Research On Bearing Capacity And Calculation Method Of Laterally Loaded Pile Based On Piezocone Penetration Testing(CPTU)

With the development of infrastructure construction and the growth of urbanization process,it is a great challenge for the safety and durability of projects.The loads of undesirable soft soil foundation is widely distributed in Jiangsu Province,which is of low strength,easy compression,high water content,large pore ratio and does not satisfy the demands of engineering construction unless being treated.Because of the good stability,high bearing capacity and small uniform settlement,pile foundation have been widely used in foundation treatment.The lateral bearing characteristics evaluation,the core part of many projects,is complex which needs input parameters of soil strength,lateral resistance and lateral displacements around pile.It is difficult to obtain the in-situ physical and mechanical properties through laboratory tests because soft soil is hard to be sampled and horizontal static load test is of high accuracy but low efficiency.Piezocone Penetration Testing(CPTU),a new type of in-situ testing technology,which is of great conveniency for getting accurate soil in-situ engineering parameters,has great importance for research on lateral loaded piles'characteristics.Research on evaluation methods of laterally loaded piles' bearing characteristic were made throuth theoretical derivation,numerical analysis and in-situ tests(CPTU tests and horizontal static load tests).The main contents and conclusions are as follows:(1)Theoretical evaluation methods of laterally loaded piles' bearing characteristic based on in-situ tests were summarized at home and abroad and two aspects of p-y curves model were analyzed.Two types calculation methods of p-y curves model based on CPTU,rooted in Matlock and hyperbolic curve,were derived after forecasting the soil parameters with CPTU.Differences exist between two methods for calculating lateral limit soil resistance when it comes to different types of soil layers and the former was applied to cohesive soile while the latter was for cohesiveless soil.(2)The interaction betwwen soil and piles subjected to lateral loding was simulated by finite elements method.Comparative analyses were made between simulation results and theoretical derivation results.It is concluded the two methods are of different accuracy when they are used in different types of soils.(3)Section bending moments,lateral soil resistance,lateral deformation and p-y curves of tested piles were evaluated by horizontal static load tests.It can be learnt that the interaction between soil and pile subjected to lateral loading were mainly distributed in the upper soil layers.The type of CPTU p-y curves based on Matlock is more suitable for cohesive soils,and the type of CPTU p-y curves based on hyperbolic method performs better in predicting p-y curve in cohesiveless soils.