1. 22 The relieving platform limits the sliding plane, and the sliding mass at this time is no longer a voussoir, so,[www.Sentencedict.com] Rankine theory and Coulomb theory cant be applied to calculate the earth pressure.

2. If a series of wedge-shaped blocks—i.e., ones in which the upper edge is wider than the lower edge—are set flank to flank in the manner shown in the figure, the result is an Arch.These blocks are called voussoirs.Each voussoir must be precisely cut so that it presses firmly against the surface of neighbouring blocks and conducts loads