动荷载作用下土工格栅应变软化特性

土工格栅的强度衰减特性对加筋路堤和加筋挡墙的稳定性有重要影响。对塑料土工格栅进行了应力控制式单向循环拉伸试验，研究了循环拉力、预拉力、加载频率等对格栅应变软化及变形的影响。试验结果表明，随着循环拉力、预拉力的增加，格栅的累积应变增大，软化指数增大，强度减弱；荷载振动频率的减小也会产生类似的结果。通过对试验数据的分析，总结了格栅应变软化的规律，并将其引入改进的Iwan模型中，建立了能描述循环拉伸荷载作用下土工格栅的拉力应变关系的模型，通过将模型计算结果与试验结果的对比，验证了模型的正确性。

Degradation of Geogrids under Cyclic Tensile Load

The degradation characteristics of geogrids have important influence on the stability of reinforced embankments and retaining walls. A series of unidirectional cyclic load-extension tests under stress control were carried out on plastic geogrids. The influence of cyclic tension, pretension and load frequencies on strain and degradation characteristics of geogrids was studied. It is observed that, with the increase of cyclic tension and pretension and the decrease of load frequencies, the accumulative plastic strain and degradation index of geogrids increase, and the stiffness of geogrids decreases. Based on experimental data, the empirical equation for softening of geogrids was proposed. A modified Iwan model was put forward to describe the stress-strain relationship of the geogrids subjected to cyclic tensile load. The proposed model was proved to be reasonable by comparing the experimental data with the numerical results.