A Numerical Study On Vertical Bearing Capacity Behavior Of Large-Diameter Bored Pile Groups

Along with the construction development in high-rise buildings and large bridges in china, large-diameter bored piles are widely used in these projects for their high bearing capacity and convenient construction. However, the studies of large-diameter bored piles principally focus on the analysis for the bearing behavior of single pile foundation, and the bearing character and pile group effect of pile group foundations have not been well understood. Therefore, the corresponding indepth research needs to be carried out. In this paper, the studies are emphasized on numerical methods for evaluating the bearing capacity behavior of large-diameter bored pile groups and its influencing factors under vertical loading. The main investigations consist of the following parts.1. Based on general-purpose finite element software ABAQUS, the three-dimensional finite element computational model of large-diameter bored single pile foundation under vertical loading is established. The vertical bearing capacity of large-diameter bored single pile foundation is evaluated by displacement-controlled method and the relation between vertical load and settlement is obtained. Moreover, the distribution of axial force and lateral resistance along the buried depth of pile and the compression of pile are discussed. At last, the comparative analysis of the vertical bearing capacity of large-diameter bored single pile foundations are made for different moduluses of lateral soil, moduluses of pile-tip soil, the cohesions of pile-tip soil, the friction angles of pile-tip soil and the pile diameters.2. The three-dimensional numerical analysis for evaluating the vertical bearing capacity of large diameter bored pile groups in different pile numbers, pile spaces and pile diameters is done in this paper. For the pile groups of different arrangement under vertical loading, the shaft resistance, the tip resistance, the load distribution, the displacement distribution and the plastic strain of soil are analyzed. The effect of pile number, pile space and pile diameter to the bearing behavior of pile groups is discussed. Comparing with subentry efficiency factors of pile groups in different circumstances, the impact extend of pile number, pile space and pile diameter to pile-group effect are analyzed.3. The effective length of large-diameter bored pile groups of different arrangement and single pile foundation under vertical loading is studied with the method of bearing capacity control. Relations between the vertical bearing capacity, the shaft resistance, tip resistance of piles and length of piles are acquired. The effect of pile number, pile space and the pile-group effect to the effective length of arge-diameter bored pile groups and the corresponding bearing capacity is discussed. Finally, the load share ratio of skin friction of piles under effective length is analyzed and through the bearing behavior the piles under effective length are found to be friction piles.