砂土-格栅筋土界面特性的本构模型研究

Study of constitutive model of sand-geogrid interface behavior in geogrid/geotextile reinforced soil

基于砂土与土工格栅、土工织物界面的室内大型直剪试验,分析了两种不同界面的力学性能。试验结果表明,峰值、残余剪切应力与界面剪胀性曲线存在一定的联系,即峰值强度通常会发生在界面相对减缩过程结束和残余剪切强度发生在界面的相对剪胀过程结束。加载过程中由于土工合成材料的逐步磨损、褶皱或者断裂导致了筋土界面强度出现较为明显的强度软化现象,在界面抗剪强度的研究中不可忽略。在试验基础上提出一种能够描述筋土界面力学性能的组合本构模型,该模型包含4个关系式:(1)峰值、残余强度包络线;(2)强度峰值前的双曲线模型;(3)强度峰值后的位移软化模型;(4)反映剪胀特性的界面剪胀模型。该组合模型的预测结果与直剪试验结果吻合较好,表明所用模型是合理的。

Experiments were conducted in a large-scale direct shear apparatus to study the mechanical behavior at the sand-geogrid(S-GG) and sand-geotextile(S-GT) interface. The results show that a certain relationship exists between peak/residual shear strength and shear dilatancy of interface. That is, peak shear stress will occur at a stage when relative shear compression finishes, while residual shear stress will occur when relative shear dilatancy finishes. The shear stress obvious reduction with increasing shear displacement is known to be caused by geosynthetics polishing, folding and rupture, which should not be neglected in interface behavior studying. Thus, a combined constitutive model has been presented for predicting sand-geogrid interface behavior. The model is composed of four relationships:(1) The peak/residual shear strength envelope.(2) A hyperbolic relationship model of shear behavior in pre-peak region.(3) A displacement-softening model for post-peak region.(4) Modeling for shear dilatancy of sand-geogrid interface. The predictions made by the proposed model are found to be in good agreement with the results of direct shear tests, so as to prove that the model is reasonable.