饱和南京细砂永久应变势模型的试验研究

土单元永久应变势的预测模型是土动力学的重要研究内容之一。现有的土单元永久应变势模型没有反映振动孔压增长的影响,难以合理解释地震动作用引起的饱和砂土地基永久变形一般是由土层软化或再固结变形所致的机理。基于饱和南京细砂永久变形动三轴试验结果的有效应力状态分析,研究了试样的永久变形与振动孔压增长的关系,建立了一个能反映振动孔压增长影响的土单元永久应变势模型,给出了土单元永久应变势的数学表达式,分析了土单元永久应变势模型参数的影响因素。初步的验证性试验表明:模型预测与试验测得的试样永久应变势与振动孔压增长曲线比较接近,说明该模型具有一定的合理性。     

盾构隧道纵向等效弯曲刚度的简化计算模型及影响因素分析

盾构法隧道在国内的应用越来越广泛,早期建造的盾构隧道在工后沉降较大时出现较大的纵向变形问题,考虑隧道结构特征的设计模型及其刚度计算逐渐得到重视。在考虑管片螺栓等结构特征基础上,建立可考虑环缝张开的三维纵向结构计算模型。研究结果表明,与管片环接缝相关的影响因素,如螺栓的数量、螺栓的预紧力以及管片环宽度对纵向弯曲刚度有效率影响较大,随着纵向螺栓数量和管片环宽度的增加而线性增加,随着螺栓预紧力的增加而非线性快速增加,而管片环的横向弯曲刚度有效率影响较小。研究成果为盾构隧道纵向设计提供了关键参数。     

黄土塬煤层采空区弹性波多波波场特征

黄土塬已知煤层采空区的弹性波多波波场研究表明,反射波、散射波、天然源面波和人工源面波等各种弹性波波场显示出表征性特点。借助于这种波场特征,对于煤层采空区的地震勘探具有一定的指向意义。     

岩溶区客运专线桥梁桩基地质勘察方法与技术浅析

灰岩分布区岩溶发育易引发地面下沉、开裂,是地质灾害及路、桥、建筑物等工程设施的主要隐患,铁路客运专线桥梁工程一般选用桩基础的形式通过;岩溶作为一种常见的不良地质,其发育特征具有一定的规律性,但在较小范围的特定区内,其出现有着随机性,桥梁墩台勘察若依靠逐桩钻探不仅投入较大,也难以达到理想的效果。本文结合岩溶区客运专线勘察设计的经验,阐述了通过利用定测阶段钻孔和采用跨孔弹性波CT优化布置钻孔数量及位置的综合勘探方法,可以用最少的工作量则能全面、准确地揭示桥梁墩台地质情况,满足桥梁专业设计需求。     

Features of aerosol optical depth and its relation to extreme temperatures in China during 1980-2001

Based on Total Ozone Mapping Spectrometer (TOMS) monthly aerosol optical thickness (AOT) measurements in 1980–2001 a study is made of space/time patterns and difference between land and sea of AOT 0.50 μm thick over China,which are put into correlation analysis with synchronous extreme temperature indices (warm/cold day and night).Results suggest that 1) the long-term mean AOT over China is characterized by typical geography,with pronounced land-sea contrast.And AOT has significant seasonality and its seaso...     

海岸带区域SPOT卫星数据大气校正处理

将SPOT卫星自身近红外波段的数据作为气溶胶信息的来源,假设近红外波段暗像元受到大气影响较弱,卫星表观反射率近似等于地表反射率,且近红外波段暗像元与红光波段具备近似的线性关系,通过开源6S大气辐射传输模型的调试运行,并结合敏感性实验建立大气校正所需的查找表,最后通过一定的算法,实现了SPOT卫星Level_0级数据的大...     

Investigation of the thermodynamic processes of a floe-lead system in the central Arctic during later summer

Thermodynamic processes of a system involving a floe and a small lead in the central Arctic were investigated during the ice-camp period of the third Chinese National Arctic Research Expedition from 20 to 28 August, 2008. The measurements included surface air temperatures above the floe, spectral albedo of the lead, seawater temperatures in the lead and under the ice cover, and the lateral and bottom mass balance of the floe. The surface air temperature at 1.15 m remained below 0℃ throughout the observation period and sea ice had commenced its annual cycle of growth in response to autumn cooling during the study. The surface of the lead was frozen by 23 August, after which the spectral albedo of the thin-ice-covered lead in the band of 320-950 nm was 0.46 ±0.03, the seawater temperatures both in the lead and under the ice cover, as well as the vertical seawater-temperature gradient in the lead decreased gradually, and the oceanic heat under the ice was maintained at a low level approaching 0 W/m2. By the end of the measurement, the thickness of the investigated floe had reached its annual minimum, while the lateral of the floe was still in the melting phase, with a mean melting rate of 1.0 ±0.3 cm/d during the measurement, responding to an equivalent latent heat flux of 21 ±6 W/m2. The lateral melting of the floe had made a more significant contribution to the sea-ice mass balance than the surface and bottom melting in the end of August.     

北半球对流层厚度的时空变化特征

利用1948—2010年NCEP/NCAR逐月位势高度再分析资料、美国国家海洋局提供的1948—2010年逐月海温再分析资料,分别定义了1 000—500 hPa和500—200 hPa厚度,利用EOF、SVD等方法研究了北半球对流层厚度时空演变特征及其与大气环流和海面温度的关系。结果表明,冬季平均厚度EOF第一模态均具有北太平洋及附近高纬度亚洲大陆地区与北美大陆高纬地区反位相变化的特点,而夏季第一模态则是北半球范围内较一致的位相分布;冬、夏季平均厚度EOF第二模态均突出体现了欧亚大陆及附近地区与北半球其他地区反位相变化的特点;冬、夏季厚度场的变化形势与大气环流及海面温度具有密切联系。     

Ground-Based In Situ Measurements of Near-Surface Aerosol Mass Concentration over Anantapur: Heterogeneity in Source Impacts

Surface measurements of aerosol physical properties were made at Anantapur(14.62°N,77.65 °E,331 m a.s.l),a semiarid rural site in India,during August 2008-July 2009.Measurements included the segregated sizes of aerosolsas as well as total mass concentration and size distributions of aerosols measured at low relative humidity(RH<75%) using a Quartz Crystal Microbalance(QCM) in the 25-0.05 μm aerodynamic diameter range.The hourly average total surface aerosol mass concentration in a day varied from 15 to 70 μg m-3,with a mean value of 34.02±9.05μgm-3 for the entire study period.A clear diurnal pattern appeared in coarse,accumulation and nucleation-mode particle concentrations,with two local maxima occurring in early morning and late evening hours.The concentration of coarse-mode particles was high during the summer season,with a maximum concentration of 11.81±0.98μgm-3 in the month of April,whereas accumulationmode concentration was observed to be high in the winter period contributed >68% to the total aerosol mass concentration.Accumulation aerosol mass fraction,A f(=Ma/Mt) was highest during winter(mean value of Af～0.80) and lowest(Af～0.64) during the monsoon season.The regression analysis shows that both R eff and R m are dependent on coarse-mode aerosols.The relationship between the simultaneous measurements of daily mean aerosol optical depth at 500 nm(AOD500) and PM 2.5 mass concentration([PM2.5]) shows that surface-level aerosol mass concentration increases with the increase in columnar aerosol optical depth over the observation period.     

广州市外来人口弹性城镇化水平研究

流动人口的城市化问题历来是学界关注的焦点,经问卷调查和深度访谈获取广州市天河区外来人员异地城市化和弹性城镇化水平,发现其异地城市化水平低,城市化进程并没有一帆风顺,但弹性城镇化高,是中国城市化进程中没有出现贫民窟现象的重要原因。进一步分析发现,较高的经济门槛将广大外来人员拒在大城市门外,而较低的生活水平、越来越完善的设施、发展越来越迅速的城镇则向他们敞开大门:在现阶段,到沿海等大城市工作,而家人等安置在家乡城镇的弹性城镇化道路是收入不高的外来人员的理性选择和未来重要的归宿。