• Volume 43,Issue 6,2021 Table of Contents
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    • >Earthquake Research
    • Three-dimensional velocity structure and seismic distribution characteristics in the juncture of Shanxi, Hebei, and Henan Provinces

      2021, 43(6):1251-1262,1279. DOI: 10.3969/j.issn.1000-0844.2021.06.1251

      Abstract (300) HTML (0) PDF 34.87 M (740) Comment (0) Favorites

      Abstract:We applied the double difference tomography method to relocate seismic events and invert crustal velocity structure of the juncture of Shanxi, Hebei, and Henan Provinces using seismic data from October 2008 to June 2018. After relocation, the spatial distribution of seismic events is improved greatly, and the velocity structure at shallow depth coincides well with topography and sedimentary thickness. The control faults and the events of the study area are mostly distributed along the high-low velocity gradient belt of the Taihang mountain uplift area. We analyzed the tomography results and obtained the characteristics of P- and S-wave velocity anomalies among different tectonic units or the same unit but for various depths. Also, we studied the relationship between the velocity anomalies and the distribution of medium-small earthquakes and historical strong events. Combined with the active seismogenic structures and the deep seismogenic environment of historical strong earthquakes and the medium and small earthquakes in the study area, a scientific basis for the determination of future strong earthquake risk areas can be provided.

    • Statistical relationship between the radon anomaly of Diangou spring and seismic activity in Wudu, Gansu based on data mining technology

      2021, 43(6):1263-1268. DOI: 10.3969/j.issn.1000-0844.2021.06.1263

      Abstract (230) HTML (0) PDF 6.33 M (540) Comment (0) Favorites

      Abstract:High-frequency oscillatory anomalies of radon concentration in Diangou spring in Wudu City, Gansu Province often clustered after the Wenchuan earthquake. The radon observation data and seismic catalogue were preprocessed by using the data mining method, then the parameters such as radon anomaly, magnitude, focal depth, and seismic zonation were extracted. On this basis, Bayesian network model was adopted to study the statistical relationship between radon anomaly in Diangou spring and seismic activity in the surrounding area. The results of seismic zonation obtained from the clustering method were basically consistent with those of tectonic division, reflecting the clustering characteristics of seismic activities in different structural units. The results of Bayesian network model showed that the gas radon anomalies were related to the surrounding seismicity, especially the seismic activities in the middle segment of Longmenshan fault and the Qingchuan fault. The research results are helpful to understand the differential characteristics of gas radon response in Diangou spring to surrounding earthquakes, thus having reference significance for the judgment of gas radon anomaly and earthquake prediction in the future. It also provides a new technical idea and method for earthquake precursor anomaly analysis and seismic activity zonation.

    • Relationship between geophysical anomalies in the southeastern Gansu and the Xiahe MS5.7 earthquake

      2021, 43(6):1269-1279. DOI: 10.3969/j.issn.1000-0844.2021.06.1269

      Abstract (207) HTML (0) PDF 2.38 M (447) Comment (0) Favorites

      Abstract:Combined with the annual geophysical anomalies in 2019, the geophysical fixed-point observation data in the southeastern region of Gansu Province were processed by temporal and spacial scanning, and it was found that eighteen items in nine monitoring stations experienced abnormal changes before the Xiahe MS5.7 earthquake. The reliability of these anomalies were divided from four aspects:the repeatability of anomaly, the coordination of multidisciplinary precursors, the temporal and spatial evolution of anomaly, and the change of anomaly after the earthquake. The reliability value of each anomaly related to the Xiahe earthquake was calculated according to the division results. The calculated results showed that the reliability of each anomaly is more than 50%, indicating that they are basically credible as precursory anomalies of the Xiahe earthquake. Among them, the reliability values of Linxia water level, Linxia borehole strain in the NS direction, and Liangshui water level in Wudu are the highest, up to 80%; the reliability values of Linxia water temperature and Tianshui borehole strain in NS and NW directions are the lowest, less than 60%. The reliability values of anomalies along the Guanggaishan-Dieshan fault are higher than those in the north side of the northern margin fault of the West Qinling, which is related to the concentration of tectonic stress and seismogenic mechanism in the area. The reliability analysis of geophysical anomalies is of great significance to establish an effective earthquake prediction index system.

    • Analysis of the Tangshan M5.1 earthquake on July 12, 2020

      2021, 43(6):1280-1287. DOI: 10.3969/j.issn.1000-0844.2021.06.1280

      Abstract (268) HTML (0) PDF 10.49 M (767) Comment (0) Favorites

      Abstract:This paper analyzed the seismogenic characteristics of the Tangshan M5.1 earthquake on July 12, 2020. The nature, seismogenic structure, and rupture mechanism of the earthquake were preliminarily analyzed, then it was speculated that Tangshan fault may be its seismogenic fault. Before the earthquake, the seismicity anomalies in Tangshan area and North China tectonic region were mainly lack of earthquake and significant calm, indicating that the crustal stress in these areas had accumulated to a certain extent. The M5.1 earthquake belongs to the seismic fluctuation activity in the old seismic area of the Tangshan M7.8 earthquake on July 28, 1976. The sequence of the M5.1 earthquake is not rich; the intensity of the earthquake area is low and the feel range is large.

    • Characteristics of the surface rupture end of the 1679 Sanhe-Pinggu M8 earthquake and its geological significance

      2021, 43(6):1288-1293,1302. DOI: 10.3969/j.issn.1000-0844.2021.06.1288

      Abstract (332) HTML (0) PDF 19.64 M (597) Comment (0) Favorites

      Abstract:The research on the geometric structure and kinematic characteristics of the ends of earthquake surface ruptures is helpful to understand the fracture propagation and termination process scientifically. The Xiadian fault is a crucial seismogenic structure in the North China Plain, where occurred the Sanhe-Pinggu M8 earthquake in 1679. So far, the length of its co-seismic surface fracture and the deformation characteristics of its ending parts remains controversial. Based on the results of previous study and field geological survey, two shallow seismic exploration profiles were arranged at the end of the surface rupture of the 1679 Sanhe-Pinggu M8 earthquake, and the new activity characteristics at the end of the fault were studied. The results showed that the latest activity at the end of the fault occurred in the Holocene. The movement mode is mainly strike slip with a normal slip component, showing obvious characteristics of slip deficit. Combined with the data of co-seismic vertical displacement distribution, it is considered that the surface rupture of the earthquake is only more than 10 km long, which does not match the M8 earthquake, so the seismogenic structure and mechanism of the Sanhe-Pinggu M8 earthquake still need to be further studied.

    • Determination of focal depth using the travel time difference of sPn and Pn waves in multilayer medium

      2021, 43(6):1294-1302. DOI: 10.3969/j.issn.1000-0844.2021.06.1294

      Abstract (159) HTML (0) PDF 5.00 M (433) Comment (0) Favorites

      Abstract:To measure the focal depth by using the travel time difference between sPn and Pn waves and further improve the measurement accuracy, the relationship between the travel time difference of sPn and Pn waves in multilayer medium and the focal depth was deduced, and it was found that the travel time difference is not related to the epicenter distance, but only related to the focal depth and the regional crustal velocity model. The slope of the travel time difference curve remains unchanged with the source in the same layer, while the slope of the curve is different with the source in different layers, showing as a piecewise straight line. The more uneven the crustal velocity structure is in the longitudinal direction, the greater the focal depth error calculated by sPn-Pn travel time difference is, and the greater the slope difference of each segment of the travel time curve is. The single-layer crustal velocity model of sPn and Pn waves with the same propagation path but different wave velocities in the crust was discussed, and it was found that the measured focal depth increases with the increase of wave velocity in single-layer medium. For the same layered structure of crust in the same area, the measured focal depth decreases with the increase of Poisson's ratio. Based on the multi-layer average crustal model of five typical blocks in China provided by previous studies, a quick look-up table for the formula to calculate the focal depth by using the sPn-Pn travel time difference was presented.

    • Design and implementation of an earthquake disaster information acquisition system based on Android platform

      2021, 43(6):1303-1309. DOI: 10.3969/j.issn.1000-0844.2021.06.1303

      Abstract (259) HTML (0) PDF 8.24 M (549) Comment (0) Favorites

      Abstract:Timely and accurate disaster information after the earthquake can provide an important basis for the deployment of emergency rescue force, the decision-making of emergency command, and the assessment of earthquake intensity. This paper analyzed the actual need of quickly collecting on-site disaster information after the earthquake, determined the research and development goal of the earthquake disaster information acquisition system based on Android platform. Then it analyzed the business process of the system and designed the system architecture and system client, middle layer, and data layer. Finally, it described in detail the realization of many functions i.e., disaster information and intensity reporting, query management, statistical analysis, etc. The test results verified the applicable value and disaster collection efficiency of the system.

    • Geochemical characteristics of soil gases Rn and H2in Shanxi reservoir area, Zhejiang Province

      2021, 43(6):1310-1316. DOI: 10.3969/j.issn.1000-0844.2021.06.1310

      Abstract (175) HTML (0) PDF 14.00 M (1196) Comment (0) Favorites

      Abstract:In Shanxi reservoir area of Zhejiang Province,this paper set up 5 survey lines for fault soil gases Rn and H2,then selected 15 sampling points for dissolved water radon.The results showed that the mean value of Rn concentrations in 3 soil gas lines is over 70 Bq/L,the maximum value of soil H2 is 1 377 ppm,and the maximum value of dissolved radon concentration in water samples is 68.3 Bq/L.Based on the analysis of historical seismicity and geological structure of the study area,it is found that the high value distribution areas of soil Rn,H2,and dissolved water radon are closely related to the spatial location of F11-3 branch of the Shuangxi-Jiaoxiyang fault,which is the seismogenic fault of small earthquakes in the study area.In addition,we also found that the occurrence time,the frequency,and the intensity of historical earthquake swarm are important factors affecting the geochemical characteristics of soil gases Rn and H2 in Shanxi reservoir area.

    • Research and development status of earthquake prevention and disaster mitigation technology from the perspective of patent

      2021, 43(6):1317-1325. DOI: 10.3969/j.issn.1000-0844.2021.06.1317

      Abstract (165) HTML (0) PDF 5.25 M (572) Comment (0) Favorites

      Abstract:The development of earthquake prevention and disaster mitigation needs the support of high technology, so it is important to accurately grasp the global development trend of earthquake prevention and disaster mitigation from the perspective of patent. Based on global patent database incoPat, this paper revealed the global research status, research hotspots, and R & D layout of technologies in the field of earthquake prevention and disaster reduction. The results showed that the research and development of technologies in the field of earthquake prevention and disaster mitigation has rapidly increased since 2004. The total number and growth rate of patents in China far exceed those in other countries, but the overall quality of patents in the United States is the highest. High value patents mainly include vibration sensors and accelerometers, earthquake early warning systems and alarms, seismic walls and seismic structures, isolation bearings, elevator control devices, earthquake emergency command systems, earthquake emergency disposal and escape devices, disaster relief robots, etc.

    • Development characteristics and formation mechanism of Beizhang earth fissure in Linfen basin

      2021, 43(6):1326-1333. DOI: 10.3969/j.issn.1000-0844.2021.06.1326

      Abstract (162) HTML (0) PDF 22.18 M (488) Comment (0) Favorites

      Abstract:Ground fissure disasters occur frequently in Linfen basin, which is located in southern Shanxi Graben System. The earth fissures formed in Houma depression, with large scale and severe disasters, have caused serious economic losses to local residents since 1990s. A case study of Beizhang earth fissures developed in Houma depression since 2007 was discussed in this paper. Through detailed surface investigation and mapping, the plane distribution characteristics of Beizhang earth fissures were found out. Furthermore, a trench was excavated which revealed the cross-section structure features of the earth fissures. According to the results of geophysical exploration, drilling, and InSAR, this paper analyzed the relationship among active fault, over-withdraw groundwater, and earth fissures. Finally, the formation mechanism of Beizhang earth fissures was obtained, and then some prevention measures were proposed to mitigate the hazards of Beizhang earth fissures.

    • Co-seismic fault slip distribution and Coulomb stress change during the Aketao MW6.6 earthquake, 2016

      2021, 43(6):1334-1342. DOI: 10.3969/j.issn.1000-0844.2021.06.1334

      Abstract (216) HTML (0) PDF 17.96 M (538) Comment (0) Favorites

      Abstract:On November 25, 2016, an MW6.6 earthquake occurred in Aketao region, Xinjiang. Based on the Sentinel-1 data, the line-of-sight co-seismic deformation field of the earthquake was obtained, and the Bayesian method was used to invert a single fault with a strike of 106.9°, a dip of 73.8°, and a focal depth of 17.35 km. On the basis of a geometric model of the fault, the slip distribution was inverted by the steepest descent method (SDM). The results showed that there are two slip peaks on the fault plane. The maximum slip on the west side of the fault is 0.66 m, with a depth of 11.7 km; the maximum slip on the east of the fault is 0.83 m, with a depth of 7.5 km. According to the inversion results, the LOS deformation was simulated, and the maximum residual error is ~5 cm. A double-fault geometric model with dip angles of 70.79° and 55.33° was constructed to invert the slip distribution. The results showed that the slip distributions of the single-fault model and the double-fault model are consistent, but the maximum slip value is different. Relative to the slip distribution of the single-fault model, the slip of the double-fault model increases on the west side, with a value of 0.68 m; while it decreases on the east side, with a value of 0.77 m; the maximum residual error is reduced by ~2 cm. The area of the Coulomb stress increase in the double-fault model matches the distribution of aftershocks.

    • Site response of active-source observation stations in the Qilian Mountains

      2021, 43(6):1343-1351. DOI: 10.3969/j.issn.1000-0844.2021.06.1343

      Abstract (167) HTML (0) PDF 10.54 M (644) Comment (0) Favorites

      Abstract:Site response is one of the key factors affecting the accurate determination of source parameters and robust estimation of high-precision crustal medium attenuation. In this paper, the site responses of 40 short-period observation stations in the active-source observation network of Qilian Mountains were analyzed by using the H/V spectra ratio method. The results showed that the 40 short-period observation stations in the Qilian Mountains active-source observation network have amplification (attenuation) effect in varying degrees. According to the characteristics of coda site response curves of 40 stations, they can be divided into three types:flat, amplification, and high-frequency attenuation. The site response curves of some stations are flat in the frequency band of 1-20 Hz, and the site response value is 1-2 times; Most stations have obvious amplification (attenuation) effect in different frequency bands, and the site response value is 0.3-9 times. The lithology of station foundation may be the main factor determining the characteristics and size of site response curve, which has an inverse correlation with the medium density of station foundation.

    • Assessment of seismic buried personnel in urban area: a case study of Tianjin urban area, China

      2021, 43(6):1352-1360. DOI: 10.3969/j.issn.1000-0844.2021.06.1352

      Abstract (174) HTML (0) PDF 11.96 M (605) Comment (0) Favorites

      Abstract:The distribution of seismic buried personnel is an important basis for scientific and effective post-earthquake emergency rescue.To evaluate the distribution of buried personnel caused by the destruction of buildings during earthquake,a relationship model among urban population,indoor rate,and buildings was established at a spatial scale of community.Combined with seismic damage assessment methods of buildings,a rapid assessment model of seismic buried personnel was constructed in this paper.Then,a case study of Tianjin urban area was taken to estimate the amount and distribution of seismic buried personnel under various intensities.Results showed that the night is the high-risk period for seismic buried accidents,and four areas (residential,universities,resident service,and hospitals) have high risk of seismic burial.Furthermore,attention should be fixed on primary and secondary schools in daytime on weekdays.

    • >地震工程
    • Stability analysis of slope and quick determination of slip surface

      2021, 43(6):1361-1367. DOI: 10.3969/j.issn.1000-0844.2021.06.1361

      Abstract (353) HTML (0) PDF 2.69 M (1219) Comment (0) Favorites

      Abstract:To solve the problem of slope stability analysis and slip surface determination in projects,an analytical method was proposed in this paper.First,based on the basic assumption and the geometric relationship of slope,a model for determining the critical slip surface of slope was established,and the governing equation of slip surface was derived.Then,based on the limit equilibrium theory,the analytical expression of safety factor associated with the governing equation of slip surface was derived.Finally,the minimum safety factor and the corresponding critical slip surface could be obtained by solving the minimum value of objective function (unary function) in the definition domain.The calculation results showed that the analysis results of slope stability with the proposed method are basically consistent with those with the traditional limit equilibrium method,and the deviation of the minimum safety factor calculated by the two methods is less than ±5%;The critical slip surface determined by the proposed method is close to that widely searched by the traditional limit equilibrium method.The method in this paper can be used as a reference for efficient and accurate slope stability analysis and slip surface determination.

    • Seismic fragility of a concrete box-girder bridge with and without isolation bearings

      2021, 43(6):1368-1376. DOI: 10.3969/j.issn.1000-0844.2021.06.1368

      Abstract (194) HTML (0) PDF 11.27 M (512) Comment (0) Favorites

      Abstract:To evaluate the seismic fragility of bridges with and without isolation bearings, the numerical models of a three-span concrete box-girder bridge with lead rubber isolation bearings and with non-isolation pot rubber bearings were established. The maximum displacement responses of pier top and bearing under different earthquakes were first analyzed. Then a damage index named ductility ratio of rotation angle was defined to estimate the seismic fragility of bridge piers and bearings. Finally, the wide-bound method was applied to analyze the seismic fragility of bridge system. The analysis results demonstrated that the bearing is the most vulnerable component, and the fragility of the bridge system is greater than pier and bearing. The failure probability of lead rubber bearing is obviously lower than that of non-isolation pot rubber bearing, thus it can be seen that the isolation bearing can effectively reduce the maximum displacement of pier top under earthquake, and the seismic vulnerability of pier with isolation bearings is better than that with non-isolation bearings.

    • Vibration response analysis of school buildings caused by metro trains running on a curved track

      2021, 43(6):1377-1386. DOI: 10.3969/j.issn.1000-0844.2021.06.1377

      Abstract (172) HTML (0) PDF 16.64 M (515) Comment (0) Favorites

      Abstract:Subway has become an important form of rail transit because of its advantages such as fast speed, punctuality, and large traffic volume. However, the problem of environmental vibration caused by metro has become increasingly prominent. In this paper, a middle school construction project in the curved section of Hangzhou Metro Line 3 was taken as an example. The vibration response analysis of a vertical coupling model of the vehicle-common monolithic track system was carried out by using the finite element software ABAQUS, and the vibration source of track considering the influence of track vertical profile irregularity was obtained. By using the finite element software MIDAS GTS/NX, a three-dimensional finite element model of the twin-parallel curve shield tunnel-soil-pile-building system was established. The vibration response of the system was calculated under the excitation of track fulcrum force, and the propagation law of metro vibration wave and the dynamic response characteristics of buildings were studied. According to relevant environmental vibration control standards, the vibration comfort of buildings was evaluated. The results showed that the maximum acceleration and dynamic fulcrum force of rail are about 40 m/s2 and 30 kN, respectively; the vibration of stratum and building are mainly in the vertical direction, and the vibration in the horizontal Y-direction is slightly greater than that in the horizontal X-direction; the ground acceleration decreases gradually with the increase of its distance from the tunnel center line; the dominant frequency of vibration at each building floor is 16-40 Hz; the vibration responses of some building floors exceed the limit requirement of code, and it is suggested that appropriate vibration reduction measures should be taken for metro tracks or buildings.

    • Load transfer characteristics of anchors in frozen soil based on hyperbolic model

      2021, 43(6):1387-1393. DOI: 10.3969/j.issn.1000-0844.2021.06.1387

      Abstract (148) HTML (0) PDF 7.05 M (438) Comment (0) Favorites

      Abstract:In this paper, the influence of different freezing temperatures and moisture contents on the anti-pulling performance of anchor in frozen silt was studied. According to the mechanical characteristics and deformation law of the frozen soil-concrete interface, the hyperbolic model was used to describe the shear displacement characteristics of anchor-frozen soil interface. The anchor load transfer equation considering the influence of temperature and moisture content was established based on the load transfer method. The calculation formulas of shear stress, axial force, and bearing capacity of the anchorage section were then obtained by using the finite difference method, and the rationality of the equation was verified by ABAQUS numerical simulation. The results showed that the uplift bearing capacity of anchor in frozen soil is greater than that at normal temperature. The lower the temperature, the higher the bearing capacity. Under the same load, the attenuation rate of axial force along the depth increases with the decrease of frozen soil temperature. Under the same freezing temperature, the bearing capacity of anchor increases first and then decreases with the increase of moisture content. The ultimate bearing capacity of the anchor can be effectively improved by increasing the anchor diameter.

    • Factors influencing the vibration isolation effect of annular ditches in layered foundation

      2021, 43(6):1394-1401,1418. DOI: 10.3969/j.issn.1000-0844.2021.06.1394

      Abstract (171) HTML (0) PDF 11.58 M (393) Comment (0) Favorites

      Abstract:To explore the influence of geometric parameters of the annular trench in layered foundation on its vibration isolation effect, the amplitude attenuation ratio (Ar value) was adopted for evaluation and analysis in this paper. The area behind trench with Ar value ≤ 0.4 was defined as the effective vibration isolation area. The geometric parameters of annular groove were changed to obtain its influence law on the effective vibration isolation area, so as to determine the influence of different geometric parameters on the vibration isolation effect of annular groove. The results showed that the vibration isolation effect of annular groove is relatively weak when it is near the interface of soil layer. When the width increases from 0.01 to 0.35, the proportion of effective vibration isolation area only changes by 4.8%, namely that the change of width has little influence on the vibration isolation effect. As the arc length of the annular groove increases, the expansion rate of the effective vibration isolation area slows down. After the arc length reaches 2.20, the vibration isolation effect tends to be stable. There are vibration amplification zones at the end of the annular groove and between the vibration source and the groove.

    • Damage prediction and evaluation of bridge pier structures under artificial mainshock-aftershock sequences

      2021, 43(6):1402-1408. DOI: 10.3969/j.issn.1000-0844.2021.06.1402

      Abstract (149) HTML (0) PDF 5.67 M (409) Comment (0) Favorites

      Abstract:Under mainshock-aftershock sequences, the structural damage caused by different fault distance (RJB) and aftershock times are obviously different, so these influencing factors should be considered when evaluating the bridge damage under mainshock-aftershock sequences. Based on OpenSees platform, a continuous girder bridge was taken as an example in this paper. According to different influencing factors, the artificial main-aftershock sequences were selected to carry out the structural damage analysis. The damage results were compared with those of real main-aftershock events to study the feasibility of predicting structural damage by artificial main-aftershock sequences. The analysis results showed that:when considering the aftershock attenuation, the method based on modified PGA amplitude can well simulate the final damage of the structure under real main-aftershock sequences, and can reasonably predict the damage index of the structure. The influencing factors of fault distance and aftershock times should be considered when evaluating the damage of bridge under regional mainshock-aftershock sequences. The damage state of the bridge structure becomes more and more serious with the decrease in fault distance, and the structural damage increment increases with the increase in the number of aftershocks. Under artificial mainshock-aftershock sequences, the larger the fault distance, the smaller the error of incremental damage, and the closer the predicted damage state is to the actual state

    • Dynamic response and deformation analysis of low-angle loess-mudstone landslides induced by earthquake

      2021, 43(6):1409-1418. DOI: 10.3969/j.issn.1000-0844.2021.06.1409

      Abstract (147) HTML (0) PDF 20.37 M (545) Comment (0) Favorites

      Abstract:Based on indoor tests, the static and dynamic mechanical strength parameters of a loess-mudstone landslide were obtained, and a large-scale physical simulation test model for low-angle loess landslides was established. Combined with the finite difference software FLAC3D, the dynamic response law and macro failure characteristics of the loess landslide were analyzed, and the instability evolution law of the landslide under earthquake was described. The results indicated that the low-angle loess-mudstone landslide shows obvious amplification effect along the horizontal and vertical directions under seismic load. With the increase of slope height, the acceleration amplification effect at the shoulder and rear of slope is more obvious. Comparing the acceleration amplification factors of the profiles at the slope toe, slope waist and slope shoulder, it is found that the underlying mudstone has a certain amplification effect on the seismic wave. The contact surface and tension cracks at the shoulder and rear of the slope form an arc sliding surface, then the overlying loess layer slides successively from inside to outside. The sliding force and seismic force of the soil at the slope shoulder cause a large-area and long-distance sliding of the soil at the slope waist, with a maximum sliding distance of about 200 m. In terms of the dynamic response and macro deformation characteristics of the low-angle loess landslide, the numerical simulation results are in good agreement with the shaking table test results.

    • Open trench isolation of site vibration induced by high-speed railway operation

      2021, 43(6):1419-1428. DOI: 10.3969/j.issn.1000-0844.2021.06.1419

      Abstract (195) HTML (0) PDF 16.18 M (549) Comment (0) Favorites

      Abstract:To study the vibration isolation effect of the open trench in layered foundation under the action of high-speed trains, a perfect dynamic model of high-speed vehicle-ballastless track-foundation coupling system was built based on the vehicle-track interaction theory and the finite element method. The effects of the depth, position, width of open trench on the site vibration were discussed, as well as the train speed. The results showed that the site vibration in front of the open trench was enhanced, while the vertical and horizontal vibration behind the open trench was greatly reduced. However, a vibration amplification area located at a specific position weakens the vibration isolation effect. The optimal vibration isolation effect can not be achieved if the open trench is too shallow or too deep. The width of open trench has no obvious effect on the vibration isolation. For the vertical and horizontal vibration of the site caused by higher speed trains, the vibration isolation effect of open trench is more obvious

    • Finite element analysis of the seismic behavior of fabricated shear walls with spiral stirrup confined sleeve grout-anchor

      2021, 43(6):1429-1435,1451. DOI: 10.3969/j.issn.1000-0844.2021.06.1429

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      Abstract:In this paper, the finite element models of a cast-in-place shear wall and a fabricated shear wall with spiral stirrup confined sleeve grout-anchor were established by using the finite element software ABAQUS, and the forward skeleton curves of the two models were simulated under uniaxial loading. The results showed that the seismic index of the shear wall confined by spiral stirrups can be well simulated by setting confined concrete model in the compression zone of edge members. The study results prove the feasibility of using ABAQUS software to simulate the mechanical properties of cast-in-place and prefabricated shear walls, and can provide a research basis for the prefabricated shear walls with grouted connection.

    • Ground motion intensity measures based on SDOF system and high-rise structures

      2021, 43(6):1436-1443. DOI: 10.3969/j.issn.1000-0844.2021.06.1436

      Abstract (158) HTML (0) PDF 11.97 M (815) Comment (0) Favorites

      Abstract:Reasonable ground motion intensity measures are important basis for predicting and evaluating the seismic response of structures. One long-period high-rise frame core tube structure and a single degree of freedom (SDOF) system with 24 periodic points were selected. Based on the time-history analysis results of 100 ground motion records with different focal mechanisms, the correlations between 16 ground motion intensity measures and the structural seismic response were studied, and improved spectral correlation ground motion intensity measures considering the influence of high modes were proposed. The results showed that:(1) The correlations between different ground motion intensity measures and the structural seismic response are quite different. With the increase in natural period of SDOF system, the correlation between intensity measures and the seismic response tend to decrease. (2) According to the analysis of correlations between each intensity measure and seismic responses of the high-rise long-period structure (maximum vertex displacement, maximum base shear, and maximum story drift), the peak ground velocity is recommended as the best intensity measure for high-rise long-period structures. (3) As high-rise long-period structures are significantly affected by high modes, the response spectrum measure with high modes can be used to improve the correlation.

    • Seismic isolation and reinforcement technique of imitated ancient buildings

      2021, 43(6):1444-1451. DOI: 10.3969/j.issn.1000-0844.2021.06.1444

      Abstract (150) HTML (0) PDF 7.59 M (356) Comment (0) Favorites

      Abstract:To strengthen the archaized buildings without destroying their original architectural features, the seismic isolation technique was applied to the archaized buildings with traditional culture in this paper. Two finite element models (with and without isolation) were established by numerical simulation, then the dynamic time history analysis was carried out on the models before and after reinforcement. The displacement and acceleration time history curves of the two models under seismic waves with different frequency spectra were compared and analyzed. The results showed that the seismic response of the structure is obviously reduced by using the seismic isolation technology, and the seismic capacity is significantly improved. The reinforcement cost can be saved and the construction is convenient bu using the proposed method, so it can be used as a reference for similar projects.

    • Vulnerability analysis of a powerhouse at dam toe under the input of obliquely incident seismic waves

      2021, 43(6):1452-1459. DOI: 10.3969/j.issn.1000-0844.2021.06.1452

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      Abstract:To study the influence of obliquely incident seismic waves on the vulnerability of powerhouse at dam toe, the design seismic component consistent with measured ground motion was first obtained on the surface through the superposition of obliquely incident SV-wave field and P-wave field. Meanwhile, in order to consider the dynamic damage of the powerhouse, a program of structural vulnerability analysis considering the system of obliquely incident waves was compiled, in which a damage constitutive model of concrete was embedded. Finally, 26 near-field ground motions were selected from the PEER database and modulated according to the peak ground acceleration (PGA). Taking a powerhouse at dam toe in southwest China as an example, the vulnerability curves of its upstream and downstream walls under the action of obliquely incident system with different intensities were calculated with the incremental dynamic analysis method. Through comparison, it is found that the failure probability of seismic vulnerability curves under vertically incident waves is relatively higher than that under obliquely incident waves, with the maximum difference of 26%. The failure probability of downstream wall is higher than that of upstream wall, and the maximum difference is up to 19%. Thus, the seismic design of powerhouse at dam toe should consider the effect of obliquely incident seismic wave, and more attention should be paid to the seismic safety of downstream wall.

    • Evaluation of modal identification results of concrete arch dams based on seismic records

      2021, 43(6):1460-1471. DOI: 10.3969/j.issn.1000-0844.2021.06.1460

      Abstract (237) HTML (0) PDF 14.86 M (768) Comment (0) Favorites

      Abstract:The modal parameters identified from seismic records of concrete arch dams can reveal the variation of actual dynamic characteristics of the structure during earthquake, thus providing important information for seismic response analysis and post-earthquake damage assessment of the structure. In this paper, the basic principles of common modal identification methods were first introduced. Then, the observation data of two earthquakes were used to identify the modal parameters of Longyangxia arch dam by using two different methods of "input-output" and "output-only". Finally, the rationality of the modal identification results in this paper were analyzed by comparing with the engineering experience values and the research results of other scholars. The research results can provide experience and reference for similar projects.

    • Numerical simulation of the amplification effect of two-dimensional trapezoidal sedimentary basins

      2021, 43(6):1472-1479,1500. DOI: 10.3969/j.issn.1000-0844.2021.06.1472

      Abstract (215) HTML (0) PDF 7.74 M (467) Comment (0) Favorites

      Abstract:As a special type of site effect, the influence of basin effect on ground motion is still being studied. In this paper, a two-dimensional trapezoidal sedimentary basin model was established with the explicit finite element method. According to Buckingham's π theorem, a number of dimensionless parameters affecting the basin effect were defined, i.e., basin depth-width ratio, wave velocity ratio of medium, ratio of basin depth to incident wavelength, and ratio of basin width to incident wavelength. Using Ricker wavelet as the input wave, the influence of above-mentioned dimensionless parameters on the amplification effect of the basin model was studied under vertical incidence of plane SH. It was found that the basin-induced focusing effect becomes obvious with increasing depth-width ratio of basin, and the basin edge effect becomes obvious with decreasing depth-width ratio of basin. With a certain depth-width ratio of basin and incident wave ratio, the maximum amplification coefficient of the basin gradually moves from the center to the edge with increasing ratio of basin width to incident wavelength, indicating more and more obvious edge amplification effect. The wave velocity ratio difference has the greatest effect on the amplification coefficient. With the increase of wave velocity ratio difference, the wave impedance ratio increases and the amplification effect becomes obvious. This study makes the research conclusion on the amplification effect of ground motion in trapezoidal basins have more general significance.

    • Seismic response analysis of the joint between tunnel and cross passage

      2021, 43(6):1480-1486. DOI: 10.3969/j.issn.1000-0844.2021.06.1480

      Abstract (172) HTML (0) PDF 8.45 M (416) Comment (0) Favorites

      Abstract:As an indispensable part of long-distance shield tunnel, the cross passage is usually placed between two tunnels for escape, fire prevention and drainage. Under the action of seismic load, stress concentration is easy to occur at the joint between tunnel and cross passage, which has complex structure and obvious spatial effect, thus resulting in structural damage and immeasurable earthquake damage. Based on the finite difference software FLAC3D, a three-dimensional model for two-line parallel tunnel and cross passage was established by taking the typical silty clay in Tianjin as an example. Under the input of sine wave, the stress and deformation of the joint between tunnel and cross passage were analyzed, and the effects of tunnel buried depth and the diameter and length of cross passage on the seismic response of joint were discussed. Based on Fish language, a finite difference model which can simulate different incident directions of seismic waves was established. The calculation results showed that different incident directions of seismic waves have a significant impact on the stress of structural joint.

    • Random response analysis of base-isolated structures based on probability density evolution

      2021, 43(6):1487-1494. DOI: 10.3969/j.issn.1000-0844.2021.06.1487

      Abstract (145) HTML (0) PDF 6.05 M (438) Comment (0) Favorites

      Abstract:The probability density evolution method was used to analyze the linear random responses of seismic structures and base-isolated structures under frequent earthquakes. The physical random function model was introduced to select disperse representative points from multi-dimensional random variables by utilizing the number theory collocation method. Then the discrete representative points were used to synthesize seismic acceleration time-history samples as random excitation. After obtaining the structural response and its related derivatives, the TVD difference scheme was applied to solve the generalized probability density evolution equation, thus obtaining the time-varying probability density of the solved response and its evolution. The results showed that the base-isolated structure has better shock absorption performance than the anti-seismic structure under random earthquakes. The isolation layer can reduce the standard deviation of structural displacement response and the discretization of structural response. The probability density evolution method can not only give the second-order statistical moment of structural response, but also fully reflect the time-varying probability information of structural response. The probability density function distribution of displacement response, which evolves with time, does not obey normal distribution or other common distribution.

    • Simulation of seismic ray tracing based on Newton iteration method to solve group velocity

      2021, 43(6):1495-1500. DOI: 10.3969/j.issn.1000-0844.2021.06.1495

      Abstract (199) HTML (0) PDF 5.30 M (551) Comment (0) Favorites

      Abstract:Anisotropy generally exists in underground media. Nowadays, seismic wave ray tracing based on anisotropy is mostly carried out in weakly anisotropic media by using the approximate formula of group velocity, which will lead to large errors in strongly anisotropic media, and can not really simulate the propagation law of seismic wave. According to the anisotropy in underground media and the basic propagation law of seismic wave, this paper proposed the Newton iteration method for solving the group velocity. Based on the Paraview platform, a 3D geological model was automatically constructed, and the shortest path method was used to simulate and visualize the seismic ray tracing. Taking the northern Shanxi rift zone in the North China Craton as an example, the expression of velocity heterogeneity and anisotropy in complex 3D geology was realized. The experimental results showed that the proposed method can mitigate the influence of anisotropy on seismic wave propagation simulation, clearly express the geological structure and anisotropic characteristics of the study area, so it can be better applied in the interpretation of complex 3D geological structure.

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