عنوان مقاله [English]
This paper describes a series of laboratory tests performed on geocell reinforced soil beds, with one and two layers of geocell and different heights of geocell under repeated loads (loading, unloading and re-loading), to simulate vehicle traffic loads. A soil surface settlement up to 20000 load repetitions was recorded, until its value became stable or failure occurred due to excessive settlement. The influence of the height of geocell layers, H, in terms of H/D (H: the height of geocell layers, and D: the loading surface diameter) and vertical spacing of the two geocell layers, and h, in terms of h/D, in the foundation bed, were studied. Assessment of performance is investigated for one and two layers of geocell, whereas the used mass of geocell material is kept constant. For example, the experiment reinforced by two layers of geocell with H/D=0.225 has exactly the same mass of geocell compared with the experiment reinforced by one thicker layer of geocell reinforcement with H/D=0.45. The results show that the settlement under repeated loads is the large portion of the settlement that occurs during the first few cycles of loading and unloading compared to the total settlement recorded after all cycles. The optimum vertical spacing of geocell layers was found to be approximately 0.2 times the loading plate diameter (i.e., h/D=0.2). For one layer reinforcement, with an increase in the height of the geocell, the settlement of the loading plate decreases. The reinforced bed with two layers of geocell has more efficiency than one layer of geocell in reducing the surface settlement, whereas the same mass of geocell was used in the foundation bed. For example, the maximum settlements of loading plate for the two layers of geocell-reinforced soil bed with H/D=0.225 (h/D= 0.2) and for one layer of geocell-reinforced soil bed with H/D=0.45, at the end of loading, are 36\% and 28\% of the loading plate diameter, respectively.