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HOLE DESIGN

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    HOLES FOR PROSTAR

    1.Hole Diameter

    Allowable range of hole diameter for PROSTAR is 3650mm(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

    . This varies with the SHAPE of the object to be demolished or the break plan.(Refer to Table-1 regarding standard hole length)

    .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

    4060cm (14填2)

    Soft Virgin Rock

    5070cm(18填24)

    Presplitting of the above Rocks

    30 60cm1䡫2)

    Table-3: Hole Spacing for Concrete

    Kings of Concrete

    Quantity of Re-bars(kg/m3)

    Hole Spacing

    Plain Concrete

    030

    4070cm(14填24)

     

     Reinforced

    Concrete

    3060

    3040cm(1䡫14)

    60100

    2535cm(10填12)

    Over 100

    2030cm(8填1)