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.
What is good about the abstract?
- This abstract is reasonable for a second year undergraduate report.
- It states what kind of flow net is being drawn i.e. for flow through an idealised earth dam
- It states what kind of permeameter test is being carried out i.e. falling head permeameter test
- It states that the tests are carried out on the same material i.e. the earth dam material
- The conclusions are acceptable and are stated clearly.
How could the abstract be improved?
- The first and most important requirement is to have a good understanding of the subject matter and the aims of the experiment. Note that the purpose of these tests is primarily to demonstrate how abstract theory actually works and this is not really addressed in the example abstract.
- Language has to be more precise. Insufficient care has been taken over the meaning of words, phrases and sentences and this is unacceptable in engineering practice where precision and detail are important. For example : The statement of results needs to be more precise and detailed:
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.
- The abstract could be more concise. For example, the first paragraph could be rewritten as follows with half the number of words:
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.
- A statement about the limitations of the results should be made. For example:
The accuracy of these calculations is shown to depend on both good experimental technique and the validity of the assumptions in the theory.
- The conclusion should make a clearer statement about the value of the theory, such as:
The flow net theory is shown to provide good estimates of the variation of head, the flow patterns, and the flow quantities.