考虑土应变软化和率效应的桶形基础上拔模拟

Simulation of suction caisson foundations under uplift load considering strain softening and rate effect of clay

研究桶形基础上拔承载特性对海上张力腿油气平台和多腿风机等构筑物安全服役性能具有重要意义.基于ABAQUS二次开发,建立考虑软黏土应变软化和率效应的桶形基础上拔数值分析模型,并将上拔数值模拟结果和理论值、试验值进行对比,验证了数值模型的有效性.模拟分析发现,软黏土应变软化参数对桶形基础上拔峰值荷载的影响在5%以内,而率效应对上拔荷载影响明显,率效应参数变化引起的上拔峰值荷载差异达40%以上;上拔峰值荷载随桶外壁粗糙度线性增加,桶外壁粗糙度引起的应变软化和率效应变化对上拔荷载影响可以忽略;对于群桶基础,桶间距越小,极限承载力群桶效应越明显,承载力降低最多可达10%,桶间距超过1.5倍桶径后,群桶效应可以忽略.

It is of great significance to study the uplift bearing characteristics of suction caisson foundations for the safe service performance of offshore tension leg platform(TLP) and multi-leg wind turbine. Based on the secondary development of ABAQUS, a numerical model of suction caisson foundations considering strain softening and rate effect of soft clay is established. The numerical results are compared with the theoretical and experimental results to verify the reliability of the numerical model. The simulation results show that the change of soft clay strain softening parameters has less than five percent influence on the peak of uplift load, while the rate effect has obvious influence on the peak of uplift load and the difference caused by the change of rate effect parameters is more than forty percent. The peak of uplift load increases linearly withthe caisson outer wall roughness, and the effect of strain softening and rate effect on the uplift load caused by the caisson outer wall roughness can be ignored. For the caisson groups foundation, the caisson group effect becomes obvious with the decrease of caisson spacing, and the bearing capacity can be reduced by up to ten percent. When the caissons spacing is more than one and a half times of the caisson diameter, the caisson groups effect can be ignored.