The Gamagori Tunnel, wihch is one of tunnels under construction by the Aichi Irrigation Public Corporation, is a tunnel passing so-called “masa-do” an efflorescence consisting of granite, located at the end of the west main waterway of the Toyokawa Irrigation Project. There is a layer containing under-ground water at the top. part of the tunnel. In making the location, a number of discussions were carrird out on that tunnel should be passed in this masa-do or tunneled into the hard rocks located in the north to avoid this or an open canal should be provided in the direction of the south. As the results of various investigation, the construction was commenced after having judged to be quite safe to adopt normal construction method for excavating a tunnel into masa-do. But impossibility of progressing excavation has occured due to water flowing out with masa-do on the way of construction. Finally, alternation of the construction method was obliged to adopt pressure construction method, its preparation now being progressed. In this report, a consideration will be paid on in what cause was excavating a tunnel into masa-do determined and on the cause to have incured its failure.
Many debris barriers were constructed in the Chichibu Mountains and the distribution of these dams is closely related to geology; tectonic line, rocks and crustal movement. Dams were constructed on the Kannon yama-Tomoe gawa tectonic line which runs from northwest corner to southeast in the Tertiary System of the Chichibu basin. Almost of all dams were distributed in the crystalline schist area of the Toya upheaval mountain block, especially along the Jushi-Kunigami and the Zogahana-Asahine tectonic lines of the outsides of this block, and the drainage of the river Toki. In the Chichibu paleozoic complex they were built on schalstein and black slate along faults.
The paper is concerned with the measurement of dip and strike in the sound exploration record. The record is influenced in some physical characteristics of the sound; directinality, velocity, exaggeration. Then, discussed that these influences should be eliminated in the analysis of the record. And finally, dip and strike is measured by two apparent dip in the cross point of observed lines, by the calculation or nomographic methods usually. The nomographic method is convenient to measure many dip and strike. It is also introduced in this paper, the compilation and interpretation of the nomograph and the distribution of survey lines.