The problems of predicting the dynamic peak pressures during mass flow have been investigated. In a portion of a vertical-sided silo, the stress fields adjacent to a wall have been derived by the observation of a flow pattern which shows simultaneous yield within the solids layer along the wall. An equation on the local passive yielding is presented in order to predict the peak pressures.
Measurements of the wall pressure show that the equation predicts accurately the maximum peak pressures. In a portion of a convergent hopper, the stress condition during emptying has been examined by measurement of the static rearranged wall pressure distribution after flow, and the dynamic surcharge for the transition to be emplyed is predicted experimentally.

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The fundamental equations of the dynamics of granular materials has been considered for adhesive forces due to liquid surface tension which act between grains and for the other kinds of adhesive forces which act between grains. The following conclusions have been deduced:
1) The force distribution around grains is ellipsoidal with the principal values P_J=T+3σ_J/(2rΛ), where J (=I, II, III) denotes one of the directions of the principal stress axes, T the adhesive force between grains due to liquid surface tension, (σ_J) the principal stress, r the mean radius of grains, and Λ the number of contacts within unit volume. The stressstrain equations are given by substituting this P_J for that in the known equations.
2) The adhesive force between grains T which is due to the liquid surface tension is given as follows:
T′₀=2πrs (cosφ-√α/2)
α=(C₁ρ_a/2πλρ₁)^1/2
T=T₀ [1-w/(α′γ)], α′=α(cosφ-√α/2)/(cosφ-√α/8)
where w denotes the displacement between the adjacent two grains, which must be small, and s denotes liquid surface tension, C₁ the weight ratio of liquid to the total granular mixture, ρ_a the apparent density, ρ₁ the liquid density and λ is equal to r³ Λ.
3) The Mohr failure envelope is given by
(σ_I σ_III)/(σ_I+σ_III+2σ_T)=sinΘ
where σ_I and σ_III denote the maximum and the minimum principal stress (positive in compression), respectively, and σ_T is given by (2/3)γΛΤ.
4) When an adhesive force the strength of which is f_t per unit area acts between grains in a tangential direction, the condition of slip is given by the following expression:
[1/2∑_J∑_K(P_J-P_K)²cos²η_Jcos²η_K]^1/2>2πrf_tb_m(∑_JP_Jcos²η_J)^1/m
where J or K (=I, II, III) denotes the principal stress direction, and η_J denotes the angle between the J-direction and the normal at the point where the force acts on the grain surface.

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Direct consolidation of α- and β-Si₃N₄ is conducted by the use of one-dimensional explosively shocked treatment. The effect of shock pressure, phase and particle size distribution of a sample powder on the characteristics of explosively shocked compact is examined by the measurement with X-ray diffraction (XRD), Electron spin resonance (ESR), Infrared absorption (IR) and so forth. The following is the results induced:
1) Cracks exist in the shock compact. The apparent density and Vickers hardness increase with the increase in shock pressure. A compact of ca. 90% theoretical density is obtained.
2) Residual strain by XRD and spin density by ESR is reduced under higher shock pressure. This is considered to be attributed to the relaxation effect of high residual temperature. The shock compact of α-Si₃N₄ receives more residual strain and spin density than that of β-Si₃N₄.
3) The effect of the particle size distribution of sample powder on the characteristics of shock compact is slightly present. The shock compact of larger particle size has more residual strain.
4) Metal impurities are not found except in the surface layer of the compact.
5) The solubility of the powder grinding shock compact in 1N NaOH is higher than that of the as-received powder. This indicates that an active surface layer exists in the shock compact.
6) The tapping density of the powder grinding shock compact is much higher than that of the as-received powder.

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