Numerical simulation method for soil strength reduction during pile driving in offshore engineering

In offshore engineering, the diverse and complicated construction conditions make pile driving more complex and difficult, which usually leads to refusing hammer and pile run during piling projects. Hence, it is crucial to predict the drivability of piles and to estimate the hammer blow counts accurately. In the continuous pile driving, since the soil around the piles is remolded heavily, the soil strength reduction and the frictional resistance decrease obviously. The calculated blow counts are usually much more than the measured data for continuously piling procedure. Four kinds of methods which can consider the soil strength reduction during pile driving analysis are compared. The methods include the linear formula method, nonlinear formula method, exponent formula method and stress history method. Since they all can not consider the effect of soil properties on soil resistance surrounding piles, a novel method is proposed. Based on the one-dimensional stress wave theory and the pile-soil interaction model, the proposed method estimates the soil resistance using the GRLWEAP software by using different restitution factors in different soil layers. The proposed method is verified by comparing the calculated results with the in-situ records of a practical project.