The mechanical and hydraulic properties of rock fractures are strongly influenced by surface conditions of the fractures. In this study, roughness heights of both surfaces of an artificially fractured rock were measured with a laser displacement meter, and then combined numerically to derive the apertures between the both surfaces. The spectrum of the surface roughness on a log-log plot is linear in a range of frequencies. In low frequencies, the power spectral density of the aperture variation is less than that of the surface roughness. The histogram of the apertures approximates a normal distribution because the measured fracture was considerably matched. The auto-correlation distance, being a length within which two points are spatially correlated with each other, of the surface roughness ranges between 1 to 4.5 mm, and that of the aperture variation is about 1 mm. To examine the effect of the auto-correlation distance of aperture variations on hydraulic properties of fractures, different auto-correlation distances were chosen, 20 aperture distributions for each auto-correlation distance were generated by using a personal computer and flow simulations were carried out. The simulations show that flow rates through fractures depend on not only the mean separation between the both surfaces but also the auto-correlation distance. In fractures composed of apertures with larger auto-correlation distance, the flow rates greatly vary fracture by fracture even in the same mean separations, and the average flow rate tends to approach the one predicted by the parallel plate model. When an aperture distribution has no auto-correlation, the flow rate could be uniquely estimated by the ratio of the mean separation between both surfaces to the standard deviation of apertures.
Blanket grouting tests were carried out at the cut-slope in order to consider the grouting mechanism and its effect. Geotechnical investigation such as geotomography, borehole television, etc., were introduced as well as or-dinary measurements of grouting performance. The results are summarized as follows: ·The flowing direction of paste is controled by orientation of fractured zones, seams and joints together with the gravity action. ·Continuous joints and small joints connected with together are injected at the begining stage of grouting, and then small joints filled up gradually. ·Seismic-and resistivity-tomography help effectively to grasp the state of the rock mass being injected, offering informations, qualitatively and quantitavely.
One of the big themes for forecasting the occurrence of slope land disaster is to predict “where”, “in what scale” and “when” such disaster may take place. When the theme “where”among them is to be discussed, it is general practice to analyze the factor of occurrence. The analysis of occurrence factor can be roughly classified into the case where it is grasped as a “point” from a viewpoint of “where the disaster took place”, and the case where it is grasped and analyzed as a “surface”from a viewpoint of “in what scale the disaster took place”. In case when the analysis is made from the viewpoint of “where the disaster took place”, the occurring area, sliding area and piling area are all represented by one point, and all of them are treated as an average factor. Therefore, it is impossible to adequately analyze “under what conditions of land the disaster took place”. Similarly, the discussion on “under what conditions of the land”is not sufficient in case where the disaster is analyzed from the viewpoint of “in what scale it took place”. When we deeply analyze the occurrence factors, it is essential to analyze the case from the viewpoint of “under what conditions of land the disaster took place”. In that case, it is important to analyze the head cleavage or sliding cliff of land slide as a line. For this purpose, it is effective to use the overlay method of images with the unit of pixel of some proper size as the analysis method. In this study, we report the idea of method to analyze the factors of place of slope land disaster as the “line” through the digital image analysis of aerial photograph data.
The manborn and carborn γ-ray survey using a multichannel analyzer with NaI (Tl) scintillation detectors was carried out across the Atera active fault in Yamaguti Village, Nagano Prefecture. The manborn was investigated 880 m long along the Ohsawa River across the Atera Falts. The data of the fluctuation of214Bi, 208Tl, 40K and ratios of those three radioactivity nuclides were compared with the degrees of fracture of outcrop rocks on the river-bed in order to evaluate the parameters for locating of buried faults. The carborn was carried out 50.1 km long through the Atera active fault to reveal the regional distribution of radioactive anomalies. The sharp anomalie of the fluctuation ratio which was a measured value to moving average of214Bi/208Tl, 214Bi/40K on the ground surface was appeared above fault gouge. From viewpoint of fault mapping the most important parameteres which can indicate location of fault are214Bi/208Tl and 214Bi/40K. Corrections for elimination of Compton scatterring is found more effective to emphasize anomalies. In the area of granitic rocks, three geological settings of uranium anomaly are known: the fault zone, the boundary of host rocks of contact metamorphism and the roof pendant. The anomalies of214Bi/208T1 fluctuation ratio in investigated area from carborn distinguish the fault zone from the boundary of host rocks of contact metamorphism. From analysis of the γ-ray spectrometry around these anomalies, it was clarified that the anomalies of214Bi/208Tl and214Bi/40K around faults are due to a little increase of y-ray activities of214Bi and decrease of208Tl and40K. On the other hand, the anomalies around the boundary of host rocks of contact metamorphism are due to only increase of214Bi.
Heavy rain fall caused the flood at the central part of Saga City in July 2, 1990. Deep flood zone was concentrated at the suburbs that are newly developped areas of Saga City. Leveling was carried out for the water surface of flood and ground surface to clarify the influence of landsub sidence or drainage canal. Simulations based on the tank model were carried out to reproduce the flood depth, and to check the influence of landsubsidence or drainage canal. It proved that the real drainage ability is lacked to drain the flood water, and the landsubsidence decrease the ability of drainage.