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141.
142.
The authors have previously determined that the effectiveness and failure pattern of the ice cover caused by flexural-gravity waves generated by a submerged body motion near the bottom ice can greatly depend on the depth of the water area. In its turn, the presence of a ledge on the ice surface may affect a wave propagation pattern. This paper presents an experimental study of the bottom contour influence on the deflection and length of flexural-gravity waves. The authors describe a numerical model for the analysis of the deformed state of ice caused by hydrodynamic loads due to a submarine motion, taking into account the bottom contour. The experiments are carried out in the ice tank. The results of calculations and experiments are compared. 相似文献
143.
Offshore pipelines are critical infrastructures and any possible damage may have devastating financial and environmental consequences. Earthquake-related geohazards (such as strong ground motion, active seismic faults, submarine landslides and debris flows) consist crucial threats that an offshore pipeline has to overcome. The main aim of the current study is to examine analytically a seabed-laid offshore pipeline subjected to a lateral kinematic distress due to a submarine landslide or a debris flow. Extra emphasis is given on the impact of pipe-soil interaction on the pipe response, by the realistic representation of the soil resistance via a tri-linear model. Firstly, the proposed analytical model is validated with a numerical model utilizing the finite-element method. Subsequently, various combinations of soil parameters and loading conditions that affect the examined problem are investigated with realistic input data taken from the offshore section of the high-pressure natural-gas pipeline TAP (Trans Adriatic Pipeline) in the Adriatic Sea. Finally, useful conclusions are drawn regarding the applicability and the efficiency of the proposed approach. 相似文献
144.
多元统计分析在金川铜镍矿床两类矿石中的应用 总被引:3,自引:0,他引:3
应用聚类分析和因子分析对金川铜镍硫化物矿床样品及其微量元素进行了分析和科学分类,并对分类的样品进行R型因子分析,找寻在成矿作用过程中对成矿贡献起关键性作用的因子。因子分析结果表明,富矿类型的网状矿石与贫矿类型的星点状矿石的Ni,Cu矿化期存在着明显的差异性;网状矿石在成矿作用过程中,经受了晚期晚阶段的中、低温热液作用,使矿石中的主要成矿元素Cu产生了进一步的叠加和富集,并伴有Bi,Se,Te及贵金属元素的富集。因子分析的研究为脉动式多期多阶段的成矿机制模式提供了新的依据,同时,也为矿床中有用伴生元素的赋存状态及找寻提供了有用的成因信息。 相似文献
145.
146.
大型海底热液硫化物矿体的形成机制是涉及多种控制因素的复杂地质过程,其中热液流体同海水的混合扮演着重要角色。大洋钻探计划(ODP)资料表明在大西洋TAG区热液硫化物矿体内部,热液流体同经过改造的海水之间发生着广泛的混合作用,这个过程在很大程度上控制着海底热液硫化物矿体的内部结构和化学组成。以TAG热液硫化物矿体为例,利用数值模拟方法模拟了热液流体与经过不同程度改造的海水的混合过程,试图探讨海水与热液流体混合在热液硫化物矿体形成中的作用。模拟计算结果表明:(1)来自矿体深部的热液流体与经围岩加热的下渗海水的混合是造成TAG热液活动区硬石膏大量沉淀的重要原因;(2)在热液流体与海水的混合过程中,混合流体的化学性质和矿物沉淀情况在330~310℃上下发生了较大变化,330~310℃是一个特殊的温度区域;(3)利用数值计算结果探讨了TAG热液活动区不同区块(TAG-1,TAG-2和TAG-5等)的流体混合作用和热液活动过程。 相似文献
147.
Radium tracing of submarine groundwater discharge (SGD) and associated nutrient fluxes in a highly-permeable bed coastal zone, Korea 总被引:2,自引:0,他引:2
In order to estimate submarine groundwater discharge (SGD) and SGD-driven nutrient fluxes, we measured the concentrations of nutrients, 224Ra, and 226Ra in seawater, river water, and coastal groundwater of Yeongil Bay (in the southeastern coast of Korea) in August 2004 and February 2005. The bottom sediments over the shallow areas of this bay are composed mainly of coarse sands. Large excess concentrations of 224Ra, 226Ra, and Si supplied from SGD were observed in August 2004, while these excess concentrations were not apparent in February 2005. Based on the mass balance for 224Ra, 226Ra, and Si, which showed conservative mixing behavior in seawater, SGD was estimated to be approximately 6 × 106 m3 day− 1 (seepage rate = 0.2 m day− 1) in shallow areas (< 9 m water depth) in August 2004, which is much higher than the SGD level typically found in other coastal regions worldwide. During the summer period, SGD-driven nutrients in this bay contributed approximately 98%, 12%, and 76% of the total inputs for dissolved inorganic nitrogen (DIN), phosphorus (DIP), and silicate (DSi), respectively. Our study implies that the ecosystem in this highly permeable bed coastal zone is influenced strongly by SGD during summer, while such influences are negligible in winter. 相似文献
148.
Submarine groundwater discharge (SGD) to coastal southern Rhode Island was estimated from measurements of the naturally-occurring radioisotopes 226Ra (t1/2 = 1600 y) and 228Ra (t1/2 = 5.75 y). Surface water and porewater samples were collected quarterly in Winnapaug, Quonochontaug, Ninigret, Green Hill, and Pt. Judith–Potter Ponds, as well as nearly monthly in the surface water of Rhode Island Sound, from January 2002 to August 2003; additional porewater samples were collected in August 2005. Surface water activities ranged from 12–83 dpm 100 L− 1 (60 dpm = 1 Bq) and 21–256 dpm 100 L− 1 for 226Ra and 228Ra, respectively. Porewater 226Ra activities ranged from 16–736 dpm 100 L− 1 (2002–2003) and 95–815 dpm 100 L− 1 (2005), while porewater 228Ra activities ranged from 23–1265 dpm 100 L− 1. Combining these data with a simple box model provided average 226Ra-based submarine groundwater fluxes ranging from 11–159 L m− 2 d− 1 and average 228Ra-derived fluxes of 15–259 L m− 2 d− 1. Seasonal changes in Ra-derived SGD were apparent in all ponds as well as between ponds, with SGD values of 30–472 L m− 2 d− 1 (Winnapaug Pond), 6–20 L m− 2 d− 1 (Quonochontaug Pond), 36–273 L m− 2 d− 1 (Ninigret Pond), 29–76 L m− 2 d− 1 (Green Hill Pond), and 19–83 L m− 2 d− 1 (Pt. Judith–Potter Pond). These Ra-derived fluxes are up to two orders of magnitude higher than results predicted by a numerical model of groundwater flow, estimates of aquifer recharge for the study period, and values published in previous Ra-based SGD studies in Rhode Island. This disparity may result from differences in the type of flow (recirculated seawater versus fresh groundwater) determined using each technique, as well as variability in porewater Ra activity. 相似文献
149.
The short-lived radium isotopes, 223Ra (T1/2 = 11.4 days) and 224Ra (T1/2 = 3.66 days), have been successfully used as tracers of several environmental processes, e.g., submarine groundwater discharge, coastal mixing processes, and water residence times. In this paper, the uncertainties associated with 223Ra and 224Ra measurements using a Radium Delayed Coincidence Counter are determined on a detailed error propagation basis with a confidence interval of 1σ. From the data analyses of several groups of coastal water samples, the calculated relative uncertainties averaged 12% for the 223Ra and 7% for the 224Ra. These uncertainties can decrease for radium-enriched groundwater samples although asymptotic limits have been found at 7% relative uncertainty for 223Ra and 4% for 224Ra. In this paper, the influence of sampling and measurement parameters on the final radium uncertainties is evaluated in order to provide guidance to optimize these factors and obtain more reliable results. 相似文献
150.
Takashi Doi Michiaki Takano Kei Okamura Tamaki Ura Toshitaka Gamo 《Journal of Oceanography》2008,64(3):471-477
We present the results of a chemical survey at a submarine volcano, Teishi Knoll, obtained using a submersible in-situ Mn
analyzer (GAMOS) mounted on an autonomous underwater vehicle (AUV) platform. During this survey, high-resolution data of dissolved
Mn were obtained in three dimensions in nearly real time. The AUV enabled continuous detailed observations along a preprogrammed
pathway, which could not have been performed with conventional CTD hydrocasts. During this observation, anomalously high dissolved
Mn concentrations were obtained within the crater, corresponding to high water temperatures. The anomalies might be a hydrothermal
signature due to volcanic activity from the crater. 相似文献