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1.
Pseudo-Static Elasto-Plastic Cyclic Creep Model and Cyclic Stability of Offshore Soft Foundation 总被引：2，自引：0，他引：2
The accumulative shear deformation of soft clays under cyclic loads is considered as pseudo-staticcreep.A pseudo-static elasto-plastic cyclic creep model is developed based on the visco-elasto-plastic theory.Theparameters in the model are determined by cyclic triaxial soil tests.A method for analyzing the stability of offshoresoft foundation under wave loads is given by combining the model with pseudo-static creep analysis.An exampleis analyzed by the method.The results show that the horizontal and vertical stability of foundations under waveloads can be analyzed by it and the analytical results are qualitatively consistent with the observed failure modes ofshallow foundations. 相似文献
2.
Mohammad M. Eslami 《Marine Georesources & Geotechnology》2018,36(3):331-339
Concrete seawalls are structures in coastal facilities for shore and slope protections. Owing to several advantages of sloped or inclined walls such as minimum soil disturbance and less required earthworks, they can be considered as an appropriate alternative to vertical cantilever retaining walls. The combination of slab and strip semideep foundation instead of heel–toe slab foundations increases their capability for stability, erosion control, and storm wave energy dissipation. In this paper, three case studies from seawalls in which failure has occurred are presented and discussed. Technical performance of sloped walls against different internal and external instability factors is investigated, and comparisons are made between vertical and sloped (inclined) walls with respect to geotechnical and structural aspects through parametric study. Analysis indicates that the sloped retaining walls perform better from technical, practical, and economical standpoints. It was found that for identical static and dynamic loads, including earthquake and wave loads, inclined walls provide relatively higher safety factors against different criteria and exhibit more stable and practical performance compared with commonly used walls in practice. The case studies in this paper illustrate causes of failure in each case and gives suggestions for improving instability prevention of walls against static and dynamic loads. 相似文献
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4.
Structural Types of Sea Embankment and Their Stability Analysis 总被引：1，自引：0，他引：1
MAO Changxi DUAN Xiangbao MAO Peiyu Prof. Senior Engineer Hydraulic Engineering Department Nanjing Hydraulic Research Institute 《中国海洋工程》1998,(3)
In this paper based on investigation on the structural types of sea embankments in thesoutheast coastal area of China,as well as the related tidal stages,waves and strength of marine soils,thefinite element method(FEM)calculations for seepage flow stability,including the overall stability againstsliding and local stability of sloping surface under the action of tidal stage and waves are carried out.Acomparison of the computational results of FEM for single circular slip,composite circular slip andgeogrid reinforcement against sliding shows that for calculation of stability against sliding of marine softsoil foundation it is even more reasonable to use the composite circular slip.The stability of sloping typesea embankment against sliding is slightly better than that of the vertical face type;for the combination ofthree defences(wave,scour and seepage defences)the sea embankment structural type of a compositecross section with a platform should be a good one,but it still should be suitable to local condit 相似文献
5.
Babloo Chaudhary Hemanta Hazarika Siavash Manafi Khajeh Pasha 《Marine Georesources & Geotechnology》2018,36(3):308-322
Coastal protective structures, such as composite breakwaters, are generally vulnerable to earthquake. It was observed that breakwaters damage mainly due to failure of their foundations. However, the seismically induced failure process of breakwater foundation has not been well understood. This study describes failure mechanism of breakwater foundation as well as a newly developed reinforcing model for breakwater foundation that can render resiliency to breakwater against earthquake-related disasters. Steel sheet piles and gabions were used as reinforcing materials for foundation. The experimental program consisted of a series of shaking table tests for conventional and reinforced foundation of breakwater. Numerical analyses were conducted using finite difference method, and it was observed that the numerical models were capable to elucidate the seismic behavior of soil–reinforcement–breakwater system. This paper presents an overview of the results of experimental and numerical studies of the seismic response of breakwater foundation. Overall, the results of these studies show the effectiveness of the reinforced foundation in mitigating the earthquake-induced damage to the breakwater. Moreover, numerical simulation was used for parametric study to determine the effect of different embedment depths of sheet piles on the performance of breakwater foundation subjected to seismic loading. 相似文献
6.
A stability analysis of reinforced foundation soil is presented in this paper. A method based on the discrete element method (DEM) is suggested for calculating the bearing capacity on strip footings over multilayer soils reinforced with a horizontal layer of geosynthetics. The proposed method can estimate the ultimate bearing capacity and the distribution of tensile force developed in the geosynthetics of the footing system by Winkler springs to account for the compatibility between soil blocks and tensile elements to consider the tensile behavior between soil and geosynthetics. For footings on various multilayer soils with or without reinforcement of geosynthetics, the results of the method were compared to the field test results as well as to those obtained by various methods proposed by other researchers. 相似文献
7.
为了研究海底防沉板—桩复合基础在地震荷载作用下的动力反应特性,以我国南海深水工程实例为研究对象,利用Flac3D有限差分仿真软件建立了计算模型,土体采用Mohr-Coulomb本构模型,模型底部输入EL Centro地震波,对不同桩长的复合基础进行分析计算.在该特定工程背景下,研究结果表明:随着桩长的增加,防沉板顶部加速度放大系数呈减小趋势;地震荷载下,复合基础发生震陷,沉降量在地震波加速度峰值过后趋于稳定;当桩长为6m时,复合基础的水平振动程度和震陷量最小;由于桩基础把震动能量传输到深部土层中,复合基础周围土体的加速度响应值小于远场土体.在动力时域内,防沉板与桩连接处弯矩最大,需要在此处增设加固装置. 相似文献
8.
ABSTRACTThe suction caisson is commonly a top-closed cylindrical steel structure with large diameter, short length and much thinner skirt wall thickness. The resistance to penetrating is calculated as the sum of the tip bearing capacity and the adhesion on the both sides of the skirt wall. Since the thickness of the skirt wall is very small, the downward adhesion produced by the skirt wall will cause the additional vertical stress and shear stress in the soil at the skirt tip level, increasing the skirt tip resistance. However, the increase in skirt tip resistance caused by the additional vertical stress rather than shear stress in soil at the skirt tip level was only considered, this may lead to an inaccurate estimation for the tip bearing capacity and the suction required. Thus, a modified slip-line field is put forward in this study to estimate the tip resistance. The expression of obtaining the minimum suction to install the suction caisson in clay is derived in terms of the force equilibrium. Results from calculations of the minimum suction have been proved to be in a good agreement with the measured data. 相似文献
9.
《海洋技术学报》2024,(1)
海上高桩承台基础结构承台部分的设计主要依靠高桩码头和桥梁等其他高桩承台结构的经验，基于在建工程，为解决设计时容易设计出过厚承台和多余配筋的问题，本文采用有限元对包括土体在内的整个风机基础进行精细化数值模拟计算，计算结果与规范算法进行对比，得到承台设计时规范算法的安全余量，同时提出配筋优化方向。结果表明：基于弹性材料模型计算结果，有限元计算结果小于规范算法计算结果，基桩最大压力相差22.43%，最大上拔力相差2.08%，弯矩差别最大为57.89%，最小为18.85%；基于弹塑性材料模型计算结果，钢筋最大应力出现在钢管桩桩头，承台顶层钢筋受力较小，设计时可加强钢管桩桩头配筋，减少承台顶层钢筋数量。 相似文献
10.
Yogendra Tandel Mohsin Jamal Chandresh Solanki Atul Desai Jignesh Patel 《Marine Georesources & Geotechnology》2017,35(4):504-511
Granular piles are frequently used as a method of improving soft grounds as they provide increased bearing capacity and reduce foundation settlements. However, in very soft clayey soils, they may not derive their load-carrying capacity by low confining pressure provided by the surrounding soil. In such circumstances, granular piles may be reinforced with suitable geosynthetic to increase its load-carrying capacity and to reduce excessive bulging. In this study, the performance of small group of geosynthetic-reinforced granular piles (GRGPs) is examined in terms of load-carrying capacity, settlement, and modulus by laboratory model tests. The parameters investigated include modulus of reinforcement material, area replacement ratio (ARR) based on the column diameter and reinforcement length. The results indicated that increasing the modulus of the reinforcement and the ARR based on the column diameter enhances the overall performance of the GRGP group. It was also observed that reinforcement on top portion of the granular pile is sufficient to substantially increase the load-carrying capacity of granular pile group. 相似文献
11.
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
12.
Babloo Chaudhary Hemanta Hazarika Akira Murakami Kazunori Fujisawa 《Marine Georesources & Geotechnology》2018,36(7):827-840
A strong earthquake often precedes a tsunami, and a breakwater may settle during the earthquake. Such seismic subsidence of the breakwater may reduce its ability to block the tsunami, and the tsunami may easily enter coastal areas by overflowing it. This study deals with the instability of a breakwater due to an earthquake. In addition, to protect a breakwater from damage caused by an earthquake, a new concept of using geogrid for reinforcing the foundation of a breakwater is introduced. To determine the behavior of unreinforced foundation and to evaluate the effectiveness of the proposed reinforced foundation under different earthquake loadings, a series of shaking table tests were performed. It was observed that the earthquake generated excess pore water pressures and deformations of foundation ground were main reasons of failure of the breakwater. The reinforced foundation was found effective to reduce the earthquake-induced damage of the breakwater, and finally it makes the breakwater resilient against earthquake-induced forces. Numerical simulations were also performed to elucidate the mechanism of reinforcement–breakwater–soil–water system under different earthquake loadings. 相似文献
13.
The in-situ application of micropiles has gradually increased in limited spaces of downtown areas because the micropile has various advantages, such as low vibration and noise and compact machine size. In this study, model tests were carried out to understand the reinforcement effect induced by the mechanical interaction between the micropile and soil. The micropiles were installed in the soil adjacent to footings. Factors such as reinforced range (W) with piles, spacing (S) between piles, the installed angle (θ) of piles, and pile length (L) were considered variables in the tests. The reinforced angle (θ) was a more critical factor than the others for restraining the settlement and increasing soil stiffness in the model test results. The reinforcement effect rapidly increased around the reinforced range (W) of 2B (B: the width of a footing), the reinforced angle (θ) of 45 ～ 75°, and the pile length (L) of 3B. Based on the results of the experimental analyses, the purpose of this study is to improve the reinforcement efficiency of micropiles by recommending the most effective pattern and design method for installing them. 相似文献
14.
《Applied Ocean Research》2007,29(1-2):37-44
The paper pertains to a study of analysing a waterfront retaining wall under the combined action of tsunami and earthquake forces. The stability of the waterfront retaining wall is assessed in terms of its sliding and overturning modes of failure. Pseudo-static approach has been used for the calculation of the passive seismic earth pressure. Hydrodynamic pressure generated behind the backfill due to shaking of the wet backfill soil is considered in the analysis. Tsunami force is considered to be an additional force acting on the upstream face of the wall and is calculated using a simple formula. It is observed that the factor of safety in sliding mode of failure decreases by about 70% when the ratio of tsunami water height to initial water height is changed from 0.375 to 1.125. Variations of different parameters involved in the analysis suggest sensitiveness of the factor of safety against both the sliding and overturning modes of failure of the wall and provides a better guideline for design. 相似文献
15.
An analytical expression of a gravity retaining wall's seismic stability against sliding and overturning is proposed in this article. The derivation, aiming at the cohesionless soil with inclined backfill surface and nonvertical wall back, is based on limit equilibrium analysis and the pseudo-dynamic method. The variations of the sliding and overturning stability safe factors with the horizontal seismic acceleration are investigated for different seismic amplification factors, soil friction angles, wall friction angles, vertical seismic acceleration coefficients, wall back inclination angles, and backfill surface inclination angles. The results indicate that the soil friction and horizontal seismic action significantly impact the seismic stability. The increase of vertical earthquake action changes the curvature of stability factor curves. The wall friction and back inclination strengthen the gravity retaining wall's resistance to sliding and overturning failure while the backfill surface inclination plays a negative role in the seismic stability. We also found that the seismic stability safe factors calculated by the proposed method are larger but more reasonable than those by the Mononobe-Okabe method. 相似文献
16.
1 .ＩｎｔｒｏｄｕｃｔｉｏｎＴｈｅｐｅｎｅｔｒａｔｉｎｇｂｕｃｋｅｔａｎｄｂｏｘｆｏｕｎｄａｔｉｏｎｉｓａｎｅｗｔｙｐｅｏｆｓｔｒｕｃｔｕｒｅ ,ｗｈｉｃｈｈａｓｂｅｅｎａｐｐｌｉｅｄｉｎｍａｎｙｅｎｇｉｎｅｅｒｉｎｇｆｉｅｌｄｓ .Ｉｎｖｉｅｗｏｆｔｈｅｈｉｇｈｃｏｎｓｔｒｕｃｔｉｏｎｃｏｓｔａｎｄｔｈｅｆｏｒｍｉｄａｂｌｅｃｏｎｓｔｒｕｃｔｉｂｉｌｉｔｙｏｆｏｆｆ ｓｈｏｒｅｐｌａｔｆｏｒｍｓｗｉｔｈｐｉｌｅｄｆｏｕｎｄａｔｉｏｎｓ ,Ｂａｅｒｈｅｉｍｅｔａｌ.(1 990 )ｐｒｏｐｏｓｅｄｔｈｅｃｏｎｃ… 相似文献
17.
This paper presents a three dimensional limit method based on the upper bound theory for the stability of suction bucket foundations of offshore platforms. The bucket embedded in soil is subjected to a lateral load applied above the mud line. In order to simulate the lateral load, a fictitious soil layer is assumed, having a thickness equals to the vertical distance from the load point to the surface of the foundation. The unit weight and shear strength of the fictitious soil are set to be zero. The soil–bucket failure mechanism is approximated by a series of prisms. The three dimensional limit method starts from establishing a compatible velocity field and obtains the factor of safety by the energy and work balance equation. Optimization is followed to approach the critical failure mechanism that offers the minimum factor of safety. Two different basal surfaces are incorporated, i.e. an arbitrarily defined failure surface and a partly elliptical failure surface. Results of centrifuge modeling of bucket foundations are used to verify the method. The arbitrary failure surface provides more reasonable prediction than the partly elliptical failure surface. Being a multi-variable dependent problem, further investigation is needed to search for the critical failure mechanism. 相似文献
18.
《海洋技术学报》2024,(1)
为提高基础利用率增加海上风电设施的可行性，对楔形单桩基础竖向承载力特性进行研究分析。采用PLAXIS 3D 有限元软件建立楔形单桩基础模型，从桩侧摩阻力、桩侧法应力及土体位移对比分析楔形单桩基础与等截面单桩竖向承载特性差异，并探讨内摩擦角、楔角及楔高对承载力的影响。研究表明：楔形单桩基础竖向承载力高于等截面单桩基础，且承载力随着楔角、楔高的增大而增大，提高率最大达24.786%。倾斜侧壁的引入改变了桩侧摩阻力的传递规律；倾斜侧壁挤密桩周土体，桩侧摩阻力与法向应力增大，从而有效提高单桩基础的竖向承载力。研究成果可为今后海上风电单桩基础截面型式的设计提供参考。 相似文献
19.
The reliability and/or stability of the lifeline structures against failure under seismic loads are of critical concern, and must be studied carefully. Therefore, the main objective of this paper is to demonstrate the commonly encountered backfill effects on the dynamic response of rectangular tanks. However, only the exterior wall of the tank which interacts with both the backfill and fluid is tackled, as each part of the structure shows considerable differences in terms of both the load bearing mechanisms and the geometrical and positional differences. Finite element analyses are employed, taking into consideration the fluid-wall-backfill interaction. The analyses are conducted to observe whether or not both backfill and wall behavior can be affected by variation of the internal friction angle. For that purpose, some comparisons are made on vertical displacements of the backfill, roof displacements, stress responses, etc., by means of internal friction angle variations of the backfill from 25° to 40°. Consequently, it is observed that the variations on maximum vertical displacements are affected considerably. In contrast, the maximum stress responses are affected partially. However, the inertial effects of the backfill show that pseudo-static approximations may be insufficient to understand the dynamic behavior of the backfill-wall-fluid system. 相似文献
20.
1 .IntroductionIt has beenrealizedthat constructing gravitystructures onsoft soil foundations is a difficult task,especiallyinthe marine area where boththe geological and environmental conditions are severe .Thisisnot only because the bearing capacity of the soft foundation is relatively low, but also because thestrength of the soft soil will befurther weakened bythe waveloading (Andersenet al .,1988 ;Ander-sen and Lauritzsen,1988 ; Yasuhara ,1988) .The strength weakening may cause serious d… 相似文献