Nonlinear Finite Element Analysis Of Precast Piles For Piling Process

Driving piles process of precast piles is a nonlinear process, which influence is mainly from engineering geological conditions, design parameters of pile, machinery parameters of a pile driver and workmanship. This thesis models and analyzes driving piles process by using nonlinear finite element analysis software ABAQUS.For machinery parameters of a pile diver, it is this studies that of the hammer weight, drop high, hammer cushion and pile cushion etc effect on peck and duration of impact, maximum of compressive stress, maximum of tensile stress and degree of penetration.For design parameters of piles, this thesis analyzes mainly impact of pile type, pile diameter, pile length, pile material on piling process. Impedance of the pile body is introduced to analyze impact of material on piling process, and L/D is used to analyze impact of pile type, pile diameter, pile length on driving piles process.For engineering geological conditions, this thesis analyzes mainly impact of soil physical properties, mechanical properties and soil distribution on piling process. Pile-subsoil stiffness ratio is introduced to analyze impact of engineering geological conditions on degree of penetration, and selects appropriate construction process in accordance with soil characters.The main conclusions are as follows by simulating:(1) Duration of impact has something to do with the weight of hammer only, and has nothing with drop.(2) Drop and weight have an effect on maximum Mise stress, but the maximum Mise stress produced by drop is far greater than the maximum Mise stress produced by weight. Moreover, increased stress by increasing drop is far larger than weight (three times, more or less). Tensile stress of precast pile increases with increase of weight basically, but tensile stress changes little when weight is within1~2m, and it goes up faster when more than 2m.Increasing weight will not increase tensile stress of precast pile.(3)Peak of impact of pile head increases with increase of rigidity of pile cushion ; duration of impact decreases with increase of rigidity of pile cushion; setting pile cushion can absorb large amounts of deformation energy of pile body, thus decreases tensile stress of pile body , which effect decreases with increase of rigidity of pile cushion.The injection depth of pile increases rapidly with increase of rigidity of pile cushion, but when the rigidity of pile cushion is more than the rigidity of pile body , the effect will be little to the injection depth.(4) When the energy of hammering is the same, the vertical injection depth of single pile shows an increasing trend with increase of rigidity ratio of pile-subsoil. In order to be easier piling construction, rigidity ratio of pile-subsoil should be more than 200.Last, this thesis shows concrete application of conclusion through a project example. It is proved that the conclusion can be introduced to guide design of pile foundation, construction piling, and settlement of the problems in driving piles process.