. Deep borehole surveys and problems. Boring. PROBLEMS 255 its bearing that of the seam dip plus 180 deg., say ,8 + 180 deg., where jS is the direction of full dip of the stratum and 5 its amount. Substituting in Eq. (21) we get for the shortest connection at a bearing 62 between hole and stratum strike directions 5C = i7 cos 5 + AB' cosec 5 sin di (34) /. THE SHORTEST OF ALL POSSIBLE BOREHOLES TO THE STRATUM Here the vertical plane holding point A in the stratum and B on the borehole mouth must have the direction ^ + 180 deg., so that 62 = 90 deg., and we get (Fig. 171). BC = H cos b + AB' co
. Deep borehole surveys and problems. Boring. PROBLEMS 255 its bearing that of the seam dip plus 180 deg., say ,8 + 180 deg., where jS is the direction of full dip of the stratum and 5 its amount. Substituting in Eq. (21) we get for the shortest connection at a bearing 62 between hole and stratum strike directions 5C = i7 cos 5 + AB' cosec 5 sin di (34) /. THE SHORTEST OF ALL POSSIBLE BOREHOLES TO THE STRATUM Here the vertical plane holding point A in the stratum and B on the borehole mouth must have the direction ^ + 180 deg., so that 62 = 90 deg., and we get (Fig. 171). BC = H cos b + AB' cosec 5 (35) This is similar to E'E of Figs. 168 and 169 „!„„ Fig. 171.—Borehole dipping against the beds. We shall not deal with upward holes, since these do not come under deep boring; also we will not go into the variant forms of Eqs. (21a), (216), (21c) and {2ld) above, which arise with contrary senses of hole and strata dips. Varying these, as we have done in the cases of vertical and inclined normal holes, will give the reader no difficulty and preserve the space at our disposal. II. Boreholes Not at Right Angles to the Strike of the Strata All the cases are covered by Eq. (21) for length, , H ± AB' tan 8 sin 62 L = BC = sin a + sin d\ tan 6 cos a (36) and it appears needless to draw the upstream and down- stream cases, since the previous examples are particular cases of these problems. The related displacement and depth problems will need no further embellishment here Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Haddock, M. H. (Marshall Henry). New York, McGraw-Hill
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