盾构过富水砂层对地表建筑物影响的研究

结合深圳地铁2号线盾构过富水砂层施工实际,考虑流-固藕合水土本构关系,用FLAC3D软件建立了盾构施工数值分析模型。计算结果与工程实测数据对比验证了数值模型的合理性。进一步研究了盾构过富水砂层对地表不同位置建筑的影响:建筑物基础在隧道正上方时产生沉降最大且较均匀,水平位移最小;盾构机开挖下穿时建筑物差异沉降最大,建筑物倾向盾构开挖方向;建筑物基础横向上离隧道中心一倍隧道埋深时,建筑物水平移动最大,易受剪切破坏,倾向垂直盾构开挖方向,周边地表沉降差最大;建筑物离隧道中心横向距离超过两倍隧道埋深时,盾构开挖对建筑物基础沉降的影响较小,建筑物沉降与其周边地表沉降较均匀。     

地震作用下骆驼城土遗址的安全性评价

以甘肃高台地区国家级重点文物保护单位骆驼城土遗址为研究对象,对其依次采用实地勘察、室内土工试验、统计分析、数值模拟四种手段进行了研究。将可靠度理论引入有限元动力分析中,利用APDL语言编制程序,使用蒙特卡洛法进行一千次的抽样数值模拟后进行抗震概率性分析。从而实现了土遗址抗震安全性评价的一种新方法和手段。计算结果对于骆驼城土遗址抗震防护及加固具有重要的参考价值,同时也为类似土遗址的防灾减灾工作提供一定依据。     

钢管水泥土围护墙等效弹性模量的有限元计算

分析了水泥土围护墙弹性模量对于控制基坑变形的重要性、根据上海某钢管水泥土墙基坑支护的工程实例建立ABAQUS平面二维有限元模型,计算钢管水泥土围护墙等效弹性模量,量化了内插钢管对提高水泥土重力式围护结构的支护强度所起到的作用,并对钢管长度、外径、间距和插入位置进行了参数分析。     

基于CCD的高精度水管倾斜仪研制

CCD技术近年来已发展的非常成熟,应用范围广泛.本文介绍了利用CCD技术实现的高精度水管倾斜仪测量系统,其采用非接触式测量方法降低了测量过程中浮子干扰对测量精度的影响,体积小,安装简单,可用于流动观测中.     

玛曲断裂带土壤气汞、氡地球化学特征

根据汞、氡土壤气在断层上的形成机制,分析了玛曲断裂带土壤气中汞、氡地球化学异常特征,并依据异常判断了断层的位置、产状、性质.与断层的实际剖面所反映的断层规模与性质基本耦合.为评价活断层提供了有益的参考.     

干涉雷达人工角反射器技术

人工角反射器是众多雷达目标中的典型散射结构.本文介绍了人工角反射器技术应用在雷达干涉测量(CD-InSAR)的基本概念,描述了其中常用的二面角、三角锥形三面角、正方体三面角和长方体锥形三面角等四种典型的人工角反射器特点和最大雷达散射截面的计算机模拟,最后对人工角反射器制作和布设中的一些注意事项及主要应用领域进行了探讨.     

岩石滞后非线性弹性响应的物理模型

介绍了岩石滞后非线性弹性的几个物理模型。赫兹颗粒接触模型是具有多尺度和滞后特性的经典模型,它预测了岩石中强烈的非线性;软的粘结系统几乎决定了岩石的力学性质,粘结系统中的流体对非线性响应的贡献特别显著,但是目前还没有搞清楚粘结系统和孔隙流体究竟是如何影响非线性响应的;GL模型是一个基于金属位错的物理模型,这是滞后动力行为方面一个开拓性的微观模型;PM模型是一个基于岩石细观尺度的唯象模型,它对理解岩石滞后非线性的机制和尺度是很重要的。     

Invertebrate colonization of leaves and roots within sediments of intermittent Coastal Plain streams across hydrologic phases

Ecological flows between habitats are vital for predicting and understanding structure and function of recipient systems. Ecological flows across riparian areas and headwater intermittent streams are likely to be especially important in many river networks because of the shear extent of these interfaces, their high edge-to-width ratio, and the alternation of wet and dry conditions in intermittent channels. While there has been substantial research supporting the importance of riparian-stream linkages above-ground, comparatively less research has investigated below-ground linkages. We tested the hypothesis that riparian roots are colonized by invertebrates as a food source within stream beds of intermittent headwater streams. We compared benthic invertebrate assemblages colonizing three types of buried substrates (leaves, roots, and plastic roots) among three intermittent Coastal Plain streams, each with a different riparian management treatment (clearcut, thinned, and reference), over a 1-year period. Invertebrate density was significantly lower in root litterbags than in plastic roots litterbags, but neither differed from densities in leaf litterbags. Total invertebrate abundances, however, were significantly higher in leaf and root litterbags compared to abundances in plastic root litterbags. Invertebrate biomass and richness did not vary among substrates, but invertebrate density, abundance, and richness all declined from the wet phase (September–December) through the dry phase (June–August). Meiofauna and aquatic dipterans were the primary colonizing invertebrates during the wet phase. Relative abundance of terrestrial taxa increased during the dry phase, but their absolute abundance remained lower than aquatic taxa during the wet phase. Invertebrate composition did not differ among substrate types, but was significantly different among streams and time periods. Cumulative number of dry days, degree days, and redox depth all strongly correlated with assemblage structure as indicated by ordination scores. Our results suggest that subsurface invertebrates respond to leaves and roots as food sources, but assemblage composition is not substrate specific. Colonization of leaves and roots within stream beds by aquatic and terrestrial taxa supports the idea that headwater intermittent streams are important interfaces for the reciprocal exchange of energy and materials between terrestrial and aquatic ecosystems.     

Lateral stiffness estimation in frames and its implementation to continuum models for linear and nonlinear static analysis

Continuum model is a useful tool for approximate analysis of tall structures including moment-resisting frames and shear wall-frame systems. In continuum model, discrete buildings are simplified such that their overall behavior is described through the contributions of flexural and shear stiffnesses at the story levels. Therefore, accurate determination of these lateral stiffness components constitutes one of the major issues in establishing reliable continuum models even if the proposed solution is an approximation to actual structural behavior. This study first examines the previous literature on the calculation of lateral stiffness components (i.e. flexural and shear stiffnesses) through comparisons with exact results obtained from discrete models. A new methodology for adapting the heightwise variation of lateral stiffness to continuum model is presented based on these comparisons. The proposed methodology is then extended for estimating the nonlinear global capacity of moment resisting frames. The verifications that compare the nonlinear behavior of real systems with those estimated from the proposed procedure suggest its effective use for the performance assessment of large building stocks that exhibit similar structural features. This conclusion is further justified by comparing nonlinear response history analyses of single-degree-of-freedom (sdof) systems that are obtained from the global capacity curves of actual systems and their approximations computed by the proposed procedure.