Amplitude versus offset analyses of the deep sedimentary structures at the northern flank of the Porcupine Basin,SW of Ireland

This paper represents an attempt of analysing the amplitude versus offset (AVO) behaviour and specific seismic attributes of sedimentary structures from the Porcupine Basin, SW of Ireland. During the last decade, a huge number of carbonate mounds were investigated in this region in water depths of 600–1,000 m, but the genesis and growth of these mounds are still not clearly identified. The aim of this paper is to give a better understanding of the connection between fluid migration pathways in the deeper underground and surface expressions of their fluid expulsions like gas chimneys and pockmarks through which the mounds may generate themselves. The data used in this study to determine boundary conditions for the physical properties of the underlaying strata were gathered from the northern flank of the Porcupine Basin, where a huge amount of fluid and/or gas chimneys covers the seabed. Marine seismic reflection data contain information about the elastic properties of the underlying earth, mainly based on the observed variations in the seismic reflection amplitude at different shot–receiver offsets. To extract elastic parameters from the data, inversion techniques were used, which presume that input amplitudes are proportional to reflection coefficients for plane wave reflection. To calibrate the AVO analyses with the existing stratigraphy in the working area we have used the well logs from several bore holes in the region. The results of this study show clearly that the investigated and identified pockmarks on the seafloor are the surface expression of hydrocarbon seepage in the deeper sedimentary underground.     

裂隙网络非连续介质渗流场与温度场耦合分析研究

在岩体水力学研究中,一个重要问题就是岩体渗流场与温度场的耦合分析。笔者关注了国内外相关的研究,对其发展的趋势进行了展望。系统综述了裂隙岩体渗流-温度耦合的研究情况,阐明了裂隙岩体三种渗流模型的特点、适用范围及裂隙网络非连续介质模型的研究概况,分析了裂隙岩体渗流-温度耦合作用研究及工程应用。最后,提出基于裂隙网络非连续介质渗流温度耦合分析是目前亟待解决的课题,并指出今后需要深入研究的问题。     

Dynamics of the gas flux from shallow gas hydrate deposits: interaction between oily hydrate bubbles and the oceanic environment

Decomposition of methane hydrates on the continental margins is a potentially significant source of atmospheric methane, but the input depends upon the poorly understood fate of the hydrocarbon bubbles rising from the sea floor. During a field trip to the Gulf of Mexico, three different seepages were imaged and analyzed. Three different imaging techniques were tried (side, front, and back illumination), of which back illumination produced the best results. The images were analyzed and the size-dependent bubble distribution, mass flux, and rise speeds determined. The total observed gas flux was 62.3×10⁻³ mol s⁻¹, primarily methane, of which a single vent produced seven times the next largest vent. Of this major vent, 50% of the bubble mass was contained in the largest bubbles, r>5500 μm. The vertical velocities demonstrated that these bubbles were heavily contaminated with oil, which was also corroborated by bubble shape and oscillation observations.     

留家水库坝基渗漏分析

留家水库是一座中型水库，多年来一直存在着渗漏问题，根据水库大坝的勘察资料，对水库渗漏问题进行了分析，并提出截渗措施。     

岩溶水库坝基防渗帷幕灌浆幕深与幕长的结构形式及处理

防渗帷幕灌浆是处理岩溶地区水库坝基坝肩渗漏的主要方法之一，它可以杜绝深、浅层的复杂的岩溶漏水问题，帷幕设计的合理性及其效果取决于水文地质、地下水的补排条件，水工建筑物结构之间的帷幕体的搭接形式，布置格局和边界范围。本文根据34处渗漏水库的灌浆实践，提出确定帷幕的深度和长度的原则，并得出了相关曲线和经验公式，对岩溶地区水库的渗漏处理进行探讨。     

煤矿采空区瓦斯流动分布规律分析

近年来，由于煤矿开采深度的增加、煤与瓦斯突出事故的增多，使人们更加重视对瓦斯运动规律的研究。上隅角瓦斯超限现象在我国煤矿众多高瓦斯矿井中普遍存在，是影响矿井持续、稳定和安全生产的重要原因和事故隐患。为了探讨上隅角瓦斯聚积的根本原因，文章依据渗流理论，在分析采空区内瓦斯流态的前提下，通过建立采空区瓦斯渗流和分布的数学模型，定出边界条件，对采空区瓦斯流动分布规律进行了研究，为分析上隅角瓦斯浓度分布和预测上隅角瓦斯浓度提供了理论依据，对上隅角瓦斯的防治和煤与瓦斯突出预测具有实际意义。     

利用孔中温度场分布确定堤坝渗透流速的热源法模型研究

地下水温度场是研究地下水运动的一种良好的天然示踪剂。库水或河水发生集中的强渗漏时,由于库水、河水与地下水之间的温度差异,渗漏水必将对周围地层温度产生影响。本文对这种由于热源运动而产生的影响进行研究,将渗漏通道看作是一个线热源,利用虚拟热源法推导出了地层中过余温度公式,提出了一个利用孔中温度分布研究堤坝渗漏的简化模型。利用该模型可以计算出堤坝渗透流速,为工程加固提供科学依据。     

三维饱和-非饱和渗流场求解及其逸出面边界条件处理

对三维饱和-非饱和渗流场的有限单元法求解进行了详细论述,在边界条件中明确列出了非饱和渗流逸出面边界条件的数学表达式。为了理论上能够严密地给出非饱和逸出面的边界条件和数值处理,根据渗流场固有的物理特性,定义了极限含水率和非饱和渗流逸出面蒸逸系数两个渗透基本特性参数。针对渗流场饱和与非饱和逸出面分界线(逸出线)位置事先不知道的问题,提出在这种边界非线性渗流场迭代求解过程中,应根据中间解通过边界条件类型的转化来准确地甄别这一分界线,完整地获得精细地处理饱和及非饱和渗流逸出面边界条件的思路与方法。     

基于模糊随机理论的广义可靠度在边坡稳定性分析中的应用

在常规的概率极限状态理论基础上 ,分析了边坡体安全状态的模糊性 ,在此基础上构造了基于MCS以及FORM算法的模糊随机可靠度算法 ,分别就边坡体的滑动失效、渗透破坏两种失效模式作了参数敏感性分析 ,并进一步对边坡体的系统失效模式作了探讨     

深基坑周围地下水渗流破坏影响因素的分析

分析了基底的土层性质、防渗墙的埋入深度以及抽水回灌层位等因素对地下水渗流的影响。根据基坑周围地下水渗流特征,指出了基坑中容易发生渗流破坏的地段,并提出了相应的控制措施。