| The focus of this thesis is to study the potential of internal drainage materials for geosynthetic reinforced earth walls. In addition, design methods for such internal drainage within the reinforcement soil zone of geosynthetic reinforced earth wall were also developed. In order to analyze the behavior of internal drainage and seepage flow rates finite difference methods are employed. Major parameters considered are the existence of front drainage, in-plane permeability of the geosynthetic (typically a needle punched nonwoven geotextile), permeability of reinforced/retained soil, geosynthetic length/wall height ratio, wall height, geosynthetic spacing, and backfill inclination. Various conclusions were drawn with respect to the factors mentioned above.; Transmissivity testing with foam as superstrate and substrate was performed on potential products for the purpose of providing data for analyses and design. The tests, short-term and extended-term tests (100hr), are based on ASTM D4716. During both types of testing, the ultimate flow rate and transmissivity of each product was measured.; Two alternative design methods of internal drainage in geosynthetic reinforced earth walls were developed; one is design by seepage flow rate and the other is design by total seepage force. Internal drainage design by seepage flow rate assigns actual drainage to the geosynthetic in the system while comparing required and allowable flow rate at each potential drainage geosynthetic location. Internal drainage design by total seepage force determines the optimal solution for internal drainage of geosynthetic reinforced earth walls while comparing hypothetical total seepage force and actual total seepage force at the end of reinforcement geosynthetic by using simulations.; Using the results of these two design methods, the number of drainage layers required by total seepage force method is generally equal to or less than by seepage flow rate method. However, both methods show potential over the existing approach of assuming uniform drainage within equally spaced layers. Optimal design approaches using example problems are included. |
