Effects of riverbed scour on seismic performance of high-rise pile cap foundation

To explore the seismic performance of a high-rise pile cap foundation with riverbed scour, a finite element model for foundations is introduced in the OpenSees finite element framework. In the model, a fiber element is used to simulate the pile shaft, a nonlinear p-y element is used to simulate the soil-pile interaction, and the p-factor method is used to reflect the group effects. A global and local scour model is proposed, in which two parameters, the scour depth of the same row of piles and the difference in the scour depth of the upstream pile and the downstream pile, are included to study the influence of scour on the foundation. Several elasto-plastic static pushover analyses are performed on this finite element model. The analysis results indicate that the seismic capacity (or supply) of the foundation is in the worst condition when the predicted deepest global scout depth is reached, and the capacity becomes larger when the local scour depth is below the predicted deepest global scout depth. Therefore, to evaluate the seismic capacity of a foundation, only the predicted deepest global scout depth should be considered. The method used in this paper can be also applied to foundations with other soil types.     

阿拉善高原荒漠植被组成分布特征及其环境解释 Ⅲ.植物功能群多样性对环境因素的响应

采用水分生态型(包括旱生植物、旱中生植物、中生植物和湿生植物)、生活型(灌木、半灌木、多年生草本和一二年生草本)和植物主要光合途径(C3和C4)等方法将研究区的植物种类进行了功能群(functional groups/types)划分,为进一步认知荒漠生态系统的结构、功能和过程提供了分析基础。植物功能类群相对集中是阿拉善荒漠植被组成的一个重要特点,这主要和植物趋于旱化、生态型相对简单密切相关。按优势功能群依次为:PFTs1(旱生C3一二年生草本)、PFTs2(旱生C3多年生草本)、PFTs3(旱生C3灌木)、PFTs4(旱生C3半灌木)、PFTs5(旱生C4一二年生草本)、PFTs7(旱生C4灌木)和PFTs8(旱生C4半灌木)。气候、土壤理化指标决定着植物功能类群的分布。其中年均降水量、湿润系数决定着植物的生态型、生活型在水平地带上的分布特征,同时,也影响C3和C4植物(海拔梯度上)的分布。土壤容重、砂粒、粉粒含量决定着植物生活型特征,而土壤pH值、Cl-、SO42-和Ca2+决定着植物水分生态类型的空间分布。这些结果揭示了极端干旱区植物对胁迫环境响应的多样性,是对极端环境条件下如何理解生物多样性维持机制和可持续发展的较好生态学解释。     

基于GIS的中国可持续人居功能分区评价(英文)

在中国1km×1km栅格尺度人居环境自然适宜性分类评价和分县尺度人口空间集聚程度分级评价的基础上,结合中国分县资源环境承载力和区域经济发展水平和发展潜力,确立了中国可持续的人居功能分区评价模型,提出了中国可持续发展的人居功能分区方案。研究表明:中国可持续的人居功能分区空间分布呈现东南半壁优于西北半壁的格局;人居功能强可持续地区面积约139.75×104km2,占国土面积的14.66%,相应人口4.3亿,接近总人口的1/3,主要分布在东南沿海、长江中下游地区、四川盆地、黄淮海平原以及东北平原的部分地区;人居功能较强可持续地区面积约193.61×104km2,占国土面积的1/5,相应人口3.2亿,接近总人口的1/4,主要分布在三江平原、辽河平原、山东半岛等地;可持续地区面积210.19×104km2,约占国土面积的22%,相应人口3.7亿,占总人口的28.24%,主要分布在呼伦贝尔高原、黄土高原和云贵高原等地,零星见于藏东南谷地和柴达木盆地等地区;较弱可持续地区,面积约145.85×104km2,占国土面积的15.30%,人口1.4亿,约占总人口的11%,零散分布于黄土高原、川滇高原和云贵高原的部分地区;弱可持续地区面积约263.86×104km2,约占国土面积的27.68%,相应人口0.4亿,接近总人口的3%,主要分布在青藏高原、西北荒漠以及川滇高原北部地区。     

城市热岛效应热点问题研究进展

概述了国内外城市热岛效应研究热点及不足,探讨了时空替代性、评价指标合理性、模拟空间尺度适宜性及理论与应用研究相结合等问题,指出未来城市热岛效应研究应注重新方法与新思路的集成、城市群热岛效应监测、城市热岛与全球异常环境要素间的生态关联性、缓解城市热岛效应的生态途径与技术方法。     

宣城市陈山滑坡群稳定性分析

宣城市陈山滑坡群由四处滑坡组成,其中Ⅰ、Ⅱ、Ⅲ号滑坡已发生滑动,造成坡下橡塑厂房倒人伤重大灾害发生,Ⅳ号滑坡雏形目前已经形成,至今未发生大规模的滑动,却一直存在缓慢下滑的迹象,已处于严重不稳定状态,如遇强降水的引发,将可能产生大规模突发性滑坡,直接威胁山下敬老院、橡塑厂等人员生命财产安全。本文论述了陈山滑坡群的形成条件、特征及危害,对Ⅳ号滑坡的稳定性进行了分析,并提出了防治对策。     

用于铂族元素分析的中外地质标准物质

标准物质作为地质分析的计量标准,在分析质量监控、仪器校准、方法评价和仲裁分析中发挥着重要作用。铂族元素分析一直是地质材料分析中最棘手的任务之一,铂族元素标准物质研制困难,数量少,严重影响了对铂族元素分析方法的评价和分析数据的质量监控,成为铂族金属矿产资源勘查、评价和相关研究工作的瓶颈。收集了中国及国际上现有的34个铂族元素标准物质和52个其他地球化学标准物质中的101个铂族元素定值数据。为便于使用也收集了这些标准物质中其他元素的含量信息,给出了铂族各元素按含量大小排列的信息简表以方便选择。充分利用这些标准物质对促进铂族元素分析方法研究,保证铂族元素分析数据质量,提高中国和世界铂族金属矿产资源勘查、评价及研究水平具有重要意义。     

Antiquity and long-term morphological stasis in a group of rove beetles (Coleoptera: Staphylinidae): Description of the oldest Octavius species from Cretaceous Burmese amber and a review of the “Euaesthetine subgroup” fossil record

The Staphylinine group of rove beetle subfamilies is a significant animal radiation, and one subordinate monophyletic clade – the ‘Euaesthetine subgroup’ – includes around 3000 species in subfamilies Euaesthetinae and Steninae and has a fossil record dating to the Early Cretaceous. Detailed morphological study of a new well-preserved Cretaceous Burmese amber fossil revealed strong evidence consistent with its taxonomic placement in the euaesthetine genus Octavius. We thus describe Octavius electrospinosus sp. nov., the first Cretaceous record of the genus and of the tribe Euaesthetini. Previously, the oldest records of Octavius and Euaesthetini were from the Eocene (Baltic amber) and discovery of O. electrospinosus sp. nov. therefore nearly doubles the minimum lineage age of Octavius, increasing it by 50 million years. We also briefly review the known Euaesthetine subgroup fossil record and tabulate summary data for all previously described fossils. All are placed in extant genera, and have visible diagnostic generic-level characters including some putative synapomorphies as judged by recent phylogenetic work. Including O. electrospinosus sp. nov., there are now four known Cretaceous species, all of which belong to either Octavius, Nordenskioldia, or Stenus. To explain the long-term morphological stasis in this group of rove beetles, we suggest that the continuous presence of mesic habitats may have buffered these lineages from strong selection for morphological change. Considering the fossils along with phylogenetic hypotheses we suggest the Euaesthetine subgroup originated in the Late Jurassic– Early Cretaceous and the Staphylinine group in the Early Jurassic. We emphasize the derived status of Cretaceous fossils in assessing possible divergence times and the significance of the pre-Cretaceous taphonomic bias for restricting more robust estimates. Further detailed morphological study of available fossils in a phylogenetic framework is badly needed to clarify the phylogenetic positions of these taxa.     

组合荷载下超大群桩受力变形模型试验研究

李子沟特大桥是内昆线上的重点工程 ,采用了超大群桩基础。为了进一步完善对超大群桩基础的力学行为的认识 ,应用模型试验分析了在组合荷载作用下超大群桩基础的内力分布特点、群桩的承载性状和受力变形特性。试验结果表明 ,最大弯矩发生在与承台连接附近的桩身处 ,弯矩沿桩身向下随荷载由线性或非线性递减。对于组合加载与水平纵向加载 ,弯矩的极值、沿桩身的变化趋势和受荷载的影响范围不同     

Centrifuge modelling of raked piles

Inclined piles are prohibited by many codes in seismic areas. Nevertheless the battered effect has not yet been clarified because very few data are available. The present work is a comparison, at reduced scale in the centrifuge, of the response of two simplified pile groups: a 1 × 2 vertical piles and 1 × 2 pile group with one inclined pile. Two configurations are considered: end-bearing and floating pile group, both with pile heads rigidly fixed with a massive cap. First, repeatability tests under horizontal cyclic loading were performed on both floating pile groups. Secondly, repeated horizontal impact tests were performed on both end-bearing pile groups. These impact tests, which highlight the influence of inclined piles on the inertial response of a group, are a first step for the more complex analysis of the performance of such groups under seismic loads where inertial and kinematic interactions are combined. The first part of this work revealed the influence of sand structure around the inclined pile tip on the repeatability of the tests performed on floating pile groups. The second part highlighted differences in the dynamic response between the two end-bearing pile groups through measurements of the pile cap acceleration, the bending moment profile and the axial load in the piles.     

隧道开挖对邻近桩基工作性能的影响研究

隧道开挖对邻近既有建（构）筑物桩基乃至整个建（构）筑物的稳定与安全带来不同程度的影响。采用大型通用有限元分析软件ABAQUS,结合工程算例,模拟隧道开挖对邻近桩基工作性能的影响。首先分析了当邻近桩基与隧道竖向轴线之间的水平距离和桩长变化时隧道开挖所引起的单桩反应变化规律;在此基础上,研究了隧道开挖对邻近群桩的影响,对比分析了群桩中基桩与单桩的工作性能差异,得出了一些对工程建设有意义的结论。