Impacts of transportation arteries on land use patterns in urban-rural fringe: A comparative gradient analysis of Qixia District, Nanjing City, China     

ZHANG Runsen  PU Lijie  ZHU Ming 《中国地理科学(英文版)》2013,23(3):378-388

Integrated transportation and land use studies are of major interest to planners because they consider the interaction between transportation development and land use change. Quantifying the impact of transport infrastructure on land use change is necessary for evaluating the role of transportation development in the process of land use and land cover change in the urban-rural fringe. Taking Qixia District of Nanjing City, Jiangsu Province, China as a typical urban-rural fringe area, this paper analyzes the patterns and characteristics of land use change along three major transportation arteries using land use data from 2000 and 2008. We examine the spatial differentiation and gradient of land use pattern around railway, expressway, and highway corridors to investigate whether land use change in the urban-rural fringe is related to distance from transportation arteries and to clarify the varying impacts of different forms of transport infrastructure on land use patterns. We find that construction land generally tends to be located close to major transportation arteries, and that railways have the most obvious influence on land use change in the urban-rural fringe, while the impact of expressways was not significant. We conclude that there exists a causal relationship between the presence of transportation arteries and land use change in the urban-rural fringe, but this relationship varies across different types of linear transport infrastructure.  相似文献   

中国北方东部地区春季降尘量及其环境意义   总被引：13，自引：7，他引：6  

李晋昌  董治宝  王训明 《中国沙漠》2008,28(2):195-201

 中国北方东部地区2001—2002年春季降尘量分布特征的研究表明,研究区平均春季降尘量为127.05 t·km^-2,约占全年的一半,且主要集中在3、4月;春季降尘以近源沉积为主,因此降尘量的空间分布主要受局部环境的影响;除中沙外,降尘总量和降尘中其他组分的沉积量随距离均呈现指数递减趋势,且粒度越大的颗粒物,其半衰距离越短;更新世时期黄土高原平均每年流失的黄土至少已达1亿t,现在黄土高原每年实际流失的黄土大约为14.4亿t,如以此侵蚀速度持续下去,黄土高原将在6.6~13.2万a之内被侵蚀完毕。  相似文献   

增强型管桩和普通管桩受力性能试验对比研究   总被引：1，自引：1，他引：0       下载免费PDF全文

付贵海  魏丽敏  郭志广 《水文地质工程地质》2012,39(3):60-64

通过对桩身预埋有混凝土应变计的普通光圆预应力管桩和增强型预应力管桩的静载对比试验,比较了两种桩的荷载-沉降曲线、桩身轴力分布情况、桩侧摩阻力及桩端阻力的发挥性状,研究了增强型管桩荷载传递规律及桩身环向凸肋的荷载分担情况.结果表明,由于环向凸肋的存在,使增强型管桩在桩周形成的剪切破坏面比普通管桩更大,从而提高了增强型管桩的承载能力.在最大试验荷载作用时,增强型管桩的侧摩阻力要比普通管桩高27.4％～39.5％.  相似文献   

连续流气提式流化床启动过程中好氧颗粒污泥的形成机制   总被引：4，自引：0，他引：4  

周丹丹  刘孟媛  侯典训  王紫嫣  梁爽  董双石 《吉林大学学报(地球科学版)》2012,42(1):212-219

探讨连续流气提式好氧颗粒污泥流化床(CAFB)反应器的运行特征,对该工艺颗粒污泥形成过程、形成机理和颗粒性质进行分析。以市政污泥为接种污泥,以醋酸钠为碳源,在连续运行方式下培养好氧颗粒污泥。研究结果表明：CAFB反应器启动的第4－5天即有大量颗粒污泥形成,颗粒直径800~1 000 μm,比重1.006,生物相丰富,能够分泌大量胞外聚合物。当COD有机负荷高达8 和13 kg/(m³·d)时,对COD处理效率均维持在93%~97%,COD出水质量浓度仅为30~80 mg/L,引起启动后期丝状菌的大量繁殖,污泥流失。进一步提高污泥负荷有望控制污泥膨胀。  相似文献   

坑道口部管棚加固抗爆性能模型试验研究     

许宏发  佟佺  王广建  王德荣 《岩土力学》2012,33(11):3219-3224

正确评估管棚加固围岩的抗爆性能,对坑道口部防护设计十分重要。基于相似模拟理论,用不同配比的水泥土替代自然岩体和注浆岩体,用塑料管替代钢管,模拟管棚超前支护坑道口部在爆炸荷载作用下的抗爆性能。制作了口部相似模型3件,模型长×宽×高为2 m×2.2 m×2 m,在顶部直接爆炸,分别模拟无管棚、1层管棚和3层管棚下,坑道口部动力响应和破坏特征。试验表明：管棚超前支护能有效加固坑道围岩,整体性增强,受力分布合理;随着管棚层数增加,口部破坏明显减弱,拱顶破坏范围从1.55 m减小到0.45 m、主裂缝最大宽度由25 mm减小到3 mm、网状裂缝最大宽度由24 mm减小到0.3 mm、裂缝条数由14条减少到3条、模型顶部爆坑体积由0.12 m3减小到0.05 m3。管棚超前支护能有效地将爆炸荷载的破坏作用控制在管棚加固层之外,抗打击能力明显增强。  相似文献   

考虑软土结构性损伤的柱形孔扩张理论分析     

雷华阳  丁小冬  张万春 《岩土力学》2012,33(10):3059-3066

采用考虑结构性损伤的四折线应变软化模型,针对管桩沉桩过程中产生的挤土效应,得出改进的柱形孔扩张理论解,并与已有模型进行对比分析,结果表明,简化的四折线模型与软土的典型压缩曲线最为接近,提出了四折线模型中各直线段和相应参数的确定方法。采用Mohr-Coulomb屈服准则和相关联流动法则,提出了桩周不同区域内土体的应力、应变计算公式,给出了极限软化半径、极限破坏半径和极限扩张压力的计算方法。结合工程实例,通过对比分析发现,四折线模型的位移计算值与实测值最为接近,能更好地符合管桩挤土效应的实际情况。  相似文献   

管桩挤土效应的现场试验和数值模拟   总被引：4，自引：0，他引：4  

雷华阳  李肖  陆培毅  霍海峰 《岩土力学》2012,33(4):1006-1012

以PHC管桩加固某物流加工二期标准仓库、厂房项目为依托,进行了吹填土地区PHC管桩的挤土效应研究。利用预先埋设的孔压计和测斜计,借助沉桩过程的现场测试手段,研究了PHC管桩在沉桩过程中桩周孔压变化和土体位移分布特征,发现沉桩过程中超孔隙水压力随距桩心距离的增加而近似呈线性规律衰减,影响范围约为10倍桩径,土体水平位移不仅与地基土性质有关,而且其分布特征也与深度有很大关系,表现为0.2～0.4倍桩长处土体水平位移较大。采用数值模拟有效地模拟了现场测试结果,进而将结果推广,得到了沉桩引起的桩周土体位移随深度和距桩心距离的变化规律。数值模拟结果表明：桩-土界面摩擦特性和桩径对土体位移场的影响较大。  相似文献   

柔性管Reel-lay铺管安装稳定性分析   总被引：2，自引：1，他引：1  

白勇  唐继蔚  余彬彬  阮伟东  闫会宾 《海洋工程》2013,31(6):22-29

钢管的S-lay、J-lay铺管方法的应用研究已经非常深入,而柔性管的Reel-lay铺管法的应用研究则相对较少。由于管道本身的材料非线性、管土接触存在非线性以及环境的不确定性等问题过于复杂,因此通过类比J-lay铺管法,采用整管的力学性能、弹性海底模型及均匀流等方式对Reel-lay铺管的水下段稳定性问题进行了简化;根据悬链线理论和小变形梁理论,给出了柔性管Reel-lay铺管法的数值计算方法,并与有限元模拟的结果进行了对比分析。结果表明:随着铺设角度增大,管道受到的弯矩也随之增大,但管道顶部的拉力却随之减小;随着铺设水深的增加,管道悬浮段质量增加,管道顶部拉力明显增加,但弯矩明显减小;浮重对管道铺设很重要,应根据实际情况,选择合适的配重以满足管道稳定和铺设的要求。  相似文献   

Erratum     

Guest Editor Rahul Sharma 《Marine Georesources & Geotechnology》2013,31(1):61-62

Abstract

Several physical aspects of continuous subbottom profiling are presented, and their relationship to operating characteristics of profiling instruments is discussed. Interpretation of data produced by shallow‐penetration continuous profilers, such as the SONIA system, is a process of transformation of the continuous measurement of the travel times of reflected sound pulses into geologic phenomena. Essentially, the continuous profiler is a geologic tool; interpretation of the data is based on geologic observation and reasoning, irrespective of the further use of the information obtained in applied science. However, interpreters must have sufficient knowledge of the geophysical system and of the equipment design to be in a position to evaluate the significance of their interpretation.  相似文献   

The Stability of Tide Gauges in the South Pacific Determined from Multiepoch Geodetic Levelling, 1992 to 2010     

Manoj Nilesh Deo  Ramesh Govind  Ahmed El-Mowafy 《Marine Geodesy》2013,36(3):261-284

Tide gauge data is important for determining global or local sea level rise with respect to a global geocentric reference frame. Data from repeated precise levelling connections between the tide gauges and a series of coastal and inland benchmarks, including Continuous GPS (CGPS) benchmarks, are used to determine the stability of tide gauges at 12 locations in the South Pacific. The method for determining this stability is based on a constant velocity model which minimises the net movement amongst a set of datum benchmarks surveyed since the installation of the tide gauges. When assessed at a 95% confidence interval, and with the exception of the Solomon Islands, none of the tide gauges were found to be in motion relative to their CGPS benchmarks. The Solomon Islands estimate is considered to be unreliable since the CGPS benchmark was recently established and has been surveyed fewer than three times. In Tonga and Cook Islands, the tide gauges were found to be disturbed or affected by survey errors whereas the Vanuatu results were affected by earthquakes.  相似文献