Study On The Soil Strength Reduction During Pile Driving In Offshore Engineering

With the development of offshore oil in to deep sea, the pile has been widelyused in the offshore platforms. As result of poor construction environment, pileinstallation become more difficult and the accident more frequent. In order to reduceeconomic loss, prediction of pile drivability is an essential link before pileconstruction. However, the soil structure around the pile is destructed and the strengthreduced, it become difficult to accurately determine the soil resistance to driving.Scholars at home and abroad through a series of experiments and theoretical analysisdiscuss this problem, due to the f the soil strength reduction affected by many otherfactors, there has been not a rigorous calculation method. To solve this problem, finiteelement method and wave equation method were used to study the process of piledriving.First of all, this paper discusses the pile driving process with the1-D stress wavetheory and pile-soil interaction model. For soil strength reduction, soil structure andeffective stress principle were explained. By comparing the measured data, find sandand clay in the strength reduction performance differently, also discusses the commonthe simulation method of soil strength reduction.Secondly, apply GRLWEAP to calculate actual the pile bearing capacity, basedon actual pile driving records, soil resistances were determined in sand and clay bywave equation back analysis method. Using least squares method make measuredvalue and calculated value numerical fitting and get sand and clay of soil strengthcalculation formula.Finally, finite element method-Plaxis was used to simulate pile driving process,discuss the influence of displacement, stress, strain and the excess pore water pressureas soil strength reduction degree varies. The result shows that due to the compactioneffect of the pile and the production of excess pore water pressure, soil stress andstrain state around pile will change. Along with the soil strength reduction degree andhammer blow increasing, excess pore water pressure, radial stress, radial strain andvertical strain will keep increasing, the vertical stress will decrease continuously...