Mining knowledge

Weisbach Triangle : When transferring ground level azimuth U/G by suspensions  of two wires down a shaft. It is difficult to set up the  theodolite exactly in line with them. In addition one wire  being nearer obscures. The wire beyond leading to an  inaccurate bisection. In weisbach method the theodolite is  set up slightly out of line forming a small triangle with the two  wires. This triangle is known as weisbach triangle & the  azimuth of the line joining the two wires is found by solution  of the triangle of formed. .α is obtained form the triangle W1  TW1 by the sine rule   α sin β sin α= ----------------- e = c.sinα b In a weisbach triangle W2 TW1 called the weisbach angle β & the ratio c/b must be very small for  which the theodolite station (T) should be very near to the wire (W1). If the weisbach angle is less  than 25 minutes. There is no necessary of measuring sides. The angle should be measured very  accurately to avoid any error. Purpose of correlation survey : Th

Weisbach Method of correlation : The weisbach method of correlation is usually preferred when only one shaft is available.  The  method consists of suspending two plumb wises which form a plumb plane and azimuth of the  same is determined at the surface and taken U/G at the shaft inset and thereafter transferred to  the U/G base or reference line. Two plane wires A & B made of anticorrosive crucible steel 0.1 cm diameter having  breaking strength of 150” g and to avoid king on a small drums fitted with brake or ratchet to hold  them in any desired position are lowered down the shaft tin washers are passed down by the  wires from the surface & they are free of obstruction. The smaller plummets are then replaced by  symmetrically shaped finned plumb bobs made of lead. When the wires hang vertically each  plumb bobs immersed in a barred of water to cut down oscillation due to (i) simple pendulum  motion, (ii) Irregular mass in strata, (iii) air current, (iv) dropping water. The lo