Distributed discontinuities essentially affect to the mechanical behaviour of rock mass. Such discontinuities can be modelled by introducing the damage tensor of Murakami et al. which was originally proposed for creep failure of metal-like materials. In this paper, the concept is extended to the rate-insensitive rock mass behaviour involving joint sets. An in-situ observation method of the damage tensor is proposed.

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This paper deals with a method of monitoring the stability of underground openings during the construction. The method is based on the interpretation of displacements measured in the field. The strain evaluated from measured displacements is compared with the critical strain of materials. If the occurring strain is still smaller than the critical strain, the stability of openings is guaranteed. Normalized initial stress is used for determining the strain distributions around the openings. Back analysis plays an important role for obtaining the normalized initial stress from measured displacements. In order to make a quick interpretation of field measurements, microcomputers are generally placed at construction site so that the back analysis can be performed right after taking measurements.
In this paper, the mathematical formulation of the back analysis for the use of microcomputers is shown together with some results of case studies.

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The mechanical efficiency of a thin flexible tunnel support system such as shotcrete lining and rock bolts is investigated on the basis of experimental works. At first, model tests of tunnel excavation in which shotcrete lining and rock bolts were simulated by thin papers were carried out in a dry sand ground. As the results, it is found out that even if so flexible thin paper closed ring lining has a remarkable effect on the tunnel stability and that the effect of rock bolts appears only when they are placed to get into the outside of a plastic zone developed in the surrounding ground. Secondary, a circular tunnel excavation was simulated by shrinking a metal ring in an aluminium rod mass and the development of a loosened zone in the ground due to tunneling was discussed.

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The construction of a new expressway in mountainous areas requires cutting off slopes and crossing over desolated valleys throughout the areas. For the purpose of rational design and performance of such a road, a considerable amount of information has to be acquired on the nature of the terrain through which the road will be built. This paper discusses the value of using the remote sensing technique for geomorphological and geological surveys recently undertaken for a highway in Kyushu district, southern part of Japan. Remote sensing data used for analysis were obtained with a multispectral scanner (MSS) on board an airplane. These data are analysed both analogly and digitally in comparison with results from interpretation of aerial photographs and direct reconnaissance surveys.

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In the field of small-diameter tunnelling, one of the biggest factors standing in the way of the realization of constructing long span and curved tunnels has been the difficulty of measuring the horizontal position of a tunnelling machine. This paper describes a mesurement method which emits a magnetic field from a coil in the tunnelling machine and detects the source of the transmission by the use of two search coils. A 90-meter long tunnel with a 200-meter radius of curvature was constructed, and it was confirmed that the horizontal position found by this method is accurate to a certain specified centimeter. These results indicate the utility of this simple and precise horizontal position measurement method for tunnel construction work.

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A method for predicting surface failures which occur during heavy rainfall on granite mountain slopes is proposed by using the digital land form model that is obtained by reading altitude on a topographical map at 10m grid point space. A depth of a potential failure layer is assumed at each grid point. In the layer, an infiltrated water movement from cell to cell is modeled in the study (cell is a square of the grid). Infiltrated ground water levels which show the three dimensional effects of a topographical factor in an area can be hourly calculated at every cell by the model. The safety factor of every cell is also calculated every hour by the infinite slope stability analysis method with the obtained infiltrated ground water level.
Failure potential delineation is defined here as the time when the safety factor becomes less than unity under the assumptions that the depth of the layer is 1.2m and effective rainfall, 20mm/hr, continues 50 hours. More hazardous cells are found to appear at the sites where mountain slope failures occurred in the past time.

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A method of coupling a boundary element method (BEM) with a finite element method (FEM) is developed to analyze three dimensional elasto-plastic problems of tunnels in infinite ground.
In the proposed method, FEM handles construction sequences and elasto-plastic behavior of the ground surrounding a tunnel, and BEM which is applied to the infinite elastic region takes into account boundary conditions at infinity.
By performing some coupling analyses, the following conclusions are obtained. (1) The coupling method is shown to be a reasonable one in the problems with infinite region. (2) Economical coupling analysis of tunnels can be performed by considering geometrical symmetry proposed here. (3) In an elasto-plastic coupling analysis, it is not necessary to make stiffness matrix of BEM region repeatedly. (4) Applicability of the coupling method to tunnel problems is confirmed.

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The earthquake observation has been carried out at Ochiai semi-underground hydroelectric power station installed in a cylindrical pit of 15m in diameter, 22m in depth in rock mass in purpose of evaluating the earthquake resistance of semi-underground nuclear power plants. The behavior of the cylindrical pit has been analysed mainly by the observed seismic waves of the near field strong earthquakes, which happend in August, 1983. And some of the obtained results are as follows.
(1) Rations of subsurface maximum accelerations to surface maximum accelerations were almost in range from 1/2 to 1 in radial direction and 7/10-1 in vertical direction.
(2) The power spectrum in high frequency domain of more than 8Hz in radial direction and more than 11Hz in vertical direction decrease according to the depth from the ground surface.

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Recently attension is being directed toward developing a numerical procedure whose objective is to determine a set of parameters from a set of observed displacements at the field. The procedure, so called “Identification or Inverse” problem, is general and can be applied to any geotechnical problems, in which the system parameters are to be identified. In this paper, the method to identify the elastic constants and geometry characteristics of inhomogeneous rock masses is presented. Elastic parameters are calculated by the optimization process in mathematical programing. Geometry characteristics are determined by Akaike's information criterion (AIC) which estimates the maximum likelihood of the system. Several examples of tunnel problems with loosend area are examined and evaluated by the proposed method.

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Mononobe-Okabe's equation has been proposed in 1924 and has been used for the aseismic design of the retaining wall, today. But it is well known that the effect of cohesion is not considered in this equation.
Author measured a resultant force and a distribution of seismic earth pressure acted on a movable model wall, using a shaking table test. Sand used in the tests is slightly cohesive. The test results were discussed by the comparison with the theoretical results proposed by S. OHARA in 1960.
Also, we try to verify the base sliding of the gravity type quay walls which were occured during the earthquakes by our theoretical results.

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During an earthquake, the induced inertia forces alternate in direction and magnitude numerous times. Thus, the factor of safety may drop below unity several times which induce some movement of the failure section. So, the overall effect of an earthquake acting on a slope is thus the cumulative displacement of the failure section. If the calculated displacements are sufficiently large, the slope is considered to have failed. The minimum factor of safety only exists transiently, thus, the stability of slopes should depend on the cumulative displacement developed during an earthquake. Herein, on calculating the factor of safety of a slope for a given earthquake shock, the effects of earthquakes on the displacements of a slope should be assessed. Incidentally, this is done based on the concept of Newmark.

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A series of undrained triaxial compression and extension tests with pore water pressure measurements were performed on undisturbed samples of fibrous peats, which were normally and overconsolidated under isotropic stress condition. Test results indicate that void ratio vs. effective pressure relationships during isotropic compression and swelling can be approximated by the straight lines on Δ1n e-Δ1n p′ plane, and that stress-strain behaviour and strength parameters, c_u/p′₀ φ′, c′ are strongly affected by fabric anisotropy and stress history. Based on the test results, the authors proposed a method for predicting stress-strain behaviour of normally consolidated peat under triaxial compression and extension conditions. Moreover, the method, by which the values of undrained strength parameters of overconsolidated peat by using the test data on normally consolidated peat can be estimated, was shown and the validity of the method was verified by the test results.

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To obtain basic data served to the field measurements and the design methods of sandy ground tunnels, a series of laboratory model tests and two different types of finite element analyses were performed. In the case of shallow overburden, large displacement took place even at the ground surface, while the larger displacement zone reduced its size when the overburden became deeper. The use of joint elements in the analyses was found to be more effective than of usual elasto-plastic elements to describe the discontinuous movements occured in sandy ground due to tunneling.

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Deformation modulus E_V of sandy deposits subjected to vertical loading was estimated in connection with the use of pressuremeter. The deformation modulus E_PM measured by using pressuremeters was related to the deformation modulus E_V backcalculated from the in-situ plate loading tests and from the monitored settlement of structures. In order to ensure the E_V-E_PM relation, triaxial tests and miniature pressuremeter tests on sand specimens in triaxial chamber were conducted, as well as the plate loading tests and miniature pressuremeter tests both performed on/in artificially prepared sandy deposits. The ratios E_V/E_PM obtained from the backcalculation of the field data and obtained from the laboratory tests were found to be related to the SPT blow count N in a similar manner.

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Recently, the stability of slopes during earthquakes has become to be an important engineering problem, especially in case of the earthquake-proof design of nuclear power plants. But, for fissured rock slopes, some problems are remained unresolved, because they can not be treated as continua. The authors have been investigating toppling failure of slopes, from a point of view which regards a fissured rock mass as an assemblage of rigid blocks. DEM (Distinct Element Method) proposed by Cundall (1974) seems to be very helpful to such a investigation. So, in this paper, the applicability of DEM to toppling failure of slopes is examined through the comparison between DEM results and theoretical or experimental results using 3 simple models.

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This paper describes the geotechnical properties of highly-moistured wastes discharged from several plants, and also describes a new method for the rapid dehydration by which the wastes become easy for the geotechnical processing. The samples tested are red muds, white muds, and sludges from a filtration plant. Consolidative and shear characteristics of these wastes are comparably discussed with those of clays and high organic soils. For the rapid dehydration, a bottom drainage method is examined at field using a polymer grid container of 5m diameter and 1m depth with the filter fabric at inside wall and bottom. Field test results prove the bottom drainage method to be very effective for the rapid dehydration of the highly-moistured wastes.

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The two-dimensional consolidation of a cross-anisotropic clay deposit is theoretically examined. Based on the Biot theory (1955), the solutions of the consolidation settlement and of the excess pore water pressure are presented, although certain constraint relationships of elastic parameters are imposed. Some results of calculation are shown and the characteristics of consolidation are discussed to assess the influence of soil anisotropy.

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