Research On Bearing Behavior Of Concrete-cored Rubberired Cement-soil Pile Composite Ground

Stiff-core cement-soil pile composite foundation refers to the composite foundation which is formed by mixing piles formed in cement soil and pressed into high-strength piles,and then hardened.This new type of foundation treatment method bears the upper load by the inner core pile(steel pile or concrete pile),the outer core cement soil pile and the soil around the pile.After adding core material,the bearing capacity and economic cost of the composite foundation are improved.Stiff-core cement-soil pile can improve the soil quality.But in the engineering,it also gradually exposed its own shortcomings:first,the composite pile shows a strong brittle failure when bearing;second,the composite pile in the foundation soil is vulnerable to soil erosion.In order to solve the above two problems as much as possible,we add rubber powder with strong plastic deformation and good corrosion 'resistance to the cement soil of outer core pile,forming a new composite material rubber cement soil(RCS for short).Then,in order to further improve the bearing capacity of composite foundation,the common equal diameter piles are replaced by wedge piles.The wedge-shaped pile depends on its wedge angle to increase the friction between pile and soil,so as to further improve the bearing capacity.By combining the wedge-shaped concrete pile with the rubber cement soil pile,the concrete wedge-shaped rubber cement soil pile,namely the wedge-shaped core RCS pile,is formed.In this paper,the bearing capacity of RCS pile with wedge-shaped core is analyzed by theoretical research and finite element simulation,and the single pile and group pile are analyzed by ABAQUS finite element simulation.By changing the parameters of rubber powder content,wedge angle of core pile and length of inner core under a single pile,as well as the pile distance,number of piles,core length ratio,rubber powder content of outer core pile and wedge angle of inner core pile under a pile group,the simulation study is carried out,and the influence of single pile and group pile bearing performance under different factors is analyzed.The following conclusions and results are obtained:Through ABAQUS numerical simulation,the load settlement,pile-soil friction resistance,stress of inner and outer core and load sharing of wedge-core RCS pile composite foundation with load variation are studied in this paper.By changing the wedge angle and core length ratio of wedge-shaped core RCS piles,the paper observes the changes of side friction resistance,P-S curve and stress of wedge-shaped core composite piles under different conditions of single pile and group pile composite foundation.It is obtained that the bearing capacity of wedge-shaped core RCS piles will not increase endlessly with the increase of wedge angle and core length ratio of wedge-shaped core piles.There is a reasonable optimum value for both factors.If this value is exceeded,the increase of wedge angle of core pile and core length ratio will have little effect on the increase of bearing capacity of wedge-core RCS piles.Comparing the bearing capacity of different pile body material piles,the paper finds that the bearing capacity of wedge-core RCS piles is lower than that of concrete piles but much higher than that of cement-soil piles.The theoretical analysis shows that wedge-core RCS piles not only have good bearing performance reliability,but also reasonable preparation cost.The influence of different rubber powder content on bearing capacity of wedge-core RCS pile single pile and pile group composite foundation studied in this paper is analyzed.It is found that the deformation effect of single pile and pile group under single pile and pile group is improved by increasing rubber powder content,and the stress ratio between inner and outer core piles is adjusted continuously,thus the stress and deformation performance of each component in composite pile body can be better exerted.By changing the number and spacing of wedge-core RCS piles,the influence of pile group effect on bearing capacity of single pile and pile group composite foundation is analyzed.It is found that the increase of number and spacing of piles deepens the overall settlement of pile group and increases the stress and deformation of pile and soil.With the increase of pile spacing,the influence of pile group effect on composite foundation decreases graduallyThe bearing capacity of wedge-core RCS piles and the calculation of displacement and settlement of pile body are analyzed according to the theory of soil support,and the calculation method of settlement of wedge-core RCS piles is analyzed according to relevant codes and section recurrence method.