Micro-mechanism Analysis Of Pullout Behavior Of Reinforced Sand Cushion With Denti-inclusions

Reinforcement-soil interface parameters are significant factors for analysis and design of reinforced earth structures. Soil reinforced with denti-inclusions is produced by vertical inclusions combined with the conventional grid reinforcement. This kind of soil reinforcing measure provides the horizontal friction, and the vertical elements give significant resistance to soil. However, theory research about this new reinforcement is lack. It’s unclear about the behavior of interface between soil and reinforcement. In this paper, numerical simulation of reinforced sand cushion with denti-inclusions adopting PFC3 D was conducted. The evolutional laws of relative displacement and stress were analyzed from microscopic aspect. And, the behavior of interface between soil and reinforcement were discussed. The research work of this paper includes three aspects as follows:(1) A numerical model based on pullout test for reinforced sand cushion with denti-inclusions was established. In this model, elliptical group particles were developed to simulate the properties of sand particles, using parallel-bond model to simulate the reinforcement. The displacement, contact force, stress and porosity were measured to analyze the micro-mechanical properties of the interface and the development law of shear bond. The results show that stress concentration occurs nearby the denti-inclusions and rare soil stress at the terminal of reinforcement.Because of the denti-inclusions, the shear bond is unsymmetry, and the displacement of particles at the side of the reinforcement with densi-inclusions appears wavy shear band.(2) A series of numerical models were designed to analyze the effective of sand cushion’s thickness and porosity on pullout resistance and interface’s properties. The results show that the frictional effect of interface will be greatly enhanced when sand cushion is placed in clay, and the ultimate pullout resistance has been significantly improved. But too thick sand cushion isn’t beneficial. The optimal thickness relates tothe type of geosynthetic. Increasing the compaction of sand cushion, the ultimate pullout resistance is enhanced for the normal pressure.(3) Reinforcement with different traverse ribs’ spacing and height of the denti-inclusions were simulated for pullout tests. The results show that an appropriate spacing benefits to eliminate the interaction of denti-inclusions and developing the passive resistance of transverse ribs which located in the rear area, at the same time,the transverse ribs’ deformation is increased. Compared with traditional grid reinforcement, the proposed reinforcement with denti-inclusions has a higher pullout resistance, because the vertical elements provide passive resistance. Increasing the height of denti-inclusions which is placed in clay, pullout resistance is enlarged more than that of the sand cushion. Variation of spacing influences the form and stiffness of geogrids and results in the interaction between soils and reinforcement changed.