Note Return to text — EXPERIMENTS ON RETAINING WALLS AND PRESSURES ON TUNNELS.

The solution represented by Fig. 11 is general, and applies whether is inclined to the right or left of the vertical through or coincides with it, and whether the earth surface is horizontal or inclined above or below the horizontal. It can likewise be easily adapted to the case shown in Fig. 1.[Footnote 7] The construction of Fig. 11 has been used in evaluating the thrust and determining (approximately) the plane of rupture in the experiments (recorded below) of Leygue on retaining boards, , that could be rotated about , and thus placed at any inclination to the vertical. In all the experiments, the vertical height of was 0.656 ft.; the length of the board was 1.3 ft. The value of the moment of the earth thrust about was found by use of suitable apparatus, corresponding to dry sand with a natural slope of 3 base to 2 rise, or , , and lb. per cu. ft. By use of the partition board mentioned previously, the side friction of the sand on the glass sides of the box containing it was estimated, and the moments corrected, so as to give the true moment when there is no side friction. The notation used to express results is partly given in Fig. 12, for the general case where,