• Volume 42,Issue 4,2020 Table of Contents
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    • >结构
    • Structural Damage Identification Based on Analogous Flexibility Difference Curvature and Perturbation of Frequency

      2020, 42(4):825-832. DOI: 10.3969/j.issn.1000-0844.2020.04.825

      Abstract (495) HTML (0) PDF 1.28 M (768) Comment (0) Favorites

      Abstract:To improve the efficiency of damage diagnosis of beam structures, a structural damage identification method, based on the analogous flexibility difference curvature and frequency perturbation was established. First, according to the theory of structural vibration, the calculation formula of generalized flexibility matrix was studied. Utilizing the high sensitivity of modal flexibility to structural damage, the damage location index, based on flexibility difference curvature, was improved, and the damage index of LCFC (the difference of likeness curvature of flexibility coefficient) was defined and used to preliminarily identify damage. Identification result of structural damage was confirmed based on matrix perturbation. Considering various damage conditions, damage identification of the simply supported beam structure was verified by numerical simulation. Results showed that the LCFC index has a good diagnostic effect on the damage location of beam structures using only the first mode. Calculation workload of the index was small. For multi-damage cases with boundary damage elements, the LCFC index was effective when the damage degree was >10%. When the damage degree was < 25%, accuracy of the second-order perturbation identification results was high and the relative error was significantly lower than that of the first-order perturbation identification results, which proved the practicability, effectiveness, and accuracy of the method.

    • Orthogonality of Transverse Vibration Modes of Single, Fully-Embedded Piles

      2020, 42(4):833-839. DOI: 10.3969/j.issn.1000-0844.2020.04.833

      Abstract (400) HTML (0) PDF 1.03 M (567) Comment (0) Favorites

      Abstract:The Timoshenko beam model was used as the flexural wave propagation model in a single, fully-embedded pile. Based on the differential equation of transverse vibration of single, fully-embedded piles in a frequency domain, combined with the force balance and displacement compatibility equations of nodes and the dual transformation of the internal forces and displacements in two local dual coordinate systems, the orthogonality conditions of transverse vibration modes of a single, fully-embedded pile were derived. By virtue of the reverberation-ray matrix method, the natural frequencies, attenuation coefficients, and modes corresponding to different natural frequencies for a single, fully-embedded pile were solved. A specific case study is proposed to verify the correctness of the orthogonality conditions of modes.

    • Study of Progressive Collapse of Transmission Tower-Line System Considering Different Incident Angles of Earthquake Waves

      2020, 42(4):840-846. DOI: 10.3969/j.issn.1000-0844.2020.04.840

      Abstract (380) HTML (0) PDF 12.91 M (850) Comment (0) Favorites

      Abstract:This paper analyzes the problem of the progressive collapse of a long-span transmission tower-line system by considering different incident angles of earthquake waves. Based on a practical project example, we established a finite element model in ABAQUS that consists of two transmission towers and three transmission lines. We then studied the collapse mechanism and failure process of the transmission tower-line system with respect to three typical seismic records (El Centro, Taft, and Northridge waves). The research results show that under seismic action the longitudinal direction is relatively more unfavorable than the lateral direction. In different types of members, the auxiliary material is most likely to fail and the bracing rod to be most seriously damaged. Different seismic waves and incident directions will result in different positions of weakness.

    • Effect of CFRP Sheets on Seismic Performance of Precast Segmental Piers

      2020, 42(4):847-855. DOI: 10.3969/j.issn.1000-0844.2020.04.847

      Abstract (362) HTML (0) PDF 13.01 M (1042) Comment (0) Favorites

      Abstract:To improve the seismic performance of precast segmental piers during earthquake, carbon-fiber-reinforced plastics (CFRPs) were used to reinforce the vulnerable parts of precast segmental piers. Based on the results of previous experiments, we established a three-dimensional solid finite element model of a precast segmental pier and analyzed the restoring force characteristics and damage sustained by the pier under cyclic loading. After reinforcing the bottom segments of the pier with either stirrup reinforcement or an outsourced CFRP sheet, we compared the effects of the two reinforcement methods on its seismic performance. The results showed that the bottom section of the CFRP-wrapped pier enhanced the overall stiffness and bearing capacity of the pier and made the stiffness degradation of the pier gentler. Based on the results, we can conclude that CFRP reinforcement is conducive to the stability of the precast segmental pier under earthquake and can better ensure the safety of the bridge.

    • Experimental Study on the Shear Behavior of Masonry Structures of Traditional Rural Buildings

      2020, 42(4):856-861,947. DOI: 10.3969/j.issn.1000-0844.2020.04.856

      Abstract (425) HTML (0) PDF 4.95 M (783) Comment (0) Favorites

      Abstract:Brick masonry structure is the main structural form of traditional rural buildings. Hence, the accurate evaluation of its seismic capacity is of important research significance. In this study, a compressive strength test was first carried out on four typical mortars (cement, lime, slag, and mud) to examine the shear performance of brick masonry structures. Second, a shear strength test along mortar joints was carried out on a brick masonry structure built with the four mortars. A modified formula of the masonry shear strength was obtained by comparing the average and formula values of the shear strength of traditional old red brick masonry structures. Finally, an accurate shear strength evaluation of brick masonry structures was carried out by comparing modified, standard, and design values. In this research, technical support and scientific basis for seismic performance evaluation, seismic strengthening, and seismic design of traditional rural brick masonry structures are mainly provided.

    • Seismic Performance Analysis of Existing Simply Supported Bridges Subjected to Near-fault Ground Motions in the Transverse Direction

      2020, 42(4):862-871. DOI: 10.3969/j.issn.1000-0844.2020.04.862

      Abstract (503) HTML (0) PDF 7.20 M (807) Comment (0) Favorites

      Abstract:To investigate the influence of material degradation on the lateral seismic behavior of simply supported bridges in the near-fault area and to reveal the variation of the combination isolation effects of bearing + shear key with respect to the service time, an actual bridge subjected to the Wenchuan earthquake was taken as an example and a nonlinear time-dependent analysis model of the bridge was established considering the time-varying characteristics of steel corrosion and concrete carbonation. Time history analysis was applied to study the deterioration trend of various members of the bridge. A parametric study was conducted to examine the time-varying influence of the shear key strength. Results show that the flexural resistance of the pier column is continuously reduced and the damage level increased as the service life increased. The material degradation improves the relative displacement-control capacity of the shear key, which causes the decrease of bearing displacement. However, the overall seismic performance of the bridge decreases due to the increased damage of the pier. The shear key’s great strength corresponds to its strong displacement-control capacity. However, the increased strength of the shear key will reduce the isolation effects of the bearing and increase the plastic deformation of the pier. As the service time increases, the increased strength of the shear key will be more disadvantageous for the pier. When the strength of the shear key is designed to be 20%-30%, the displacement of the bearing and the girder in different service years can be effectively controlled, and the damage of the pier is also in a repairable state. The 20%-30% shear key strength is a reasonable strength value for the bridge example used in this paper and is consistent with the Caltrans recommendation in America.

    • Incremental Dynamic Response of Inter-story Isolation System on Top of Columns

      2020, 42(4):872-880. DOI: 10.3969/j.issn.1000-0844.2020.04.872

      Abstract (392) HTML (0) PDF 5.48 M (934) Comment (0) Favorites

      Abstract:To study the seismic performance of inter-story isolation systems with and without a straining beam on the top of cantilever columns, we used the incremental dynamic analysis (IDA) method to simulate the whole process from elasticity to elasto-plasticity until structural collapse. We obtained the story drift ratio and peak acceleration by modulating the amplitude of the ground motions. We then plotted IDA curves to explore the influence of the straining beam on the dynamic response of the isolation structure and to study the seismic performances of the two structures. The results show that at the same performance point, the straining beam has no effect on the bending moment and curvature values of the fiber hinge, but at different performance points, the state of the fiber hinge is significantly different. The difference between the peak acceleration of the two systems increases from the normal-use state to the collapse-prevention state. When subjected to extremely rare earthquakes, the seismic performance of the sub-structure in the inter-story isolation system with a straining beam on top of the cantilever column is higher than that without a straining beam.

    • >地震科学
    • Effects of HVDC Power Transmission Interference on Geoelectric Field Observations in Jiangsu Province

      2020, 42(4):881-889. DOI: 10.3969/j.issn.1000-0844.2020.04.881

      Abstract (467) HTML (0) PDF 7.01 M (989) Comment (0) Favorites

      Abstract:This work mainly analyzes and summarizes the observation data of four geoelectric field stations in Jiangsu Province from 2015 to 2019 subjected to interference by national high-voltage direct current (HVDC) transmission lines. The influence characteristics and data interference magnitude of the Xitai, Jinnan, Jinsu, and Changxuan lines are mainly considered. The conclusions are as follows. (1) The interference of the HVDC transmission lines with the geoelectric field observation data is a far-field interference. Under the interference of the same HVDC transmission lines, the range of the change ratio of the observation data at a long polar distance and short polar distance of the same station in the same direction is close to 1. (2) The forms, directions, and ranges of the data change of different stations caused by HVDC line interference differ in terms of station location, HVDC converter station location, relative position of ground electrode, and underground transmission medium. The results can provide a reference for the discrimination of geoelectric field observations disturbed by HVDC transmission lines. They may also be applied to geoelectric field observation data.

    • Preliminary Study on the Extraction of the Anisotropy Anomaly of Daily Amplitude Variations in a Geoelectric Field

      2020, 42(4):890-898. DOI: 10.3969/j.issn.1000-0844.2020.04.890

      Abstract (432) HTML (0) PDF 3.02 M (558) Comment (0) Favorites

      Abstract:In this study, the anisotropy degree (S-value) method of daily amplitude variations in a geoelectric field was proposed. Seismic reflection results obtained using the proposed method at different stations were compared and analyzed. Results showed that (1) the method can recognize anomaly precursors. The short-term anomalies of M=5.0 earthquakes with an epicenter distance of about 200 km can be recorded at each station within 4 months before an earthquake. The occurrence time of anomalies at different stations is related to epicenter distance. (2) Under normal circumstances, the S-value curve generally fluctuates within two times the mean square deviation of the mean. When the S-value in 2 days exceeds the value of two times the mean square deviation of the mean and the curved form is distorted, an anomaly appears. (3) Seismic reflection results from each station remarkably differ. Their difference may be related to the electrical structure of an underground medium, a seismological structure, and the related structure of each station.

    • Impact and Countermeasures of HVDC Transmission on Geomagnetic Observation in Gansu Province

      2020, 42(4):899-906. DOI: 10.3969/j.issn.1000-0844.2020.04.899

      Abstract (389) HTML (0) PDF 1.65 M (649) Comment (0) Favorites

      Abstract:With the continually expanding scale of the national power grid, an increasing number of high voltage direct current (HVDC) transmission projects have been employed; this has had an inevitable impact on obtaining geomagnetic observation data on both sides of the transmission lines. Five HVDC transmission lines currently cause interference at Gansu geomagnetic station, and it is thus extremely important to correctly identify the extent of HVDC transmission interference on geomagnetic observation data to enable its correct preprocessing. In this paper, the influence of HVDC transmission lines on geomagnetic observation data is identified by comparing observation data of a single station with those from multiple stations. The results show that: (1) HVDC transmission has an obvious influence on the geomagnetic Z component, but the influence on the D and H components is not obvious. (2) The HVDC influence forms on geomagnetic observation are mainly a square wave type, slowly changing type, trapezoid type, and composite type. (3) Analyzing the characteristics and forms of HVDC with respect to its influence on geomagnetic observation data is useful for correctly preprocessing the observation data and will provide a basis for conducting automated computer processing in the future.

    • Research on a Zigbee-Based Method for Improving Seismic Data Accuracy

      2020, 42(4):907-913. DOI: 10.3969/j.issn.1000-0844.2020.04.907

      Abstract (374) HTML (0) PDF 3.30 M (770) Comment (0) Favorites

      Abstract:Considering that the traditional seismic exploration methods cannot accurately obtain high-precision exploration data, a method based on Zigbee to improve the accuracy of seismic exploration data is proposed. The polar coordinate method of a total station is used for spatial positioning and zoning according to the geology and surface structure of the seismic exploration area. The propagation mode of seismic wave and the seismic resolution factors that affect the detection effect were analyzed using an exploration instrument with a differential GPS positioning module, and the seismic data were obtained. The seismic damage data were detected and tracked using the ray tracing technology and were then extracted and repaired by a special detection instrument. The detection system composed of an MEMS accelerometer and Zigbee module was established, and the seismic exploration data were effectively detected according to the topological structure network, in order to improve the accuracy of seismic exploration. According to the simulation experiment, the proposed method has high accuracy and validity of seismic exploration data and can provide great help for related work.

    • Observation Data Analysis of Vertical Geoelectric Field with New Technology: A Case Study Based on Data from Pingcheng Station

      2020, 42(4):914-918. DOI: 10.3969/j.issn.1000-0844.2020.04.914

      Abstract (440) HTML (0) PDF 1.80 M (569) Comment (0) Favorites

      Abstract:The data of the horizontal and vertical geoelectric fields at Pingcheng Station were analyzed. Results showed that (1) the observation data of the vertical geoelectric field with solid nonpolarized electrodes are basically consistent, but a large potential difference is found between a lead electrode and a solid nonpolarized electrode. (2) The vertical geoelectric field data display a strong diurnal variation. The diurnal amplitude variation in A1C1, A2C1, and A3C1 channels is about 5.85 mV/km, whereas the diurnal amplitude variation in B1C1, B2C1, and B3C1 channels is about 10.02 mV/km. (3) The vertical geoelectric field has an obvious diurnal variation with dominant frequencies of 12 and 24 h.

    • Structural Characteristics of the Yuncheng Basin, China, Based on Bouguer Gravity Anomalies

      2020, 42(4):919-926. DOI: 10.3969/j.issn.1000-0844.2020.04.919

      Abstract (463) HTML (0) PDF 19.87 M (1029) Comment (0) Favorites

      Abstract:For this paper, a wavelet decomposition was carried out on the Bouguer gravity data of the Yuncheng Basin, China, and the surrounding area. Gravitational anomalies of different orders in the study area were obtained. According to the wavelet transform results of the different orders and the geological tectonic environment of the region, a detailed map of the Bouguer gravity anomaly zone, with its characteristic wavelet transform, was thoroughly analyzed. The distribution characteristics of the structural phenomena at different depths of the crust, which were revealed by the anomalies, were studied. The results showed that the wavelet transform details corresponded well with the uplift and depression in the crust and the fault structure. This study should provide a reference for the structural characteristics and crustal structure in the Yuncheng basin.

    • Exploration Results of Quaternary Activities along the Cangdong Fault

      2020, 42(4):927-933. DOI: 10.3969/j.issn.1000-0844.2020.04.927

      Abstract (485) HTML (0) PDF 1.87 M (676) Comment (0) Favorites

      Abstract:Based on the results of artificial seismic exploration, three profiles of boreholes are arranged in the North Shanlingzi Village of Dongli District, Zhongtang Village of Dagang District, and Beihuaidian Village of Ninghe County. Through the identification of microfossils and the test of strata age, the locations of the marine strata of boreholes are obtained in this work. The activity of the Cangdong fault is analyzed and studied through strata contrast and the paleomagnetic test results of BZ1 bore in Zhongtang Village. The result indicates that the activity sign of the Cangdong fault has not been found since the Late Pleistocene and its latest active age might be in the Middle Pleistocene. The contrast result of the marine strata of the Beihuandian borehole profile in the northern part of the Cangdong fault and the Zhongtang borehole profile in the southern part shows that there is a little difference in activity between the southern and northern sections of the Cangdong fault, divided by the Haihe fault. In addition, previous research has shown that the marine strata observation may better reflect the information of earthquakes. Besides the Cangdong fault, the marine strata of 21 boreholes on the south Tianjin fault, north Tianjin fault, and Haihe fault were also identified, and the location of marine strata will also be determined in the current Jiyunhe fault detection.

    • Effect of HVDC Transmission on Geoelectric Field Observation in Gansu Province

      2020, 42(4):934-940. DOI: 10.3969/j.issn.1000-0844.2020.04.934

      Abstract (454) HTML (0) PDF 3.25 M (529) Comment (0) Favorites

      Abstract:In this study, the interference of Guazhou, Jiayuguan, and Gaotai geoelectric field observations in the Hexi Area of Gansu Province via the Jiuquan-Hunan ±800 kV HVDC transmission project was taken as an example to analyze the changes in anomalies during geoelectric field observation. The anomaly mechanism and the basic principles of HVDC transmission were discussed, and the possible effects of different distances, conductivities, and grounding currents on the observation were calculated. Under ideal conditions, the influence of HVDC on geoelectric field observation was directly proportional to the grounding current and inversely proportional to the square of the distance between the observation site and the earth electrode of a converter station and the conductivity of the affected area. Least square fitting was conducted to eliminate the interference, and the effect was ideal.

    • Detection of Missing Earthquakes and Activity Characteristics of the Mangya M5.0 Earthquake Sequence in Qinghai

      2020, 42(4):941-947. DOI: 10.3969/j.issn.1000-0844.2020.04.941

      Abstract (478) HTML (0) PDF 11.10 M (1072) Comment (0) Favorites

      Abstract:The Mangya M5.0 earthquake that occurred in Qinghai Province on March 28, 2019, was taken as a study example, and nine aftershocks (ML≥1.0) with a high signal-noise ratio after the mainshock were selected as template events. A template-matched technique was used to scan the continuous waveform that occurred in 30 days after the mainshock. Results showed that 13 earthquakes were missed, and they were about 43% of the original earthquake catalog. This work could provide relatively complete aftershock sequence data for the following studies on seismicity or seismic risk assessment in the study area. The comparison of the change in b value before and after template matching revealed that b value decreased slightly after template matching. This result confirmed that b value commonly decreases in a short time after strong earthquakes occur. The extended catalog repositioned with a double difference technique revealed that earthquakes were mainly distributed in the north side of the Mangya-Youshashan fault, showing the characteristics of a clustered distribution.

    • >岩土
    • Scattering of qP-waves by a Lined Tunnel Buried in Transversely Isotropic Media

      2020, 42(4):948-954. DOI: 10.3969/j.issn.1000-0844.2020.04.948

      Abstract (532) HTML (0) PDF 12.65 M (1006) Comment (0) Favorites

      Abstract:The seismic response of a lined tunnel buried in a transversely isotropic (TI) half-space under incident qP-waves was studied by adopting the indirect boundary element method (IBEM) and the "conjunction" technique. Inheriting the advantages of both the half-space and full-space Green’s functions, a model of a lined tunnel buried in a TI-layered, viscoelastic half-space was deconstructed into the excavated layered half-space region and the enclosed circle region. First, the direct stiffness method was adopted to solve dynamic responses of the displacements and stresses due to the qP-wave incident from the underlying TI half-space (free fields). Then, a set of hypothetical distributed loads were applied both on the elements of the open surface in the layered half-space domain and on the enclosed domain boundary to calculate Green’s functions (scattered fields). Finally, densities of the hypothetical loads were determined by introducing boundary conditions, and the dynamic stress generated at the inner surface of the lining was obtained. The validity of the proposed method was verified by comparing its results with those of existing numerical solutions. By taking a lined tunnel buried in a homogeneous TI half-space and in a single TI-layered half-space as examples, numerical calculations were performed in the frequency domain, and the effects of material anisotropy, incident angle, and frequency of excitation on the dynamic stress were studied. Numerical results illustrated that the dynamic stress on the inner surface of the lined tunnel was very sensitive to the TI parameters, and there were significant difference between the TI medium and the corresponding isotropic case. The change in TI parameters altered the resonant frequency of the layer and further altered the dynamic interaction between the layer and the tunnel, which led to the change in dynamic stress in terms of magnitude and spatial distribution. Generally, the dynamic stress of the isotropic medium was litter than that of the TI medium in the two numerical examples. Therefore, the material anisotropy of the site should be considered for the seismic design of tunnels in practical engineering.

    • Seismic Liquefaction Characteristics of Saturated Sand with a Low Permeable Covering Layer

      2020, 42(4):955-959,988. DOI: 10.3969/j.issn.1000-0844.2020.04.955

      Abstract (493) HTML (0) PDF 4.21 M (1319) Comment (0) Favorites

      Abstract:In this paper, a group of centrifuge-shaking table tests were performed for saturated sand with a weak permeable covering layer. OpenSees was used to carry out the numerical simulation on the test model. Experimental and numerical results were compared and discussed. The horizontal Arias Intensity (Ia) was used to measure ground motion intensity. When liquefaction occurred, the horizontal Ia was taken as the anti-liquefaction strength of the soil. The reaction of saturated sand subjected to different earthquake waves was calculated by OpenSees to test the accuracy of Ia as a measure of anti-liquefaction strength. Results showed that ground motion intensity, which can cause liquefaction of saturated sand, increases with increasing depth. When incident seismic intensity reached the requirement for the liquefaction of sand, liquefaction occurred.

    • Propagation Characteristics of S-waves in Unsaturated Soil

      2020, 42(4):960-966. DOI: 10.3969/j.issn.1000-0844.2020.04.960

      Abstract (454) HTML (0) PDF 5.68 M (2235) Comment (0) Favorites

      Abstract:Based on research into unsaturated porous media, propagation characteristics of S-waves in unsaturated soil were studied by considering the interaction between liquid and gas phases in the pores. Elastic wave equations were established according to the mass balance equation, the momentum balance equation, and the effective stress principle of unsaturated soil. The dispersion equation of S-waves in unsaturated soil was obtained after theoretical deduction. Finally, the influences of saturation degree, frequency, and intrinsic permeability coefficient on S-wave velocity and attenuation coefficient are discussed using numerical examples. Results showed that the wave velocity of S-waves is hardly affected by degree of saturation, but decreases with increasing frequency; it first remains unchanged, then increases with an increasing intrinsic permeability coefficient The attenuation coefficient of S-waves increases with increasing saturation degree and frequency; however, with increasing intrinsic permeability coefficient, it first remains unchanged, then increases, then finally decreases.

    • A Comparative Analysis of Forced Displacement and Response Acceleration Methods for Underground Structures

      2020, 42(4):967-972. DOI: 10.3969/j.issn.1000-0844.2020.04.967

      Abstract (471) HTML (0) PDF 2.13 M (916) Comment (0) Favorites

      Abstract:Two kinds of simplified analytical methods are discussed. Both were derived from the response deformation method based on the premise that the deformation of an underground structure depends on the deformation of the foundation soil. One method applied ground displacement to the boundary of the finite element model to simulate seismic load; the other applied ground acceleration to the integral finite element model to simulate seismic load. Both simplified analytical methods avoided calculating the value of the spring stiffness and improved the computational efficiency. Calculated results with different ground motion intensities and lateral margins were obtained and checked with the results of the dynamic time-history method. They showed that the results of the two simplified analytical methods were satisfactory as the ground motion intensity increased. The lateral margin had to be twice the width of the structure when using the forced displacement method, and needed to be more than three times the width of the structure when using the response acceleration method.

    • Comparative Experimental Study on Dynamic Characteristics of Soft Clay under Different Cyclic Loads

      2020, 42(4):973-981. DOI: 10.3969/j.issn.1000-0844.2020.06.973

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      Abstract:Investigation of long-term settlement and dynamic mechanical properties of soft clay under cyclic loads is important to its subgrade design. In this study, we determined the effects of vibration waveform, drainage condition, and dynamic stress ratio on the dynamic strain and dynamic pore pressure of soft clay under undrained condition through GDS dynamic triaxial test. Results show that the drainage condition exhibits the most serious influence on the dynamic strain and dynamic pore pressure of saturated soft clay. Under the condition of partial drainage, the dynamic pore pressure gradually dissipates and the dynamic strain develops rapidly. The vibration waveform also influences the dynamic strain and pore pressure of soft clay, and these parameters easily reach the maximum value under the action of unidirectional pure pressure semi-sine wave. The dynamic stress ratio has a great effect on pore pressure under few vibration times. However, the dynamic stress ratio minimally affects pore pressure in the normalized pore pressure model. Through the above analysis, a pore pressure growth model including the indices of cyclic vibration time and pore pressure, was established.

    • Shaking Table Test Design and Numerical Simulation of Pile-Raft Foundation

      2020, 42(4):982-988. DOI: 10.3969/j.issn.1000-0844.2020.04.982

      Abstract (399) HTML (0) PDF 5.94 M (943) Comment (0) Favorites

      Abstract:A shaking table experiment was designed to study the seismic performance of the pile–raft foundation of a nuclear power project. Numerical simulation was carried out with ABAQUS software to verify the feasibility of the test design scheme. The scale of the experiment was set as 1: 200 based on the actual project. Seismic waves were selected from the relevant technical documents and specifications of nuclear power plant structure at home and abroad. Artificial waves fitted by R.G1.60 standard response spectrum were inputted to calculate the case. Results show that the displacement at the top of pile is larger than that at the bottom of pile. The acceleration and displacement of the raft are smaller than those of the pile. This study provides guidance for the improvement of the shaking table test and reference for practical engineering design.

    • Dynamic Response of Foundation Pits Subjected to Explosion Induced by Gas Leakage

      2020, 42(4):989-995,1006. DOI: 10.3969/j.issn.1000-0844.2020.04.989

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      Abstract:To study the explosive effect induced by gas leakage on the foundation pit, the TNO multi-energy method is used to calculate the explosive load of gas leakage. The explosive impact load was then applied on a certain range around the foundation pit. First, assuming that a sudden explosion of fuel gas occurred at different excavation stages, the numerical model was then established to simulate the explosion at different excavation stages with the finite element software ABAQUS. The effect of the explosive load on the deformation of the foundation pit at different excavation stages was studied. Results showed that the effect of explosive load on the horizontal displacement of the foundation pit is significant, while the effect on the rebound of the soil in the pit is not clear. In addition, if the last prop is not installed after the excavation, the effect of explosive load on the supporting structure of the pit will be more significant.

    • Seismic Dynamic Response Characteristics of Loess Tunnel Portal Section with Consideration of Tunneling Elevation on the Slope

      2020, 42(4):996-1006. DOI: 10.3969/j.issn.1000-0844.2020.04.996

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      Abstract:In this study, we conducted a large-scale shaking-table model test and a numerical simulation using Midas-GTS finite element software to obtain the dynamic response characteristics and failure process of a loess tunnel portal section under earthquake action and the transmission law of the seismic wave. We then analyzed the main factors influencing the dynamic response of the loess tunnel portal section. The results reveal that the collapse of the slope along the arc fracture surface is affected by the coupled effect of shearing at the toe and cracking at the top of the slope. The slope will have a significant amplification effect on the seismic waves at the predominant frequency. The tunnel free surface was found to be the main factor affecting the seismic dynamic response of the tunnel portal section. The length of the anti-seismic section at the tunnel opening should be five times the portal diameter with the consideration of tunneling elevation on the slope. The results obtained from the shaking-table model test and numerical calculation agree well with respect to the three response characteristics: displacement, acceleration, and stress, which verifies the results as being reasonable and reliable. These research results provide useful reference information for tunnel engineering design and the anti-seismic theoretical research of underground structures.

    • Change Law of the Dynamic Elastic Modulus of Reinforced Loess in Lishi Area

      2020, 42(4):1007-1012. DOI: 10.3969/j.issn.1000-0844.2020.04.1007

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      Abstract:In view of the unclear evolution mechanism of the dynamic modulus of reinforced soil and the complicated test process, combined with the GDS dynamic triaxial test, this study conducted a dynamic elastic modulus test of reinforced soil under the influence of different factors, i.e., confining pressure, water content, reinforced materials, and reinforced layers. Three conclusions were drawn: (1) The dynamic elastic modulus of reinforced soil was affected by water content, confining pressure, reinforced materials, and number of reinforced layers, in which the influence order is as follows: water content > confining pressure > number of reinforced layers > reinforced material. (2) The dynamic elastic modulus of reinforced soil is mainly affected by the coupling and arrangement of the reinforced materials and soil particles. (3) This paper proposed a prediction model of dynamic elastic modulus attenuation under the influence of different factors, and its expression conformed to the hyperbolic law. The conclusion has a certain guiding significance for the design and treatment of roadbeds.

    • Experimental Study of the Dynamic Shear Modulus and Damping Ratio of Silty Clay on Eastern Henan Plain

      2020, 42(4):1013-1018. DOI: 10.3969/j.issn.1000-0844.2020.04.1013

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      Abstract:The dynamic shear modulus and damping ratio of silty clay are important parameters for evaluating the dynamic stability of building sites on the Eastern Henan Plain. To analyze the dynamic characteristics of silty clay on the Eastern Henan Plain, we conducted a dynamic triaxial test of the silty clay using a bidirectional-vibration triaxial test system. We also studied the influence of the state and consolidation pressure of silty clay on its dynamic shear modulus and damping ratio. The results indicate that the changes in the dynamic characteristics of plasticized silty clay (PSC) and soft plastic silty clay (SSC) are similar, with increases in shear strain, their dynamic shear modulus ratios decrease, and the damping ratios increase. Under the same strain, the dynamic shear modulus ratio of SSC and the damping ratio of PSC increase with increases in the consolidation pressure. Under the same test conditions, the maximum dynamic shear modulus of PSC was found to be greater than that of SSC. The dynamic shear moduli of PSC and SSC decrease rapidly when the shear strain is less than 0.01%, and tend to be consistent with each other when the shear strain reaches 0.03%. According to existing research on the dynamic shear modulus and damping ratio of silty clay, combined with experimental data, we propose a mathematical model for the dynamic shear modulus ratio and damping ratio of silty clay with shear strain. The results of this study provide a basis for evaluations of dynamic stability at silty-clay construction sites on the Eastern Henan Plain.

    • >震灾与综合
    • Investigation of Building Damage Characteristics and Human Casualties in Relation to the MS4.7, MS4.3, and MS4.9 Earthquakes Occurring in Rong County, Sichuan Province

      2020, 42(4):1019-1023,1034. DOI: 10.3969/j.issn.1000-0844.2020.04.1019

      Abstract (367) HTML (0) PDF 12.42 M (877) Comment (0) Favorites

      Abstract:The seismic damage characteristics of buildings and associated human injuries were analyzed based on field investigation data obtained for the MS4.7, MS4.3, and MS4.9 earthquakes in Rong County, Sichuan Province. The results indicate that the types of building predominantly damaged in the disaster area are masonry-concrete structures, brick-wood structures, and civil structures; of these, brick-wood and civil structures are more vulnerable to seismic damage. Human injuries mainly occurred in relation to building damage. The main reasons for these phenomena are the old ages of buildings in the area, the inadequate building structure, and the poor seismic performance of the houses. In addition, frequent earthquakes occurring within a short time frame caused a remarkable accumulation of earthquake damage, and people in the area were knew little about earthquake prevention and mitigation.

    • Simulation of Stochastic Seismic Event Set Using the Earthquake Catastrophe Model

      2020, 42(4):1024-1034. DOI: 10.3969/j.issn.1000-0844.2020.04.1024

      Abstract (551) HTML (0) PDF 15.61 M (748) Comment (0) Favorites

      Abstract:Earthquakes are a type of major natural disaster that result in serious casualties and property losses. Seismic hazard analysis is one of the main modules in the seismic catastrophe model. Traditional probabilistic analyses of seismic hazard are based on the potential source model, seismicity model, and ground motion attenuation model, which use the probability method to determine the seismic hazard of the target site. This hazard represents the combined effect of all earthquakes on the site. However, the effect of a single seismic event on the site should be used in seismic risk analyses based on the earthquake catastrophe model, so the potential focal area must be converted into a series of individual seismic events. In this study, based on the potential focal area and seismicity model adopted in the fifth seismic ground motion parameters of China’s zonation map, we used the Monte Carlo method to simulate the seismic event set that conforms to the time, space, and intensity distribution characteristics of seismic activity in China. In the simulation of seismic events, the basic theory states that the occurrence time of earthquakes follows a Poisson distribution, the magnitude distribution is described by the Gutenberg-Richard law, and the spatial distribution is described by the potential focal area and the earthquake occurrence rate. The simulated earthquake events included the following parameters: time (year, month, and day), location (longitude, latitude), depth, magnitude, fault strike, and attenuation characteristics. The results show that this simulated seismic event set can meet the requirements of seismic hazard analysis in the seismic catastrophe model.

    • Seismic Response of Basin Site under Plane Wave with Different Bedrock Inclinations

      2020, 42(4):1035-1042. DOI: 10.3969/j.issn.1000-0844.2020.04.1035

      Abstract (286) HTML (0) PDF 22.57 M (790) Comment (0) Favorites

      Abstract:To analyze the dynamic response at the surface of a basin site under seismic waves with different bedrock inclinations, a 2D layered basin with a depth of 100 m and width of 2 km was selected. Under the input of a Dirac pulse with a duration of 0.25 s, the seismic responses of the basin subjected to vertical incident P wave and SV wave were analyzed with bedrock inclinations of 10°, 20°, 30°, and 40°. The result shows that the incident wave had a wave-type transformation at the inclined bedrock; meanwhile, surface waves were generated and were concentrated at the center area of the basin. With increase in the bedrock inclinations at the valley sides, the dominant frequency at the center of the earth surface tended to decrease. The results obtained from the present analysis can provide a reference to research on this topic.

    • A Dynamic Storage Method of Seismic Information Network Data

      2020, 42(4):1043-1048. DOI: 10.3969/j.issn.1000-0844.2020.04.1043

      Abstract (338) HTML (0) PDF 2.02 M (481) Comment (0) Favorites

      Abstract:This study proposed a dynamic storage of seismic information network data to improve the storage efficiency and stability of seismic information network data. First, the hardware part of the dynamic storage system of seismic information network data was designed and analyzed. Then, a dynamic storage system of a distributed big data cluster based on Hadoop was constructed. In this system, multiple storage servers were integrated into a cluster system, and the load of storage servers was balanced to obtain the proportion of performance indicators and comprehensive performance parameters through the weighted formula. Comparative experiments were performed on the proposed system, the high-speed data storage system, and the network coding cloud storage system. Experimental results showed that the dynamic storage system of the seismic information network data had the shortest time and the fastest storage efficiency. The storage stability was high, and no overload problem was detected.

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