Experimental investigation of effective parameters on lateral resistance of single piles

Assessment of bearing capacity of single pile under lateral loading has been always an attractive matter for engineers. Piles are usually subjected to moment, vertical, and horizontal loads. The Lateral loads are including wind, earthquakes, ship decking, earth pressure, wave, and ice thrust. The behavior of laterally loaded single pile is complicated and still is a useful research area. There are a lot of parameters which affect on pile behavior under lateral loading. One of these important factors is cross section shape of pile. When a pile is subjected to lateral loading, the passive force performed in front of the pile, has an important role on lateral resistance of pile which is exactly related to cross section shape of pile. Physical modeling is a reliable approach in geotechnical engineering to take into account all of these factors simultaneously. In this experimental study the effect of cross sections shapes of pile on single pile behavior under lateral loading in sandy soil were assessed. Four different cross sections shapes of pile which are commonly used in real projects were employed. These pile shapes were including: H pile, and closed-end square, pipe, and fin piles. In concept of optimum design the surface areas of all different cross sections shapes of piles were considered to be the same but with comparative moment inertias. In this condition the amount of material used for pile construction was the same for all different pile shapes used in this study and thus it was possible to comparison the results and find the best pile shape in any conditions. The lateral resistances of these single piles were investigated in different conditions such as different soil relative densities including 35, 65, and 85 % corresponds to loose, medium dense, and dense sand and different embedment pile lengths including 250, 500, and 980 mm corresponds to short rigid, intermediate, and long flexible piles. Results revealed that the ratios of lateral bearing capacity of short rigid H pile, square pile and fin pile to that of pipe pile in loose sand were 0.82, 1.21, and 1.43 respectively. The lateral resistances of single short rigid piles in medium dense sand were about 150 to 155% (152 % in average) higher than loose sand and they were in dense sand about 335 to 356 % (348 % in average) greater than loose sand for different pile shapes. When the soil relative density changed from loose state to medium state the lateral resistance of single piles were about 74 % higher in comparison to the case which soil relative density changed from medium state to dense state. The increase in lateral resistance of H pile in dense sand in comparison to loose sand was higher than fin pile, pipe pile and square pile by about 2, 10, and 22 % respectively. The lateral bearing capacity of long flexible piles and intermediate piles with different pile shapes in dense sand was respectively by about 290 % and 179 % greater than short rigid piles. The efficiency of fins in long flexible fin pile on improvement of lateral bearing capacity was lower in comparison to short rigid fin pile.