含初始缺陷地铁隧道的抗震动力学行为研究

针对含初始缺陷的既有地铁隧道受邻近穿越隧道施工影响的首都地铁隧道工程背景,基于有限差分方法,通过对既有地铁车站结构受邻近隧道穿越后的抗震性能研究,揭示其抗震动力响应机理。结果表明,在邻近隧道穿越影响下,含初始缺陷的既有隧道各薄弱控制点在地震作用下位移和应力动力时程的波动趋势具有相似性,说明衬砌结构是整体运动的,其位移、应力较穿越前均有所增加,边墙和仰拱在穿越后抗震性能影响最大,剪切破坏主要以车站结构周边土体为主,新线穿越后其剪切破坏分布范围有所增大,应进行注浆加固处理,与自身结构刚度相匹配,提高抗震能力。     

Deformation fabrics of glaucophane schists and implications for seismic anisotropy: the importance of lattice preferred orientation of phengite

ABSTRACT

Strong seismic anisotropy is observed in many subduction zones. This effect is attributed partly to subducting oceanic crust that is transformed into blueschist facies rocks. Because blueschist facies constituents such as glaucophane, epidote, and phengite show strong anisotropic elasticity, seismic anisotropy in subducting oceanic crust can be attributed to the lattice preferred orientation (LPO) of these minerals. We studied the deformation fabrics and seismic properties of phengite-rich epidote–glaucophane schists from the Franciscan Complex of Ring Mountain, California. The samples are composed mainly of glaucophane, epidote, and phengite. Some samples contain abundant phengite, the maximum being 40%. The LPOs of glaucophane showed that the [001] axes are aligned subparallel to lineation, and both (110) poles and [100] axes are aligned subnormal to foliation. The epidote [001] axes are aligned subnormal to foliation, with both (110) and (010) poles aligned subparallel to lineation. The LPOs of phengite are characterized by the maxima of [001] axes subnormal to foliation, and both (110) and (010) poles and [100] axes are aligned in a girdle subparallel to foliation. The phengite showed substantially strong seismic anisotropy (AV_P = 42%, max.AV_S = 37%). The glaucophane schist with abundant phengite showed significantly stronger seismic anisotropy (AV_P = 30%, max.AV_S = 23%) than the epidote–glaucophane schist (AV_P = 13%, max.AV_S = 9%). When the subduction angle of phengite-rich glaucophane schist is considered, the polarization direction of the fast S-waves for vertically propagating S-waves changed to a nearly trench-parallel direction for the subduction angle of 45?60°, and the S-wave anisotropy became stronger for vertically propagating S-waves with increasing subduction angles. Our data showed that phengite-rich blueschist facies rock can therefore contribute to the strong trench-parallel seismic anisotropy occurring at the subducting oceanic crust and at the slab–mantle interface in many subduction zones.     

覆水砂土场地中桥梁群桩基础地震响应离心试验研究

为探究覆水饱和砂土场地中土-群桩基础-桥梁结构体系动力相互作用规律,自主设计并制作了直（斜）群桩基础-桥梁结构物理相似模型,开展了不同地震动强度和不同特性地震波输入下的离心机振动台试验,分析了群桩基础-桥梁结构动力特性指标,探究了覆水饱和砂土地基超孔隙水压力发展规律和桩-土相互作用动力响应特性。研究结果表明：覆水的存在对地基土-桥梁结构体系的基本周期和阻尼影响很小,但会导致直群桩基础桥梁结构的振动幅值增加20%,而斜群桩基础桥梁结构的振动幅值降低10%;斜群桩基础模型阻尼比是直群桩基础模型的2倍。上覆水导致饱和砂土地基由受低频振动液化深度更大变为受高频振动地基液化深度更大,同时导致小震作用下促进超孔隙水压力发展,而大震作用下则反之。上覆水会增大桥梁上部结构的动力响应和桩身弯矩。上述研究结果可为覆水场地中桥梁工程抗震设计提供关键参考依据。     

基于Tesseral的盲源地震响应恢复影响因素研究

将盲源地震波记录中有用的反射波信号恢复并降低噪声影响,历来是地震勘探数据处理环节中的一个难题.本文利用tesseral软件,通过建立一个典型凹陷模型,对影响盲源地震响应恢复的六个主要因素:自由表面、被动源的震源分布、被动源数目、被动源子波信号的持续时间、震源子波类型和随机噪声的响应特征分别进行研究,研究结果表明,各影响因素对盲源地震响应恢复质量均有一定程度的影响,其中被动源的震源分布情况、能捕获的被动源数目和被动源持续时间这三个因素直接决定了被动源地震响应的恢复质量,能否接收到来自自由地表的多次波,决定了地震响应恢复的可能性.这对实际地震勘探数据处理具有一定的指导意义.     

Crustal structure of Dabieshan orogenic belt

The crustal structures ofP velocity and density on the deep seismic sounding profile across the Ilabieshan orogenic belt are presented. There is a 5-km-thick crustal “root” between the Yuexi and Xiaotian where the elevation is highest on the profile. An apparent Moho offset of 4. 5 km beneath the Xiaotian-Mozitan fault marks the paleo-suture of the Triassic collision. A high-velocity anomaly zone at the depth below 3 km beneath the ultra-high pressure (UHP) zone may be correlated to the higher content of UHP metamorphic rocks. Project supported by the National Natural Science Foundation of China and the Joint Earthquake Science Foundation.     

Pseudo‐dynamic testing with substructuring at the ELSA Laboratory

The paper describes the distinctive features of the pseudo‐dynamic test method as implemented at the ELSA reaction‐wall facility. Both hardware and software aspects are considered. Particular attention is devoted to the digital control system and to a coupled numerical–experimental substructuring technique allowing realistic earthquake testing of very large structures. Mathematical and implementation details corresponding to this testing technique are given for both synchronous and asynchronous input motion. Selected test results illustrate the advantages of the presented features. Copyright © 2000 John Wiley & Sons, Ltd.     

文安Ms5.1级地震前锦州地震台的某些前兆异常

本文系统地展示和分析了文安5.1级地震前锦州地震台及其子台沈家台的前兆异常。     

Seismic vulnerability evaluation of axially loaded steel built-up laced members Ⅱ： evaluations

The test results described in Part 1 of this paper （Lee and Bruneau, 2008） on twelve steel built-up laced members （BLMs） subjected to quasi-static loading are analyzed to provide better knowledge on their seismic behavior. Strength capacity of the BLM specimens is correlated with the strength predicted by the AISC LRFD Specifications. Assessments of hysteretic properties such as ductility capacity, energy dissipation capacity, and strength degradation after buckling of the specimen are performed. The compressive strength of BLMs is found to be relatively well predicted by the AISC LRFD Specifications. BLMs with smaller kl/r were ductile but failed to reach the target ductility of 3.0 before starting to fracture, while those with larger kl/r could meet the ductility demand in most cases. The normalized energy dissipation ratio, EC/ET and the normalized compressive strength degradation, Cr″/Cr of BLMs typically decrease as normalized displacements δ/δb,exp increase, and the ratios for specimens with larger kl/r dropped more rapidly than for specimens with smaller kl/r; similar trends were observed for the monolithic braces. The BLMs with a smaller slenderness ratio, kl/r, and width-to-thickness ratio, b/t, experienced a larger number of inelastic cycles than those with larger ratios.     

首都圈及山西断陷带北部地壳垂直形变与地震危险性分析

根据首都圈地区及山西断陷带精密水准复测资料,分析了近十年来地壳垂直形变状态与特征。结果表明,研究区的东北区域表现为整体下降,下降速率约2～4mm／a;但“北升南降”的运动格局基本没有改变。太行山以西至山西断陷带的东侧地区为整体隆升。隆升速率最大近8mm／a。运动的时空分布从“南快北慢”整体上升的特征,逐步转变为“北升南降”的有升有降的特征。西区上述运动性质发生变化是以2001年为分界线,同时在延怀盆地及其附近区域形成了四象限分布的形变图像。但这一图像从规模和量级上都小于大同地震前的变形。山西断陷带北部的运动表现为断陷型的垂直运动,整体呈下降趋势,运动速率为4～6mm／a。上述特征表明监测区未来2～3年内发生6级以上地震的可能性不大。     

Nonlinear behavior of high-damping rubber bearings under horizontal bidirectional loading: full-scale tests and analytical modeling

Horizontal bidirectional loading tests are conducted for real-sized high-damping rubber (HDR) bearings with diameters of 700 mm (HDR700) and 1300 mm (HDR1300). The hysteresis loops of these bearings under bidirectional horizontal loadings are compared with those under unidirectional loadings. The results show that the bearing force measurement in the primary direction of loading increases when there is displacement in the orthogonal direction. Unusually, the maximum restoring force in the orthogonal direction to the primary loading direction occurs near zero displacement. On the basis of the observations of the restoring forces, a rate-independent model is proposed. This model simulates well the test results under both bidirectional loading and unidirectional loading. It can reproduce the irregular restoring forces characteristics around zero displacement as described above. Bidirectional loading induced twist deformation in the HDR bearings that increased local shear strains. This phenomenon results in an early failure as observed in HDR700. The additional shear strain is estimated based on the twist deformation measured by video image analysis. The comparison of the nominal total shear stress demonstrates that the increase of shear stress because of bidirectional loading occurs when the average shear strain is larger than about 200%. The larger the shear strain, the greater the bidirectional effect. It is shown that the nominal total shear stress of average strain of 350% under bidirectional circular loading pattern is approximately the same as the average shear strain of 400% under unidirectional loading. This means that the average shear strain of 350% under a bidirectional circular loading corresponds to a local shear strain of 400%. Copyright © 2012 John Wiley & Sons, Ltd.