近场地震动下偏心结构的减震控制研究

本文选用远场宽频地震Kanai-Tajimi模型与近场地震He-Agrawal速度脉冲模型,对现有的典型近场地震记录进行了非线性数值拟合。通过调整脉冲分量与宽频分量的比值,得到了不同脉冲分量的地震波,分析了在合成近场地震波作用下,设置粘滞阻尼器时偏心结构的动力反应,并与未设置阻尼器时结构的地震响应进行了对比,同时也对能反映结构偏心特性的参数进行了分析研究。通过数值模拟与仿真分析,得到了一些对实际工程设计有意义的结论。     

龙门山断层的造山机制

龙门山断层的抬升模式过去主要有由下部地壳的流动(Lower crustal channel flow,LCCF)模式与脆性地壳的增厚(Brittle crustal thickening)的变形模式。2008年汶川地震后,一般认为它是源自在浅部由压缩性断层所导致的造山运动,这应无疑义,但深部是否为由LCCF引发的浅部压缩性断层模式或仅为薄壳构造所引起仍有待证实。     

汶川8.0级地震地表变形局部化样式与建筑物破坏特征关系初步研究

本文以汶川地震地表形变带的实地测量数据为基础,结合沿实测地震地表变形剖面建筑物破坏情况的调查与测量,分析了不同地震地表变形类型及其建筑物破坏特征,定量化地讨论了地表变形梯度与建筑物破坏程度间的关系。提出无论地震地表变形表现为何种类型的断层陡坎,地表破裂、强变形局部化在宽10~30m的地表破裂带内;建筑物受损情况最直接的影响是建筑物所处地点的地表变形梯度,地表变形梯度大于0.1的地段,建筑物均完全被摧毁;地表变形梯度在0.07~0.1间的地段,建筑物遭受严重损坏,产生倾斜及强烈变形等;地表变形梯度在0.03~0.07之间的地段,建筑物可能受到中度损坏,产生倾斜及变形等,具有抗震设防能力的构建筑物一般不会倒塌;地表变形梯度小于0.03的地段具有抗震设防能力的构建筑物一般只会受到轻的损坏或基本完好。     

大地电磁三维正演并行算法研究

大地电磁法三维正演算法计算量大,用传统的串行程序计算相当耗时。而三维正演是逐个频率按顺序计算的,并行性好,适合并行运算。结合MPI自身的优越性,在深入分析大地电磁三维正演串行程序实现流程的基础上,确定了并行计算的思路,实现了三维正演的并行计算。通过三个理论模型对实现的三维正演并行程序进行了试算,分析对比了在多种情况下程序的执行效率。测试结果表明,所实现的三维正演并行程序运行结果正确,效率提高明显。此思路可为解决其它地球物理超大计算量问题所借鉴。     

结构主动控制和混合控制的装置和方法

本系统讨论了土木工程结构的主动控制和混合控制设备的构造和性能及其实际应用的效果；对一般非线性优化控制方法及其效用做了分析介绍；对当前土木工程结构控制研究中存在的困难和问题以及今后的发展趋势进行了分析讨论和展望。     

Acceleration of vegetation dynamics in hydrologically connected wetlands caused by dam operation

The dynamic responses of wetlands to upstream water conservancy projects are becoming increasingly crucial for watershed management. Poyang Lake is a dynamic wetland system of critical ecological importance and connected with the Yangtze river. However, in the context of disturbed water regime in Poyang Lake resulting from human activities and climate change, the responses of vegetation dynamics to the Three Gorges Dam (TGD) have not been investigated. We addressed this knowledge gap by using daily water level data and Landsat images from 1987 to 2018. Landsat images were acquired between October and December to ensure similar phenological conditions. Object-oriented Artificial Neural Network Regression for wetland classification was developed based on abundant training and validation samples. Interactions between vegetation coverage and water regimes pre and post the operation of the TGD were compared using classification and regression trees and the random forest model. Since the implementation of the TGD in 2003, Poyang Lake has become drier, especially during the dry season. A more rapid plant growth rate was observed post TGD (44.74 km² year⁻¹) compared to that of the entire study period (12.9 km² year⁻¹). Average water level for the antecedent 20 days most significantly affected vegetation before 2003, whereas average water level for the antecedent 5 or 10 days was more important after 2003. The impoundment of the TGD after the flood season accelerated the drawdown processes of Poyang Lake, and the rapidly exposed wetlands accelerated vegetation expansion during the dry seasons, resulting in shrinkage and degradation of the lake area. This study deepens our knowledge of the influences of newly developed dams on lakes and rivers.     

安宁河-则木河断裂带及周边地区Rayleigh波群速度背景噪声成像研究

安宁河-则木河断裂带位于川滇地块、巴颜喀拉地块和华南地块的交接部位,是川滇菱形块体的东部重要边界。利用布设在安宁河-则木河断裂带周边区域的西昌台阵和川西台阵均历时两年、共187个宽频带地震台站的垂直分量的背景噪声数据,采用噪声层析成像方法获得了这一区域4~20s的Rayleigh波群速度分布图像。与前人研究相比,本文结果的横向分辨率有明显改进,在安宁河-则木河断裂带可达20km左右,在其它区域可以达到20~40km。成像结果表明,安宁河-则木河断裂地区上地壳的速度结构存在明显横向不均匀性,速度分布特征与地表地质构造基本一致,不同周期的速度分布变化较小。盐源盆地、西昌盆地和四川盆地西南缘表现为低速异常。九龙附近和南部的德昌-盐边-巧家附近表现为高速异常,分别与出露的花岗岩体和峨眉山玄武岩有关。在安宁河断裂南段和则木河断裂北段能观测到断裂两侧的速度存在明显差异,其余断裂带两侧的速度对比不明显。贡嘎山附近的中上地壳表现为明显的低速异常,其东侧和西南侧高速体的阻挡,以及鲜水河-安宁河断裂带走向的变化,在贡嘎山区形成一个挤压弯曲段,使得川滇菱形块体的东南向水平运动转换为垂直于断裂的挤压作用和垂直隆升,导致了贡嘎山的快速隆起。     

Brittleness characteristics of tight oil siltstones

Rock brittleness directly affects reservoir fracturing and its evaluation is essential for establishing fracturing conditions prior to reservoir reforming. Dynamic and static brittleness data were collected from siltstones of the Qingshankou Formation in Songliao Basin. The brittle–plastic transition was investigated based on the stress–strain relation. The results suggest that the brittleness indices calculated by static elastic parameters are negatively correlated with the stress drop coefficient and the brittleness index B₂, defined as the average of the normalized Young’s modulus and Poisson’s ratio, is strongly correlated with the stress drop. The brittleness index B₂, Young’s modulus, and Poisson’s ratio correlate with the brittle minerals content; that is, quartz, carbonates, and pyrite. We also investigated the correlation between pore fluid and porosity and dynamic brittle characteristic based on index B₂. Pore fluid increases the plasticity of rock and reduces brittleness; moreover, with increasing porosity, rock brittleness decreases. The gas-saturated siltstone brittleness index is higher than that in oil- or water-saturated siltstone; the difference in the brittleness indices of oil- and water-saturated siltstone is very small. By comparing the rock mechanics and ultrasonic experiments, we find that the brittleness index obtained from the rock mechanics experiments is smaller than that obtained from the ultrasonic experiments; nevertheless, both decrease with increasing porosity as well as their differences. Ultrasonic waves propagate through the rock specimens without affecting them, whereas rock mechanics experiments are destructive and induce microcracking and porosity increases; consequently, the brittleness of low-porosity rocks is affected by the formation of internal microcrack systems.     

Recent progress and application on seismic isolation energy dissipation and control for structures in China

China is a country where 100% of the territory is located in a seismic zone. Most of the strong earthquakes are over prediction. Most fatalities are caused by structural collapse. Earthquakes not only cause severe damage to structures, but can also damage non-structural elements on and inside of facilities. This can halt city life, and disrupt hospitals, airports, bridges, power plants, and other infrastructure. Designers need to use new techniques to protect structures and facilities inside. Isolation, energy dissipation and, control systems are more and more widely used in recent years in China. Currently, there are nearly 6,500 structures with isolation and about 3,000 structures with passive energy dissipation or hybrid control in China. The mitigation techniques are applied to structures like residential buildings, large or complex structures, bridges, underwater tunnels, historical or cultural relic sites, and industrial facilities, and are used for retrofitting of existed structures. This paper introduces design rules and some new and innovative devices for seismic isolation, energy dissipation and hybrid control for civil and industrial structures. This paper also discusses the development trends for seismic resistance, seismic isolation, passive and active control techniques for the future in China and in the world.