考虑多年冻土蠕变特性的抗拔桩非线性有限元分析

NONLINEAR FINITE ELEMENT ANALYSIS OF UPLIFT PILE WITH CONSIDERATION OF CREEP CHARACTERISTIC IN PERMAFROST

结合青藏铁路多年冻土区钻孔灌注抗拔桩现场载荷试验,依据场地多年冻土地温实测资料、物理力学参数以及冻土类型,考虑多年冻土蠕变特性,对冻土区钻孔灌注抗拔桩进行非线性有限元分析。桩–土体系有限元分析采用三维十节点四面体等参单元,桩–土相互作用采用面–面接触单元;同时,假定桩–土体系本构模型服从Drucker-Prager屈服准则。通过数值模拟计算结果与抗拔桩现场载荷试验的对比分析,结果表明,考虑冻土蠕变的分析结果与试验值较为接近,不考虑冻土蠕变时,当外载荷较大时桩顶上拔位移的计算值要比试验值小43%左右,但外载荷较小时两种计算结果差别不大。因此,考虑冻土蠕变的分析方法更比较符合多年冻土区钻孔灌注抗拔桩的实际受荷特点。

Combined with the field loading test of large diameter uplift pile casted in-situ in permafrost region of Qinghai-Tibet Railway,based on actually measured ground temperature in permafrost region,physico-mechanical parameters and frozen soil type,nonlinear finite element analysis is conducted to analyze uplift pile casted in-situ in permafrost region considering creep characteristic.Three-dimensional 10-node tetrahedral structural element is adopted in pile-soil system.Surface-to-surface contact element is used in pile-soil interaction,and the constitutive model of pile-soil system is assumed to obey Drucker-Prager yield criterion.Through the comparison of numerical results and test ones,it is shown that the analytic result and test result of creep deformation agree well with each other.If not considering frozen soil creep in calculation,the difference is not too much when external load is small;and the calculation value of displacement at the top of pile uplift is about 43% smaller than the test result when external load is large.So the method in which frozen soil creep is considered can truly reflect the actual characteristic of uplift pile in permafrost region.