Prediction of single pile settlement based on inverse analysis

An inverse analysis technique which is firmly based on non-linear regression method has been adopted to estimate Young's modulus of layered ground using the pile settlement model proposed by Poulos and Davis (1980). This is purely an elastic model, therefore no slip between soil and pile could be taken into account. In this method, not only mean value but also uncertainty involved in it can be quantified. Furthermore, a prediction procedure based on the First Order Second Moment (FOSM) method is also proposed. Two sets of bored pile loading test data consisting of pile top settlement and load distribution along pile shafts at various loading stages from the Bangkok area are analysed. It is found that more reliable estimation of parameters is possible if they (i.e. Young's modulus of each layer) are estimated based on several pile loading test results which have been conducted in a variety of geological settings and pile configurations. However, the prediction may not directly reflect accuracy of the estimated results, i.e. good prediction can be obtained if the geological conditions and the pile configurations are not very much different from the ones used in the estimation. On the other hand, erroneous prediction could result if these conditions are very much different. All these outcomes are explained based on data structure of pile loading tests which exhibit the multicollinearity.