12.4.4 Conclusions
Hydraulic–pneumatic pile driving hammer can effectively achieve the impact of
large diameter and tonnage piles. The falling speed and strike energy of the
hydraulic hammer depend on the parameters of the low-pressure accumulator and
the diameter and length of the oil return pipeline. The shorter the length of the
return pipe and the larger the diameter are, the greater the strike energy of the
hydraulic hammer is. Low-pressure accumulator can quickly absorb the hydraulic
oil discharged from the hydraulic hammer, so that the hydraulic hammer drops
rapidly, thereby improving the strike energy of the hydraulic hammer.
12.5 Contact Model Pile and Soil
Pneumatic–hydraulic hammer uses the combined action of weight of hammer and
pneumatic–hydraulic pressure to achieve the impact of hammer and pile and penetrate the pile into the soil. This section mainly analyzes the impact process of
hammer and pile, and the contact between pile and soil after impact. The mathematical model of pile-soil contact process is established by software ANSYS, and
the distribution of displacement, stress, shear force and strain in pile-soil contact is
obtained by simulation calculation. The comparison between theoretical results and
field application shows that the proposed theory and method can well explain the
pile penetration process and the changing trend of soil parameters. According to the
research results of this section, the phenomena of pile collapse and pile breakage in
pile driving construction can also be predicted, prevented and evaluated, which can
provide technical support for pile foundation construction.
12.5.1 Finite Element Analysis Model of Pile and Soil
The pile driving process of hydraulic hammer can be divided into two stages: the
first stage is the impact process of hydraulic hammer on the pile body, in which the
pile body obtains certain strike energy; the second stage is the process of pile
penetration into soil under strike energy. The energy of the hydraulic hammer
before hitting the pile body is related to the instantaneous velocity and the mass of
the movable part of the hydraulic hammer body. The expression of the strike energy
of the hydraulic hammer is as follows.
E t ¼
1
2
Mv
2
ð12:48Þ
12.4 Rapid Piling Process of High-Speed Pneumatic–Hydraulic Composite Hammer
307
Hydraulic–pneumatic pile driving hammer can effectively achieve the impact of
large diameter and tonnage piles. The falling speed and strike energy of the
hydraulic hammer depend on the parameters of the low-pressure accumulator and
the diameter and length of the oil return pipeline. The shorter the length of the
return pipe and the larger the diameter are, the greater the strike energy of the
hydraulic hammer is. Low-pressure accumulator can quickly absorb the hydraulic
oil discharged from the hydraulic hammer, so that the hydraulic hammer drops
rapidly, thereby improving the strike energy of the hydraulic hammer.
12.5 Contact Model Pile and Soil
Pneumatic–hydraulic hammer uses the combined action of weight of hammer and
pneumatic–hydraulic pressure to achieve the impact of hammer and pile and penetrate the pile into the soil. This section mainly analyzes the impact process of
hammer and pile, and the contact between pile and soil after impact. The mathematical model of pile-soil contact process is established by software ANSYS, and
the distribution of displacement, stress, shear force and strain in pile-soil contact is
obtained by simulation calculation. The comparison between theoretical results and
field application shows that the proposed theory and method can well explain the
pile penetration process and the changing trend of soil parameters. According to the
research results of this section, the phenomena of pile collapse and pile breakage in
pile driving construction can also be predicted, prevented and evaluated, which can
provide technical support for pile foundation construction.
12.5.1 Finite Element Analysis Model of Pile and Soil
The pile driving process of hydraulic hammer can be divided into two stages: the
first stage is the impact process of hydraulic hammer on the pile body, in which the
pile body obtains certain strike energy; the second stage is the process of pile
penetration into soil under strike energy. The energy of the hydraulic hammer
before hitting the pile body is related to the instantaneous velocity and the mass of
the movable part of the hydraulic hammer body. The expression of the strike energy
of the hydraulic hammer is as follows.
E t ¼
1
2
Mv
2
ð12:48Þ
12.4 Rapid Piling Process of High-Speed Pneumatic–Hydraulic Composite Hammer
307