This paper consisted the general part of the legal consultation report for the case at issue conserning to dam construction in 1961 which contained the introdnctory, general and special parts to conclude the engineering geological opinion to the possibility and propriety to construct the proposed dams. Extent of geological survey for civil engineering works naturally varies much according to the scale of the project. With the expanding scale of construction works, engineering geological survey should systematically programed intimately connected throughout to the stages of the work from preliminary survey, planning, design, execution and through maintenance. This paper summarizes how the engineering geological survey should be for large scale dam project by reviewing the transitional ways of geological survey with the expansion of dam scale. A few such transitional case histories of geological survey for arch dams are also summarized. It is hoped that this way of geological survey will be followed as the basic principle of engineering geological survey will be followed as the basic principle of engineering geological survey not only for dams but for large scale civil Engineering works in general.
In the San-in area some kinds of granites belonging to the Paleogene period are widely developed. The writers have investivated the joint clay of these granites connecting it with the mechanism of the collapsed caused by heavy rain fall. Main types of joint clay assemblage are as follows: (1) monmorillonite type, (2) sericite type, (3) monmorillonite-sericite assemblage type, (4) monmorillonite-sericite-kaolinite assemblage type, (5) monmorillonite-sericite-hydrated halloysite assemblage type, and (6) sericite-kaolinite-hydrated halloysite assemblage type. The characteristic form of slope failure on weathered granites caused by heavy rain fall is landside that weathered rock blocks enclosed by joint planes slither down joint plane. In the event of such a collapse, these joint clay acts as cleavable plane and lubricant.
The tunnels of 55 national hyghway are constructed or under construction by the Ministry of Construction in mountainous Shikoku disrict which mainly consists of Paleozoic, Mesozic sedimentary and metamorphic rocks. The writer summerized geological conditions and construction records of these tunnels. There is distinct difference in selection of steel support type of tunnels in Paleozoic and Mesozoic rocks which will be caused by their geological conditions. It is shown that difficulties of construction, containing failures of portal, surface subsidence, caving and squeezing grounds are closely connected with geological feateres of tunnel sites in Shikoku.