9700186 This research will develop an understanding of the role of geomembrane surface roughness on interface behavior. Through a comprehensive experimental program using the recently developed and implemented Optical Profile Microscopy technique to provide quantitative measures of geomembrane surface roughness, it is expected to provide a more rational basis for selecting design parameters and predicting the long-term behavior of composite systems with geomembrane interfaces. A custom interface shear apparatus will be made for this research, and testing will include measurements of the distribution of local void ratio in the interface region using a recently developed resin impregnation - image analysis procedure to provide insight into fabric and porosity evolution during shearing. The experimental studies will be complemented with appropriate analytical studies. The quantitative measures of geomembrane surface roughness and local void ratio distribution in the interface region will permit the interface strength behavior to be examined within the context of state. Within this unifying frame understanding, it is expected that small changes in state as shearing progresses can be related to the physical characteristics of the geomembrane surface. Numerical simulations will be performed to study a range of interface conditions and explore optimal roughness designs for mobilizing interface shear. ***
