• Volume 42,Issue 2,2020 Table of Contents
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    • >结构抗震
    • Scaled Model Tests on the Dynamic Response of Polar Cranesin Nuclear Power Plants under Seismic Action

      2020, 42(2):283-289. DOI: 10.3969/j.issn.1000-0844.2020.02.283

      Abstract (799) HTML (0) PDF 4.64 M (897) Comment (0) Favorites

      Abstract:Based on the dimensional analysis theory, in this paper, we propose a similarity criterion for the dynamic response of a scaled polar crane in a nuclear power plant under earthquake action. We determine the similarity relation of dynamic responses between a prototype nuclear polar crane and the scaled model. As the shaking table input, we used the El Centro wave, and based on the seismic code requirement and similarity criterion, we scaled the input amplitude to 0.3g and 0.2g in the horizontal and vertical directions, respectively, with a time scale of 4. Comparing the maximum accelerations of the shaking table inputs, the scaled model experiment results showed that the peak acceleration in the middle-span of the crane girder increases 56.0% in the horizontal direction and 119.0% in the vertical direction, and the peak acceleration in the polar girder increases 66.7% in the horizontal direction and 43.5% in the vertical direction. These experimental results indicate that when the direction of the earthquake input is vertical to a crane girder, the horizontal peak acceleration in the middle span of the crane girder is maximum. When the earthquake input is parallel to the crane girder, the horizontal peak acceleration in the polar girder is maximum. The influence of the direction of the earthquake input on the vertical peak acceleration in polar girder is not significant. Under earthquake loading, the polar crane experiences no derailing phenomenon.

    • Fragility Analysis of Step-terrace Frame Structures onthe Slope under Mainshock and Aftershocks

      2020, 42(2):290-298. DOI: 10.3969/j.issn.1000-0844.2020.02.290

      Abstract (641) HTML (0) PDF 8.57 M (2413) Comment (0) Favorites

      Abstract:A strong earthquake commonly triggers the occurrence of multiple aftershocks. Three structures with different layers and crosses and an ordinary flat frame structure were designed with reference to the current codes of China. Based on the incremental dynamic analysis method, the Park-Ang damage index was adopted as the parameter of structural response, and the peak ground acceleration was used as the parameter of the ground motion intensity. Then, the vulnerability curves of the step-terrace structures and the ordinary flat frame structure under a mainshock and aftershocks were obtained. The vulnerabilities of the step-terrace structure and the ordinary flat frame structure were compared and analyzed, and the influence of aftershocks on the vulnerability of each structure was studied. The anti-collapse abilities of the structures were evaluated based on the collapse margin ratio (CMR), and the safety reserves of the structures were compared. The results show that the aftershocks increased the exceedance probability of the structure, and with the increase of the aftershock intensity, the exceedance probability was bigger. Compared with the ground structure, the exceedance probability of the step-terrace structure was higher, and the influence of the number of layers and the number of falling spans on the vulnerability of the structure was significant. Compared with the ordinary flat frame structure, the anti-collapse reserve coefficient of the step-terrace structure was small, and the anti-collapse safety reserve was lower. For the step-terrace structure, the increase in the number of layers will reduce the collapse of the security reserves, and the number of layers has a great impact on the CMR.

    • Failure Modes of Single-layer Lamellar Spherical Reticulated Shellsunder Cooperative Work with Lower SupportingStructures and Severe Earthquakes

      2020, 42(2):299-303,310. DOI: 10.3969/j.issn.1000-0844.2020.02.299

      Abstract (562) HTML (0) PDF 6.03 M (913) Comment (0) Favorites

      Abstract:This paper proposes three structural failure models of single-layer lamellar spherical reticulated shells under 90 working conditions based on ABAQUS finite element analysis; these models include the failure modes of weakly supported structures, strongly supported structures, and moderately supported structures. The ultimate acceleration of the structure markedly differs under different failure modes, and the ultimate failure loads of the structure under the failure modes of weak and strong support are low, while that under the failure mode of moderate support is relatively high. The failure load of the structure presents an increasing trend in the interval from weak or strong support to medium support. When the stiffness of the upper and lower structures is matched, the ultimate bearing capacity of the structure is relatively high. The stiffness of the lower supporting columns is one of the main factors affecting the failure modes and ultimate loads of a structure. Increases in supporting stiffness cause the ultimate load of the structure to first increase and then decrease. As the equivalent load of the roof increases, the ultimate bearing capacity of the structure decreased and shows greater potential to be damaged in an earthquake.

    • A Simplified Model of, and Critical Angles for Curved Bridgesunder Multi-dimensional Earthquake Excitation

      2020, 42(2):304-310. DOI: 10.3969/j.issn.1000-0844.2020.02.304

      Abstract (587) HTML (0) PDF 4.78 M (880) Comment (0) Favorites

      Abstract:The internal force or stress of a certain point or section of a curved girder bridge can reach its maximum value only when earthquake motion is sourced from a certain direction. Therefore, it is necessary to input ground motions in multiple possible directions so that the critical angle can be determined. Based on the mechanical characteristics of isolated curved girder bridges, this study simplified bridge superstructure and piers into an accumulated mass model with two horizontal degrees of freedom and one torsional degree of freedom around the mass center axis. Thus, a simplified analytical model with two particles and six degrees of freedom was established. Dynamic characteristics and ground motion behavior of the curved girder bridge were studied by solving the dynamical equation of the structure. The experimental sample showed that the calculated results of the two-particle model were basically consistent with those of the traditional finite element model. The method was simple and the influence of various sensitivity factors was considered. With the help of programming, a more regular design method is put forward. Based on the model, the critical angle of curved girder bridges under multi-dimensional earthquake action was investigated using MATLAB programming. For isolation curved girder bridges with different parameters, the critical angle could be determined only by running the program once after changing relevant parameters. The model provided a reference for determining the critical angle of seismic waves by a finite element method, and greatly reduced the workload of trial calculations of multi-directional input.

    • Parameter Sensitivity Analysis of Continuous Rigid-frame Bridgesin High Seismic Intensity Regions under Seismic Action

      2020, 42(2):311-317. DOI: 10.3969/j.issn.1000-0844.2020.02.311

      Abstract (635) HTML (0) PDF 5.50 M (2243) Comment (0) Favorites

      Abstract:The seismic response of long-span, continuous rigid-frame bridges is greatly affected by a parameter change. To further study the influence of various parameters of rigid-frame bridges on the internal force of the bridge under the action of an earthquake, the orthogonal numerical test method was adopted with a continuous rigid-frame bridge as an example. The transverse bending moment at the middle span of the main beam, the longitudinal bending moment at the pier top and bottom, and the transverse bending moment at the pier bottom were taken as the evaluation indices. The influence law of structural parameters (side span-to-central span ratio, power of beam bottom, pier height ratio) on the internal force of the bridge under seismic action, and the parameter sensitivity were analyzed. Results indicated that the pier height ratio had a great influence on the mid-span transverse bending moment. Additionally, it was observed that with the rise in pier height ratio, the maximum bending moment value increased by 28%. The side span-to-central span ratio had a large influence on both the longitudinal bending moment at the pier top and bottom and the transverse bending moment at the pier bottom, and with the increase of side span-to-central span ratio, the maximum value of the bending moment increased by 51%, 55%, and 52%, respectively. Bridge design in high-intensity areas should pay close attention to the choice of side span-to-central span ratio and pier height ratio.

    • Seismic Response Analysis of the Emergency Bridgeof a Nuclear Power Plant

      2020, 42(2):318-325. DOI: 10.3969/j.issn.1000-0844.2020.02.318

      Abstract (584) HTML (0) PDF 9.62 M (1004) Comment (0) Favorites

      Abstract:In this paper, an emergency bridge was first built in a nuclear power plant to meet constructional, operational, and emergency needs, as seismic safety is very important. In this paper, the finite element dynamic time-history analysis method was introduced to construct a three-dimensional integral refined model considering bridge-pile-soil interaction. Maximum acceleration of typical subgrade section and T beam, and distribution of the maximum moment at the bottom of a bridge pier column were calculated under SL-1 and SL-2 earthquake actions. Calculated results showed that this method can directly address the nonlinear problem of soil and conveniently incorporate the radiation damping effect of the foundation. Contact between T beam and cover beam can be precisely simulated. Moreover, the independent development high-performance software platform GEODYNA, with its high efficiency, was used for 3D calculation. This method can provide some reference in the seismic design of bridges in nuclear power plants.

    • Seismic Response of High-rise Steel StructureBuildings with Transverse Bracing

      2020, 42(2):326-331,367. DOI: 10.3969/j.issn.1000-0844.2020.02.326

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      Abstract:To test the seismic performance of high-rise steel structures, we used a high-rise steel-frame office building as our research object. Using the finite element model, we analyzed the seismic response of its transverse bracing. As the input wave, we used the El-Centro wave with a peak acceleration of 200 cm/s2. To analyze the seismic simulation response of the building with different slab thicknesses, we used the transient dynamic method and obtained the displacement time-history curves at the top floor of the building. Using SAP200 software, we analyzed the response spectra of the building before and after setting the transverse bracing, then recorded the vertical and horizontal displacements and the story drift ratio. The results are as follows: (1) The displacement of the high-rise steel structure building under earthquake did not increase with increased slab thickness, and displacement fluctuation was obvious at slab thicknesses of 100 mm and 170 mm. (2) After setting the transverse bracing, the horizontal stiffness of the building was obviously improved, and the maximum story drift ratio varied greatly, but was always less than 1/250, which meets the requirements of the relevant building code.

    • A Simplified Analysis Model for Evaluating the Seismic Performance ofHigh-Rise High-Strength Steel Composite Eccentrically Braced Frames

      2020, 42(2):332-336. DOI: 10.3969/j.issn.1000-0844.2020.02.332

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      Abstract:A high-strength steel composite eccentrically braced frame (HSS-EBF) is a new type of seismic structure system. A simplified HSS-EBF analysis model was established using the ABAQUS software to analyze its seismic performance. The overall model of a 10-story HSS-EBF example was developed after the validity of the simplified analysis model was verified. Subsequently, the hysteretic behavior of this example was analyzed by simultaneously applying vertical load and horizontal inverted triangular cyclic load. The results denoted that the simplified HSS-EBF analysis model can accurately simulate the ductility and lateral stiffness as well as dffectively predict the deformation and nonlinear performance of the HSS-EBF structure.

    • Experimental Study on Flexural Capacity of ConcreteShear Walls under Strong Earthquake

      2020, 42(2):337-344. DOI: 10.3969/j.issn.1000-0844.2020.02.337

      Abstract (499) HTML (0) PDF 10.41 M (804) Comment (0) Favorites

      Abstract:Experimental work on the flexural capacity of concrete shear walls under a strong earthquake was conducted to improve the measurement accuracy of the flexural capacity of concrete shear walls. The study samples were chosen as one concrete shear wall contrast specimen and three test specimens, and the vertical load and horizontal load were applied to simulate the strong seismic intensity. After completing the preparatory work of the test, the separated finite element model was established. In the finite element model, the plastic damage analysis of concrete was completed by calculating the elastic-plastic stiffness of concrete under compression and tension. Based on this, it calculates the flexural capacity of the concrete shear wall. The finite element model was applied to the three test specimens to carry out the simulation test. The simulation results showed that the load-displacement curves of the three specimens are similar to the actual displacement values after a serious earthquake, and the error between the test result and the actual value is less than 2%, which means that the experimental testing method has some viability and shows that the numerical simulation results are accurate.

    • Critical Load for Buckling Failure of Curtain WallStructures after Deformation of the Building

      2020, 42(2):345-351. DOI: 10.3969/j.issn.1000-0844.2020.02.345

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      Abstract:To solve the problems of curtain wall structures in the traditional deformation of building settlements, research on the critical load of buckling stability of the curtain wall structure in the deformation of building settlements was proposed. The glass curtain wall of the structure was selected as a research object; a finite element model of the glass panel was established to simulate the critical load of the buckling stability of the curtain wall structure. The vertical springs were placed in different nodes at the bottom of the building, and the vertical force of the building's deformation was simulated by adjusting the spring stiffness. On this basis, the potential deformation energy, the potential energy of external force and the potential energy of elastic restriction of the glass rib were calculated by the energy method. Then, the critical load of the buckling stability of the curtain wall structure in the deformation of the building's settlement was calculated according to the principle of the potential value of the standing energy. Different glass rib parameters were established and the single variable factor for the experiment was selected. The experimental results showed that the results of the calculation of the proposed method are accurate and the calculation time of the critical load of the proposed method is less than that of other methods.

    • Collapse Analysis of Transmission Towers under Multi-dimensionalSeismic Excitation Considering Hysteretic Behavior of Components

      2020, 42(2):352-359. DOI: 10.3969/j.issn.1000-0844.2020.02.352

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      Abstract:Based on a novel, nonlinear material constitutive model of angle steel, the collapse mechanism of transmission towers subjected to multi-dimensional seismic excitation was simulated in this paper. Buckling capacities of angle steels with different slenderness ratios were investigated by the RIKS algorithm in ABAQUS, and the finite element analysis results were verified by bearing capacity tests. Based on the hysteretic property test results, a new nonlinear material constitutive model of angle steel was developed and verified using Fortran programming language. A three-dimensional finite element model of the transmission tower was then established, and collapse of the transmission tower under multi-dimensional seismic excitation was simulated. Ultimate bearing capacity, buckling of members, and collapse locations of the transmission tower were investigated by dynamic explicit analysis. Research results can provide a theoretical guidance for the seismic design of transmission towers under multi-dimensional seismic excitation.

    • >地震科学与监测技术
    • Thermal Infrared Anomalies before Milin MS6.9 Earthquake in 2017

      2020, 42(2):360-367. DOI: 10.3969/j.issn.1000-0844.2020.02.360

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      Abstract:In this study, we used the thermal infrared brightness data from China geostationary meteorological satellite to investigate the thermal anomalies before the Milin MS6.9 earthquake in Tibet, 2017. We used the methods of wavelet transformation and power spectrum estimation and found that the anomalies appeared four months before the Milin earthquake. The evolution direction of anomalies was very similar to the faults orientation in the study area. The anomaly area reached the maximum on August 10 and disappeared on September 20. We also analyzed the data for the same period and same frequency in 2016, and the results showed that no significant anomalies occurred around the epicenter. Time-series curves indicate that the peak value of the relative power spectrum appeared on August 12, 98 days before the Milin earthquake. The peak value was almost 20 times the average value. From July 4 to September 7, the relative power spectrum deviated from the background value and standard deviation for about 65 days. The thermal infrared anomalies of strong earthquakes in Tibet are mainly distributed in south-central Tibet, which is consistent with the distribution of geothermal resources, thus providing abundant experiences for predicting earthquakes in Tibet.

    • Distortion Anomalies in Geomagnetic Diurnal Variationbefore the Jinghe M5.4 Earthquake in 2018

      2020, 42(2):368-375. DOI: 10.3969/j.issn.1000-0844.2020.02.368

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      Abstract:The comprehensive characteristics of geomagnetic anomalies before the Jinghe M5.4 earthquake on October 16, 2018 were obtained and analyzed using a series of geomagnetic methods such as the geomagnetic daily value spatial correlation, geomagnetic load-unload response ratio, spatial correlation of daily variation of the geomagnetic vertical component, and geomagnetic low-point displacement. These methods showed that there were middle and short-term anomalies before the earthquake. Additionally, the results showed the following aspects. (1) Before the earthquake, multiple anomalies existed, which enhanced the credibility of the methods. (2) The anomalies considerably increased closer to when the earthquake erupted demonstrating that seismogenic probability increased in this area. (3) Compared with a single method, a comprehensive analysis method to identify earthquake locations, can reduce the time scale of prediction. (4) Anomalies in the spatial correlation of the daily variation of the geomagnetic vertical component mainly appeared in the northern Tianshan area before the earthquake. The comprehensive anomalies observed in the Jinghe earthquake illustrated that geomagnetic analysis methods had a certain forecast effectiveness in short-term earthquake prediction.

    • Geological and Geomorphological Evidence of Late Quaternary Activity alongthe Southeastern Segment of the Lintan—Tanchang Major Fault, China

      2020, 42(2):376-383. DOI: 10.3969/j.issn.1000-0844.2020.02.376

      Abstract (874) HTML (0) PDF 28.81 M (894) Comment (0) Favorites

      Abstract:The Lintan—Tanchang fault zone is located between the east Kunlun fault and the northern margin of the West Qinling fault. As an important fault in the process of tectonic transformation and deformation transfer in the southeastern Gansu, China, its geometric distribution, new activity, and movement characteristics play a crucial role in earthquake preparation. Much investigation and research on the Lintan—Tanchang fault has been conducted, especially since the occurrence of the Minxian—Zhangxian MS6.6 earthquake. It has been thought that the activities of each segment of the fault had significant differences. With the exception of the southeast section of the main fault, the remaining secondary faults have been active since the late Quaternary. In this paper, we discovered geological and geomorphological evidence of late Quaternary activities along the southeast section of the Lintan—Tanchang main fault. As an important supplement of the structural features and activities of this fault, this discovery can help perfect the geometric images and motion characteristics of the regional structure, and it is vital in understanding the regional tectonic activities, tectonic transformation, and deformation transfer.

    • Seismogenic Structure of 2018 Xietongmen, Tibet MW5.6Earthquake Inferred from InSAR Data

      2020, 42(2):384-390. DOI: 10.3969/j.issn.1000-0844.2020.02.384

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      Abstract:On December 24, 2018, a MW5.6 earthquake occurred in Xietongmen County, Shigatse City, Tibet. This study utilizes Sentinel-1A satellite SAR data and D-InSAR technology to obtain an image of the co-seismic deformation field in the LOS direction and then inverses the geometric parameters and co-seismic slip distribution of the seismological fault of the event. The results show that the fault associated with the MW5.6 earthquake lies in a near NS-direction, has a dip angle of 35°, and a rupture length of 12 km. The co-seismic slip is mainly concentrated in a range of 4-11 km, the maximum slip is 0.18 m, and the moment magnitude is MW5.6. In addition, it is determined that the seismogenic fault of the Xietongmen earthquake in 2018 is a new blind fault belonging to the Xietongmen—Shenzha extensional fault system.

    • Correlation between Component Borehole Strain Observation at LinxiaSeismic Station and the Minxian-Zhangxian M6.6 Earthquake

      2020, 42(2):391-395. DOI: 10.3969/j.issn.1000-0844.2020.02.391

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      Abstract:The reliability of component borehole strain observation data of Linxia station from 2008 to 2018 was analyzed. The means value of the annual correlation coefficient between S1+S3 and S2+S4 was found to be more than 0.98. The calculated results of principal stress and direction showed that there was an apparent anomalous change in the principal direction before the Minxian M6.6 earthquake in 2013; after removing the trend drift, the change characteristics of the principal stress first decrease and then increased, and the Minxian M6.6 earthquake occurred in the change of trend.

    • Noise Analysis of Coastal Broadband Tiltmeter Based on STFT Method

      2020, 42(2):396-402. DOI: 10.3969/j.issn.1000-0844.2020.02.396

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      Abstract:Based on the observation data of broadband tiltmeter at coastal seismic stations (Putian and Xiamen stations), this paper analyzes the noise of broadband tiltmeter using the short-time Fourier transform (STFT) method of analysis. Several noise patterns are summarized and the respective physical meaning is analyzed. The broadband tiltmeter noise mainly involves seismic co-seismic wave, typhoon interference, bad line contact, interference signal from the motherboard, etc. The results of the research can be used to track and analyze broadband tiltmeter of observation data, as well as to determine the types of broadband tiltmeter fault.

    • Application of Deformation Rate Accumulation Methodto the Fixed-point Leveling Observation in Shanxi

      2020, 42(2):403-409. DOI: 10.3969/j.issn.1000-0844.2020.02.403

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      Abstract:The method of accumulation deformation rate was used to calculate data from four fixed-point observation sites in Shanxi Province, and the relationship between the measurement results and moderate and strong earthquakes in this area and adjacent areas were analyzed, and some continuous abnormal outliers were identified before the earthquake. The anomaly information extraction was more intuitive and prominent, showing a strong earthquake-reflective effect. This approach has certain reference significance for the anomaly identification of cross-fault data in Shanxi.

    • Detection Method for Seismic Ionospheric DisturbanceAnomaly Data Based on DBSCAN

      2020, 42(2):410-415. DOI: 10.3969/j.issn.1000-0844.2020.02.410

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      Abstract:To improve the accuracy of the analysis of ionospheric disturbance data and eliminate anomalous data, this study proposes a detection method for seismic ionospheric disturbance anomaly data based on DBSCAN. According to the characteristics of wireless sensor network data, the Euclidean distance is set as the index, and different ionospheric disturbance data are compared and clustered. The similarities of the seismic ionospheric disturbance data are then calculated. The DBSCAN method is used to extract relevant environmental feature sets, through which the seismic ionospheric disturbance anomaly data can be detected. The run time, false positive rate, false negative rate, and detection rate of the proposed method are compared with those of a traditional method. Experimental results show that the proposed method requires minimal time, significantly reduces false positive and false negative rates, and improves detection rates.

    • Improvement of Integration and Sharing Performanceof Seismic Data in Intelligent Network

      2020, 42(2):416-421. DOI: 10.3969/j.issn.1000-0844.2020.02.416

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      Abstract:Seismic data integration and sharing play a significant role in seismic monitoring and analysis. The conventional digital library-based seismic data integration and sharing method have the problems of low integration and poor sharing rates, so a new seismic data integration and sharing method are studied. The method is divided into two stages. First, seismic data is collected using data warehouse technology, including data extraction, cleaning, reduction, loading, etc; then a sharing platform is set up to complete the data transparent access, and the data sharing is realized. The results show that the proposed method’s degree of integration and sharing rate can reach 95.68% and 87.34%, respectively, providing an efficient data query mechanism for seismic monitoring and prevention of telemetry.

    • Reliability Analysis of a Geoelectric Field Observation:A Case Study of Guazhou Station

      2020, 42(2):422-430. DOI: 10.3969/j.issn.1000-0844.2020.02.422

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      Abstract:In this study, observation data of two different instruments at Guazhou station were processed through time-frequency analysis methods, and the reliability of the geoelectric field observation data of Guazhou station for many years was evaluated. The following conclusions are drawn: (1) The correlation coefficient of the long and short dipoles in the same direction is basically above 0.9, and the difference value is below 1 mV/km. (2) The comparison and analysis results of the two instruments in February 2015 and February 2019 show that the maximum diurnal variation ratio of the long dipole to the short dipole in different periods is close to 1. This finding indicates that the device system, observation environment, and electrical structure of the observation site have been in a stable state for a long time. (3) The frequency spectra of FFT in the north-south and east-west directions from 2014 to 2016 show dominant periods of 8, 12, and 24 h. Generally, the observation data recorded by the two instruments at Guazhou station are basically reliable and can meet the requirements of earthquake prediction and electromagnetic field monitoring.

    • Anomaly Characteristics of Geomagnetic DiurnalVariations in Sichuan and Adjacent Areas

      2020, 42(2):431-437. DOI: 10.3969/j.issn.1000-0844.2020.02.431

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      Abstract:The geomagnetic vertical component data of 31 geomagnetic stations in Sichuan Province and its adjacent areas since 2015 were analyzed with the geomagnetic load-unload response ratio method. Results show six groups of high anomaly values of the geomagnetic load-unload response ratio. Five of these groups correspond to earthquakes above M5.0. The anomalies usually appear within 6 months before an earthquake, and the epicenter is located near the threshold line of the abnormal area. The high anomaly values of the geomagnetic load-unload response ratio are related to the changes in the induced magnetic field resulting from the electrical conductivity change in the seismogenic zone.

    • Fault Determination and Mechanism Analysisfor Electrodes in the Geoelectric Field

      2020, 42(2):438-446. DOI: 10.3969/j.issn.1000-0844.2020.02.438

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      Abstract:The variations of the data on the electrode faults in the geoelectric field in Hebei province in recent years are analyzed and summarized. The data variations are considered stable without interference, and a "peak valley" shape can be seen in the images recorded by several stations. Moreover, the correlation coefficient and difference are satisfactory. The synchronous interference of the data on the electrode faults in the geoelectric field in two channels mainly indicates the following: (1) the correlation coefficient of the data in the two channels decreases, and the difference becomes large; (2) the image shows synchronous step, jump, and long-trend changes. The position of electrode failure can be preliminarily determined according to the synchronicity of the data variation. Meanwhile, nonelectrode faults also need to be eliminated. The observation environment, instrument, external circuit, circuit connector, and wiring board are first checked, and the electrode failure is determined with a contrast test. The Butler-Volmer equation and Nernst equation are used to analyze and explain the data variation caused by the electrode failure. The results of this study can serve as a reference for stations in judging electrode faults promptly.

    • Quantitative Analysis of the Disturbance to Earth Resistivity Caused by a Metal Greenhouse at Zhoukou Station

      2020, 42(2):447-452. DOI: 10.3969/j.issn.1000-0844.2020.02.447

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      Abstract:The earth resistivity observations in Zhoukou station showed an anomaly in 2015 due to disturbance sources near the station. To correctly evaluate this anomaly, this study established a 3D numerical model on the basis of electrical sounding results. The influences of disturbance sources near the station on earth resistivity observations were quantitatively assessed by using the finite element method. Calculation results suggested that the disturbance from a metal greenhouse was the main influencing factor of the anomaly.

    • Reliability of Geoelectric Activity Indexes in Jiangsu andAnhui Provinces Based on GEI Method

      2020, 42(2):453-459. DOI: 10.3969/j.issn.1000-0844.2020.02.453

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      Abstract:In this study, in the first quarter of 2018, the single-station geoelectric index D and multi-station average geoelectric index Ds were determined using the geoelectric index (GEI) method based on observation data of 6 stations in Jiangsu and Anhui Provinces. Comparing the index D and Ds with single-station geomagnetic index K and average geomagnetic index K of the 6 stations, it was found that: 86.48% of D indexes are correspondingly the same with K indexes or have only a difference of 1, and 89.44% of Ds indexes are correspondingly the same with K indexes or have only a difference of 1. The high consistency between two types of indexes showed that: (1) the geoelectric index calculated by this method is reliable; (2) the electromagnetic activity level can be quantitatively identified by geoelectric indexes D and Ds. Only a few of the D and Ds indexes have a slight difference from the K and K indexes, but the problem can be well solved if the measurement accuracy of geoelectric field is improved or the measurement data from more stations are used in the calculation; (3) In the future, the mutual compensation and reference between the geoelectric and geomagnetic indexes will more accurately identify the earth’s electromagnetic activity level in mainland China. This will have a wide prospect of application in the related field of earth science and technology.

    • Accurate Analysis of the Effect of Rainfall on Water Level of theThree Gorges Well Network Based on Surface Soil Infiltration

      2020, 42(2):460-467,528. DOI: 10.3969/j.issn.1000-0844.2020.02.460

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      Abstract:To study the influence of rainfall on the well water level of the Three Gorges well network, based on the surface rock and soil permeability, the vertical permeability test method of the surface rock and soil in the area where the wells existed was used to measure the vertical permeability of the surface rock and soil. A mathematical model was developed for the rainfall infiltration supply analysis. On the basis of this model, the effect of rainfall on the daily, monthly, and annual dynamics of well water level was accurately analyzed and checked through the comparative observation data of the water level and meteorology of eight wells in the three Gorges well network. The results show that the influence characteristics are quite complex. The influence characteristics of the same rainfall cycle on different wells are different. On one hand, they may be related to the different hydrogeological conditions of each well, while on the other hand, they may also be related to the difference in the cycle of rainfall at each well point.

    • >岩石土力学抗震
    • Comparative Analysis of Vibration Measurement BetweenQingdao Metro Line 3 on Rock Foundation andShanghai Metro Line 10 on Soft Foundation

      2020, 42(2):468-474. DOI: 10.3969/j.issn.1000-0844.2020.02.468

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      Abstract:The environmental vibration caused by subway running can affect human health if it exceeds a certain value. Evaluating the exact vibrational response caused by the subway is of great importance. Therefore, an imported vibration meter is used to measure the vibration of Qingdao Metro Line 3 and Shanghai Metro Line 10, respectively. By processing the data, the time-history curves of vibration acceleration are obtained, and the Fourier transform also obtains the corresponding spectrum curves. The spectrum curves are then transformed into the frequency range of the one-third octave spectrum. Finally, the average value of frequency vibration levels is worked out. The differences between Qingdao Metro Line 3 and Shanghai Metro Line 3 in terms of vibration acceleration time-history curves, vibration acceleration spectra, one-third octave spectra, and frequency vibration rates are also discussed. The findings show that the Qingdao Metro’s vibration response is greater than that of Shanghai Metro; the frequency vibration level of Qingdao Metro has surpassed China’s environmental vibration standard, whereas Shanghai Metro’s frequency vibration level is equal to environmental vibration standard.

    • Influence of Initial Normal Stress of Slip on the Stabilityof Common Three-dimensional Slopes

      2020, 42(2):475-480. DOI: 10.3969/j.issn.1000-0844.2020.02.475

      Abstract (473) HTML (0) PDF 1.68 M (571) Comment (0) Favorites

      Abstract:The influence of the distribution of the initial normal stress on the stability of slope was investigated using the explicit solution of slope safety factor based on modification of normal stress distribution over the slip surface. The initial normal stress distribution over the slip surface was assumed and then modified by a correction function with undetermined parameters so the slip mass can satisfy the equilibrium conditions of force and moment in all directions. An equation satisfying all the equilibrium conditions was derived, and the safety factor was calculated. Slope stability was also evaluated. Computation results show the minimal influence of different distributions of initial normal stress on the 3D symmetrical slope. The maximum difference in the safety factor is below 5%. For the common slope, the influence is relatively large and the difference in the safety factor is 6.2%. The maximum difference compared with the other methods is 28.7%. Therefore, verifying the rationality of normal stress distribution over the sliding surface is necessary in engineering practice.

    • Neighboring Underground Structure-Soil InteractionCharacteristics under Seismic Action

      2020, 42(2):481-489. DOI: 10.3969/j.issn.1000-0844.2020.02.481

      Abstract (540) HTML (0) PDF 10.38 M (1087) Comment (0) Favorites

      Abstract:In this paper, the seismic performance of a large subway station with a three-story, three-span major structure, and a two-story, three-span additional structure, was analyzed using a dynamic time-history method. The seismic responses of the site soil and the major structure under varying interaction modes and distances between major and additional structures were discussed. Under different working conditions, deformation of the site soil and the major structure, and the internal force and story drift angle of the major structure were analyzed and compared. Results showed that the influence of the neighboring underground structures-soil interaction on the site soil was more significant than that of the individual underground structures-soil interaction. When the distance between the additional structure and major structure was more than twice the structural width, the effect of the additional structure on the deformation of site soil around the major structure could be neglected, and the effect on the deformation and internal force of the major structure was essentially zero. Hence, the influence range of the interaction between neighboring underground structures under an earthquake was basically twice the structural width. The existence of the additional structure adversely affected the major structure under an earthquake. The deformation and internal force of the structure with a single-layer channel connection were smaller than those with double-channel connections.

    • Field Test and Analysis of Vehicle Load and Its Influence on theRetaining Structure of Adjacent Foundation Pits

      2020, 42(2):490-497. DOI: 10.3969/j.issn.1000-0844.2020.02.490

      Abstract (584) HTML (0) PDF 5.38 M (2334) Comment (0) Favorites

      Abstract:Currently, research into vehicle loads’ influence on support structures of foundation pits is still at an initial stage. Through field measurements of vehicle load and vibration acceleration of foundation pits’ retaining structures, as well as dynamic earth pressure of a retaining pile following the action of vehicle load. Empirical formulas for the calculation of vehicle load on adjacent foundation pits were obtained, and the influence of vehicle load and vehicle speed on the vibration characteristics of retaining structures and dynamic earth pressure were analyzed. Results showed that vertical vibration gives priority to the vibration induced by vehicle load at the ground surface. Vehicle load directly influences the amplitude of the vibration acceleration of both the foundation pit retaining structure and the dynamic earth pressure. Vehicle speed also has an effect on the peak acceleration induced by vehicle vibration, and higher speed will lead to larger peak vibration acceleration and dynamic earth pressure. However, the influence of vehicle load will decrease with increasing distance. These results can provide a reference for design and construction of relevant foundation pit projects.

    • A Cloud Model for Rock Burst Prediction Based onthe Back Analysis Weighting Approach

      2020, 42(2):498-504. DOI: 10.3969/j.issn.1000-0844.2020.02.498

      Abstract (467) HTML (0) PDF 1.51 M (660) Comment (0) Favorites

      Abstract:To comprehensively consider the randomness and ambiguity in rock burst prediction practice, a cloud model theory is introduced into the method. However, the index weight value of the existing rock burst prediction cloud model needs to be improved in terms of objectivity and accuracy. Therefore, this paper proposes a rock burst cloud model based on a back analysis weighting approach. First, the specific implementation steps of the model are given, and the optimization objective function is established. Next, the ratio of maximum tangential stress of cavern to the compressive strength of rock, the ratio of compressive strength of rock to the tensile strength, and the elastic energy index were selected as judging indexes. Based on 18 rock burst engineering examples, the back analysis of index weights was carried out using MATLAB software. Finally, the newly-built cloud model was applied to the rock burst prediction of the Jiangbian hydropower station and Maluping mine. Results were compared with the predictive results of the cloud model based on a subjective weighting method to test the feasibility and effectiveness of the proposed model. The research showed that the subjective interference factors in the weighting process of the rock burst cloud model based on back analysis weighting approach were few, thus the accuracy of prediction results was high.

    • Development of Similar Materials and Model Test Analysis ofRock Excavation and Unloading for the SurroundingGrade-V Rock under High Geostress

      2020, 42(2):505-511. DOI: 10.3969/j.issn.1000-0844.2020.02.505

      Abstract (556) HTML (0) PDF 3.84 M (813) Comment (0) Favorites

      Abstract:The model test can quantitatively and qualitatively reflect the variation law of physical parameters based on simplified ontology. Herein, loess and sand are considered to be the aggregates, gypsum and cement are considered to be the cementing material, water is considered to be the regulator, and the orthogonal test method is used to prepare a material similar to the surrounding grade-V soft rock. The physical and mechanical parameters of the material can satisfy the requirements and appropriately simulate the surrounding grade-V soft rock of a tunnel. On this basis, the steel cylinder model test is used to observe differences with respect to the stress-varying slope, self-stabilization time, and strain of the test group under different material ratios. Further, the excavation and unloading effects of the surrounding grade-V rock are explored under a high geostress based on the variation of rock mass at the opening of the model after loading. The test results denote that different proportions of similar materials will cause variation of the physical and mechanical properties and that the elastic modulus exhibits considerable influence; furthermore, the self-stabilization time of the material increases, the stress release becomes considerably thorough, and the overall variation trend decelerates with an increase in vertical pressure.

    • Quick Assessment of the Seismic Stability of LoessSlopes Based on a Logistic Regression Model

      2020, 42(2):512-516. DOI: 10.3969/j.issn.1000-0844.2020.02.512

      Abstract (684) HTML (0) PDF 2.91 M (780) Comment (0) Favorites

      Abstract:Seismic loess landslides are one of the main geological disasters in the Longxi area. A method to quickly evaluate seismic stability of loess slopes is necessary for large-scale site selection and earthquake emergency response in the study region. On the basis of a field survey and remote sensing interpretation, the slope height H, slope angle α, and estimated intensity value I, were obtained. Using the logistic regression analysis method, an empirical formula for quickly evaluating the seismic stability of loess slopes was obtained. Through back-judgment, validations, and application in real cases, it can be concluded that the formula proposed in this study is suitable for quickly evaluating the seismic stability of loess slopes in the Longxi area.

    • Evaluation of Blasting Vibration Effect of Residential Housesaround Quarry and Attenuation Relationship

      2020, 42(2):517-520. DOI: 10.3969/j.issn.1000-0844.2020.02.517

      Abstract (427) HTML (0) PDF 8.61 M (740) Comment (0) Favorites

      Abstract:To avoid the impact of the blasting construction in Fuling quarry on the surrounding residential houses, a total of four test points were set up, and the influence of blasting vibration with different blasting charges and distances on nearby houses was monitored and analyzed. The vibration attenuation relationship and the safe distance of the quarry blasting construction for nearby residential houses were obtained. When the distance from the protected objects is 200 m, the blasting charge is 96 kg, and the vibration velocity is 0.45 cm/s, the upper limit value of the allowable vibration of the adobe house and rubble house is reached.

    • Relationship Between Microscopic Parameters and Shear Strength C, φ of Loess in Lanzhou New District

      2020, 42(2):521-528. DOI: 10.3969/j.issn.1000-0844.2020.02.521

      Abstract (499) HTML (0) PDF 12.94 M (1029) Comment (0) Favorites

      Abstract:In this study, we conducted a direct shear test of undisturbed loess (typical low clay silt) in the Lanzhou new district, used high-power electron microscopy, and conducted an energy spectrum test to obtain the cohesion C, internal friction angle φ, mineral element ratio, and micro structural parameters of the loess. We then analyzed the correlation among the microcosmic parameters, the mineral element ratio, and the shear strength (C, φ) of the soil samples by a single-factor and multiple regression fitting method. The results indicate that the φ value has a linear correlation with the mean angle value, and the correlation coefficient of the fitting formula is 0.82. The cohesion C value is linearly correlated with the kurtosis and skewness of the long axis, Fe/Si, Al/Si, and K/Al, and the maximum correlation coefficient after fitting is 0.99. The fitting formula for the microcosmic parameters and shear strength provide a new research approach for predicting the shear strength of soil samples.

    • Dynamic Response of Loess Slopes Based onthe Shake Table Test

      2020, 42(2):529-535. DOI: 10.3969/j.issn.1000-0844.2020.02.529

      Abstract (530) HTML (0) PDF 9.52 M (811) Comment (0) Favorites

      Abstract:In the loess region, the geotechnical disasters caused by the earthquake are serious. Taking a loess slope in the new Lanzhou area as a prototype, we conducted a large-scale oscillating table model test to study the dynamic response law and the loess slope failure mechanism under the earthquake load. The results showed that the acceleration amplification effect on the loess slope surface is obvious and reaches its maximum value on the slope shoulder. Meanwhile, the amplification effect increases with increasing seismic intensity, when the intensity reaches 600 gal, the maximum amplification coefficient on the slope shoulder is 2.06. The result also showed that ground pressure on the slope surface is less than the pressure on the slope body at the same elevation. The maximum value appeared on the slope of the free face and the value varies between 0.7-0.75 kPa. As the seismic intensity increases, the slope's superficial fissure gradually changes from a small short to a deep fissure, especially near the shoulder of the slope. In the test, the maximum settlement is about 10 cm and the maximum horizontal displacement of the slope shoulder is about 5-8 cm. The final failure mode of the model slope is traction break-slip. The research results may provide some reference for studying the stability of the loess slope under earthquake loads.

    • >震灾防御及综合
    • Setback Distance for Seismic Fortification and Avoidanceof Structures in Ground Fissure Sites

      2020, 42(2):536-545. DOI: 10.3969/j.issn.1000-0844.2020.02.536

      Abstract (527) HTML (0) PDF 5.31 M (3164) Comment (0) Favorites

      Abstract:Based on geological exploration data obtained along the Xi'an Metro Line 2, in this study, we used ABAQUS finite element software to establish an interaction model for a ground fissure site and structure. In the experiment, the structure was placed at different distances from the ground fissure followed by the application of a seismic wave equivalent to that of the El Centro earthquake. We then compared the changes in the story drift ratio and shear force of the frame columns at the different locations to study the working characteristics of the near-ground fissure structure under earthquake. We determined the dynamic response law of the structure for different setback distances, which were then compared with the variation law of peak acceleration of the ground surface. The results showed that the magnification of the story drift ratio was 30%-41% for a hanging wall structure and 18%-22% for a footwall structure. With increases in the setback distance, the peak acceleration gradually decreased, as did the degree of structural damage. The peak ground acceleration showed a gentle linear decline, and the magnification of the maximum story drift ratio decreased from 41% to 21%. Variation in the peak ground acceleration does not fully reflect the dynamic response law of a near-ground fissure structure. The dynamic time history response law of a structure located at a ground fissure site obviously differs from that at a regular site. The maximum horizontal seismic influence coefficient must be adjusted when a structure located at a ground fissure site is designed for seismic resistance.

    • Design of a Real-time Transmission System for Big DataCongestion during Earthquake Based on Python

      2020, 42(2):546-551. DOI: 10.3969/j.issn.1000-0844.2020.02.546

      Abstract (590) HTML (0) PDF 1.78 M (674) Comment (0) Favorites

      Abstract:Because of the problems of high time delay, poor security, and transmission congestion in the seismic data transmission system, a Python-based real-time data transmission system is proposed in this paper. The system hardware consists mainly of modules for video transcoding, an interactive interface for Python, a module for data transmission, and a module for system maintenance. The video transcoding can be is possible by Un-encapsulation, decoding, video data storage, coding, encapsulation, etc. Using the Python interactive interface, the interaction between the measurement points and seismic data monitoring center is realized. CDMA transmission mode is combined as a wireless transmission module with VPDN networking mode. The system software is split into two data transmission modes: receiving and sending packets, and the system design is mainly completed by receiving the package. The experimental results show that the system has high response speed, low delay, and superior security, which solves the problem of seismic data congestion.

    • An On-line Emergency Assessment Method for SeismicRisk Level of Remote Sensing Information

      2020, 42(2):552-557,578. DOI: 10.3969/j.issn.1000-0844.2020.02.552

      Abstract (480) HTML (0) PDF 2.94 M (545) Comment (0) Favorites

      Abstract:When GIS technology is used to evaluate the seismic hazard level, because of the poor rationality of its terrain control points, the accuracy of the collected remote sensing images is low, and the seismic rating is not sufficiently exact. A new electronic emergency assessment method for remote sensing information hazard levels of earthquake disasters is proposed in this paper. The method of geometric image correction is used to segment the image of the remote sensing, and the surface control points are chosen based on the cutting result. The useful information on remote sensing is extracted, and evaluation indexes for remote sensing interpretation are established. The information of each evaluation unit is ranked and divided, then the online emergency assessment of remote sensing information hazard level is completed. The effectiveness of the proposed method and the GIS seismic hazard rating method were compared in a simulation experiment. The experimental results show that the proposed method will increase the selection rationality of control points for the disaster terrain, make the acquired remote sensing images clearer and the results of the disaster rating more precise.

    • Research and Monitoring of Carbon Emission inCivil Building Reconstruction after Earthquake

      2020, 42(2):558-567. DOI: 10.3969/j.issn.1000-0844.2020.02.558

      Abstract (480) HTML (0) PDF 4.41 M (757) Comment (0) Favorites

      Abstract:when post-earthquake reconstruction carbon emission is high it would have a significant environmental impact. Therefore, it is necessary to propose a monitoring method of carbon emission for civil building reconstruction after the earthquake. To solve the problems of inaccurate monitoring results and low monitoring efficiency in the existing monitoring methods of carbon emission in civil building reconstruction after the earthquake, a new approach was proposed in this work. First, the carbon emission basis was elaborated in detail, and the research was carried out in compliance with the international carbon emission standard. Second, the emission coefficient method was used to complete the data collection of building carbon emissions. Based on the boundary conditions of carbon emissions in the building use stage, the boundary conditions for carbon emissions were determined. Finally, the carbon emission of reconstructed civil buildings after the earthquake was calculated, and the carbon emissions monitoring was done in real-time. The experimental results showed that the proposed real-time monitoring method can effectively monitor the carbon emissions of post-earthquake reconstructed buildings, and has a high monitoring efficiency.

    • Extraction of Building Seismic Damage Information from PolarimetricSAR Images Based on Variogram Texture Features

      2020, 42(2):568-578. DOI: 10.3969/j.issn.1000-0844.2020.02.568

      Abstract (652) HTML (0) PDF 10.21 M (827) Comment (0) Favorites

      Abstract:The rapid assessment of the construction of seismic disaster information has a guiding meaning for earthquake emergency rescue work, and the polarimetric synthetic aperture radar (SAR) has the characteristics of all climatic conditions and of all times. Therefore, the extraction of seismic disaster information from polarimetric SAR images gradually became an access point for research. Although the polarimetric SAR has abundant polarimetric information, the texture information cannot be overlooked. In the image, the texture distribution of the intact artificial construction is regular and that of the collapsed construction area is disorderly. Therefore, the combination of texture information can also extract construction information well. In this article, the 2010 fully polarimetric SAR data in the Yushu area were taken as the object of research. First, the construction area and non-building information, such as the road and hydraulic system, were extracted from the SAR images. On this basis, the variation calculation was performed in the area of collapsed construction and intact building in component T11 of the coherent dispersion matrix. After determining the variation interval a according to the variation curve, the variogram texture information was obtained. Finally, the FCM algorithm was used to extract the area of the intact building and the collapsed building collected from the texture variation information, respectively. The extraction accuracy of intact buildings, destroyed buildings and water systems on the roads is 80.18%, 84.54% and 77.58%, respectively, which are verified by the corresponding sample pixels of the optical remote sensing images after the earthquake.

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