太平洋水下海山磷酸盐的成因及形成环境

笔者首次对太平洋与大洋富钴结壳密切相关的海山磷酸盐的成因及形成环境进行了比较深入的研究.研究发现,各种产出形态的磷酸盐都不同程度地交代碳酸盐等含钙物质,而呈现出交代生物结构、交代凝灰结构、交代角砾状结构及交代填间结构等各种交代结构,反映了磷酸盐的交代成因. 此外,其δ13C值(变化于0.7‰~2.0‰之间)也证实其属于交代成因.磷酸盐中Na、Mg、Sr、F、P2O5含量以及Na/P2O5、Mg/P2O5、Sr/P2O5、F/P2O5的比值,特别是晶格中结构CO2的含量(变化于5.7%~6.2%之间),与形成于氧化环境下的Blake plateau、Chatham Rise、Agulhas Bank等处的磷酸盐相近,表明调查区磷酸盐亦形成于氧化环境.氧同位素测定结果表明,磷酸盐的形成温度为5.8~14.8 ℃,平均为11.5 ℃,显示其形成于正常的海水温度环境.西、中太平洋海山磷酸盐形成环境十分接近的事实暗示,西、中太平洋广大区域内的成磷事件存在着时间上和成因上的统一性和相似性.     

泥水平衡盾构用海水泥浆的改性试验研究

由于海水中富集大量可溶性盐类及各种金属离子成分,利用海水配置的海水泥浆具有相对密度大、胶体率低、稳定性差、失水量高等特点,不能满足泥水平衡盾构施工要求。为实现对海水泥浆改性以达到利用海水泥浆维持开挖面稳定,降低穿江越海盾构施工成本,选用CMC(羧甲基纤维素钠)、纤维素PAC(聚阴离子纤维素)、聚丙烯酸铵等8种添加剂进行海水泥浆性质变化试验,优选出对海水泥浆改性明显的添加剂,并分析优选添加剂掺入量和时间对海水泥浆性质的影响规律。同时,基于优选的添加剂CMC,利用泥膜形成试验平台进行改性海水泥浆地层渗透试验。研究表明:不同添加剂对海水泥浆性质变化差异较大,增黏剂PAC、CMC对海水泥浆的改性效果稍好,24 h离析出现浑浊层、混合层、絮凝沉淀层。海水泥浆对地层渗透的滤水量大于改性海水泥浆,泥皮也稍厚,但呈稀疏状态。可以推测,添加剂中和部分海水成分,呈絮凝沉淀,多余添加剂表现出对淡水泥浆的增稠作用。     

Analysis of Safe Span Length and Fatigue Life of Submarine Pipelines

Owing to the complex environmental conditions, suspension could induce complicated forces on submarine pipelines and even cause vortex-induced vibration, resulting in fatigue damage of pipelines. Through aiming at the 28-inch submarine pipeline in the East China Sea, the pipeline was segmented according to the similarity, considering the factors of pipe assembly, typhoon, current, wave and seabed topography. The effects of span length on natural frequency in each section of submarine pipeline were analyzed by finite element model. The maximum safe span length allowed by each pipeline section was verified by fatigue cumulative damage theory, and the fatigue life of each pipeline section were predicted. The results showed that each order natural frequency of the pipeline decreased with the increase of span length. The calculated results of empirical formulas were much smaller than those of the FEM analysis. The increase of the gap between the suspended pipeline and the seabed was beneficial to enhance the fatigue life of the suspended pipeline.     

An Analysis on Limit Load for Corroded Submarine Pipelines

1 .Introduction Submarine pipelines are one of the safest and the least environmentally disruptive means for ma-rine gas or oil transport . With the development of exploitation of submarine oil or gas ,the safety ofsubmarine pipelines has becomethe major …     

水动力作用下管道稳定性的试验研究

利用振荡流水槽在以下两种约束条件下，研究波浪作用下直接铺设于砂质海底的管道失稳临界条件：1）管道两端自由；2）管道可水平、垂直自由运动，但流动受到限制。试验结果表明，管重无量纳数G与管道失稳的临界Fr数之间大致呈线性关系，而当G超过一定数值时，管道是侧向稳定的。管道的约束条件、砂床特性和加载速度对管道稳定性均有影响。     

基于观测的南海西沙海域深层近惯性振荡特征分析

近惯性内波运动普遍存在于全球大洋中,影响大洋中的质量、动量和能量输送,是大气强迫与海洋混合之间的重要纽带。由于目前海洋深层观测资料的缺乏,对于深层近惯性内波生消演变特征研究甚少。利用2009-2012年的潜标观测资料,采用带通滤波和谱分析方法研究了南海西沙海域深层近惯性内波生成、传播和消亡等演变特征。通过研究发现,南海西沙海域深层存在较强的近惯性振荡,其生成源为台风过境能量输入,绝大部分时段内,近惯性振荡能量在海洋浅层耗散,不向海洋深层传播;仅在少部分时段内,近惯性振荡能量的80%～85%耗散在500 m以浅区域,有大概15%～20%继续向海洋深层传播。     

中国晚前寒武纪的宏体化石概观

本文综述了目前中国晚前寒武纪地层中所发现的宏体化石,从18亿年起直到6亿年左右。蓟县剖面高于庄组(14亿年)中发现Grypanta等大化石,再次证明生物演化大阶段的世界性。包括后生动物实体化石在内的淮南生物群可能是前冰期的,也就是先伊迪卡拉期的。震旦纪晚期的西陵峡生物群,现有伊迪卡拉期的典型分子,又有丰富的蠕虫管和高级的红藻、绿藻类。蠕虫管的大量出现预告了带硬部动物时代的到来。     

Spoiler自埋技术特点及其在杭州湾海底管道运行情况分析

海底管道阻流板(Spoiler)自沉埋技术是一种新型管道自埋技术,为深入了解其作用机制及其效果,本文通过分析安装有阻流板的杭州湾海底管道历年检测资料,结合管道附近海域海床、潮流动力特性,深入探讨了阻流板装置在实际工程中的运行效果,分析了其作用机制及其适用条件。研究发现安装阻流板装置的杭州湾海底管道在往复潮流作用下逐渐埋入海床,其埋入段长度由2005年的50%增加到2013年的80%以上,而且平均埋入深度超过2.6 m,自埋效果较好;而在管道路由与海流平行段或管道敷设于抗冲刷强海床上时,阻流板作用不能有效发挥,管道仍然呈现裸露状态。     

A Reliability Based Expert System for Assessment and Mitigation of Landslides Hazard Under Seismic Loading

Different models were developed for evaluating the probabilistic three-dimensional (3-D) stability analysis of earth slopes and embankments under earthquake loading using both the safety factor and the displacement criteria of slope failure.The probabilistic models evaluate the probability of failure under seismic loading considering the different sources of uncertainties involved in the problem. The models also take into consideration the spatial variabilities and correlations of soil properties. The developed models are incorporated in a computer program PTDDSSA.These analysis/design procedures are incorporated within a code named SARETL developed in this study for stability analysis and remediation of earthquake triggered landslides. In addition to the dynamic inertia forces, the system takes into consideration local site effects.The code is capable of assessing the landslide hazard affecting major transportation routes in the event of earthquakes and preparing earthquake induced landslide hazard maps (i.e., maps showing expected displacements and probability of slope/embankments failure) for different earthquake magnitudes and environmental conditions. It can also beused for proposing a mitigation strategy against landslides.     

Dynamic propagation criteria for catastrophic failure in planar landslides

Quantitative assessment of the risk of submarine landslides is an essential part of the design process for offshore oil and gas developments in deep water, beyond the continental shelf. Landslides may be triggered by a reduction in shear strength of subsea sediments over a given zone, caused for example by seismic activity. Simple criteria are then needed to identify critical conditions whereby the zone of weakness could grow catastrophically to cause a landslide. A number of such criteria have been developed over the last decade, based either on ideas drawn from fracture mechanics, or considering the equilibrium of the initial weakened zone and adjacent process zones of gradually softening material. Accounting for the history of the weak zone initiation is critical for derivation of reliable propagation criteria, in particular considering dynamic effects arising from accumulating kinetic energy of the failing material, which will allow the failure to propagate from a smaller initial zone of weakened sediments. Criteria are developed here for planar conditions, taking full account of such dynamic effects, which are shown to be capable of reducing the critical length of the softened zone by 20% or more compared with criteria based on static conditions. A numerical approach is used to solve the governing dynamic equations for the sliding material, the results from which justify assumptions that allow analytical criteria to be developed for the case where the initial softening occurs instantaneously. The effect of more gradual softening is also explored. Copyright © 2016 John Wiley & Sons, Ltd.