Research On Settlement Law Of Super-high-rise Pile-raft Structure Foundation In Longdong Region

Research on the laws of the pile raft foundation building subsidence is relatively mature in the eastern coastal soft soil area.However,in recent years,with the vigorous implementation of the “One Belt And One Road” strategy proposed by President xi,a series of large engineering such as high-speed railway and high-rise buildings have sprung up in front of the world.In all of these projects,there is a solid foundation,which is the full use of pile-raft foundations.It is widely used in practical engineering for its advantages s uch as pile length,deep burial,high bearing capacity,small settlement and good stability.For the Longdong region,which is the thickest in the yellow soil layer of the whole country and even the world,it is faced with all kinds of difficult problems w hether it is the preparation of the preliminary foundation plan or the follow-up project construction.To do this,The author is based on a super high-rise building in xifeng district,qingyang city,gansu province,The main contents are as follows :(1)Research of engineering geological characteristics of large thickness loess foundationA strong combination of laboratory and outdoor experiments,The physical properties and mechanical properties of typical loess in the site were analyzed comprehensively and the geological conditions were evaluated,The results show that the upper surface of malan loess is larger,the cohesion is smaller,the collapsibility coefficient is larger,and the compressibility is large.The porosity of the loess layer and the yellow soil layer in the lower part of the lower layer decreased,and the cohesion increased,the coefficient of collapsibility and compressibility decreased,and the stability increased.(2)Research on the site monitoring and settlement characteristics of super-high-rise piles and soil in construction stageThrough the pile arrangement of concrete strain gauge,the bottom of the pile caps of pile arrangement between earth pressure box,using the data collected,such as temperature,resistance,stress,strain and so on,calculating mainly for construction stage axial force of pile,pile side friction and the basic parameters such as soil pressure and analysises overall security on structure.(3)Study on comparison and analysis of settlement theory calculation of pile raft foundation in longdong areaUsing the method of generation of entity such deep foundation and standard method,simplified stress adjustment method and compressed domain decomposition method and so on the many kinds of settlement calculation method for tall building subsidence loess region trial,and compared with the measured values analysis,suitable for the region and was a kind o f ideal settlement calculation method.(4)Comparative analysis and research of settlement and deformation of pile raft foundation by finite element analysisIn the subsidence theory,on the basis of ABAQUS finite element software was used to numerical simulation analysis,further to the settlement of pile raft foundation,strain and displacement and other parameters and actual values,the theoretical value,this article verify the validity of the numerical simulation.(5)Prediction of settlement of super-high-rise pile raft foundation in Longdong large thickness loess areaBy means of Origin software,numerical analysis method and poisson curve method,the settlement of construction and post-construction is predicted in advance.Through this experimental research,it not only guarantees the safety of the construction stage,but also provides a warning for the series of unsafe conditions such as uneven settlement or excessive settlement of such buildings in the future.In the future,we can optimize the d esign of pile foundation and develop pile foundation theory.