Superintend by：China Earthquake Adiministration
Sponsored by：Lanzhou Institute of Seismology, CEA
Tsinghua University
China Civil Engineering Society Seismological Society of China
Edited by：Editorial Board of China Earthquake Engineering Journal
Editor-in-Chief：SHI Yucheng
Address：450 Donggang West Road, Lanzhou, Gansu, China
Post Code：730000
Tel：0931-8275892
Email：dzgcxb2021@163.com
dzgcxb@gsdzj.gov.cn
dzgcxbtg@163.com
ISSN 1000-0844
CN 62-1048/P
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Seismic vulnerability analysis of assembled piers with a hybrid connection
LIN Shangshun, LI Liangyong, YE Shiji, CHEN Zhixiong, ZHAO Jinbing
2024(2):251-258, DOI: 10.20000/j.1000-0844.20220808005
Abstract:
Based on the quasi-static test phenomenon and the test results of an integral cast-in-place pier specimen (ZT-1), a cast-in-place ultrahigh performance mortar-concrete-filled steel tube (CFST) pier specimen with a mortise-tenon connection (GX-1), and a grouting sleeve-CFST pier specimen with a mortise-tenon connection (GT-1), a time-history analysis of these specimens under an earthquake was conducted using the finite element analysis software OpenSees. The vulnerability of the specimens under an earthquake was analyzed by determining the corresponding damage quantification index. The research results show that (1) the change trend of the vulnerability curve of GT-1 is close to those of ZT-1 and GX-1 under slight and moderate damage; (2) when the PGAs are 0.15g, 0.2g, 0.3g, and 0.4g, the seismic responses of GX-1 and ZT-1 are close, and the exceeding probability of severe damage to GT-1 is reduced by 6.71%, 11.67%, 10.32%, and 4.46%, respectively, compared with ZT-1. (3) GT-1 has better collapse resistance than ZT-1 and GX-1.
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Parameter determination and shear characteristics of lacustrine sedimentary peat soil in Dianchi Lake
RUAN Yongfen, CAI Si, LI Rongyu, CHENG Yun, QIAO Wenjian, CAI Long
2024(2):259-268, DOI: 10.20000/j.1000-0844.2021122500x
Abstract:
Organic matter content (wu) and water content (ω) greatly influence the mechanical properties and engineering characteristics of peat and peaty soil (peat soil for short). However, the determination standards of ω and wu of soil with high organic matter content are unclear in existing codes, procedures, and standards, and the test results vary greatly among different units. To define the determination standards of ω and wu of high organic content soil, tests were performed under different burning temperatures and burning times. Generally, the site of lacustrine sedimentary soil in Dianchi Lake has 3-5 layers of peat soil. To explore the variation law and evolution mechanism of stress and strain under different buried depths and confining pressures, a series of triaxial consolidation undrained (CU) tests was performed on five layers of peat soil with different buried depths under low to high confining pressures. The test results show that the stress-strain curve of peat soil presents a “layered” phenomenon with increasing confining pressure; the strain corresponding to the maximum deviatoric stress decreases with increasing depth, and the curve shape changes with the confining pressure and buried depth of soil samples; the pore pressure coefficient decreases with increasing depth. Moreover, the control standard of failure strain of peat soil in the CU test is proposed. This research further deepens the understanding of the mechanical properties of peat soil and provides an experimental basis for determining ω and wu standards.
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RBF neural network prediction model for steel bar corrosion depth under general atmospheric environment
WANG Shengli, LIU Hua, ZHENG Shansuo, DONG Shuqing, HUANG Yu
2024(2):269-277, DOI: 10.20000/j.1000-0844.20211224005
Abstract:
The prediction of steel bar corrosion depth is the basis for evaluating the service performance of RC structures. To establish a prediction model for steel bar corrosion depth in RC members under general atmospheric environment, the main parameters affecting the corrosion depth and the influence law were analyzed in this paper. Then, a numerical model and a RBF neural network prediction model were established based on the measured data, and the parameter sensitivity analysis was carried out. Results show that: compared with the numerical model, the RBF neural network has higher efficiency and accuracy in predicting the corrosion depth of steel bars; it can effectively map the complex nonlinear relationship between the influencing parameters and the corrosion depth of steel bars. The results of parameter sensitivity analysis show that the expansive crack width on RC surface has the greatest influence on the corrosion depth of steel bars, followed by other factors, i.e., the diameter of steel bar, the ratio of concrete cover thickness to steel bar diameter, and the compressive strength of concrete. The proposed model can be used to predict the corrosion degree of steel bars and evaluate the remaining service life of RC structures in engineering detection.
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Construction and application of a database management system for seismic landslides and strong motion records in the Loess Plateau
LI Xiaobo, ZHOU Xinghao, BO Jingshan, HUANG Meng, OUYANG Ganglei, YAN Lingyong
2024(2):278-285, DOI: 10.20000/j.1000-0844.20230105004
Abstract:
Seismic landslide data and actual strong motion records are essential data for seismic landslide mechanism research. How to manage these data scientifically and give full play to their scientific value remains a question worth exploring. In this paper, based on the loess landslides induced by seven typical historical earthquakes and the strong motion records of 125 earthquakes from 2001 to 2018 in the Loess Plateau region, a database management system for earthquake landslides and strong motion records in the Loess Plateau was constructed relying on the open-source GIS platform + MySQL database. With a standard and friendly interface and a clear and smooth graphical presentation, the system parameters are easy to obtain. The system not only provides a scientific and convenient platform for managing and applying seismic landslides and strong motion records data but also provides a solid database for studying the mechanism of seismic landslides in the Loess Plateau, so it has a certain reference value for disaster prevention and mitigation work in this region.
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Simulation test of the magnetorheological grease isolation under reverse demagnetization
ZHOU Yadong, GE Aidi, FU Xiaoman, ZHANG Yan, ZHANG Heng
2024(2):286-293, DOI: 10.20000/j.1000-0844.20220912001
Abstract:
Electromagnetic coils and permanent magnets were used to independently design a magnetorheological grease (MRG) shear test device with reverse demagnetization to jointly control the magnetic field. ANSYS Electronics was employed to simulate and analyze the magnetic field distribution of the test device, and MRG with different mass fractions of carbonyl iron powder was prepared. The shaking table test was performed to evaluate the dynamic shear properties of MRG under reverse demagnetization. The effects of field current, excitation amplitude, and excitation frequency on the dynamic performance of MRG were also investigated. Results show that the mass fraction of carbonyl iron powder has a considerable impact on the dynamic performance of MRG. With the increase in the field current, the shear stress of MRG rapidly increases and then slightly subsides, and the damping force decreases. The energy dissipation capacity of MRG increases with the displacement amplitude, while the damping force slightly increases with the loading frequency.
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Period reduction coefficient of isolation structures based on the equivalent linearization method
ZHANG Longfei, SHU Rui, ZHOU Yanmin, GUO Pingzong
2024(2):294-301, DOI: 10.20000/j.1000-0844.20221227001
Abstract:
The isolation design method, which is proposed in the Standard for Seismic Isolation Design of Building, is an integrated design method based on the equivalent linearization of the complex mode decomposition response spectrum. However, this method does not specify how to determine the period reduction coefficient of the isolation structure. Therefore, according to the stiffness series relationship, a simplified calculation formula for the period reduction coefficient of the equivalent single-degree-of-freedom isolation system was derived, and the influencing factors of the period reduction coefficient of isolation structures were discussed in this paper. Numerical finite element models with different filling materials and rates were established, and the accuracy of the simplified formula was verified. Results show that a functional relationship exists between the period reduction coefficient of the isolation structure, the nominal period ratio, and the period reduction coefficient of the non-isolation structure. As the filling rate increases, the period reduction coefficient of the isolation structure decreases. For the same filling rate, the period reduction coefficient of the isolated structure decreases with the increase in the elastic modulus of the filling materials and increases with the wall opening. The range of the period reduction coefficient of the isolation structure is 0.915-0.965. The deviation between the numerical simulation and theoretical analysis results is less than 3%, thereby proving the accuracy of the simplified formula. The simplified calculation method of the period reduction coefficient has a certain guiding importance for the design of isolation engineering.
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Seismic performance of shape memory alloy concrete frame buildings
2024(2):302-308, DOI: 10.20000/j.1000-0844.20230512001
Abstract:
The earthquake action causes planar and vertical deformation of reinforced concrete (RC) frames, increasing seismic forces on the structure and elevating the damage level. Shape memory alloy (SMA) materials quickly restore the shape before deformation under external forces, reduce the degree of frame damage, and further improve the load-bearing capacity and stability of the frame structure. On this basis, the seismic performance of SMA concrete frame buildings was studied. Taking an actual project as an example, a finite element model of an RC frame structure was established using ANSYS software. Tianjin, Beiling, Indian Ocean, and artificial seismic waves were selected as ground motion input, and the time-history analysis results under these seismic waves were recorded. The research results show that the hysteretic curve of the structure under earthquake action has a full flag shape. The maximum inter-story displacement is 1/125, the residual deformation is within ±10 mm, the maximum peak load is 211 kN, and the horizontal bearing capacity is strong. These results show that an SMA-supported frame has high self-resetting performance, an excellent seismic response effect, and a strong seismic bearing capacity; thus, it can effectively improve the safety and reliability of a building structure.
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Seismic strengthening of high-rise buildings based on the seismic vulnerability from incremental dynamic analysis
2024(2):309-317, DOI: 10.20000/j.1000-0844.2023030700
Abstract:
Because load-bearing structural members are unevenly distributed in high-rise buildings, the distance between these members is unequal. This irregular distribution may cause the acceleration resonance effect during earthquakes, resulting in building instability. In this paper, the seismic retrofit of high-rise structures was studied on the basis of incremental dynamic analysis using parameters such as seismic intensity, peak ground velocity, and the maximum story drift ratio. A 3D model of an actual high-rise building was constructed using ABAQUS software, and multiple seismic waves and ground motion records were selected to validate the seismic vulnerability curve. The results show that installing dampers in the high-rise structure improves the bearing capacity of components and enhances the seismic performance of the building. Increasing the thickness of steel plates improves the seismic resistance of the structure and reduces the exceeding probability of IO, LS, and CP of the frame structure in the limit state. Increasing the strength of concrete improves the anticollapse performance of the frame structure. After seismic retrofitting, the seismic capacity of the high-rise structure improves from 0.91 to 1.01. This study proves that strengthening and perfecting the vulnerable areas of buildings based on a seismic vulnerability analysis improves the seismic vulnerability of high-rise structures and reduces the loss of earthquake disasters.
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Fragility analysis of the concrete gravity dam under the oblique incidence of SV waves
LIU Jinfang, YIN Xiaoxia, GAO Feng
2024(2):318-324, DOI: 10.20000/j.1000-0844.20221024001
Abstract:
An effective method for evaluating the damage probability of concrete gravity dams under ground motions with different intensities is fragility analysis. The fragility analysis of gravity dams generally assumes that seismic waves are vertically incident, but those in the near-fault area are obliquely incident. The oblique incidence of seismic waves has a considerable influence on the seismic response of gravity dams. Based on the database of the Pacific Earthquake Engineering Research Center, 16 ground motion records were selected, and the oblique incidence input of SV waves was realized using the viscoelastic artificial boundary and equivalent nodal load. The PGA of ground motion was modulated using the incremental dynamic analysis method. The Koyna concrete gravity dam in India was taken as the research object in this paper. The fragility curves for different earthquake damage levels of the gravity dam under the oblique incidence of SV waves were established by taking the relative displacement of the dam crest as the seismic performance index. Results show that under the same earthquake damage level and ground motion intensity, the damage probability of gravity dams under the oblique incidence of SV waves decreases compared to that under the vertical incidence. When the PGA is close to the actual earthquake intensity of gravity dams, the maximum reduction rates of failure probability are 27.3% and 68.2%, respectively, when the incident angles are 15° and 30°, compared with that under vertical incidence. Meanwhile, the maximum difference values of failure probability are 36.6% and 83.9% compared with those under vertical incidence. Therefore, the influence of the oblique incidence of seismic waves should be considered in the seismic performance analysis of concrete gravity dams. The results can also provide a reference for the safety risk assessment of concrete gravity dams in near-fault areas.
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Dynamic characteristics of saturated soil foundations based on the strain gradient nonlocal Biot theory
HUANG Zhigang, XU Zhihua, DING Haibin, TONG Lihong, XU Changjie, LEI Zuxiang
2024(2):325-334, DOI: 10.20000/j.1000-0844.20220524001
Abstract:
This paper explores the influences of the pore size effect (represented by a nonlocal parameter) and the heterogeneous effect of the medium (represented by a size factor) on the dynamic response of saturated soil foundations. Based on the strain gradient nonlocal Biot theory, the calculation program for the dynamic response of a saturated soil foundation subjected to cyclic load was compiled using the meshless method. Therefore, the accuracy of the meshless method program was verified. Results indicate that the responses of displacement and pore pressure at observation points are delayed with the increase in nonlocal parameters, maintaining the scale factor as constant. By contrast, the responses are advanced with the increase in the scale factor, maintaining the nonlocal parameter as constant. This finding indicates that the macro-modulus of the system will be decreased considering the pore size effect, which will be increased considering the heterogeneous effect of soil structures. Methods and ideas for solving dynamic problems of saturated soil using the proposed meshless method in this paper could provide references for future research on similar problems.
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Seismic response characteristics of the gypsum-salt layer in the Zhouchongcun Formation of the Wuwei Basin and its petroleum geological significance
I Shangxing, TAN Jing, YU Bingliang, XIONG Qiangqing, YUAN Xingfu, WU Tong, WANG Yuling, ZHENG Xuejing, CHEN Jie
2024(2):335-342, DOI: 10.20000/j.1000-0844.20221012001
Abstract:
The gypsum-salt layer, as the main cap rock of oil and gas fields, is of considerable importance for the sealing of oil and gas reservoirs. On the basis of a 2D seismic exploration in Wuwei Basin, the seismic response characteristics and spatial distribution regularity of the gypsum-salt layer in Zhouchongcun Formation were analyzed using the integrated analysis method of well logs and seismic data. Results indicate a certain positive correlation between the thickness of the gypsum-salt layer and the seismic amplitude attribute. A thick gypsum-salt layer leads to a strong seismic amplitude. The thickness of the gypsum-salt layer varies from 45 to 540 m in the longitudinal direction. Horizontally, the gypsum-salt layer is relatively thick in the core and depression areas of the basin, and the main part is between 300 and 500 m. The gypsum-salt layer is relatively thin in the structurally high position of the basin, and the main body is between 50 and 150 m. The distribution characteristics of the gypsum-salt layer generally show that the low tectonic position corresponds to a thick gypsum-salt layer, and the high tectonic position corresponds to a thin gypsum-salt layer. This study provides a technical guarantee for the breakthrough of natural and shale gas exploration in the Wuwei Basin.
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Dynamic fuzzy reliability analysis of collapse accumulation slopes under bidirectional earthquakes
TONG Xiaojin, TANG Jianzheng, FU Yanqing, CHEN Xunlong, SHU Suxun
2024(2):343-348, DOI: 10.20000/j.1000-0844.20220617003
Abstract:
A dynamic fuzzy analysis method for the seismic reliability of collapse accumulation slopes was established, considering the randomness and fuzziness of parameters for rock and soil in collapse accumulation slopes and the excitation of bidirectional earthquakes. Furthermore, the influence of vertical earthquake excitation on the reliability of the collapse accumulation slope was analyzed. First, the dynamic time-history analysis of FEM was used to calculate the dynamic response of collapse accumulation slope under bidirectional earthquakes, and the strength parameters of rock and soil mass were processed using fuzzy theory. Based on the Mohr-Coulomb strength criterion, the time-history calculation model for the safety factor and reliability of the slope under an earthquake was then established. Finally, a new method for evaluating the seismic reliability of slope was adopted, and the corresponding program was compiled by MATLAB to realize the rapid output of calculation and analysis results. The calculation results of the proposed method are reasonable and safe for engineering. The vertical earthquake has an impact on the reliability of the collapse accumulation slope, but the degree of impact must be analyzed in accordance with the actual situation. For the working condition of the example, the vertical earthquake slightly influences the reliability of the collapse accumulation slope, which only reduces the reliability by 3.55%. Therefore, the influence of a vertical earthquake can be overlooked in this example, and only the influence of a horizontal earthquake should be considered.
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Mechanical properties of fly ash-modified loess reinforced by geogrid
WANG Lili, XIE Wanli, ZHONG Xiumei, LI Xudong
2024(2):349-357, DOI: 10.20000/j.1000-0844.20231008001
Abstract:
With the acceleration of urbanization in the loess region of western China, construction land with fill and excavation is abundant and requires the corresponding foundation treatment technology to solve the problem of large deformation in the filling area. In this paper, fly ash and geogrid were used as modified fillers to improve loess. Through the direct shear, triaxial, collapsibility, and scanning electron microscopy tests, the strength change rule, macroscopic damage characteristics, and microstructure characteristics of reinforced and unreinforced loess specimens with different mixing ratios of fly ash were analyzed. The results show that the optimum water content and maximum dry density of the fly ash-modified loess reinforced by geogrid increases and decreases, respectively. When the mixing ratio of fly ash is 20%, the reinforced improvement effect is the best: The peak strength, residual strength, and equivalent internal friction angle of loess are greatly improved, and the lateral deformation and collapsibility are greatly reduced. Scanning electron microscopy test results show that the improvement of loess by fly ash is mainly reflected in the direct filling of loess pores by fly ash particles and the interweaving of chemical crystals to form a network filling; the porosity and pore size of loess decrease after the improvement. The study results provide a reference for improving and reinforcing fill slopes and fill roadbeds in loess areas.
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Typical damage and seismic vulnerability of brick-concrete structural buildings in south Sichuan
ZHANG Ying, GUO Hongmei, YIN Wengang, ZHAO Zhen, HE Zonghang, HUANG Wentao
2024(2):358-368, DOI: 10.20000/j.1000-0844.20220823001
Abstract:
This paper takes brick-concrete structural buildings with local construction mode characteristics in the south Sichuan area as the research object. The typical damage characteristics of brick-concrete structures were analyzed based on the construction characteristics of brick-concrete structural houses and the investigation results of historical earthquake damage in south Sichuan, such as the Changning M6.0 earthquake. The proportion of different damage levels under different intensities was calculated, and empirical analysis was used to obtain the preliminary vulnerability matrix. However, the actual vulnerability matrix was lacking due to the incomplete damage ratio of structures under high intensity caused by the sample limitation. Therefore, using the interpolation method, the empirical vulnerability matrix was supplemented to calculate the damage ratio under high intensity, and then the vulnerability curve was fitted. Thus, the vulnerability analysis model of brick-concrete structures, which was mainly based on seismic damage statistics and supplemented by numerical simulation, was established. The comparative analysis of the average seismic damage index facilitated testing the reliability of vulnerability analysis. Results show that the constructed vulnerability matrix can objectively reflect the seismic capacity of brick-concrete buildings in south Sichuan. This matrix also has practical application value for conducting seismic damage prediction, disaster loss assessment, and seismic damage risk assessment and prevention.
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Shaking table tests on the liquefaction resistance of tire-reinforced sand cushions
LI Bowen, LU Yang, LIU Sihong, SHEN Chaomin, FANG Binxin
2024(2):369-375, DOI: 10.20000/j.1000-0844.20220430001
Abstract:
Waste rubber tires are filled with bulk materials to form reinforced earth structures, which have been applied to soil foundations, retaining walls, and guard reinforcement projects, showing an obvious effect on vibration isolation. However, few studies have addressed the liquefaction resistance of tire-reinforced soil. Three groups of small shaking table tests were performed to verify the liquefaction resistance of tire-reinforced sand cushions by changing the drainage conditions of the tire cushion. The results show that tire-reinforced sand cushions have a good liquefaction resistance effect. Compared with a rigid cushion, the differences in the peak excess pore pressure ratio and residual excess pore pressure ratio range between 0.01-0.19 and 0.08-0.16, respectively. The drainage channels provided by tire-reinforced sand cushions inhibit the development of excess pore water pressure and accelerate the dissipation of excess pore water. Pore water is discharged along the interface between the tires and the soil below and the drain channels between the tires. The quantitative index of the soil liquefaction degree is defined by measuring lateral earth pressure, further verifying the liquefaction resistance of tire-reinforced sand cushions. During the vibration process, the tire-reinforced sand cushions have a surface settlement range of 11.3-15.7 mm, showing good deformation coordination performance.
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Shaking table tests on the liquefaction characteristics of saturated sand
ZHAO Xuan, MA Shuzhi, MA Shuo, WEN Sheng'ao
2024(2):376-387, DOI: 10.20000/j.1000-0844.20220406001
Abstract:
In this paper, six sand models with three groups of various mean particle sizes and three groups of various fine contents were prepared based on the earthquake simulation shaking table test. Sensors embedded in the sand were used to monitor the excess pore water pressure at different positions in the model, and the time-history curves of excess pore water pressure and pressure ratio in the models were analyzed. Furthermore, the effects of some factors, such as the peak value of seismic wave loading, mean particle size of sand, fines content, and buried depth, on the liquefaction characteristics of saturated sand were summarized. Test results show that the liquefaction degree and potential of sand models gradually increase with the peak value of seismic wave loading, and the liquefaction resistance slowly decreases. With the increase in the buried depth, fines content, and average particle size of sand, the liquefaction degree and potential of sand models also gradually decrease, and its liquefaction resistance gradually increases. The results reveal that the influence degree of various influencing factors on sand liquefaction is seismic wave strength ＞ buried depth of sand ＞ mean particle size and fines content of sand. The test results can help support the parameter selection of subsequent numerical simulations and provide a reference for studying the influence of other factors on sand liquefaction.
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Reinforcement design of the earthen site slope for rural houses in the high loess slope of Kashgar, Xinjiang, under earthquake based on deformation control
ZHANG Yichi, LIU Jian, YANG Guang
2024(2):388-398, DOI: 10.20000/j.1000-0844.20230207001
Abstract:
To verify the effectiveness of strengthening the earthen site slope under earthquake, we considered the existing reinforced section of the earthen site slope in the high loess slope of Kashgar, Xinjiang, as the research object. A three-dimensional dynamic analysis model was established using the finite\|element software Midas/GTX NX,and analysis was performed on the deformation control of the earthen site slope reinforced by lattice anchor retaining wall under earthquake. Results indicate the severe displacement and deformation at the top and foot of the slope,the cumulative effect of the increase in earthquake duration. The displacement and deformation in the horizontal and vertical directions were effectively controlled after reinforcement,and the maximum deformation value met the requirements of control. The stability coefficient of the earthen site slope under earthquake reached 1.54 after reinforcement,which meets the requirement value of 1.15 in the code. The research demonstrates that the lattice anchor retaining wall can effectively control the displacement and deformation of the earthen site slope,thus improving slope stability.
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Seismic responses of the super-high head ship lock based on different water simulation methods with oblique incidence of SV waves
LIU Liqiao, CAO Zhouhong, SU Ying, LI Xian, YUAN Ao
2024(2):399-409, DOI: 10.20000/j.1000-0844.20221027001
Abstract:
The plane SV waves at different angles were simulated based on the input method of obliquely incident ground motion with a viscoelastic artificial boundary. The water inside the lock chamber was simulated using the acoustic-structure coupling and additional mass methods to investigate the seismic responses of the super-high head ship lock, such as displacement, stress, and plastic damage. The similarities and differences in the calculation results of the two methods were compared and analyzed. Results reveal that (1) the variation law of the seismic responses of the left and right lock walls calculated using the two methods with the incident angle is the same. The maximum tensile damage of the left lock wall emerges when the angle of incidence is 15°, and that of the right lock wall appears when the angle of incidence is 35°. The incident angle of a seismic wave has a considerable influence on the dynamic response of super-high head ship locks. Therefore, the design process should consider the influence of the oblique incidence of seismic waves. (2) When the angle of incidence is large, the extreme values of relative displacement and principal stress and the tensile damage results of the lock walls calculated by the acoustic-structure coupling method are relatively larger than the additional mass method, which is safer for the lock design. (3) The two calculation methods are recommended for cross-referencing and calibration, and the safety result is endorsed for the design of super-high head ship locks.
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Reasonable stiffness of the spring components of the damping anchor head for the anchor cable frame considering permanent displacement
ZHANG Tong, JIANG Liangwei, YANG Yun, GE Xuejun, ZHANG Hanwen, YI Mengbi
2024(2):410-420, DOI: 10.20000/j.1000-0844.20220419001
Abstract:
Under the action of a strong earthquake, dynamic damages, such as the pullout of the inner anchor section and the abruption of the anchor cable, are induced by the prestressed anchor cable frame. A novel anti-seismic measure involves setting springs at the outer anchor head, and an important design parameter is the spring stiffness. The seismic responses of slope under various PGAs and seismic waves with different durations were studied using a three-dimensional numerical model of bedrock-overburden slope reinforced by a prestressed anchor cable frame with springs at the anchor head. A method for determining the reasonable stiffness of spring components was proposed to control the displacement of the slope and reduce the load on the anchor cable. Results show that the damping effect gradually emerges with a decrease in spring stiffness. The horizontal acceleration at the top of the slope is slightly affected by the stiffness change. However, the slope displacement and spring deformation sharply increase when the spring stiffness is lower than the critical value. The minimum stiffness is determined by taking the empirical limit of slope permanent displacement as the primary control condition and combining the “straight-curved boundary point” of the fitting curve of spring peak stroke and stiffness. The permanent displacement of 10 cm and delimit curvature k less than 0.002kmax are taken for the calculation model to obtain a reasonable range of spring stiffness, i.e., (2.5, 3.8) kN/mm, under 0.4g-0.6g. The proposed method can provide a reference for the seismic design of prestressed anchorage engineering of slopes.
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Seismic response of the basin considering the effect of soil nonlinearity and dip angle
DING Xin, YU Yanyan, DING Haiping
2024(2):421-430, DOI: 10.20000/j.1000-0844.20221107003
Abstract:
Considering a 2D sedimentary basin model, the D-P elastoplastic model was used to simulate the nonlinear characteristics of the basin. Combining the explicit finite element method with the viscoelastic boundary method and changing the dip angle of the basin edge, the seismic response of the basin surface was analyzed in time and frequency domains, and the difference between linear and nonlinear seismic responses of the basin was compared. The following results are presented: (1) The influence of soil nonlinearity on ground motion in the entire basin is observed. Only considering the nonlinearity, the amplification factor of ground motion is reduced by 30%-50%. Meanwhile, considering the influence of nonlinearity and dip angle, as well as the range and position of areas with the strongest amplification change, the distribution characteristics under considerably small dip angles are different. (2) The amplification factors of the two components tend to increase with the edge dip angle, but the basin edge area is most affected by the nonlinearity. In addition, under the input of a real seismic wave, the range of significant amplification area and the difference between linear and nonlinear results are relatively large. (3) Considering the nonlinearity, the amplification factors of seismic waves with various frequencies are different. However, the distribution of the spectral ratio from low to high frequency is increasingly complex, and the influence of the basin dip angle becomes evident with the increase in frequency. (4) Considering the nonlinearity of soil, the overall characteristics of seismic wave propagation are maintained, but the strength of each seismic phase is reduced.
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Overview of the earthquake monitoring status in the United States
Lü Shuai, FANG Lihua, REN Huayu, ZHOU Benwei
2024(2):431-448, DOI: 10.20000/j.1000-0844.20230802001
Abstract:
The earthquake monitoring work in the United States started early and has enjoyed a leading position in the fields of network design, equipment development, software development, standard formulation, data management, and new technology application. In recent years, earthquake data products in the United States have achieved a leap from singularity to diversification and customization with the development of mobile Internet and the advancement of projects, such as strong earthquake observation, earthquake early warning, and large-scale seismic arrays. Although the earthquake monitoring work in China started late, with the implementation of a series of major projects in recent years, such as the national seismic intensity rapid reporting and early warning, the “Belt and Road” seismic monitoring network, and the China seismic experimental site, the seismic network density, monitoring and early warning ability, intelligent processing of seismic data, service level, and application of new technologies in China have all made great progress. This paper introduces the progress of earthquake monitoring in the United States from five aspects: earthquake monitoring architecture, seismic network layout, data processing system, earthquake warning system, and data products, to better understand the current situation of international earthquake monitoring. Then, a comparative analysis is conducted with the current earthquake monitoring efforts in China. The study results can provide a reference for the further planning and development of earthquake monitoring and early warning in China.
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Seismology-based ground motion attenuation relationship in the Tianshan area
LI Wenqian, RAN Huimin, ZHAO Ruisheng
2024(2):449-456, DOI: 10.20000/j.1000-0844.20221025002
Abstract:
A total of 3 171 seismic records with moment magnitude of 3.5-4.5 collected from the Tianshan area were selected in this paper. Using the microgenetic algorithm and by calculating the Fourier amplitude spectrum of the S-wave velocity, five regional crustal medium parameters were obtained: the stress drop Δσ was 182.06 bar, the quality factor parameter Q0 was 444.20, the η value was 0.35, and the geometric attenuation parameters R1 and R2 were 74.30 and 106.59 km, respectively. Based on the five parameters, the Fourier spectrum of acceleration was calculated. Combined with the random phase spectrum, the time history of ground motion with a certain magnitude and epicentral distance was also obtained. Then, the peak acceleration attenuation relationship of regional ground motion was established. Results show that the attenuation relations of far-field ground motions with moment magnitudes of 5 and 6 are in good agreement with the records of strong ground motions. Among the five selected empirical attenuation relationships, the results for the ground motion with a moment magnitude of 5 are the best for its average value, and the standard deviation is the smallest. The far-field results for the attenuation relationship of ground motion with a moment magnitude of 7 are higher than most strong ground motion records.
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Slipping condition and the mode of activation of fractures induced by fluid injection
LIU Dianzhu, WANG Xinyao, WANG Chun
2024(2):457-464, DOI: 10.20000/j.1000-0844.20221117002
Abstract:
To investigate the physical mechanism of fracture activation induced by fluid injection, a series of triaxial injection-driven shear experiments were performed on sandstone cylindrical samples with a single fracture. The slipping conditions and modes of fracture activated by the fluid injection were analyzed. The results show that the initiation of fracture slippage largely depends on the stress state and the roughness characteristics of the fracture surface. Fluid pressure is the main cause of fracture slippage, while the degree of the nonuniform distribution of fluid pressure and the evolution permeability are the secondary causes. The fluid pressurization rate regulates the slipping mode of fracture. While the roughness characteristics of the fracture surface and permeability evolution characteristics are positively correlated with the rate of fracture slippage, they are negatively correlated with the rate of fluid pressurization. Under laboratory conditions, effective normal stress ＞20 MPa and Coulomb rupture stress ＞1.6 MPa will pose a serious threat to fracture stability, which is significant for evaluating the instability of natural faults activated by fluid injection.
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Anomalous characteristics of the dominant azimuth of geoelectric fields at some stations in the Sichuan region before earthquakes
LIAO Xiaofeng, WANG Weiming, YANG Xing, HE Chang, LI Xuehao
2024(2):465-472, DOI: 10.20000/j.1000-0844.20230116001
Abstract:
The anomalous characteristics of azimuth change were analyzed with earthquake cases using the geoelectric field dominant azimuth method to calculate the geoelectric field data of Jiangyou, Yanyuan, and Chengdu stations in Sichuan Province. Several results were obtained. (1) Since April 6, 2019, obvious abnormal changes have occurred in three directions at Jiangyou station, in which the dominant azimuth (Δα) range of two directions has gradually narrowed and that of one direction has increased. (2) Since August 1, 2021, the Δα ranges in five directions at Yanyuan station have decreased gradually. (3) Since March 1, 2021, the Δα range of five directions at Chengdu station has obviously changed, among which the Δα range of four directions has been gradually reduced, and that of one direction has been gradually increased. (4) The case study shows that the dominant azimuth anomalies of the stations have certain indicative significance for moderate-strong earthquakes within 250 km around the stations. The Δα range of the three stations all showed abnormal decreasing characteristics, and the earthquakes occurred about 5 months or even longer after the anomalies. Thus, the geoelectric field dominant azimuth method may show a medium-and long-term indication ability in this area. (5) Furthermore, the abnormal changes observed at three stations before the earthquakes reflect the changes in rock fractures near the sites. As the regional tectonic stress increases, the rock fractures near the station develop, exhibiting an orderly arrangement of structural variation.
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Design and application of a borehole core basic database: a case study of Changshu station
HE Bin, LIU Dongdong, PAN Ying, LI Feng, ZHANG Min, ZHANG Yang
2024(2):473-481, DOI: 10.20000/j.1000-0844.20230109002
Abstract:
This study investigates the key problems in the construction of a borehole core basic database (borehole core test, data processing, and data collection) and proposes a design scheme for the borehole core basic database. Taking the borehole construction at Changshu station in Jiangsu Province as an example, based on the newly issued construction standard (Specification for the Construction of Seismic Station Crust Deformation Station-Part 2: Crust Tilt and Strain Observatory in Borehole), some key works include borehole construction process, core experiment steps, and the development of core data processing and analysis software. The design scheme of the basic database provides detailed research ideas, methods, and examples for the collection and testing of borehole cores. This study fills the gap in terms of identifying new technical indicators in the national borehole standardization construction and provides a reference for the construction of the borehole core basic database in China.
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Design and accuracy analysis of GNSS crustal deformation monitoring system in local areas
WANG Lei, GAO Shuzhao, SHAO Yuping, YUAN Dongdong, GAO Shijian, SONG Cheng
2024(2):482-490, DOI: 10.20000/j.1000-0844.2022110800
Abstract:
This study explores the relationship between shale gas production and crustal deformation, as well as the response of surface deformation to shale gas fracturing, by deploying a remote cross-fault GNSS deformation monitoring system. The system uses static and kinematic measurement methods to collect information on surface deformation, as well as combines multiple positioning modes to improve the reliability of surface displacement signal detection. Furthermore, it uses network communication and a cloud server to realize the automatic transmission of data, remote management of equipment, and kinematic monitoring of each site. Considering the distinguish ability between measurement error and deformation, the measurement accuracy was analyzed in detail. Results of static measurement indicate that the accuracy of single-day baseline solution and PPP static solution can reach 10 mm in both horizontal and vertical components. The kinematic positioning results for the Luding M6.8 Earthquake in Sichuan indicate that the accuracies of RTK, PPK, and PPP kinematic solutions all reached within 10 mm as well. The results of the accuracy analysis demonstrate that the system can well reflect some long-term and transient deformation information on the monitored areas.
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Stress direction change and strong aftershock occurrence after the MS6.0 earthquake in Crete, Greece
2024(2):491-500, DOI: 10.20000/j.1000-0844.20220929001
Abstract:
The focal mechanism of earthquakes is an indicator of the variation of crustal stress, which is directly related to the occurrence of strong earthquakes. To date, no previous study has investigated the indication of focal mechanism change to the occurrence of normal-fault earthquakes with low apparent stress. This paper takes the 2021 MW6.0 earthquake sequence in Crete, Greece, as an example to determine the relationship between stress variation and the occurrence of strong earthquakes by calculating the minimum spatial rotation angle between the earthquake sequence's focal mechanisms and the direction of the regional stress field. The focal mechanisms determined by multiple agencies were used to obtain the central focal mechanism as the focal mechanism of the earthquake, thus ensuring the accuracy of the focal mechanism. Then, the local stress field was determined by the earthquake sequence's accurate focal mechanism. Finally, the spatial rotation angle of the crustal stress field was calculated, and the relationship between the occurrence of strong earthquakes and the variation of the stress field was explored. Results indicate that the spatial rotation angle between the focal mechanism of aftershocks and the direction of the regional stress field is large in the short term after the mainshock, thereby corresponding to the weak seismicity of subsequent earthquakes with small magnitudes. Consequently, the spatial rotation angle decreases, corresponding to the occurrence of three strong aftershocks (MW＞5.0). After that, the spatial rotation angle increases again for a long time, and the magnitude and frequency of the corresponding aftershocks decrease. Using the same 2021 MW6.0 earthquake sequence as an example, the results reveal that the stress direction concentration also exists before the normal-fault earthquakes with low apparent stress. Therefore, this study provides an example for the exploration of earthquake stress precursors.
Earthquake Engineering
Earthquake Research
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Characteristics of the Loess Seismic Subsidence in Qinyin Village, Shiyuan Town, Induced by the Jishishan M6.2 Earthquake
ZHONG Xiumei, HU Xuefeng, JIA Shichao, WANG Yi
DOI: 10.20000/j.1000-0844.20240208002
Abstract:
The Jishishan M6.2 earthquake occurred on December 18, 2023, induced many loess seismic subsidence disasters. Characteristics of the seismic subsidence disaster are obtained through the field investigation of disaster area in Qinyin Village, Shiyuan Town, Jishishan County. Physical parameters characteristics, microstructure characteristics, and seismic subsidence behaviours of the loess in Qinyin Village were studied based on a series of laboratory tests. In addition, the main causes of seismic subsidence disasters were analysed combined with the field survey results. The results show that the loess in the seismic subsidence area of Qinyin Village is cracked and the cracks are developed. The loess layer is destroyed by anti-dip step-shaped seismic cracking. The maximum settlement is approximately 57 cm. The maximum length of the crack is about 300 m, and the maximum width is about 83 cm. The edges of the loess ridge collapses or slides, and the maximum extension length of the collapse is about 100 m. The loess in the seismic subsidence area is loose, the moisture content is relatively high, the micro-trellis pores are developed, and the particles cementation is weak. Thus, the soil conditions for generating seismic subsidence are met. Besides, the thickness of the loess layer in the seismic subsidence area is relatively large, and the equivalent dynamic stress of the earthquake is greater than the critical dynamic stress to produce seismic subsidence of the loess, and the duration and the predominant period of the ground motion is large, which causes a serious seismic subsidence damage in the site.
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Analysis on the process and causes of debris flow in Zhongchuan Township induced by 6.2 earthquake in Jishishan in 2023
Luo Yi, Li Dewen, Jiang Wenliang, Li Linlin, Jiao Qisong, Tian Yunfeng, Li Qiang, Li Yongsheng
DOI: 10.20000/j.1000-0844.20240113004
Abstract:
Strong earthquake can easily induce the debris flow process in mountainous areas, but it needs to be supplemented by necessary geomorphological, geological, hydrological or climatic conditions. The 2023 debris flow in Caotan and Jingtian Village, Zhongchuan Township in Minhe County, Qinghai Province, has attracted much attention due to its severe disaster. Based on the comprehensive investigation of debris-flow gully and its surrounding areas of Caotan village, including the survey of geomorphological and quaternary-geological features, outcrop observation, grain-size and grain-shape analysis of debris flow source and deposits as well remote sensing, the disaster process characteristics, influencing factors and future prevention and control are analyzed and discussed. The erosion/accumulation thickness and its spatial distribution characteristics of debris-flow gully show that the source area is mainly concentrated in the tributary source of the right bank on the upper reaches of Caotan Village. The rich fine sand material in the source area and the traditional irrigation method provide favorable conditions for the trigger of the slump under earthquake-induced vibration; the field investigation shows that the source is mainly supplied by a large number of shallow (2~3m) slumps, and is gradually broken and dispersed during the migration process. The existence of the shallow stable water table and the exposure of the spring water provide continuous supply of water source for the material in the source area, and finally form debris flow. The both longitudinal and transverse profiles of the circulation area of gully in the pre-disasters are complex, there exist a local small reservoirs and gully are blocked by human structures, these increase the paroxysmal and destructive capacity of debris flow. The spatial distribution characteristics of residual debris and mud traces show that the debris flow has typical plug flow characteristics and shows great viscosity. The increasing potential energy eventually led to debris-flow breaking through the valley barrier to continue to flow. Erosion and accumulation coexist along the way, reshaping the debris-flow valley. The topography of the accumulation area is further open, leading to the dispersion and accumulation of debris flows. The intrusion of civil architecture into the valley is one of the causes of the disaster. In addition, the severe cold weather and the midnight occurrence of earthquake, as well as the lack of public awareness of the nature of the disaster, also aggravated the severity of the debris flow disaster to a certain extent. In view of the many small and medium-sized basins in the upper reaches of the Yellow River, with similar stratigraphic structure, landform and hydrological conditions, and similar human settlement environment and human-land relationship, this paper proposes to carry out the investigation step by step in combination with the characteristics of this disaster. On this basis, regular inspections and investigations will be carried out for the identified high-risk and hidden dangers to strengthen the prediction and early warning of major disaster risks. At the same time, add publicity and popularization to improve the public"s scientific awareness of earthquake-induced disasters.
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SIMULATION STUDY OF THE 6.9 MAGNITUDE STRONG GROUND MOTION IN MENYUAN, QINGHAI ON JANUARY 8, 2022
DOI: 10.20000/j.1000-0844.20230920001
Abstract:
In this study, to meet the new requirements of emergency response in the digital age, we developed a method based on the stochastic finite fault modeling. Using the subsurface three-dimensional velocity structure model and vS30 data from the Menyuan region of Qinghai Province, we applied the step by step iterative ray-tracing method, the Green"s function displacement analytical solution of phase spectra and the finite fault method to calculate strong ground motion simulation data with amplification response at the ground surface. Taking the 6.9 magnitude earthquake in Menyuan, Qinghai as an example, we created PGA and intensity distribution simulation maps for the study area. Comparing these simulated results with actual PGA records from monitoring stations and the field intensity survey, we found that the intensity zonation ranges are basically consistent. This process also verified that this method can be utilized for the rapid assessment of future earthquake disasters, thereby providing a reference for the post-disaster emergency rescue.
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Earthquake disaster defense; Risk survey; Service platform; Gansu Province; Three levels of province, city and county
SUN Yanpin, CHEN Wenkai, LI Dagui, MA Yupeng
Abstract:
Gansu is one of the provinces in China with high seismic intensity. Although some achievements and progress have been made in the informatization of earthquake disaster defense in Gansu province in recent years, the technical systems for earthquake disaster defense at the municipal and county levels have still not been established, resulting in problems such as ineffective integration of resources across the province and a low level of data information services. Building on the foundation of the earthquake disaster risk survey work in Gansu Province, this paper aims to construct a comprehensive earthquake disaster defense service platform at the three levels of province, city, and county, integrating the display, query, and services of achievements in earthquake hazard, disaster-bearing bodies, and earthquake disaster risk assessment. The platform facilitates the unified aggregation and service of risk survey results at the provincial, municipal, and county levels. Through various forms such as web pages, maps, statistical charts, etc., the platform provides informatization services for earthquake disaster risk prevention and control throughout the province, maximally meeting the operational needs of earthquake departments at all levels and comprehensively enhancing the seismic damage prevention and control service capabilities across the entire province. Key words：Earthquake disaster defense; Risk survey; Service platform; Gansu Province; Three levels of province, city and county
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Stress change on surrounding faults and stress triggering of aftershocks by 2023 Jishishan Ms 6.2 earthquake in Gansu
Zhou Mingyue, WAN Yongge, GUAN Zhaoxuan, JIN Zhitong
DOI: 10.20000/j.1000-0844.20240101001
Abstract:
On December 18, 2023, an Ms 6.2 earthquake occurred in Jishishan County, Linxia Prefecture, Gansu Province, China. The earthquake was located in the Lajishan fault. To deeply into the static Coulomb stress impact of this earthquake on the surrounding faults and aftershocks, the static Coulomb Failure Stress(CFS) changes induced by the Jishishan Ms6.2 earthquake at various depths along the major surrounding faults are calculated by using elastic half-space medium and the co-seismic rupture model. And the future potential seismic hazard on the study region is estimated based on the CFS changes.The results indicate that the event significantly increased the CFS on segments of the Qinghainanshan-Xunhuananshan fault, Lajishanbeiyuan fault, and Lajishannanyuan fault. Particularly, the eastern segment of the Qinghainanshan-Xunhuananshan fault experienced a CFS increase well beyond the static stress triggering threshold, reaching 0.022 MPa, indicating a potentially higher seismic hazard. Other faults also exhibited various degrees of CFS changes, with stress unloading amounts reaching tens of thousands of Pascals on segments of the Lajishanbeiyuan fault and Lajishannanyuan fault, and hundreds of Pascals on the other segments of Nanshan-Xunhua Nanshan fault in Qinghai except the eastern segment and Zhuanglanghe fault. Furthermore, a comparative analysis of CFS changes on faults at different depths revealed a significant influence of depth variations on the CFS pattern of the earthquake. However, the increase in CFS along the Qinghainanshan-Xunhuananshan fault remains highly significant. This study provides a reference for evaluating the possibility and risk of future earthquakes in study region. Moreover, the CFS changes induced by the earthquake on the fault planes of the larger aftershocks are calculated. The CFS changes on the fault planes of the three subsequent Ms≥4 earthquake are estimated as 0.024 MPa, 0.033 MPa, and 0.034 MPa, respectively, which surpassing the triggering threshold and it shows that the Ms6.2 earthquake has obvious triggering effect on these three earthquakes.
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The Causes and Destructive Effects Analysis of the liquefied earthflow triggered by the 2023 Jishishan Ms 6.2 earthquake, Zhongchuan Township Gansu Province
DOI: 10.20000/j.1000-0844.20240110001
Abstract:
At 23:59 on December 18, 2023,an Ms 6.2 seismic event? struck the Jishishan County in Linxia Prefecture, Gansu Province, triggering numerous geological disasters. Among them, the sand-soil liquefaction mudflow disaster in Zhongchuan Township caused significant economic losses and casualties, and it is urgent to analyse and determine its characteristics, causes and destructiveness. After the earthquake, we went to Zhongchuan Township in Gansu Province, which is the most destructive area of the earthquake, to carry out emergency scientific research, and obtained high-precision and high-resolution digital results of DOM and DSM. Through image interpretation, ground surveys, and on-site inspections, we conducted a comprehensive analysis of the post-earthquake mudflow disaster. The results show that: ① Loess soil, prone to sliding and saturated with water, experienced a rapid increase in pore water pressure under the seismic load, leading to sand-soil liquefaction. This ultimately destabilized and destroyed the soil layer, causing the collapse of the plateau"s edge and seismic landslides. The soil-water mixture, under the influence of gravity, flowed down the slopes and valleys, forming a liquefaction-type landslide-mudflow disaster; ② The disaster phenomenon is not a single mudflow, but the liquefaction of sand and soil led to mudflow and sand-bursting at the same time, the probability of both occurring at the same time is very low, the devastation is very great; ③ This earthquake exemplifies the "small and medium quake, large disaster" scenario, where, despite its moderate magnitude, it caused greater destruction and casualties compared to other earthquakes of similar scale. This geological disaster has both particularity and abnormality.
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Sliding process and causative mechanisms of the Jintian-Caotan landslide-mudflow hazard chain induced by the 2023 Jishishan Earthquake
WANG Liao, XIE Hong, Pu Xiaowu, LI Zhimin, GUO Xiao, YAO Yunsheng
DOI: 10.20000/j.1000-0844.20240113003
Abstract:
At 23：59 on December 18, 2023, a magnitude Ms6.2 earthquake occurred in Jishishan County, Gansu Province. This earthquake triggered a severe landslide-debris flow disaster in Caotan Village, Zhongchuan Town, Minhe County, Qinghai Province. Based on the detailed geological survey, low-altitude photogrammetry, onsite engineering geology mapping, and soil water content experiments, basic characteristics, dynamic development process, as well as causes of the landslide disaster were investigated and analyzed. The results suggest that the landslide initiated in a phased and block-wise manner, undergoing six significant sliding stages. This progression exhibits a characteristic of progressively retreating slip. The analysis suggests that the landslide was predominantly attributed to such composite factors: prolonged irrigation activities undertaken by local inhabitants culminated in the establishment of saturated loess layers beneath the surface. Subsequent to the strong earthquake shaking, the pore water pressure within these saturated loess layers experienced a rapid escalation, inducing a state of liquefaction in the loess.
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Structure design and experiment of ocean bottom cabled seismometer node
ZHANG Chuan, ZHOU Jianping, RUAN Aiguo, WENG Lichun, DUAN Lei, ZENG Jinfeng, CHEN Ningte
DOI: 10.20000/j.1000-0844.20230330001
Abstract:
The ocean bottom seismometer is an important marine seismic observation equipment. In view of the characteristics of high noise of ocean currents and frequent human activities in China"s offshore shallow ocean, the chained seismic observation method is proposed and the mechanical structure of ocean bottom cabled seismometer node is designed. Firstly, the overall structure of node is designed according to the size and layout of the internal components. Then the shell thickness, end cover thickness and sealing size are determined by theoretical calculation and finite element simulation. Finally, the pressure test verifies that the pressure resistance and water tightness of the designed seismometer node structure meet the requirements, and the seismic observation comparison test verifies its ability to receive natural earthquakes. The ocean bottom cabled seismometer will be applied to the actual seismic observation in the offshore area of Zhejiang Province to provide real-time and continuous seismic observation data.
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Finite element analysis of seismic performance of weakened flange connection plate upper welded lower bolted steel beam column
DOI: 10.20000/j.1000-0844.20231011001
Abstract:
Research on the seismic performance of weakened steel beam-column "upper welded and lower bolted" joints with lower flange plate connection plates, providing reference for the design and engineering application of shortened cantilever beam steel beam-column joints. Using the finite element software ABAQUS, based on the consistency between numerical simulation and experimental results, the effects of the weakened length of the lower flange plate connection plate and the cross-sectional shape of the frame beam on the seismic performance of the upper welded and lower bolted steel beam column joints were analyzed. If the weakening length of the lower flange plate connecting plate is too short, it cannot play the role of plastic hinge outward movement. If the weakening length of the lower flange plate connecting plate is too long, it will lead to serious out of plane buckling. The seismic performance of the beam full section weakening group is better than that of the half section weakening group and the unchanged group. Reasonably arranging the length of the weakened area of the lower flange plate connection plate and the cross-sectional shape of the frame beam can effectively improve the seismic performance of the "welded up and bolted down" steel beam column joints.
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Analysis of influencing factors and characteristics of residential housing damage in typical earthquake-stricken areas of Sichuan Basin
PengQiaoqiao, MengXiangrui, DiBaofeng, ZengYajie, LUO Xiaolong, Hu Shunzhong
DOI: 10.20000/j.1000-0844.20230309001
Abstract:
A Ms. (surface wave magnitude)6 .0 earthquake occurred on September 16th, 2021, and affected 18 towns in Luxian County, Sichuan Province with different impacts. Through an on-site survey, we quantitatively analyzed the damage of the earthquake to residential houses in affected areas, assessed relationships among the house structures, epicentral distance, and degree of residential damage. This led to the development of a matrix of residential housing vulnerability to show the earthquake-affected areas in the Sichuan Basin with different intensities. Based on this analysis, the study compared the difference in average earthquake damage indexes between the affected areas and other regions that had previously experienced earthquakes of the same magnitude. In doing so, we were able to identify some of the key characteristics and factors that contributed to the degree of housing damage observed in the study areas. The following results were drawn: (1) housing vulnerability ranked from high to low involving brick-concrete structure, brick-wood and other structures (civil, wood and stone masonry structure), steel-concrete structure; (2) the areas within 6,600 meters from the epicenter experienced 90% of the earthquake damages; (3) earthquakes of similar magnitude cause 1~2 times less damage to residential housing within the Sichuan basin than areas in the mountainous regions. The results herein can be used as scientific references for the rapid assessment of damages, planning, and reconstruction of residential housing in the post-earthquake period in the Sichuan Basin and other settings prone to earthquakes .
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Research on CO anomalies before and after the 2021 Maduo MS7.4 earthquake in Qinghai
SHI Yanfei, XIN Cunlin, LIANG Haodong, LIU Haibo
DOI: 10.20000/j.1000-0844.20230105002
Abstract:
The study of gas geochemical information before and after the earthquake has high application value to monitor and forecast earthquake. In order to understand the relations between the variation of CO and the May 22, 2021 Maduo Ms7.4 earthquake in Qinghai, on the basis of verifying the reliability of Atmospheric InfraRed Sounder (AIRS) date with ground date of Waliguan atmospheric observation station, extract the date of CO from AIRS before and after the Maduo Ms7.4 earthquake, by the sliding mean method and difference method to discuss the relationship between CO changes and seismic activity. The results showed that the extraction of CO geochemical information using satellite remote sensing date is reliable. From the aspect of time, in the first two months of the Maduo Ms7.4 earthquake, the CO concentration gradually increased and recovered to calm after earthquake. From the aspect of space, the CO concentration with particularly obvious changes in the near-surface layer at the epicenter. In March the CO concentration began increase around the epicenter, converged from discrete distribution to the epicenter and seismogenic fault zone in space. The maximun anomaly is 18.60ppbv in the end of April, the center line of the anomalies were consistent with Jiangcuo fault and the distribution of seismic rupture. Excluding the influence of background and seasonal change, inferred the change of CO concentration is caused by earthquake. The abnormal phenomena of CO mainly attributed to underground gases escape, rock compression and collision, and the atmospheric chemical reactions play a secondary role.
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Influence of calcium lignosulfonate on hydrological properties of Lanzhou loess
WANG Shen-li, LI Xiao-long, LIU Chen-lin, LIU Dong-fa
DOI: 10.20000/j.1000-0844.20220418002
Abstract:
To reveal the influence of calcium lignosulfonate on hydrological properties of Lanzhou loess, based on different content of calcium lignosulfonate and age, the water repellency, permeability and water stability are analyzed through tests of water droplet infiltration, permeability and disintegration. And the mechanism of loess improved by calcium lignosulfonate is discussed by tests of X-ray diffraction and scanning electron microscope. The results show that: loess improved by calcium lignosulfonate can improve the water repellency and water stability, which of low content has limited improvement, but which of high content has large improvement. The effect of reducing permeability is limited. The loess improved by calcium lignosulfonate can show age effect in the hydrological properties. At 28 days, there is a generalized peak value in the hydraulic property parameters of loess improved by calcium lignosulfonate with the content, but the relationship between peak value and content is different. The hydrological properties and mechanical properties of loess improved by calcium lignosulfonate maintain a certain positive correlation. Loess improved by calcium lignosulfonate does not produce new mineral components. The thickness of electric double layer becomes thinner, and cementation products wrap particles, bind particles and fill pores, what improve the hydraulic properties.
