HOLES FOR PROSTAR
1.Hole Diameter
Allowable range of hole diameter for PROSTAR is 36¡«¡«50mm(1 3/8 ¡«20).
The larger the hole diameter is, the greater the expansive stress becomes and the wider the hole spacing becomes.
2.Hole Length
¢ñ. This varies with the SHAPE of the object to be demolished or the break plan.(Refer to Table-1 regarding standard hole length)
¢ò.This varies with the MATERIAL of the objects to be cracked or the break plan. Refer to Tabel-2;Table-3 as a guide line.
NOTE: When the length is less than 3 times that of the hole diameter, less cracking will occur, the breaking effect is lessened and the time required for demolition is increased.
3. Angle of Hole
It is preferable to drill holes vertically, but in case of a thin material, consideration should be given so as to make a long hole by drilling it obliquely since a greater effect is achieved with a deeper hole.
4. Hole Spacing
Hole spacing varies with the properties of rock, joint, volume to be removed, conditions of free surface, quantity of re-bars, secondary breaking, work period etc.
Table-1: Hole Length
|
Kinds of objects |
Hole Length |
|
Boulder |
80% of height |
|
Bench |
105% of height |
|
Concrete |
90% height |
Table-2: Hole Spacing for Rock
|
Kings of Rocks |
Hole Spacing |
|
Hard Virgin Rock |
40¡«60cm (1¡ä4¡å¡«2¡ä) |
|
Soft Virgin Rock |
50¡«70cm(1¡ä8¡å¡«2¡ä4¡å) |
|
Presplitting of the above Rocks |
30 ¡«60cm£¨1¡ä¡«2¡ä) |
Table-3: Hole Spacing for Concrete
|
Kings of Concrete |
Quantity of Re-bars(kg/m3) |
Hole Spacing |
|
Plain Concrete |
0¡«30 |
40¡«70cm(1¡ä4¡å¡«2¡ä4¡å) |
|
Reinforced
Concrete |
30¡«60 |
30¡«40cm(1¡ä¡«1¡ä4¡å) |
|
60¡«100 |
25¡«35cm(10¡å¡«1¡ä2¡å) |
|
Over 100 |
20¡«30cm(8¡å¡«1¡ä) |
