The main tasks of the overall design of large diameter DTH hammer impactor
include:
(1) Determine the parameters of DTH hammer impactor according to the selected
type and use requirements.
(2) Drawing the general assembly drawing of DTH hammer (including drill bit).
The overall design basis of DTH hammer impactor is as follows:
(1) Stratigraphic conditions: complex geology such as filling layer, clay layer,
pebble layer, and weathered sand layer.
(2) Drilling method and technology: Rotary force and axial thrust are provided by
double power DTH hammer drilling machine (combined construction of double
power head long screw drilling machine and pneumatic DTH hammer),
high-pressure gas is provided by air compressor, and percussive rotary compaction drilling is carried out.
(3) Conditions and requirements: Drilling without water and meet certain drilling
speed requirements.
11.3.2 Overall Structure
(1) Valveless DTH impactor
Large diameter pneumatic DTH hammer is designed for the construction of pile
foundation in complex geology such as filling layer, pebble layer, and sand layer.
Therefore, DTH hammer with low frequency and high impact energy is selected,
and its drilling effect is more remarkable. According to the requirements of pneumatic impact compaction equipment and DTH hammer at home and abroad,
valveless valve distribution mechanism is adopted. Figure 11.7 shows that the
valveless DTH impactor adopts a double cylinder structure, with grooves and holes
in the cylinder block for air intake and grooves in the piston. The reciprocating
motion of the piston can be realized by opening or closing the corresponding air
Fig. 11.7 Structure schematic diagram of valveless central exhaust DTH hammer (1—Upper
connector; 2—Check valve; 3—Adjust gasket; 4—Intake seat; 5—Inner cylinder; 6—Outer
cylinder; 7—Nozzle; 8—Piston; 9—Sleeve; 10—Guide sleeve; 11—Round keys; 12—Lower
connector; 13—Drilling bit)
11.3 Principle and Parameter Design of Large Diameter …
207
include:
(1) Determine the parameters of DTH hammer impactor according to the selected
type and use requirements.
(2) Drawing the general assembly drawing of DTH hammer (including drill bit).
The overall design basis of DTH hammer impactor is as follows:
(1) Stratigraphic conditions: complex geology such as filling layer, clay layer,
pebble layer, and weathered sand layer.
(2) Drilling method and technology: Rotary force and axial thrust are provided by
double power DTH hammer drilling machine (combined construction of double
power head long screw drilling machine and pneumatic DTH hammer),
high-pressure gas is provided by air compressor, and percussive rotary compaction drilling is carried out.
(3) Conditions and requirements: Drilling without water and meet certain drilling
speed requirements.
11.3.2 Overall Structure
(1) Valveless DTH impactor
Large diameter pneumatic DTH hammer is designed for the construction of pile
foundation in complex geology such as filling layer, pebble layer, and sand layer.
Therefore, DTH hammer with low frequency and high impact energy is selected,
and its drilling effect is more remarkable. According to the requirements of pneumatic impact compaction equipment and DTH hammer at home and abroad,
valveless valve distribution mechanism is adopted. Figure 11.7 shows that the
valveless DTH impactor adopts a double cylinder structure, with grooves and holes
in the cylinder block for air intake and grooves in the piston. The reciprocating
motion of the piston can be realized by opening or closing the corresponding air
Fig. 11.7 Structure schematic diagram of valveless central exhaust DTH hammer (1—Upper
connector; 2—Check valve; 3—Adjust gasket; 4—Intake seat; 5—Inner cylinder; 6—Outer
cylinder; 7—Nozzle; 8—Piston; 9—Sleeve; 10—Guide sleeve; 11—Round keys; 12—Lower
connector; 13—Drilling bit)
11.3 Principle and Parameter Design of Large Diameter …
207