Alpine ocean seafloor spreading and onset of pelagic sedimentation: new radiolarian data from the Chenaillet-Montgenèvre ophiolite (French-Italian Alps)

Radiolarians of Middle Jurassic age (tentatively middle Bathonian) provide the first direct age determination from oceanic sediments associated with the Chenaillet-Montgenèvre ophiolite (Piemonte zone, French-Italian Alps). This datum obtained from radiolarites of the Lago Nero- Replatte thrust sheet is older than those previously established on ophiolite sedimentary covers from this segment of the western Alps. It also shows that Lago Nero-Replatte basal radiolarites are anterior to the youngest intrusives from the overlying Chenaillet s.s. thrust sheet. This chronological relationship implies either a late seafloor spreading-related magmatic activity in places younger than adjacent initial pelagic sedimentation, or more likely that the Lago Nero-Replatte and the Chenaillet s.s. thrust sheets are distinct and distant pieces of lithosphere that were eventually stacked together: the Lago Nero-Replatte unit was trapped within the accretionary wedge while the Chenaillet s.s., of a younger age and in a more distal position with regards to the European margin, was obducted. Regionally, the Lago Nero-Replatte sediments appear to be coeval to other Bathonian supraophiolitic radiolarites exposed in the western Alps. These results strengthen the Bathonian correlation of widespread seafloor spreading in both western Tethys and the central Atlantic ocean.     

Validation of Practice Oriented Models and Influence of Soil Stiffness on Lateral Pile Response Due to Kinematic Loading

Earthquakes usually cause both inertial and kinematic loading of pile foundations. Inertial loading and lateral pile response can be predicted to a certain extent by lateral pile load tests for important engineering projects. However, there is no accepted in situ assessment method for pile behavior due to kinematic loading. Therefore, it is important for geotechnical engineering practice to validate the practice oriented models and examine the influence of soil strength parameters on the performance of kinematically loaded piles due to lateral spreading. For this purpose, a well-documented case of full-scale lateral spreading test conducted at Port of Tokachi in Japan by Ashford et al. (2006 Ashford , S. A. , T. Juirnarongrit , T. Sugano , and M. Hamada . 2006 . Soil-pile response to blast-induced lateral spreading. I: Field test . Journal of Geotechnical and Geoenvironmental Engineering 132 ( 2 ): 152 – 162 . [Google Scholar]) is selected as a primary reference in terms of test data and site conditions. Four p-y analyses are performed using a special purpose software based on finite difference technique. The first two investigate the employment of different p-y curves suggested in the literature. The third one investigates the influence of variations in internal friction angle and undrained shear strength. In the fourth analysis, liquefied shear strength and residual shear strength approaches are utilized for the liquefiable layers and their effects are investigated. In all analyses, mobilized lateral pressures in non-liquefied layers are also scrutinized. The results of the analyses are discussed and compared with the measured values in the field. Finally, conclusions are given based on the analyses and discussions.     

Characterization of mixing and spreading in a bounded stratified medium

Matheron and de Marsily [Matheron M, de Marsily G. Is the transport in porous media always diffusive? A counter-example. Water Resour Res 1980;16:901–17] studied transport in a perfectly stratified infinite medium as an idealized aquifer model. They observed superdiffusive solute spreading quantified by anomalous increase of the apparent longitudinal dispersion coefficient with the square root of time. Here, we investigate solute transport in a vertically bounded stratified random medium. Unlike for the infinite medium at asymptotically long times, disorder-induced mixing and spreading is uniquely quantified by a constant Taylor dispersion coefficient. Using a stochastic modeling approach we study the effective mixing and spreading dynamics at pre-asymptotic times in terms of effective average transport coefficients. The latter are defined on the basis of local moments, i.e., moments of the transport Green function. We investigate the impact of the position of the initial plume and the initial plume size on the (highly anomalous) pre-asymptotic effective spreading and mixing dynamics for single realizations and in average. Effectively, the system “remembers” its initial state, the effective transport coefficients show so-called memory effects, which disappear after the solute has sampled the full vertical extent of the medium. We study the impact of the intrinsic non-ergodicity of the confined medium on the validity of the stochastic modeling approach and study in this context the transition from the finite to the infinite medium.     

Major advances in liquefaction research by laboratory tests compared with in situ behavior

Major advances in liquefaction research in the laboratory to understand the basic mechanisms in comparison with in situ behavior during previous earthquakes are reviewed. Then, several issues related to liquefaction triggering and post-liquefaction deformation are selected for further discussion in the author's perspective. These include effects of fines associated with aging, effects of gravels, effects of initial shear stress, and lateral spreading and lateral flow due to void redistribution. It has been disclosed that a quite a few issues still remain to be settled in evaluating liquefaction onset and post-liquefaction deformations for improving engineering design, particularly for Performance-Based Design (PBD).     

Response of a pile group behind quay wall to liquefaction-induced lateral spreading:a shake-table investigation

The response of pile foundations near a quay wall under liquefaction-induced lateral spreading remains a complex problem. This study presents the results of a shake-table test on a 2×2 pile group behind a sheet-pile quay wall that was subjected to lateral spreading. The quay wall was employed to trigger liquefaction-induced large lateral ground deformation. The discussions focus on the behavior of the pile and the soil and on the bending moment distributions within the group pile and the restoring force characteristics at the superstructure. Overall, the piles exhibited apparent pinning effects that reduced soil deformation. In addition, the rear-row piles near the quay wall experienced larger bending moments than did the front-row piles, indicating significant pile group effects. The tests showed that lateral spreading could be a primary cause of larger monotonic deformations and bending moments. It can also be concluded that the monotonic bending moments were significantly decreased due to the presence of slow soil flow. The stiffness at the superstructure was reduced because of accumulated excess pore pressure before liquefaction, and it was recovered during lateral spreading. The present study further enhances current understanding of the behavior of low-cap pile foundations under lateral spreading.     

一种改进的林火蔓延模型及其实现

为了研究林火蔓延的动态模拟问题,结合元胞自动机原理,对现有的林火蔓延数学模型进行改进,提出一种新的模拟林火蔓延模型。该模型充分表达了可燃物类型、温度、湿度、坡度、风速和风向等林火蔓延影响因子在元胞空间中的作用形式,通过求解出燃烧元胞向摩尔(Moore)型邻域中八个方向元胞的林火蔓延速度,来确定元胞状态演变规则函数。最后,利用地理信息系统二次开发技术将该模型表达成计算机算法,实现了不同条件下的林火行为的仿真模拟。     

西太平洋帕里西维拉海盆不对称性发育特征及其成因

西太平洋帕里西维拉海盆是伊豆-小笠原-马里亚纳"沟-弧-盆"体系下众多弧后扩张盆地中最大的一个,地质、地球物理资料显示该海盆具有明显的不对称发育特征,但长期以来对其成因缺乏系统研究。本文深入分析了帕里西维拉海盆东西两侧的几何形态、地形地貌、沉积特征与地球物理特征,以及盆地南端东翼的缺失和西翼明显的弯曲构造特征,并结合海盆区域板块运动机制研究认为：盆地不对称性发育特征的成因主要在于盆地的构造发育背景、盆地两侧构造活动与沉积环境的差异,盆地东西两侧的不对称发育主要受盆地发育过程中两侧的构造过程与沉积环境控制;盆地南端东翼的缺失和西翼的弯曲构造更多地受到东侧加洛林板块特别是加洛林脊俯冲作用的影响。     

滑模摊铺机在混凝土路面施工中的应用

泰曲路(泰安-曲阜)改造工程三合同段的混凝土路面采用滑模摊铺机进行施工,滑摸摊铺机在不用固定模板的情况下可以连续完成摊铺、振动、刮平、成形、抹光以及打设传力杆等工序,工艺先进,具有一定的推广价值。     

青海南部蛇绿岩中辉长岩锆石SHRIMP U-Pb定年和岩石地球化学特征

青海南部蛇绿岩呈构造岩片产于晚三叠世浅变质细碎屑岩中.扎河地区出露的辉长岩为蛇绿岩的组成单元,属低钾拉斑系列,其锆石SHRIMP U-Pb年龄为(239.8±3.1)Ma,表明岩石形成于中三叠世早期.地球化学特征上,岩石富MgO、Al2O3,低K2O、TiO2;REE总量低,(La/Yb)N=1.10～4.40,LREE略显富集,δEu=1.50～2.41,具有明显正铕异常;大离子亲石元素(Rb、Ba、Sr、Th、U)富集、高场强元素(Nb、Zr、Ti)亏损,反映岩浆源区曾遭受到俯冲组分的影响.综合分析认为,扎河辉长岩岩石具有板内和弧岩浆岩的双重属性,其形成环境为弧后盆地,表明中三叠世早期巴颜喀拉盆地发生过一次拉张事件.在区域上,它是甘孜-理塘蛇绿岩的组成部分.     

Investigation on the stochastic simulation of strong ground motions for Bucharest area

This short article evaluates the stochastic method of ground motion simulation for Bucharest area using both the single-corner frequency model and recently introduced double-corner frequency models. A dedicated Q model is derived using ground motions obtained during the largest Vrancea earthquakes from the past 30 years. The simulated ground motions are tested against the observed data from the Vrancea earthquakes of August 1986 and May 1990. Moreover, the observed data are also compared against simulations obtained using the Q model derived by Oth et al. (2008). Finally, the results of the simulations show that the derived Q model is better suited for larger magnitude events, while the Q model of Oth et al. (2008) provides better results for smaller earthquakes.