By using a simple rectangular frame in which steel balls of equal diameter were placed in one layer, bi-axial compression tests were carried out to observe the influence of grain-to-grain friction on the shear phenomena of a granular material. Since the distribution of the void ratios was considered important, photo-cells were used to measure the void ratios at many points within the steel ball layer. The average value and the variance of the void ratio distribution which changed with shear were computed and were compared among the results obtained for various densities of steel ball packing. A series of tests were conducted on steel balls with rough surface and those with smooth surface. The difference in the behaviors of these two kinds of steel balls was studied in terms of the difference in the surface roughness. The results obtained were discussed in connection with the theory proposed previously by the senior author.

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This is to introduce some soil-mechanical aspects of some recent major shield-driven tunnels excavated by the pneumatic method through very soft clays in Tokyo and Osaka for underground railways. The two important points discussed herein are the air pressure reqired for supporting the exposed cutting face and the settlement of the shield and the ground due to weakness of the soil supporting the shield.

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This paper deals with the effect of water content on shearing characteristics of granular soils such as Shirasu by means of drained triaxial compression tests on the compacted specimens having different water contents. It is clarified in this study that apparent cohesion and angle of shearing resistance are affected independently by water content, and the parameters for shearing strength vary with confining pressure. The decrease in shearing strength with an increase in water content seems to be caused by a decrease in the portion of strength contributed by interlocking of particles. As dilatancy decreases with an increase in water content, the critical void ratio decreases correspondingly with an increase in water content.

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The significance of shear strength increases on the allowable preload rate for compressible, normally consolidated soils subjected to a flexible strip load is examined. On the basis of representative soil parameters and various assumed boundary conditions, a computer analysis has been made to systematically predict the rates and magnitudes of shear strength increase and the associated settlements which occur as primary consolidation progresses, and to evaluate the bearing capacity of the soil in terms of these strength increases. Results show that, when adequate drainage is provided, weak soils may be expected to experience a measurable increase in bearing capacity during the consolidation process; furthermore, these increases occur in a time which is compatible with many construction schedules. On the other hand, when drainage is inadequate, slow rates of consolidation preclude the occurrence of any reasonable bearing capacity increase, except for cases where the ratio of the horizontal to the vertical coefficients of consolidation is large. Since consolidation settlement at any given time is governed by the magnitude and duration of the applied load, which is, in turn, governed by the rate of bearing capacity increase, the resulting consolidation settlements can be accelerated to any worthwhile degree only for cases where reasonable bearing capacity increases are experienced. Finally, the benefits of optimizing the preload rate decrease significantly for cases where the initial soil strength is high.

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