共查询到20条相似文献，搜索用时 125 毫秒
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地震作用对琼州海峡海缆路由区海底稳定性影向的分析 总被引：1，自引：0，他引：1
以琼州海峡的北海—临高段海缆路由为例,利用计算对比的方法,分析了地震作用下,路由区3m以浅海底土液化或滑移的可能性,评价了路由区海底的稳定性。结果发现,在地震烈度为Ⅶ度的地震作用下,砂性土海底的地震剪应力平均值(0.86kPa,1.72kPa和2.57kPa)小于砂性土的液化剪应力(1.60kPa,3.20kPa和4.81kPa);粘性土海底的地震剪应力平均值(1.25kPa,2.49kPa和3.74kPa)小于粘性土的抗滑剪应力平均值(4.07kPa,4.61kPa和4.49kPa),路由区海底稳定性良好;在地震烈度为Ⅷ度的地震作用下,砂性土海底的地震剪应力平均值(1.73kPa,3.45kPa和5.12kPa)大于砂性土的液化剪应力;粘性土海底的地震剪应力平均值(2.49kPa,4.98kPa和7.47kPa)除表层外,大于粘性土的抗滑剪应力,路由区海底会发生失稳破坏。 相似文献
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南海珠江口盆地贝壳砂土力学性质初步研究 总被引：1，自引：0，他引：1
通过对珠江口盆地广布的贝壳砂的化学组分、粒度组分、形成时代的研究以及对砂土进行直剪试验、主高压结试验、常规三轴剪切试验和动三轴试验，对贝壳砂的土力学性质及动载荷作用下的稳定性作了初步分析，获取了贝壳砂的基本物理力学参数并评价了地震作用下砂土液化的可能性，为海洋工程的设计和施工提供了基本的物理力学参数。 相似文献
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曹妃甸围海造陆区吹填了高厚度的粉细砂,粉细砂在地震荷载作用下可能发生液化,威胁吹填区码头和堆载场地的稳定性。采用等体积循环单剪试验,研究了吹填粉细砂在循环荷载作用下的强度和等效超静孔压发展。随着荷载循环次数的增加,粉细砂中超静孔压的发展呈现"快-慢-快"趋势。当累积孔压达到初始固结应力的80%时,超静孔压快速增加,土体达到破坏,液化的发生具有突发性。根据单调和循环单剪试验数据,提出了曹妃甸吹填粉细砂动强度的归一化表达式。结合场地液化评估简化方法,对曹妃甸场地进行了液化判别:在7级地震作用下,中密粉细砂场地的液化深度能达到10 m。 相似文献
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琼州海峡跨海工程新Ⅶ线区地质条件及地质灾害因素评价 总被引：6，自引：2，他引：6
通过对琼州海峡跨海工程(固定式)新Ⅶ线调查区浅层地质一地球物理特征的研究，揭示了研究区的地形地貌特征及地质条件，并对区内主要地质灾害因素进行了评价研究，认为新Ⅶ线区内海底表面无障碍物，区内也无任何断层，目前在潮流的作用下仍在移动的沙波和沙垄是其主要的潜在地质灾害因素，而斜坡稳定性和砂土震动液化(海底以下20m范围内砂土层)在120年一遇的极端波浪荷栽作用下或在地震基本烈度为Ⅶ度的情况下均不会构成该跨海工程的潜在地质灾害因素。同时还指出，虽然区内地质条件均属于不具活动能力的限制性地质条件，但其对工程设施仍具有不可忽视的潜在危险性，应给予足够重视。 相似文献
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现代黄河水下三角洲砂土液化模式 总被引：1，自引：1，他引：1
根据实际勘探资料及室内土工试验结果，按极限平衡理论和线性波动理论等，分析了现代黄河水下三角洲砂土在地震和波浪动力因素的作用下发生液化的可能性，并根据其液化过程实质是孔隙水压力产生、发展和消散的过程，总结出砂土液化模式应包括四个阶段；（１）压密阶段：孔隙水压力升高至砂土本身强度，使颗粒产生相对位移；（２）初始液化阶段：孔隙水压力升至土层所受侧向压力，产生较大应变；（３）完全液化阶段：孔隙水压力升至土层上覆有效应力，产生喷水冒沙现象；（４）塌陷形成阶段：孔隙水压力消散。 相似文献
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For South Korea, liquefaction potential along the western coast has not been widely assessed because South Korea is considered to be a low seismic hazard. However, recent earthquake events and historical records indicate that the seismic hazard of South Korea should not be ignored. Moreover, as artificial fills are extensively used along the western coast for development, liquefaction evaluation of the soils in this area is necessary. In this paper, we present: (1) the seismic characteristics of the study area; (2) procedures for evaluating liquefaction potential, focusing on the liquefaction potential index (LPI) approach; and (3) LPI distributions at several representative locations along the western coast of South Korea under various seismic scenarios. The liquefaction potential index represents the liquefaction potential over the upper 20 m of a boring or sounding. Using cone penetration test (CPT) and standard penetration test (SPT) data from two coastal sites, we compare and discuss CPT-based and SPT-based LPI values, particularly values computed in nonplastic, silt-rich soils. In these soils, it appears that the CPT yields lower liquefaction resistance, resulting in large LPI values. Finally, discussion and suggestions are provided for CPT- and SPT-based liquefaction assessment of low plasticity and high fines content soils. 相似文献
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海床式静力触探设备工作效率高,能够实现从垂向上对地层的连续探测,数据分辨率较好。通过对黄河口海域3个静力触探孔和1个地质钻孔的分析,将研究区20m以浅地层自上而下划分为粉土、粉质黏土、粉土夹粉砂或粉砂、粉质黏土、粉土五层,静力触探曲线对粉土层中的硬壳层和粉质黏土层中的贝壳夹层等特殊地质现象有很好的反映。对粉质黏土的静力触探参数与物理力学参数进行相关性分析,得到适合该区域的回归方程。采用基于CPT数据的液化判别法,对研究区表层粉土液化可能性进行评判,通过Seed简化法计算的周期应力比(CSR)与Olsen法计算的周期阻力比(CRR)的大小比较,得出当抗震设防烈度为7度时,研究区表层粉土不会液化,当抗震设防烈度为8度时,粉土层将发生液化,计算最大液化深度3.7m。 相似文献
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Simplified techniques based on in situ testing methods are commonly used to predict liquefaction potential. Many of these simplified methods are based on finding the liquefaction boundary separating two categories (the occurrence or non-occurrence of liquefaction) through the analysis of liquefaction case histories. As the liquefaction classification problem is highly nonlinear in nature, it is difficult to develop a comprehensive model taking into account all the independent variables, such as the seismic and soil properties, using conventional modeling techniques. Hence, in many of the conventional methods that have been proposed, simplified assumptions have been made. In this study, an updated support vector machine (SVM) based on particle swarm optimization (PSO) is used to evaluate liquefaction potential in two separate case studies. One case is based on standard penetration test (SPT) data and the other is based on cone penetration test (CPT) data. The SVM model effectively explores the relationship between the independent and dependent variables without any assumptions about the relationship between the various variables. This study serves to demonstrate that the SVM can “discover” the intrinsic relationship between the seismic and soil parameters and the liquefaction potential. Comparisons indicate that the SVM models perform far better than the conventional methods in predicting the occurrence or non-occurrence of liquefaction. 相似文献
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Simplified techniques based on in situ testing methods are commonly used to predict liquefaction potential. Many of these simplified methods are based on finding the liquefaction boundary separating two categories (the occurrence or non-occurrence of liquefaction) through the analysis of liquefaction case histories. As the liquefaction classification problem is highly nonlinear in nature, it is difficult to develop a comprehensive model taking into account all the independent variables, such as the seismic and soil properties, using conventional modeling techniques. Hence, in many of the conventional methods that have been proposed, simplified assumptions have been made. In this study, an updated support vector machine (SVM) based on particle swarm optimization (PSO) is used to evaluate liquefaction potential in two separate case studies. One case is based on standard penetration test (SPT) data and the other is based on cone penetration test (CPT) data. The SVM model effectively explores the relationship between the independent and dependent variables without any assumptions about the relationship between the various variables. This study serves to demonstrate that the SVM can “discover” the intrinsic relationship between the seismic and soil parameters and the liquefaction potential. Comparisons indicate that the SVM models perform far better than the conventional methods in predicting the occurrence or non-occurrence of liquefaction. 相似文献
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Ali Ghorbani Reyhaneh Jahanpour Hadi Hasanzadehshooiili 《Marine Georesources & Geotechnology》2020,38(1):1-22
AbstractAn elastoplastic, dynamic, finite-difference method was applied to study the effects of nonlinear seismic soil–pile interaction on the liquefaction potential of marine sand with piles. The developed model was well validated using the centrifuge test. The results showed that acceleration, bending moment, and excess pore water pressure complied well with centrifuge test results. The effect of different affecting parameters on liquefaction potential was investigated using parametric study. Using a sensitivity analysis, the pile embedment parameter was shown to be the most influential parameter. Finally, applying the evolutionary polynomial regression technique, a new model for predicting the liquefaction potential was presented. 相似文献
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波浪作用下埕岛海域海底土液化分区 总被引：1，自引：0，他引：1
根据埕岛海域表层沉积物特征,结合该区的波浪实测资料推算的波浪要素,利用动三轴实验得到研究区土体在循环荷载作用下孔隙水压力的增长与振动次数的关系,计算研究区内海底土层的液化可能性和液化所需的时间,并根据土体在不同水深情况下达到液化所需的时间对研究海域进行了液化分区。结果显示,7-8 m等深线之间的海底土体由于受到波浪破碎作用的影响,最易发生液化,液化影响深度也最深,自该海域向近岸和远海,液化可能性降低;土层埋深为2.5 m以浅时,研究区大部分区域液化可能性为高,而到埋深为4 m时土层液化可能性明显降低。 相似文献
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Masoud Rabeti Moghadam Alireza Sadeghi Abdollahi 《Marine Georesources & Geotechnology》2017,35(3):376-396
Breakwaters provide a calm sea basin for ships and protect harbor facilities by reflecting wave energy toward the open sea area. Their performance under environmental loadings is the main concern for coastal engineers. Liquefaction susceptibility of loose sediments of seabed threatens performance of these structures. The article investigates soil liquefaction effects on the seismic performance of Iran liquefied natural gas (LNG) composite breakwater. Performance-based design method, considering both grade of the breakwater and acceptable level of damages, was selected as design philosophy. Liquefaction-induced damages to the breakwater were determined by numerical analysis. Since the obtained level of deformations did not meet allowable damages, soil improvement against liquefaction was considered. Different improvement patterns were proposed based on distribution of pore pressure ratio (ru) beneath the breakwater to control its seismic performance. This investigation revealed that the most important area for soil improvement is located near the toes of breakwater to control the slope instability and performance of the breakwater. 相似文献
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As the offshore wind turbine foundation, the four-bucket jacket foundation has a large stiffness and the structure is difficult to be damaged under seismic load. Nevertheless, the saturated subsoil of the four-bucket jacket foundation tends to be liquefied under earthquake, which greatly affects the safety of offshore wind turbine. Therefore, the seismic performance of four-bucket jacket foundation is mainly reflected in the anti-liquefaction capacity of foundation soil. In this paper, the liquefaction resistance of sandy soil of four-bucket jacket foundation for offshore wind turbine is studied. The liquefaction and dynamic response of sandy soil foundation of four-bucket jacket foundation under seismic load are obtained by carrying out the shaking table test, and the influence mechanism of four-bucket jacket foundation on the liquefaction resistance of sandy soil foundation is analyzed.
相似文献20.
The multi-spring shear mechanism plastic model in this paper is defined in strain space to simulate pore pressure generation and development in sands under cyclic loading and undrained conditions,and the rotation of principal stresses can also be simulated by the model with cyclic behavior of anisotropic consolidated sands.Seismic residual deformations of typical caisson quay walls under different engineering situations are analyzed in detail by the plastic model,and then an index of liquefaction extent is applied to describe the regularity of seismic residual deformation of caisson quay wall top under different engineering situations.Some correlated prediction formulas are derived from the results of regression analysis between seismic residual deformation of quay wall top and extent of liquefaction in the relative safety backfill sand site.Finally,the rationality and the reliability of the prediction methods are validated by test results of a 120 g-centrifuge shaking table,and the comparisons show that some reliable seismic residual deformation of caisson quay can be predicted by appropriate prediction formulas and appropriate index of liquefaction extent. 相似文献