冻融循环后筋土复合体加载破坏试验研究

Loading Test of Reinforcement-Soil Complex Suffered Freeze-Thaw Cycling

模拟野外实测降温过程,对筋土复合体进行开敞条件下的冻融循环,然后对筋土复合体进行加载破坏试验,得到加载过程中墙体的竖向变形与墙面的水平位移结果.对试验结果进行有限元数值计算,其中土的本构模型采用Drucker-Prager(D-P)理想弹塑性模型,单元类型选用四节点平面等参单元,把筋材的作用等效成附加应力沿筋的方向加在土骨架上,取加筋土中的土体进行计算.结果表明:筋土复合体冻融循环后在约束固脚的方式下进行加载试验,破坏形式以沉降变形破坏为主,墙体中部产生的变形增量最大;等效附加应力法单元网格划分中只出现土单元,取消了模拟筋材的单元和筋-土之间的界面单元,可以直接利用素土的本构模型,不必针对加筋土复合体建立复合材料的本构模型,计算结果符合一般规律;冻融循环使表层土变得疏松,局部变形偏大,导致模型试验实测值大于有限元计算值.

Aimed at modeling the in-situ measured temperature process, freeze-thaw cycling test on reinforcement-soil complex under open conditions was made. Then loading test was carried out, and the test results about vertical deformation of reinforcement-soil complex and lateral displacement of wall panel during loading process were recorded. The test data were processed by FEM numerical calculation. Drucker-Prager （D-P） ideal elastoplastic constitutive model was adopted to be the constitutive model. Four nodes plane isoparametric element was taken to be the unit type. The effect of reinforcement material was thought to be an equivalent additional stress on soil skeleton along the reinforcement direction. The soil in the complex was chosen as research object. It is found that under bank-base-strengthen constraint condition,the main failure mode is settlement deformation. The maximum deformation occurs in the middle of the wall. Only soil unit appears in the equivalent additional stress grid. After the reinforcement material unit and the interface element between the reinforcement material and soil cancelled, the constitutive model of soil can completely replace the model of reinforcement-soil complex. So the number of element partition will be reduced, and the effect of complex material anisotropy on the calculation results will be disappeared. The calculation results are in accordance with general law. It is found that the freeze-thaw cycling results in the surface soil loose and the local deformation larger, which cause the measured value larger than that from FEM calculation.