Seismic response of flexible cantilever retaining walls with dry backfill

Failure of retaining walls during earthquakes has occurred many times in the past. Although significant progress has been made in analysing the seismic response of rigid gravity type retaining walls, considerable difficulties still exist in the seismic-resistant design of the flexible cantilever type of retaining walls because of the complex nature of the dynamic soil–structure interaction. In this paper the seismic response of cantilever retaining walls with dry backfill is simulated using centrifuge modelling and numerical modelling. It is found that bending moments on the wall increased significantly during an earthquake. After the end of base shaking, the residual moment on the wall was significantly higher than the moment under static loading. The numerical simulation is able to model quite accurately the main characteristics of acceleration, bending moment, and displacement recorded in the centrifuge test.     

2000年汛期河南持续暴雨的天气形势和水汽分析

通过对2000年6月23日－7月15日河南省出现的3次连续3天以上的暴雨，大暴雨过程的降水特征－背景形势，影响系统和水汽条件等方面的分析，揭示了有利于连续性暴雨产生的水汽条件和两种环流背景场。     

门源6.4级、共和7.0级地震前后波速比变化特征

通过来用门源台、湟源台所记录的地震资料，对1986年门源6．4级地震、1990年共和7．0级地震前后进行波速比-时空分析，发现两次地震前后其时间分布形态为持续低值-恢复-发震的现象，空间分布为圆形、椭圆形的异常区，震后异常区消失。     

准噶尔盆地陆东-五彩湾地区石炭系火山岩电性与地震响应特征

勘探实践证实,准噶尔盆地石炭系已成为一套现实勘探层系;陆东-五彩湾地区石炭系火山岩体规模大、分布广,是重要的天然气储集体;火山岩储层有效性主要受不整合、岩性、岩相控制,识别火山结构、火山岩岩性、岩相成为判别储层有效性的关键.由于主要目的层巴塔玛依内山组特殊的三段式火山岩组合层序结构,为通过测井、地震物探手段识别火山岩岩...     

地震火山地层学及其在我国火山岩盆地中的应用

火山地层,物源来自于地下,搬运和分散方式有岩浆流、碎屑流、空落堆积及它们的再搬运,是不同于所有沉积地层的"异化地层".与层序地层学研究沉积地层类似,火山地层学着重研究火山岩系的层序界面和内部充填样式,通过地震层序分析刻画成因地层单元和地层对比关系.应用地震火山地层学在南海北部陆缘带识别出向海倾斜反射(SDR)、向陆流、...     

全国地下水超采区现状与治理对策

地下水超采问题是我国当前资源、生态保护面临的主要问题之一。本文分析了全国地下水开发利用现状和存在问题，提出了加强地下水保护和超采区治理的对策和建议。     

Electromagnetic Abnormity Observed at Sujiatun Seismic Station and Its Relation to Earthquake

INTRODUCTIONShort-termearthquake prediction is one of the most challenging targets in earth science today.Manyrecent reports have presented examples fromseveral regions of the world by which associationsbetween possible electromagnetic precursors and earthquakes become more and more plausible(Eftaxias ,et al .,2003) . At the same time ,electromagnetic abnormity,as one of the short-termearthquake precursors ,is recognized by more and more experts in some countries . Pre-earthquakeelectroma…     

Assessment of liquefaction potential based on peak ground motion parameters

Conventionally, evaluation of liquefaction potential of loose saturated cohesionless deposits as specified in Japanese design codes employs peak ground acceleration (PGA). However, recent large-scale earthquakes in Japan revealed that liquefaction at some sites did not occur even though large PGAs were recorded at or near these sites. As an alternative approach, an evaluation procedure based on peak ground motion parameters, i.e. incorporating both PGA and the peak ground velocity (PGV), is proposed. By performing parametric studies using one-dimensional seismic response analysis and formulating regression models, seismic-induced shear stresses within the deposit are expressed in terms of peak ground motion parameters at the surface, and these are used to calculate the factor of safety against liquefaction. Application to case histories in Japan indicates that the proposed two-parameter equation can adequately account for the occurrence and non-occurrence of liquefaction at various sites as compared to the conventional PGA-based approach. Moreover, analyses of several strong motion records at various sites show that liquefaction may occur when PGA≥150 gal and PGV≥20 kine, indicating that these values can serve as thresholds in assessing the possible occurrence of liquefaction.     

1987年寻乌地震前的地震活动性异常特征及其相关讨论

利用“八五”，“九五”地震预报攻关研究的成果。对1987年寻乌Ms5.5级地震前的地震活动性异常特征进行了再研究。结果表明，此次地震前出现小震活动空区，地震活动“增强-平静”，前兆性震群活动等多项明显的地震活动性异常。这些异常还表现出一些中期向短期过渡的特征。对将来主震的中短期预测具有一定的参考价值。