Rigid Body Stability (Gravity Analysis)
Rigid body stability, also known as gravity analysis, assesses the stability of a dam under the influence of gravity and other external forces. This analysis evaluates the equilibrium of the dam as a rigid body subjected to various forces, including the weight of the dam, water pressure, soil pressures, and any additional loads acting on the structure. The primary objective is to determine if the dam has sufficient resistance against sliding along its foundation and if it is stable against overturning.
First, potential failure surfaces between the dam and its foundation are identified. These surfaces are typically determined based on the site’s geological and geotechnical characteristics, considering factors such as soil properties, slope angles, and water levels. Potential sliding surfaces can be identified along the interface between the dam and the foundation, while potential overturning surfaces are related to the center of gravity of the dam.
Second, factors such as the dam’s weight, water pressure, and soil pressures are calculated. The dam’s weight is calculated by considering the weight of the dam’s materials, such as concrete or earth fill. The dam’s water pressure is determined based on the hydrostatic forces caused by the water stored behind the dam. Soil pressures from the foundation and any additional loads are also accounted for in the analysis.
Lastly, the forces and moments acting on the dam are computed, with special care to include equilibrium conditions. The analysis determines the factor of safety against sliding and overturning by comparing the resisting forces to the driving forces. A factor of safety greater than 1 indicates stability, indicating that the dam can resist the applied forces without failure.
Rigid body stability analysis also helps to identify critical failure surfaces and potential weak points within the dam’s structure. This information is crucial for improving the dam’s condition and implementing structural reinforcements.
Best Practices Resources
Stability Analysis of Concrete Structures (EM 1110-2-2100), USACE