Study On Bearing Properties Of Steel Pipe Piles With Lrage-diameter Of Offshore Wind Farms Foundation Under Vertical Load

The long and large-dimater steel pipe piles have been widely used in ocean engineering and high-rise building due to its higher bearing capacity, good ability of anti bend, smaller amount of dumping and relatively simple pile driving process. However, due to the high cost of testing large-diameter steel pipe piles,less research data led to the current lack of vertical bearing capacity of big diameter steel pipe pile,which making the design and construction with great inconvenience and waste. So,researching bearing characteristics of long and large-diameter steel pipe piles has great theoretical and practical significance.The main idea of this paper are as follows:Firstly, from the static load test data collected from four marine engineering, the bearing capacity of large and large-diameter steel pipe piles were analysed, then the bearing mechanism of large and large-diameter steel pipe piles were studied and load settlement curve and lateral friction curve were given.Secondly, based on the bearing properties of large-diameter steel pipe piles. The correction coefficient of plugging effect was put forward aiming at the pile end resistance,and then verified end resistance and shear resistance by the result from static loading test.At last, The vertical capacity of steel pipe pile with large diameter with plugging effect and size effect were studied.In this paper, the main conclusions are as follows:The influence coefficient of soil plug for steel pipe piles whose diameter is greater than 1.5m is very large, which generally in the range of 0.2?0.3, so the proposed specification revision were introduced that for those the diameter is larger than 1.5m, ?p were range from 0.2 to 0.3.When calculating standard value of shear frictional resistance of pile by using criterion, we found that the calculating value were smaller than pratical ones by 10% to 20%, this is because of the deeper soil,the larger soil stress,thus leading to larger friction resistance. However, The calculated value is less than the measured ones, which is safe for the design,so it is reasonabile of using the method proposed in this dissertation.