| Steel pipe Pile foundation is widely used in marine engineering because of its high bearing capacity,small settlement,good stability and strong adaptability.In recent years,with the development of China’s marine resources to the deep sea area,the offshore steel pipe pile foundation is developing towards the direction of large diameter,super long,deep penetration and large bearing capacity.As a result,the soil strength decline caused by the disturbance around the pile is significantly different from that of the small diameter steel pipe pile.In order to further clarify the characteristics and laws of soil strength decline around large diameter steel pipe pile during driving,based on onedimensional wave equation theory,numerical analysis and model test methods are used to study this problem,and the research results are verified by engineering examples.The main contents are as follows:1.The drivability of large diameter steel pipe pile in practical engineering was analyzed by using pile driving analysis software GRLWEAP,and the common calculation methods of soil resistance at pile side are compared and analyzed.It was found that the method to determine soil resistance based on site standard penetration test parameters is the most accurate.2.This paper revealed the attenuation law of soil strength around large diameter steel pipe pile in the process of continuous pile driving.By comparing with the actual pile driving records,it was proposed that soil properties and depth have influence on the weakening of soil strength.In order to more accurately simulate the weakening law of soil strength,two factors should be comprehensively considered in pile driving analysis.3.The ring shear test with high shear rate was carried out to simulate the weakening process of soil strength caused by continuous shear of surrounding soil during pile driving.The relationship curves of shear stress and shear displacement under different normal stress were obtained,and the weakening law of soil strength was revealed.Based on the test results and the driving example of large diameter steel pipe pile,the calculation method of soil strength weakening around the pile was proposed.4.A small indoor pile driver was developed,and the indoor pile driving model test was carried out.Through the analysis of the test results,the influence of the soil in the steel pipe pile on the side friction of the pile in the process of pile driving was studied,and the reason why the weakening degree of the soil resistance around the super large diameter steel pipe pile is obviously greater than that of the small diameter steel pipe pile in the process of pile driving was clarified. |
