裙式吸力基础抗拔过程中的渗流特性

Seepage characteristics around skirted suction caisson during uplifting

饱和砂土中的吸力基础在拔出过程中,基础内外产生的孔隙水压差会引发渗流。采用有限元数值模拟分析了传统和裙式吸力基础在上拔过程中有关渗流场特性的分布规律。结果表明:传统吸力基础周围,土体孔压随时间逐渐消散而有效应力逐渐增加;水头等势线在桶内分布密集且呈层状,桶外部分布稀疏;在桶底端部渗流速度梯度曲线呈现多重圆弧包线桶尖端处渗流速度最大。裙式吸力基础与传统吸力基础在土体孔压、有效应力的变化趋势及水头等势线分布规律上基本一致,只是大小发生了变化。裙式吸力基础的水头损失主要存在于主桶内部和裙结构内部。裙结构对渗流有较大影响,裙结构内部渗流速度远大于主桶内部渗流速度;裙的增加使渗流路径变长,导致裙式吸力基础主桶内最大水流势能、渗流速度均小于传统吸力基础。

During the uplifting of suction caisson in saturated sand,the difference of porewater pressure between inside and outside of the caisson will lead to seepage.The finite element numerical method is used to study the seepage characteristics of the traditional and skirted suction caissons during the uplifting.The results show that the pore pressure of soil gradually dissipates with time,and the effective stress gradually increases for the tradotional suction caissons.The hydraulic head equipotential lines distribute densely in a layered form inside the bucket and sparsely outside the bucket.The seepage velocity gradient curves show multiple circular arcs,and the seepage velocity reaches the maximum value at the bottom of the bucket.The pore pressure,as well as the effective stress of soil,and the distribution of hydraulic head equipotential line around the skirted suction caisson are basically the same as those around the traditional suction caissons,but the values are different.The decrease of hydraulic head mainly occurred in the main bucket and the skirted structure.The skirted structure has a great influence on the seepage characteristics,and the seepage velocity inside the skirted structure is much larger than that inside the main bucket.The addition of skirted structure increases the length of percolation path,and the maximum value of water potential energy and percolation velocity in the main bucket of the skirted suction caisson are less than that of the traditional suction caissons.