Question 1)
As Surveyor in charge of an underground mine you have been instructed to design a tunnel to join a crosscut to a haulage drive. The details of the crosscut and drive are shown below.
Crosscut - Bearing: 71°06'25”
Grade: 1:70
Last Survey Station: 5417.744 E
2448.954 N
1099.439 RL Floor
Haulage drive - Bearing: 312°33'10”
Grade: -1:100
Last Survey Station: 5594.088 E
2384.402 N
1152.447 RL Floor
The face of the crosscut is 80m ahead of the last station. Both the crosscut and haulage drive
are 5m wide and 4m high.
The tunnel is to have a circular horizontal alignment turning right from the crosscut with aradius of not more than 50m and not less that 30m with a maximum grade of 1 in 10.
a. Compute the co-ordinates of the two tangent points for the most cost efficient solution.
b. Plot the crosscut and drives at suitable scale showing all relevant information. Show the proposed walls as dashed lines on the plan.
c. Compute the co-ordinates of a point (Stn 425) that is 5m along the centreline of the tunnel from the TP in the crosscut (TP1). Check your calculations using the plan.
d. From this point a chord line bearing 88°43’ is to be set out. At 2m intervals compute the centreline offsets from this line and reduced levels of the floor.)
e. At what chainage from Stn 425 should mining cease and why?