GB467130A - Means for surveying bore-holes and strata revealed thereby - Google Patents

Abstract

467,130. Borehole surveying. HUM. PHREYS, F. June 3, 1936, No. 15492. Convention date, Sept. 12, 1935. [Class 97 (ii)] Relates to instruments for indicating the inclination and orientation of the bottom of a borehole and for making a directionally indicative mark on a piece of bore core in situ in the borehole. As shown, a casing 16, carried between compression springs 14, 15, in an outer casing 2, supports on pivots 23, 25 a clinometer cage 7 and in gimbals 32 a compass card 31. The clinometer cage has a biassing weight 26, which swings it into the vertical plane containing the borehole axis, and carries on a pivot 28 a pendulum 27 at the lower end of which is a pointer 29 swinging over a transparent curved scale 30 arranged over the compass card 31. A magnetic needle 33 is pivoted over the compass card which is prevented from rotation relatively to the outer casing 2 by a pin and groove connection 17, 18 between the casings 16, 2. A directionally indicative mark is made on a flat surface ground on the bottom of the borehole by a diamond 10 on a finger 11 pivoted at 12 to the bottom of the casing 2 and urged downwards by a spring 13 so that the diamond is moved radially on the bottom face of the borehole by the weight of the instrument. The indications of the pendulum 27 and magnet 33 are photographically recorded on a sensitive sheet 34 by a lamp 21 the circuit for which is closed by a time switch 19. In a modification the clinometer cage and pendulum are replaced by a bob hanging by a thread so that when the instrument is vertical it lies over the centre of the compass card and when inclined moves over concentric graduations on the compass card. The device shown in Fig. VII enables the core, after it has been extracted, to be placed in a position corresponding to that which it occupied in situ. The core 39 is clamped in a holder 40 which is rotated on the horizontal pivot attaching it to the vertical standard 43 in accordance with the inclination of the bore-hole. The standard 43 is carried at one end of an arm 44, which is rotated on the pivot attaching it to the centre of a horizontal circular scale 45 in accordance with. the orientation of the borehole. A glass plate 59 marked with a line 60 and carried by a plate 58 facilitates the orientation of the core about its own axis in accordance with the position of the mark 41 and enables the dip and strike of strata in the core to be determined. The plate 58 carries a protractor 62 from the centre of which hangs a pendulum 61 and is connected by links 57, 56 to a spindle 53 rotatably mounted on the top of the standard 43.