Field Test Of The Compressive Bearing Capacity Of Rotary Bored Pile

According to the analysis of urban distribution in China,most of them develop along rivers and belong to the low level terraces in topography and landform,and most buildings are built on such low level terraces.Pile foundation has been widely used.These piles tend to be shorter in length,The stratum in which the pile is located is more fixed.Throughout the research results at home and abroad,most of them are focused on the large diameter long pile,and there are few researches on the short pile of such low terrace.Based on the Gangu Fuze Huating project and Jingning Runjia International project,this paper analyzes and studies the bearing capacity of short piles on the lower terrace.(1)The static load test method of anchor pile was used to test the bearing capacity of single pile for the phase I project of Gangu Fuze Huating,and the measured pile length was 10.0-10.3m.According to the Q-s curve and s-lgt curve,the deformation characteristics of four piles under different pile top loads are analyzed,and the limit value and characteristic value of pile compressive bearing capacity are studied.(2)For the three test piles of Runjia International Project,during the construction of the pile foundation,the balanced position of the test pile was estimated first and load boxes were buried.The balanced position of the test pile was at 4.0m and load boxes were placed in advance.The self-balancing method was adopted in the test,and the test pile length was 23.0m.The ultimate bearing capacity and characteristic value of the pile are obtained by interpolation method according to the displacement of the upper and lower piles under different loads.(3)In the above two tests,in order to test the distribution of the end resistance of the pile end soil layer and the side resistance of the surrounding soil layer along the pile body,two vibrating string reinforcement stress meters were symmetrically embedded in the section of each test pile at the change of the pile body stratum to test the axial force of the pile body under different loads.Based on the axial force,the lateral resistance of different soil layers and the end resistance of pile tip are calculated.When the bearing capacity reaches the limit,it is considered that the lateral resistance of pile and the end resistance of pile tip both reach the limit value and are taken as the ultimate lateral resistance and end resistance of soil layer.(4)In the Technical Specification for Building Pile Foundation JGJ94-2008,the calculation parameters and calculation formulas of pile foundation bearing capacity are recommended,and these formulas and calculation parameters are used to calculate the bearing capacity of 7 piles in the above two projects.By comparing the ultimate bearing capacity of the piles of the two projects,the bearing capacity of the piles of the two projects obtained by comparing the bearing capacity of the piles of the two projects with that obtained by the standard calculation method,and the ultimate lateral friction resistance and ultimate end resistance measured by the reinforcement stress meter,the factors that should be considered in the calculation of pile bearing capacity under different working conditions are obtained.