11.6 Typical Engineering Cases
11.6.1 Project Site
The project site is located at the west of Dayou Street, south of Middle East Road,
east of Youshan road and north of Xiahe Village, Xiahe District, Lishui City,
Zhejiang Province. The building area is about 83;000 m
2 , of which the underground
area is 19;900 m
2 . Construction is undertaken by Wenzhou Great Wall Foundation
Engineering Company. The diameter of piles is 600, 700 mm, the number of piles is
550, the length of piles is about 14 m, the amount of concrete works is 2715 m
3 , and
the amount of concrete reinforcing bars is 187 t. Located in the south of Lishui
Basin, the site belongs to the landform of big creek flood alluvial plain.
Stratigraphic geology is roughly distributed as follows.
(1) Layer miscellaneous fill: Recent backfill, backfill time is less than 6 years, layer
thickness 4:5 $ 6:5 m.
(2) Layer silty clay: flood alluvial origin, 1:5 $ 2:5 m thickness, soft plastic, silt
content is high, the property is close to silt, local transformation into silt,
formation bearing capacity characteristic value f ak ¼ 120 $ 130 kPa.
(3) Layer pebbles: alluvial origin, 6:0 $ 10:0 m thickness, medium density structure, characteristic value of bearing capacity f ak ¼ 280 kPa.
(4) It can be divided into three types:
(a) One layer of strong weathered siltstone: dark purple, 0:8 $ 1:5 m thickness,
medium density, characteristic value of bearing capacity of stratum
f ak ¼ 300 kPa.
(b) Two layers of medium-weathered siltstone: dark red, 1:0 $ 2:5 m thick,
f ak ¼ 10 $ 15:0 MPa, soft rock, rock basic quality grade V.
(c) Three layers of slightly weathered siltstone: purple red, f ak ¼
20 $ 35:0 MPa, which belongs to softer to harder rocks, and the basic
quality grade of rock is grade III to IV.
11.6.2 Model and Parameters of Pneumatic DTH Hammer
Large diameter pneumatic DTH hammer double rotary drilling rig is used for
drilling. The upper power head drives the DTH hammer and the lower power head
drives the outer sleeve. The large diameter DTH is hammered onto the long screw
drill rod. The drilling efficiency of this construction method is higher than that of
wave impact and rotary drilling by 5–10 times. The slag is discharged by wind
speed and the bottom of the hole is clean. During the drilling process, the steel
casing keeps track of the guard wall, and there is no collapse of the hole wall, which
ensures the construction quality and progress, and no slurry discharge and pollution
of the environment. As shown in Fig. 11.43, the main components of large diameter
11.6 Typical Engineering Cases
261
11.6.1 Project Site
The project site is located at the west of Dayou Street, south of Middle East Road,
east of Youshan road and north of Xiahe Village, Xiahe District, Lishui City,
Zhejiang Province. The building area is about 83;000 m
2 , of which the underground
area is 19;900 m
2 . Construction is undertaken by Wenzhou Great Wall Foundation
Engineering Company. The diameter of piles is 600, 700 mm, the number of piles is
550, the length of piles is about 14 m, the amount of concrete works is 2715 m
3 , and
the amount of concrete reinforcing bars is 187 t. Located in the south of Lishui
Basin, the site belongs to the landform of big creek flood alluvial plain.
Stratigraphic geology is roughly distributed as follows.
(1) Layer miscellaneous fill: Recent backfill, backfill time is less than 6 years, layer
thickness 4:5 $ 6:5 m.
(2) Layer silty clay: flood alluvial origin, 1:5 $ 2:5 m thickness, soft plastic, silt
content is high, the property is close to silt, local transformation into silt,
formation bearing capacity characteristic value f ak ¼ 120 $ 130 kPa.
(3) Layer pebbles: alluvial origin, 6:0 $ 10:0 m thickness, medium density structure, characteristic value of bearing capacity f ak ¼ 280 kPa.
(4) It can be divided into three types:
(a) One layer of strong weathered siltstone: dark purple, 0:8 $ 1:5 m thickness,
medium density, characteristic value of bearing capacity of stratum
f ak ¼ 300 kPa.
(b) Two layers of medium-weathered siltstone: dark red, 1:0 $ 2:5 m thick,
f ak ¼ 10 $ 15:0 MPa, soft rock, rock basic quality grade V.
(c) Three layers of slightly weathered siltstone: purple red, f ak ¼
20 $ 35:0 MPa, which belongs to softer to harder rocks, and the basic
quality grade of rock is grade III to IV.
11.6.2 Model and Parameters of Pneumatic DTH Hammer
Large diameter pneumatic DTH hammer double rotary drilling rig is used for
drilling. The upper power head drives the DTH hammer and the lower power head
drives the outer sleeve. The large diameter DTH is hammered onto the long screw
drill rod. The drilling efficiency of this construction method is higher than that of
wave impact and rotary drilling by 5–10 times. The slag is discharged by wind
speed and the bottom of the hole is clean. During the drilling process, the steel
casing keeps track of the guard wall, and there is no collapse of the hole wall, which
ensures the construction quality and progress, and no slurry discharge and pollution
of the environment. As shown in Fig. 11.43, the main components of large diameter
11.6 Typical Engineering Cases
261