胶州湾悬浮颗粒现场剖面测量与结果分析   总被引：6，自引：0，他引：6  

魏建伟  石学法  方习生  张伟滨  王宗灵 《海洋科学进展》2006,24(1):74-82

应用LISST-100现场激光粒度仪于2003年3月在胶州湾首次进行了悬浮颗粒剖面测量,获得了2个剖面的悬浮颗粒现场粒度分布光衰减资料。2个剖面的悬浮颗粒分布自上而下非常相似,颗粒平均大小多为38~74μm,其中1~20μm细颗粒组分所占的比重高。水柱表层悬浮颗粒略粗于底部悬浮颗粒,而且内湾悬浮颗粒比外湾粗。水柱近底层悬浮颗粒粒径同底质浮泥颗粒粒径大小相近,颗粒组成也非常相似。悬浮颗粒浓度自上而下逐渐增大,接近底部颗粒浓度急剧增高。根据现场测量数据可以马上对悬浮颗粒有效密度、颗粒沉降速率和通量做粗略估算。分析结果表明,光衰减系数同颗粒浓度显著相关,推断光衰减主要是由1~250μm悬浮颗粒的散射作用引起的,而<20μm的悬浮粒子对光衰减作用起着主要控制作用。光衰减系数与颗粒投影面积显著相关,表明颗粒投影面积可以作为遥感离水反射率的替代指标。  相似文献   

Wave Attenuation Performance and the Influencing Factors of A Lower Arc-Plate Breakwater     

LI Xue-yan  WANG Qing  YOU Zai-jin  GUO Wei-jun  ZHANG Jun-bin  ZHAN Chao  ZHANG Zhi-chen  WANG Li-xue  LI Qin 《中国海洋工程》2020,(1):89-98

Comprehensive experimental and numerical studies have been undertaken to investigate wave energy dissipation performance and main influencing factors of a lower arc-plate breakwater. The numerical model, which considers nonlinear interactions between waves and the arc-plate breakwater, has been constructed by using the velocity wave- generating method, the volume of fluid (VOF) method and the finite volume method. The results show that the relative width, relative height and relative submergence of the breakwater are three main influencing factors and have significant influence on wave energy dissipation of the lower arc-plate open breakwater. The transmission coefficient is found to decrease with the increasing relative width, and the minimum transmission coefficient is 0.15 when the relative width is 0.45. The reflection coefficient is found to vary slightly with the relative width, and the maximum reflection coefficient is 0.53 when the relative width is 0.45. The transmission and reflection coefficients are shown to increase with the relative wave height for approximately 85% of the experimental tests when the relative width is 0.19 0.45. The transmission coefficients at relative submergences of 0.04, 0.02 and 0 are clearly shown to be greater than those at relative submergences of 0.02 and 0.04, while the reflection coefficient exhibits the opposite relationship. After the wave interacts with the lower arc-plate breakwater, the wave energy is mainly converted into transmission, reflection and dissipation energies. The wave attenuation performance is clearly weakened for waves with greater heights and longer periods.  相似文献   

Experimenta l study on ultrasonic propagation in water-based bentonite slurry          下载免费PDF全文

LAN Kai  YAN Taining 《世界地质(英文版)》2009,12(3):174-178

Drilling fluid is a common flushingmedium used in pile foundation, geological drilling and petroleum drilling. Study on ultrasonic propagation properties in drilling fluid is of vital importance, not only for developing equipments to non-contact measuring concrete casting level for bored pile, but also for developing equipments considering drilling fluid as signal channel. The existence of clay particlesmakes the ultrasonic propagation and attenuation in drilling fluid much different from pure water. In order to know the relation among ultrasound frequency, slurry density and depth, a series of laboratory experiments about ultrasound propagation in water-based bentonite slurry were finished. Wavelet method was adopted to process the gained original waves of ultrasonic propagation in slurry, so we knew the velocity and attenuation coefficient of ultrasound propagated in different drilling fluids with different density. The first group experiments shows that with density of drilling fluid increase, ultrasonic velocity will decrease but attenuation coefficient will increase if ultrasonic frequency keep constant. The second group experiments shows that the power of ultrasound will intensify in small bore hole, the attenuation coefficient ismuch smaller than theoretical value.  相似文献   

Development of in-situ Marine Sediment Geo-Acoustic Measurement System with Real-Time and Multi Frequencies （the Second Generation）   总被引：1，自引：0，他引：1  

陶春辉  邓显明  李红星  周建平  金肖兵  傅顺声  Wilkens  R.  H  顾春华  何拥华 《中国海洋工程》2009,23(4):769-778

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基于同轴差距测量法的南海深水海底沉积物声衰减特性研究   总被引：4，自引：3，他引：1  

邹大鹏  卢博  吴百海  梁润华  陈飞燕 《热带海洋学报》2009,28(3):35-39

通过分析沉积物声波测量过程能量损失的实质,阐述平行轴差距衰减测量法和垂直轴差距衰减测量法的研究基础——差动式衰减测量方法原理,并推导了其衰减系数公式。根据南海沉积物的柱状样品分装的特点,结合以上两种方法,提出了同轴差距衰减测量法,这种方法具有原理上的合理性并且其可操作性强;运用此方法测量了沉积物在常温和温度控制变化条件下的声波信号,计算了衰减系数,研究了温度对沉积物声波传播能量的影响,得出南海深水海底沉积物具有以下声衰减特性：沉积物含砂量高,声衰减系数大;随着温度的升高,沉积物的声衰减系数变化具有不均匀性,整体呈非线性减小趋势。以上研究将为声学遥测和反演海底沉积物的物理力学特性提供数据和方法支持。  相似文献   

多极子声波测井在低孔低渗气层中的数值研究   总被引：3，自引：1，他引：2       下载免费PDF全文

陈雪莲  王瑞甲 《地球物理学进展》2007,22(6):1836-1840

现有的天然气勘探中的测井技术,在评价低孔低渗气层时遇到诸多难题,本文引入了一种新的气藏评价方法,即利用多极源激发的模式波的幅度来识别气藏,并对此方法进行了数值验证.以Biot多孔介质理论为基础建立了低孔低渗含气储层计算模型,数值计算了多极子声源在充液井孔中激发的频散曲线、衰减曲线以及全波列波形.结果表明,挠曲波和螺旋波的衰减系数与相速度相比,对孔隙中的流体性质更敏感,且随着多极源级数的增加和工作主频的提高,挠曲波和螺旋波的衰减系数的变化程度明显增强;在偶极子和四极子激发的全波列波形中,可清晰的观测到对地层孔隙流体不敏感的地层横波,在这种情况下,可以通过对比波列中地层横波和频散的弯曲波(或螺旋波)幅度来识别气层.  相似文献   

四川及邻区地震动衰减关系   总被引：29，自引：3，他引：26       下载免费PDF全文

雷建成  高孟潭  俞言祥 《地震学报》2007,29(5):500-511

根据地震构造环境和震害分布特点, 将四川及邻区划分为西南地区和四川盆地地区. 收集了西南地区96次、 四川盆地地区40次近代破坏性地震资料, 并对各次地震的震级参数进行了统一校核. 按照该地区震中烈度与震级、 有感半径与震级的统计关系, 对地震烈度衰减进行了近场与远场特征控制, 建立了地震烈度沿长轴、 短轴和平均轴的衰减关系. 统一了中国与美国面波震级的震级标度, 利用最新得出的美国西部基岩水平向地震加速度反应谱衰减关系, 采用考虑地震加速度的近场距离饱和与震级饱和特征的衰减模型, 转换得到了该地区的基岩水平向地震加速度反应谱衰减关系.   相似文献   

Preliminary results of seismic hazard assessment in the Sannio-Matese area of Southern Italy     

M. S. Barbano  F. Colombo  G. Zonno 《Natural Hazards》1989,2(3-4):307-328

The seismic hazard in the Sannio-Matese area has been worked out by a modification of the McGuire (1976) computing programme, taking into account the influence of nine potential seismic source zones.The method uses truncated-quadratic intensity-frequency distribution and azimuth-dependent intensity attenuation derived from isoseismal maps for each of the seismogenetic sources. A new modification has been introduced to take into account different decay of the intensity in the near (to VIII degree) and far (from VIII degree) field.Different assumptions about maximum possible intensities and truncation of intensity-frequency laws are used to evaluate the effects of the uncertainties on the computed hazard at high intensities. Intensities associated with different level of annual probability are computed for five test sites in the considered area. Maps displaying the expected intensity for a mean return period of 500 years (pa 0.002) are presented and compared with observed intensities.Presented at the XXIst General Assembly of the European Seismological Commission, Symposium on Methods of Seismic Hazard Assessment in Europe, Sofia, 23–27 August 1988.  相似文献   

Seismic wave attenuation in fluid-saturated porous media     

James G. Berryman 《Pure and Applied Geophysics》1988,128(1-2):423-432

Contrary to the traditional view, seismic attenuation in Biot's theory of fluid-saturated porous media is due to viscous damping of local (not global) pore-fluid motion. Since substantial inhomogeneities in fluid permeability of porous geological materials are to be expected, the regions of highest local permeability contribute most to the wave energy dissipation while those of lowest permeability dominate the fluid flow rate if they are uniformly distributed. This dichotomy can explain some of the observed discrepancies between computed and measured attenuation of compressional and shear waves in porous earth. One unfortunate consequence of this result is the fact that measured seismic wave attenuation in fluid-filled geological materials cannot be used directly as a diagnostic of the global fluid-flow permeability.  相似文献   

Theoretical background for the inversion of seismic waveforms including elasticity and attenuation   总被引：3，自引：0，他引：3  

Albert Tarantola 《Pure and Applied Geophysics》1988,128(1-2):365-399

To account for elastic and attenuating effects in the elastic wave equation, the stress-strain relationship can be defined through a general, anisotropic, causal relaxation function ^ijkl (x, ). Then, the wave equation operator is not necessarily symmetric (self-adjoint), but the reciprocity property is still satisfied. The representation theorem contains a term proportional to the history of strain. The dual problem consists of solving the wave equation withfinal time conditions and an anti-causal relaxation function. The problem of interpretation of seismic waveforms can be set as the nonlinear inverse problem of estimating the matter density (x) and all the functions ^ijkl (x, ). This inverse problem can be solved using iterative gradient methods, each iteration consisting of the propagation of the actual source in the current medium, with causal attenuation, the propagation of the residuals—acting as if they were sources—backwards in time, with anti-causal attenuation, and the correlation of the two wavefields thus obtained.  相似文献