X 波段双极化雷达对云中水凝物粒子的相态识别

人工影响天气研究需对云中降水粒子的相态和分布结构进行准确识别,以便提高人工影响天气作业效率.中国科学院大气物理研究所的车载X波段双极化雷达可提供与云中降水粒子大小、形状、相态等特征密切相关的4个极化参数:反射率因子、差分反射率、差分相移率、水平和垂直极化相关系数.利用这4个极化参数加上环境温度作为5个输入参量,建立了降水粒子相态模糊逻辑识别算法,识别的降水粒子有10种:毛毛雨、雨、湿霰、干霰、小雹、大雹、雨加雹、湿雪、干雪、冰晶.利用此雷达的实际观测资料,并与地面和飞机空中实测资料对照,对我国南、北方地区观测的降水天气过程进行分析,结果表明:建立的模糊逻辑算法对云内水凝物粒子的相态识别分类合理.     

1960~2011年中国日降水集中程度的时空变化特征

利用1960~2011 年的日降水资料,计算降水集中指数（Concentration Index,CI）,分析中国区域降水集中程度的空间分布及时间变化特征,得到以下主要结论：CI 指数可有效描述我国日降水集中程度;我国CI 指数介于0.575 与0.750 之间,平均为0.652,总体呈现出东部大、西部小,夏季大、冬季小的特征;44.17%站点的CI 指数表现出增加趋势,55.83%的站点表现出减少趋势,其中10.36%站点的变化趋势通过95%信度水平的显著性检验,CI 指数显著增大的站点主要分布在西北、华中和西南地区,显著减小的站点主要分布在东北、华北、东南沿海及青藏高原东部等地区;3~5 年是各子区域CI 指数变化的主要周期,与对应区域降水量的变化周期较一致;1970 年左右和2000 年左右是显著周期性变化出现较集中的时间段。     

采油平台淘空防护措施的试验研究

通过室内试验,研究了采油平台的冲淘机理和防护措施,对仿生海底、仿生林、抛石块、抛石子袋等防冲淘措施进行了方案设计和试验,完成了导管架式、桶形基础式、沉垫式3种采油平台的冲淘及防护措施试验研究,提出和完善了多层次抛石防护技术,并将研究成果成功应用于海上防护工程.提出的研究思路以及得到的研究成果,对解决胜利油田海区粉土地基的防冲淘难题具有重要指导意义.     

日照帆船港工程泥沙运移物模试验研究

通过动床波浪输沙模型试验,研究了日照帆船港3种设计方案的泥沙运移情况.通过分析试验结果,预报了常浪和大浪作用下工程区的冲淤分布.结果表明,日照帆船港工程的建设不会对邻近海岸产生大的影响,航道和港池均不会出现大的淤积.但是,为防止堤脚冲刷,应在挡沙坝堤脚处设置护脚结构.     

单元畸变对动力有限元方法计算精度的影响

在有限元分析中,由于求解区域或边界的不规则,有限单元的划分会产生畸变单元。本文通过数值试验分析了有限单元畸变对动力有限元计算精度的影响,结果表明:长宽比畸变对动力有限元计算精度没有影响;当斜交角不小于30°时,斜交角对动力有限元计算精度的影响可忽略;锥度对动力有限元计算精度有影响,锥度越大,锥度对动力有限元计算精度的影响越大。     

徐州市棠张镇饱和粉土液化性能试验研究

徐州市棠张镇高速铁路路基的粉土粘粒含量少于1．5％、粉粒含量约为80％,在强烈地震作用下存在着液化可能性,为了分析该路基粉土的液化特性,进行了多组振动三轴液化试验。对试验结果进行分析发现,该地区的粉土振动孔压发展模式与Seed提出的用反正弦三角函数拟合的砂十振动孔压发展模式不同,可以用双曲线进行拟合。采用最大往返剪切作用面上的应力条件确定了该地区的孔压发展模式的拟合参数,为该地区粉土地震液化动力计算分析提供了所需的地震孔隙水压力增长模型。同时,本文指出粉土的密度和结构是振动孔压发展的重要影响因素。     

高压喷射注浆技术在白龟山水库顺河坝防渗墙围井试验中的应用

本次围井高喷试验,选用三重管摆喷法处理方案,施工采用两序施工方法.砼墙体连续均匀,孔与孔之间连接较好,其防渗、强度、厚度均能满足设计要求.     

Stability Study of a Tide Embankment Subjected to Sea Level Variations Using Centrifugal Model Tests

To investigate the behavior of dredged-sea-sand fill compacted inside tide embankments with a damaged geosynthetic mat, centrifugal model tests and numerical simulation were conducted, both considering variations in sea level. The results from the three centrifugal model tests demonstrate that the subsidence of the dredged-sea-sand fill inside tide embankments with a damaged geosynthetic mat was strongly affected by the loss of dredged-sea-sand into the filter layers with large particles and a decrease in the bearing capacity of the filter layers with small particles. In addition, a comparison of the test and simulation results confirms that the loss of sand into the filter layer and the subsidence of the dredged-sea-sand fill were well reproduced by the numerical simulation.     

Evaluation of Liquefaction Potential Index Along Western Coast of South Korea Using SPT and CPT

For South Korea, liquefaction potential along the western coast has not been widely assessed because South Korea is considered to be a low seismic hazard. However, recent earthquake events and historical records indicate that the seismic hazard of South Korea should not be ignored. Moreover, as artificial fills are extensively used along the western coast for development, liquefaction evaluation of the soils in this area is necessary. In this paper, we present: (1) the seismic characteristics of the study area; (2) procedures for evaluating liquefaction potential, focusing on the liquefaction potential index (LPI) approach; and (3) LPI distributions at several representative locations along the western coast of South Korea under various seismic scenarios. The liquefaction potential index represents the liquefaction potential over the upper 20 m of a boring or sounding. Using cone penetration test (CPT) and standard penetration test (SPT) data from two coastal sites, we compare and discuss CPT-based and SPT-based LPI values, particularly values computed in nonplastic, silt-rich soils. In these soils, it appears that the CPT yields lower liquefaction resistance, resulting in large LPI values. Finally, discussion and suggestions are provided for CPT- and SPT-based liquefaction assessment of low plasticity and high fines content soils.     

Experimental Study on Complete Consolidation Behavior of Hong Kong Marine Deposits

The time-dependent feature of soft soils has gained intensive attraction in recent years. Due to the high water content and viscous property, the Hong Kong marine deposit (HKMD) frequently poses a challenge to geotechnical practice, particularly to the reclamation in Hong Kong. A key issue related to reclamation design, foundation construction and maintenance is excess settlement/deformation of the ground. Formation of HKMD typically goes through sedimentation and self-weight consolidation. A series of one-dimensional settling column consolidation tests, together with conventional oedometer tests were conducted on the HKMD. By normalizing parameter in settling stage, a unique global relationship of effective stress, σ_z′ and strain, ?_z could be established. Results reveal that the settling curve and settling rate are significantly affected by the sediment concentration in self-weight consolidation. After the primary self-weight consolidation, the settling rate is reduced in the “secondary self-weight consolidation.”