Impact of Extent of Wetting in Arid Region Geotechnical Practice

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9612073 Houston Eight of the ten fastest growing cities in the U.S. are located in the arid or semi-arid regions of the southwest. With the expected growth, there is a need for supporting infrastructure including surface and subsurface structures. For civil engineers, there is also a growing appreciation for the different mechanical behavior of arid soils, including problems with soil expansion, collapse, and wetting-induced slope instability. Some of the associated failures can be catastrophic. Recent evaluations of existing unsaturated flow models demonstrate that, although rates of infiltration can be simulated fairly accurately with appropriate model calibration, the degree of saturation and the in situ stresses are not well predicted. This research addresses the need for improving arid-region geotechnical practice in estimating the degree and extent of wetting, and quantifying the effect of that wetting on soil behavior. The result of work will include practical design envelopes of degree and extent of wetting, allowing the assessment of changes in saturation due to urbanization or increased irrigation. The multidisciplinary team includes PI's from geotechnical engineering, construction, and geology. The methodology includes: (1) large-scale, deep field lysimeters, (2) collection, analysis, and presentation of the extensive existing geotechnical and geoenvironmental data assembled from reported information and practitioners files, and (3) unsaturated soil testing for shear strength and compressibility in response-to-wetting, including pore-air and pore-water pressure control and measurement. ***