【作者】 李晓广；

【导师】 喻国良；

【作者基本信息】 上海交通大学 ， 港口、海岸及近海工程， 2011， 硕士

【摘要】 砂土液化在地震中较为常见,液化后地基失效,导致大量建筑物损毁。然而,砂土液化在工程上被正面利用。例如,振动注浆被用于处理软弱地基,该方法首先通过振动机具的冲击振动,在砂土地基内形成软化区,然后利用注浆管将浆液压入砂土中;通过振动使混凝土液化泛浆再碾压形成碾压混凝土(RCC)等等。本文的研究对象为含水饱和的粉细砂,针对其在振动载荷作用下可以液化这一工程特性,在不同工况条件下,利用静力触探仪测得粉细砂锥尖阻力,对比高频振动前后锥尖阻力变化情况,分析讨论了振动荷载作用时间、振动荷载作用频率、振动荷载作用距离等因素对于砂土液化效果的影响程度;利用粘度计测得不同工况下砂土液化后的粘度,通过对比液化前后粘度的变化,分析讨论了砂土的流变特性。研究发现:1)在不同振动荷载作用时间下,振动时间越长,液化效果越明显,但存在一个临界液化时间,超过临界液化时间,液化效果将不会随之增加;2)在不同振动荷载作用距离下,砂土液化效果随着振动荷载作用距离的增大而变得不明显,振动载荷的作用在砂土中的传播随着距离加大而衰减,导致液化效果减弱;3)砂土液化效果随着振动频率的增加而变得明显,特别在振动荷载作用频率与砂土固有频率接近时,因为存在共振效应,此时砂土液化效果最为明显;4)在高频振动前后的粉细砂表观粘度显著减小,存在剪切稀化现象。液化后粉细砂的特性仍属于非牛顿流体,符合幂律流体。更多还原

【Abstract】 Liquefaction is very common in the earthquakes. The foundations of constructions lost efficacy,a large number of buildings were damaged due to liguefaction. However,liquefaction is friendly used in engineering practice. For examples,the basic principle of vibration grouting technique is adopted to treat soft land. Roller Compacted Concrete (RCC) is formed by“vibration and then rolled”.This study focused on fully saturated silt. Under different conditions, the cone resistances of fully saturated silt were measured by a static penetrometer.In order to comparing the resistances pre and post vibrations,the influences of vibration time,frequencies,and distance away from the vibration source on the liquefaction characteristics were discussed; furthermore,the viscosity of the liquefied silt was measured using a viscometer,and the viscosity results for different cases were compared to find the silt’s rheological features. It was found in this study that: 1) Under different vibration time,the longer the vibration time is,the more the liquefaction effect would generally have,neverthness,there is a critical liquefaction time,which means if the vibration time is longer than the critical liquefaction time, the liquefaction effect would no longer increase; 2) Under the different vibration distance,the farther vibration distance is,the less the silt liquefaction would become,but as the vibration distance becomes farther, the vibration effect would get weak. 3) The higher vibration frequency is, the better the liquefaction would be. When the vibration frequency is close to silt inherent frequency,the liquefaction behaves the most. 4) After high frequency vibrations was applied , the silt apparent viscosity was significantly decreased,a shear thinning phenomenon exists. The liquefied silty still belongs to a kind of non-newtonian fluid,i.e.,the power-law fluid.更多还原