Since it is known that the progress of rock weathering leadto the decrease of its seismic Velocity, the seismic velocities of rock are used to decide the weathered grades of the rocks, and we can determine whether or not a weathered rock can be excavated with ripper. This method is based on a correlation between seismie velocities and rippability, Rippable and nonrippable seismic Velocities are determined for the different types of rock.
This paper contains a discussion concerning to the jack m anod and the result of rock deformation test. In Yuda Dam, two kinds of jack method were performed at the concrete gallery wall which was regarded as an elastic body, by using a diaghragm aiming at uniformly distributed loading and a rigid disc aiming at equally displaced loading. In the case of uniformly distribruted loading, those results obtained from the surface displacement, strain meters embedded in the concrete and concrete test pieces, were approximately similar values. In the case of equally displaced loading, those results were various, and Youngs modulus calculated from surface displacement was about 1/3 to that by uniformly displaced loading method. In Koshibu Dam-site, the bedrock of test place consists of sound granodiorite, which is called Ikuta granite, the series of rock deformation test were peformed by jack method, water chamber method and seismic method. The relation between those results from water chamber method, jack method and seismic method was 1: 1.4: 2.2, and the difference of the modulus of deformatin by those three methods was than that which had been before.
Japanese National Railways has been carried out a Series of submarine geological surveys at the Akashi Straits where interisland-through rail-and road-way are proposed. According to the results hitherto obtai.ned, there develop widely gravellous formations (from latest-Tertiary to earliest-Quaternary) underlain by Miocene group (mainly sandstone with some shale and conglomerate) or older granite. So, the author presents an every-5m countour map of these underlying groups based on Sparkers records. By this map (Fig. 3), thickness of the gravellous beds and relief of. basement rocks are numerically illustrated, and its accuracy is thought to within±5meters examined from all the standpoints of concerning factors.
Underground condition of constructing a tunnel is strongly controlled by geological features such as kinds of rocks, geological structure, etc.An example, Yui tunnel of Shin-Tokaido line, is shown in this paper.In this case, hardness decreases at the position of anticlinal axis of strata. Mudstone, even crushed into breccia, holds its own impermeability.Underground water is reserved mainly in the compound strata of tuff?breccia and conglomerate, partly above a muds tone layer as a form of perched water. Places of water seepage are well related with the undulation and faulting of these aquifer in the tunnel.