An analysis of coastal erosion in the tropical rapid accretion delta of the Red River, Vietnam     

Do Minh Duc  Mai Trong NhuanChu Van Ngoi 《Journal of Asian Earth Sciences》2012,43(1):98-109

The largest plain in the North Vietnam has formed by the redundant sediment of the Red River system. Sediment supply is not equally distributed, causing erosion in some places. The paper analyzes the evolvement and physical mechanism of the erosion. The overlay of five recent topographical maps (1930, 1965, 1985, 1995, and 2001) shows that sediment redundantly deposits at some big river mouths (Ba Lat, Lach, and Day), leading to rapid accretion (up to 100 m/y). Typical mechanism of delta propagation is forming and connecting sand bars in front of the mouths. Erosion coasts are distributed either between the river mouths (Hai Hau) or nearby them (Giao Long, Giao Phong, and Nghia Phuc). The evolvement of erosion is caused by wave-induced longshore southwestward sediment transport. Meanwhile sediment from the river mouths is not directed to deposit nearshore. The development of sand bars can intensively reduce the erosion rate nearby river mouths. Erosion in Hai Hau is accelerated by sea level rise and upstream dams. Sea dike stability is seriously threatened by erosion-induced lowering of beach profiles, sea level rise, typhoon, and storm surge.  相似文献   

三种红层岩石常规三轴压缩下的强度与变形特性研究   总被引：7，自引：2，他引：5  

周应华  周德培  封志军 《工程地质学报》2005,13(4):477-480

利用MTS815Teststar程控伺服岩石力学试验系统研究了川东地区一红层边坡中的砂岩、粉砂岩和泥岩围压为03MPa的应力-应变全过程曲线,建立了峰值强度、峰值强度前弹性模量以及峰值强度后的弹性模量和围压的关系。将低围压下红层的全应力-应变曲线概化成5个阶段,分别为压密段、弹性段、屈服段、应变软化段和塑性流动阶段。试验结果得出,红层弹性模量随围压的增加而提高且变化明显,砂岩和粉砂岩在此围压内为脆性破坏,泥岩为塑性破坏的规律。  相似文献   

楔形体破坏模式下红层边坡岩体质量SMR法评价   总被引：4，自引：2，他引：2  

周应华  周德培  张辉  冯君 《工程地质学报》2005,13(1):89-93

简要介绍了边坡岩体质量分类的SMR法,将之应用于2个典型楔形体破坏模式下红层岩体高边坡稳定性宏观评价。 指出在评价过程中要注意对边坡起控制作用的优势结构面,并将其作为SMR法中结构面项评分的主要依据,这样得出的评分 值与边坡的实际情况才会比较相符。对地应力的影响进行了定性的分析,指出高地应力地区边坡SMR法应该慎用。  相似文献   

红层与煤系复合结构覆岩采动破坏分析及其应用   总被引：3，自引：0，他引：3  

张改玲董青红  隋旺华陈德俊王连奎  赵庆杰 《工程地质学报》2004,12(1):41-44

许多矿区煤层采动影响范围内的覆岩层由红层和煤层共同构成。本文研究了山东省太平煤矿东区二叠系 3号煤层覆岩破坏和防水煤柱留设的问题 ,在对上覆第四系水文地质条件分析的基础上 ,对红层和煤系复合结构覆岩的工程地质特征和破坏状况进行了分析 ,确定了合理的防水煤岩柱高度 ,并经过开采验证 ,避免了水害发生.  相似文献   

Optical properties of the red tide in Isahaya Bay,southwestern Japan: Influence of chlorophyll a concentration     

Hiroaki Sasaki  Akihiko Tanaka  Mitsunori Iwataki  Yasuharu Touke  Eko Siswanto  Chun Knee Tan  Joji Ishizaka 《Journal of Oceanography》2008,64(4):511-523

Remote sensing reflectance [R _rs(λ)] and absorption coefficients of red tides were measured in Isahaya Bay, southwestern Japan, to investigate differences in the optical properties of red tide and non-red tide waters. We defined colored areas of the sea surface, visualized from shipboard, as “red tides”. Peaks of the R _rs(λ) spectra of non-red tide waters were at 565 nm, while those of red tides shifted to longer wavelengths (589 nm). The spectral shape of R _rs(λ) was close to that of the reciprocal of the total absorption coefficient [1/a(λ)], implying that the R _rs(λ) peak is determined by absorption. Absorption coefficients of phytoplankton [a _ph(λ)], non-pigment particles and colored dissolved organic matter increased with increasing chlorophyll a concentration (Chl a), and those coefficients were correlated with Chl a for both red tide and non-red tide waters. Using these relationships between absorption coefficients and Chl a, variation in the spectrum of 1/a(λ) as a function of Chl a was calculated. The peak of 1/a(λ) shifted to longer wavelengths with increasing Chl a. Furthermore, the relative contribution of a _ph(λ) to the total absorption in red tide water was significantly higher than in non-red tide water in the wavelength range 550–600 nm, including the peak. Our results show that the variation of a _ph(λ) with Chl a dominates the behavior of the R _rs(λ) peak, and utilization of R _rs(λ) peaks at 589 and 565 nm may be useful to discriminate between red tide and non-red tide waters by remote sensing.  相似文献   

��Ӷ��Ѵ������ֽ�������ЧӦ   总被引：1，自引：1，他引：0  

孙少安  申重阳  项爱民 《大地测量与地球动力学》2009,29(3):11-15

????????????????????????β??????????????1985??2006??β?????仯??????????1???????????????????????????????????????????????????????????????????????????2????????????????????????????????1?λ??????????￡??????????ε?????????????????????1?γ????????仯?????3?? ????????????????仯?????????????????仯????????????????????????????  相似文献   

Analysis of petroleum hydrocarbons in mangrove sediments of Red Sea of Yemen     

Nabil A. AL-SHWAFI  Abdulhakim AL-KHOLIDI  Aref M. O. AL-JABALI  and Nengjuan ZHOU 《世界地质(英文版)》2009,12(3):160-163

A field work has been carried out to identify the occurrence of oil and oil products pollution in mangrove sediment from Red Sea of Yemen. The concentration of total petroleum hydrocarbons is from 700 ng/g at Kamaran Island station to 400 ng/g at Al-Hodiedah station, and the total organic carbon ( TOC) in samples ranges from 0.07% at Dhubab station to 0.03% at Kamaran Island station. This pollution is as a result of localized oil pollution and /or heavy ship traffic in the Red Sea and Gulf of Aden.  相似文献   

北美地区一次冬季中尺度对流系统上空红色精灵现象的空间观测及其母体雷暴分析     

钟丽华  杨静  陆高鹏  王庸平  何其佳  郄秀书 《大气科学》2020,44(5):997-1012

红色精灵是发生在雷暴云上空的一种大尺度瞬态放电发光现象,它们通常出现在地面上空40～90 km之间,是由地闪回击和随后可能存在的连续电流产生的。目前,由于综合同步观测资料较少,与夏季红色精灵相比,全世界对冬季红色精灵的研究屈指可数。2008年12月27～28日,受高空槽及低层暖湿气流的影响,北美阿肯色州地区爆发了一次冬季雷暴天气过程,搭载于FORMOSAT-2卫星上的ISUAL（Imager of Sprites and Upper Atmospheric Lightning）探测器有幸在这次雷暴上空记录到了两例红色精灵事件。本文利用ISUAL获取的红色精灵观测资料、多普勒天气雷达资料、美国国家闪电定位资料、超低频磁场数据、美国国家环境中心/气候预测中心提供的云顶亮温和探空数据等综合观测数据,对产生红色精灵的这次冬季雷暴特征和相关闪电活动规律进行了详细研究。结果表明,在两例红色精灵中,ISUAL均未观测到伴随的“光晕（halo）”现象,第一例为“圆柱状”红色精灵,第二例红色精灵由于发光较暗,无法判断其具体形态。产生红色精灵的母体雷暴是一次中尺度对流系统,该系统于27日15:00（协调世界时,下同）左右出现在阿肯色州北部附近,并自西向东移动。23:59系统发展到最强,最大雷达反射率因子（55～60 dBZ）的面积达到339 km2,之后开始减弱。03:03雷暴强度有所增加,随后云体便逐渐扩散,雷暴开始减弱,并在11:00完全消散。两例红色精灵发生分别在04:46:05和04:47:14,此时雷暴处于消散阶段,正负地闪频数均处于一个较低水平且正地闪比例显著增加,并且多位于云顶亮温?40°C～?50°C的层状云区上空。红色精灵的出现伴随着30～35 dBZ回波面积的增加。在红色精灵发生期间,雷达反射率大于40 dBZ的面积减少,10～40 dBZ的面积增加,表明红色精灵的产生与雷暴对流的减弱和层状云区的发展有关,这与已有的夏季红色精灵的研究结果类似。红色精灵的母体闪电为正地闪单回击,位于中尺度对流系统雷达反射率为25～35 dBZ的层状云降水区,对应的雷达回波顶高分别为2.5 km和5 km,峰值电流分别为+183 kA和+45 kA。根据超低频磁场数据估算两个母体闪电的脉冲电荷矩变化（iCMC）分别为+394 C km和+117 C km。超低频磁天线记录到了第一例红色精灵内部的电流信号,表明这例红色精灵放电很强。  相似文献   

壳聚糖/蒙脱土插层复合物对活性红染料的吸附热力学研究     

程华丽  李瑾  王涵  焦淑芳  马启敏 《中国海洋大学学报(自然科学版)》2014,44(6):90-96

采用溶液插层法,利用壳聚糖和蒙脱土制备了壳聚糖/蒙脱土插层复合物,使用红外光谱和X-射线衍射分析对其结构进行了表征;以此复合物为活性红染料RR136的吸附剂,考察了复合物中壳聚糖与蒙脱土的摩尔比、染料溶液pH值和浓度、吸附温度及吸附剂用量等因素对吸附性能的影响。结果表明,吸附反应的最佳条件是以壳聚糖与蒙脱土摩尔比为5∶1的插层复合物为吸附剂,反应温度20℃,RR136溶液pH为3。壳聚糖/蒙脱土插层复合物对活性红染料的吸附更符合Langmuir模型,吸附热力学参数ΔGo、ΔHo和ΔSo值分别为-3.338kJ·mol-1(30℃),-37.98kJ·mol-1和-114.77J·mol-1·K-1,表明壳聚糖/蒙脱土插层复合物对活性红染料的吸附是自发的、以物理吸附为主的放热反应。  相似文献   

Cenozoic high-K alkaline magmatism and associated Cu–Mo–Au mineralization in the Jinping–Fan Si Pan region,southeastern Ailao Shan–Red River shear zone,southwestern China–northwestern Vietnam     

《Journal of Asian Earth Sciences》2014

The Jinping–Fan Si Pan (JFP) Cenozoic magmatic and Cu–Mo–Au metallogenic belt in the southeastern part of the Ailao Shan shear zone host the Tongchang, Chang′an, Habo, and Chinh Sang Cu–Mo–Au deposits. These deposits form an integrated epithermal-porphyry regional mineralization system associated with 40–32 Ma high-K alkaline magmatism. The magmatic rocks in the belt have relatively low TiO₂ (<0.73 wt%), P₂O₅ (<0.29 wt%), and FeO^* (<4.99 wt%), and high Na₂O (2.86–4.75 wt%) and K₂O (4.01–7.98 wt%). They also have high contents of incompatible trace elements, and are enriched in LILE (Rb, Ba, K, Sr) and LREE. They have marked Nb, Ta, Ti and P depletion in primitive mantle-normalized spidergrams, and plot close to the EMII mantle field in the Sr–Nd isotopic diagram. These characteristics are similar to those of the Eocene high-K alkaline rocks along the northern Ailao Shan belt, eastern Tibet plateau. The sulfur and lead isotope analyses of sulfide minerals from both the ores and related magmatic rocks confirm the involvement of a magmatic ore fluid. The Cenozoic alkaline intrusions and Cu–Mo–Au mineralization in the JFP were formed prior to the initiation of left-lateral shearing along the Ailao Shan shear zone. The magmas appear to have been derived from enriched mantle, possibly with mixing of materials from the buried Tethyan oceanic lithosphere, and/or crust.  相似文献