A study of regional tectonics using the lineament map drawn from Landsat TM (Thematic Mapper) images was conducted for the southern part of Chubu district, Central Japan. Many long lineaments appeared along boundaries of tectonic blocks which are characterized by directional orientation of small lineaments. Tectonically significant NE-SW lineaments crossing Akaishi Mountains were specially obtained.
It was found that the NE-SW lineaments coincide with geological or active faults in Akaishi Mountains and South Fossamagna areas, but they are not along with the sedimentary structure of the Paleogene and Neogene formation distributed in these areas. In the north side area of the NE-SW lineaments, main directions of small lineaments are N-S or E-W and seismic activity in the crust is low. In the south side area, on the contrary, the main directions of them are N-S or NE-SW and seismic activity is high. Moreover, the most north one of the NE-SW lineaments agrees with the boundary of the principal axis of the seismic stress. Many earthquakes, of magnitude more than 4, also occurred on the NE-SW lineaments in Akaishi Mountains. Therefore, the NE-SW lineaments are considered to reflect the active fracture zones and extend to the Median Tectonic Line.

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The study using the slope-shaded map and lineament map from Landsat images reveals that the Kinki district consists of several geologic blocks resembling a mosaic. The main lineaments are divided into four patterns by their direction and geological significance: they are N-S, E-W, NE-SW, NW-SE and sometimes cut each other. Some of them show a relatively good agreements with the distribution of active faults and linear distribution of microearthquake epicenters.
Some large lineaments are located in the boundary of geologic blocks. Their distribution patterns seem to indicate that this district has been under an E-W compressive force at least throughout the Quaternary.

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The determination of yield functions is the first step for the derivation of the constitutive law of geo-materials. In thi: paper, a new yield function is proposed by incorporating a parameter k, which is related to the creation of new fracture surfaced uring failure of materials, into the modified Cam-Clay model based on the classical plasticity theory and the critical state concept in soil mechanics. The critical state is the stress state where materials plastically deform without plastic volumetric strain increments. The proposed model characteristically shows that plastic strain increment vectors are normal to the yiek surfaceswhich have more general shape on the Rendulic stress plane than an ellipse of the modified Cam-Clay model and that the yield surfaces intersect perpendicularly the hydrostatic axis aside from the origin of stress space.
The application of the proposed model to the experimental data of cement mortar (uniaxial compressive strength Dc=205kgf/cm₂) givesM=0.77 andk=0.66, where M is the ratio of octahedral shear stressτ_octto mean principal stressσ_mat the critical state. These values of M and k are considered to be appropriate in comparison with those of rocks in published papers. The assumption that M does not depend on Lode's parameter but is constant, in the proposed model, represents that the shape ofyield surfaces is a circle of Von Mises on the octahedral stressplanes. Furthermore, the initial yield stress, experimentally obtained, of am=250kgf/cm²on the hydrostatic axis causes the onset of dilatancy at about 80% stress level ofσ_cwhich may be a little higher. Since the experimental data used in this paper cover the region of contractancy only, it is necessary to confirm the validity of the proposed model for all stress states including that of dilatancy.

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The author tried to show close relationship between the distribution of fractures and location of large-volume pyroclastic flows since the Pliocene, using information from Landsat image together with geologic data. The following conclusions are reached : Centers of caldera volcanism in Kyushu Island are situated at intersections of three fractures. One of them is the Kagoshima graben and its northward and southward extension, and the others are tectonic lines which run across the Kyushu Island in NW or NE directions. Northeast Japan is cut by main three fractures which are distributed in northern, middle and southern parts and have NE, NW and NW directions respectively. Large scale pyroclastic flows had been erupted in these fractured zones. In southwest Hokkaido many fractures of NW to WNW directions controled the distribution and forms of calderas which were erupted in the latest Pleistocene. The Late-Pleistocene calderas are nearly square but not circular in shape. The rims of calderas are usually in parallel with the extention of the fractures. The pyroclastic flows erupted at the broken portions in the large scale structural zone such as grabens. The same phenomena indicate that the fractures have been helped the generation of the magma resulted from the melting of shallow zone material and its ascent with contamination by sial materials to produce voluminous acidic magma.

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Distribution of lineaments from the Landsat images around the Aso caldera shows good agreement with that of active faults which were found by geological investigations and photointerpretations. These active faults cut the Aso volcanic ash beds and sometimes the Akahoya ash bed which is the key bed indicating the age of about 6, 000 Y.B.P..
The lineaments elongated in ENE direction at southwest and northeast sides of the caldera correspond with the active faults which suggest the presence of the fracture zone that run under the caldera center.
Macroscopic investigations of the image also show the distribution of major lineaments which are elongated in NNW, NW and NE directions respectively, and are 20-30 km long in the basement rocks found in surrounding areas of the caldera. These lineaments seem to reflect the presence of young faults resulted from the tectonic movement since the Pliocene.

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Stress rate and strain rate controlled tests of sandstone were carried out under generalized triaxial stresses. In order to obtain stress loci in the principal stress space, in the latter tests, octahedral shear strain was increased under both conditions of the increment of horizontal principal strain dε_h=0 (uniaxial strain) and the increment of mean principal strain dε_m=0.
The results from the tests reveal that:(1) The failure curve of sandstone is somewhat more convex outward than that of Mohr-Coulomb. The lubricant inserted between the specimen and the platen reduces the failure strength in triaxial compression tests, but does not in triaxial extension tests.
(2) Under the condition of dε_h=0, the stress states change toward the failure curve, with a decrease in the gradient of stress loci which depends only on the Poisson's ratio of the specimen.
(3) Under the condition of dε_m=0, the strain at the peak in differential stress-strain curves which clearly appears as ε₂ runs from ε₃ to ε₁, does not agree with that at the extreme value in stress-strain curves. The stress states deviate from the line perpendicular to the hydrostatic axis and sharply change just before reaching the failure curve. They all tend to be directed toward a certain point thereafter. For the condition of plane strain (dε₂=0), σ₂ is not constant but decreases with σ₂=(σ₁+σ₃)/2. The difference in the relative value of ε₂ to ε3 makes the distinct stress loci, which are expressed in terms of the normal and shear stresses on the fracture plane.

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The total energy applied from an external system of a given specimen, in the process of fracture, is transformed into elastic strain energy and irreversible energy. The elastic strain energy is related to the violence at the fracture of brittle materials which characterizes rock or coal bursts.
In this paper, compression tests under a generalized triaxial stress system were made to obtain a three dimensional distribution of elastic strain energy in the failure surface. Results from the tests reveal that:-
(1) Elastic properties of the substance in a given specimen are shown by the gradient of the reloading curve rather than that of the envelope curve obtained from cyclic loading.
(2) The strength of mortar is neither influenced by the loading path nor cyclic loading. The failure criterion of mortar is represented as the failure surface which is somewhat convex outward beyond that obtained by Mohr-Coulomb.
(3) Elastic strain energy attains a maximum value at failure during the uniaxial compression test.
(4) Irreversible energy depends on the loading path, but elastic strain energy does not. The latter is dependent on the stress state in the failure surface. The locus of elastic strain energy in the failure surface is represented by an ellipse in the Rendulic plane whose major and minor semi-axes are related to Young's modulus and Poisson's ratio of the specimen.

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The mechanical and hydraulic properties of joints included in rock masses are affected significantlyby geometrical characteristics of the two surfaces making up each joint. It is recognized that the amplitude of seismic waves transmitted across a rock joint is more sensitive to changes in the joint properties than the velocity of transmitted waves. In this study, the real area of contact between the two surfaces of a joint under normal stresses is examined by means of measurig the amplitude of seismic waves transmitted across the joint. Seismic experiments are conducted using a joint model which consists of a single aluminum plate (2mm in thickness) ranging from 10mm to 50mm in diameter inserted between two cylindrical aluminum blocks (50mm by 50mm) or consists of multiple plates with an identical diameter of 10mm. It is shown from the experiments that seismic waves transmitted through the joint model attenuates monotonously with decreasig the total contact area of plate (s). Then the relationship between the amplitudes of seismic waves and the contact areas is given by A/A₀=α^0.75, where A₀ is the amplitude of seismic waves transmitted through the no-joint model, A is that of seismic waves through the joint model, and α is the ratio of contact area to the cross- sectional area of the cylindrical blocks. The reason for the equation being non-linear is that the energy of seismic waves passing through the central part of the circular section is greater than that of seismic waves passing through the outer part, which is caused by the difference in diameters between the joint model and the transducers. Thus the above relationship is valid only for the present measuring system. With the seismic measurements, three series of uniaxial loading are conducted on an artificial rock joint under mated and unmated contact conditions. The real contact areas estimated using the equation are 90% and 11% for mated and unmated conditions at the normal force of 12kN, respectively. The difference in contact areas is also reflected in the normal force-closure behaviors.

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The basic purpose of this paper is to reveal the Pliocene to Quaternary geotectonism of Northeast Japan using the Landsat images with geomorphological and geological data. The following conclusions are reached : a) Directions of tectonic lines which separated pre-Miocene basement into many blocks are NNW, NNE and NW. b) The tectonic lines of the Miocene predominate in NS, NNW and NW directions. c) Fractures of NW and NE directions have been formed since the Late Miocene and that of WNW one has been formed in the Pleistocene. d) Pleistocene and Holocene volcanoes distribute in the graben-like zones between two fractures of the Pliocene age, and the situations of the volcanoes correspond to the intersections of two fractures of NE and NW directions. e) Lateral movement of WNW or NW direction within the blocks of Backbone Range has been increased to form a westward curve of the Northeast Japan Arc. It seems that the movement began in Late Miocene and continued during Quaternary because many lineaments of WNW direction cut the Quaternary volcanoes. f) The Pliocene sediment along the Kitakami river increases its width of distribution southward, and many faults with NS directions dipping eastward exist in the Sendai Plain. These facts suggest the possibility of anti-clockwise rotational movement of the Kitakami Mountains. g) New grabens of NE directions distribute northward of the Kitakami Mountains and the Ishinomaki-Tyokaisan tectonic Zone with NW direction exists between the Kitakami Mountains and Abukuma Mountains. Based on these facts, it appears that the Kitakami Mountains has been remained as a rigid block and pressed the Backbone Range westward during the movement of the Plate with compressional stress from east to west.

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In order to reinvestigate the strain softening behavior of rocks, firstly, conventional triaxial tests for Ainoura sandstone were performed by using the stiff testing machine. It is an interesting test result that the strain softening behavior could not be controlled stably because of brittleness when confining pressure exceeds 30MPa rather than in uniaxial. The comparison between the local strains with the strain gauges and the apparent strain with the displacement tranceducer in the strain sofetning and residual regions manifests that the latter strain reflects the plastic shear deformation along the fracture plane formed in the specimen. It means that the strain softening behavior is not a intrinsic property of material but depends on the structure of the specimen.
Secondly, a model for the strain softening behavior was made based on the test results. This model is composed of an elastic cylinder, of length L and Young's modulus E_a, which includes a fracture plane diagonally at an angleθto the loading axis. Consideration of energy balance on this model gives apparent Young's modulus E a which characterizes the strain softeningbehavior of it; where g is an energy necessary to form the fracture plane in an unit area, and σs is a difference of the failure and residual strengths and is termed softening stress. The equation shows that the brittleness is increased with the length of the specimen or softening stress. The present experimental result that softening stress increased with confining pressure reasonably explains the unstable strain softening behavior under high confining pressure.

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This paper describes moisture movement in unsaturated sandstone and tuff, whose porosities are 13% and 29% respectively. For each rock three cylindrical specimens are prepared: dry (not perfectly) and saturated intact specimens, and one dry specimen including a tensile fracture parallel to the cylindrical axis. The side surface is sealed with silicon sealant to allow one dimensional movement of moisture. The 1cm lower part of the specimen is submerged in water, and the top surface is open to the room air. In this condition, water is infiltrated into the dry specimen upwards while the top surface of the initially saturated specimen becomes dry with time. During the experiments, relative humidity at two different heights above the top surface is monitored as well as total weight of the specimen. An evaporation rate is calculated from the difference between the two values of relative humidity, based on a molecular diffusion theory. In addition, water absorption at the top surface is measured using an infrared optical moisture meter. The experiments show that a steady state is not reached even in 70 days after the beginning of infiltration into the intact specimen. However, the changes of weight can be predicted with the data for the first 10 days, by a hyperbolic function which has two parameters giving a infiltration rate at the beginning of the experiment and weight at the steady state. The evaporation rate and the infiltration rate of intact sandstone are different from those of intact tuff, but each difference is not so large as that of the porosities. Distributions of saturation in the specimens are obtained from the results of the changes of weight and moisture at the top surfaces, which present increasing degrees of saturation with depth. When a two layer model composed of dry and capillary zones is used to estimate the evaporation rate in a drying process, the estimated value may include about a 50% error.

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This paper examines the fundamentals of underground development and its utilization, including the maintenance and management before, during, and after the planning and construction. It is expected that underground spaces will be densely concentrated within a given region. New problems will arise as follows: the suitable arrangement of underground openings, subsidence and instability due to weathering of the ground around the openings, changes in ground water flow, and so on. Once the underground space has been constructed, it is impossible to return the environment to its initial conditions. In addition repair and reconstruction due to damage are nearly impossible. Therefore, this paper discusses the durability (i.e. durable life) of underground structures from economical, functional, and physical points of view. Especially, the long term stability of underground openings is investigated in detail in connection with several previous accidents. In the future, it is necessary to recognize that “underground developments must be dealt with different from surface ones”. Success of projects depends on planning and maintenance done from a long-term viewpoint, including careful study concerning the affects such systems will have on society.

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