The fundamental difference between a dam and a retaining wall lies in the type of material they are designed to hold back.
According to a definition from September 5, 2018, a masonry dam retains the water behind it, whereas a retaining wall retains the soil components behind it. This highlights the primary function and the nature of the pressure each structure is built to withstand.
Key Distinction
While both structures are engineered to resist lateral pressure from materials, their purpose dictates the specific material they are built to retain:
- Dams: Primarily engineered to hold back large bodies of water. The pressure exerted by water increases significantly with depth, requiring robust designs to manage immense hydrostatic forces.
- Retaining Walls: Primarily designed to support soil, rock, or other granular materials, often used to prevent erosion or create usable level ground in sloped areas. The pressure from soil is different from water pressure and depends on the soil type, moisture content, and angle of internal friction.
Pressure Dynamics
Despite retaining different materials, the way pressure distributes across the height of certain types of these structures can be similar. The reference notes that the pressure distribution throughout its height is similar to that of a masonry dam for a retaining wall. This suggests that the engineering principles for analyzing lateral pressure distribution might share common ground, particularly for gravity structures.
Summarizing the Difference
Here's a simple breakdown:
| Feature | Dam | Retaining Wall |
|---|---|---|
| Material Retained | Water | Soil/Soil Components |
| Primary Function | Store water, control flow | Support soil, prevent erosion/collapse |
| Typical Scale | Large, spanning valleys | Varied, from small landscaping to large civil works |
Practical Considerations
Understanding this difference is crucial in civil engineering and construction because it directly impacts:
- Design: Structures must be designed to handle the specific forces and properties of the material they retain (water density vs. soil density, hydrostatic pressure vs. earth pressure).
- Materials: While both can use materials like concrete, masonry, or earth, the specific requirements for impermeability (dams) or drainage (retaining walls) differ.
- Safety Factors: Safety calculations must account for the unique risks associated with water retention (potential catastrophic failure, downstream impact) versus soil retention (erosion, slope instability).
In essence, although both are barrier structures resisting lateral forces, their core function and the material they restrain define their fundamental difference.
