东南海岸带海相软土的Cc~n关系

收集整理了国内学者给出的我国东南海岸带不同地区（上海、连云港、广州、深圳、浙江沿海、渤海湾）海相沉积软土的8个Cc与n统计关系式,并根据公开发表的资料增加了这些地区以及沿海其他地区（天津、温州）260个的Cc～n数据,进行了东南海岸带软土的统一分析。发现Cc～n间存在较好的线性关系,具体关系大致可以分为陡变型和缓变型2类,缓变型与国外一些学者给出的统计结果较为接近。本文还对比了两种质量的上海软黏土的试验结果,分析了土样扰动对Cc～n统计关系的影响。     

利用GPS三频数据计算电离层垂直总电子含量变化率

研究了通过采样间隔为1 s的GPS三频载波相位观测数据计算1 Hz电离层垂直总电子含量变化率（RVTEC）的方法,推导了直接采用双频载波相位观测量计算RVTEC的公式,对一般空间环境与电离层活动剧烈两种条件下L1L2、L1L5、L2L5三种载波相位组合计算的RVTEC进行了一致性分析,给出了通过三频载波相位观测数据计算电离层RVTEC的修正方法,比较了X射线太阳耀斑期间RVTEC与由传统方法计算的总电子含量变化率（ROT）响应,在双星串飞编队测高模式下对计算方法进行了应用.结果表明,L1L2、L1L5两种组合之间的一致性较好,由L1L2、L1L5组合计算的RVTEC的中误差约为0.004 TECu/s,RVTEC较ROT更能体现TEC变化的细节,在双星串飞编队测高模式下海面高梯度的计算中,电离层延迟之差可以忽略.

     

上海地区基于静力触探的液化判别分析

上海地区(及其他软土地区)以静探触探作为岩土工程勘察的主要原位测试手段,积累了大量的工程数据,其结果稳定可靠,重现性好,具客观性。采用上海地区静探液化判别方法,对收集的大量资料进行统计分析,以期通过静探Ps值快速、简单地作出地基土是否液化的初步判断,有效指导勘察设计工作。     

煤层气储层物性预测的AVO技术对地震纵波资料品质要求的探讨

煤层的含气性及渗透性可以利用纵波AVO技术及基于各向异性理论的方位AVO技术进行研究.煤层气属于吸附气,储层厚度较薄,地震异常响应较弱,对地震资料的品质及其携带的信息量提出了更高的要求.本文对AVO与方位AVO反演理论的近似条件及模型试算结果进行了分析,提出了对地震纵波数据信噪比、入射角、偏移距分布及方位角分布等参数的要求:1.观测系统设计及野外采集时应保证地震波的有效入射角在0.～30.或更大范围内,偏移距应大中小均匀分布,避免过于集中或缺失.2.地震数据应有足够宽分布的方位角,煤层气地震勘探中应选择宽方位观测系统.3、地震资料信噪比应足够高.     

粘粒含量对甘肃黄土抗液化性能的影响

甘肃黄土是介于砂土与粘土之间的一种过渡性土壤,它具有砂土的某些特性,又具有粘土的某些特性,存在一定的粘塑性。通过对含粘粒黄土所做的实验研究,包括：粘粒含量不同的原状土样所做室内的动三轴试验、激光粒度分析试验、化学分析和电镜扫描,试验结果分析对比后,得出了含粘粒黄土抗液化性能的特性。并得出以下结论：（1）粘粒颗粒级配不同,也引起黄土动力稳定性的变化;（2）液化强度与粘粒含量并非呈单调增加关系,无论固结压力如何,粘粒含量Pc=15％左右时抗液化性能最低;（3）粘粒含量为一定值时,液化孔压比偏大,偏离这一值时,液化孔压比偏小。     

地基微波辐射计探测在黄河上游人工增雨中的应用

利用2003、2004年夏秋季在青海省河南县的地基双频段微波辐射计连续观测资料,在实施系统探测实验以进行辐射亮温值(TB(23.87),TB(31.65))与大气汽态总水汽含量(Q)和云中积分液态水含量(L)值反演处理的基础上,分析了黄河上游河曲地区的云水特征,并进行了降水预测及人工增雨作业指标的探讨。结果表明:在黄河上游河曲地区,7—9月纯晴天无云天气条件下,L值基本为0,表明了统计回归反演的显著性。多云条件下Q值和L值分别在3.76~4.75g·cm-2、227.34~859.42g·m-2的范围内。可降水云天气,Q值在5.23~8.65g·cm-2间,L值在421.18~1016.37g·m-2的范围内;积雨云个例分析表明,在降雨开始前近5小时的降雨酝酿期内,Q及L的增加有明显的波动,但在对流云出现并发展时,Q和L总是急剧上升,在降雨前达到一峰值;由河南站和西安站的Q、L值比较差异可以看出,Q、L值受水汽输送、地形等因素的影响,黄河上游河曲地区的人工增雨潜力有显著的优势;所计算出的降水预测阈值,可作为该地区人工增雨作业指标的参考。     

非饱和黄土电阻率和含水率间关系试验研究

通过土壤电阻率和土壤含水率的关系,可以将高密度电法测得的土壤电阻率剖面快速转化为含水率剖面,对于土壤含水率的连续性监测具有重要意义。笔者以甘肃永靖黑方台非饱和黄土为研究对象,采用四电极法进行了室内一维电阻率试验,分析了电阻率的时间特性,提高了黄土电阻率测试的精度,建立了黑方台黄土电阻率与其含水率之间的关系。结果表明,同一干密度条件下,在黄土吸湿和脱湿过程中,黄土的含水率与电阻率呈指数关系,脱湿和吸湿过程均具有较好的相关性,在含水率不断增加的过程中,土体的电阻率逐渐减小。在不同干密度条件下,黄土的电阻率和含水率具有较好的相关性,且随着含水率的增大,电阻率值逐渐减小直至趋于稳定,随着干密度的增大,土体对水分的敏感性有所降低。     

Water mining from the deep critical zone by apple trees growing on loess

There have been significant recent advances in understanding the ecohydrology of deep soil. However, the links between root development and water usage in the deep critical zone remains poorly understood. To clarify the interaction between water use and root development in deep soil, we investigated soil water and root profiles beyond maximum rooting depth in five apple orchards planted on farmland with stand ages of 8, 11, 15, 18, and 22 years in a subhumid region on the Chinese Loess Plateau. Apple trees rooted progressively deeper for water with increasing stand age and reached 23.2 ± 0.8 m for the 22‐year‐old trees. Soil water deficit in deep soil increased with tree age and was 1,530 ± 43 mm for a stand age of 22 years. Measured root deepening rate was far great than the reported pore water velocity, which demonstrated that trees are mining resident old water. The deficits are not replenished during the life‐span of the orchard, showing a one‐way mining of the critical zone water. The one‐way root water mining may have changed the fine root profile from an exponential pattern in the 8‐year‐old orchard to a relative uniform distribution in older orchards. Our findings enhance our understanding of water‐root interaction in deep soil and reveal the unintended consequences of critical zone dewatering during the lifespan of apple trees.     

Numerical modelling of desiccation cracking

The ability to model and predict the formation of desiccation cracks is potentially beneficial in many applications such as clay liner design, earth dam construction, and crop science, etc. However, most studies have focused on statistical analysis of crack patterns and qualitative study of contributing factors to crack development rather than prediction. Because it is exceedingly difficult to capture the nonlinear processes during desiccation in analytical modelling, most such models handle crack formation without considering variation of material properties with time, and are unattractive to use in realistic modelling. The data obtained from laboratory experiments on clay soil desiccating in moulds were used as a basis to develop a more refined model of desiccation cracking. In this study, the properties, such as matric suction, stiffness and tensile strength of soil, and base adhesion, could be expressed approximately as functions of moisture content. The initial conditions and the development of suction due to desiccation and the varying material properties were inputted to UDEC, a distinct element code, using its internal programming language FISH. The model was able to capture some essential physical aspects of crack evolution in soil contained in moulds with varying lengths, heights, and materials of construction. Extension of this methodology is potentially beneficial not only for modelling desiccation cracking in clay, but also in other systems with evolving material properties such as concrete structures and road pavements. Copyright © 2010 John Wiley & Sons, Ltd.     

大连市地理信息共享平台建设内容探讨

以大连市为例,对城市地理信息系统共享平台的建设内容进行探讨,明确了建设目标,将系统的总体建设内容分为数据中心工程、标准规范工程、数据建设工程、运维管理工程、应用接口工程、应用系统工程6个部分,并对各部分进行详细地介绍。