滇西南普洱强震群地区地壳形变的数值模拟

滇西南普洱一带地质构造复杂,中-强地震成群活动特征明显,地壳的形变特征与形变机制引起了地学界的广泛关注和深入研究。在参考、借鉴以往研究成果的基础上,本文构建了普洱一带包含活动断裂的二维板有限元模型,以GPS测量得到的块体年运动量作为模型区域的边界约束,模拟计算获得了普洱地区的构造形变空间分布,以NEE、NNW 2个方向、从数值模拟角度对普洱地区的水平形变特征和区域地壳垂直形变场进行了分析和探讨。结果表明:在青藏高原东南缘扩展、高原物质重力滑塌型南东向移动的动力学背景下,研究区内NEE向断裂的活动带动牵引NNW向断裂共轭运动,隆升性质的垂直形变场与60年的大区域水准测量结果相吻合,沿NNW向形变场的分布无规律,应是区域应力累积和震后调整双重作用的结果。沿NEE向形变场呈现了较明显的西部大于东部的分布图像,特别是西北部高值区对应了2014年景谷6.6级强震,最后对研究区的区域动力学问题进行了初步探讨。     

波浪作用下锚链系泊浮式防波堤动力响应的数值模型研究

浮式防波堤充分利用波能在水深方向的分布特性,在满足工程消浪要求的同时对海域水沙交换影响较小,且能够快速布置,在某些实际工程有一定应用前景。为了深入了解波浪作用下浮式防波堤的动力响应,基于OpenFOAM标准求解器olaFlow,在刚体运动求解计算中植入锚链求解模块MOODY(mooring cable dynamics),实现了基于重叠网格方法的浮体运动与锚链受力耦合求解,建立了锚链系泊浮式防波堤动力响应的二维数值模型。利用该数值模型对锚链系泊单方箱浮式防波堤在波浪作用下的透射系数、运动响应、锚链张力进行了模拟,并和相关试验结果进行了比较。结果表明,模型能够准确模拟二维波浪和浮式防波堤的相互作用,并用于三维模型的改进。     

软悬挂状态下隔水管动力特性分析

建立了软悬挂状态下隔水管动力分析模型,采用有限单元法对模型进行离散,结合Newmark-β法对动态方程求解,并对模型进行验证,最后选取南海某口深水井实际参数,对软悬挂状态下隔水管动力特性进行分析。研究结果表明:软悬挂状态下隔水管底端横向位移最大,顶部铰接处弯矩最大。软悬挂状态下,隔水管横向位移与弯矩随着海底隔水管总成(LMRP)重量增加而减小,随着平台运动速度、平台航向与海流方向夹角增大而增大;回收隔水管减小悬挂长度有利于减小最大横向位移,但会造成弯矩轻微增加;采用旋转刚度适当较大的挠性接头则有利于减小隔水管挠性接头以下整体位移与弯矩。研究成果为钻井平台避台撤离时隔水管的安全提供理论指导。     

An approach for shake table performance evaluation during repair and retrofit actions

Large‐scale, servo‐hydraulic shake tables are a central fixture of many earthquake engineering and structural dynamics laboratories. Wear and component failure from frequent use may lead to control problems resulting in reduced motion fidelity, necessitating repairs and replacement of major components. This paper presents a methodology to evaluate shake table performance pre‐ and post‐repair, including the definition of important performance metrics. The strategy suggested is presented in the context of the rebuilding of a 4.9 × 3.1 m, 350‐kN‐capacity uniaxial shake table. In this case, the rebuild consisted of characterization of wear to table components, replacement of worn bearing surfaces, and replacement of hydraulic accumulators. To assess the effectiveness of the repair actions, sinusoidal and triangular waves, white noise, and earthquake histories were run on the table before and after the rebuild. The repair actions were successful in reducing the position and velocity dependence of friction, improving the ability of control algorithms to accurately reproduce earthquake motions. The maximum and average response spectral misfits in the period range of 0.1–2 seconds were reduced from approximately 50% to 15%, and from 5% to less than 2.5%, respectively.     

Near-bankfull floods in an Alpine stream: Effects on the sediment mobility and bedload magnitude

In a mountain environment, the transport of coarse material is a key factor for many fields such as geomorphology, ecology, hazard assessment, and reservoir management. Despite this, there have been only a few field investigations of bedload, in particular using multiple monitoring methods. In this sense, attention has frequently focused on the effects of “high magnitude/low frequency floods” rather than on “ordinary events”. This study aims to analyze the sediment dynamics triggered by three high-frequency floods (recurrence interval “RI” between 1.1 and 1.7 yr) that occurred in the Rio Cordon basin during 2014. The flood events were investigated in terms of both sediment mobility and bedload magnitude. The Rio Cordon is an Alpine basin located in northeastern Italy. The catchment has a surface area of 5 km², ranging between 1763 and 2763 m above sea level. The Rio Cordon flows on an armored streambed layer, with a stable step-pool configuration and large boulders. Since 1986, the basin has been equipped with a permanent station to continuously monitor water discharge and sediment flux. To investigate sediment mobility, 250 PIT-tags were installed in the streambed in 2012. The 2014 floods showed a clear difference in terms of tracer displacement. The near-bankfull events showed equal mobility conditions, with mean travel distance one order of magnitude higher than the below-bankfull event. Furthermore, only the near-bankfull events transported coarse material to the monitoring station. Both events had a peak discharge up to 2.06 m³ s^-1, but the bedload transport rates differed by more than one order of magnitude, proving that under the current supply-limited condition, the bedload appears more related to the sediment supply than to the magnitude of the hydrological features. In this sense, the results demonstrated that near-bankfull events can mobilize large amounts of material for long distances, and that floods of apparently similar magnitude may lead to different sediment dynamics, depending on the type and amount of sediment supply.     

2016年射阳MS 4.4地震前后重力场变化

利用江苏重力测网2014-2017年重力场观测资料,采用绝对重力控制与相对重力联测相结合的平差方法,获取2016年射阳M_S 4.4地震前后重力场变化图。根据射阳M_S 4.4地震前后射阳地区各测线重力段差变化特点,绘制重力场等值线并进行对比分析,结合相关机理,探讨重力场变化与该地震的内在联系。同震观测数据显示：射阳M_S 4.4地震发生在重力异常值高梯度带附近,发震时震中地区位于NS挤压正异常、EW张拉负异常状态,震后区域重力梯度变化量开始减小,是一种典型的重力异常调整现象。     

青藏高原“亚东—东巧—葫芦湖”大陆裂谷带形成的深层动力过程

正确理解亚东—东巧—葫芦湖构造带的形成与属性对深化认识青藏高原的地壳形变、物质运动的行为与轨迹和深层动力过程极为重要.通过较系统的多元要素分析和研究发现：（1）基于壳、幔结构的空间展布特征表明,这是一条在EW向拉张力系作用下的陆内裂谷带;（2）强烈地震的活动与发生、大地热流异常值展布和地幔对流应力场研究证明,它是一条现今活动的大陆裂谷带;（3）该裂谷带的形成与演化乃地球内部物质与能量强烈交换的产物.     

A data‐based mechanistic modelling (DBM) approach to understanding dynamic sediment transmission through Wyresdale Park Reservoir,Lancashire, UK

This paper outlines the application of a new data‐based mechanistic (DBM) modelling methodology to the characterization of the sediment transmission dynamics in a small upland reservoir, Wyresdale Park, Lancashire. The DBM modelling strategy exploits advanced statistical procedures to infer the dynamic model structure and its associated parameters directly from the instrumented data, producing a parametrically efficient, continuous time, transfer function model which relates suspended sediment load at the reservoir inflow to the outflow at the event scale. The associated differential equation model parameters have physical attributes which can be interpreted in terms of sediment transmission processes and associated reservoir trap efficiency. Sedigraph analysis suggests that wind‐induced resuspension episodically supplies an additional load to the reservoir outlet. The stochastic nature of the DBM model makes it ideal for evaluating the effects of uncertainty through Monte Carlo simulations (MCS) for discharge and sediment transmission. Copyright © 2000 John Wiley & Sons, Ltd.     

Design of dampers for structures based on optimal control theory

The aim of this paper was to propose a design guideline for using visco‐elastic dampers for the control of building structures subjected to earthquake loading as well as suspension roof structures subjected to wind loading. The active control algorithm was used to calculate the control forces. Based on the single‐mode approach the control forces were transformed to the forces which visco‐elastic dampers can provide. Application of the method to the design of the building structure with passive damping devices in the bracing system and to the suspension roof with dampers was studied. Through the application of optimal control theory a systematic design procedure to implement dampers in structures is proposed. Copyright © 2000 John Wiley & Sons, Ltd.     

中国地区水平地壳形变模型的建立

我国大陆板块是欧亚大陆板块的重要组成部分,其板块运动剧烈,地质构造复杂,是全球研究板块运动的重要地区。本文通过对各个块体分别建模和解算,得出结论:中国地区除东北块体相对于欧亚板块不动外,其他块体均有不同程度的形变运动,东部形变较小,西部形变较大;华北块体总体上以大约6mm/a的速率向东运动;华南块体以约5~8mm/a的速率向东南方向运动;新疆块体以约10~15mm/a的速率向北东方向运动;西藏块体也向北东方向运动,但运动速率从南到北逐步减少。