在上部均布荷载作用下柔性基础基底压力是均匀分布的，基底以下土体在同一深度附加应力呈现中间大、周围小的分布规律，导致基础沉降中间大、周围小。刚性基础的沉降是均匀的，必然导致基底压力的分布为周围大、中间小。软基上的油罐筏板基础是具有一定刚度的基础，但并非刚性基础，因而基底压力分布应该介于柔性基础和刚性基础之间，沉降为中间大、周围小的不均匀分布。基于ABAQUS有限元分析，结合工程实际情况，采用UH模型作为土体本构模型进行了模拟分析，对筏板厚度、地基刚度等影响基础不均匀沉降的主要因素进行敏感性分析，探求变刚度地基在油罐基础不均匀沉降中的影响规律。

The contact pressure between soil and the flexible foundation under top uniform load is uniformly distributed. The additional stress of subsoil is large inside and small outside, which causes that the settlement of flexible foundation is also large inside and small outside. But the contact pressure between soil and the rigid foundation under uniform load is large outside and small inside, and the settlement is uniform. The thickness of the raft foundation of oil storage tanks is always large but not as large as that of the rigid foundation. So the distribution of the contact pressure is between that of the flexible foundation and the rigid foundation, and the settlement of the raft foundation is large inside and small outside. The authors adopt the UH model(the unified hardening model) as the soil constitutive model to simulate the soil deformation and research the sensitivity analysis of main influencing factors for the nonuniform settlement of the oil tank foundation. And the authors also research the influence of variable stiffness as on the nonuniform settlement.