This paper describes the geotechnical properties, particularly the shear characteristics of a silty sand distributed at a place in the Arabian Gulf.From the tests results, following important conclusions and suggestions were obtained : (1) The silty sand is classified to one kind of the quick sand, (2) the shear strength of this sand for practical purpose is the same as that of normally consolidated clay, (3) liquefaction potential of this sand is considerably higher when compared with that of some typical sands, and (4) a silty sand with metastable structure resulting from the simultaneous deposition of sand and silt sized particles was developed under sea water.

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This paper is first concerned with the characteristics of the excess pore-water pressure built up at the moment of applying a load increment on a normally consolidated clay of some age under one-dimensional condition. A simple empirical formula by which the initial excess pore-water pressure could be estimated is developed on the basis of Bjerrum's concept. Numerical results of the formula are presented and compared with observations from oedometer tests. Successively, based on the results of comparison, some considerations are made of a preconsolidation effect and a unique relationship between void ratio and effective pressure concerning aged clays. Other characteristics of aged clays are further discussed by referring to the results of consolidation tests.

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The extraction of reliable undisturbed samples of granular soils from below groundwater table for subsequent laboratory testing, is not possible by routine sampling methods. Consequently, during investigations for major, sensitive structures founded on such profiles, alternative sampling techniques such as in situ freezing and coring or dewatering and block sampling followed by laboratory freezing and coring, have to be considered. In both procedures, the soil is frozen at some stage.This paper presents the results of a study of the effect of freezing and thawing of granular soil on its static and cyclic strength and stress-strain behaviour. It is found that freezing and thawing leads to some degradation in the soil properties, but it is still recommended that these procedures may be used to obtain conservative values of the soil properties which are more relavant than those obtained from reconstituted specimens.

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A basic method for stability analysis of the slope containing piles in a row is described, using the theoretical equation of lateral force acting on piles in a row due to plastically deforming ground, which has already been derived by the authors. Studies of the effect of many factors on pile and slope on the slope-stability are carried out for an example of the foundation piles of landing pier in a harbor and a design method is proposed for the stability analysis of the slope with landing pier.The results show that such factors as the position of pile's row, the fixity condition of the pile head, the interval between piles, the pile diameter, the thickness of the pipe pile and the slope gradient have much effect on the slope-stability. In the proposed design method, such six factors can be considered systematically. Moreover, an example is shown, in which important factors in pile design are brought out and illustrated.

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When overconsolidation is induced in a horizontal deposit of sand by the removal of surcharge pressure or by other events, the lateral deformation is prevented and the coefficient of earth pressure at rest, K₀, increases. To evaluate effects of the overconsolidation ratio as well as increased K₀-value on the liquefaction resistance of sand deposits, several series of cyclic torsion shear tests were carried out on samples of clean sand overconsolidated to different degrees under various K₀-conditions. The results of these tests were summarized in an empirical formula. This formula is used to estimate the cyclic strength of sand at any given OCR- and K₀-values, based on the cyclic strength for isotropically and normally consolidated samples.

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Extensive field and laboratory tests were carried out on an alluvial marine clay in the Tokyo Bay to grasp its undrained strength characteristics. First, a procedure for obtaining the in-situ undrained strength of the clay in the laboratory tests is discussed in the light of the fundamental properties of the aged alluvial clay. Then undrained strength and anisotropy in the undrained strength of this clay both in the field and in the normally consolidated state are reported and discussed including the effect of the strain rate on the undrained strength. Further, overconsolidated state was considered and overconsolidation ratio resulting from secondary compression and cementation was quantitatively evaluated for this clay. Finally it was suggested from an examination on in-situ vane strength tests that K₀ value of this clay is constant through depth and is independent on overconsolidation ratio.

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This report describes a measured record of earth pressure and water pressure which acted upon the perimeter basement walls of a building during an earthquake. The record was obtained, when the "Off Miyagi Prefectuce Earthquake" (magnitude 7.4) occurred on 12th June, 1978, at the alluvial formation area in Yokohama City about 380 km away from the epicenter. The number of record-taking points were 7 points for earth pressure and 3 for water pressure ; 10 points in total in the perpendicular directions. The record was taken by detecting the earthquake with an acceleration transducer and by continuously measuring and recording, from the instant when the starter was triggered, with a dynamic strain meters. From this record, the properties of earth and water pressure were found to be as follows : 1) Maximum amplitudes of the earth and water pressure Δp_E during the earthquake with respect to those p at normal times were within the range of 2.74 to 6.37 kN/m², the ratios between them Δp_E/p, were 0.011 to 0.0374, and both the value and the ratio tended to become larger when getting closer to the ground surface, 2) a long-period component of about 10 sec was observed in the individual records, 3) water pressure and earth pressure indicated properties which noticeably resembled each other.

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