Mapping small-scale along-front structure using ADCP acoustic backscatter range-bin data

A quasi-three-dimensional view of a scallop-shaped river plume front is derived using acoustic Doppler current profiler (ADCP) backscatter measurements recorded in individual range bins. The data show that the scallops consist of broad troughs of plume water separated by narrow cusps of ambient water and have an along-front wavelength of about 13 m. Having this view across such an inhomogeneous region is helpful in interpreting the corresponding ADCP velocity measurements, so that an examination of just those ADCP profiles made in the ambient water shows the expected strong sinking motion, which reaches about 25 cm s^?1 at 1–2-m depth.     

分层密度流体的边界波动在不透水刚性底床的运动行为——Ⅰ造波条件对波型演化的关系

在一座二维内波实验水槽(12 m×0.7 m×0.5 m)、于总水深H等于40 cm的条件下,以淡、盐水依密度分层布置的两层流体,从事孤立内波生成的研究。内波水槽内的上下层水深比H₁/H₂、造波区位能差(η₀)、上下层的密度比皆为实验主要的控制变因。在各种不同实验条件配合之下,试验及比较以上变因对内波振幅能量及相关传递系数的影响,进而产生几种不同的波动特性:上举型孤立内波、下沉形孤立内波、非周期性的重力内波等,且不同形式的重力内波需要配合固定的造波条件使能达成。     

Assessment of acoustic backscatter intensity surveying on deep-sea ferromanganese crust: Constraints from Weijia Guyot,western Pacific Ocean

Near-bottom observation data from the manned deep submersible Jiaolong with high-precision underwater positioning data from Weijia Guyot, Magellan Seamounts in the Western Pacific Ocean are reported. Three substrate types were identified: Sediment, ferromanganese crust, and ferromanganese crust with a thin cover of sediment. The ferromanganese crusts show clear zoning and their continuity is usually disturbed by sediments on areas of the mountainside with relatively gentle slope gradients. The identified substrate spatial distributions correspond to acoustic backscatter intensity data, with regions of high intensity always including crust development and regions of low intensity always having sediment. Therefore, acoustic backscatter intensity surveying appears useful in the delineation and evaluation of crust resources, although further more work is needed to develop a practicable methodology.     

松辽盆地保乾三角洲前缘带演变及其勘探意义

岩性油藏是松辽盆地最主要油藏类型之一,而三角洲前缘带是形成岩性油藏的有利相带。通过保乾三角洲沉积体系在不同地质时期沉积微相和沉积模式的深入研究,动态再现了保乾三角洲前缘带的演化过程。前缘带砂体经历了退积、进积和大规模迁移三个过程,物源方向总体由西南向西北方向逐步迁移,三角洲朵体形态由“深湖型”朵叶式逐步转变为“浅湖型”树枝式。保乾三角洲前缘带不同沉积时期的迁移规律对岩性油藏的勘探具有重要指导意义。     

分层密度流体的边界波动在不透水刚性底床的运动行为——Ⅱ分层条件对传动波型的影响

在两层流体中,内波的特性受到许多控制变因的影响,其中包括上下层水深比、造波区位能差(位能大小)、上下层的密度比等。本文以成功大学水工试验所研发的MNDAS套装软件记录,协助数据分析及处理,研究上下层水深比对内波波型的影响,当水深比值差异越大造成的孤立波形与明显,且Kdv及修正mKdV可以合理描述内波振幅与频率之间的关系。     

喀斯特地区嵌岩混凝土摩擦桩的反算

云南南盘江大桥为7跨预应力钢构连续桥, 1、2号墩为桩基,采用人工挖孔灌注桩。No. 2嵌岩桩底下部12m处为强风化白云岩。对拟定的端承区域勘探发现在桩底的岩石- 混凝土接触区域有一溶洞,溶洞高约20m,垂直发育,洞底有粘土、碎石土充填,结构松散,粘土为软塑状。东南大学采用与O-cel l试验类似的平衡内部千斤顶系统进行了桩的荷载实验。O-cell试验安装在距桩底12m处,即靠近桩下部的弱风化与强风化岩石之间的接触区域。本文阐述了O-cell试验数值分析中用来反算桩体/岩石交接区域特性的部分。采用的数值分析软件为BAQUS,版本6. 4 ( ABAQ US, 2004) 。同时采用二维轴对称模型来对桩径2. 5m、桩长49m的钻孔桩进行O-cell试验数值模拟。假设加载的钻孔桩的变形与屈服发生在混凝土桩体与岩石的交接区域,混凝土桩为线弹性,强风化白云岩与弱风化白云岩为弹- 塑性,并可用Drucker- Prag er 模型( ABAQUS, 2004)表示,对岩石和混凝土- 岩体接触面的特性进行反算,然后用反算结果模拟桩顶荷载特征。数值模拟计算和现场载荷试验检测的载荷- 位移曲线对比表明,除了非弹性和永久变形外,整个向上与向下的变形与试验检测到的值基本相同。这主要是由于接触面模型的弹性性质所决定的,即它在卸载过程中会将滑动的接触面复原;而永久变形是岩体-混凝土接触面屈服的结果。必须指出的是,由于桩的承载力相对较高( 2. 5m桩径,嵌岩长度37m) ,试验不能达到最终荷载, 所以检测到的变形也较小( <10mm)。分别在桩端、O-单元荷载盒上37m处检测向上弯沉,并将结果与O-单元荷载盒顶部的弯沉作比较。结果发现,由于桩是由O-单元荷载盒底部向上加载,所以桩端的弯沉预计比O-单元荷载盒的弯沉小约5mm。这一差值几乎等于施加荷载状态下无限制(Δ= P L /A E )桩体的理论弹性缩短量。通过O-cell现场试验可以有效地观测加载状态下荷载弯沉反应情况和调整或校准数值分析中的材料模型,并可将之推广应用到相同地质条件下类似项目施工的其它桩的反应过程中。此外,还可以通过溶洞区域中的高承载力桩的O-cell试验结果来构建桩体摩擦反应的模型; 在模型摩擦反应基础上,可以估计桩端预计的变形反应值; 在交接面反应中,可以采用正弦接触面有效地引入人工粘结和表面粘结。      

Preliminary observation of a tidal intrusion front inside the mouth of the Chesapeake Bay

In situ sampling during flooding tidal flow and southerly winds shows the up-estuary translation of a surface front along the Thimble Shoal channel, which is located in the southern part of Chesapeake Bay. Currents and surface density were measured using a towed acoustic Doppler current profiler and CTD, and a ship-borne radar was used to monitor the orientation and planform of the front, which varied over time. These preliminary observations suggest that dense shelf water, upwelled to the surface along the coast near Cape Henry, Virginia, can be found well into the southern part of the bay during flood, and that the boundary between the intruding shelf water and less dense estuarine water has many of the same characteristics as tidal intrusion fronts found in smaller scale estuaries.     

Geomorphology of a modern carbonate slope system and associated sedimentary processes: Example of the giant Great Abaco Canyon,Bahamas

The large acoustic data set acquired during the Carambar cruises is composed of high resolution bathymetry, backscatter data and very‐high resolution seismic lines which allow for an overview of the morphology and sediment transfer processes from the shallow upper slope to the abyssal plain of a modern carbonate system: the north‐eastern slope of the Little Bahama Bank. Surficial distribution of the acoustic facies and echofacies reflects a wide variety of sedimentary processes along and across the slope. The western sector of the Little Bahama Bank is dominated by depositional processes whereas its eastern sector, which is incised in the lower slope by giant canyons, is affected by erosion and bypass processes. Datasets suggest that currents play an important role both in along‐slope sedimentary processes and in the abyssal plain. The Antilles Current appears to affect a large part of the middle and lower slopes. The absence of sizeable present‐day channel/levée complexes or lobes at the mouth of the canyon – revealed by the bathymetric map – indicates that the southward flowing Deep Western Boundary Current influences modern abyssal sediment deposition. Based on depositional processes and indicators of canyon maturity observed in facies distribution, the current study proposes that differential subsidence affects the eastern versus western part of the bank. The morphology of the Great Abaco Canyon and Little Abaco Canyon, which extend parallel to the platform, and the Little Bahama Bank slope appears to be related to the Great Abaco Fracture Zone.     

复杂深海工程地质原位长期监测系统研发与应用

海底滑坡、浊流等深海底地质灾害严重威胁海洋工程安全,是国家深海开发亟待解决的风险问题。为避免深海海底地质灾害对海底工程造成危害,解决深海海底地质灾害监测预警的难题,我们研发了一套复杂深海工程地质原位长期监测系统。该系统通过声学、电阻率、超孔隙水压力等方法监测深海海底沉积物的物理力学性质变化,实现了对深海海底地质灾害的监测和预警。该系统主要包括海床基搭载平台、监测系统、通信控制系统、供电系统等。其中监测系统主要通过原位长期监测海底沉积物的电阻率、声学、超孔隙水压力等的变化来获取海底沉积物的物理力学性质变化;通信控制系统可以实现海底到海面,再到陆地的双向通信和数据传输。其中供电系统通过独特设计的海水电池工艺,可以满足该系统在海底长期工作一年的电量需求。复杂深海工程地质原位长期监测系统已完成了近海测试,并搭载“海洋地质六号”“东方红三号” “张謇号”等科考船在南海进行了多次远海海试,获取了丰富的实测数据。电阻率监测系统采用温纳法滚动测量,测得的水土界面位置平均电阻率为0.207 Ω·m。超孔隙水压力监测系统采用开放式结构的压差式光纤光栅孔压测量方法,监测到孔压观测的4个标志性阶段:(1)贯入过程引起的超孔隙水压力累计,峰值为34.942 kPa,历时0.182 h;(2)贯入完成后累积的超孔隙水压力衰减,衰减到9.973 kPa,历时为0.810 h;(3)环境应力引起的超孔隙水压力实时响应,超孔隙水压力的变化范围为8.327~14.384 kPa;(4)残余孔隙水压力平均值为11.150 kPa。声学监测系统采用两个一发三收模式,测量的海水平均声速为1 533 m/s,测量的海底沉积物自上而下的平均声速依次为1 586、1 587、1 784、1 735、1 831 m/s。复杂深海工程地质原位长期监测系统的成功研制将显著提升目前海洋工程地质原位长期观测的技术能力,解决复杂深海工程地质评价及地质灾害监测预警的技术难题。     

超磁致伸缩声波震源的时频特征与实测研究

宽频带、大功率、短余振声波震源是高分辨率探测大尺度复杂结构体的关键技术,为了解决探测距离与其分辨率的矛盾问题,采用超磁致伸缩材料制作的声波发射器作为震源,研制了一种新的声波探测仪器。该震源中心频率为5 kHz,激励电压300~600 V,具有辐射声功率大、余振短（3.5个周期）、频带宽（1~3 kHz）的特性;其最大的优点是每次激发的声波信号一致性好,可以采用单点多次激发,通过多次叠加的数据处理技术提高信噪比,较好地解决了声波探测距离与分辨率的矛盾,并成功地应用于煤矿采场顶煤厚度探测。现场探测结果表明:大功率声波探测系统能够有效提取4~7 m煤岩交界面的反射波信号,借助于小波多分辨分析信号处理方法,有效地提高了采场顶煤厚度探测的精度及其可靠性,为顶煤厚度精确探测提供了一条有效途径。      

三峡库区大型单斜顺层新生滑坡变形特征与失稳机理研究

以三峡库区巫山轿顶峰2号滑坡为例,结合库水位变化、地质环境条件资料,通过现场调查测绘、无人机航空摄影测量、工程地质钻探、地表及深部位移监测等方法,详细分析了该滑坡的变形特征、成因机制与发展趋势.该滑坡体积约250×104 m3,为大型单斜顺层新生岩质滑坡.滑坡前后缘高差约380 m,前缘剪出口高陡临空,位于库区蓄水位以...     

Mapping Benthic Habitats in Delaware Bay and the Coastal Atlantic: Acoustic Techniques Provide Greater Coverage and High Resolution in Complex, Shallow-Water Environments

Accurate benthic habitat maps are critical for resource management in coastal waters with competing uses. We used a 500 kHz phase-measuring bathymetric sonar (PMBS) and 900 kHz side-scan sonar to acquire seafloor data in estuarine and shelf environments. Grab samples and remotely operated vehicle video created geological and biological classifications for segmented maps produced by a backscatter clustering program. PMBS improves regional map resolution (<1 m), reduces the need for direct sampling, extends information on sediment–biological relationships to larger areas, and allows measurements of bedforms. Auto-segmentation was successful in environments with highly contrasting acoustic signatures and meters-scale homogeneity. Patchier communities are identifiable in PMBS data. Species preferences for sediment (i.e., tubeworm preference for sediment without shell hash) allowed us to determine potential habitat without identifying individual organisms in acoustic data. PMBS with sufficient ground-truthing offers an efficient way to map seafloor characteristics, which is critical in marine spatial planning efforts.     

Clinoform development and topset evolution in a mud‐rich delta – the Middle Triassic Kobbe Formation,Norwegian Barents Sea

Clinoform surfaces are routinely used to mark transitions from shallow waters to deep basins. This concept represents a valuable tool for screening potential reservoir intervals in frontier basins where limited data are available. Variations in the character of clinoform geometries and shoreline and shelf‐edge trajectories are indicators of a range of different factors, such as palaeobathymetry, changes in relative sea‐level and sediment supply. Applications of conceptual and generalized models might, however, lead to erroneous assumptions about the supply of coarse‐grained material to the delta front and basin when superficial similarities between clinoform geometries are not treated holistically. The present study examines the mudstone‐dominated Middle Triassic Kobbe Formation – a potential hydrocarbon reservoir interval in the Barents Sea, where prodeltaic to deltaic deposits can be examined in cores, well logs and two‐dimensional and three‐dimensional seismic data. Despite pronounced acoustic impedance contrast to the surrounding shale, channel belt networks are not observed close to the platform edge in seismic datasets, even at maximum regressive stages. However, sub‐seismic prodeltaic deposits observed on the shallow platform indicate that prodeltaic deposits were sourced directly from the delta plain. Clinoform surfaces with different geometries and scale are observed basinward of the palaeoplatform edge of underlying progradational sequences, correlative to mudstone‐dominated prodeltaic core sections. Results indicate that platform‐edge deltas developed at discrete sites in the basin due to normal regression, but the positions of these deltas are not directly relatable to variations in clinoform geometries. Transitions from third‐order to fourth‐order clinoform geometries record discrete transgressive–regressive cycles but are not necessarily good indicators of sandstone deposition. Because of prolonged periods with high accommodation, channel avulsions were frequent and only very fine‐grained sandstone was deposited in heterolithic units at the delta front. Sandstones with good reservoir properties are predominantly found along basin margins.     

兴蒙造山带正 （ Nd，t）值花岗岩的成因和大陆地壳生长

“野外地质掌中宝”系统是以WindowsCE为软件平台 ,以掌上电脑为硬件载体 ,适用于野外地质勘探和国土资源调查的便携式工作平台。它包括前端工具软件包、后台伺服处理子系统、通讯子系统以及硬件接口软件等。该系统的开发研究将是以信息高新技术改造传统的野外地质勘探和国土资源调查技术的一次重要实践 ,它的研制成功将为野外地质工作者提供面向2 1世纪的高效、实用、方便的现代化工作平台     

“野外地质掌中宝”系统的及其应用

“野外地质掌中宝”系统是以Ｗｉｎｄｏｗｓ ＣＥ为软件平台,以掌上电脑为硬件载体, 适用于野外地质勘探和国土资源调查的便携式工作平台。它包括前端工具软件包、后台伺服处理子外地质勘探和国土资源调查技术的一次重要实践,它的研制成功将为野外地质工作才提供面向２１的高效、实用、方便的现代化工作平台。     

矿井分布式地震超前探测系统研究与应用

为探测掘进巷道前方地质构造，研制一套矿井分布式地震超前探测系统。系统基于地震波反射理论，通过检波器分布式接收或震源分布式激发确定地质异常体的位置。为了进一步提高煤矿采掘过程中构造的预测预报精度，采用分布式观测系统和孔中胶囊检波器进行数据采集以提高设备的灵敏度，通过负视速度原理排除侧帮和后方地质异常体的干扰，利用绕射共偏移算法优化数据反演成果。经过大量试验验证和归纳总结，该系统采用人工锤击震源可有效探测出前方70 m范围内的地质异常信息，采用人工炸药激发震源可有效探测出前方150~200 m范围内的地质异常信息。研究结果表明，矿井分布式地震超前探测系统通过从硬件到软件优化，可实现采掘过程中对地质构造的探测精度，并提高探测效率。      

Diagenesis of late Cenozoic diatomaceous deposits and formation of the bottom simulating reflector in the southern Bering Sea*

Diatom ooze and diatomaceous mudstone overlie terrigenous mudstone beds at Leg 19 Deep Sea Drilling Project sites. The diatomaceous units are 300-725 m thick but most commonly are about 600 m. Diagenesis of diatom frustules follows a predictable series of physical and chemical changes that are related primarily to temperature (depth of burial and local geothermal gradient). During the first 300-400 m of burial frustules are fragmented and undergo mild dissolution. By 600 m dissolution of opal-A (biogenic silica) is widespread. Silica reprecipitates abundantly as inorganic opal-A between 600 and 700 m sub-bottom depth. Inorganic opal-A is rapidly transformed by crystal growth to opal-CT. The result is formation of silica cemented mudstone and porcelanite beds. A regional acoustic reflector (called the bottom-simulating reflector, or BSR) occurs near 600 m depth in the sections. This acoustic event marks the upper surface where silicification (cementation) is active. In Bering Sea deposits, opal-A is transformed to opal-CT at temperatures between 35° and 50°C. This temperature range corresponds to a sub-bottom depth of about 600 m and is the area where silicification is most active. Thus, the BSR represents an isothermal surface; the temperature it records is that required to transform opal-A to opal-CT. Deposition of at least 500 m of diatomaceous sediment was required before the temperature at the base of the diatomaceous section was appropriate (35°-50°C) for silica diagenesis to occur. Accordingly, silica diagenesis did not begin until Pleistocene time. Once silicification began, in response to sediment accumulation during the Quaternary, the diagenetic front (the BSR) moved upsection in pace with the upward migrating thermal boundary. X-ray diffractograms and SEM photographs show three silica phases, biogenic opal-A, inorganic opal-A’, and opal-CT. These have crystallite sizes of 11-16 A, 20-27 A, and 40-81 A, respectively, normal to 101. The d(101) reflection of opal-CT decreases with depth of burial at DSDP Site 192. This occurs by solid-state ordering and requires at least 700 m of burial. Most clinoptilolite in Leg 19 cores forms from the diagenesis of siliceous debris rather than from the alteration of volcanic debris as is commonly reported.     

不同胶结情况下套管井中声场激发谱的研究

采用实轴积分法计算套管刻度井中的声场激发谱,分析了第一、第二界面的胶结情况以及模拟地层的厚度等对井内声场的影响。数值结果显示：在套管刻度井中,模拟地层厚度的增大或第一、第二界面的胶结状况变差,该地层的外边界对井中激发谱的影响变小,在低频（小于3 kHz）情况下,当外边界半径大于0.2 m时,不管第一、第二界面胶结状况如何,该边界面对井中激发谱的影响基本可以忽略;在设计套管刻度井时,为减小模拟地层的外边界对井内声场的影响,既要考虑不同胶结情况下模拟地层的厚度问题,还应考虑声源测量频率的影响问题。     

声学多普勒剖面仪对悬浮沉积物浓度的测量研究

为探讨声学多普勒剖面仪(PCADP)测量悬浮沉积物浓度(SSC)的可行性,将PCADP测量输出的声学后散射强度经衰减修正后,通过光学浊度计(OBS)标定转变为SSC.结果表明,SSC与后散射强度之间具有较好的相关性(R=0.74),用后散射强度测得的SSC平均相对误差为22.4%.为排除粒径变化对声学测量误差的影响,又对粒径变化不是很大的时段进行了分析,结果相关性有了较大提高(R=0.81),平均相对误差减小为18.9%.由此可见,PCADP能够达到专业SSC测量仪器的精度(20%~50%),满足沉积动力学研究的需要.     

Lobe construction and sand/mud segregation by turbidity currents and debris flows on the western Nile deep-sea fan (Eastern Mediterranean)

Based on an unusual data set comprises bathymetric data, backscatter imagery, seismic-reflection and Chirp profiles, and sediment cores, the Late Quaternary lobe at the mouth of the youngest turbidite channel off the western Nile deep-sea fan was investigated. The large-scale construction of the lobe through time and space is mainly controlled by 1) a pre-existing topography inherited from the downslope movement of Messinian evaporites, and 2) the type and nature of gravity flows delivered to the basin floor. The margins of the lobe are defined by high-backscatter acoustic facies that contrasts strongly with the low-backscatter facies from the surrounding abyssal-plain deposits. Within the lobe, low-backscatter facies characterise the main channel-levee systems and lobate bodies immediately beyond the end of the channels. Cores reveal that the high-backscatter facies corresponds to a series of extensive but thin debris-flow deposits with a fingered margin. These debrites comprise a muddy-sand matrix and dispersed clasts with diameter of 5 to 10 cm. The lower backscatter facies at channel mouths corresponds to alternations of thin sandy turbidites and muddy hemipelagites. Extensive thin debris flows therefore traversed surprisingly low gradients to reach the distal fringes of the lobe complex but are never found in the lobate bodies just beyond the channel mouths. Although the Nile deep-sea fan is considered as a silt/mud-rich accumulation, sand-prone deposits exist within the lobe. This sand/mud segregation results either from the presence of channelized features in the lobe and/or from the hydrodynamic process of particle transport by debris flows and turbulent flows.