Experimental Study On Pile Group Effect Of A Tandem-Pile Structure In Multi-Directional Irregular Waves

With the development of marine industries like deep-water oil exploration,sea transportation and offshore wind power in recent years,marine engineering structures such as ocean platforms and cross-sea bridges have been widely developed.Small scale pile group is a common structure type in coastal engineering,and pile group effect should be considered when calculating wave forces on piles.The researches on pile group effect at home and abroad are mainly based on experiments at present.The experiment contents were mostly on isolated pile.Pile structures of limited experiments on pile group were simple,which contained only 2-3 piles.So researches on pile group effect are not thorough.And experiments before were mostly under the action of regular waves and uni-directional irregular waves,without the introduction of multi-directional irregular waves.As a result,in this paper,experimental study on the9-tandem-pile group structure under the action of regular waves,uni-directional irregular waves and multi-irregular waves is conducted.Firstly,features of pile group effect coefficient under the action of regular waves,uni-directional irregular waves and multi-irregular waves are studied combined with the wave force on isolated pile.This paper analyzes the change rules of pile group effect coefficients of inline force and transverse force with relative pile distance,and compared the difference of pile coefficient of different piles in pile group.The influence of parameter KC is also considered.And meanwhile,this paper defines inline force and transverse force coefficients K_GI,1/3 and K_GLI,1/3 under the action of multi-irregular waves,combining with the wave force on isolated pile in uni-directional irregular waves.And the relation between the coefficients and directional spreading of multi-directional irregular waves is analyzed,which shows further characteristics of the wave force under the action of multi-irregular waves.Secondly,the frequency domain characteristics of the wave force spectra of group piles and an isolated pile under the action of irregular waves are analyzed.The characteristics of inline force and transverse force are analyzed,and the characteristics of inline force and transverse force pile coefficient K_G,m0 and K_GL,m0 are studied.Lastly,compared with the results of pile group effect in 2-3 piles in former studies,characteristics of pile group effect are further discussed.