• Volume 42,Issue 3,2020 Table of Contents
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    • >结构抗震
    • Seismic Behavior of Reinforced Concrete Columns with PermanentTemplate of Ultra-High-Performance Concrete

      2020, 42(3):579-588,606. DOI: 10.3969/j.issn.1000-0844.2020.03.579

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      Abstract:To examine the seismic behavior of reinforced concrete (RC) columns with prefabricated ultra-high-performance concrete (UHPC) permanent templates and check whether the prefabricated permanent templates are stripped from the surface of the specimen under low-cyclic repeated loading. Pseudo-static tests were conducted for the comparative purpose of six permanent template columns (PTC) and one RC column with varying axial load ratio, shear span ratio, stirrup spacing, and concrete cover. The failure pattern, hysteretic characteristics, deformation capacity, energy dissipation capacity, and stiffness degradation of permanent template columns were studied. Test results showed that the permanent templates that were perpendicular to the direction of loading stripped at about 70% of the peak load; the permanent templates that were stripped at the final destruction of the specimen parallel to the direction of loading. Within the same shear span ratio, axial load ratio, and several stirrups, the seismic behavior of the specimen with the UHPC template and 10 mm concrete as the cover is relatively better than others, but its bearing capacity and prophase stiffness are slightly reduced.

    • Shaking Table Tests of Shear Wall in Large Buildings underLong-Period Ground Motion

      2020, 42(3):589-595. DOI: 10.3969/j.issn.1000-0844.2020.03.589

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      Abstract:To optimize the shear wall structure of large buildings under long-period ground motion, the shaking table test was carried out. By analyzing the difference between ordinary and long-period seismic waves, it was proved that the long-period seismic waves feature significantly long-period components. Taking the shear wall of a high-rise hotel as the research case, the construction process and sensor layout of the simulation experimental platform were designed, and the scale of the building model was set to 1:10. Moreover, CA wave, RG wave, and EL wave were chosen as the experimental seismic waves, and the seismic performance of shear walls in large buildings was evaluated from many aspects. The results of shaking table test show that under the same displacement, the ultimate bearing capacity of the building under long-period seismic wave was the smallest. Under the CA wave, RG wave, and EL wave, the natural period of the model changed, and under the action of the EL wave the natural period was always slightly longer than the basic period. Under different seismic waves, the interlayer shear force in the X and Y directions tended to be the same. Under the action of the CA wave and EL wave, the X-direction displacement ratios were relatively close, while the Y-direction displacement ratios of shear walls were quite different under the action of the three seismic waves. Under the action of long-period seismic waves, the shear walls of large buildings were most severely damaged. It is hoped that this study can provide the foundation for the shaking table test of the optimization design of shear walls in large buildings.

    • Characteristics of the Measured Dynamic Response of GuandiDam during the MS5.1 Earthquake in Xichang

      2020, 42(3):596-606. DOI: 10.3969/j.issn.1000-0844.2020.03.596

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      Abstract:At 16:29 on October 31, 2018, an MS5.1 earthquake occurred in Xichang, Sichuan Province. The epicenter of the earthquake was 26 km from Guandi Dam. The earthquake process was completely recorded by the strong motion station on Guandi Dam. On the basis of the recorded strong motion data, the dynamic response characteristics and law of Guandi Dam during the Xichang earthquake are investigated by analyzing the time history characteristics and frequency spectrum response law of each measuring point. Results show that the PGA ranges from 3.70 gal to 69.98 gal in various parts of the dam, and the instrument intensity ranges from 1.8 degree to 5.2 degree. Affected by the direction of the Xichang earthquake rupture, the three-component peak value and spectral characteristics of strong motion show an obvious directional amplification effect with the increase in elevation. Moreover, the overall performance indicates that the longitudinal component is larger than the transverse and vertical components. The response period of the earthquake is less than the characteristic period of the dam bedrock site, and the predominant period of the dam bedrock site under Xichang earthquake excitation is far from the natural vibration period of the dam, indicating that the earthquake has no impact on dam safety.

    • Simulation Analysis of Vibration Characteristics of IsolatedCurved Girder Bridges under Different Earthquakes

      2020, 42(3):607-612. DOI: 10.3969/j.issn.1000-0844.2020.03.607

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      Abstract:The simulation analysis of the seismic characteristics of curved bridges is of great significance to the isolation and damping of curved bridges. Based on the design characteristics of isolated curved bridges, a nonlinear horizontal spring unit was used to simulate the bidirectional nonlinearity of the lead rubber bearing. Using SAP2000, a strong earthquake was selected, and the characteristics of the curved bridge were considered. The vibration characteristics of the bridge were simulated and analyzed considering different earthquakes. The simulation results are as follows:In the inputting process of different seismic waves and peak accelerations, under small earthquakes, the horizontal stiffness of bearing was relatively large, and the structure was relatively stable; the horizontal stiffness of the bearing under large earthquakes was relatively small, and the restoring force-displacement hysteresis curve of the bearing was relatively large, which can dissipate the seismic input energy, thus effectively mitigating the seismic response and play the isolation effect.

    • Evaluation of Damping Effects of Building StructuresBased on Soil-Structure Interaction System

      2020, 42(3):613-623. DOI: 10.3969/j.issn.1000-0844.2020.03.613

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      Abstract:This paper presents a seismic assessment method for soil-structure interaction (SSI) based on the seismic records of soil-structure systems. A simplified SSI model is adopted, and the model parameters are determined through system identification. The SSI damping effect of the seismic response of a superstructure is decomposed into inertial interaction and kinematic interaction. Moreover, a method of reducing structural response by inertial interaction and motion interaction is proposed and used to analyze two middle-story buildings along the Pacific coast during the Tohoku-Oki earthquake of 2011. The results show that the damping effect of the inertial interaction decreases when the structural response of the building enters the inelastic range.

    • Influence of Eccentricity of the Upper Structure and BaseIsolation Layer on the Structural Seismic Response

      2020, 42(3):624-628,664. DOI: 10.3969/j.issn.1000-0844.2020.03.624

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      Abstract:With the development of base isolation technology, the engineering application of the technology in high-intensity areas in China is expected to become a trend. However, because of the rich and intriguing architectural functions and modeling, the mass center and stiffness center of the structure tend to be unevenly distributed. Taking a three-story steel frame structure as the analytical model, the nonlinear time-history analysis was carried out under one-directional horizontal seismic action using SAP2000, and three schemes were designed:the uneven distribution of the superstructure mass center, uneven distribution of the isolation layer mass center, and uneven distribution of the isolation layer stiffness center. The analysis results showed that the eccentricity of the mass center of the superstructure and isolation layer has a great influence on the torsion effect and seismic response of the structure, and reducing the eccentricity of the superstructure has the most significant effect on the horizontal seismic response of the structure. The eccentricity of the stiffness center of the isolation layer has a greater influence on the superstructure compared with the eccentricity of the mass center; therefore, it is more effective to control the eccentricity of the isolation layer stiffness center in isolation design.

    • Shaking Table Test of a Liquid Storage TankConsidering Pile—Soil Interactions

      2020, 42(3):629-638. DOI: 10.3969/j.issn.1000-0844.2020.03.629

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      Abstract:To study the dynamic response of a liquid storage tank considering pile-soil interactions and the effect of long-period seismic waves on the liquid sloshing and tank uplift, a pile-soil-storage tank model was designed to perform a shaking table test based on dimensional analysis. In the experiment, four bedrock waves and four surface waves were used. The system change laws obtained when bedrock waves and surface waves were used as input were the same. The surface acceleration was amplified, and the magnification factor of surface acceleration decreased with increasing PGA as input. Under the action of general ground motion, increases in PGA input result in approximately linear increases in the shaking wave height of the stored liquid; by comparison, under the action of long-term ground motion, a nonlinear increase is observed, and the shaking wave height of the liquid is large. In addition, the wave height generated by the liquid is related to the tank type. The uplift height of the storage tank increases nonlinearly with increasing PGA input and is less than that under general ground motions under the excitation of long-period ground motions. The influence of long-period seismic waves should be considered in the design of storage tanks.

    • Seismic Risk Assessment of High-speed Railway ContinuousGirder Bridges Based on Fuzzy Theory

      2020, 42(3):639-645. DOI: 10.3969/j.issn.1000-0844.2020.03.639

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      Abstract:In this paper, based on fuzzy theory, we propose a seismic economic risk assessment method for bridge systems and take a high-speed railway continuous girder bridge as an example. We adopted a fuzzy comprehensive evaluation method and performed combined damage analyses of the displacement-based support and sections of a curvature-based pier. The results showed that the proposed analysis method of the fuzzy seismic economic risk for bridge systems can comprehensively and accurately calculate the economic losses of continuous girder bridges under earthquake. We found the error for the seismic economic loss to be larger when pier components are used to represent the whole bridge. This framework method for determining the annual expected risk of loss based on fuzzy theory can comprehensively assess the direct economic risk of a high-speed railway continuous girder bridge based on the probabilistic characteristics of the structural seismic performance. In addition, this method can be used to make reasonable evaluations of the seismic design, maintenance, reinforcement, and post-disaster reconstruction of high-speed railway continuous girder bridges.

    • >地震科学技术与观测
    • Application of the Modified Chirp-Z Transform in SpectrumAnalysis of Air-gun Seismic Source Signals

      2020, 42(3):646-652. DOI: 10.3969/j.issn.1000-0844.2020.03.646

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      Abstract:The air-gun seismic source signal is a kind of short-time non-stationary signal, and the spectral zoom algorithm can improve the accuracy of the spectral analysis of such signals. In this study, the error simulation calculations of the two spectral analysis algorithms of a modified chirp-Z transform (MCZT) and fast Fourier transform (FFT) were carried out. Second, the underwater wavelet signal and seismic wave signal of the air-gun seismic source were calculated and compared. The results show that the MCZT algorithm has a smaller error and its computation time is less than that of the FFT. It can effectively improve the extraction accuracy of the frequency and amplitude feature of air-gun seismic source signals. This indicates that the MCZT algorithm is an effective method to analyze the spectrum characteristics of air-gun seismic source signals.

    • Time-Frequency Characteristics of Ground Motions Based on a Wavelet Transform

      2020, 42(3):653-664. DOI: 10.3969/j.issn.1000-0844.2020.03.653

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      Abstract:3 551 sets of earthquake records from the NGA database of America were grouped according to site conditions, moment magnitude, and epicentral distance.The wavelet power spectrum of each record was calculated using a one-dimensional continuous wavelet transform.The predominant frequency corresponding to the maximum value of the wavelet power spectrum at every time was investigated.Results showed that the predominant frequency of ground motion gradually decreased with time, and the time-variation of the predominant frequency of the vertical component seemed more remarkable than that of the horizontal component.Furthermore, a linear function model, together with an exponential model and an exponential trigonometric model, were used to fit the time-varying curves of predominant frequency under varying magnitudes.Epicentral distance, effects of site conditions, moment magnitude, and epicentral distance on the time-varying curves of predominant frequency were analyzed.Time-varying curves of horizontal and vertical frequencies decreased with time and decayed more quickly in the vertical direction.In most cases, the high-frequency components were higher in the vertical records than those in the horizontal records.

    • Anomalies of Thermal Infrared Brightness Temperature Beforethe Hualien, Taiwan Earthquake Swarm on February 2018

      2020, 42(3):665-670. DOI: 10.3969/j.issn.1000-0844.2020.03.665

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      Abstract:To resolve the obvious thermal infrared anomalies before the Hualien, Taiwan earthquake swarm on early February 2018, the TBB data of the national geostationary meteorological satellite FY-2G were collated in this study, and the anomalies were analyzed and extracted using the wavelet transform and relative power spectrum. Results showed that the thermal infrared anomaly range of the Hualien, Taiwan earthquake swarm was mainly distributed in the southwestern part of the epicenter area, and the phenomenon of power spectrum enhancement occurred approximately 8 months before the earthquake. With time, the abnormal range extended, and the longitudinal valley fault zone expanded gradually within approximately 2 months, with the largest amplitude exceeding 14.

    • Diurnal Variation and Mechanism of Differences inGeoelectric Storms in Jiayuguan and GuazhouGeoelectric Fields, Gansu Province

      2020, 42(3):671-679. DOI: 10.3969/j.issn.1000-0844.2020.03.671

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      Abstract:Diurnal variations in the geoelectric field at Jiayuguan and Guazhou stations are studied using the observation data of the geomagnetic field at Jiayuguan Station in Gansu. Changes in geoelectric storms are explored with the method of time-sequence superposition residual. Results show that (1) the static diurnal variations in the geoelectric field at the two stations appear as two obvious undulating changes without a phase difference, and the ranges of diurnal variations at the two stations are different. (2) The component variation in the geoelectric field is significantly correlated with the orthogonal component variation in the geomagnetic field. The waveforms of diurnal variation in geoelectric and geomagnetic fields are different. The dominant periods of the two stations are 12, 8, and 24 h after the high-frequency change is removed, and the dominant periods become 24, 12, and 8 h after the geomagnetic storm effect is eliminated. (3) During an electromagnetic storm, the correlation between geoelectric and geomagnetic fields is obviously reduced. During a magnetic storm, the change rate of Y is significantly correlated with EY of the geoelectric field. This result indicates that the differences between daily variations in the two stations are related to the underground conductivity of station sites. The diurnal variation in the geoelectric field is mainly caused by solar wind-induced ionospheric activity. A geoelectric storm may be attributed to many factors, such as shallow and deep resistivities and geological structures between the two stations.

    • Influence of the Subway on Deep-well Resistivity Observation: A Case Study of Jiangning Station

      2020, 42(3):680-687. DOI: 10.3969/j.issn.1000-0844.2020.03.680

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      Abstract:Jiangning station in the city of Nanjing is less than 3.2 km from the S1, S7, and S9 Metro Lines and the subway can have a significant effect on deep-well observations. In this paper, the station's deep borehole resistivity observation data from 2016 to 2018 were analyzed in conjunction with some test schemes of the subway. Three kinds of interference characteristics have been found:positive and negative impulse jumping, ascending, and descending. The mechanisms of these changes were briefly discussed. The maximum variation range of surface and deep-well geo-electric observation data was also compared. The results showed that short polar distance observation can minimize subway interference; as the subway line increases, the interference increases correspondingly; subway trial interference operating on geo-electric observation is typically greater than that of formal subway operation.

    • Method of Extracting Earthquake Precursor Anomalies Based onthe Linear Polarization Characteristics of a Geoelectric Field

      2020, 42(3):688-695,713. DOI: 10.3969/j.issn.1000-0844.2020.03.688

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      Abstract:In this study, the observation data of a geoelectric field at Pingliang Station were collected from 2008 to 2017. The linear polarization and nonpolarization anomalies of the geoelectric field were analyzed, and a method for extracting seismic precursor anomalies was proposed on the basis of the linear polarization characteristics of the geoelectric field. Periodic properties, polarization coefficient, polarization direction, and projection in a vertical polarization direction were discussed with a relative data processing method. The following normal background characteristics of the linear polarization of the geoelectric field at Pingliang Station were obtained. The polarization direction varies within N(66.7±6)° E, and the polarization coefficient is between 0.7 and 1. The fluctuation range of the projection value in the vertical polarization direction varies from -0.53 mV/km to 2.61 mV/km. The relationship between moderate and strong earthquakes around Pingliang Station and the nonpolarization anomaly of the geoelectric field was analyzed statistically. Results showed that the geoelectric field at this station can reflect earthquakes. The nonpolarization anomaly of the geoelectric field can be used as an important indicator of earthquake precursor anomalies; that is, the duration from nonpolarization before the earthquake to polarization recovery after the earthquake generally ranges from 4 days to 15 days and occurs mostly within 5 days to 1 month before the earthquake.

    • Evaluation of the Forecasting Effectiveness of the Short-term AftershockOccurrence Rate and Forecasting Strategy in Qinghai Region

      2020, 42(3):696-704. DOI: 10.3969/j.issn.1000-0844.2020.03.696

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      Abstract:To evaluate the forecasting effectiveness of the occurrence rate of short-term aftershocks in the Qinghai region, and to construct an early aftershock forecasting strategy and forecast index system that reflects the regional seismic activity, we performed a continuous and sliding fitting of the sequence parameters of eight earthquakes that have occurred in the Qinghai area since 2009. To do so, we used the epidemic-type aftershock sequence (ETAS) model and the ETAS-based thinning algorithm, and used the N-test method to evaluate the forecasting effectiveness. The prediction results show that the ETAS model and ETAS-based thinning algorithm have good forecasting ability regarding the aftershock occurrence rate in the Qinghai region. We found that the "best" forecasting result may be obtained using a 3-day forecasting time window and applying the algorithm in the early stage of the sequence.

    • Characteristics and Difference of Trace Hydrogen in EscapeGas from Geothermal Hot Spring Well and Soil

      2020, 42(3):705-713. DOI: 10.3969/j.issn.1000-0844.2020.03.705

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      Abstract:Hydrogen is known as one of the most useful types of gas for detecting fault activity. The hydrogen concentration is susceptible to temperature, air pressure, and other factors because of its sensitivity. This study made the first attempt at continuous hydrogen observation in the geothermal hot spring well and the soil simultaneously. The differences in dynamic variation characteristics of trace hydrogen escaped from the geothermal hot spring well and the soil was analyzed, and the causes of hydrogen anomalies in geothermal hot spring well were discussed. Spectrum analysis showed that there arediurnal variations of hydrogen escaped from both the hot spring and the soil. The concentration of hydrogen escaped from the geothermal well is related to the well's water level and temperature but has no relation to environmental factors on the soil. The trace hydrogen released from the soil is mainly influenced by the surface environmental conditions, it is positively correlated with air temperature and negatively correlated with air pressure. The abnormality of a sudden rise in hydrogen escaped from the geothermal hot spring well originated from the bubble carried by the upwelling fluid, which is a non-seismic precursor anomaly.

    • Textual Research on the 1765 Zhuoni-Kangle Earthquake inGansu Province and Its Causative Structure

      2020, 42(3):714-720,758. DOI: 10.3969/j.issn.1000-0844.2020.03.714

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      Abstract:According to a textual research on historical materials, the Zhuoni-Kangle earthquake on May 1, 1765, occurred around Liulin and Zongshi villages near the Taohe River. It had a magnitude of about 6 and an epicenter intensity of eight. The long axis direction of the extreme seismic area was roughly consistent with the eastern segment of the Guomatan fault. A field investigation revealed that the Guomatan fault had a new activity near the extreme seismic zone, which was characterized by a left-lateral strike-slip fault with normal components. The fault dipped NE, and geomorphological signs such as fault ridges and gully dislocations were preserved along the fault. The analysis of the tectonic stress field in this area also indicated that the Zhuoni-Kangle earthquake occurred in the sinistral step between the Guomatan fault and the Zhangxian-Huangxianggou fault, which is caused by the stress concentration at the intersection and end points of the fault zone. Our comprehensive analysis suggested that the Guomatan fault served as the seismogenic structure of the Zhuoni-Kangle earthquake.

    • >岩土工程与抗震
    • Theory, Technology, and Application of Shaking TableModel Tests of High Earth-Rockfill Dams

      2020, 42(3):721-731. DOI: 10.3969/j.issn.1000-0844.2020.03.721

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      Abstract:The theory and technology of shaking table model tests on earth-rockfill dams are systematically described and discussed. A model similarity design method based on static and dynamic characteristics tests of a prototypical model dam, and a vibration test method using input from ground motions of different intensities are proposed. Based on the performance parameters of a 1g large-scale shaking table and ng super-gravity centrifuge-shaking table equipment, advantages and disadvantages of shaking table model tests of earth-rockfill dams were analyzed. Combined with existing projects, the application of shaking table tests in earth-rock dam engineering was summarized. The evolution law of structural dynamic characteristics of a high concrete-faced rockfill dam under many strong earthquakes was studied.

    • Shaking Table Test on the Dynamic Response of a PileFoundation in an Inclined Liquefiable Site

      2020, 42(3):732-741. DOI: 10.3969/j.issn.1000-0844.2020.03.732

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      Abstract:To study the dynamic response of pile foundations in inclined liquefiable sites, a series of shaking table model tests on the interaction of bridge pile-soil in sloping liquefiable sites were carried out, based on the Dallington Bridge damage in the New Zealand earthquake of 2011. Macroscopic phenomena such as soil liquefaction, ground cracks, and soil flow were reproduced. Results indicated that the liquefaction potential and inertia of the soil layer were necessary conditions for lateral spreading in the sloping site. Shallow soil was easier to liquefy than the deep soil, and the acceleration in the liquefaction layer gradually decreased from bottom to top, while that in the non-liquefaction layer showed an opposite characteristic. Lateral earth pressure around piles in deep soil is clearly greater than that in shallow soil, and soil liquefaction can weaken earth pressure on the pile structure. Maximum structural strain was located at the upper bridge abutment, while two large values of bending moment appeared in the middle of pile and the soil layer interface. The main reasons for the two large bending moments were the pile end embedding and soil flow at the inclined site.

    • Seismic Behavior of the Composite Retaining Structures inCase of Nuclear Power Plants in High Soft-RockSlopes under Strong Earthquakes

      2020, 42(3):742-750. DOI: 10.3969/j.issn.1000-0844.2020.03.742

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      Abstract:Based on the progress of the case study conducted on high slopes of domestic nuclear power plants, a high soft-rock slope that interacts with clay in a nuclear power plant has been selected as an example in this study to comprehensively analyze the dynamic amplification effect, seismic performance, and reinforcement effect under earthquake action using various methods. Initially, we use a pseudo-static method to obtain a preliminary reinforcement design of the slope. Next, we analyze the dynamic amplification effect of the slope as well as the dynamic response and seismic performance of the retaining structures based on the shaking table test and numerical calculation results. Furthermore, we discuss the optimization value of the seismic parameters of the slope. The research results denote that (1) the acceleration amplification factor of the in situ slope increases with an increase in height, the magnification factor of mudded intercalation after saturation is greater than that before saturation, and the maximum value of the factor in the horizontal direction is 1.90; (2) the dynamic amplification factor significantly decreases after reinforcement, and the maximum factor in the horizontal direction is 1.31, whereas the maximum factor in the vertical direction is 1.0 (note:no amplification effect in the slope below the anti-slide pile with the anchor cable indicates that the seismic performance of high soft-rock slope is good when using an anti-slide pile with an anchor cable and the anchor-cable framework); (3) the overall seismic performance of the slope is good for PGA=0.21g, and only the force value of the anchor cables at the top and middle parts of the slope exceed the design value by up to 20% and 5%, respectively; and (4) the acceleration amplification factor distribution obtained via numerical calculations is in good agreement with the shaking table test results. Furthermore, the acceleration amplification factors obtained by the two methods are very close. The research results can provide technical support to conduct seismic safety evaluation and obtain engineering design for high and steep soft-rock slopes in case of nuclear power plants.

    • Temperature Response Characteristics of Crack Deformationof Typical Earthen Sites in Jiayuguan

      2020, 42(3):751-758. DOI: 10.3969/j.issn.1000-0844.2020.03.751

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      Abstract:Fractures, gullies, gouges, and stripping are typical distortions of earthen sites in Northwest China. To explore the change laws of earthen sites and their occurrence environment, it is important to theoretically and practically investigate the deformation monitoring of these sites. In this study, two cracks of the Jiayuguan earthen site are investigated. By analyzing the monitoring data of fracture deformation and environmental temperature in 2016, the response relationship between them was found, and the influence law of environmental temperature on fracture development was explored. By using correlation analysis and normalization processing data and combining the support vector machine method, the fracture development trend was predicted, thus providing a theoretical basis for studying the fracture development trend of earthen sites.

    • Experimental Study on the Effect of Single Tamping Energy onDynamic Compaction Reinforcement inLarge-Thickness-Loess Area

      2020, 42(3):759-763. DOI: 10.3969/j.issn.1000-0844.2020.03.759

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      Abstract:A series of tests was carried out to study the dynamic compaction parameters of a large-thickness-loess foundation in a loess hilly region. The average settlement of each test area before and after dynamic compaction and the change law of the main physical and mechanical indexes of soil were analyzed. The main parameters were gained, such as the center distance of dynamic compaction points, impact number, and the effective reinforcement depth under energy levels of 6 000, 8 000, 10 000, and 12 000 kN·m. Hence, the empirical method of determining the effective reinforcement depth of dynamic compaction was given. The test results showed that the void ratio, dry density, and collapsibility coefficient of the reinforced loess can be used as the evaluation indexes of the reinforcement effect. If the physical and mechanical indexes of the ground soil after dynamic compaction meet the design requirements, the lower limit depth is the effective reinforcement depth. In the collapsible loess area with large overburden thickness, the lower limit depth of foundation soil after eliminating the collapsibility can be used as the effective reinforcement depth

    • Progress of the Application of the Multifunctional Cone PenetrationTest in the Seismic Liquefaction Discrimination Method

      2020, 42(3):764-776. DOI: 10.3969/j.issn.1000-0844.2020.03.764

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      Abstract:Seismic liquefaction is one of the direct causes of the instability of the foundation and damage to the upper structure, and the first step is to predict and judge the liquefaction of the project site. Therefore, the rationality and reliability of liquefaction discrimination method is an important part of geotechnical seismic investigation. As the main test of in situ technology, the cone penetration test (CPT) is widely used for discrimination of liquefaction due to its advantages of high speed, low cost and high efficiency. In line with the development of CPT technology in the country and abroad in recent years, the application of different CPT technologies in the assessment of earthquake liquefaction has been systematically summarized. In this article, a method of liquefaction discrimination based on state parameters was introduced especially, and the method based on statistical and probability analysis was introduced briefly. Then, the difference between the different liquefaction discrimination methods was compared and analyzed. Finally, based on the results of the existing research, the problems and deficiencies of the existing methods of CPT were studied. The results showed that the method based on state parameters can consider the effects of confinement pressure, stress and void ratio and connect the laboratory test and the field test effectively; The SCPTU and RCPTU liquefaction discrimination structures need to be expanded and improved; the probability and statistical analysis method needs to be combined with the corresponding software to make it more applicable.

    • >地震专辑与综合
    • Seismic Intensity Evaluation and Damage Characteristicsof Xiahe, Gansu MS5.7 Earthquake

      2020, 42(3):777-783. DOI: 10.3969/j.issn.1000-0844.2020.03.777

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      Abstract:On the basis of the estimated earthquake-affected area and by conducting an in situ investigation and disaster analysis, we drew a seismic intensity map and determined the damage characteristics of the Xiahe, Gansu M5.7 earthquake that struck on October 28, 2019. The maximum intensity of the earthquake was Ⅶ degree, the affected area measured 193 km2, and the VI degree area measured 1 398 km2. In the earthquake region, most houses were civil structures supported by wooden frames. In the meizoseismal area, the cob walls of most houses were severely cracked and collapsed, but their load-bearing timber frames only showed a slight tilt and partial damage without complete collapse. Most temples were basically intact and showed only slight cracks on specific walls. The disaster presented a zonal distribution along the distribution direction of the fault zone. The damage to the buildings on the mountainside were relatively severe, thereby indicating the obvious mountain amplification effect and slope effect of the earthquake. Considering these disaster characteristics, we offered a number of suggestions for enhancing the antiseismic performance of buildings and strengthening the publicity and education related to earthquake prevention and disaster reduction.

    • Characteristics of Strong Ground Motion Records of the Xiahe,Gansu M5.7 Earthquake on October 28, 2019

      2020, 42(3):784-790. DOI: 10.3969/j.issn.1000-0844.2020.03.784

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      Abstract:A M5.7 earthquake occurred on October 28, 2019 in Xiahe County, Gansu Province. The main shock fully triggered 18 strong motion stations in the China Digital Strong Motion Network (CDSMN), for which we obtained and processed 54 records of three-component acceleration. In this paper, we identify the ground motion parameters of the near-field stations and present the peak acceleration contours near the epicenter. We also compare the actual observed values with several commonly used ground motion prediction equations. After comparing the acceleration response spectra of the 62LBL and 62BLX stations with the design response spectrum in China, we summarize the characteristics of the response spectrum of the M5.7 earthquake. To study the site effect on the peak acceleration and peak velocity, the H/V method was used to perform a seismic site effect analysis of four typical stations.

    • Anomaly Characteristics of the Qinghai Underground FluidNetwork before the Xiahe M5.7 Earthquake

      2020, 42(3):791-798. DOI: 10.3969/j.issn.1000-0844.2020.03.791

      Abstract (337) HTML (0) PDF 8.80 M (985) Comment (0) Favorites

      Abstract:A series of anomalies occurred in the Qinghai underground fluid network before the Xiahe M5.7 earthquake on October 28, 2019. This paper selected the water level and temperature anomalies in the Menyuan and Pingan county, the water temperature anomalies in Zuoshu and Ledu, the water radon anomalies in Huangyuan and Xining, and the underground fluid network of Qinghai. The abnormal change pattern, time course and synchronization, and spatial distribution were analyzed, and the causes of the anomalies and relationship with the Xiahe M5.7 earthquake were discussed. It is believed that these anomalies were not caused by the activity of the Xiahe earthquake, but were the result of an overall change of the tectonic stress field in the northeastern Qinghai-Tibet Plateau. These anomalies are seismic field precursors and not source precursors.

    • Intrusion Detection of the Seismic Information NetworkBased on the Chaos Algorithm

      2020, 42(3):799-805. DOI: 10.3969/j.issn.1000-0844.2020.03.799

      Abstract (317) HTML (0) PDF 1.13 M (439) Comment (0) Favorites

      Abstract:The traditional machine-learning-based network intrusion detection method can only detect the known intrusion behavior and has the disadvantages of high false alarm rate and poor timeliness when detecting unknown intrusion behavior. In this study, a new seismic information network intrusion detection method based on the chaos algorithm is proposed. First, the candidate seismic information network feature-chaos variable mapping model is created to enable the transformation between variables, and the chaos variable iterative evolution algorithm is used to select seismic information network features. Then, the support vector machine is used to learn optimal features. Finally, to improve the detection accuracy of seismic information network intrusion, the Cauchy bee colony algorithm is adopted to optimize the parameters of the support vector machine, and the optimization model of network intrusion detection is established. The simulation experiment results show that the seismic information network intrusion detection method based on the chaos algorithm can effectively implement intrusion detection with high detection rate and low false alarm rate, thus having high application advantage.

    • A Control Method for the Integrated Audio Source Level of SeismicExploration Transponders Controlled by a Single-Chip Microcomputer

      2020, 42(3):806-811. DOI: 10.3969/j.issn.1000-0844.2020.03.806

      Abstract (306) HTML (0) PDF 3.17 M (464) Comment (0) Favorites

      Abstract:Previous control method of seismic exploration transponders cannot effectively reduce the interference of noise on the integrated audio of the transponder, which results in the existence of noise and affects the sound quality and effectiveness of the transponder. Therefore, a control method for the integrated audio source level of seismic exploration transponders controlled by a single-chip microcomputer is proposed. A seismic exploration transponder based on a single-chip microcomputer is constructed, which includes a power supply module, main control module, power amplifier module, matching module, receiving module, receiving/transmitting module, and receiving/transmitting transducer. The single-chip microcomputer is used to determine the working condition of the internal output, and the audio source level is identified on the basis of the optimization method of the integrated audio source layout. Results show that the proposed method can effectively enhance the integrated audio source level of the seismic exploration transponder controlled by the single-chip microcomputer. Moreover, the proposed method has a good denoising effect. The transponder controlled by the proposed method can provide better exploration results and improve the equipment for seismic exploration.

    • Key Design Techniques of a Lightning Protection System for theGeoelectrical Resistivity Monitoring Stations in the WinterOlympic Games Security Project

      2020, 42(3):812-817. DOI: 10.3969/j.issn.1000-0844.2020.03.812

      Abstract (332) HTML (0) PDF 4.93 M (544) Comment (0) Favorites

      Abstract:Lightning damage is one of the important factors that affect the stable operation of seismic stations; thus, it is of significance to protect the stations from lightning. This study introduced the design of a lightning protection system for the geoelectrical resistivity monitoring stations in the Winter Olympic Games security project. Through the analysis of problems in the key design techniques of the lightning protection system, the overall design of a comprehensive lightning protection system in terms of the aspects of grounding grid, power supply, and comprehensive wiring was discussed, and the lightning protection system at Baochang Station was designed. On this basis, the design of the lightning protection system of all eight stations in the project was completed, and the effectiveness of the lightning protection system of the stations was improved. In this study, some new technical achievements were attained, i.e., (1) the power supply and measuring lines were buried; (2) the buried power supply and measuring lines were more than 10 m from the grounding body; and (3) the network signal lightning arrester with corresponding current values was installed in the stations that still used overhead lines. These research results can be used as a reference for the construction of the lightning protection system for national stations in the future.

    • Testing Method of SKZ-3 Component Borehole Strainmeter

      2020, 42(3):818-824. DOI: 10.3969/j.issn.1000-0844.2020.03.818

      Abstract (360) HTML (0) PDF 4.14 M (1047) Comment (0) Favorites

      Abstract:The SKZ-3 component borehole strainmeter, which was developed on the basis of the principle of four-component self-checking, not only has the advantage of traditional geostress observation but can also monitor the high-frequency strain in the depths of the earth. Testing and calibration of the SKZ-3 component borehole strainmeter ensured the validity and reliability of observation data.

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