shear zone has energy absorption effect, which strengthens with the increase of thickness. The higher the elevation, the more obvious the energy absorption effect of the thicker ductile shear zone, and the less obvious the energy absorption effect of the thinner ductile shear zone. Under the influence of vertical seismic wave, the thicker ductile shear zone still has energy absorption effect on the seismic wave, and the thinner ductile shear zone close to the ductile shear zone shows amplification effect on the seismic wave.

[0034] Under horizontal and vertical seismic action, along the ductile shear zone layer to the top of the slope, the RPHA and RPVA of each monitoring point in the slope model show a growth trend. Along the horizontal plane to the slope surface, the RPHA and RPVA of each monitoring point in the slope model show a nonlinear growth trend. The surface tendency effect and elevation amplification effect of the excavation slope containing ductile shear zone are obvious.

[0035] The Flac3D finite difference numerical software is used to establish a true three-dimensional model of the engineering slope. First, the stability of the slope in the study area is analyzed, and then the slope after excavation is loaded with seismic motion to analyze the dynamic response characteristics and dynamic stability.

[0036] The numerical simulation results of the excavation slope containing ductile shear zone under seismic action show that the dynamic response law of the excavation slope under seismic action is basically consistent with the physical test results, showing obvious elevation amplification effect and surface tendency effect, and the energy absorption effect of the ductile shear zone strengthens with the increase of elevation. After the action of seismic motion, the X-direction horizontal displacement increases by about 2-4 times, and the Z-direction horizontal displacement changes from vertical upward due to unloading rebound of the excavation rock mass to movement towards the valley, with a maximum difference of 4 cm. Compared with the unseismic state, the plastic zone extends along the strike of the ductile shear zone with a large amount of shear deformation zone, and extends towards the steep slope surface. A continuous shear deformation zone appears along the strong unloading bottom boundary, which is connected with the ductile shear zone, and the maximum shear stress increment reaches 7.624×10 -4 MPa.

[0037] The deformation and failure mode of the slope containing a ductile shear band under the action of earthquake is a'slip-tension' type failure. According to the deformation and failure characteristics of the slope model, the dynamic deformation process of the slope model is divided into five stages: ① low excitation intensity period, the slope has no obvious deformation; ② initial deformation stage of the slope model, local development of micro cracks; ③ slope model deformation expansion stage, the existing cracks in the slope model continue to extend and expand, and new cracks develop; ④ slope model deformation development stage, with the development of larger cracks as the slip bottom boundary and the rear edge, instability trend appears; ⑤ slope model failure stage, the slope develops cracks or strong unloading layer at a certain height as the slip bottom boundary to the free surface, driving the rear edge crack tension, and finally'slip-tension' type instability occurs.

[0038] The present application overcomes the drawbacks of the previous seismic failure mode of the slope containing a ductile shear band, which does not consider the monitoring physical quantity inside the slope containing a ductile shear band and the characteristic parameters of the landslide body itself; solves the problem that in the previous research on the seismic failure mode of the slope containing a ductile shear band, the reinforcement of the slope containing a ductile shear band is only analyzed from the macroscopic phenomenon, and the reinforcement of the slope is not carried out from the energy transfer angle; the present application identifies the seismic failure mode of the slope containing a tunnel from the energy transfer angle, and provides a new method for the research on the slope containing a ductile shear band.

Claims

1. A method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test, characterized by: The steps include: S1. Conduct shaking table similarity material tests based on rock mass mechanical parameters and Buckingham π similarity theorem to construct a physical model of the slope containing a ductile shear zone; S2. Arrange acceleration sensors in the horizontal and vertical directions from the slope surface to the slope interior; S3, conduct a shaking table test until the model is completely destroyed and record the raw data; S4. Process and analyze the original data and perform acceleration response analysis.

2. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 1, characterized in that: In S1, the rock mass mechanical parameters include: conventional triaxial compression tests are conducted on micro-neodacite, weak unloading dacite, strong unloading dacite, and ductile shear zone rock samples in the study area through on-site sampling, and recommended mechanical parameter values ​​are proposed for various rock masses in the study area based on existing actual conditions.

3. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 2, characterized in that: Materials were selected according to Buckinhamπ similarity theorem, and cast-in-place was used, pouring step by step from bottom to top. Every 10cm of pouring was compacted before pouring the next layer. Before pouring the next layer, the compacted part of the first layer was scraped and quartz sand was laid on the bottom of the model box.

4. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 1 is characterized in that: In the above S2, arranging the acceleration sensors includes setting a number of slope surface monitoring points at intervals along the ductile shear zone line, and then delineating a slope surface monitoring line along the interface between the ductile shear zone and the dacite.

5. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 1, characterized in that: The S3 includes loading several groups of artificial fitting seismic motions. After the artificial fitting seismic motion loading is completed, the input waves are loaded in sequence from low frequency and low amplitude to high frequency and high amplitude until the slope physical model is completely destroyed and the original data is recorded.

6. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 5, characterized in that: The input wave adopts two types: fitting earthquake motion data of the study area and sine wave, and loads sine waves with different excitation directions, frequencies and amplitudes.

7. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 6, characterized in that: The excitation directions include X and Z directions; the different frequencies include 5 Hz, 15 Hz, and 25 Hz; and the different amplitudes include 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, and 0.8 g.

8. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 1, characterized in that: The raw data were low-pass filtered at 50 Hz, and the filtered data were baseline corrected for initial acceleration incompatibility using Spectr software.

9. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 8, characterized in that: The baseline correction comprises the following steps: The acceleration, velocity and displacement time history before correction and the acceleration, velocity and displacement time history after correction are defined respectively, and then the corresponding trend polynomials are obtained; The acceleration signal before correction is integrated once to obtain the velocity time history, and the velocity time history is fitted with a polynomial with a constant term of 0 to obtain the correction trend polynomial of the velocity time history; According to the derivative relationship between velocity and acceleration, the acceleration trend polynomial that takes into account the baseline offset trend of the velocity time history is obtained by deriving the correction trend polynomial of the velocity time history. Substituting the acceleration trend polynomial that takes into account the velocity time history baseline offset trend into the acceleration before correction, the baseline correction of the acceleration signal that takes into account the velocity time history curve offset is completed; The acceleration signal before correction is integrated twice to obtain the displacement time history. A polynomial with both constant term and first-order term of 0 is used to fit the displacement time history correction trend polynomial, which is then differentiated twice to obtain the acceleration trend polynomial that takes into account the displacement time history baseline offset trend. The acceleration trend polynomial that takes into account the displacement time history baseline offset trend is substituted into the acceleration before correction to complete the baseline correction of the acceleration signal that takes into account the displacement time history curve offset.

10. The method for identifying the seismic response law of a slope containing a ductile shear zone in a shaking table test according to claim 9, characterized in that: The correction trend polynomial of the speed time history is specifically expressed as: ； Where t is the current time, is the initial value of time, i is the i-th point, and M is the highest order of the acceleration trend polynomial; are the coefficients of the fitted polynomial; The acceleration trend polynomial considering the velocity time history baseline offset trend is specifically expressed as: ； The correction trend polynomial of the displacement time history is specifically expressed as: ； The acceleration trend polynomial that takes into account the displacement time history baseline offset trend is specifically expressed as: 。

Images