Layback

Layback for excavation is given in units of run to rise.

However, it can be specified in terms of either variable run to a constant rise of one (1) or it can be given in a constant run (1) to variable rise.

A layback of zero (0) is simply an excavation with vertical walls (no slope to it)

Here are some common laybacks and their equivalents:

1/2 :1  is the same as 1:2

3/4 :1  is the same as 1:1 1/3

1:1 is a 45° slope

1-1/2 :1  is the same as 1: 2/3

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