考虑土-结构相互作用的西安钟楼地震反应分析

为探讨土-结构相互作用对西安钟楼地震反应的影响,建立了钟楼上部木结构-台基-地基三维有限元模型,基于粘-弹性人工边界条件,利用振型分解反应谱法进行了地震反应分析。结果表明,考虑相互作用木结构2层相对位移反应增大了2.12倍,台基相对于地面间的相对位移增大了44%。因此,在对钟楼结构进行地震反应分析时必须考虑土-结构相互作用。     

基于高塔观测的登陆台风边界层风切变指数拟合

利用深圳气象梯度观测塔观测数据, 以2017年以来进入深圳150 km范围的7个台风个例为研究对象, 基于幂指数律拟合讨论台风边界层风切变指数的变化规律。结果表明:幂指数能较好地拟合台风影响下350 m高度以下风廓线, 随着拟合高度范围增加, 风切变指数增大, 拟合精度基本维持;用深圳气象梯度观测塔等差层数据拟合台风风速效果好于全层次数据和等比层数据拟合;7个台风影响期间拟合风切变指数平均值为0.268, 明显高于以往研究(0.1~0.177), 主要原因是拟合的高度范围较以往研究明显增大, 此外还与强风样本较少以及下垫面更粗糙有关。利用幂函数拟合台风不同风速段最大风切变指数, 可在台风过程中预估不同高度极端大风风险。研究还表明:台风眼经过铁塔前后风切变指数明显升高, 在抗风设计以及台风防御过程中应充分考虑这一变化。     

关于比萨斜塔的整治情况

简要介绍比萨斜塔的历史、倾斜过程及目前的状态，对比萨斜塔的整治提出了结构方案和土工方案，并给出了比萨斜塔的地基土层的力学模型与力学性质，根据塔基土体的力学性质对整治方案进行了分析。     

Surface sediment characteristics and tower karst dissolution, Guilin, southern China

Dissolution of extensive outcrops of limestone and dolostone in humid tropical and subtropical southern China produced numerous caves and residual hills that are referred as tower karst. This study identifies and relates the physical and chemical characteristics of the surface sediment with the limestone bedrock in Guilin to assess the influence of the limestone dissolution process on sediment composition.The results of this study indicated that (i) both limestone and dolostone of the region are very pure (99.5% and 98.5% of CaCO₃ and MgCO₃, respectively); (ii) the material composition of limestone and dolostone is different from that of soil and sediment of the region: constituents of surface sediments are highly related with the clastic sedimentary rocks, such as the mudstone, but show negative correlation with limestone and dolostone; (iii) the limestone formations are highly resistant to physical weathering and disintegration; their durability versus physical weathering and their high susceptibility to chemical dissolution account for why residual towers can form and persist; (iv) a dual-zone environmental structure exists vertically downward from the surface in Guilin: the zone of unconsolidated clastic sediments that is predominantly acidic, and the zone of karstified limestone that is predominantly basic. The evidence suggests that the environment and processes differ in these two zones. The chemical dissolution of limestone that formed tower karst of the region is not mainly responsible for the accumulation of clastic sediment on the surface.     

黄土高原土壤裸露与景观格局关系——以延安市宝塔区为例

土壤裸露是水土流失具体的空间表现,同时又是导致进一步水土流失的重要因素。由人类和自然相互作用下形成的景观格局对土壤裸露具有深刻的影响。为深入探讨二者间的内部联系,文章选定位于黄土高原的延安市宝塔区为研究区,分别就景观格局的类型组成和空间结构,分析其与土壤裸露的关系。研究结果可知人为活动强度较大的区域土壤裸露程度较高,在景观类型上,表现出滩地、农村居民点、其他建设用地、低覆盖度草地及山区旱地等景观类型的土壤裸露值较高,另外,从景观组成来看,农牧组成为主的流域土壤裸露值明显高于其他流域;通过景观空间结构与土壤裸露的关系分析,可知个体单元型态、空间构型以及整体多样性等景观空间结构特征,均对土壤裸露程度具有不同大小的指示意义,其中又以景观聚集度及平均斑块面积与土壤裸露程度有强烈负相关。     

塔式容器震害预测

本文根据塔式容器的结构地震荷载计算和地震破坏的经验,建立了塔式容器的一种震害预测方法,该方法以塔式容器地脚螺栓的抗拉强度和根径确定抗震系数,通过抗震系数确定塔式容器相应的破坏等级,简单易行,文中用此方法对大连石化公司的塔式容器进行了震害预测,初步验证了该方法的可靠性。     

Seismic analysis of the Asinelli Tower and earthquakes in Bologna

The existence of a valuable historical heritage of the Medieval age in Bologna has motivated a deeper study on the seismic behaviour of the Asinelli Tower, which, beyond being the town symbol, has a structural configuration prone to seismic damage. Accordingly, in the present paper, the seismicity of Bologna is reviewed and a synthesis of the damage observed in the urban area, based on an accurate historical research, is given, with the objective of evaluating the behavior of the Asinelli Tower within the framework of the effects localized in the municipality. An assessment of the tower's stability with respect to compatible seismic events, at least qualitatively, with the region seismicity is then carried out by means of a non-linear dynamic analysis on a simplified model.     

八家子铅锌矿硫同位素特征及其地质意义

八家子铅锌矿位于虹螺山—五指山成矿带的南端,矿床赋存于长城系高于庄组及大红峪组中。本文通过130件硫同位素资料对全矿区的硫同位素特征,不同成矿阶段,不同组构以及不同矿物的硫同位素组成进行了系统研究。全区δ~(34)S分布范围为 16.4‰—-19.1‰,δ~(34)S(?)s为2.16‰,硫同位素具有水平分带及垂直分带特征。同时还对矿床的硫同位素平衡温度和平衡程度进行了计算和估计,并结合包体测温结果确定矿床的成矿温度介于低温到高温之间,主成矿期温度以中温(300—400℃)为主。上述研究表明,本区的硫同位素组成特征是沉积岩和岩浆热液共同作用的结果,成矿作用应以岩浆热液作用为主。     

地质雷达在溪洛渡浙西800kV特高压直流输电线路工程塔基勘察中的应用

溪洛渡浙西800kV 特高压直流输电线路经过的湘西地区交通极为不便,地形起伏较大,地质条件复杂,在这一地区开展工程钻探工作,困难重重。初勘资料表明,线路经过的灰岩区,岩溶发育强烈,对塔基稳定构成安全威胁,同时线路经过的砂岩区中部分塔基覆盖黏土层中含有风化碎屑,普通麻花钻难以准确判定覆盖层厚度。为了查明塔基下方岩溶发育情况,基岩面埋深等工程地质问题,经综合试验比选,采用地质雷达进行探测。岩溶探测过程中为了进一步查清桩孔基底之下至少5m以内的岩溶情况,除了地面工作外,还进行了桩底探测。钻探及施工开挖结果表明地质雷达能有效探查地下隐伏岩溶、基岩面、风化带、断裂及破碎带等,为合理选择塔位、设计基础深度提供了科学依据,取得了良好的应用效果。