An experimental investigation of water level effects on the dynamic behaviour of a large arch dam

The need for full‐scale dynamic tests, which are recognized as the most reliable method to evaluate a structure's vibration properties, is increasing as new analysis techniques are developed that take into account the complex interaction phenomenons that occur in dam–reservoir–foundation systems. They are extremely useful to obtain reliable data for the calibration of newly developed numerical methods. The Earthquake Engineering and Structural Dynamics Research Center (CRGP) at the University of Sherbrooke has been developing and applying dynamic testing methods for large structures in the past 10 years. This paper presents the experimental evaluation of the effects of the varying water level on the dynamic response of the 180 m Emosson arch dam in Switzerland. Repeated forced‐vibration tests were carried out on the dam during four different periods of the reservoir's filling cycle during a one‐year span. Acceleration and hydrodynamic pressure frequency responses were obtained at several locations while the dam was subjected to horizontal harmonic loading. The variation of the resonant frequencies as a function of the reservoir level is investigated. A summary of the ongoing numerical correlation phase with a three‐dimensional finite element model for the dam–reservoir–foundation system is also presented. Copyright © 2001 John Wiley & Sons, Ltd.     

Seismic interaction in linearly connected electrical substation equipment

An electrical substation consists of a complex set of equipment items that are interconnected through conductor buses or cables. If the connections are not sufficiently flexible, significant dynamic interaction may occur between the connected equipment items during a seismic excitation. This interaction is believed to be responsible for some of the observed substation equipment damage in recent earthquakes. This paper investigates the interaction between two equipment items connected by a linear spring‐dashpot or spring‐dashpot‐mass element representing a conductor bus. It is found that the interaction between the two equipment items may significantly amplify the response of the higher‐frequency equipment item. The influences of various key parameters on the interaction effect are quantified. Means for reducing the adverse interaction effect are described. Copyright © 2001 John Wiley & Sons, Ltd.     

A Reliability Based Expert System for Assessment and Mitigation of Landslides Hazard Under Seismic Loading

Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem. The models also take into consideration the spatial variabilities and correlations of soil properties. The developed models are incorporated in a computer program PTDDSSA.These analysis/design procedures are incorporated within a code named SARETL developed in this study for stability analysis and remediation of earthquake triggered landslides. In addition to the dynamic inertia forces, the system takes into consideration local site effects.The code is capable of assessing the landslide hazard affecting major transportation routes in the event of earthquakes and preparing earthquake induced landslide hazard maps (i.e., maps showing expected displacements and probability of slope/embankments failure) for different earthquake magnitudes and environmental conditions. It can also beused for proposing a mitigation strategy against landslides.     

Scale Invariances in the Morphology and Evolution of Braided Rivers

This paper presents an overview and synthesis of an extensive research effort to characterize and quantify scale invariances in the morphology and evolution of braided rivers. Braided rivers were shown to exhibit anisotropic spatial scaling (self-affinity) in their morphology, implying a statistical scale invariance under appropriate rescaling of the axes along and perpendicular to the main direction of flow. The scaling exponents were found similar in rivers of diverse flow regimes, slopes, types of bed material and braid plain widths, indicating the presence of universal features in the underlying mechanisms responsible for the formation of their spatial structure. In regions where predominant geologic controls or predominant flow paths were present, no spatial scaling was found. Regarding their spatiotemporal evolution, braided rivers were found to exhibit dynamic scaling, implying that a smaller part of a braided river evolves identically to a larger one provided that space and time are appropriately normalized. Based on these findings, and some additional analysis of experimental rivers as they approach equilibrium, it was concluded that the mechanism bringing braided rivers to a state where they show spatial and temporal scaling is self-organized criticality and inferences about the physical mechanisms of self-organization were suggested.     

Algorithm of Calculation of Lyapounov Coefficients for Analysis of Chemical Autooscillations, as Applied to Calcite Crystallization Model

The numerical algorithm of calculation of Lyapounov coefficients (L _k) of any order is developed. The apparatus of analytical calculations is not used in this algorithm. The proposed algorithm is of use for usual computer languages and allows us to find the numerical value of L _k for any k and to make complete qualitative analyses of dynamic models on the plane.     

Pegmatite Emplacement in the Seridó Belt, Northeastern Brazil: Late Stage Kinematics of the Brasiliano Orogen

Geometric and kinematic analysis was performed in an area located in the central part of the Seridó Belt (NE Brazil), where supracrustal rocks affected by polyphase deformation are well exposed. The first event recognized in this area (and regionally known as the D₂ deformation) is characterized by top to the south thrust tectonics while a second one (D₃ deformation) is marked by upright folds, strike-slip or transpressive shear zones and the development of flower structures. Major pegmatite swarms were emplaced during and late as regards the second event (dated ca. 580 Ma), being part of the Brasiliano orogeny; similar dyke swarms are known from the Nigerian Shield. These pegmatite swarms provide reliable kinematic markers of the late evolutionary stage of the Neoproterozoic Trans-Sahara-Borborema collisional belt. Mineralogical, geometric and kinematic features support two stages of pegmatite emplacement during the strike-slip event: (i) older, syn-D₃ homogeneous pegmatites intruded mostly along lithological and structural discontinuities, such as foliation surfaces; (ii) late, D₃ heterogeneous pegmatites were emplaced along tension gashes and other dilation structures. The heterogeneous pegmatites are economically more important, being exploited for precious metals and stones, as well as industrial minerals.     

Rotation and dilation deformation mechanisms for auxetic behaviour in the α-cristobalite tetrahedral framework structure

 Analytical expressions are derived for the Poisson's ratios associated with a three-dimensional network of regular, corner-sharing tetrahedra in which: (1) the tetrahedra are assumed to be rigid and free to rotate relative to each other; (2) the tetrahedra are assumed to maintain shape and orientation but are free to change size (dilate); (3) tetrahedral rotation and dilation are assumed to act concurrently. The structure has a primitive unit cell containing four tetrahedra and is analogous to the molecular structure of α-cristobalite. Strain-dependent variations in Poisson's ratio are also predicted by the models. For deformation due to tetrahedral rotation the network is found to exhibit negative Poisson's ratios in each of the three principal directions, with the magnitude of the Poisson's ratio being dependent on the angle of rotation of the tetrahedra. The behaviour of the Poisson's ratio is isotropic in the transverse plane, but anisotropic elsewhere. In the dilation model negative Poisson's ratios equal to −1 are observed for uniaxial loading in any of the principal directions, with the value being constant irrespective of tetrahedral size. The model for concurrent tetrahedral rotation and dilation allows positive as well as negative Poisson's ratios, with the values determined by the framework geometry and relative strengths of the two mechanisms. The concurrent model also offers a design route to materials and structures having ultrahigh Young's moduli. Received: 15 February 2000 / Accepted: 1 October 2000     

喜马拉雅构造-成矿域及其成矿效应初步分析

通过近年来的研究 ,提出了全新的喜马拉雅构造 -成矿域概念。从大喜马拉雅构造域及其成矿效应出发 ,通过构造域对矿集区的控制作用、成矿时代、成矿物质来源、深部过程与成矿效应的分析 ,从而较全面地评价了青藏高原及邻区的资源潜力和需要进一步工作的重要成矿带或矿集区。通过分析认为喜马拉雅构造 -成矿域内强烈的壳幔物质交换 ,下地壳翻天覆地的物质和流体交换 ,导致了在同一构造地质单元内可以有一个或多个超大型矿床的存在。并对多个重要矿床类型提出了更切合实际的观点 ,如西藏甲马铜钼银铅锌金多金属矿床属于矽卡岩 -斑岩复合型 ,云南羊拉铜钼金多金属矿床也属于矽卡岩 -斑岩复合型矿床等。在喜马拉雅构造域内形成的燕山晚期或喜马拉雅期矿床大多和大陆地壳深部复杂的动力学过程有关 ,所形成的矿床矿物组合及成矿元素组合复杂 ,特别是矿石中钴、银元素含量较高 ,许多矿床中银、钴已经作为主要成矿元素。最后明确提出了青藏高原主体及东缘重要矿集区的资源潜力     

Tectonic Dynamic Metallization of Silver-GoldHydrothermal Fluids in Proterozoic GneissTerrene Shear Zones, Suichang, Zhejiang, China

-,The well-known Suichang silvengold field is located inZhejiang Province of SOutheast China. It is the largest silver-gold deposit associated with copper and zinc in the Cathaysianmetallogenic province.There are a series of silver-gold dePOsits in the shear zonesof Proterozoic gneiss terrene, Suichang region. The volcanicapparatus at Mesozoic has complicated rpineralization. Respectively, there are two pieces of understanding on the origin ofore-formigg nuid: (l ) metamorphic fluid (Lia…     

二维滞弹性非静力平衡云模式第二部分──中低空风切变对云微物理过程的影响

本文运用已建立的二维时变云模式［1］，就中低空风垂直切变对对流和云微物理过程的影响进行了模拟研究。为此设计了五种方案进行了对比试验。结果表明：中低空风切变较小时，容易爆发对流；中低空切变不超过某一值时，对流发展缓慢，但最终会爆发强对流；一旦中低空风切变超过某一值时，则对流发展不起来。另一方面，中低空风切变可加强各云微物理过程及地面降水量。