Research On Cushion Of Rigid-pile Composite Foundation

Composite foundation with rigid piles is formed from rigid pile、soil between piles andbedding cushion，but the key technology of the rigid pile composite foundation is beddingcushion.Bedding cushion have the ability to ensures piles and soil to share the load、toadjusts the pile-soil load sharing ratio、to adjusts piles and soil to share the horizontal load、to reduces basement stress concentration phenomenon and to adjusts the overall foundationsettlement and deformation. At present the theoretical research about the mattress layerlags behind engineering practice, so that the thickness and modulus of cushion in designand construction are set according to engineering experience. Therefore, research on the setof the cushion in composite foundation with rigid piles is very necessary now.Based on the existing research results, this article analyzed the mechanism of thecushion、the Failure mode based on different thickness of the cushion, Using the finiteelement software FLAC3D,with four factors（the modulus of the soil、pile diameter、thickness of the cushion、modulus of the cushion）,we did a numerical analysis on theirimpact on the pile-soil stress ratio. This article pointed out the limitations of therecommended value of the thickness of the cushion in the Specification, the thickness ofthe cushion should be different under different geological conditions. Proposed that ratiobetween the thickness of cushion and the pile diameter should be taken as the standardmeasure of pile-soil stress ratio. Recommended that the modulus of materials in cushionvary from40to60MPa. The pile diameter should vary from400mm to600mm, which ismost beneficial to cushion maximize its function and achieve the goal of economic andsecurity at the same time. In addition, according to the results of numerical analysis, thispaper also gives optimization ideas on the design and construction of rigid pile compositefoundation.