Author : Christopher Bondi Pickles
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (56 download)
Book Synopsis Hydraulic Classification of Unsaturated Nonwoven Geotextiles for Use in Soil Structures by : Christopher Bondi Pickles
Download or read book Hydraulic Classification of Unsaturated Nonwoven Geotextiles for Use in Soil Structures written by Christopher Bondi Pickles and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Due to the great success of geosynthetics and the ever increasing variety of available products, classification of the polymeric materials has fallen behind their numerous applications and wide use in practice. The behavior of nonwoven geotextiles while in unsaturated conditions is one example of an area where information is lacking. Geotextiles are often incorporated in engineered structures including landfill liners and covers, earthen dams, retaining walls, and roads to perform the separation, filtration, and/or drainage functions. Although the materials perform well when saturated, this condition is often not realistic in many of these systems. Moreover, under unsaturated conditions, a capillary break will often form at the interface between the soil and geotextile. If a capillary break is unaccounted for in a system design, the resulting build-up of moisture may have negative effects on the performance of the structure. Properly designed geotextile capillary barriers, on the other hand, have the potential for many positive applications. In order to understand the hydraulic behavior of geotextiles under unsaturated conditions, several methods used to determine the geotextile water retention curve were evaluated in this study. Two different test setups, the modified capillary rise and the modified hanging column, where then constructed and used to study the retention function of geotextiles in the in-plane and cross-plane directions, respectively. Based on the properties of the geotextiles and a fine grained soil used in this study, predictions were made about the formation of a capillary break in the soil-geotextile system. Eight small column tests where then conducted to simulate a capillary barrier, measure its storage, and verify the experimental predictions involving the geotextile water retention curve. The testing program provided insight to the unsaturated behavior of nonwoven geotextiles and the materials ability to impede moisture flow in unsaturated conditions. Whether a result of differences in the testing methods used, surfactants applied during manufacturing, or anisotropy in geotextiles pore structure, the nonwoven geotextiles tested in this study experienced variations in air and water entry suctions when tested in the cross-plane versus the in-plane direction. Additionally, the four nonwoven geotextiles were found to experience increased air-entry suctions when fine grained soil was retained on and impregnated in the material or when subjected to a normal load. Thicker geotextiles were found to provide more resistance to impregnation with fines. Due to the low water entry suction of a nonwoven geotextile, when a geotextile and a fine grained soil are placed in contact with each other under unsaturated conditions, the interface of the two materials may create a capillary break that is capable of preventing moisture flow until the soil adjacent to the geotextile is nearly saturated. Furthermore, the small range of water-entry suctions found in geotextiles makes classification for performance based selection of different geotextiles in a capillary barrier system irrelevant, i.e the geotextiles are very similar and one geotextile does not seem to outperform another in a capillary barrier application.
