【摘要】 随着城市建设的高速发展,武汉市深基坑机械施工振动荷载诱发软土层过大地面沉降和塑性变形已成为亟待解决的关键问题。针对施工过程中机械振动荷载和往复交通荷载引起的淤泥和淤泥质黏土地基长期沉降问题,考虑到软土的结构特性、触变性和小应变特征,采用室内三轴试验、共振柱试验,现场剪切波速测试、地脉动测试和十字板剪切试验综合分析软土在机械振动荷载和往复交通荷载条件下的沉降、变形机理。论文得出如下结论:高灵敏度淤泥和淤泥质黏土的不固结不排水剪切强度主要是黏聚强度,在振动荷载下,触变性增加;共振柱试验中,随着剪应变的增加,淤泥的共振频率f随之增大,动剪切模量G随之减小,阻尼比λ变化不明显;而淤泥质黏土的共振频率f和动剪切模量G随之减小,阻尼比?有增大的趋势;场地的剪切波速随地层的结构、强度和土层分布而变化;现场地脉动测试3个方向的共振频率均远小于共振柱测试的共振频率;最后,基于机械振动波在淤泥和淤泥质黏土中峰值加速度放大效应,提出修正现有软土塑性应变计算公式的建议。更多还原

【Abstract】 With the rapid development of urban construction, the problems of ground subsidence and plastic deformation of soft clay under dynamic loading of deep foundation construction in Wuhan are urgent to be solved. Considering the issue of long-term ground settlement in the layers of silt and silty clay due to machinery vibration loading and repeated loading as well as the characteristics of structure, thixotropy and small strain of soft clay, the static triaxial test, resonant column test, field shear wave velocity test, ground micro-tremor test and vane shear test are taken to comprehensively analyze the mechanisms of ground subsidence and deformation under the machinery vibration loading and repeated loading. The test results show that the unconsolidated and undrained shear strengths are determined by the cohesive strengths of high-sensitivity silt and silty clay.The resonant frequency of the silt has a positive correlation with shear strain, but the dynamic shear modulus has a negative one.The resonant frequency and dynamic shear modulus of silty clay has a negative correlation with shear strain, but the damping ratio has a positive one. The filed shear wave velocity is determined by the structure, strength and distribution of soil stratum.The resonant frequency of three directions monitored by the ground micro-tremor test is much smaller than that of the resonant columns test. Based on the amplification effect of vibration wave peak acceleration in silt and silty clay, the formula for plastic strain of soft clay is suggested to be modified.更多还原