The in-situ stresses are determined by the Flat-jack method by making three slots (P, Q, and R) on the wall (ABCD) of a mine gallery as shown. The in-situ stresses \( \sigma_P \), \( \sigma_Q \), and \( \sigma_R \) are determined at slot-P, slot-Q, and slot-R, respectively. If \( \sigma_P > \sigma_Q \), and \( \sigma_R = 0 \), the shear stress on the wall is
The observations from a correlation survey are shown. If the coordinates of points C and D are (East: 375 m, North: 1120 m) and (East: 376 m, North: 1121 m), respectively, the whole circle bearing of the line EF is
CD = 3.0 m CE = 4.2 m \( \angle DEC = 1'' \) \( \angle DEF = 170^{\circ} 20' \)