强降雨下基于Green-Ampt模型的边坡稳定性分析

降雨入渗分析方法直接影响降雨型滑坡的预测与防范。Green-Ampt（GA）模型物理意义明确、参数较少,在降雨型滑坡分析中逐渐得到了重视,但该方法忽略了湿润层非饱和层的存在以及饱和层渗流而影响计算精度。针对以上不足,基于GA模型,建立了适用于边坡并且能综合考虑湿润层土体含水率分布情况与饱和层内平行于坡面渗流作用的降雨入渗分析（LSGA）模型,并提出了该模型下边坡稳定性系数表达式。结果表明：对于不考虑分层的无限长边坡,LSGA模型可简化为GA模型,说明GA模型是LSGA模型的一个特例;与LSGA模型相比,GA模型在失稳深度和时间上有较大延缓;饱和层渗流作用对湿润层特性影响较小,对边坡稳定性影响较大;相反,坡体长度方向尺寸效应则对湿润层特性影响明显,而对边坡稳定性影响较小;利用LSGA模型和稳定性评价方法得到的结果与模型试验揭示的现象基本吻合,证明了该方法有较好的精确性和可靠性。     

基于检查信息分层的“粗反馈”最终检查模式

“二级检查一级验收”作为测绘单位质量控制的基本制度,在成果质量保障中发挥着重要作用,但是部分单位因整改质量不高,造成在最终检查环节上执行不顺畅。通过质检实践,总结了常规最终检查模式下整改中存在的问题,针对基础测绘项目中整改效果不明显的实际情况,在常规检查模式的基础上提出了基于检查信息分层的粗反馈最终检查模式,并通过应用实例验证了该模式在提升整改质量中的有效性和实用性。     

Spatial and temporal variation of picoplanktic cyanobacteria population in a density stratified estuary,and the introduction of a cellular gradient number

Spatial and temporal variations in the distribution of the marine picoplanktic cyanobacteria population and mixing conditions were found in the Ebro River estuary outflow to the Mediterranean Sea in Spain. Six sampling surveys were undertaken between July 1999 and February 2000 for distances up to 15 km from the river mouth. Measurements were taken of flow velocity, salinity, temperature, depth and picocyanobacteria (PCB) abundances. Gradient Richardson (Rig) and Reynolds (Re) numbers were determined to evaluate hydrodynamics. In summer, large values of Rig arise from the small flow rates, and small values of velocity shear between the surface fresh water layer and the bottom saline layer; conversely, in winter the large flow rates and attendant large velocity shears between the layers give rise to small values of Rig. Flow conditions in the fall are an intermediate case between the summer and winter cases. Vertical abundance distributions were resolved through the river water, interfacial region, and the bottom salt wedge; longitudinal gradients of PCB abundances were also resolved. Seasonal differences in the PCB abundance values were observed. Analysis of cell numbers (C) showed that the variable dC/dS, the dependence of cell number upon salinity gradient (dS) was critical. A non-dimensional number; the cellular gradient number (Cg) is introduced. Cg has useful biological interpretations that can potentially be included in ecological modeling. For example, Cg = 1 pertains to perfect adaptability of the organism to adjust to changing environmental conditions, whereas Cg = 0 describes total mortality. For a system with strong advection there is insufficient time for cells to adapt to the changing environment, and so those cell counts are unchanged. This is the case for the Ebro estuary in winter as advection of salinity (and hence PCB abundance) dominates the other loss processes for large flow rates.     

Thermohaline convection in flowing groundwater

Geothermal activity creates destabilising temperature gradients which are significant in some aquifers. Usually, in such aquifers stabilising salinity gradients also exist. The combination of temperature and salinity distribution in the aquifer may induce various types of hydrodynamic instabilities which were identified in a previous article. The present article concerns the effect of anisotropic characteristics of the hydrodynamic dispersion on the growth of instabilities in the aquifer. Three different mechanisms may lead to instability of the flow field: (a) buoyancy forces may induce convection currents; if the difference between the convection velocity of salt, due to the hydraulic gradients, and that of heat is negligible, then this mechanism is generally most effective in planes parallel to the hydraulic velocity of the fluid (velocity due to the hydraulic gradient); (b) the difference between heat and salt effective diffusivities may lead to overstability; this mechanism is most effective in planes perpendicular to the hydraulic velocity; (c) the difference between the convection velocity of salt and that of heat may induce oscillations which are most effective in planes parallel to the hydraulic velocity. The growth of instabilities in an aquifer of unlimited length is different from their growth in an aquifer of limited length. In the latter thermohaline convection develops in planes perpendicular to the hydraulic velocity, whereas in the former it develops in planes forming an angle θ with the hydraulic gradient. The development of convection cells in the flow field is identified by numerical experiments. These experiments identify the convection cell length and the angle formed between the thermohaline convection plane and the hydraulic gradient.     

层化海洋中的二阶波散射作用问题

引入Stokes有限振幅水波的多色波作用机制 ,采用二层层化海洋模型 ,分析了层化海洋中非线性波对结构的散射作用问题。提出了二层海洋中二阶水波散射条件的数学表达式 ,进而推导了二层海洋中二阶波对一般型圆柱散射作用的格林积分解式 ,并给出了对解式中自由面及分层界面无限积分的递推算式。     

层状岩体三维可视化构模与数值模拟的集成研究

由于数据结构的差异,用于岩土工程三维可视化的网格与用于数值模拟的计算网格之间存在本质差异,如何通过两种网格的共享实现三维地质模型与数值模拟之间的集成是岩土工程建模的重要内容。在对层状岩体三维可视化网格与数值模拟网格的特点进行剖析的基础上,提出了基于松散模式的三维规则格网与FLAC3D基本元素之间的转化方法,从理论上实现了“可视”与“可算”的结合。将其应用于我国某海底隧道的选线研究中,证明了该方法的合理性和有效性。     

基于多元数据的中国地理空间疫情风险评估探索——以2020年1月1日至4月11日COVID-19疫情数据为例

新冠肺炎（COVID-19）在空间上具有一定的传播风险,对城市的安全健康构成了威胁,防止疫情传播成为紧迫的任务。在2020年1月1日至4月11日,COVID-19疫情经历了发生、迅速发展和趋于稳定的发展过程,利用初期的COVID-19数据进行宏观层面的疫情风险评估,为防疫控制措施提供一定的参考。因此本研究基于行政区划、定点医院、疫情小区以及道路交通等多元数据,在宏观层面提出并构建全国地理空间疫情风险性评估,对疫情风险分布探讨的同时进行评估效果验证,并根据构建指标揭示影响风险的因素及其机理,主要结论： ① 地理空间风险评估具有有效的可行性。② 地理空间疫情风险分布全局Moran's I指数为0.758,具有显著的空间集聚特征。同时,不同的省区市之间的局部LISA值呈现空间差异性,其中高—高聚类省区市占比全国25.81%,风险程度较高,主要分布在湖北、河南、湖南、江西、安徽、浙江、江苏、上海,低—低聚类省区市占比全国9.68%,风险程度较低,主要分布在青海、西藏、新疆。③ 地理空间疫情风险分布与地理区位、道路交通、医疗卫生、疫情现状指标均存在一定的相关性。根据统计学的Pearson相关性分析,其相关指标R ²存在差异,在数值上由高到低依次为疫情现状、地理区位、道路交通、医疗卫生,在属性上其相关因子存在正负2种效应,地理空间疫情风险与武汉市地理距离、定点医院密度以及居民-医院地理距离呈现显著的负相关,其R ²分别为0.813、0.545、0.436,与铁路网密度、公路网密度以及疫情小区密度呈现显著的正相关,其R ²分别为0.751、0.792、0.825。④ 地理空间疫情风险的构成因素错综复杂,其受到多种因子的共同作用,根据空间分层异质性分析,不同因子之间均存在交互作用,其中居民—医院地理距离与公路网密度、铁路网密度交互作用较强,q值分别为0.9842、0.9837。本研究在宏观层面为城市管理中重大疫情的空间资源分配以及区域空间的联防联控策略提供了相应的依据。     

中国机场总规模分层优化测算研究——基于人口覆盖角度

适宜的机场数量规模是中国机场发展战略和中长期规划的重要研究内容.传统的定性方法难以满足规划的需求,而采用合理的定量测算方法求解中国机场规模对未来的规划更具有参考意义.本文根据不同等级需求点的可达性要求,设置不同的机场服务半径,并规定新建机场腹地人口规模,通过制定位置集合覆盖模型(Location Set Covering Problem,LSCP)和最大覆盖选址模型(Maximal Covering Location Problem,MCLP)的综合修正模型,对中国机场规模进行分层测算.结果表明,不同地、县级需求组合下,在地面道路距离100 km范围内覆盖中国95％总人口时,中国机场规模以370～385个为宜.其中,中部、西部地区地级机场与县级机场均需建设;东北地区需要多新建地级机场,黑龙江省还需新建少量县级机场;东部地区新建少量地级机场以及适量县级机场.对于本文结果中出现的首层地级测算中地级市没有布局机场,但在第二层县级测算时下属县却布局机场,以及同一地级市布局多个县级机场的现象,认为是合理的.测算结果对未来民航机场规划具有一定参考价值.     

Seasonal distribution of organic matter and copper under stratified conditions in a karstic,marine, sulfide rich environment (Rogoznica Lake,Croatia)

Closed, isolated small systems, as the representatives of a “unique-environmental feature”, are valuable natural laboratories for studying different biogeochemical processes. The saline Rogoznica Lake (“Dragon Eye”), situated on the Eastern Adriatic coast is such a system (10 276 m², 15 m deep) typical of many stratified, sulfide rich water bodies. The depth of mixolimnion changes seasonally and it is greatly influenced by meteorological conditions, i.e. temperature and rainfall. Vertical mixing usually occurs during winter when cold, oxygen-rich water from the surface sinks downwards.     

Distribution of trace metals in anchialine caves of Adriatic Sea,Croatia

This study presents results of the first comprehensive research on ecotoxic trace metals (Cd, Pb, Cu and Zn) in aquatic anchialine ecosystems. Data show the influence of hydrological and geological characteristics on trace metals in highly stratified anchialine water columns.