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This paper presents the results of a laboratory study on the at-rest lateral stress and Ko of two artificially cemented sands. A modified oedometer ring was used to measure the lateral stress of cemented and uncemented sands. Test materials were No. 3 Ottawa sand and a marine sand with Portland cement. The specimens were prepared using the method of undercompaction to minimize the influence of specimen preparation on test results. The cement contents were 0, 0.5, 1.0, 2.0, 4.0, and 8.0% by the weight of dry sand. The water content of the specimens was 4% of the weight of dry sand and cement. When the sands were cured under zero confining pressure, the test results indicated the following: the at-rest lateral stress in cemented sands decreases significantly with increasing cement content; the relationship between the vertical and at-rest lateral stress is nonlinear and the value of Ko increases with increasing vertical stress; and the lateral stress decreases with sand density and curing period. When the specimens were cured under vertical stress, the value of Ko during the removal of vertical loading increased with both overconsolidation ratio and cement content. Stress history has a significant influence on the behaviour of at-rest lateral stress in cement sands. Key words : cemented sand, Ko, lateral stress, overconsolidation, stress history.

This paper presents the results of a laboratory study on the lateral stress in a vibrated sand. No. 3 Ottawa sand was tested on a snaking table providing vertical vibration, and at-rest lateral stress was measured using a modified oedometer ring. The test results show that the lateral stress in normally consolidated sand increases with vibration time. The magnitude of the increase in lateral stress is related to the density of sand and the intensity of vibration. For overconsolidated sand with a high coefficient of earth pressure at rest, the lateral stress decreases with vibration time. Stress paths of a tested specimen are also presented in this paper. Key words : sand, coefficient of earth pressure at rest, lateral stress, vibration, overconsolidation ratio, stress path.

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