The impact phenomenon of a falling rock to sand layer was examined and compared with experimental results. Five model weights with different weight, size and bottom shape were used in the experiments. The equation of motion of the weight was expressed by a free vibration of a mass with viscous damping. The viscous term was determined so that the caluculated impact acceleration of flat bottom weights coincides with experimentally obtained value. The restoring force was assumed to be given by a plastic bearing capacity theory of a shallow circular foundation. The calculated acceleration time history and maximum penetration of the weights showed a good agreement with measured values in the experiments.

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Participating in a construction work on a very soft clay ground, the authors had to know the availability of the slurry-trench method in the clay ground. Therefore, they excavated three trial trenches to see the cases of unstable, critical and stable conditions of the trenches in the clay. Based on these trenches and investigation of clay at excavated places, they found that the stability of slurry-trench in the clay ground could be judged with the degree of consolidation of clay. The clay ground of overconsolidation ratio equal to or greater than 1.0 can support a slurry-trench stably. This judgement was checked and discussed with a slurry-trench in another site measuring the deformation and the pore-water pressure of clay ground.

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One of the significant problems occured in the excavation of hard rock mass is structural failure caused by falling or sliding of blocks defined by intersecting structural discontinuities. It is believed that it will be the effective method against structural failure to forecast the existence of keyblocks prior to the excavation. to search and then to support such keyblocks right after the excavation, This paper is to explain how to forecast the shape of keyblock and to calculate required supporting force by utilizing stereographic projection method of computerizing when the data of discontinuities in rock mass are obtained.

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Presented is a simplified procedure for performing the dynamic effective stress analysis. The proposed method is an extension of the method of equivalent linear dynamic response analysis which has been used in the total stress analysis. It is assumed, in this method, that the variations of the shear modulus and damping factor due to the magnitude of strain and reduction of effective stress are independent each other. That is, at first, the total stress analysis is done in order to obtain the shear moduli and damping factors corresponding to the specified strains, called effective strains. Secondly, the effective stress analysis is carried out and the modui are varied due to the variation of the effective stress only. In this way, by applying the simplified stress-strain relation to the effective stress analysis, it becomes possible to reduce plenty of calculating time of the effective stress analysis.

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Engineering classification of residual granitic soil in Kaduna district, Nigeria, is clarified on the bases of geochemical, geomechanical and statistical studies.
Geotechnical properties of each soil layer are investigated by performing analytical procedure of perticle size distribution, porosity, N-value and chemical composition. The degree of weathering of the parent rock which belongs to tropical savanna zone is discussed in this paper comparing with the characteristics of residual soil derived from granite in Japan.

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Three categories of techniques are employed in order to estimate the deformation/strength parameters of subsoils based on the data obtained from vane and pressuremeter tests: (1) theoretical procedures to convert the results of vane and pressuremeter tests into the deformation/strength parameters are proposed. (2) the deformation/strength parameters of clayey soils are derived from an elasto-plastic constitutive model. (3) deformation/strength parameters are estimated from lab/field tests through empirical equations. The use of these three categories of techniques in a number of construction sites gave an idea of applicability and limitations of using the soil parameters obtained from vane and pressuremeter tests in the deformation and stability analysis.

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The purpose of this paper is to explain the shear behavior of sand under various three-dimensional stress paths. In the stress-strain model under shear proposed here, the direction of strain increments is analyzed by considering the sliding mechanism on a spherical surface in the principal value space of the mechanical quantity t_ij which has been introduced to describe uniquely soil behavior in three-dimensional stresses. The magnitude of strain increments is calculated with reference to the idea by Prévost where the properties of isotropic and kinematic hardenings in plasticity are combined. The validities of this model are then confirmed by the true triaxial tests on Toyoura sand not only under radial straight stress paths on the octahedral plane but also under rotational stress paths that the direction of shear stress on the octahedral plane is changed continuously.

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In this paper, triaxial test results on overconsolidated cohesive soil with various preconsolidation pressures and overconsolidation ratios are shown which were carried out under drained or undrained condition. From these results, e-log p relationships at both peak and residual states and q-p relationships are presented. An expression on failure strength of overconsolidated cohesive soil is given which is obtained from the assumption that Hvorslev's failure criterion of soil is valid and the slope of e-log p relationship at wet side is different from the one at dry side. The validity of this idea is verified by the author's and other researchers' experimental results. Finally the relationship between the coefficients used in the present theory and the plasticity index is discussed.

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A statistical reconsideration on the parameters for geomechanics classification of rock mass has been carried out to apply them in the Japanese geological conditions.
Procedure to produce the parameters from the data base collected in conjunction with tunnel deformation and geomechanical rock conditions is reported.
Analysed results of 152 examples of tunnel excavation in the Japanese geology so far collected are compared with the weighting of classifications by Wickham, Bieniawski and Barton.
The authors concluded that the greatest weight should be placed on the thickness of tunnel overburden presented by the sectional area of tunnelling, whereas the RQD and joint condition constitute the greatest factor in the aforesaid researchers.

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A computer program was developed to design a new tunneling method using bolts and shotcrete, so-called NATM.
Combined effect of the bolts to reinforce the tunnel ground comes from reaction caused by ground displacement and maintenance of the three-demensional stress condition of ground which prevents the ground deterioration. Analysis is executed step by step with progress of excavation. Progressive deformation with stope advance is calculated using the creep function. Bolts will slide, if the axial force exceeds the shear resistance between bolt and ground. Proper model can be chosen to represent a specific case of shotcrete depending on the design objective. A slit in the shotcrete to be provided in a tunnel subjected to heavy deformation can also be modeled.

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