The maximum permissible eccentricity for no tension at the base of a gravity dam is A. $$\frac{{\text{B}}}{2}$$ B. $$\frac{{\text{B}}}{3}$$ C. $$\frac{{\text{B}}}{4}$$ D. $$\frac{{\text{B}}}{6}$$

The correct answer is $\boxed{\frac{{\text{B}}}{6}}$.

The maximum permissible eccentricity for no tension at the base of a gravity dam is the maximum distance that the center of gravity of the dam can be located from the centerline of the dam’s base without causing tension in the dam’s foundation. This distance is typically expressed as a fraction of the dam’s width, $B$.

The maximum permissible eccentricity is determined by the following equation:

$$e_m = \frac{{\text{B}}}{6}$$

where:

• $e_m$ is the maximum permissible eccentricity
• $B$ is the width of the dam

The equation is based on the following assumptions:

• The dam is a cantilever beam.
• The dam is perfectly elastic.
• The dam’s foundation is rigid.

If any of these assumptions are not met, the maximum permissible eccentricity may be different.

The maximum permissible eccentricity is important because it determines the maximum load that the dam can safely support. If the dam is overloaded, it may crack or collapse.