PROBLEMS 



275 



Set off from A a line at the hole bearing N. 50°E. and on 

 it the dip angle of the hole, i.e., 60 deg., setting off on the dip 

 line A Ax = 1,200 ft. the borehole length. Drop a per- 

 pendicular A1A2 to meet the direction line from A in A 2, and 

 Ao will be the plan position of the end of the borehole from 

 A. In a similar manner, using the relevant data, get B2 



^*^. 



Fig. 184. — The three slanting borehole problem. 



and Ci . AoBoCi is the actual area encompassed by the bore- 

 hole bases. On line A2C2 set off the depths of A2 and C2 

 at these points, respectively, at right angles to this line, 

 so getting As and C3. Join A3 to C 3 and produce to meet 

 A2C2 produced in x. (Note that A2A3 is the depth of A 2 

 and 52^3 is that of Bo and C2C3 that of C2.) Similarly set 

 off AoA^, the depth of A2, and B2B3, the depth of B2, 

 at right angles to ^2^2 as shown. Connect A' 3 to B3 

 and produce to meet A2B2 produced in y. x and y are on 

 the strike of the stratum. Drop a perpendicular C2D 

 on to the strike line xy and erect one, C2E, at C2 equal to its 

 depth. Join ED and the angle EDC2 is the amount of dip 

 and its direction is DCo. Check by B2 GF using the same 

 reasoning. 



