Study On Settlement Test And Prediction Method Of Long And Short Pile Composite Foundation

With the development ofbuildings in the direction of high level and deep base,requirements of their foundations resistant to the deformation are getting higher and higher,so leading to the occurrence of long and short pile composite foundation treatment technology in the engineering practice.The long and short pile composite foundation can give full play to characteristics of the pile and soil,and serve purpose to control the settlement and improve the safety factor.However,more and more complex methods for the pile foundation treatment make the safety problems caused by the settlement more serious than ever.Therefore,it is necessary to study the long and short pile composite foundation in depth.In this work,the study is firstly referred tothe settlement deformation and bearing capacity of long and short pile composite foundation.Then,a comparative analysisamong various calculation methods is presented for the settlement of long and short pile composite foundation.Finally,the GA-SVM model is used to predict the settlement of long and short pile composite foundation.The main research contents and achievements are as follows:(1)Through the indoor experiment model,influence of the pile length,pile diameter and cushion thickness on the settlement and deformation is investigated,which indicates the variation law of settlement with the long and short pile composite foundation.The results show that a significant effect can be seen tocontrolthe foundation settlement by increasing the length of long pile,the length of short pile,and the pile diameter,or by decreasing the cushion thickness.(2)Stress characteristics of the long and short pile composite foundation are obtainedthrough the analysis of the pile stress,the pile-soil stress ratio and the underlayer stress in the long and short pile composite foundation.The results show that the stress of the pile has a peak,where the pile stress is the largest,the pile-soil stress ratio toward the top of the pile increases first and then decreases,while toward thebottom of the pile it increases gradually,and the pile stress in the underlayer is greater than the stressin its surrounding soil.(3)An analysis for thesettlement calculation of the long and short pile composite foundation by different methods is presented on the basis of a given engineering example,and the calculated values of the settlement from them are compared with the measured data.The results show that the calculation from the equivalent natural foundation gives values of thesettlement in agreement with the given case,and the weighted modulus method obtains thesettlement values with largeerrors,even though its calculation is relativelysimple.(4)The GA-SVM prediction model is used to predicting the settlement of long and short pile composite foundation.The results show that the GA-SVM performs a good prediction degree for the settlement of long and short pile composite foundation,with small errors between the prediction results and the field measurement data.The proposed GA-SVM model in the work has a good prediction accuracy and capability for the settlement prediction of long and short pile composite foundation,which provides a useful guideline for the safety prediction of the geotechnical engineering.