CAREER: Stabilization of Earth Slopes Using Reticulated In-situ Reinforcement

University Of Missouri-Columbia, Columbia MO

Investigators

Abstract

Maintenance and stabilization of surficial slope failures represent a tremendous, but often overlooked, economic and manpower burden for many infrastructure maintenance organizations (Transportation Research Board, 1996). Because of the benign appearance of most shallow slope failures, little research has been performed to determine the true life-cycle and overall organizational costs of maintaining these slides and how these slopes can be most effectively maintained. Maintenance and repair measures are currently selected more on the basis of tradition than for technical or economic reasons. As a result, repair methods tend to be quick fixes rather than long-term solutions with slope maintenance efforts tending to be repetitive occurrences at many sites. A relatively new technique that shows great promise for cost effective maintenance and repair of surficial slope failures is the use of small diameter, in-situ reinforcement similar to soil nails and micropiles. These techniques have been successfully used for stabilization of slopes both in the U.S. and abroad. However, the current level of knowledge of how loads are transferred in these systems, how closely spaced members interact, and how these systems can be optimized is rather limited (Bruce and Juran, 1997). Designs for stabilization of slopes with these techniques, therefore, remain very conservative, even to the extent of eliminating the techniques from consideration in many cases based on excessive cost. This is particularly true in applying in-situ reinforcing systems to stabilization of surficial slides since the overall costs that can normally be justified for repair of surficial slides are low. However, there are currently a number of novel installation methods and reinforcing materials that offer significant promise for use in stabilizing surficial slides. Consensus among designers and researchers alike is that significant fundamental research is needed to develop a better understanding of these systems so that more cost-effective designs and new innovative installation methods and materials can be technically and economically justified. An integrated suite of eight research and educational tasks will be undertaken to expand the state of knowledge in the area of slope stabilization using small diameter in-situ reinforcement and to improve surficial slide maintenance and repair operations. A large-scale tilt apparatus will be developed, constructed, and calibrated, and a series of tests will be performed with this device to evaluate the effectiveness of several alternative in-situ reinforcement strategies and materials for stabilization of surficial slope failures. Testing activities will be facilitated by numerical modeling efforts, which in turn will lead to development of a procedure for predicting the performance of reticulated reinforcement for slope stabilization. While focused on surficial slope failures, the results of this work will also provide direct and immediate benefits for application to larger slides as well. A reliability based decision-making framework will also be developed to assist maintenance personnel and infrastructure managers in making decisions regarding repair of earth slopes. Three integrated educational tasks will be undertaken to facilitate understanding of slope stabilization and repair problems, to introduce young persons in the exciting field of geotechnical engineering, and to disseminate and publicize the results of this project. A series of classroom scale physical models demonstrating key slope stability and soil-structure interaction concepts will be developed for use in college level undergraduate and graduate courses as well as for demonstration to K-12 students. An interactive, internet-based course module on soil-structure interaction in slope reinforcement applications will also be developed based on the results of the research to complement the physical models and provide for widespread dissemination of the research results. In addition, the large-scale tilt apparatus developed for this project will be utilized for predictive design exercises and a design contest for students across the country. Use of the apparatus in this way will serve to demonstrate numerous fundamental slope stability and reinforcement concepts to a broad audience and is expected to enhance the visibility of the geotechnical engineering profession.