A Shaking Table Experimental Study On Liquefaction Resistance Of Multi-pile Composite Foundation

:Multi-pile composite foundation is a new concept of composite foundation appeared in recent years in civilengineering. When used to treat liquefaction of natural ground, the liquefaction resistance of the multi-pile composite foundation stays a problem in discipline of geotechnical engineering since lack of investigations and research of seismic damage. To study the liquefaction resistance of the multi-pile composite foundation, a laminar shear model box and a shaking table have been designed and developed. Centering on the shaking table test of the multi-pile composite foundation, the following works have been done during this research:(1) Based on the model boxes used in the shaking table test on seismic geotechnical problems at present both here and abroad, as well as according to the purpose of this research, a laminar shear box has been designed and developed. At the same time, some devices have been developed to work with the laminar box, such as the platform and the foundation of the shaking table, supporting system of the platform and the lateral guidancesystem. Working with the existing MTS testing system, a simple unidirectional exclusive shaking table testing system has been successfully developed.(2) The basic physical and mechanicalindices of sand used in the shaking table test are obtained by routine laboratory tests, as results of the routine laboratory tests shown, the sand is confirmed to be the silty-fine sand. In addition, the liquefaction resistance curves of sand and excess pore water pressure time history curves are acquired by performing the dynamic tri-axial tests.(3) By using the shaking table testing system, the saturated ground tests have been successfully accomplished. The following conclusions have been drawn:①The shear box has successfully simulated the free boundary of the natural ground.②The method of preparing the model groundprove to be useful to get a uniform ground.③The increase of the excess pore water pressure of the model base is augmenting with depth. The excess pore water pressure of shallow layer keeps constant while the dissipation starts from deep layer.(4) A series of the multi-pile composite foundation tests have been conducted on the simple unidirectional exclusive shaking table by using the laminar shear box. The following conclusions have been drawn:①The multi-pile composite foundation is effective in distributing earthquake shear stress, the stone column and the CFG pile bear the shear stress in the ground soil.②The multi-pile composite foundation has an effective function in resisting liquefaction since the drainage of the stone column.③The liquefaction resistance of the multi-pile composite foundation is a coupling effect of distributing earthquake shear stress of the piles and drainage of the stone column.