# Pullout Behavior of Nail Reinforcement in Nailed Soil Slope
## 1 Introduction  
Soil nailing techniques are widely applied for the stabilization of slopes and excavations. The basic concept of reinforced-soil systems relies upon the transfer of resisting tensile force-generated nails into the soil through friction or adhesion mobilized at the inter-faces. The soil mass exerts the driving forces, i.e., lateral earth pressure on the weight of a potentially sliding soil mass while providing the nail bond resistance. The frictional interaction between the soil and nails restrains the soil movement during and after excavation. The pullout resistance and displacement performance of the reinforcement has significant effects on the safe and economic design of a reinforced-soil system [1]. The pullout resistance in a reinforced-soil system is influenced by many parameters, such as methods and construction processes, soil and nail properties, the interface roughness between soil and nails, and the geometry of the slope or excavation. Friction and adhesion at the interface between reinforcement and soil increases the stability by reducing the tensile strain in soil mass [2]. [PERSON] and [PERSON] [3] have presented the design of the soil nailing system for landslide prevention and mitigation. They have also reviewed the various aspects and constraints related to soil nailing. The resistance factors for LRFD of soil nail pullout limits state under different design scenarios of nailed soil structures, that differ in wall face batter, soil friction angle, nail ultimate bond strength, and surcharge live load, are analyzed and calibrated by [PERSON] and [PERSON] [4] using artificial neural network (ANN) models. The progressive pullout response of a soil nail in reinforced soil systems is examined analytically by [PERSON] et al. [5] They have considered the pullout process as three typical phase processes. The first is a pure elastic phase during which the nail-soil interfacefollows a linear elastic stress-displacement relationship, and then the elastic-plastic phase during which a transition point presents dividing the elastic and plastic zones and the final pure plastic phase. They have also performed a comprehensive parametric study to assess the effects of key factors, including length and diameter, length of plastic zone, and the elastic modulus of a soil nail, on the pullout resistance of a soil nail. The studies on the pullout behavior in soil nailing systems are due to [PERSON] et al. [6], [PERSON] et al. [7] and [PERSON] et al. [8] for various overburden pressure and conditions of soil dilation. The effect of rainfall infiltration on the behavior of soil nails in loose fill slopes is studied by [PERSON] et al. [9] [PERSON] et al. [10] have investigated through the experiments the soil-nail pullout interaction in loose fill materials. They have also simulated the pullout load-displacement relationship using a one-dimensional spring model. [PERSON] et al. [11] have developed the novel nail pullout test to predict the soil-nail interface shearing mechanisms using short nails embedded in expansive cohesive soils under varying degrees of saturation. The effect of nails and soil parameters, namely size, length and angle of nails and friction coefficient at interface, on the pullout force for grouted soil nails in sandy soil are investigated experimentally and numerically by [PERSON] et al. [12]. The accuracy of effective stress method (ESM) equations for the prediction of the ultimate bond strength of soil nails is assessed statistically by [PERSON] and [PERSON] [13] using the maximum likelihood method. Pullout behavior and the failure mechanisms of waste tire strip-reinforced sands are studied using the physical models by [PERSON] et al. [14] and they observed that the pullout resistance is initially provided by the front portion of the embedded tire strips and in the latter stages, more and more of the areas of the end portion of the tire strips are mobilized, giving a progressive failure mechanism.