The paper describes a procedure for the evaluation of the effect of tensial strength on stability of slopes. The procedure is based on variational approach to limiting equilibrium problems. Based on this approach it was found possible to estimate the depth of tension cracks, and their effect on slope stability in a consistent manner. Formulas and charts which enable the determination of the depth of tension cracks and stability number for every combination of slope angle, mobilized friction, and tensial strength are given.Based on this analysis the following conclusions may be presented : a) The maximum depth of tension cracks is 25% of the slope height, and this value occurs for vertical slopes.b) The increase in stability number (decrease in critical height), which corresponds to a maximum crack is of the order of 20%. This is valid for cracks which are not filled with water.

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The disaster due to the slope failure at the heavy rainfall is one of the most important social problems in the mountainous countries like Japan. The object of this study is the relatively shallow slope failure in the surface soil layer of the slope, since this kind of slide occurs very frequently at the rainfall. There are two approaches to prevent or decrease the disaster : One is to perform the mechanical defensive works such as a retaining wall and the other is to find out the good prediction method of slope failure in order to minimize the damage. It is well known that the measurement of deformation and pore pressure of a slope is very effective for the prediction of slope failure, but it is practically impossible from the economical and technical aspects to measure these factors for a very big number of steep slopes during the heavy rainfall. From this viewpoint, the authors developed the new prediction method of slope failure by using the probability of failure in which only the rainfall intensity is needed as the information during a rainfall.The present paper firstly shows the validity of this method based on many analytical results for the actual failure and the non-failure slopes and after that the mechanical significance of the probability of failure which is just only a conceptional index is verified by the laboratory and the field experiments.

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The purpose of this study is to facilitate the analysis of the multi-dimensional consolidation subject to a certain condition. As well-known, consolidation is expressed by the heat conduction type equation taking the volmetric strain as an unknown, to which no boundary condition can be generally given. But in case of irrotational consolidation, a boundary condition can be given to the volmetric strain by introducing a consolidation potential. Also, in case of irrotational consolidation with the consolidation load being constant, consolidation can be expressed by the heat conduction type equation using an unknown consisting of an excess pore water pressure and the average excess pore water pressure. Also, in this case, the boundary condition can be given to such an unknown by introducing the consolidation potential. This paper describes the above concept and gives the rigorous solution of consolidation of a cylindrical clay with radial external drainage of water by applying such concept.

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The reliability of geotechnical structures of short-term stability is largely affected by uncertainties contained in measured undrained strength of soils. The main sources of the uncertainties are (1) the inherent random variation of soil property in the in-situ ground, (2) stress release in boring, (3) mechanical disturbance during sampling and trimming of soil specimen, and (4) testing errors. These uncertainties are modeled in probabilistic manner and a new probabilistic model of measured undrained strength is proposed for normally consolidated and or lightly overconsolidated clay. The proposed model is attested by some actual data, and it is concluded that the proposed model can well predict the statistical parameters of in-situ undrained strength on the basis of those of the measured undrained strength.

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In this paper the probability theory is applied to analyse the motions of particles in a particulate material and the mechanical model for particulate material is established. In modelling, the motions of particles are regarded as the Markov process which is one of the well-known stochastic processes. In this model the contact angles formed at contact points of particles are adopted as random variable. The basic equation of the two dimensional Markov process is derived and applied to the mechanical behaviours of particulate material. Furthermore, the strains are defined for particulate material and derived by using probability density function of contact angles and the discontinuous motions of particles at contact points.

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It is generally understood that there exists a hysteresis loop between the normally consolidated and overconsolidated effective stress Mohr-Coulomb-failure envelopes, the size of hysteresis loop being a function of the past maximum consolidation pressure. Research findings of different investigators in this regard are at variance. This paper presents the results of an experimental investigation on two remoulded clays in (CIU)^^^- compression tests, varying both maximum past consolidation pressure and the overconsolidation ratio. Test data is analysed in terms of Mohr-Coulomb as well as Hvorslev failure envelopes.Test results show that the effective stress Mohr-Coulomb failure envelopes are uniquely defined independent of overconsolidation ratio, past maximum pressure and the failure condition such as the peak deviator stress, peak effective principal stress ratio and the peak porewater pressure. When the failure is denfined at a strain level lower than that of the peak stress condition, unique effective stress parameters (c' and φ') equal to the peak stress values are observed at pre-peak strains (ε_a≃6 percent) even bofore the peak stress conditions are reached (ε_f≃15 percent). From the view point of Hvorslev criterion, the shear strength of the two remoulded soils is essentially through φ_e' and it is independent of maximum past pressure.

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In this paper the shearing mechanisms for particulate material are investigate at the particle scale. Then, the coefficients in the basic equation of Markov process, which has been explained in the previous paper (Kitamura, 1981), are quantitatively evaluated by introducing the concepts of the potential barrier and the potential slip plane. It is revealed that these concepts play important roles for the investigation of shearing process of particulate material at the particle scale. The values of these coefficients can be obtained by using the energy transferred into or out the particulate material, the initial void ratio, the grain size distribution, the coordination number and the frictional coefficient.

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The countermeasures to ground vibrations generated by car traffic are summarized and among them the detail of the soft ground improvement is described in this paper.The field tests and the finite element analyses were performed on the reduction of ground vibrations by soft ground improvement. At the field tests the ground was improved at region of 20 m in width, 30 m in length and 12 m in depth by lime pile method and the ground vibration test was conducted by using a vibration generator.The finite element analyses were carried out to confirm that the finite element technique is useful to treat the surface wave propagation problem and to develop a prediction method of the reduction of traffic-induced vibration by improving the soft ground.The following conclusions were obtained : i) The improvement of soft ground is effective to reduce the traffic-induced vibrations. The reduction of ground vibrations were observed in the frequency range less than 10 Hz. ii) The width of the improvement area has small influence and the depth of the improvement area and the ratio of rigidity before and after improvement have large influence on the reduction of ground vibrations. iii) The predominant frequency of the ground was slightly increased by the construction of lime piles in the ground. iv) The calculated acceleration by the finite element analysis well agreed with measured values of the field tests. Therefore it is possible to simulate the ground vibration generated by a dynamic load on the ground surface by the finite element analysis. v) The reduction of traffic-induced vibrations can be evaluated by using a prediction figure presented in this paper.

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The effects of confining pressure on the cyclic undrained triaxial strengths of intact sandy specimens obtained by sand sampling methods were investigated. It was found that the ratio of cyclic deviator stress amplitude to initial confining pressure required to cause a certain value of cyclic axial strain amplitude at a certain number of loading cycle in an intact triaxial specimen increased significantly with the decrease in confining stress when the laboratory confining pressure was less than the in situ confining pressure. However, it was also found that cyclic undrained triaxial strength expressed by stress ratio decreased only slightly with the increase in confining pressure when the laboratory confining pressure was larger than the in situ confining stress.

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The rate of evaporation of water in a burette and the compressibility of filter materials used as side drains are examined among experimental problems in the usual procedure for the measurement of volume change of cohesive soils in drained triaxial tests. The effects of change in room temperature on the measured volume change is also investigated and discussed.The compressibility of a filter paper is found to be a more important factor than others because no one can avoid the effect especially in drained triaxial tests with varying cell pressure. The compressibility of a filter paper, however, can be evaluated; a way to evaluate it is proposed by finding a linear relation between the volume of water drained from the filter paper and cell pressure in log scale for the rebound-recompression portion obtained from compression tests of the filter paper in a triaxial cell.

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