Pullout characteristics and conceptual model of gabion reinforcement

The reinforced gabion wall on the west line of Xiangtan to Hengyang highway in Hunan province was studied with the large scale pullout model tests and numerical simulations to obtain the interface friction characteristics between the double twisted hexagonal gabion mesh(2.2 mm and 2.7 mm respectively) and red sandstone. The experimental results showed that the pullout displacement-shear stress curve could be roughly divided into 3 sections：the rapid growth，the steady progression and the yielding sections. The thinner gabion mesh led to the higher peak shear stress，larger cohesion and friction angle under the same normal stress. The pullout displacement-shear stress curve from the numerical simulation had two sections，namely，the rapid growth of shear stress and the yielding of gabion mesh. Under the same conditions，the 2.2 mm meshes resulted in the larger drawing coefficient and pseudo-friction coefficient and thus presented the better interface friction properties. The conceptual model suggested that the proportion of pullout force shared by the horizontal bars and longitudinal bars relied on the magnitude，the length，the coefficient of earth pressure and the friction factor，etc. The pullout bearing resistance on the transversal bars(T1) comprises the largest proportion of the total resistance (about 62%–72%)，on the other hand，the proportions of the annular pullout friction on the longitudinal bars(T2) and the interface friction acting on the surfaces of all nodes(T3) both grow against T1 when the normal stress increases.