250 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



Note. — In this case H must be less than h and if the strata dip in the 

 other direction no location is possible. 



These will cover all cases of vertical boreholes. 



b. INCLINED boreholes: lengths, displacements and depths 



In these cases the boreholes may have an infinite number 

 of dips in amount in two directions at 180 deg. from one 

 another, i.e., corresponding opposed and 'together" 

 dips, and still be at right angles to the strike of the stratum, 

 provided the hole does not leave the plane normal to the 

 stratum strike, i.e., its full dip or rise direction plane (Figs. 

 168, 169). The angle 02 of Eq. (20) is 90 deg., making it 



H ± AB' tan 5 



X = 



tan a + tan 8 



according to the relations of the dips of borehole and 

 stratum. It will be found more convenient to measure 

 the surface slope 7 in these cases. 



C_-i-^ 



Fig. 168. 



1. The Borehole and Stratum Dip in the Same Direction 

 with the Borehole Upstream of the Outcrop (Fig. 168). 



la. The Length of the Borehole, 



TT 



BB" = —^ 



sm a 



