For heavy embankments and dams, of height h, the depth of exploration of soil should not be less than A. $$\frac{{\text{h}}}{4}$$ B. $$\frac{{\text{h}}}{2}$$ C. h D. 2h

The correct answer is C. h.

The depth of exploration of soil for heavy embankments and dams should be at least equal to the height of the embankment or dam. This is because the soil at the base of the embankment or dam must be able to support the weight of the structure. If the depth of exploration is less than the height of the embankment or dam, the soil may not be able to support the weight of the structure and the embankment or dam may collapse.

Option A is incorrect because the depth of exploration should be at least equal to the height of the embankment or dam, not one-fourth of the height.

Option B is incorrect because the depth of exploration should be at least equal to the height of the embankment or dam, not one-half of the height.

Option D is incorrect because the depth of exploration should be at least equal to the height of the embankment or dam, not twice the height.