基于Mindlin位移解的超大群桩基础沉降计算

针对18根和64根超长大直径群桩基础,采用Mindlin位移解,假定桩端阻力为集中力和桩侧摩擦阻力呈向下线性增加分布形式后,推导出沉降计算公式.在苏通长江公路大桥主桥索塔群桩基础离心试验的模型地基条件下,按照变形比法来确定压缩土层的计算深度,对这两类超长大直径群桩进行沉降量计算.研究结果表明,与离心模型试验沉降值相比,两类群桩理论计算沉降值均偏低,18根群桩基础沉降理论计算值偏低16.8%,而64根群桩基础偏低39.9%.可见,用基于Mindlin位移解对超长大直径群桩基础进行沉降计算时,理论值偏低,同时也表明群桩效应对桩数较多的群桩沉降计算影响较大.

Settlement Calculation Based on Mindlin Displacement Solution for Extra Long and Large Diameter Pile Groups Foundation

Based on Mindlin displacement solution,the formulas for settlement of 18 and 64 extra long and large diameter pile groups are deduced according to the hypotheses that resistance to pile end is concentrated force and skin friction of pile is linear increasing distributed force.According to displacement ratio to decide calculated depth of compressed soil layers,the settlements of two types of pile groups are obtained at the condition of the foundation soils used by centrifugal model tests for pile groups under main tower of Sutong Yangtse River Highway Bridges.Comparing calculated settlements with those of centrifugal model tests, these theoretically calculated values are lower than experimental values of settlement by centrifugal model tests,16.8% for 18-pile groups foundation and 39.9% for 64-pile groups foundation.So,based on Mindlin displacement solution,calculated settlement of extra long and large diameter piles group foundation is lower,and pile group effect have much great influence to more pile number than that of less pile number.