【作者】 魏楠；

【导师】 陈龙珠；

【作者基本信息】 上海交通大学 ， 防灾减灾工程及防护工程， 2008， 硕士

【摘要】 作为加固砂土类地基的有效措施,振冲法在得到了广泛应用的同时,也逐渐暴露出一些施工难题:在处理深厚砂土地基、含卵砾中粗砂地基时,出现了地基深处成孔缓慢、加固效果差、难以达到设计深度等问题。目前普遍使用的电动型振冲器难以解决这些问题,因此在一些大型工程的地基处理中已经应用进口高频液压振冲器。液压型振冲器具有振动频率高、激振力大、贯穿能力强、输出功率大等特点,有利于振冲器的贯入而无需冲水成孔,适用范围广。但是目前饱和砂土地基高频振动液化特性的研究较少,不利于高频振冲器的开发和推广应用工作。因此,本文将采用有限差分程序FLAC2D对振冲法施工过程进行数值模拟,分析振动过程中振动时间、孔隙水压力、地基土体水平振动加速度与振动频率的关系,以了解振动频率对饱和砂土地基振动液化情况的影响。高频振动技术是国外近10年来在桩基施工方面开发并推广应用的新技术,了解高频液压振动桩锤将有助于国产高频液压振冲器的研制开发。因此,本文在饱和软粘土地基上对国产高频振动桩锤的工作性能进行了初步的监测,分析振动频率对桩身振动量、地基土体振动量的影响,结果表明我国已经具备研制液压高频振冲器的技术能力。本文是国家自然科学基金资助项目“饱和土的高频振动特性及其应用研究”(50779034)的部分内容。更多还原

【Abstract】 As the effective method of densifying sandy soils, vibroflotation has been used widely around the world. But some difficult problems were gradually discovered. When vibroflotation was used to deal with deep deposits of sand or complex geology, the effect of improvement was not as good as people’s expection in advance. And the slow velocity of drilling, the unsatisfactory improvement and the phenomena of difficult drilling were also discovered. It is difficult to deal with these problems only by depending on electric vibrator. So imported vibrator of high-frequency has been used in the foundation treatment of some large construction. Because of high frequency, strong vibration ability, strong penetration ability, large output power and so on, imported vibrator of high-frequency can deal with these problems that electric vibrator can not deal with. It also can penetrate without water of pressure, and is suitable for different condition.However, there is little work on the research of dynamic behavior of soil under high frequencies. It is not advantaged for the development and wide use of this mechanism. The paper mainly focuses on the research of saturated sand foundation at high frequencies through finite-difference computer codes FLAC. The relationship between vibration frequency and time of vibration, pore water pressure and the acceleration of soil will be study. The effect of vibration frequency on the liquefaction of sand foundation will be researched.Piling with high-frequency vibration has been developed and widely used abroad in recent 10 years. It is significative to study the mechanism of piling with high-frequency vibration for the development and use of vibrator of high-frequency. The monitoring research of the piling on saturated foundation at high frequencies is done to analyze the effect of frequency on the acceleration, the velocity, the displacement of the pile and the soil. It is doable for our countries to develop vibrator of high-frequency through the result of research.The research work in this paper was supported by the Natural Science Foundation of China with the grant number 50779034.更多还原