Reliability analysis of soil nail internal limit states using default FHWA load and resistance models     

Jie Yuan 《Marine Georesources & Geotechnology》2013,31(7):783-800

Abstract

Reliability analyses of nail pullout, nail-in-tension, and system reliability of internal limit states are presented for both permanent and temporary soil nails that are designed using default Federal Highway Administration nail load and resistance models within traditional deterministic allowable stress design (ASD) framework. The model uncertainty, correlations between soil strength parameters, between model factor, and nominal load term, and between the two internal limit states, and influence of model factor fittings are all addressed in the analyses. This study provides a general idea of the reliability that is implicitly embedded in current ASD-based soil nail internal limit state designs.  相似文献   

海水中溶解态铵盐氮同位素分析的预处理方法     

刘丽丽  于海燕  俞志明  宋秀贤  曹西华  袁涌铨 《海洋科学》2013,37(12):28-33

以蒸馏法为基础, 研究了适合海水中铵盐稳定氮同位素分析的预处理方法。对蒸馏法预处理过程中的最佳蒸馏时间、沸石的选取、铵盐最适浓度范围等分别进行改进和优化, 获得稳定、高效的海水中铵盐氮稳定同位素分析预处理方法。结果表明: 最佳蒸馏时间为50 min, 铵盐的回收率为(97±5.8)%。测定了不同沸石对不同浓度氨氮的吸附率, 筛选出酸性条件下铵氮吸附效率较高且稳定的康华科技沸石; 确定铵盐的最佳适用浓度范围为2～10 μmol/L, 在该浓度范围内氮回收率94%～99%,氮分馏系数为0.1‰～0.8‰。将此方法应用于长江口海域水样分析, 结果表明, 这一方法可以应用于河口中铵盐的氮同位素分析, 能够为河口中溶解态氮的来源及循环机理等研究提供有效信息。  相似文献   

东南极普里兹湾NP93－2柱样古地磁结果          下载免费PDF全文

王保贵  侯红明  汤贤赞  袁友仁 《极地研究》1996,8(1):34-40

（王保贵）（候红明）（汤贤赞）（袁友仁）ＰａｌｅｏｍａｇｎｅｔｉｃｒｅｓｕｌｔｓｏｆＣｏｒｅＮＰ９３－２ｆｒｏｍｔｈｅＰｒｙｄｚＢａｙ，ＥａｓｔｅｒｎＡｎｔａｒｃｔｉｃａ￥ＷａｎｇＢａｏｇｕｉ；ＨｏｕＨｏｎｇｍｉｎｇ；ＴａｎｇＸｉａｎｚａｎａｎｄＹｕ...  相似文献   

种子预处理对唐古特白刺出苗和幼苗生长的影响     

屠彩芸  郭凤霞  李新荣  陈垣  何明珠 《中国沙漠》2011,30(4):981-986

 采用不同方法对唐古特白刺种子预处理,以不处理为对照,再行60 ℃浸种24 h后育苗,通过测定出苗动态和生长指标,探寻促进白刺种子出苗和幼苗生长的技术途径。结果表明,唐古特白刺种子出苗率变化动态均呈“S”型曲线,符合Logistic曲线方程,出苗质量随种子处理不同而异,出苗期为38～55 d,极限出苗率为30.2%～57.8%。沙搓和沙碾均可显著提高白刺种子出苗质量,为培育壮苗奠定良好基础,出苗率较对照分别提高15.6%和13.4%,出苗势分别提高60.1%和6.9%,出苗指数分别提高35.2%和13.2%,活力指数分别提高41.5%和23.3%。尤其沙搓种子出苗集中,较对照缩短5 d。而掐尖、20%醋酸和5%碱水浸泡均抑制发芽。将种子与沙子混合后手搓和棍碾压均可破坏白刺种子坚硬致密的内果皮结构,破除休眠,促进出苗和幼苗生长,但需注意的是沙碾操作不当会造成种子内部结构被破坏。  相似文献   

GIS在矿产资源潜力评价中的应用     

孙元 《地理空间信息》2012,(3):57-60

GIS技术的广泛应用为矿产资源潜力评价提供了新的思路和手段,并对其产生了深远的影响。简要介绍了GIS、矿产资源潜力评价及GIS在矿产资源潜力评价中的应用现状,并根据基于GIS矿产资源潜力评价的3个步骤,详细阐述了GIS在矿产资源潜力评价中的具体应用及其优越性。  相似文献   

Similarity quantification of soil parametric data and sites using confidence ellipses     

Liang Han  Lin Wang  Xuanming Ding  Haijia Wen  Xingzhong Yuan  Wengang Zhang 《地学前缘(英文版)》2022,(1):217-229

This paper presents a confidence ellipse-based method to evaluate the similarity of soil parametric data using the database from the site investigation reports.Then,the obtained similarity assessment results of parametric data are used to further estimate the site similarity via two proposed strategies,namely the mean and weighted mean approaches.The former referred to the average of parametric data similarity degrees,while the latter was the weighted average,and the weight was calculated using the coefficient of variation(COV)of each parameter.For illustration,the liquidity index(LI)dataset was firstly used to explore the performance of the presented method in the evaluation of parametric data similarity.Subsequently,the site similarity was assessed and the effects of numbers and weights of selected parameters for study were systematically studied.Lastly,the transformation models about the relationships between Cc and x as well as between Cc and e0 were constructed to illustrate the application of the similarity analysis in reduction of transformation uncertainty.Results show that the greatest site similarity degree is at about 0.76 in this study,and the maximum decrease of transformation uncertainty can reach up to 18%and 25.5%as union parametric data similarity degree increases.Moreover,the site similarity degree represents the whole similarity between two different sites,and the presented union parameter similarity degree maintains a good agreement with transformation uncertainty.  相似文献   

吉林延边地区土壤钙元素生态地球化学   总被引：3，自引：0，他引：3  

王冬艳  李月芬  尚媛  白荣杰  徐倩 《吉林大学学报(地球科学版)》2011,41(1):215-221

在吉林延边地区系统的野外调查和土壤及苹果梨果实样品采集、测试的基础上,采用统计对比及相关分析方法研究了土壤钙元素全量、交换性钙及果实钙含量的空间差异,以及土壤-果实系统中钙元素的转化吸收特征及其对果实品质的影响,目的在于揭示钙元素的迁移转化规律及其生态效应,为土地利用服务。结果表明：延边地区土壤中钙全量总体上缺乏,不同研究区土壤-果实钙元素转化吸收差别明显;果实中钙元素含量趋于一致,其吸收系数在可变范围内与土壤交换性钙含量呈极显著负相关;土壤交换性钙含量与pH值呈极显著正相关,与果品品质的4项指标(总糖、总酸、可溶性固形物和维生素C）具有显著相关性,其含量丰富有利于果品品质的提高。  相似文献   

Environmental effects of foreign trade and its spatial variations in mid-eastern provinces and cities of China     

Xianfeng Jin  Suocheng Dong  Lingjun Luo  Yu Li  Chao Yuan  Kesheng Shu  Jiaquan Chen 《中国地理科学(英文版)》2012,22(5):626-636

The studies on environmental effects of foreign trade and its spatial variations are helpful to design and implement environmental protection countermeasures.In order to eliminate the adverse effects of insufficient observation values on the accuracy of regression results and dynamic information quantity of fitting equation during empirical study,panel data of the mid-eastern provinces and cities of China from 1985 to 2007 were selected based on the adjustment of classical regression model in this paper.Panel unit root test and panel cointegration analysis method were applied to investigating the environmental effects of foreign trade and its spatial variations in the mid-eastern provinces and cities of China and its three groups divided by foreign trade dependence.The results show that all scale effects are positive,while all technical effects are negative and unable to counteract positive scale effects.Foreign trade development is regarded as an important cause for outstanding eco-environmental problems in the mid-eastern provinces and cities of China.Total effects and structural effects are significantly different among different groups because of spatial variations in environmental policies,export destinations,source of FDI,etc.Following the principle of′coordinating generality and considering differences comprehensively′,it is essential to issue a series of policies and countermeasures corresponding to differences in regional environmental effect of foreign trade,in order to coordinate the relationship between foreign trade development and eco-environment in each region.  相似文献   

黑潮及相邻海域表层砂壳纤毛虫分布模式:以夏季黄海、东海至西太平洋断面为例   总被引：1，自引：0，他引：1  

宣俊  李海波  王超锋  董逸  赵苑  赵丽  张武昌 《海洋科学》2022,46(2):28-36

2019年夏季对沿黄、东海至西太平洋跨越黑潮一个断面(122°E～145°E)的表层砂壳纤毛虫群落进行调查,研究了黑潮中砂壳纤毛虫与相邻水体的差异.根据水文环境及各站位所处的空间位置,我们将研究区域划分为大洋边缘区域、黑潮区域和大洋区域.各站位砂壳纤毛虫的丰度范围为3.95～31.94 ind·L–1,种丰富度范围为6...  相似文献   

郯庐断裂中段新生代右行走滑位移   总被引：2，自引：0，他引：2  

黄超  余朝华  张桂林  傅良同  袁志云  范兴燕 《吉林大学学报(地球科学版)》2013,43(3):820-832

依据走滑拉分盆地中盆地沉降（或抬升）速率与边界断层走滑速率之间的数值关系,通过对夹在郯庐断裂中段两分支断层间的潍北凹陷沉积埋藏史的恢复,间接求取郯庐断裂中段新生代右行走滑位移。潍北凹陷内不同构造位置4口井的埋藏史恢复结果表明：凹陷新生代经历了古近纪早、中期的快速沉降,古近纪末-新近纪初的抬升剥蚀和中新世以来的缓慢沉降3个阶段;各阶段的平均沉降速率分别为0.142 9、-0.072 8、0.032 5 km/Ma。通过对太平洋板块与欧亚板块间俯冲速率和方向变化的分析推断,中新世中期（39.5 Ma）太平洋板块由北西向俯冲转而变成正西向俯冲所产生的西南向应力分量是导致新生代郯庐断裂开始右行走滑的主要因素,且走滑活动持续至今。根据走滑活动发生和持续的时间,结合各个时期内潍北凹陷的沉降和抬升速率,计算出郯庐断裂中段新生代右行走滑位移量为15 km左右。  相似文献