The mine, which is work d on the open system and has a depth of 450 ft., yields stones of very fine quality, but the annual output does not exceed in value 500,000.
Thus we don't ever need to compute the Bezier polynomials, we simply depth reduce the control points recursively until d =0.
Within Blue Bridge Lane, Trench D exposed subsoil at a depth of 0.35m below the present ground surface.
If now we assume the water to have a depth d above the base, the total water pressure represented by the triangle kbh will have its centre at d/3 from the base, and by the parallelogram of forces, assuming the density of the masonry to be 2.5, we find that the centre of pressure upon the base bc is shifted from the centre of the base to a point i nearer to the outer toe c, and adopting our assumption of uniformly varying intensity of stress, the rectangular diagram of pressures will thus be distorted from the figure bfgc to the figure of equal area bjlc, having its centre o vertically under the point at which the resultant of all the forces cuts the base bc. For any lower level the same treatment may, step by step, be adopted, until the maximum intensity of pressure cl exceeds the assumed permissible maximum, or the centre of pressure reaches an assigned distance from the outer toe c, when the base must be widened until the maximum intensity of pressure or the centre of pressure, as the case may be, is brought within the prescribed limit.
