Journal of the Japan Society of Engineering Geology

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Bore hole camera with 44 mm in diameter, which can take un-distorted panoramic (360°) picture of the inner surface of the hole has been devised by joint study and research of Electric Power Development Co. Ltd., and Nac Incorporated.
A mirror located in front of the lens turns 360° together with a illuminating lamp and transmits the image of the hole wall onto the feeding film through the lens, Pechan prism and slit. The Pechan prism precisely turns half the turning angle of the mirror and corrects the image which is transmitted from the turning mirror.
Turning of the mirror, lamp and Pechan prism and feeding of fhe film are synchronously driven by a DC motor set in the camera and can be operated with the controller from the ground surface through a cable. The camera operates at either 100V AC or 12V DC.
The camera can hold a roll of 16mm film for 10 feet long each charging. One turning of the mirror feeds 68.55 mm of film. The hole length photographed by one turning is 22.1 mm in case of 46mm diameter hole, and 32.1 mm for 66 mm diameter hole.
The magnetic north is automatically marked on the photograph. The stainless-steel cylindrical outer shell is watertight under pressure up to 20kg/cm².

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This article deals with some examples of geological investigation methods and matters to be considered with respect to geological f easibility in the reservoir which is to be founded on karstified or calcareous rocks. The illustrated reservoir to be planned by EGAT (Electricity Generating Authority of Thailand) is on the Quae Yai River in western Thailand. In connection with the technical co-operation extended to EGAT, EPDC has been carrying out the detail design of the dam (rockfill type; crest length 615m and maximum hight 140m) and geological investigation of the reservoir (surface area at NHWL, 404.65km² and total strage capacity, 17, 200×10⁶m³). The investigation methods of the reservoir site mainly consist of geological interpretation by air-photos, geological mapping, hydrogeological survey, some core borings and laboratory tests on the samples of rock, and water which were collected during the field survey.
Judging from the geiologic conditions revealed as a result of the recent investigations, EPDC has reached the conclusion that the fear of leakage which had been entertained is almost entirely eliminated.

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