孔曲りのメカニズムおよび給水量の影響について
ボーリングにおける孔曲りに関する研究 (第1報)
1975 年 91 巻 1053 号 p. 709-712
詳細
1975 年 91 巻 1053 号 p. 709-712
By an experimental reappearance of the crooked-hole phenomenon of a deep boring, a series of the studies concerning the investigation of the influences of possible causes on a crook has been proceeded by authors. As a part of the above. the mechanism of this crook of a borehole and the influence of the circulating rate of water on it are described in this paper.
An artificial rock sample having the inclined boundary of two layers of different strengths caused by the ratio of the content of cement and the pulverized limestone was made, and it was drilled with the non-coring metal bit of 36mmφ, 9mm in length set to the rod of 10.5mmφ, 2000mm in length, in this experiment.
Consequently, it was proved that to produce the crook of borehole was possible by the drilling of a short, borehole even the length within 300mm and the deviation of the borehole to the direction of “up-dip” side occurred after shifting to that of “down-dip” side primarily. And, according to the increase of the wearlands of tips of the bit, it was found that the more the circulating rate of water raises the smaller the degree of the deviation of the borehole becomes.
