Dynamic response of debris flows impacting curved joint check dams     

《国际泥沙研究》2022,37(5):589-600

The dynamic impact force of debris flow on dams with a curved upstream face curved was investigated using laboratory experiments and a theoretical approach. Equations describing the impact force and maximum run-up height were derived. The experiments and theoretical considerations reveal that the impact force and maximum run-up height are mainly controlled by the Froude number (Fr) reduced by the cosine of the channel slope angle (cosα). Both the impact force and the maximum run-up height have a quadratic relation with the modified Froude number (Fr/(cosα)^0.5). The experimental data and the results of the theoretical approach are in good agreement, indicating that the theoretical approach can be used in practical applications. It is concluded that the comparison between the curved-joint dam and the more conventional sharp-joint dam shows no differences in the maximum impact force and run-up height for the same modified Froude number. With the sharp-joint dam, the peak values of the impact force are reached more quickly than with the curved-joint dam.  相似文献   

2022年9月5日四川泸定MS6.8地震舆情分析          下载免费PDF全文

薛杭  赵烽帆  荣华 《中国地震》2022,38(3):425-431

2022年9月5日12时52分,四川省甘孜州泸定县发生 M_S6.8地震,造成重大人员伤亡,引起社会公众的广泛关注。突发事件的信息发布和舆情引导越来越受到党和政府的高度重视,相关信息公开效率的影响甚至决定了事件处置的舆情发展。本研究以中国地震台网中心为舆情引导主体,对四川泸定 M_S6.8地震舆情进行分析研究,总结舆情引导经验,探讨突发地震舆情引导对地震部门有效开展震后应急的促进作用,以期为今后的防震减灾新闻宣传工作带来启示和思考。  相似文献   

Testing a proposed new chronology for the Jasmund Glacitectonic Complex (SW Baltic Sea): No indication of incipient deformation during MIS 3     

《Quaternary Geochronology》2022

Weichselian advances of the Scandinavian Ice Sheet have generated several glacitectonically deformed structures in the southwestern Baltic Sea area. One example is the 100 km² large Jasmund Glacitectonic Complex (JGC), which was formed proglacially and consists of two subparallel-orientated sets of composite ridges that represent a northern and southern structural complex. The two-part morphological structure of the JGC suggests a formation by two ice advances, one approaching from NE and one from SE direction. So far, this divided structure has been assumed to have been formed by short-time ice-front oscillations during an MIS 2 ice advance. However, based on their recently published ice dynamic model for MIS 3 and the available age data from Jasmund, lüthgens et al. (2020) propose a chronological reinterpretation of the JGC development, according to which two distinct ice advances during early and late MIS 3 formed the JGC. In order to test this novel stratigraphical model for the JGC formation, five OSL samples were taken from fluvial and lacustrine deposits at a key section near Glowe (NW Jasmund). The investigated succession is divided into pre-kinematic sediments, deposited before the glacitectonic deformation, and post-kinematic sediments, deposited after the deformation. Our results show that the youngest dated pre-tectonic sediment has a burial age between ∼40 and 34 ka, which rules out a glacitectonic deformation during an early MIS 3 ice advance (∼60–50 ka). In addition, by reviewing the existing age data set, a development of the JGC during an early and late MIS 3 advance of the SIS must be rejected. Instead, our data confirm the genesis of the JGC during MIS 2.  相似文献   

自适应顺序采样Kriging方法及其在增量动力分析中的应用          下载免费PDF全文

焦圣虎  侯和涛  冉德胜  陈城  曾晓真  高梦起  熊方明 《世界地震工程》2022,38(4):218-228

复杂结构的增量动力分析（IDA）对于结构的抗震设计和分析有着重要意义,但需对结构进行大量的非线性时程分析,计算量成本高。本文结合Kriging元模型和自适应顺序采样并用于结构增量动力分析以提高其计算效率和精度,其中:Kriging元模型用于预测结构的地震响应,顺序采样根据候选点的熵值补充非线性时程分析逐步增加Kriging模型的预测精度。借助本文方法,IDA曲线可通过少量的时程分析实现较高的精度。为了校验本文方法的可行性与有效性,对二层和九层钢框架结构模型应用直接IDA、hunt&fill方法和本文方法分析并比较了上述三种方法的计算误差、计算效率和IDA曲线差别。在此基础上本文将自适应顺序采样Kriging方法用于考虑结构不确定性参数的IDA分析,并和传统的蒙特卡洛方法进行比较。结果表明:该方法具有较高的计算效率,可以保证IDA曲线的精度。  相似文献   

基于IDA的层间隔震结构失效模式研究          下载免费PDF全文

李天明  刘德稳  罗晓轩  霍一然  杨忠楠  雷敏 《世界地震工程》2022,38(4):132-142

层间隔震结构是由基础隔震结构发展而来的一种新型隔震结构。为研究层间隔震结构的倒塌,需先研究不同层间隔震结构的不同失效模式和失效位置,文章建立了3个不同结构参数的层间隔震结构有限元模型,选取20条与抗震规范反应谱吻合的地震动,采用增量动力分析（IDA）方法,分别对其失效模式和失效位置进行研究。研究表明:基于不同的结构参数,层间隔震的基本失效模式有三种,即隔震层水平位移超限导致结构失效、下部结构层间位移角超限导致结构失效、隔震层拉压应力超限导致结构失效;隔震层下部结构和隔震层最外边缘支座为结构的薄弱位置,应引起更多关注。此方法不仅可以研究结构的不同失效模式,还可以确定失效位置,可为下一步层间隔震结构的抗倒塌分析提供理论基础。  相似文献   

典型斜坡地形地震动特征分析     

丁佳龙  郝冰  李远东  周港圣  周正华 《震灾防御技术》2022,17(3):473-480

以云南鲁甸6.5级地震中房屋建筑破坏严重的龙头山集镇斜坡地形为例,通过地脉动测试分析得出斜坡及坡顶测点相对于坡脚参考点谱比峰值均＞1,顺坡向谱比峰值大于垂直坡向谱比峰值,且谱比峰值从斜坡坡脚到坡顶逐渐增大,坡顶处约为3;顺坡向谱比峰值对应的频率为4.57～5.39 Hz,垂直坡向谱比峰值对应的频率稍高,为5.42～5.96 Hz。通过结合黏弹性边界的时域动力有限元方法分析斜坡地形在垂直入射地震动作用下的响应,数值模拟结果表明,斜坡坡顶处的位移放大作用显著,坡脚处放大作用较小;介质剪切波速对斜坡地震动的影响较明显,尤其是坡顶点处不同介质剪切波速模型位移峰值差异较大。由于斜坡地形复杂的散射效应,在斜坡及附近测点均出现明显的转换面波,坡顶点处波形转换最显著。数值模拟结果进一步验证了龙头山集镇依坡而建的房屋建筑破坏严重是由局部地形地震动放大效应与地震动差动共同作用引起的。  相似文献   

Revisiting natural and laboratory electron spin resonance (ESR) dose response curves of quartz from Chinese loess     

《Quaternary Geochronology》2022

Natural and laboratory ESR dose response curves (DRCs) of [AlO₄/h]⁰ and [TiO₄/M⁺]⁰ were investigated for samples of quartz from the Luochuan loess-palaeosol master section, Chinese Loess Plateau. The natural and laboratory DRCs show a clear divergence above ∼1000 Gy, with much lower D₀ values and saturation levels observed for the natural DRCs, which is in agreement with the previous study by Tsukamoto et al. (2018). Young (<15 ka) samples from Luochuan and Jingbian – another site of the Chinese Loess Plateau, together with two modern samples of Chinese loess, were used to investigate the residual signals of [AlO₄/h]⁰ and [TiO₄/M⁺]⁰ centres. Our results are in line with published studies and show that the significant residual signals corresponding to several tens to hundreds of Gy are present in both Al and Ti centres. These need to be taken into account before laboratory DRC construction. ESR pulse annealing experiments performed on samples irradiated with different doses show an apparent dose-dependent thermal instability of [AlO₄/h]⁰ and [TiO₄/M⁺]⁰, with the signals for higher doses decaying faster with increasing temperature. We attribute the change in D₀ with preheat reported in Tsukamoto et al.2018, as well as the difference between laboratory and natural DRCs, to this apparent dose-dependent thermal instability of the signals. The saturation level of the natural DRC, being the result of reaching the equilibrium between filling of the traps and emptying them due to thermal decay, is therefore additionally affected at higher doses, due to the increased thermal instability. The inability to recreate in the laboratory the same response to irradiation as the one observed in nature questions the accuracy of dating samples beyond ∼1000 Gy.  相似文献   

Experimental study on the dynamic modulus of compacted loess under bidirectional dynamic load     

Liguo Yang  Shengjun Shao  Qilong Sun  Ping Wang 《地震研究进展（英文）》2022,2(3):100115

The dynamic characteristics of compacted loess are of great significance to the seismic construction of the Loess Plateau area in Northwest China, where earthquakes frequently occur. To study the change in the dynamic modulus of the foundation soil under the combined action of vertical and horizontal earthquakes, a hollow cylindrical torsion shear instrument capable of vibrating in four directions was used to perform two-way coupling of compression and torsion of Xi'an compacted loess under different dry density and deviator stress ratios. The results show that increasing the dry density can improve the initial dynamic compression modulus and initial dynamic shear modulus of compacted loess. With an increase in the deviator stress ratio, the initial dynamic compression modulus increases, to a certain extent, but the initial dynamic shear modulus decreases slightly. The dynamic modulus gradually decreases with the development of dynamic strain and tends to be stable, and the dynamic modulus that reaches the same strain increases with an increasing dry density. At the initial stage of dynamic loading, the attenuation of the dynamic shear modulus with the strain development is faster than that of the dynamic compression modulus. Compared with previous research results, it is determined that the dynamic modulus of loess under bidirectional dynamic loading is lower and the attenuation rate is faster than that under single-direction dynamic loading. The deviator stress ratio has a more obvious effect on the dynamic compression modulus. The increase in the deviator stress ratio can increase the dynamic compression modulus, to a certain extent. However, the deviator stress ratio has almost no effect on the dynamic shear modulus, and can therefore be ignored.  相似文献   

地震动记录选取及其对网架屋盖动力响应的影响          下载免费PDF全文

马风龙  乐风江  王健 《世界地震工程》2022,38(1):090-98

地震动记录的合理选取对预测结构响应有着重要的作用。本文通过对风雨操场建筑混合结构的抗震性能分析,提出了一种对水平及竖向地震动频谱特性均进行控制的改进选波方法。为了评价不同选波方法的可靠性和有效性,根据初选条件选取55组三向地震动记录,并以55组地震动的统计反应谱作为目标反应谱,以55组记录计算的结构响应均值作为"预测值",通过与单周期点和双频段选波方法的计算结果对比,分析表明:改进选波方法计算的结构基底剪力、柱顶位移、支座位移和网架竖向位移的相对误差和变异系数均小于前两种选波方法,其计算结果更加可靠有效。  相似文献   

基础类型对框架结构及场地土地震响应影响试验研究          下载免费PDF全文

王国波  王垚  孙富学  郑年文 《世界地震工程》2022,38(2):096-109

本文设计独立基础框架和整体箱型基础框架结构模型,基于试验数据的对比分析,探讨基础类型与地震动特性对场地土以及结构自身地震响应的影响。试验结果及分析表明:地表结构的存在总体上是放大了地表加速度响应,放大最大幅度达到了40%,影响范围可达3倍的结构跨度,且具有一定埋深的箱型基础的影响大于浅埋独立基础。由于土体对独立基础的约束相对较弱,导致独立基础结构模型的加速度响应总体上大于箱型基础的;独立基础结构模型可能发生摇摆运动导致结构基础竖向响应的频谱特性含有较多的高频成分。另外,地震动特性对结构响应也较显著,其中脉冲地震动NR波的影响最为显著。  相似文献