Research On Grey Modeling And Prediction Of Ultimate Bearing Capacity Of Single Pile

Because of the rapid development of economy and society, single pile is more and more widely applied in the engineering, so whether ultimate bearing capacity of single pile can be determinied accurately is very important for the engineering. Static load test is the most reliable method to determine ultimate bearing capacity of single pile, however, its cost is large, and sometimes ultimate load of the test pile can not be rearched. Therefore, how to avoid the destructive test and predict ultimate bearing capacity of single pile according to the limited known information of pile has significant research value.Grey system theory is a kind of system science theory whose research object is uncertain systems with partially known and partially unknown information, and the load-settlement curve has the approximate grey exponential law and the settlement sequence is non-equidistance sequence, therefore, the settlement sequence and the load sequence were generally seen as time sequence and modeling sequence respectively, and then non-equidistance GM(1,1) model was established for the two sequences. However, the modeling and prediction accuracy of the non-equidistance GM(1,1) model sometimes is not high. Futhermore, in pile foundations, the parameters are not certain, and ultimate bearing capacity of single pile is influenced by many factors which are rather complicate. So, GM(1,N) model was generally considered for ultimate bearing capacity of single pile and the factors which affects it, but the prediction accuracy of the traditional GM(1,N) model may not meet the requirement. Therefore, on the basis of the previous research, this paper considers establishing several new grey models to research the modeling and prediction problem of ultimate bearing capacity of single pile. The main contents and results of this paper are as follows:Non-equidistance prediction model of single variable for ultimate bearing capacity of single pile is researched. Generalized non-equidistance GM(1,1) model is proposed, then according to the settlement sequence and load sequence, generalized non-equidistance GM(1,1) model is established, meanwhile, the relevant steps of forecasting ultimate bearing capacity of single pile is presented, and then ultimate bearing capacity of single pile is predicted according to the prediction steps. Besides, the affine properties of generalized non-equidistance GM(1,1) model are studied.Meanwhile, multivariable prediction model for ultimate bearing capacity of single pile is considered. The ultimate bearing capacity of single pile and the factors influencing it are considered as a system with multiple input and one output, in which the factors affecting the ultimate bearing capacity of single pile and the corresponding ultimate bearing capacity of single pile are viewed as input and output respectively. Generalized grey two stages GM(1,N) model and GMC(1,N) power model are put forward, moreover, in order to improve the model prediction accuracy, the algorithm steps of GMC(1,N) power model based on cluster analysis are given, then GMC(1,N) power model based on cluster analysis is considered to predict ultimate bearing capacity of single pile, in addition, the new models provide new thought for the multivariable prediction for ultimate bearing capacity of single pile.