Chronic instability of existing railroad track substructures and embankments cause track deflections that require frequent maintenance, slow orders, and overall inefficiency of railroad operations. Substructure instability can be caused weak subgrade soils, poor-quality ballast, or inadequate thickness of the ballast and subballast layers. Typical problems that develop are subgrade shear failure, ballast pocket formation, and fouled ballast. As these problems develop, drainage becomes inhibited and the presence of water accelerates the problem. Slope instability problems that affect rail operations include embankment fill slope failures and landslides in natural slopes. Water, or water pressure, is often the primary cause of these types of instability.
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