宇和盆地を水理地質学的に調査, 研究した結果, 以下のことがらがわかった。
1) 盆地堆積物は上部粘土層, 中部粘土砂れき互層, 下部砂れき層に区分され, 堆積物の堆積速度からみると, 全体として第四系の可能性が強い。この盆地堆積物のうち砂れき, 砂層が主な帯水層である。
2) 盆地には被圧地下水が存在し, 深度70～95mのさく井で, 100～1,500m³/dayの揚水量がある。盆地の地下水開発量は日単位面積排水量1,000m³/day/km², 2,445,000m³/yearを目安として行なうべきであろう。
3) 盆地の基盤岩は秩父古生層で, 重力探査によって推定基盤深度は, 地表下約100m, EL. 120m程度と推定される。
4) 盆地の被圧水の水質は鉄分で汚染されており, その鉄分は下部帯水層程少ない。

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In order to investigate the geophysical property of sea bottom an acoustic exploration method with a sonoprobe, sparker or airgun as a source depending on the investigation purpose has been commonly used. Since this method proviedes a graduation recoding by a reflected acoustic wave at boundaries below sea bottom, a vertical section of geological structure can visibly be recognized. However, for the purpose to investigate the hardness of rocks in such cases as an investigation of engineering geology, it is not sufficient because this method does not indicate the wave velocity of rocks.
A marine seismic investigation called “Refraphone method” has been carried out by improving seismic source and geophone at sea bottom. In this method 3 to 4 hydrophones (8 to 10 depending on the situation) for the marine refraction method survey are positioned on the profile line at sea bottom and a popping ship navigating on the line at 2 to 3 knots pops an airgun, which in connected to a high pressured nitrogen gas cylinder and kept at a certain depth under the sea surface, at regular interval of 6 to 14 seconds. The refraction waves are recorded in a data recorder simulataneously with the popping timing transmitted from the ship at each receiving point.
Some characteristic of this new method are summarized as follows;
(A) Since an airgun is used instead of the dynamite, no damage accurs to fishes. There is no explosion sound in the air, as the gun pops more than 5 meters under sea surface.
(B) Surveying time can be reduced by an easy operation in comparision with traditional methods. The operation on the sea with a slow tidal current in carried out more efficently than on the ground. This applid also to that in narrow strait with a fast tidal current since it can be carried out taking the advantage of a short period of turning current.
(C) A radio wave telrometer used for guiding recording ships and a popping ship makes the position measurment more accurate than before.
A refraction wave investigation “Refraphone method” provides similarly reliable data to those obtained from a ground surface seismic investigation. By the analysis of records in “Refraphone method” the survey on the sea surface can easily be performed in order to investigate the distribution of longitudinal wave velocity which indicates the hardness of rocks, velocity and width of fractured zone recongnized as a low velocity zone, properties and thickness of weathered layer which covers bed rocks, thickness of sedimentary layer and its velocity which indicates the solidity of the layer, and so forth.

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The Hoyo straits lies between Shikoku island and Kyushu island.
We are now planning to construct the Shinkansen tunnel under this straits (the undersea length is about 14km). The geological investigation for this project was started in 1975. The main points of the investigation are as follows:
a. Land approach portion: Geological survey seismic prospecting, boring, magnetic prospecting
b. Undersea portion: Submarine observation, dredging, sonic-prospecting, undersea boring
At present, the geological investigation is still continuing, but so far have revealed that the area is underlain with green schist of palaeozoic formations and diluvial unconsolidated seabed deposits.
To continue these, next points should be studied in further detail
a. The placement and characteristics of faults.
b. The distribution and thickness of unconsolidated seabed deposits.

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Geomechanical problem of estimation as applied to the true direction and the precision of observation of joints in foundations is fundamental.
Portable computer makes calculation easy on the simultaneous distribution of amplitude and direction of the vector sum of a number of random unit vector which correspond each joint in rocks.
A example of program obtained and its application are illustrated.

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This report desclives the outline of nature in Bolivia and the result of the survey in 1979 along the section of the railways affected by the disasters.
The disasters were debris flow, slope failure, collapse of embankment, flood, etc., that had been caused by heavy rain fall atack in rainy seasons.

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