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在大桩径、小桩距的群桩条件下,不仅有来自桩侧、桩端和承台传递的多重应力叠加,还有群桩对桩间土的夹持作用影响,桩-土-承台之间作用更加复杂。用有限差分软件模拟固定桩距、桩径,变化竖向荷载下桩-土-承台的相互作用。从各层土的侧摩阻力、不同位置桩的桩顶荷载、荷载-沉降关系、桩间土体位移等方面的计算结果分析桩-土-承台之间的相互影响。结果表明,荷载超出117.8 MN(略大于Pu/2,Pu为群桩极限承载力)后,群桩对上部桩间土的夹持作用开始减小,桩侧上部侧摩阻力增大;桩侧下部侧摩阻力在多重应力叠加作用下呈减小趋势,不同位置的桩侧摩阻力影响范围有差异;用群桩沉降达到5%倍桩径时的荷载作为群桩的竖向极限承载力是可取的;当沉降与桩径的比值超出1%后,承台分担荷载的比例逐渐增大,群桩分担荷载的比例减小。
Under the condition of pile group with large pile diameter and small pile spacing, not only the multi-stress superposition which is transferred from the pile side, the pile end and the pile cap, but also the effect of pile groups on the interception of soil between piles, The role of Taiwan is more complicated. Using Finite Difference Software to Simulate the Interaction of Pile - Soil - Cap with Fixed Pile Pitch, Pile Diameter and Varying Vertical Load. The interaction between pile-soil-cap pile is analyzed from the calculation results of the lateral friction of each layer of soil, the pile top load of different position piles, the load-settlement relationship and the displacement of soil between piles. The results show that when the load exceeds 117.8 MN (slightly larger than Pu / 2, Pu is the ultimate bearing capacity of group pile), the clamping effect of pile groups on the soil between upper piles begins to decrease and the friction on the upper side of pile increases. The frictional resistance at the lower part of the pile tends to decrease with the superimposition of multiple stresses, and the influence range of the pile friction at different positions is different. The vertical ultimate bearing capacity of pile with pile pile settlement of 5% Desirable; when the ratio of settlement to pile diameter exceeds 1%, the proportion of shared load on the platform gradually increases, and the proportion of load shared by group pile decreases.