Analysis Of The Settlement Based On Apile-raft Foundation Of One High-rise Building

With the current urbanized process accelerating,the high-rise building contain low-rise podium and large underground garage is also increasing.The foundation of high-rise building is always pile-raft foundation,podium and garage’s foundation is raft foundation.This type of foundation has been widely used owing to the high bearing capacity and the ability to control the deformation.But there are numerous problem of this type of foundation,such as the larger difference of settlement and internal force between high-rise and low-rise.At present,the design of this foundation is relying on experiences,so the deformation is difficult to calculate.Based on the existing settlement’s calculating methods and related research,this paper focuses on the analyze how does the resilience of soil and the upper structural stiffness affect the settlement of one project’s pile-raft foundation in Beijing with its data from monitor.This paper’s conclusion may provide reference for theoretical research and engineering design.The main contents are as follows:(1)Combined with the data of subsidence,this paper analyzes the cumulative settlement and a single settlement.And the results show that the process of subsidence of this structure is divided into two stages: the resilient stage of soil and the stage of normal consolidation;(2)Based on the five different models from PKPM,this paper analyzes the effect of the resilience of soil and upper structural stiffness on settlement’s calculation of this pile-raft foundation.The results show that the parameter of late poured band and the resilience of soil are the main factors influencing the calculation;when using the Winkler model,the value of calculation is about 2 to 4 times of the value of monitor;when using the Mindlin model,the results have a good agreement with the monitoring data;(3)The main reasons for the difference between the calculated results and the measured values in PKPM when calculating the settlement of pile-raft foundation are as follows: the model and theory are based on the theory of elasticity and revised by experiences;the interaction between piles and soil is neglected in the calculation;the consideration that one layer of soil at the end of pile is unrealistic;the share responsibility of raft is neglected in the calculation;the theory and method take into account the stiffness of the superstructure is not perfect;(4)The deformation and settlement of pile-raft foundation in this project is simulated in FLAC3 D,this paper analyzes the influence of two factors on the settlement and deformation above in the simulation.It is concluded that the effect of the resilience of the soil on the settlement of the raft foundation is obvious,and the influence on the settlement of the pile-raft foundation of the main building is negligible;while the upper structural stiffness has little effect on the final settlement,it mainly controls the relative deformation of the piled raft foundation;(5)Combined the calculation results from PKPM,FLAC3 D with the monitoring data,we found an characteristic of the result in PKPM and FLAC3 D is that,the settlement in the middle of pile-raft foundation is largest and diminishing from the middle to the outside;the difference between the high-rise and the podium is obvious.The main reason is that the structural load is loaded to the ground once,but the actual process is gradually loading;(6)In calculating large and complex foundation’s settlement,FLAC3 D has higher precision and accuracy,the characteristics of deformation are more clearly.It’s an important means to solve such problem in design.