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Peformance of Water and Gas Pipes Buried in Reactive Soil

出版	Monash University, 2008
URL	http://books.google.com.hk/books?id=qebUXwAACAAJ&hl=&source=gbs_api

註釋Failure of buried pipes due to reactive soil movement is a regular problem for water and gas pipe networks in Australia and worldwide. Soil movement is closely related to seasonal climatic change and particularly the moisture content of soil. Large scale pipe failures are expected to occur during winter or summer when extremely hot or cold weather takes place, and the swelling or shrinkage of soil produces extra forces on the pipes. However, understanding of the correlation between pipe failures and soil movement due to moisture changes in reactive soil is not well developed. Furthermore, methods of predicting pipe deflection due to soil movement are not available. For these reasons, this research project attempted to improve the current knowledge by studying the performance of buried pipe in reactive soil. The performance of buried pipe is affected by different factors corresponding to the physical properties of the pipe and the time dependent environmental changes. Pipe diameter, age, material type, soil reactivity, failure rate and climate variables applicable to water and gas pipe networks were studied by statistical analysis to examine the relationship between pipe failures and seasonal variation of soil moisture content. Merri Creek clay was chosen for the laboratory study due to availability and was characterised to study its swell and shrink behaviour as well as reactivity. A new large scale laboratory soil box was designed to study the performance of a buried polyethylene pipe. In order to have a better understanding of the soil stresses exerted on the buried pipe, capillary rise tests, swelling potential tests and triaxial tests were conducted on core clay samples extracted from the soil box. The test results confirmed the swelling soil can induce a considerable amount of stress on the buried pipe. The deformation of the polyethylene pipe buried in the pipe box was studied during wetting of the soil from the base. The test results indicated that it is possible for the polyethylene pipe to deflect upward significantly when the soil is swelling due to increase of moisture content. A numerical procedure was also developed for predicting the deflection of buried pipe due to soil swelling. Comparative measurement of pipe deflection from the laboratory test and numerical analysis was evaluated. It was highlighted that an approximte iterative numerical procedure can be used to predict the pipe deflection in a field situation.