【作者】 刘涛；

【导师】 周东； 蓝日彦；

【作者基本信息】 广西大学 ， 工程硕士（建筑与土木工程领域）（专业学位）， 2016， 硕士

【摘要】 北部湾吹沙填海场地与自然沉积场地具有截然不同的成因属性及工程属性。原深厚的海积软土变成新陆域大面积的软弱下卧层；各土层欠固结且持续受外界因素扰动,“边成型、边固结、边承载”；海积软土直接覆盖在海底基岩之上,由基岩导入的地震波可直接进入。填海场地内外动力地质作用较为活跃,其下伏面状厚层～巨厚层状淤泥质软土往往使其在地震作用下遭受的地震灾害更为严重,因此对北部湾吹填场地进行场地地震反应分析具有重要意义。本文通过现场勘察资料及室内外实验结果建立三维模型,进行吹沙填海动力响应计算分析并借助GDS动三轴对北部湾填海场地土动力特性进行研究。主要研究工作内容如下。(1)结合工程实际条件选取具有代表性的北海铁山港及钦州港填海场地作为分析实例,分析其在地震作用下加速度、傅里叶谱及反应谱变化情况。结果表明,北部湾吹沙填海场地对低频地震波具有明显放大作用,对高频地震波过滤效果明显。(2)通过室内动三轴实验,研究了固结压力、动荷载频率对重塑软土的动剪切模量、阻尼比与动剪应变关系曲线变化规律的影响。在同一频率地震荷载作用下土样动剪切模量在动剪应变增大时逐渐减小,对于确定的动剪应变值,随着固结压力越大,动剪切模量比越大；随着动剪应变增大阻尼比呈增大趋势,怕保持一定时,固结压力越大阻尼比反而减小。(3)分析影响北部湾吹沙填海场地动力效应的场地条件因素,本文针对地下水位变化对吹沙填海场地动力响应影响展开数值模拟研究,分析了不同水位条件时吹填场地动力响应变化规律。地表峰值加速度放大系数总体随地下水位埋深减小而增大且影响明显。(4)通过正交试验设计,分析影响场地动力响应主要因素,选取L16(45)正交表进行数值模拟,确定合理的水平值,安排了4因素4水平的正交试验。确定16组场地试验模型的参数,通过FLAC3D建立16组场地模型,并进行计算分析。结果表明海积软土层厚度对吹填场地动力响应影响最大,砂土相对密实度和吹填砂层厚度次之,地下水位影响最小。更多还原

【Abstract】 The site of blowing sand reclamation has a distinct causing properties and engineering properties with the natural sedimentary site. The original of deep marine soft soil has become the large area of soft substratum soil of the new land. The soil layer is unconsolidated and continuous disturbance by the outside factors, going through "forming, consolidation, carrying" characteristics. Seismic waves imported from the bedrock can be directly into the marine soft soil covering at the bottom of the sea bedrock directly. In the field, the internal and external dynamic geological effect is more active, and the deep layer of the underlying surface of the thick layer of silt and soft soil is more serious, so it has important significance for the seismic response analysis of the Beibu Gaulf.In this thesis, through the field survey data and the experimental results of inside and outside establish three-dimensional model for calculating dynamic response of blown sand reclamation analysis, With the help of GDS dynamic triaxial apparatus, the beibu Gulf reclamation area soil dynamic characteristics were studied.The main working contents of this paper are as follows:(1) combined with the actual condition of selected projects Beihai TieShan Port representative and Qinzhou Port reclamation site as an analysis example, to analyze its under the earthquake acceleration Fourier spectrum and response spectrum changes. The results showed that Beibu Gulf blowing sand reclamation site amplification low-frequency seismic waves, high-frequency seismic waves obviously filtered.(2) through the dynamic triaxial experiment to research the consolidation confining pressure, to reshape the soft soil of dynamic shear modulus, damping the impact of dynamic load frequency. A certain frequency, soil dynamic shear modulus gradually decreases when dynamic shear strain increases, the dynamic shear strain values determined, along with the greater consolidation confining pressure, the greater the dynamic shear modulus ratio; With the move shear strain increases the damping ratio tended to increase.γd constant, the greater the pressure damping consolidation rather than decrease.(3) Analysis of Beibu Gulf site dynamic effects of blowing sand reclamation site conditions factors, In this paper, groundwater level changes in response to the impact of blowing sand reclamation sites numerical simulation of dynamic expansion, Reclamation site dynamic response analysis of the variation of different groundwater conditions. Overall, the peak ground acceleration amplification factor increases obviously with decreasing of the water depth.(4) Through orthogonal design, analysis the main factors affecting the site dynamic response, selected the orthogonal table of L16(45), determine the reasonable level, arranged the finite element orthogonal experiment of 4 factors 4 levels. Determine the parameters models of 16 groups. The FLAC3D software analysis indicate:the factor of marine soft soil thickness has the greatest impact on reclamation site dynamic response, followed by Sand relative density and Sand thickness, while the water table has the least impact on reclamation site dynamic response.更多还原