长期循环荷载作用下泥炭质土累积变形简化计算方法研究

Simplified calculation method for the accumulated deformation of peaty soil under long-term cyclic loading

交通荷载作用下软土地基附加变形预测中,人们往往关心的是地基的长期累积变形量,而非每一次循环过程中的变形情况。为此,考虑到长期循环荷载作用下土体累积残余变形发展规律与静荷载下土体蠕变变形相似的特点,将循环荷载作用次数等效为时间度量单位,引入蠕变计算理论中的蠕变势函数,结合不排水条件下土体循环累积偏应变经验模型,并基于临界状态理论,建立了可描述土体三维循环累积变形的简化计算方法。利用隐式回退应力积分算法,建立了土体循环累积变形计算数值模型,并基于Abaqus二次开发接口,编制了UMAT子程序。利用该方法对昆明泥炭质土不排水循环三轴试验结果以及地铁荷载下泥炭质土地基的长期变形进行了模拟,验证了该方法的有效性以及数值稳定性。

The cumulative deformation of subsoil is more cared than the deformation raised during every cycle when predicting the deformation of soft ground subjected to traffic loading.Considering that the development of cumulative deformation of soil subjected to cyclic loading is similar to the creep under static loading,the number of loading cycles was equivalent to a time measuremeut unit.Based on the critical state theory,a simplified method for calculating the 3D cyclic cumulative deformation of soil was established by introducing a creep potential function and utilizing the empirical model for the cyclic cumulative axial strain in typical undrained cyclic triaxial tests.Then,a numerical scheme for the proposed model was proposed based on an implicit stress integration algorithm.It was implemented by compiling a UMAT subroutine and utilizing the user-defined material model in the commercial FEM software ABAQUS.Finally,a series of undrained cyclic triaxial compression tests and the long-term settlement of peaty soil under subway loading were simulated by the proposed simplified method,which validates the rationality and stability of the numerical model.