SPR 2013 Prime KTC: Mechanically Stabilized Earth Walls

This investigation will develop a better understanding the practice of using MSE walls in Kentucky. It will provide guidelines to assist design engineers, specification writers, construction inspectors and maintenance personnel with the selection, design, construction and maintenance of MSE walls at bridge ends, and the monitoring of their long-term performance. Also, the guidelines will provide valuable information for decision making within KYTC when they are recommended as a design alternative. Mechanically Stabilized Earth (MSE) walls are widely used in bridge ends nationwide. By placing tensile reinforcing elements (inclusions) in the soil, the strength of the soil can be improved significantly such that the vertical face of the soil/reinforcement system is essentially self supporting. The use of a facing system to prevent soil raveling between the reinforcing elements allows very steep slopes and vertical walls to be constructed safely. Currently, KYTC has no design guidelines for using MSE walls. There are limited applications of MSE walls in Kentucky and KYTC does not practice the design of these structures. Several issues surrounding MSE walls in Kentucky remain unclear -- including, cost savings, the site conditions where they should or should not be utilized, what are the maximum heights permitted, the overall stability with long-term performance, newer, more robust materials, and various methods of constructing these walls. Retaining structures are essential elements of every highway design. For many years, retaining structures were almost exclusively made of reinforced concrete and were designed as gravity or cantilever walls which cannot accommodate significant differential settlements unless founded on deep foundations. When the height of retaining structures increases and poor subsoil conditions exist, the cost of reinforced concrete retaining walls increases rapidly. MSE walls offer significant technical and cost advantages over conventional reinforced concrete retaining structures at sites with poor foundation conditions. However, suitable design criteria are still required to address foundation conditions, the maximum heights permitted, overall stability, corrosion of steel reinforcing elements, and potential degradation of polymer reinforcement in the ground.