ارزیابی مقاومت بیرون کشش صندوقه های مکشی در خاک ماسه ای با استفاده از مدل فیزیکی

During the past two decades, suction caissons have become an increasingly viable alternative to traditional offshore foundation such as gravity based foundations and piles. The pull-out performance of conventional suction caissons (with upright walls) has been previously investigated by a number of researchers. However, less attention has been formerly paid to tapered suction caissons. This paper reports some results from an experimental investigation into the pull-out performance of tapered suction caissons. The 1g experiments have been carried out on eight small scale suction caissons. The aspect ratios, (length/diameter) have been 1, 2, 3 and 4 and the diameter has been constant and equal to 80 mm. Four specimens have had upright walls while the other four had a positive wall slope of 10%. The caissons have been installed in a soil tank containing very fine saturated silty sand. The caissons have then been subjected to vertical pull-out loads with different speeds. The effects of variations in soil density and pull-out rate on the pull-out capacities have also been investigated. In general, tapered caissons have been noticed to present enhanced pull-out capacities as compared to those from their equivalent upright caissons. The enhancement rate has been found to be more significant in suction caissons with higher aspect ratios. With both upright and tapered caissons the pull-out capacity increases by an increase in the pull-out rate. The pull-out rate effects are more significant with upright caissons in comparison to the corresponding tapered caissons. The density effects, however, are more significant with tapered caissons as compared to their equivalent upright caissons.