Tidal and seasonal controls in the formation of Late Miocene inclined heterolithic stratification deposits, western Amazonian foreland basin     

JUSSI HOVIKOSKI  MATTI RÄSÄNEN  MURRAY GINGRAS†  ALCEU RANZI‡  JANIRA MELO‡ 《Sedimentology》2008,55(3):499-530

Upper Miocene strata in the Acre sub‐basin, Brazil, consist dominantly of various types of inclined heterolithic stratification and pedogenic horizons. These strata were sedimentologically and ichnologically described to: (i) study different temporal controls responsible for inclined heterolithic stratification generation and their variation in a distal–proximal trend; and (ii) delineate the depositional setting. For this purpose, nine representative outcrops were sedimentologically and ichnologically studied, and their facies associations described. Thickness variations of the heterolithic strata of various orders (lamina, lamina bundles and beds) were analysed by statistical methods (Fourier transform). The deposits were interpreted as tidally and seasonally influenced estuarine or delta‐related and continental strata. The inclined heterolithic stratification deposits represented vastly different settings ranging from tidally dominated, brackish‐water ichnofossils‐bearing channels to seasonally controlled, articulated Purussaurus (a freshwater alligator) fossil‐bearing channels. Several time cycles were distinguished in the strata, including semi‐diurnal, fortnightly and seasonal. Tidal imprint was best observed in low‐energy brackish‐water settings, whereas seasonal rhythmicity was distinguishable throughout the depositional system. However, the latter was most apparent in riverine channels proximal to the inferred fluvio‐tidal transition. The different temporal controls commonly had distinguishable impact on sedimentological and ichnological properties in the studied sediments. The differing properties included: (i) the degree and nature of lateral variability with respect to lithology and bedforms in inclined heterolithic stratification; (ii) the lateral continuity of inclined heterolithic stratification; (iii) the nature of sedimentary contacts between the inclined heterolithic stratification members; (iv) thickness variation of inclined heterolithic stratification members within a set; (v) the cyclicities observed in inclined heterolithic stratification series; (vi) the degree of bioturbation; (vii) the types of trace fossils observed; and (viii) the distribution of bioturbation in adjacent inclined heterolithic stratification members.  相似文献   

小直径组合桩的波浪力实验分析   总被引：2，自引：1，他引：2  

王爱群  徐立论 《海洋湖沼通报》2002,(1):9-17

本文给出小直径孤立桩、两个桩和2×2个桩的波浪作用力实验结果。在波浪水槽中以0°,45°,90°三个波浪方向测量了各桩所受的纵向力和横向力,文中讨论了组合桩之间的干扰效应,给出了干扰系数随KC数和桩距的变化。  相似文献   

Hydrodynamic Forces on Smooth Inclined Cyh''''nders in Oscillatory Flow     

Kang Haigui Asscociate Professor 《中国海洋工程》1994,(3)

-The hydrodynamic forces on a smooth inclined circular cylinder exposed to oscillating flow were experimentally investigated at Reynolds number (Re) in the range 40000-200000 and Keulegan-Capenter number (KC) in the interval from 5-40. In the test, Re number and KC number were varied systematically. The inertia force coefficient (Cu) and the drag force coefficient (CD) in Morison equation were determined from the measured loads and the water particle kinematics. In this analysis a modified form of Morison equation was used since it uses the normal velocity and acceleration. Thus, the applicability of the Cross Flow Principle was assumed. This principle, simply stated, is as follows: the force acting in the direction normal to the axis of a cylinder placed at some oblique angle with the direction of flow is expressed in terms of the normal component of flow only, and the axial component is disregarded. Both the total in-line force coefficient (CF) and transverse force (lift) coefficient (Cf) were analyzed  相似文献   

Fluid forces on a small cylinder in the presence of a large cylinder in relative oscillatory flow     

C.H.K. Williamson 《Applied Ocean Research》1985,7(3):124-127

The present brief paper is intended to show that the fluid forces on a small cylinder can be considerably magnified when it is in the flow field of a larger cylinder. Two cylinders of unequal diameter are oscillated in a tank of fluid, and the lift and in-line forces on the smaller cylinder are measured when the pair of cylinders is placed at various orientations and spacings.  相似文献   

Hydrodynamic forces on partly buried tandem, twin pipelines in current     

Sevket Cokgor  Ilhan Avci 《Ocean Engineering》2001,28(10):476

This study extends the investigations of the forces on a cylinder, laid on, or partly buried in the bed with a parallel twin dummy cylinder nearby and without it, and were determined by measuring the pressure distribution on the cylinder in the case of a steady current. The pressure distribution around the cylinder was measured by using pressure transducers. The forces on the cylinder were calculated by the integration of the measured pressures on the surface of the cylinder. Force coefficients were obtained for the ranges of Re=0.8×10⁴–1.5×10⁴ for the burial depth to diameter RATIO=0:0.7. The distance between axis of the measurement and dummy cylinders to diameter ratio (x/D) was 2, 1.5 and 1. The dummy cylinder was replaced downstream and upstream of the measurement cylinder.  相似文献   

Inversely-Mapped Analytical Solutions for Flow Patterns around and within Inclined Elliptic Inclusions in Fluid-Saturated Rocks   总被引：1，自引：0，他引：1  

Chongbin Zhao  Bruce E. Hobbs  Alison Ord  Shenglin Peng  Liangming Liu 《Mathematical Geosciences》2008,40(2):179-197

In this paper, an inverse mapping is used to transform the previously-derived analytical solutions from a local elliptical coordinate system into a conventional Cartesian coordinate system. This enables a complete set of exact analytical solutions to be derived rigorously for the pore-fluid velocity, stream function, and excess pore-fluid pressure around and within buried inclined elliptic inclusions in pore-fluid-saturated porous rocks. To maximize the application range of the derived analytical solutions, the focal distance of an ellipse is used to represent the size of the ellipse, while the length ratio of the long axis to the short one is used to represent the geometrical shape of the ellipse. Since the present analytical solutions are expressed in a conventional Cartesian coordinate system, it is convenient to investigate, both qualitatively and quantitatively, the distribution patterns of the pore-fluid flow and excess pressure around and within many different families of buried inclined elliptic inclusions. The major advantage in using the present analytical solution is that they can be conveniently computed in a global Cartesian coordinate system, which is widely used in many scientific and engineering computations. As an application example, the present analytical solutions have been used to investigate how the dip angle of an inclined elliptic inclusion affects the distribution patterns of the pore-fluid flow and excess pore-fluid pressure when the permeability ratio of the elliptic inclusion is of finite but nonzero values.  相似文献   

Break out resistance of inclined anchors in sand     

Shubhra Goel  Shalini  Nihar Ranjan Patra 《Geotechnical and Geological Engineering》2006,24(6):1511-1525

Inclined anchors are widely used in a variety of civil engineering problems to resist oblique loads, most relevant being in transmission towers and in rocks and dams for structural strengthening. In the present study, the breakout resistance of the inclined anchors in sand has been worked out using limit equilibrium approach. The breakout resistance has been calculated for different soil friction angles with varying relative depth ratio and anchor inclination. The break out factor increases continuously with the inclination of the anchor. A comparison of predicted values of break out resistance of anchors by the proposed analysis with the experimental values as reported by the other researchers showed reasonably good agreement.  相似文献   

团树断层场地地震反应的数值模拟     

李山有  王学良  金星  杨柏坡  孙平善 《地震工程与工程振动》2003,23(4):17-21

团树断层场地在多次地震中出现了烈度异常。为了弄清烈度异常的原因，应用显式有限元方法，数值模拟了在脉冲地震波斜入射情形下断层场地的地震反应。结果表明：在基岩山脚附近土层场地地震动放大比基岩山区平均高4倍、比远离基岩山脚土层场地平均高2倍，与历史震害分布有较好的对应。  相似文献   

Experimental Measurements of Solitary Wave Attenuation Over Shallow and Intermediate Submerged Canopy     

王千  郭晓宇  王本龙  房詠柳  刘桦 《海洋工程》2016,(3):375-392

Attenuations of solitary wave over a patch of submerged canopy are experimentally investigated. The submerged canopy is modeled by a group of circular cylinder array. The decay coefficients of different wave heights in two water depths along the wave flume are measured for six canopy models, including two canopy heights and three styles of arrangements. The relationships among the decay coefficient, and the dimensionless wave height, submergence ratio, relative height and arrangement of the canopy are experimentally studied. 2D PIV technique is employed to measure the representative flow field inside the canopy. A four-deck flow structure is proposed for wave flow field over shallow submerged canopy. The characteristics of shear flow inside the aligned canopy region are discussed.  相似文献   

Buckling of multi-segment underwater pressure hull     

J. B&#x;achut  P. Smith 《Ocean Engineering》2008,35(2):247-260

Results of a numerical and experimental study into buckling performance of multi-segment pressure hull subjected to uniform hydrostatic pressure are discussed. Constituents of multi-segment configurations are bowed-out cylindrical shells with, and without flanges. Details about five collapse tests of laboratory scale mild steel, CNC machined models are given. Segments were about 200 mm diameter, 100 mm long and had uniform wall thickness of 3 mm. Experimental collapse pressures were in the range from 12 to 20 MPa. Numerical collapse pressures agreed well with those obtained during experiments.  相似文献