# Pullout Behavior of Nail Reinforcement in Nailed Soil Slope
## 1 Introduction
The pullout and bond resistance of soil nails of alluvium soil by considering the overburden pressure effect are evaluated by [PERSON] and [PERSON] [15] using nail pullout physical models. The have observed that the bond resistance of soil nails increases as the overburden pressure increases in coarse grained soil, but the overburden pressure does not have a significant effect on the bond resistance in clay soil. An analytical model was developed by [PERSON] et al. [16] to predict the pullout resistance mechanism and they have shown that an apparent friction coefficient decreases with the increase of the applied normal confining pressure around the soil nail. [PERSON] et al. [17] have simulated the pullout behavior of a soil nails in a soil mass under different overburden pressures using the finite element technique. The constitutive relationship in soil is based on a modified Drucker-Prager/Cap model, while that of the soil-nail interface is described by a Coulomb friction model. The laboratory pullout tests are conducted by [PERSON] et al. [18] on a new screw nail in sandy soil. The testing results indicate that the slip mechanism of screw soil nails is different, and that the resultant pullout capacity of screw soil nails is higher when compared with the conventional soil nails. The progressive shear strength mobilization along the embedment of the thread-bar grouted anchor is examined by [PERSON] et al. [19] using properly installed strain gauge monitoring. The grouted anchor is founded in the nonhomogeneous ground, a sand deposit followed by marly clay. They found from the results that a very low shear strength is offered by the sand and fast mobilization of the shear strength is in the marly clay at the deep end of the anchor. The behavior (pullout resistance) of a hollow and solid shaft helical soil nail installed in cohesionless soil were examined by [PERSON] et al. [20] under varying parameters such as helical soil nail properties, nail shaft types, installation torque, and overburden pressure. They have shown that additional helices will only contribute to pullout capacity if located outside the region of soil mobilized in the failure mechanism of a lower helix and solid shaft helical nails can be replaced by hollow nails without compromising on pullout capacity, adding to a reduction in construction cost. [PERSON] et al. [21] investigated the effect of excavation execution procedures on the behavior of nailed-soil structures using the finite element Code Plaxis 2D, 2015. The load transfer behavior of grouted anchors in laterite under long-term (creep) loads were investigated by [PERSON] et al. [22] using laboratory and analytical models. The creep behavior on the grout-soil interface was represented using a Merchant rheological model. They observed that that the tensile force distribution in anchors tends to be linear, and that the shear stress distribution tends towards uniformity under long term conditions. It is evident from the literature review that there is no simple way to accurately predict the pullout behavior for all types of nails in different soil types. There are numerous parameters affecting the pullout response of soil nails, including variation in soil conditions, variation in stress situation and variation in nail shape. Moreover, many parameters will change due to nail installation with time. Therefore, further studies are clearly needed to investigate the pullout behavior for soil nail reinforcement in nailed soil systems. In the present study, the nail pullout tests were conducted to assess the pullout behavior of soil nail reinforcement in granular materials. The development of soil shear resistance at the reinforcement-soil interface, i.e., soil-reinforcement interaction, is investigated in this study. Similar laboratory models of reinforced soil systems on a scale of 1:10 were prepared. The construction sequence used in a full scale slope was precisely followed in the laboratory model.