任意加载条件下土工合成材料的弹粘塑性及本构模型

ELASTO-VISCOPLASTIC BEHAVIOR AND CONSTITUTIVE MODELING OF GEOSYNTHETIC REINFORCEMENTS UNDER ARBITRARY LOADING

研究了4种土工合成加筋材料(PET、PAR、PVA和Aramid)试样在任意加载历史条件下的弹粘塑性,尤其是粘性特性。试验过程中,实现了恒定应变率加载、应变率逐步变化加载、蠕变加载以及荷载松弛。依据加载速率效应对土工合成加筋材料的粘性特性进行评价。试验结果表明,根据土工合成加筋材料类型的不同,至少存在三种粘性特性,即等速粘性、瞬时粘性和混合粘性,其中PET土工格栅表现为混合粘性,PAR、PVA和Aramid土工格栅表现为等速粘性。基于非线性三要素模型框架,针对上述三种粘性特性,提出了一种弹粘塑性本构模型。该模型可以描述土工合成加筋材料在任意加载历史下的粘性效应,包括:在不同恒定应变率单调加载时的荷载-应变响应、加载应变率发生任意变化时的荷载-应变响应、以及蠕变和荷载松弛。最后,利用该模型对上述4种土工合成加筋材料的试验结果进行模拟。结果表明,所提出的三要素弹粘塑性本构模型能够合理地模拟土工合成加筋材料的粘性特征。

Based on the test results of four types of geosynthetic reinforcements （PET, PAR, PVA and Aramid） during arbitrary loading history, their elasto-viscoplastic, especially viscous properties are investigated. Some tests were performed at constant but different strain rates. To evaluate the loading-rate effects on geosynthetic reinforcements, the strain rate was changed stepwise many times with a pair of creep and load relaxation under otherwise monotonous loading on the different types of reinforcement specimens. It is found that there are three types of viscous properties for different geosynthetic reinforcements, including Isotach viscosity, TESRA （Temporary Effects of Strain Rate and Acceleration） viscosity, and combined viscosity. An elasto-viscoplastic constitutive model, described in a nonlinear three-component framework, is presented to simulate the effects of the viscous property on the load-strain behavior of geosynthetic reinforcements. The model is able to simulate the load-strain-time behavior of geosynthetic reinforcements for arbitrary loading history, which is not only the load-strain behavior during monotonic loading with and without step changes in the strain rate but also the one after creep and load relaxation. By comparing the simulated results with the experimental data of geogrids presented in this study, it is shown that the three-component elasto-viscoplastic model can simulate well the viscous properties of geosynthetic reinforcements.