Study On Numerical Simulation Of Load-bearing And Deformation Characteristics Of Group Pile Composite Foundation

The pile composite foundation can make full use of bearing potentiality of foudation soil body and enhanced body. How do the potential load-bearing capacity of pile and soil between piles mobilize depending on the rational layout of piles. How to determine pile spacing is the key problem of layout of piles. Determination of pile spacing has very important significance on the engineering design. Thus, based on the numerical simulation of load-bearing and deformation characteristics of group pile composite foundation in this paper, formation conditions of integrity problem of group pile composite foundation is studied and reasonable pile spacing considering the effect of pile-soil interaction is obtained.Firstly, based on the numerical simulation of load-bearing and deformation characteristics of CFG single pile composite foundation and CFG group pile composite foundation. According to the results, the settlement of single pile composite foundation is smaller than that of group pile composite foundation. The maximum axial stress of pile in single pile composite foundation is at the top of pile, but the maximum axial stress of pile in group pile composite foundation is under the top of pile. The additional stress in soil is mainly existed in the range of the effect of raft and decrease quickly along the depth direction, there is no stress concentration near the pile tip, while there is stress concentration near the pile tip in group pile composite foundation.Secondly, the numerical simulation of integrity problem of CFG pile composite foundation is simulated by changing the parameters of pile spacing, pile length, cushion thickness, soil property of pile end etc. Simulation results show that: Whether or not pile and soil between piles of CFG pile composite foundation can form a whole entity, that is concerned with pile length and pile spacing, when pile length is short, it requires a relatively small pile spacing, for example, when pile length is 5 meters, pile spacing is 3 times the pile diameter, so that pile and soil between piles can form a whole entity; when pile length is longer, bigger pile spacing can be chosen. for example, when pile length is 20 meters, even pile spacing is 5 times the pile diameter, pile and soil between piles also can form a whole entity.Viewing of improving the bearing capacity of soil between piles, the pile length is not the longer the better, there is an optimal length. Placing CFG pile tip on a good layer of soil can greatly improve the capacity, if want to continue to mobilize the bearing capacity of soil between piles, the design of cushion is particularly important.Finally, the numerical simulation of integrity problem of cement mixing pile composite foundation is simulated by changing the parameters of pile spacing, pile length, pile strength etc. Simulation results turn out that: when pile spacing less than 2 times the pile diameter, pile and soil between piles can form a whole entity, if continue to reducing pile spacing, it is not economical. Pile-soil stress ratio is non-linearly increasing as the load increasing, but it decrease after cement mixing pile yield. Before cement mixing pile yield, pile shared ratio increase as the load increase, while soil shared ratio decrease. Pile strength has significant impact on the settlement of composite foundation, but before pile yield, the pile-soil stress ratio, pile-soil load share ratio, pile stress concentration factor and pile-soil stress decrescence factor have little effect by pile strength.