Abstract
This study presents a finite element analysis on the behavior of soil nail walls subjected to different freezing and thawing conditions. Thermo-mechanical coupled analysis has become increasingly important due to the increasing number of geotechnical structures built in cold regions. Soil nailing is a relatively new technique of reinforcing existing slopes or supporting new excavations. Its performance has been proven through decades of successful applications throughout the world. However, its applications in cold regions are still very limited due to sparse research available on its behavior in cold regions. In addition, soil may dramatically change its properties after experiencing freezing and thawing cycles. A two-dimensional finite element analysis using ABAQUS software is conducted to investigate the frost penetration depth in the soil and the resulting influence on the performance of the soil nail walls in Northern Ontario. The numerical model is verified against the field measurements obtained from a research program done in Brunswick, Maine, U.S. (Duchesne, 2003). The change of thermally induced stress along soil nails as well as the increase of displacements and earth pressure on the facing of the walls is investigated under freezing conditions. A parametric study is also conducted to probe the effect of thermal insulation systems on the wall facing and nails. This study provides valuable insight into the behavior of soil nailed structures in cold regions.
Highlights
Earth structures, such as embankments and slopes, and earth retaining walls, is commonly used in cold regions for transportation and other applications
1.3 Thesis Layout This study presents a numerical simulation of the freezing and thawing cycle on SNWs, followed by recommendations for implementing SNWs in cold regions
The model is adapted from Gibson et al (1981) theory, which is considered the variation of permeability and compressibility during thaw consolidation event
Summary
A soil nail is a structural element which transferred loads to the ground to retain excavated or existing slopes. The nail reinforcement developed stability of a slope, by improving the normal force and the soil shear resistance along the potential slip surfaces. The prolonged exposure to freezing temperature may weaken the facing materials, diminish the bonding strength between at the groutsoil interface, and the adhesion between the shotcrete and the soil. This may create additional long-term deformation, and generate excessive stresses on the nails. The propagation of thermal energy inside soil mass, and its associated strain and strength change, is a very complicated phenomenon Both unsaturated and saturated soils may revolve their engineering behaviours due to temperature variations (Gens, 2010). To minimize these detrimental effects, freeze-thaw cycles should be considered in the SNW design
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