粉砂中筒型基础沉贯过程筒–土作用机理试验研究

Model tests on bucket-soil interaction during installation of bucket foundation in silt sand

筒型基础沉贯安装是一项关键施工过程,目前相关研究多集中在沉贯阻力与吸力的计算方法上,而缺乏对沉贯过程筒–土作用机理研究。针对这一问题,开展了粉砂中筒型基础沉贯试验,得到了静压和吸力沉贯工况下筒壁内、外侧所受土压力发展变化规律。静压试验结果表明,筒壁内侧所受土压力远大于外侧,内侧土体挤压程度随下沉深度增加而增大,外侧相反。吸力试验结果表明,施加吸力时内侧土压力减小,外侧土压力先增大后迅速减小至稳定值,吸力产生的渗流可以大大减小端阻力与内侧摩阻力。试验结果还表明现有临界吸力计算公式是过于保守的,并根据试验结果对现有计算所需吸力的方法进行了修正,得到了一种更加准确的计算方法。

The installation of bucket foundation is a vital construction procedure. The existing relative studies have mainly focused on the methods for calculating the penetration resistance and required suction. However, the understanding of the soil-skirt interaction during the installation is not clear yet due to inadequate test data. Model tests on the installation of bucket foundation are carried out in silt sand. The inner and outer soil pressures on the skirt are measured under both jacking installation and suction installation conditions. The jacking test results show that the inner soil pressures on the skirt are much larger than the outer ones. The compaction extent of the inner sand grows with the increase of the penetration depth, which is contrary to that of the outer sand. The suction test results show that the inner soil pressures decrease dramatically when the suction is applied. The outer soil pressures, however, increase firstly and then fall down to stable values rapidly. The inner friction and tip resistance are greatly reduced due to the seepage effects. The test results also indicate that the existing critical suction is too conservative. Based on the test results, the existing prediction method for the required suction is modified and evaluated, and a more accurate method is obtained.