共查询到18条相似文献，搜索用时 279 毫秒
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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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波浪作用下海底斜坡滑动稳定性分析中,一般未考虑海底坡度引起的波浪浅水效应,即不考虑波浪在斜坡面上的变形导致的波压力变化,降低了其计算结果的可靠性。本文基于沿斜坡面传播的线性波浪理论,考虑波浪的浅水效应,利用波浪与重力作用下海底斜坡的有效应力场,计算海底斜坡滑动稳定性安全系数。在验证海底斜坡滑动稳定性计算结果可靠性的基础上,分析了坡度对海底斜坡瞬态波浪响应及其滑动失稳特征的影响。结果表明,由于波浪沿斜坡面传播的浅水效应,相对于水平海床,波浪作用下斜坡最大瞬态应力和孔隙水压力随着坡度的增加基本呈线性增加趋势,最大水平位移呈非线性增加趋势;相比于坡底水平段海床的滑动区,斜坡面上滑动区的深度和水平方向滑动范围均有所增加,且坡度越大,这种效应越显著;相比于饱和海床,非饱和条件下,坡度对斜坡体滑动特征的影响程度有所降低。 相似文献
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波致海底缓倾角无限坡滑动稳定性计算分析探讨 总被引：1，自引：1，他引：0
波浪作用下海底无限坡滑动稳定性计算的极限平衡法中,忽略了坡体水平向应力状态的影响,为此,针对波浪作用下海底缓倾角无限边坡的特点,提出直接基于滑动面处土体应力状态的滑动稳定性计算方法(简称应力状态法),并分析了其适用范围。对具体算例的分析表明,应力状态法计算得出的安全系数大于极限平衡法的安全系数,且随着滑动面深度的增加、土体泊松比以及边坡坡角的增大,两种计算方法得出的安全系数的差异会逐渐增大;对于波浪作用下的海底缓倾角无限边坡,在失稳时极可能沿具有一定厚度的滑动带而不是单一的滑动面而滑动,且波致最大剪应力所在的深度,常常不是斜坡体最易失稳滑移的深度。 相似文献
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岙山成品油码头海底边坡稳定性分析 总被引：1，自引：0，他引：1
根据岙山成品油码头工程地质勘察所得的资料,选择边坡较陡的地段,采用折线法、圆弧条分法和总应力极限平衡法,对在自重、地震力和波浪力等因素作用下的边坡稳定性进行验算分析。结果表明,海底边坡较陡地段浅层土体的稳定性较差,土体滑动面可能发生在海底下９～１２．５ｍ处。对地层的作用波浪力较地震力要小,但两者均可能成为边坡土体滑动的诱因。 相似文献
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海底斜坡稳定性受风暴潮、海底地震等诸多不确定因素影响,易发生失稳破坏,产生较大的海洋地质灾害。简要介绍海底斜坡稳定性分析方法,建立曹妃甸深槽典型斜坡计算模型,确定了模型计算的海底地形参数、地层结构参数、土体物理力学参数等指标,利用GEO-SLOPE斜坡分析软件进行海底斜坡稳定性定量计算,分析了工程建设前自然状态下以及在大规模工程建设后海底斜坡稳定性,并模拟分析了在大风浪和地震等极端条件下斜坡的稳定性,确定了海底斜坡失稳空间特征。首次采用数值计算对曹妃甸海底斜坡稳定性进行定量分析评价,可以为类似近海建设工程提供重要的参考作用。 相似文献
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对MADE KYUN河三角洲海底斜坡所在区域地形地貌、地层岩性等进行阐述分析,结合调查资料确定了斜坡坡体组成与特征:该斜坡坡体主要为淤泥、淤泥质黏土,厚度6~9m。基于GEO-SLOPE软件的SLOPE/W模块计算斜坡稳定性安全系数并确定最危险滑动面,利用BING软件的Herschel-Bulkley模型、双线型模型对最危险滑动面的滑移距离进行模拟预测。数值分析结果表明:在考虑孔隙水压力的情况下,4种计算方法得到的稳定性系数均有所下降,M-P法计算得到的斜坡稳定性安全系数为0.606,处于不稳定状态;2种模型计算得到的滑移距离分别为207和213m,峰值滑移速率分别为7.80和9.33m/s,会对较大范围的海底管道等海底设施造成破坏性影响。 相似文献
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以 Iversion的海底稳定渗流理论为基础 ,运用静力极限平衡方法和库仑破坏准则 ,提出了以海底水下斜坡坡度、沉积物有效内摩擦角和内聚力为自变量 ,波浪在海底产生的孔压梯度为参变量的海底稳定性分析方法。并给出了黄河水下三角洲不同土质所需的临界孔压梯度判断曲线 ,预测了黄河水下三角洲的海底稳定性 ,其分析结果与实测资料吻合良好 相似文献
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砂土中带裙板防沉板基础竖向承载力的上限解 总被引：1，自引：1，他引：0
防沉板是深海油气工程中水下生产系统的重要基础形式,因其埋深浅、水下施工方便等特点而具有广阔的应用前景。为了满足基础抗滑移的要求,可在防沉板底部设置裙板,裙板的存在增加了防沉板竖向承载力计算的难度。将防沉板基础简化为带裙板条形基础,考虑了内部土体与基础的相互作用,建立了竖向承载模式,即Terzaghi模式;运用极限分析法推导了该承载模式的上限解,引入了一个能够反映裙板与基础内部土体共同作用的经验参数—土体破坏率(η),其大小决定了地基中土体滑动面的范围;通过分析确定了在二维简化条件下带裙板防沉板基础的土体破坏率与基础高宽比的关系;并研究了土体破坏率不同时,地基承载力系数Nq和Nγ与土体内摩擦角之间的关系。 相似文献
11.
Gang Wang Guohai Dong Marc Perlin Xiaozhou Ma Yuxiang Ma 《Ocean Engineering》2011,38(17-18):2151-2161
A numerical model, which can simulate wave generation and propagation is developed to simulate oscillations induced by seafloor movements inside a harbor of constant slope, and once verified and then validated through comparison with experimental results, the numerical results are used to examine the analytic solutions presented in Wang et al. (Wang, G., Dong, G., Perlin, M., Ma, X., Ma, Y., 2011. An analytic investigation of oscillations within a harbor of constant slope. Ocean Engineering 38, 479–486). Small-scale seafloor movement usually induces small longitudinal oscillations, but evident larger transverse oscillations. These transverse oscillations are sensitive to the location of the moveable seafloor. The numerical result of each transverse eigen frequency compares well with the theoretical solution; in addition the spatial structure of each mode is also well-captured by the theory. Furthermore, evident/larger longitudinal oscillations induced by large-scale seafloor movements are simulated, and the numerical resonant frequencies agree favorably with the analytical solutions. These longitudinal oscillations are sensitive to the horizontal location of the moveable seafloor. 相似文献
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Study on Failure Mechanism and Bearing Capacity of Three-Dimensional Rectangular Footing Subjected to Combined Loading 总被引：2，自引：0，他引：2
This paper presents two kinematic failure mechanisms of threc-dimensional rectangular footing resting on homogeneous undrained clay foundation under uniaxial vertical loading and uniaxial moment loading. The failure mechanism under vertical loading comprises a plane strain Prandti-type mechanism over the central part of the longer side, and the size of the mechanism gradually reduces at the ends of the longer side and over the shorter side as the corner of rectangular footing is being approached where the direction of soil motion remains normal to each corresponding side respectively. The failure mechanism under moment loading comprises a plane strain scoop sliding mechanism over the central part of the longer side, and the radius of scoop sliding mechanism increases linearly at the ends of the longer side. On the basis of the kinematic failure mechanisms mentioned above, the vertical ultimate bearing capacity and the ultimate bearing capacity against moment or moment ultimate bearing capacity are obtained by use of upper bound limit analysis theory. At the same time, numerical analysis results, Skempton＇ s results and Salgado et al. ＇s results are compared with this upper bound solution. It shows that the presented failure mechanisms and plastic limit analysis predictions are validated. In order to investigate the behaviors of undrained clay foundation beneath the rectangular footing subjected to the combined loadings, numerical analysis is adopted by virtue of the general-purpose FEM software ABAQUS, where the clay is assumed to obey the Mohr-Coulomb yielding criterion. The failure envelope and the ultimate bearing capacity are achieved by the numerical analysis results with the varying aspect ratios from length L to breadth B of the rectangular footing. The failure mechanisms of rectangular footing which are subjected to the combined vertical loading V and horizontal loading H （Vertical loading V and moment loading M, and horizontal loading H and moment loading M respectively are observed in the finite e 相似文献
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De-feng Zheng Bo Liu Min Liu Ping Yin Yan-dong Huo 《Marine Georesources & Geotechnology》2019,37(1):116-127
The exploration and exploitation of marine georesources ordinarily disturbs the submarine soft clay surrounding construction areas and leads to a significant decrease in the shear strength of structured and sensitive clayey soils in submarine slopes. Under wave action, local slides can even trigger large-scale submarine landslides, which pose a serious threat to offshore infrastructure such as pipelines and footings. Therefore, accurately evaluating the stability of submarine sensitive clay slopes under wave-induced pressure is one of the core issues of marine geotechnical engineering. In this paper, a kinematic approach of limit analysis combined with strength reduction technique is presented to accurately evaluate the real-time stability of submarine sensitive clay slopes based on the log-spiral failure mechanism, where external work rates produced by wave-induced pressure on slopes are obtained by the numerical integration technique and then are applied to the work-energy balance equations. The mathematical optimization method is employed to achieve the safety factors and the critical sliding surfaces of submarine slopes at different time in a wave cycle. On this basis, the stability of submarine sensitive clay slopes under various wave parameters is systematically investigated. In particular, extreme wave conditions and special cases of slope lengths no more than one wavelength are also discussed. The results indicate that waves have some negative effects on the stability of submarine sensitive clay slopes. 相似文献
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Fei Xu Shu-Cai Li Li-Ping Li Qian Zhang Kang Wang 《Marine Georesources & Geotechnology》2016,34(2):181-187
Based on Power-Law nonlinear failure criterion and the upper bound theorem of limit analysis, a numerical solution was developed to analyze the shape of collapsing block and landslide thrust of cofferdam subjected to residual pore pressure which was caused by longstanding water wave action. In the upper bound analysis, the effect of water pressure assumed to be a work rate of external force was considered. To evaluate the validity of the present method, the results were compared with previous findings. The good agreement between the present results and the previous findings indicated that the proposed method was valid to assess the shape of collapsing block and landslide thrust of cofferdam subjected to residual pore pressure. As for the influence of the factors on the shape of collapsing block and landslide thrust, a parametric study was conducted. This parametric study was carried out to optimize the design of cofferdam supporting structures and improve analysis of the stability of cofferdam subjected to water wave action. 相似文献
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Abstract The use of marine high‐resolution geophysical profiling data, seafloor soil samples, and accepted land‐based methods of analysis have provided a means of assessing the regional geotechnical conditions and relative slope stability of the portion of the Gulf of Alaska Continental Margin known as the Kodiak Shelf. Eight distinct types of soils were recognized in the study; the seafloor distribution of these indicates a complex geotechnical setting. Each soil unit was interpreted as having a distinct suite of geotechnical properties and potential foundation engineering problems. Seven categories of relative slope stability were defined and mapped. These categories range from “highest stability”; to “lowest stability,”; and are based on the degree of slope of the seafloor, type of soil underlying the slope, and evidence of mass movement. The results of the analysis indicate that the highest potential for soil failure exists on (1) the slopes forming boundaries between the submarine banks and the broad sea valleys, and (2) the upper portion of the continental slope, where evidence of past slope failure is common. Also of concern are gently sloping areas near the edges of submarine banks where evidence of possible tension cracks and slow downhill creep was found. 相似文献
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Abstract Potential sediment mass movement was analyzed at ten locations on the continental slope off Peru and northern Chile, using samples obtained from up to 3 m below the seafloor. Shear strength parameters were obtained from consolidated‐undrained triaxial compression tests. Sediment behavior in these tests reflects the influence of organic matter, which is concentrated in the slope deposits by coastal upwelling. High water content of the organic‐rich sediments and the high de‐formability of organic matter contribute to the prevalent ductile behavior. Aggregation of clays by organic matter is apparently responsible for the high friction angles, up to 44°, displayed by the slope deposits. Sediment stability was assessed using infinite slope analyses. These analyses indicate that gravitational forces alone are not sufficient to cause sediment failure at any of the slope locations. Sediment accumulation on the slope is not rapid enough to generate excess pore pressure and reduce the resistance to gravitational sliding. Effects of earthquakes on slope stability were evaluated by modeling earthquake‐induced inertia forces as static forces and estimating pore pressures developed during cyclic loading. This analysis shows that sediments of the lower slope off Peru possess the highest susceptibility to failure during earthquakes. Earthquake accelerations on the order of 0.2 gravity are sufficient to trigger slumping at all ten slope locations. Indirect evidence suggests that creep and mass flows initiated at shallower water depths are factors that might contribute to sediment failure on the slope. 相似文献
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波浪作用下海床动力反应的数值分析 总被引：2，自引：3，他引：2
近海和离岸建筑物的基通常处于连续不断的小风浪作用之下，可将其变形视为弹性。基于二维广义Biot理论，提出了线性或非线性波浪作用下饱和弹性海床动力应应的时域有限元数值解法。静力平衡条件和Biot方程组成的边值方程可视为其特例，在比较算例中，数值计算得到的孔压和有效应力幅值沿海床深度的分布与解析解十分吻合。土骨架和孔隙流体的加速度对海床动力反应的影响很小。具体算例表明，线性波沿缓坡海床传播时，土层中超静孔压和有效应力幅值随之增大，有可能发生滑动坡坏。所提出的数值解法能够灵活地处理非线性波浪荷载，海底复杂地质条件和波浪沿缓坡传播等复杂情况。 相似文献
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The stabilization of slopes by placing piles is one of the most innovative and effective slope reinforcement techniques in the coastal engineering in recent years. Due to the simplicity and efficiency, limit analysis method is the most common approach for assessing the stability of slopes. However, the majority of existing limit analysis methods is limited to slope without the presence of piles. In this technical note, a novel upper-bound limit analysis method was proposed to access the stability of three-dimensional slopes reinforced with piles incorporating the admissible rotational failure mechanism where toe failure, face failure, and base failure were taken into account. The effects of key designing parameters, e.g., pile location, pile spacing, slope angle, slope width on the stability of earth slopes, and geometry of critical slip surface were presented and discussed. The results demonstrate that the proposed approach is more appropriate for assessing the stability of slopes reinforced with piles and can be also utilized in the design of piles stabilizing the unstable slopes. 相似文献