Model Tests On Effects Of Spudcan Penetration And Extraction On Adjacent Piles

Jack-up is a kind of engineering ship which is widely used in offshore oil development.In many circumstance Jack-ups work next to a jacket platform.Owing to the effect causes by spudcan penetration on jacket platform pile foundation.At present,there are few model researches about spudcan –pile interaction in China.Small scaled model tests are carried out under 1g condition to investigate spudcan –pile interaction.The details are as follows:Spudcan penetration influences pile foundation by squeezing soil.In order to measure soil lateral displacement during the test and analyze soil-pile interaction,a soil lateral displacement measuring system which is based on angle sensor was developed.The results are compared with centrifuge test,and concluded similar regularity.During spudcan penetration,depth of maximum soil displacement is gradually increasing.During spudcan extraction,depth of maximum soil displacement is decreasing gradually.Results show than the soil displacement measuring system work well.Flexible piles are used ad adjacent piles in the test.In this thesis,pile head condition and the distance between the adjacent pile and spudcan are two factors studied in the test.In order to analyze the adjacent pile responses,pile moment,pile head displacement are measured and compared with centrifuge test results.We found that under different pile head condition,during penetration position of maximum pile bending moment goes down gradually and at the same penetration depth,positions of maximum pile bending moment are similar.We conclude that the pile head condition has little influence on pile expect for pile head,because under fixed pile head condition pile head suffered large bending moment.Under free pile head condition,there are some differences on bending moment between 1g test and centrifuge test.While under fixed pile condition bending moment of 1g test and centrifuge test are the same.After spudcan extraction pile still suffered relatively bigger bending moment.Through comparing the pile bending moment and the change of soil displacement,concluded that there is a connection between pile response and soil displacement.The depth of maximum bending moment and depth of maximum soil displacement are the same.Bigger soil displacement caused bigger bending moment.After spudcan extraction soil displacement did not decrease to zero.So the adjacent pile still suffered soil squeezing effect after spudcan extraction.