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南海北部湾海洋工程地质特征 总被引：8，自引：0，他引：8
根据地球物理、声学探测及海底取样等实测资料详细分析,发现北部湾油气勘探开发区具有近岸、水浅等优越自然条件以及复杂的海洋工程地质特征。海底地形地貌较为复杂,存在潮流沙脊与潮沟、海底沙坡、埋藏古河道、浅层气、埋藏古陡坡、滑塌断层及可能的砂土液化层等潜在灾害地质因素,对海上构筑物存在直接或潜在的危险性。尤其在东部,海底坎坷不平,活动性的潮流消脊、侵蚀沟槽、海底沙波及浅层气等很发育,是海底工程建设的危险区,应引起高度重视。 相似文献
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A fully nonlinear domain decomposed solver is proposed for efficient computations of wave loads on surface piercing structures in the time domain. A fully nonlinear potential flow solver was combined with a fully nonlinear Navier–Stokes/VOF solver via generalized coupling zones of arbitrary shape. Sensitivity tests of the extent of the inner Navier–Stokes/VOF domain were carried out. Numerical computations of wave loads on surface piercing circular cylinders at intermediate water depths are presented. Four different test cases of increasing complexity were considered; 1) weakly nonlinear regular waves on a sloping bed, 2) phase-focused irregular waves on a flat bed, 3) irregular waves on a sloping bed and 4) multidirectional irregular waves on a sloping bed. For all cases, the free surface elevation and the inline force were successfully compared against experimental measurements. 相似文献
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This article introduces the application of a stability analysis method that accounts for strength anisotropy on the embankment constructed at the Kobe airport. Shear strength anisotropy is induced by the in-situ state of stress along a potential slip surface of the embankment. In addition, the effects of the shearing rate on the undrained shear strength of the marine clay are examined in detail based on the results of a series of constant-volume direct shear box (DSB), triaxial compression (TC), and triaxial extension (TE) tests varying shearing rates. The most critical slip surface was selected from the deterministic slope stability analysis using unconfined compression tests of undisturbed clay samples from the field. For the most critical slip surface, the potential factor of safety of the embankment is estimated to be within the range of 1.21 to 1.28, as indicated by the results of the stability analyses using the strengths obtained from the DSB, TC, and TE tests and varying shearing rates. 相似文献
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Coastal cliffs at Kvalvågen, eastern Spitsbergen, expose palaeolandslide blocks and related slope failure features that record local collapse of an otherwise undisturbed succession of paralic sediments. The collapse occurred along a shallow sloping shelf at the edge of an epicontinental sea in the Early Cretaceous. The event was coincident with a rise in relative sea level along a coast that had just previously experienced a major paralic regression across a muddy marine environment. The low relief environment in which the slope failure structures formed, as well as the timing of the collapse raise questions regarding the cause of the topographic instability and the possible influence of sea level changes or tectonic activity. These outcrops have been previously interpreted as the collapse of a deltaic system triggered by local seismic activity or collapse of a shelf break in the headwall regions of submarine canyons. This paper presents new structural and stratigraphic data that refine and adjust the previous interpretations through the evaluation of a variety of possible mechanisms for collapse based on the new data. Our data suggest that active delta deposition was not occurring at Kvalvågen at the time of collapse and that the collapse was likely due to allogenic forcing. Despite the possible influence of pore fluids and rheological controls on the collapse, we find that the geometry and kinematics of landslide slip planes, synsedimentary folds, and other slope failure related features require over-steepened topography and that these are most consistent with westward-directed collapse off of a north striking escarpment with elevated topography on the east side. Fault exposures, a large contrast in palaeo-elevation, and liquifaction features support previous interpretations of a tectonic cause for the collapse and suggest that this topographic feature may have been a fault or fold scarp. This study demonstrates the importance of combining stratigraphic and sedimentological data with structural data and kinematic analysis in the interpretation of sedimentary processes. 相似文献
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Qiu Changlin Yan Shuwang
Graduate student Dept. of Hydraulic Engrg. Tianjin University .
Professor Dept. of Hydraulic Engrg. Tianjin University 《中国海洋工程》1996,(4)
- This paper presents a procedure to calculate the safety factor against sliding of a marine gravity structure subjected to a combination of static and cyclic loads. This procedure claculates the stress at the sliding surface by the finite element method (FEM) and takes the dynamic properties of clay into account. With this procedure, the stability of a Bohai oil-drilling ship is analyzed. The calculated safety factor is much smaller than 1, indicating that this oil-drilling ship would fail just as what had happened to it. 相似文献
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海洋资源开发引起海底软黏土的结构性破坏,导致土体强度弱化,在百年一遇的极端波浪作用时极易发生斜坡海床的局部失稳甚至大范围海底滑坡,给海洋工程建设和正常运营带来严重影响。目前,主要采用极限平衡法评价这类海底斜坡,但该法只能给出近似解。基于极限分析上限方法,推导了极端波浪诱发的波压力对斜坡海床的做功功率,建立了外力功与内能耗散率平衡方程;利用最优化方法,结合数值积分和强度折减技术,求解了不同时刻的斜坡海床稳定性系数,并针对扰动后的斜坡海床开展了有限元解的对比验证。在此基础上,深入探讨了不同波浪参数(波长、波高和水深)和坡长小于一个波长等极端条件下的海底斜坡稳定性。 相似文献
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《Ocean Engineering》1995,22(4):301-315
The dynamic forces of sea water and backfill soil acting on coastal embankments and the hydrodynamic forces on offshore breakwaters have been analyzed using a finite-difference scheme. A non-horizontal sea bottom is considered in the analysis. Both rigid and flexible embankments are included in the study. For a coastal embankment, the hydrodynamic pressure of sea water acting on the embankment face significantly increases as the slope of the sea bottom increases. On the other side of the embankment, the pore pressure and the interaction force between the soil and fluid will augment significantly when the backfill soil is compressed during earthquakes. When the sea-embankment-backfill soil interaction is included, the dynamic forces acting on a flexible embankment are much larger than those on a rigid one. The comparison of evaluating the sliding of a cassion in a case study of SPM by a conventional analysis and the present seismic analysis was made. The earthquake-induced dynamic pressures on both sides of the embankment (or breakwater) could be much larger than the force generated by the storm surge. The hydrodynamic (or seismic) analysis incorporating the effect of an earthquake should be included in the coastal embankment or offshore breakwater design, especially for the area with active earthquakes. 相似文献
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An improved method of two-dimensional kinematical structural analysis of tides (the “method of the orbits”) is presented.
This method allows us to determine the parameters of the primary tidal waves shaping the observed tidal structure. The construction
of the vertical orbits for the individual tidal harmonics is performed along the horizontal coordinate axes; one of them is
oriented along the so-called “reactive azimuth,” which coincides with the direction of the tidal current at the instant of
the zero tidal level. In this case, the orbit parameters include information on the amplitude-phase relations of the interfering
waves and allow us to determine the angle of the waves crossing. The suggested method enables us to quantitatively describe
the mechanism of the tidal formation with oblique interference both close to the shore and in the open sea. We tested the
new method in two local zones of the White Sea (Morzhovets Island and in the vicinity of the entrance to Kandalaksha Gulf)
where the presence of rotating semidiurnal tidal currents evidences the significant role of oblique interference of tidal
waves. In these zones, the developed method made it possible to perform a detailed quantitative analysis of the local tide
structure caused by the M2 tidal wave, which plays the dominant role in the White Sea. The result describes the structure of the propagation of the
primary tidal waves better than the field of “pure” energy fluxes that was used earlier. 相似文献
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利用在南海东沙群岛北部至西北海域为工程目的所采集的海底地形测量、底质取样、海底底流测量资料,以及以往的区域地质、地球物理资料,采用沉积学、构造学和海洋水动力学综合研究方法,对该区海底沙波形成及稳定性进行了综合分析。认为该区海底沙波是在目前水动力环境下所形成,为今生,海底表层沉积物为晚更新世地层受到冲刷改造的再沉积。沙波形成主要受潮流底流的水动力作用控制,并与构造抬升有关。沙波具有一定的活动性,主要由SE向NW方向移动,且活动性逐渐减弱。北区段海底沙波稳定,中区段海底沙波较稳定,它们对海底工程建设不会造成影响;而南区段海底沙波较为活动,当沙波发生较大规模移动时,对海底工程建设会造成一定影响。 相似文献
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海蚀作用会诱发各种地质灾害,为研究青岛崂山地区的海蚀作用,本研究通过野外踏勘取样、岩石手标本鉴定和偏光显微镜下薄片鉴定分析等方法,分析了岩石学和构造特征对海蚀作用的影响,并以石老人地区为例分析了海蚀地貌的特征,探讨了崂山地区的海蚀地貌分布特征及影响因素。结果表明:崂山海岸基岩为I-A型复合花岗岩。抗海蚀能力最强的是白垩系莱阳群砂岩,其次为白垩系青山群火山岩和石英二长岩,再次为碱性花岗岩,黑云二长岩最弱。断裂构造破坏岩石稳定性,促进了海蚀作用;石老人地区以流纹岩为主,在海蚀崖后退过程中,安山岩的侵入体保留下来,形成了石老人海蚀柱;崂山地区发育多种海蚀地貌,受到海浪作用、气温条件、盐类结晶以及生物作用等外部因素影响。 相似文献
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《Marine Geology》2001,172(3-4):205-223
A mathematical wave erosional model was used to study the effect of high sea levels during the penultimate (oxygen isotopic stage 7) and last interglacials (substage 5e), and in the late Holocene (stage 1), on the present morphology of wave-cut shore platforms. Sea level was considered to have been either the same as today or 2.25 m lower during the penultimate interglacial, and 2.25, 4.5 or 6.75 m higher than today during the last interglacial stage. The model suggested that inherited, gently sloping shore platforms in resistant rocks may be essentially protected today from erosion by high storm waves. The lowest platform gradients were in runs with mesotidal (3 m) range, and usually with low wave periods, low surf attenuation rates and weak rocks. Modern platform gradients increased with the difference in elevation between sea levels during successive interglacial stages. Shore platforms were widest in runs in which sea level was the same as today in the penultimate interglacial and 4.5 m higher than today during the last interglacial. Constant sea level, and high, last interglacial sea levels with considerable overlapping between the zones of high duration values between the mean neap high and low tidal levels in stages 7, 5e and 1, were conducive to the development of wide shore platforms, whereas sea levels lower than today's in stage 7 tended to produce narrower platforms. In general, higher sea levels during the last interglacial tended to produce higher cliff–platform junctions than constant sea level, unless the sea was lower than today during the penultimate interglacial stage. There was a lack of supratidal ledges in macrotidal (9 m) model runs with high initial gradients; this suggests that gently sloping, inherited shore platforms are essential for the subsequent development of supratidal, nonstructural ledges in high tidal environments during periods of higher sea level. Intertidal ledges developed in the upper portion of the modern intertidal zone, under a variety of tidal and sea level conditions. These ledges can develop independently of lithological or structural influences, and without any change in sea level. A single high sea level may also simultaneously produce two ledges at different supratidal elevations in mesotidal environments. 相似文献
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Effect of Development of Caofeidian Harbor Area in Bohai Bay on Hydrodynamic Sediment Environment 总被引：7，自引：1，他引：6
Based on the characteristics of waves, tidal currents, sediment and seabed evolution in the Caofeidian sea area in the Bohai Bay, a 2D sediment mathematical model of waves and tidal currents is employed to study the development schemes of the harbor. Verification of spring and neap tidal currents and sediment in the winter and summer of 2006 shows that the calculated values of tidal stages as well as flow velocities, flow directions and sediment concentration of 15 synchronous vertical lines are in good agreement with the measured data. Also, deposition and erosion of the sea area in front of Caofeidian ore terminal induced by suspended load under tidal currents and waves are verified; it shows that the calculated values of depth of deposition and erosion as well as their distribution are close to the measured data. Furthermore, effects of reclamation scheme of island in front of the land behind Caofeidian harbor on the hydrodynamic environment are studied, including changes of flow velocities in the deep channels at the south side of Caofeidian foreland and Laolonggou and in various harbor basins, as well as changes of deposition and erosion of seabed induced by the project. 相似文献
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黄河三角洲孤东海域沉积物及水动力 总被引：7，自引：0，他引：7
根据黄河三角洲孤东近岸海域表层沉积物取样、水文泥沙观测和风浪资料推算,分析沉积物特征和运移趋势,并通过水动力条件(潮流和波浪)探讨沉积物起动和输移特征。结果表明,孤东海域沉积物多为粉砂类物质,由内向外逐渐变细,分选变差,丁坝的修建对周围粒径分布影响明显;沉积物运移趋势受风成余流、岸线轮廓和丁坝工程修建的影响,不同区域表现为不同的输移方向;研究区水动力表现为波浪掀沙、潮流输沙的特征,由于潮流较小,不足以引起泥沙的起动,泥沙起动主要由波浪引起。 相似文献
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Vast bay-type tidal inlets can be found along the coastal zones of China. They are generally suitable for deep water channels and large harbors because of the presence of large water depth and good mooring conditions. The deep channel, in front of the head of Caofeidian Island in Bohai Bay, China, is a typical bay-type tidal inlet system. The tidal current, a type of reverse flow, makes the key contribution to maintain the deep water depth. The co-action of waves and tidal currents is the main dynamic force for sediment motion. Waves have significant influence on the sediment concentration. Based on the characteristics of waves, tidal currents, sediment and seabed evolution in Caofeidian sea area, a 2D mathematical model for sediment transport under influence of waves and tidal currents is developed to study the development schemes of the Caofeidian Harbor. The model has been verified for spring and neap tides, in winter as well as in summer of 2006. The calculated tidal stages, flow velocities, flow directions and sediment concentrations at 15 stations are in good agreement with the observations. Furthermore, the calculated data on pattern and magnitude of sedimentation and erosion in the related area agree well with the observations. This model has been used to study the effects of the reclamation scheme for Caofeidian Harbor on the hydrodynamic environment, sediment transport and morphological changes. Attentions are paid to the project inducing changes of flow velocities and morphology in the deep channel at the south side of Caofeidian foreland, in the Laolonggou channel and in various harbor basins. The conclusions can provide the important foundation for the protection and use of bay-type tidal inlets and the development of harbor industry. 相似文献