DEFORMATION CHARACTERISTICS AND INFLUENCE FACTORS OF THE CIRCULAR GEOSYNTHETICS-REINFORCED PROTECTION WALLS LOCATED AROUND OIL TANK

Abstract

The reinforced protecting wall is a composite structure located around the oil tank. It is consisted of three parts which are the backfill soil, reinforcements arranged in the soil and geogrid panels respectively. The reinforced protecting wall has received very few attentions of researchers. Related researches haven't taken the influence of spatial character on the reinforced protecting wall into consideration. As a result, its theoretical researches lag behind its engineering application currently. Due to the fact that the circular geosynthetics-reinforced protection walls cannot ignore the influence of its space characteristics, the numerical analysis is carried out with Plaxis3D finite element software. The reinforced concrete protection wall and the reinforced concrete dome are simulated with the slab unit. The geotextiles are made of geosynthetics. In order to better simulate the actual working conditions, interface units are set up at the interfaces of soil, concrete and geotextiles. The tank body is simulated with the plate element, and the oil in the tank is simulated by the entity unit. Because the tank and internal fuel use entity modeling, the interaction between soil and superstructure can be considered, and the rationality and accuracy of numerical simulation can be improved. The deformation characteristics of circular geosynthetics-reinforced protection walls located around oil tank and mechanical characteristics of reinforced materials are investigated with developing a three-dimensional numerical model. The model uses the hardening soil model with small-stain stiffness(HSS models) as reinforced soil constitutive model. By changing geosynthetics-reinforced protection wall height, thickness, gradient of wall space, geogrid stiffness and reinforcement spacing, the effects of these factors on the wall deformation characteristics are explored. This paper conducts a detail study on the influence of the size of reinforced protecting wall on the serviceability limit state. The study is composed of deformation behavior, the foundation settlement, and the distribution of strains and tensile in the reinforcement. According to the above analysis, this paper puts forward some suggestions to optimize shape and size of reinforced protecting wall. The results show that the wall lateral displacement decreases with the decrease in the wall thickness, height and gradient of wall space. Also, too small wall thickness and too large reinforcement spacing can lead to the increase of the overturning trend of protection wall, and smaller stiffness of geogrid results in excessive lateral displacement of wall. Thus, these parameters should be taken into account in practice. The construction of reinforced wall can increase the settlement of foundation on the edge of storage tank. The loading state of the fuel in the storage tank does not affect the settlement of the reinforced protective wall foundation. However, the maximum settlement difference of the tank foundation decreases with the increase of fuel oil in the storage tank. Further, the potential failure surface of the geosynthetics-reinforced protection walls according to the position of maximum tensile stress of geogrid is a curve going through wall toe. The soil pressure behind the wall is greatly affected by the wall gradient. So the gradient should be considered when choosing a appropriate design method.