| At present,there are a large number of pile defects in practice of pile foundation project.Defective piles are major safety risks for the engineering safety.Integrity of piles are classified with the corresponding theory and specifications.It is still a lack of study on how the first ? pile or even the first piles should be used.Based on the pile foundation engineering construction and testing project the author joined in,the pile defect governance issues appearing in Nanning project are experimented.First of all,in this paper,it has carried on the full study on the theory,test and strengthening methods of defective piles.Based on the analysis of the existing group of pile and composite foundation theory,it is to study the load distribution rules of steel pipe-pile body concrete grouting.Secondly,the complete model pile,the defect model and defect pile reinforcement model have been produced indoors.And it has been designe d for 13 experiment methods to test,including the basic properties of m aterial test,integrity test of pile,and pile body strength test model Studyha s been carried out on the load distribution on pile top beneath cap,on the basis of considering the pile body-steel pipe-add solid three factors.The paper draws the main conclusions as follows:The integrity of pile body has been basically restored after the defective piles have a steel pipe-grouting reinforcement;The increase of the number of steel pipe basically are not affect the pile integrity.2.The strength of pile body has been basically restored(achieve complete pile strength of 80%?110%)after the defective piles have a steel pipe-grouting reinforcement.The failure modes of pile body are the same with integrity piles,but due to stress concentration,it makes the deformation of pile body damage reduced.3.The defects of pile reinforcement of reinforced steel pipe quantity has a"number effect",within the optimal steel pipe quantity,the increase of the quantity of steel tube can improve the strength of pile body effectively;In the condition of same number steel pipe,defect location moving down and increasing the length of steel tube can slightly improve the strength of pile body.4.The increases of steel pipe quantity can reduce the load sharing ratio of pile body concrete and defect parts net pulp add solid and increase the load sharing ratio of steel pipe-net pulp add solid;While after the number of steel pipe reaching "optimal",the load sharing ratio of pile body concrete,defect parts net pulp add solid and steel pipe-net pulp add solid tend to be stable;In the condition of same number steel pipe,defect location moving down and increasing the length of steel tube can reduce the load sharing ratio of pile body concrete and defect parts net pulp add solid and increase the load sharing ratio of steel pipe-net pulp add solid;In the same state,the load sharing ratio of defect parts net pulp add solid is less than the load sharing ratio of the pile top and pile body concrete.5.With the optimal steel pipe quantity,the increase of side-piling steel tube quantity can increases the total load sharing ratio of side-piling steel tube-grouting add solid group,but the load sharing ratio of the single pile in add solid group is almost invariant;The load sharing ratio of the single pile(middle-pile)in the steel pipe pile group is less than the single steel pipe pile(middle-pile).Summarizing the analysis of the above conclusions,using steel pipe-grouting reinforcement method to add.defective piles can effectively improve completeness of pile body and restore strength of pile body.Because of the number "effect" of reinforcing steel pipe,in engineering application,it is necessary to have indoor experimental research before the reinforcement design in defect,while combining with engineering hydrogeological conditions and the rock and soil environment around pile.Choosing the quantity of reinforcing steel pipe,and avoiding center cloth pile and uniform cloth piles as far as possible can achieve the most effective use of defective piles. |
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