Test Analysis for Uplift Coefficient of Post-grouting Bored Concrete Pile in Thick Sand Layers of Beijing Tongzhou District

This paper is based on the results of a field static load test on compression and uplift single piles in thick sand layers at Tongzhou district,Beijing.In this paper,each of three uplift and compression post-grouting of full length bored concrete piles from two test sites were selected.First,in order to obtain the shaft resistance curve of the each test pile,the field test data were processed.Second,compared the performance of shaft resistances between two types of piles under the ultimate load and then briefly analyzed the mechanical properties of uplift and compression piles in varies soil layers under increasing load.Third,the uplift coefficient of the soil layers was calculated by the ratio of the ultimate shaft resistance of the uplift and compression test piles.The range of the uplift coefficient of different soil layers and variation tendency varies in depth were discussed and analyzed in detail.It shows that the uplift coefficient ranges of the uplift piles in the two experimental sites are 0.34~0.67 and 0.31~0.63.The uplift coefficient range of soil layers above the middle of the test pile are 0.51~0.67 and 0.51~0.63.The uplift coefficient of soil layers near the lower-middle part of test piles are less than 0.5 in both test sites,due to insufficient performance of shaft resistance from surrounding soil layers.The results from this paper can provide the reference for design and theoretical research of uplift pile in thick sand layers of this area.