This paper describes the geotechnical properties of normally consolidated Fao clay distributed at the mouth of the Shatt Al-Arab in southern Iraq.From test results, the following important geotechnical characteristics of Fao clay were obtained. Fao clay is seriously disturbed in structure by 1) the stress release during sampling and 2) the redistribution of water in the sample during sampling and trimming. The effect of the latter is considerably greater than that of the former. However, the undisturbed structure in the field may be restored when the sample is reconsolidated under the same stresses it carried in the field. To ensure the complete restoration, consolidation loads must be applied in small increments.The paper also describes the following geotechnical properties of this clay : 1) determination of the undrained strength for practical purposes, 2) anisotropy in strength, 3) strength decrease due to rebound and 4) consolidation characteristics.

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This paper describes the geotechnical properties of Khor Al-Zubair clay distributed along the old river channel of the Shatt Al-Arab River in southern Iraq.In-situ and laboratory tests indicated that Khor Al-Zubair clay is an overconsolidated clay with overconsolidation ratio decreasing with depth. The following two were suggested from an analysis of the various tests results : -1) The overconsolidation state of Khor Al-Zubair clay was not caused by geologic stress release but may be caused another factors such as aging effects, dring, seepage forces.2) Overconsolidation resulting from factors such as aging effects, dring, seepage forces tends to decrease rather than increase the value of K₀.The paper also describes the following geotechnical properties of this caly; 1) undrained strength, 2) anisotropy in undrained strength and 3) strength decrease due to rebound.

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Penetration resistance of standard penetration test is examined in relation to the in-situ relative density determined from sand sampling. Tests have been carried out at the site of Ogishima Island where was lately reclaimed with pit sand. The results are compared with the one obtained by Gibbs and Holtz based on laboratory tests. An influence of lateral stress on blow counts is further studied on the basis of in-situ tests. They have been conducted on improved ground where received a vibratory compaction. Studies on virgin deposits show that a condition of deposition exerts a considerable influence on penetration resistance. Deposits below sea level show a little smaller resistance than the one estimated from the results of Gibbs-Holtz under the same relative density. An average relation expressed as N^^-=(22σ_v'+6)D_r² is found out. But this relation cannot be applied to deposits above sea level. The average blow count N^^- is smaller at any depth than the blow count of highest frequency N_p irrespective of the condition of deposition. The difference between them is about 2 or 3.From studies on improved ground, it is shown that the penetration resistance increases considerably through compaction. Its increase could never be explained by only the increase in relative density if the relation obtained above is utilized. Hence, the relative density evaluated from blow counts becomes far higher than the actual one. This misleading is considered to result from the increase in lateral stress. Results of pressuremeter tests before and after compaction reveal an actual increase in it. The penetration resistance is, hence, promised to receive an influence of the increase not only in relative density but also in lateral stress.

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To clarify the water loss mechanism of clayey fluid mud, one-dimensional forced water loss tests have been carried out. Based on the measurement of pore pressure and of water content within a specimen, it is concluded that the water loss is governed by the filtration mechanism. Although the theory of filtration was already proposed by Carman, the authors have formulated a simple theory on the basis of presently clarified mechanism. It is expressed by the variables familiar to soil engineers. New theory ignores the consolidation process which proceeds in a specimen, but a well-grounded method to take this effect into consideration is proposed. It is revealed that the theory should be applied only for the initial water content higher than a limit one. This limit water content is lower for the higher applied load. The theory promises that; 1) the water loss proceeds in direct proportion to the square root of time up to the time necessary to the sufficient water loss, 2) this time increases with the second power of the initial specimen's thickness, and 3) the specimen's thickness gives no influence on the water loss velocity. These theoretical predictions are all confirmed by test results.

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The Paper gives an interpretation in terms of the influence of a loading duration on the results of such one-dimensional consolidation test as conducted under the condition of a larger increment ratio, say 1.0. Based on the records of consolidation tests including measurements of both pore-water and total pressures, the role of the adsorbed moisture film with which clay particles are coated or the bonding of those is inferred and the concept of a film bond is introduced. A theory of consolidation is developed with incorporating it. The numerical solutions are presented. It is theoretically shown that such an increment duration as to produce considerable amounts of secondary compression causes the retardation of consolidation. This theoretical result is compatible with that noted and described by numerous observers. Consideration is made of the engineering significance of the parameter β which is introduced for the purpose of a convenient use of the present theory. In addition, the quantitative applicability of the present theory is verified by comparison with the theoretical and the empirical consolidation curves.

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