中文摘要：

高速铁路对基础的变形要求十分严格,为研究高速铁路桥梁桩底砂土层的蠕变变形规律,获取其蠕变模型和模型参数,开展桩底砂土的蠕变试验。针对超长桩桩端高应力环境,通过室内侧限高压单向压缩试验获得桩底土样在多级荷载作用下的应力–应变–时间关系曲线。砂土的压缩变形主要经历瞬时变形、固结变形和衰减型稳态蠕变变形3个阶段。砂土黏弹性蠕变模量受应力水平影响小,蠕变模型可不考虑非线性流变特性。研制蠕变参数拟合程序（CPF）,并利用试验成果,对砂土蠕变模型进行识别和参数确定,结果表明,Schiffman黏弹性模型能较好地描述桩底砂土层的蠕变变形特性。研究成果可供持力层为砂土的超长桩基工后沉降计算及评估利用和参考。

英文摘要：

The high speed railway has strict limitation for foundation settlement,The creep test was performed to investigate the creep deformation law of the compressible soil layers beneath pile toe of the high-speed railway bridge and to obtain the creep model and its parameters. The soil samples were explored from sandy soil layer beneath super-long pile toe and stressed by high-pressure. Its stress-strain-time curves under multilevel pressure were obtained from high-pressure confined compression test. It is found that the compression deformation experience the three stages of instantaneous deformation, consolidation deformation and damped creep deformation and that sandy soil behaved as non-linear creep characteristics for the negligible influence of pressure on creep modulus. A compute program of CPF was developed to determine the creep model and its parameters.The results indicate that the deformation characteristic of the sandy soil could preferably be simulated by the Schiffman viscoelastic model. The valuable reference are provided to calculate post-construction settlement of pile foundation with sandy soil layer beneath the pile toe.