Use of magnetic measures to assess soil redistribution following deforestation in hilly region   总被引：1，自引：0，他引：1  

Parisa Mokhtari Karchegani  Shamsollah Ayoubi  Sheng Gao Lu  Naser Honarju 《Journal of Applied Geophysics》2011,75(2):227-236

Limited information is available about the use of magnetic susceptibility property to determine soil redistribution in hilly areas of the semi-arid regions. This study was conducted to evaluate the use of magnetic properties to determine soil redistribution along a hill slope following deforestation. The study area is located in the Quaternary hilly region of Lordegan district in west Iran. Ten transects were established in two land uses that included natural Querqus forested and cultivated lands. Soil samples were collected at different positions along the slope and magnetic properties (χlf, χhf, SIRM, ARM, and χfd) and selected physico-chemical properties were determined. The results (based on the χfd, SIRM/ARM) showed that the magnetic susceptibly in the calcareous materials is pre-dominantly derived during the pedogenic processes and the superparamagnetic particles which were transported to lower positions of hill slope following deforestation. The results confirmed that this methodology could be applied for monitoring soil redistribution along the slope in calcareous hilly areas in the semi-arid regions.  相似文献   

Slope stability analysis by means of finite element limit analysis and finite element strength reduction techniques. Part II: Back analyses of a case history     

《Computers and Geotechnics》2015

This paper deals with a back analysis of a slope failure. The case history investigated is located in an alpine environment in central Europe and is characterized by a very steep original terrain, indicating in situ soil with high strength. To study the factor of safety, two different approaches applying the so-called φ′/c′ reduction are used, namely finite element limit analysis and strength reduction finite element analysis. Comparison of a strength reduction technique with rigorous finite element limit analysis confirms that the factors of safety (FoS) obtained are very similar for associated plasticity, an intrinsic assumption of limit analysis. For non-associated plasticity, a modified version of the so-called Davis approach has been applied because it has been shown that the original formulation proposed by Davis works well when the FoS is defined in terms of loads but is not appropriate when the FoS is defined in terms of soil strength. The results show that, with the modified Davis parameter, both strength reduction finite element analyses and finite element limit analyses provide very similar factors of safety. The key advantage of limit analysis, however, is that the value of the FoS can be bracketed from above and below with upper and lower bound calculations.  相似文献   

Role of Nitrogen Oxides,Black Carbon,and Meteorological Parameters on the Variation of Surface Ozone Levels at a Tropical Urban Site – Hyderabad,India     

Venkata Swamy Yerramsetti  Nikhil Gauravarapu Navlur  Venkanna Rapolu  N. S. K. Chitanya Dhulipala  Puna Ram Sinha  Shailaja Srinavasan  Gangagni Rao Anupoju 《洁净——土壤、空气、水》2013,41(3):215-225

In this study, temporal variations of surface ozone (O₃) were investigated at tropical urban site of Hyderabad during the year 2009. O₃, oxides of nitrogen (NO_x = NO + NO₂), black carbon (BC), and meteorological parameters were continuously monitored at the established air monitoring station. Results revealed the production of surface O₃ from NO₂ through photochemical oxidation. Averaged datasets illustrated the variations in ground‐level concentrations of these air pollutants along different time scales. Maximum mean concentrations of O₃ (56.75 ppbv) and NO_x (8.9 ppbv) were observed in summer. Diurnal‐seasonal changes in surface O₃ and NO_x concentrations were explicated with complex atmospheric chemistry, boundary layer dynamics, and local meteorology. In addition, nocturnal chemistry of NO_x played a decisive role in the formation of O₃ during day time. Mean BC mass concentration in winter (10.92 µg m^?3) was high during morning hours. Heterogeneous chemistry of BC on O₃ destruction and NO_x formation was elucidated. Apart from these local observations, long‐range transport of trace gases and BC aerosols were evidenced from air mass back trajectories. Further, statistical modeling was performed to predict O₃ using multi‐linear regression method, which resulted in 91% of the overall variance.  相似文献   

油气管道顶管施工中顶力预测模型     

薛振兴  蔡亮学  何利民 《岩土钻凿工程》2012,(4):30-34

顶力计算是顶管施工的重要内容,关系到整个工程的造价和成败。通过对顶力预测进行理论分析,针对混凝土顶管施工建立顶力计算模型,依次计算总顶力的两个组成部分：顶进正面阻力和管周摩擦阻力。采用朗金主动土压力理论计算水平土压力,砂性土采用“水土分算”方法而粘性土采用“水土合算”方法,进而计算顶进正面阻力;结合土柱压力理论和马斯顿压力理论,分别建立相应的管周土压力模型,给出管周总摩擦阻力的计算方法。得到适用条件明确、计算结果可靠的顶力计算公式,该公式的计算结果与工程实例相比较,满足工程要求。  相似文献   

An Atomic Force Microscopy Study on ＂Barkinite" Liptobiolith     

JIAO Kun  YAO Suping  ZHANG Ke  HU Wenxuan 《地质论评》2012,58(4)

利用原子力显微镜观察了树皮煤中两种主要显微组分树皮体和镜质体表面纳米结构特征,揭示了镜质组镜质体大分子团具有网状结构的特征,而类脂组树皮体大分子用具有纤维状、颗粒状和网络状排列结构,随演化程度的提高,树皮体大分子团结构的演化依次表现为纤维状→粒状→不规则网状→网状结构,镜质体则由结构松散的网状结构向高度定向排列的规则网状结构演化.利用AFM的横切面分析工具定量分析了显微组分表面的大分子结构排列,为显微组分分子结构演化和成烃机理研究提供了重要的科学依据.  相似文献   

关于龙游石窟4号洞4-2号岩柱长期抗剪强度反分析问题的讨论   总被引：7，自引：2，他引：5  

杨志法  李丽慧  张路青  高丙丽  曾钱帮  陆民  郑舰 《工程地质学报》2005,13(1):62-67

对于地下工程来说,围岩的长期抗剪强度从来是工程设计者和研究者所关心的课题。但历来仅根据持续时间十分 有限的试验来确定。因此从某种意义上说,由这类试验所得到的,并非真正意义上的长期抗剪强度。所以,本文提出的根据 龙游大型古地下工程即龙游石窟岩柱(包括柱础)的剪坏现象反算岩柱的长期抗剪强度的成果,是很有理论价值的。本文将 以龙游石窟4号洞的4-2号岩柱为对象作古地下工程岩柱长期抗剪强度的反演研究。为了在反演中能进一步考虑剪切面上 各部位的应力变化,作者还借助于FLAC-3D分析结果对不同部分分别进行研究,从而取得了较好的反演结果。  相似文献   

排桩冻结法深基坑施工监测与反馈分析   总被引：5，自引：0，他引：5  

袁宝远  赵燕容  朱旭芬  陈艳国  李爱国 《工程地质学报》2005,13(4):533-537

对于润扬大桥南锚碇排桩冻结法深大基坑,冻结作用使基坑的受力过程变得更为复杂,根据排桩冻结法基坑结构和场地工程地质条件,建立了大型安全监测系统。本文介绍了润扬大桥南锚碇场地工程地质条件、排桩冻结法基坑的结构和南锚碇基坑监测方案、分析了南锚排桩冻结法深基坑各项监测数据的变化规律,包括侧向土压力、内支撑轴力、排桩钢筋应力和排桩水平位移随时间变化规律,并基于施工监测进行了反馈分析,保障了南锚碇排桩冻结法深基坑的安全与稳定。监测结果分析表明,排桩冻结法是基坑工程的一种可行的施工工法,润扬大桥南锚碇排桩冻结法深大基坑的成功实践为今后类似工程的建设积累了宝贵经验。  相似文献   

A Practical Indirect Back Analysis Approach for Geomechanical Parameters Identification     

Hongbo Zhao  Zhongliang Ru  Shunde Yin 《Marine Georesources & Geotechnology》2013,31(3):212-221

Back analysis is a powerful tool to determine geomechanical parameters. In this article, a practical approach that employs the response surface method and MS Excel solver for back analysis is presented. The least square support vector machine (LSSVM)-based response surface is utilized to represent the nonlinear relationship between the geomechanical parameters and the monitored information and Excel solver is used to search the geomechanical parameters based on the monitoring information. We analyze the robustness and search ability of the proposed approach. On the other hand, two numerical cases on a circular tunnel and a slope are used to verify the proposed approach. Results clearly indicate that LSSVM-based response surface is effectively able to be used to identify the geomechanical parameters from the monitoring displacements.  相似文献   

多层球状物角度稀疏投影CT重建仿真研究     

夏惊涛  王群书  李斌康  黑东炜  盛亮  马继明  魏福利  马戈 《CT理论与应用研究》2014,(2):249-256

本文主要针对高密度差多层球状物体的角度稀疏投影CT重建问题,进行基于FBP算法的仿真研究。参考特殊工件材料结构特征设计建立检测对象模型,采用C＋＋语言开发完成平行束圆周扫描FBP重建仿真软件平台。分别采用直接补零和紧邻填充两种方法补全缺失的稀疏投影数据,并进行仿真重建和比较分析。对重建图像进行了有针对性地基于边缘和区域的增强处理方法研究,使缺陷特征得以凸显。本文的研究内容和方法可为具有类似特征的CT无损检测提供技术参考。  相似文献   

The influence of air mass source on the seasonal isotopic composition of precipitation, eastern USA   总被引：5，自引：0，他引：5  

Derek J. Sjostrom  Jeffrey M. Welker 《Journal of Geochemical Exploration》2009,102(3):103

As part of the AIRMoN program, daily precipitation samples have been collected since the early 1990s throughout the eastern and central United States. Using precipitation stable isotope (δ¹⁸O and δD) and HYSPLIT back trajectory analysis of 591 samples collected by the AIRMoN program from Florida, Illinois, Pennsylvania, Tennessee, Vermont, and West Virginia, amount weighted seasonal average isotopic compositions were calculated for precipitation from Continental, Pacific, Gulf of Mexico, Arctic, North Atlantic, and Mid Atlantic sources. Our results suggest that these sources are isotopically distinct and variable at and among most sites during most seasons. However, in many instances, the isotopic differences of the sources require dramatic changes in precipitation amounts from these sources to modify the seasonal average isotopic composition at a particular site. The relative importance of each source type to the seasonal average isotopic composition is highly variable among and within sites. The largest differences in the isotopic compositions of different sources are in winter and spring precipitation from the high latitude sites. At the Vermont location, the seasonal average isotopic composition is potentially quite sensitive to the relative amounts of precipitation from Arctic and Gulf of Mexico sources.  相似文献