| Cubic ft. | |||||
|---|---|---|---|---|---|
| The central portion | 30 | ft. × 20 ft. × 1 ft. = | 600 | ||
| The two inclined portions | 2 30 | ft. × 20 ft. × 1 ft. = | 1,200 | ||
| 60 | ft. × 20 ft. × 1 ft. = | 1,200 | |||
| Ton. | Tons. | ||||
| Cubic contents | 3,000 | × 0·028 | = 84. |
From this must be deducted the weight of the water resting upon the two slopes, which equals 33·60 tons—
| Cubic ft. | Ton. | Tons. | |
|---|---|---|---|
| 60 ft. x 20 ft. X 1 ft. | = 1,200 | X 0·028 | = 33·60. |
C. Thus the insistent load at high water upon the whole area of the foundation is reduced by
| Tons. | Tons. | ||
|---|---|---|---|
| 84 – 33·60 | 50·40 | ||
| = | = 0·25 = ¼. | ||
| 201·60 | 201·60 |
D. At high water a vertical pressure is imposed upon the ground beyond the toe of the slope due to the 20 feet head of water—
20 ft. × 1 ft. × 1 ft. × 0·028 = 0·56 ton per square foot.
This latter weight and element of stability tends to prevent movement of the ground, and also the toe of the slope, but is entirely removed at low water when the insistent pressure at the foot of the embankment is the greatest.
For the purposes of illustrating the varying load upon the surface of the ground caused by a rise and fall of a tide, it will be sufficient to take one slope of the embankment.
E. The weight of a lineal foot of one slope, if unsubmerged =