A Study Of Compound Foundation Characteristic Of Reinforced Mixing Pile

The concrete core mixing pile is a new soil improvement method. It means that, a concrete core is plugged into cement-soil mixing pile. Concrete core pile and the cement-soil mixing pile undertake together vertical load. It appropriately combines the advantages of the precast concrete pile with the cement-soil mixing pile. The cement-soil mixing pile with concrete core forms a new reasonable structure of pile; it means that, the strength of core pile is stronger than the strength of round pile; therefore, the cement-soil mixing pile with concrete core takes advantage of property of concrete core pile and cement-soil mixing pile. This paper makes a thoroughly study on the behavior of the concrete core mixing pile in vertical loading with 3-D finite element method by ANSYS software. The different core pile length, the different area replacing ratio, the different elastic module of cement-soil and the different elastic module of soil is deeply analyzed by finite element program. We get the Q-S curve, the pile top settlement curve, the displacement of pile body curve, the stress of pile curve,the pile top sharing load ratio of the pile curve and the side friction force of the pile curve by finite element program. Through which, the features of load transferring and deformation mechanism are deeply analyzed, it is expressed that the core pile shaft friction undertakes the mass of vertical load of the pile and a little of it can transmit to pile top, it is also founded that an optimum core pile length and an area replacing ratio of the reinforced mixing pile had been exited. Comparing the reinforced mixing pile with the concrete pile under the same condition, it is founded that the working behavior of the reinforced mixing single pile is similar to that of the concrete single pile, and, the concrete pile can be taken the place by the reinforced mixing pile under a certain condition. And in this paper, the different seismic response analysis in time domain is performed with 3-D finite element method by ANSYS software, taking into account of the interaction among pile-soil-superstructure. The differences between compound foundation of the concrete core mixing pile and pile foundation in seismic response are analyzed. Some parameters influencing the anti-seismic behavior of compound foundation of concrete core mixing pile are studied. The results show that, the maximum moment and shear of concrete core mixing pile are greater than pile foundation's under the same seismic response; The maximum moment of concrete core mixing pile lies in the (0.2～0.4)L,the greater the concrete core pile and the greater the area replacing ratio ,the bigger the largest moment ;The effect degree of area replacing ratio on moment and shear is greater than concrete core pile's, the elastic module of cement-soil's is slight. Then, it also introduces precisely working behaviors of the concrete core mixing pile groups under vertical static loading and seismic level loading; some methods of pile groups design are also introduced.