A traversing system to measure bottom boundary layer hydraulic properties

This study describes a new convenient and robust system developed to measure benthic boundary layer properties, with emphasis placed on the determination of bed shear stress and roughness height distribution within estuarine systems by using velocity measurements. This system consisted of a remotely operated motorised traverser that allowed a single ADV to collect data between 0 and 1 m above the bed. As a case study, we applied the proposed traversing system to investigate bottom boundary layer (BBL) hydraulic properties within Coombabah Creek, Queensland, Australia. Four commonly-employed techniques: (1) Log-Profile (LP); (2) Reynolds stress (RS); (3) Turbulent Kinetic Energy (TKE); and (4) Inertial Dissipation (ID) used to estimate bed shear stresses from velocity measurements were compared. Bed shear stresses estimated with these four methods agreed reasonably well; of these, the LP method was found to be most useful and reliable. Additionally, the LP method permits the calculation of roughness height, which the other three methods do not. An average value of bed shear stress of 0.46 N/m², roughness height of 4.3 mm, and drag coefficient of 0.0054 were observed within Coombabah Creek. Results are consistent with that reported for several other silty bed estuaries.     

地层温度对科学超深井井壁稳定的影响

井壁稳定问题包括井壁坍塌和地层破裂2种基本类型,科学超深井钻探的目的层是处于高地应力、高地温和高地层压力的深部岩层,井壁稳定问题更加突出。以12000 m科学超深井为例,从地层温度入手,分析钻井液循环温度变化所引起的当量静态钻井液密度和环空压力当量密度的变化,以及温梯应力、温差应力对井壁稳定的影响。     

煤样渗透率有效应力与基质收缩双重耦合效应及其与煤阶关系

为研究煤层气在排采过程中不同煤阶煤储层渗透率动态变化规律,利用煤岩三轴应力应变（基质收缩膨胀）测试系统,对褐煤、气煤和无烟煤样开展了有效应力与基质收缩双重效应物理模拟实验。固定轴压和围压不变,改变气体平衡压力,模拟开发过程中储层压力变化特征,测试其动态渗透率。利用实验结果,分析了不同煤阶煤岩在排采过程中动态渗透率反弹特征,并对比分析煤岩动态渗透率改善效果的差异性。研究表明：气体平衡压力从5 MPa降至1 MPa过程中,在有效应力和基质收缩双重效应作用下,褐煤样的归一化渗透率依次为1. 00、0. 60、0. 57、0. 57、0. 52,气煤样依次为1.00、0. 64、0. 50、0. 54和0. 55,无烟煤样依次为1.00、0. 74、0. 58、0. 50和0. 56。随气体平衡压力下降,中阶及高阶煤样动态渗透率先下降后上升,整体呈不对称“V”型变化规律,但拐点略有不同;低阶煤样动态渗透率呈先下降后基本稳定的趋势,整体呈斜“L”型变化规律。在有效应力和基质收缩双重效应影响下,中阶及高阶煤样动态渗透率改善效果优于低阶煤样。     

Triaxial stress state deep in orogenic belts: an example from Turkey

A rare metachert pebble containing amphibole grains with microboudin structures in a wide range of orientations provides an opportunity to perform stress analysis in two orthogonal orientations on the foliation surface. The sample was analysed by the microboudin method to infer the triaxial stress state during microboudinage. Stress parameters proportional to the far-field differential stress were determined for sodic amphibole grains in the two orientations. The ratio of the stresses in the two orthogonal orientations (σ₁−σ₂)/(σ₁−σ₃) was calculated to be 0.64, indicating that σ₂ lies closer to the midpoint between σ₁ and σ₃ than to σ₃.     

An effective approach to determine the dynamic source parameters

In this study, we present a new and effective method to determine the dynamic source parameters (i.e., stress drop and strength distribution). We first assume that the kinematic source parameters, i.e., the slip and rupture time distributions on the fault plane, are known from the previous source inversion studies. Then, using the seismic source representation theorem we determine the dynamic stress field on a fault plane from known kinematic parameters. Finally, we determine the strength of the fault defined as the peak stress just before the rupture. We have tested the validity of this method by using an illustrative two-dimensional analytical example. To assess the applicability of this method, we have applied it to study the 1979 Imperial Valley earthquake, and obtained consistent results with those ofMiyatake's (1992) andQuin's (1990). Compared with previous methods, this new method is simple, straightforward and accurate, and needs much less calculation. Therefore, it is expected to be useful in exploring the seismic source process.     

安徽淮河构造变形带及邻近块体现代构造应力场特征

针对安徽省较特殊的构造环境及历史地震分布特点，利用直达波最大振幅比和系统聚类分析方法，在对安徽淮河中游区1974年以来近百个中小地震震源机制反演、聚类及空间合成的基础上，分析了华北断块南缘的安徽淮河构造变形带及邻近块体震源断层滑动方式、构造应力场分布及块体运动方式、应力场随时间变化等。结果显示：淮河构造变形带及其邻近块体上震源断层总体上以近走滑型或斜滑型破裂为主，但倾滑型破裂也占一定比例；该地区构造应力以水平作用为主，但也存在一定的垂向作用。其中淮北和皖中块体仍可能分别向SWW和NEE方向运动，并在淮河构造变形带上产生左旋剪切作用，呈现一定的继承性活动特征；各块(带)上主压应力P轴走向随时间的变化在总体上较为一致，而各时段之间P轴方位存在一定差异，显示安徽淮河中游区受华北和华南应力场的共同作用，但其地震活动可能主要受控于华北应力场。     

生态最相关水文指标的优选及其在洞庭湖环境流量估算中的应用

水文改变指标(IHA)能够较为全面地描述水文状况,在评估水文情势改变及其生态系统影响方面具有广泛的应用.尽管该指标体系较为完善,但是数量众多的水文变量仍然存在信息冗余问题.根据洞庭湖城陵矶水文站1955-2014年的径流量数据,采用主成分分析(PCA)筛选了生态最相关水文指标(ERHIs),结合ERHIs改进了用于估算环境流量的变化范围法(RVA),并将其应用在洞庭湖出口的环境流量估算中.基于PCA选取了年最大90日流量、年最小3日流量、年最小流量出现时间、3月流量、6月流量、流量逆转次数和低流量年内平均历时7个变量作为洞庭湖出口的ERHIs.纵向和横向的对比分析都表明选取的ERHIs是合理的.ERHIs不仅有效缓解了IHA的冗余性问题,还有利于抓住最关键的生态水文变量.根据ERHIs改进的RVA方法在设定洞庭湖出口环境流量时,极大地简化原来的众多管理目标,对生态水文研究、水资源管理和生态保护都具有重要的参考价值和借鉴意义.     

渤海海域现代构造应力场的数值模拟

根据渤海海域的构造演化背景和地质构造特征建立了该区的二维地质模型,用二维有限元方法计算模拟了渤海海域现代构造应力场,获得了该区构造应力场的分布特征;同时,根据计算结果把渤海海域的构造应力场分为辽东湾、渤中、渤东和渤西等4个区域,并对这4个区域在构造应力场上的差异性进行了描述。从渤海海域整体的应力分布可以看出,该区新近纪以来的断裂活动总体水平上西部较东部强烈,海域东部沿郯庐断裂带仍有较高的断裂发育程度及断裂张开性,而海域中部地区的断层发育程度、活动位移均较低     

中国水质站网规划中几个问题的探讨

在完成中国水质站网规划工作的基础上,对下列问题作了进一步探讨:(1)水质站网规划单元的划分;(2)聚类分析在水质站网规划中的应用;(3)站网密度与人口和经济发展的关系;(4)中国水质站网的分区特征。     

Analysis and study of the large earthquake risk in Yanqing-Huailai basin

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