辽西冻风积土动力测试与动损伤机理研究

Dynamic tests and damage mechanism of frozen aeolian soil in western Liaoning area of China

风积土颗粒间包含的孔隙自由水在冬季负温作用下会发生冻结现象。为研究冻风积土在行车等动荷载作用下产生的动力损伤机理及其特征,利用GDS冻土三轴测试系统对不同条件下的冻风积土试样进行三轴加载,获得了不同条件下的动应力–应变曲线,并利用有效应力分析法对损伤有效应力及累积塑性变形进行确定。将Helmholtz自由能作为塑性势函数建立了损伤演变率与损伤释放率之间的数学关系,并依照塑性势函数和累积塑性变形率间的线性假设建立损伤演化模型。利用本文所提出的有效应力分析法对建立的P模型参数进行拟合,结果表明P模型计算结果与相关文献动损伤模型计算结果比较吻合。对比由循环加载造成的疲劳损伤与塑性区发展造成的塑性损伤发展过程,得到了冻风积土初期动损伤以塑性损伤为主,后期以疲劳损伤为主的结论,并且确定各条件下塑性损伤的阈值,为冻风积土路基的动力灾害防治提供理论依据。

The pore free water contained in the aeolian soil particles will freeze under the negative temperature in winter. In order to study the dynamic damage mechanism and characteristics of frozen aeolian soil under dynamic load, triaxial loading tests on frozen soil samples under different conditions are carried out by using the GDS frozen soil triaxial test system. The dynamic stress-strain curves under different conditions are obtained, and the effective stress analysis method is used to determine the damage effective stress and cumulative plastic deformation. The mathematical relationship between damage evolution rate and damage release rate is established by using the Helmholtz free energy as the plastic potential function, and the damage evolution model is established according to the linear assumption between plastic potential function and cumulative plastic deformation rate. The parameters of the model are fitted by the proposed effective stress analysis method. The results show that the calculated results of the model are in agreement with the calculated ones of damage model in related literatures. It is concluded that the dynamic damage of frozen aeolian soil is mainly caused by plastic damage initially, while fatigue damage later. By comparing the two damage development processes, the initial damage to the frozen soil and the threshold of plastic damage under each condition are determined. It may provide the theoretical basis for dynamic disaster prevention and control of frozen aeolian roadbed.