考虑蠕变、地震效应的土工格栅砂性土加筋挡墙弹塑性有限元分析

Elasto-plastic finite element analysis of geogrid-reinforced sandy soil retaining walls considering effect of creep and earthquake

土工合成材料加筋土挡土墙具有优良的抗震性能,但是由于加筋用的土工合成材料具有显著的蠕变及应力松弛特性,需要深入研究加筋土挡墙在经历蠕变后的地震动力行为及震后的进一步蠕变以理解其全面的静动力学性能。在已有研究的基础上,应用笔者提出的土工合成材料循环受载、蠕变和应力松弛统一本构模型模拟土工格栅的力学行为,考虑到土工格栅加筋土挡土墙的填土一般为砂性土,而砂性土一般蠕变变形较小,本文应用可以模拟砂土述砂性土非线性静动力性能的广义塑性模型模拟填土,未考虑其蠕变变形。结果表明,在正常加筋长度和密度情况下,加筋土挡墙在经受地震前的蠕变变形会趋于稳定,但筋材内力重分布明显;地震作用使得加筋土挡墙产生较大变形,加筋内力出现较大增长,但结构并未破坏;地震后加筋土挡墙蠕变变形继续发展,而土工格栅加筋会出现内力松弛现象。

Geosynthetic-reinforced soil retaining walls （GRSRWs） exhibit excellent earthquake-resistant performance during strong earthquakes. However, due to the fact that geosynthetic reinforcements might experience large creep deformation under sustainable loading, it is necessary to investigate the seismic behavior of GRSRWs after long-term creep, as well as the creep behavior after earthquake loading. Elasto-plastic finite element analysis was conducted to analyze the behavior of GRSRWs. The unified constitutive model proposed by the author to describe the creep, stress relaxation and cyclic properties of geosynthetics was used to simulate the reinforcement; a time-independent generalized plasticity model capable of simulating the nonlinear cyclic behavior of sands was used to model the backfill and foundation soils due to the fact that sandy backfill exhibited small creep deformation. It was found that with regular reinforcements, creep deformation would stabilized after sufficient period of time but the internal forces in the reinforcements would be redistributed; the lateral deformation of the wall increased significantly under earthquake loading and the reinforcement forces also increased greatly; after earthquake, the wall experienced considerable creep deformation, while the forces in the reinforcements reduced, but were still larger than those before the earthquake loading.