252 



DEEP BOREHOLE SURVEYS AND PROBLEMS 



Ic. The Total Depth of the Borehole. — This is the distance 

 to the base, i.e., BD. 



BD = H + h 



= H + 



B"E sin a 



sin (a — 5) 



and since 



we get 



B"E = AB" sin 5 



= H + 



AB" 



BD = H[\ + 



cot 5 — cot a 



cot 7 + cot a 



cot 5 — cot 



(27) 



2. The Borehole and Stratum Dip in Opposite Directions 

 against One Another with the Borehole Upstream of the 

 Outcrop (Fig. 169). 



^r 



Fig. 169. 



2a. The Length of the Borehole. 

 BB" = H/sin a 

 B'B' = H cot a 



and 



AB" = H (cot 7 - cot a). 

 L = BC = BB" + B"C 



