the inner wall of the inner sleeve is the intake passage of the back chamber, and the
central hole of the piston is the exhaust passage of the back chamber.
Top Drill Company of Korea began to produce DTH hammers in 1999.
Selection of special steel and high precision machining, the production of DTH
hammer can be equipped with different shock absorbers, according to the specific
application of the choice of positive or reverse circulation drilling, change the
opening pressure of the check valve. The drilling range is from small diameter
70 mm to large diameter 1200 mm. The product parameters of large diameter DTH
hammer with drilling diameter over 400 mm are shown in Table 11.4. It can be seen
from the table that the connection mode between DTH hammer and drill pipe
includes pin connection or hexagonal connection.
The main technical difficulties of large diameter pneumatic DTH hammer are as
follows:
(1) Drilling efficiency is low. Large diameter foundation pile hole has large
diameter, complex drilling stratum, high requirement of drilling verticality,
good quality of grouting, and the hole position cannot be moved. These
characteristics and requirements bring some difficulties to large diameter drilling construction. Usually, the upper part of the borehole is a loose layer or soft
layer, and the lower part is moderate weathering or even fresh bedrock; or the
soft layer or loose layer is intercalated with large boulders and drift stones.
Hard rock or big solitary rock drilling workload only accounts for about 10% of
the total footage in drilling, but the drilling efficiency is very low, and the
drilling time accounts for more than 50% of the total drilling time. How to solve
Table 11.4 Pneumatic DTH hammer parameters table of top drill, Korea
Model
Borehole
diameter (mm)
Connection mode
External
diameter (mm)
Length
(mm)
Weight
(kg)
ACE120 311*451
Pin connection
286
1889
608
ACE380 445*559
Pin, hexagonal
connection
376
1715
1140
TD320
355*475
Pin connection
320
1818
890
TD350
445*508
Pin connection
357
1866
1080
TD450
460*610
Pin, hexagonal
connection
400
1807
1338
TD450S 460*610
Pin, hexagonal
connection
424
1881
1492
TD550
610*850
Pin, hexagonal
connection
525
1875
2308
TD700
710*975
Hexagonal
connection
650
1867
4300
TD800
870*1 200
Hexagonal
connection
758
1884
6000
TDU350 445*508
Pin connection
350
1499
936
11.2 Principle and Classification of Pneumatic DTH Hammer
205
central hole of the piston is the exhaust passage of the back chamber.
Top Drill Company of Korea began to produce DTH hammers in 1999.
Selection of special steel and high precision machining, the production of DTH
hammer can be equipped with different shock absorbers, according to the specific
application of the choice of positive or reverse circulation drilling, change the
opening pressure of the check valve. The drilling range is from small diameter
70 mm to large diameter 1200 mm. The product parameters of large diameter DTH
hammer with drilling diameter over 400 mm are shown in Table 11.4. It can be seen
from the table that the connection mode between DTH hammer and drill pipe
includes pin connection or hexagonal connection.
The main technical difficulties of large diameter pneumatic DTH hammer are as
follows:
(1) Drilling efficiency is low. Large diameter foundation pile hole has large
diameter, complex drilling stratum, high requirement of drilling verticality,
good quality of grouting, and the hole position cannot be moved. These
characteristics and requirements bring some difficulties to large diameter drilling construction. Usually, the upper part of the borehole is a loose layer or soft
layer, and the lower part is moderate weathering or even fresh bedrock; or the
soft layer or loose layer is intercalated with large boulders and drift stones.
Hard rock or big solitary rock drilling workload only accounts for about 10% of
the total footage in drilling, but the drilling efficiency is very low, and the
drilling time accounts for more than 50% of the total drilling time. How to solve
Table 11.4 Pneumatic DTH hammer parameters table of top drill, Korea
Model
Borehole
diameter (mm)
Connection mode
External
diameter (mm)
Length
(mm)
Weight
(kg)
ACE120 311*451
Pin connection
286
1889
608
ACE380 445*559
Pin, hexagonal
connection
376
1715
1140
TD320
355*475
Pin connection
320
1818
890
TD350
445*508
Pin connection
357
1866
1080
TD450
460*610
Pin, hexagonal
connection
400
1807
1338
TD450S 460*610
Pin, hexagonal
connection
424
1881
1492
TD550
610*850
Pin, hexagonal
connection
525
1875
2308
TD700
710*975
Hexagonal
connection
650
1867
4300
TD800
870*1 200
Hexagonal
connection
758
1884
6000
TDU350 445*508
Pin connection
350
1499
936
11.2 Principle and Classification of Pneumatic DTH Hammer
205