3. To have an equal load upon the ground, and to guard against any extra strain upon the foundations near the face of a wall consequent upon the lateral thrust, which has a tendency to cause a wall to overturn.
4. Particularly to provide against any forward movement either by having deep foundations, protective works at the base of a wall, or by other means.
Note.—It is obvious, in order to counteract a sliding movement, that the foundations should be at right angles to the face batter at the base, and not be horizontal. These inclining inward foundations, however, can only conveniently extend for a portion of the width in very thick walls, but throughout in those of less thickness. When no support is possible in the front of a wall, such as an extra depth of foundations, an invert, or a firm connection between the lower portion of opposite dock-walls, &c., it is advisable to counterfort the wall.
5. That the wall should be as symmetrical in form as possible, particularly upon a soft foundation, in order to ensure equal loading and settlement, and that it subsides without a forward movement or tilting.
6. That it should be homogeneous, especially when the strata dip toward it, sufficient provision being made to prevent any lodgment of water at the back.
7. That it must have the usual margin of stability above the sufficient weight and mass to resist the calculated lateral thrust of the earth and that caused by it being surcharged by buildings, goods, cranes, or machinery, which may cause unequal and sudden loading and strain; and to withstand in sidelong ground the additional lateral thrust caused by the inclination of the strata.
8. That the face be sufficiently perpendicular to allow ships to lay close alongside, and that it be of the required hardness to resist the rubbing of vessels, and especially of barges.
9. That, when a wall is constructed of different materials, a complete union is effected of all the parts, and anything tending to make it of varying strength, unless exceptionally required, should be avoided; such as the junction of lime concrete with Portland cement concrete, or the employment of the hardest and strongest bricks or stones and their connection by means of a weak mortar.
10. That the resultant of the vertical and lateral pressure of the wall, whether surcharged or not, falls well within the middle third of the wall at its base. If not, the foundations will be unequally strained.
11. That any mooring posts or bollards, gate or sluice chamber machinery be so placed and secured that they cause no serious additional strain upon a dock-wall.