Stiffness of Frozen Soils Subjected to K0 Consolidation Before Freezing

The stiffness characteristic of artificially frozen soils subjected to K₀ consolidation at small strains are investigated at different initial confining pressure and frozen temperature by secant Young's modulus representing the soil stiffness. The influence of freezing on stiffness is investigated by comparing the behavior of frozen and unfrozen soils with similar conditions. It is observed that the frozen soils secant Young's modulus may decay with increasing strain after keeping a stage of constant value, the threshold yield strain was found to be approximately 0.05% for all tested conditions. On the other hand, the stiffness of studied frozen soils and its degradation was heavily response to the initial confining pressure amplitude and temperature fluctuation.     

冻土动强度特性试验研究

在围压为0.3～16 MPa,频率为2 Hz,温度为-4和-6℃条件下,通过一系列恒应力幅循环动荷载试验,发现冻土动强度的变化不仅跟破坏振次的大小有关,而且与围压、循环荷载作用下土体吸收的有效能量(损失能)之间也存在一定关系。根据损失能获得试样温度的变化,将冻土动强度与温度直接联系起来,表明振动荷载作用下损失能累积造成的温度额外升高是控制冻土动强度变化特性的主要因素之一。     

饱和正冻土多孔多相介质的理论构架

通过对冻土多孔多相微元体的平衡方程、各相成分之间的变形协调方程 ,推导出冻土体 (考虑土骨架与冰颗粒之间相互作用力---冻胀力 )的有效应力原理、正冻土单元的连续性方程及各相成分的能量转换与传递方程 ;在此基础上提出了正冻土的控制微分方程的理论框架 ,从而建立了在多孔固液介质的质量守恒方程与多孔多相介质的热、能守恒方程的基础上的全面考虑冻土中骨架、冰、水三相介质水、热、力与变形真正的耦合作用的数理方程 ,比当前国际流行的正冻土流体动力学模型、刚冰模型和热力学模型更全面地描述了正冻土的水、热、力与变形的实际状态     

青藏高原多年冻土区路基表面浅层地温探讨

冻土路基温度场是决定冻土路基稳定性的关键因素。在多年冻土区修筑道路工程后,由于工程施工的扰动作用,改变了地表与外界的热交换条件,打破了原有的热平衡状态,使冻土路基温度场变化十分复杂。鉴于青藏高原独特的自然地理环境,实测地温及气象资料获取的困难性,通过青藏铁路沿线有限的实测地温资料,建立了砂砾路面下路基水平表面浅层地温与理论太阳直接辐射强度之间简单的近似线性函数关系,并分析讨论了路基边坡表面浅层地温与太阳直接辐射强度之间线性关系较差的原因。     

Impacts of the Great Lakes on Regional Climate Conditions

Estimates of lake-induced spatial changes of six climate variables (precipitation, mean minimum and mean maximum temperatures, cloud cover, vapor pressure, and wind speed) were derived for the entire Great Lakes basin. These patterns were estimated by a comparison of maps of each weather variable using: (1) all regional climate data, and (2) regional data when observations within an 80-km zone around the lakes were removed. Results generally confirm expectations and prior findings, but point to inadequacies in data collection that limit a highly precise analysis. Lake effects are most noticeable in precipitation and temperature and vary considerably by season, time of day, and lake size. Greatest lake influences are found near Lake Superior where up to 100% more precipitation falls downwind of the lake in winter compared to that expected without its presence. During summer, all lakes cause a downwind decrease in rainfall of 10% to 20%. Mean minimum temperatures in the basin are higher in all seasons and over all lakes. Lake-induced reductions in mean maximum temperatures in the region are observed during spring and summer. Effects on cloud cover are greatest during winter and show increases of approximately 25% in areas downwind of Lakes Superior and Michigan. Conversely, the cool summertime waters of Lakes Michigan and Huron reduce cloudiness roughly 10%. Variations in vapor pressure are consistent with observed changes in temperature. Amounts in winter are estimated to be 10% to 15% higher across the center of the basin, but decrease by roughly 5% to 10% at many lake shore sites in summer. Seasonal wind speed data were considered to lack an appropriate number of quality long-term climate stations to determine spatial lake effects. Surface elevations, increasing east of the basin, complicated detection of effects due solely to the lakes.     

基于WebGIS的兰州市地质灾害群测群防信息化

群测群防技术是我国地质灾害防治的主要方法。针对目前地质灾害群测群防体系的低效问题,提出利用网络技术、通信技术和WebGIS技术建立基于WebGIS的兰州市地质灾害群测群防信息化系统。群测群防信息化系统是对地质灾害进行科学预测预警、减少灾害影响的一种重要平台。本系统由数据上传、灾情分析预测、信息发布和灾情浏览等功能组成,采用应用层、业务层和数据层三层分布式体系为系统框架,系统模型库中包括地质灾害空间预报模型和地质灾害时间预报模型,采用关系型数据库SQL Server2005为后台数据库,通过.NET开发平台完成系统的开发。系统运行结果表明,该系统运行稳定,能有效地为地质灾害群测群防体系中的各级用户服务并提供技术支持,具有广泛的应用前景。     

地表通量对模型参数的不确定性和敏感性分析

基于2007年12月22日~2009年12月31日黑河流域阿柔冻融观测站的气象驱动数据,利用通用陆面模型(Common Land Model,CoLM)模拟的地表通量结果,研究地表通量对模型参数(叶面积指数、地表反照率和植被覆盖度)的不确定性与敏感性。结果表明,叶面积指数、地表反照率和植被覆盖度对地表感热和潜热通量不同组分的影响存在较大的差异。其中,植被层的感热和潜热通量对叶面积指数的敏感性程度较高,敏感系数均达到0.7以上;与潜热通量相比,感热通量对反照率更加敏感,土壤感热、植被感热和总感热通量对反照率的敏感系数分别达到-0.96、-0.97和-0.66,而土壤潜热和总潜热通量对地表反照率的敏感系数仅为0.1左右;植被潜热通量对植被覆盖度的敏感性程度很高,敏感系数范围为0.92~0.96,而土壤感热通量对植被覆盖度最不敏感,敏感系数只有0.18左右。     

Thermal Interaction between Permafrost and the Qinghai-Tibet Railway

Measures were taken to protect the thermal regime of the roadbed embankment after construction and to lower permafrost temperatures in the rich-ice and warm permafrost regions along the Qinghai-Xizang Railway. However, these measures were taken only for some sections of the railway, leaving many sections unprotected. This article addresses those areas where no measures were taken and presents analysis of the variation of soil temperatures under the embankment in seasonal frozen soil areas, degrading permafrost areas, and warm and cold permafrost areas. The results show that soil temperatures, maximum seasonal freezing depth, and the permafrost table under the embankment differ according to the different frozen soil areas after embankment construction. In seasonal frozen soil areas and degraded permafrost areas, the seasonal frost layer remained frozen the next year under the shaded shoulder of the embankment. In degrading permafrost areas, a thaw layer between the permafrost table and the bottom of the seasonal frost formed under the embankment. In warm permafrost areas, the permafrost table under the embankment was unstable and soil temperatures near the permafrost table showed an obvious increasing trend. In cold permafrost areas, the permafrost table under the embankment was clearly raised and temperature lowered in the soil near the permafrost table, which is advantageous to permafrost thermal stability under the embankment. In particular, the differ-ence in solar radiation from the slope exposed to the sun to the shady slope of the embankment is responsible for the difference in the soil thermal regime and the permafrost table, which potentially can affect roadbed stability.     

Effects of the accumulation of the rare earth elements on soil macrofauna community

The accumulation of rare earth elements(REEs)in soil has occurred due to the pollution caused by the exploitation of rare earth resources and the wide rare earth fertilizers in agriculture.The accumulation of REEs has a toxic effect on the soil macrofauna community.12study samples were collected near a mine tailings dam with a large amount of REEs by distance gradient sample method.The total concentration of REEs was analyzed and the results were compared with that of the sample from a control site.The effects of the amount of REEs in the soil on the soil macrofauna community were also analyzed.The results showed that the accumulation of REEs in soil was significant in the study area and its concentration was strongly correlated with the distance from the pollution source.One-way ANOVA analysis indicated the significant differences in soil macrofauna communities among the different sites.The ordination obtained through the redundancy analysis demonstrated that the concentration of REEs and the total nitrogen,total potassium and pH,had affected the soil macrofauna community.A small amount of REEs in the soil can promote the diversity of soil macrofauna,but a large amount of REEs can reduce its diversity.The insect groups of Carabidae and Dermaptera were comparatively sensitive to the concentration of REEs in soil,and could be used as an indicator of soil pollution of REEs.However,the Formicidae and Stibaropus formosanus exhibited a high tolerance to REEs in soil.We believe that it is very important for the soil environment protection to strictly control the application of the rare earth fertilizers in agriculture in China.     

异质性地表土壤冻融循环监测网络的优化采样设计-以黑河祁连山山前地区为例

在黑河祁连山山前地区建立分布式的土壤温度/水分传感器监测网络,准确获取异质性地表的遥感像元真值,用于地表冻融状态分类及土壤水分定量反演算法的发展完善和真实性检验,以及两者的降尺度研究均具有重要意义。传感器监测网络节点的空间布局直接影响观测有效性及其数据质量,一种基于异质性地表的均值估计方法被用于空间节点的优化采样设计：即以地表温度为目标变量,将研究区划分为相对均质的若干层(子区域),计算各层及总体的变异函数参数作为代价函数的输入,通过最小化目标变量的估计方差,实现传感器网络节点在各层的空间分布,准确地捕捉区域内部的异质性。结果表明,分层后各层的异质性相对于总体都有所下降,优化的节点空间布局具有较好的属性代表性,对于异质性较强的局部区域,有较高的样本密度。