I love this thread. The compression strength of a stiff mortar is more than sufficient to support bricks of any reasonable size and weight unless your wall is one brick wide and you have a bionic bricklayer. Mortar gains compression strength very quickly, which is why a good brick layer can lay any thing up to a 1000 bricks a day in a wall only 3 or so metres wide. Once cured the mortar compression strength had better be greater than the brick otherwise the resident engineer or clerk of works will quickly condemn the corresponding wall. The issue of shear in the wall running down the sloping path will only be a factor if there is foundation failure in which case the wall is the least of the worries. The answer is simple. Walls need to turn corners and are supported by piers. I do not see any way a triangular brick can do this. Nor can a cubic one. The rectangular brick with one side twice the other was found about 5,000 years ago to be the best way to tie a wall around a right angled corner and remains so to this day.
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