gas pressure in nitrogen chamber and weight of hammer body. In the descending
stage, the hydraulic oil in the lower chamber of the hydraulic cylinder 2 flows back
to the tank through the reversing valve 5 and the long return pipeline. At this time,
the low-pressure accumulator 5 is used to absorb the hydraulic oil in the lower
chamber of the hydraulic cylinder, so as to realize the rapid descent of the hammer
body. During the descending process, the hydraulic pump supplies oil to the
high-pressure accumulator 6. The acceleration of hammer striking pile body can
reach 2 g. After the hammer strikes the pile body, the reversing valve 5 closes, and
the hammer continues to exert pressure on the pile for a certain period of time, that
is, to turn into the pressure-retaining stage.
12.4.1.4 Pressure-Retaining Stage
Figure 12.24 shows the hydraulic system diagram of the pressure-retaining stage of
the hydraulic hammer piling process. In order to maintain a certain force on the pile
body and prevent the elastic rebound of the pile body, after the hydraulic hammer
strikes the pile body, the electromagnetic reversing valves 7 and 5 are closed and
enter a certain period of pressure-retaining stage. The pressure-retaining time is
determined by the holding delay relay in the electrical control system. After the
pressure-retaining time is over, the electro-hydraulic reversing valve 7 is energized
and transferred to the rising stage for a new round of work cycle.
Fig. 12.23 Hydraulic system diagram for descending stage of hydraulic hammer piling process
12.4 Rapid Piling Process of High-Speed Pneumatic–Hydraulic Composite Hammer
299
stage, the hydraulic oil in the lower chamber of the hydraulic cylinder 2 flows back
to the tank through the reversing valve 5 and the long return pipeline. At this time,
the low-pressure accumulator 5 is used to absorb the hydraulic oil in the lower
chamber of the hydraulic cylinder, so as to realize the rapid descent of the hammer
body. During the descending process, the hydraulic pump supplies oil to the
high-pressure accumulator 6. The acceleration of hammer striking pile body can
reach 2 g. After the hammer strikes the pile body, the reversing valve 5 closes, and
the hammer continues to exert pressure on the pile for a certain period of time, that
is, to turn into the pressure-retaining stage.
12.4.1.4 Pressure-Retaining Stage
Figure 12.24 shows the hydraulic system diagram of the pressure-retaining stage of
the hydraulic hammer piling process. In order to maintain a certain force on the pile
body and prevent the elastic rebound of the pile body, after the hydraulic hammer
strikes the pile body, the electromagnetic reversing valves 7 and 5 are closed and
enter a certain period of pressure-retaining stage. The pressure-retaining time is
determined by the holding delay relay in the electrical control system. After the
pressure-retaining time is over, the electro-hydraulic reversing valve 7 is energized
and transferred to the rising stage for a new round of work cycle.
Fig. 12.23 Hydraulic system diagram for descending stage of hydraulic hammer piling process
12.4 Rapid Piling Process of High-Speed Pneumatic–Hydraulic Composite Hammer
299