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Abstract

This report describes a flow tank experiment and also a falling head permeameter test. The main aim of the flow tank experiment was to simluate the flow of water through an idealised earth dam and obtain an observed experimental and corresponding theoretical flow net. These nets were compared and measurements used to calculate the permeability of the soil in the flow tank. The permeameter experiment was used to determine the relation between permeability and void ratio for the soil in the flow tank. This relation was then used to estimate the density of the soil in the flow tank and to show how this affects permeability.

Using the flow nets, the permeability of the soil was found to be 0.027 cm/sec compared with a theoretical value of 0.028 cm/sec which represents a 5% difference. The results of the permeameter test showed a positive relation between permeability and void ratio. The dry unit density of the soil in the flow tank was found to be15.71 kN/m3. The difference between experimental and theoretical measurements is small and therefore these experimental methods are a reasonable way to estimate permeability and density. As expected, when soil density increases, permeability decreases.

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Tests in the permeameter gave permeabilities in the range from 0.01 cm/s to 0.04 cm/s as the void ratio varied from 0.6 to 0.8 respectively. The permeability of 0.028 cm/s has been used to estimate a void ratio of 0.7 and dry density of 1.6 g/cm3 in the flow tank.

This report describes an experiment to visualise the flow through an idealised earth dam and falling head permeameter tests on the earth dam material. Comparisons are made between the theoretical and experimentally observed flow nets, and equations governing flow are used to estimate permeability. Permeameter tests are used to demonstrate the relation between void ratio and permeability.

The accuracy of these calculations is shown to depend on both good experimental technique and the validity of the assumptions in the theory.

The flow net theory is shown to provide good estimates of the variation of head, the flow patterns, and the flow quantities.

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