A design method of side wall depth of a foundation pit belongs to the technical field of architectural structures and geotechnical construction. The design method aims at reducing material usage for a row
pile supporting structure of the foundation pit and saving cost on the premise of satisfying the reliability of the row
pile supporting structure of a side wall of the foundation pit. The method mainly comprises the steps of calculating upright
critical depth of the side wall of the foundation pit, providing a formula related to a stress increment of precompression of an
anchor bolt or a support transmitted into a
soil mass, and a formula of an upright
cutting depth increment of the side wall of the foundation pit, and constructing a
mathematical model of the upright depth of the side wall of the foundation pit: H equal to H0tau plus
delta H1 minus
delta H3 greater than or equal to h, wherein the
delta H1 is the upright depth increment of the side wall of the foundation pit caused by horizontal compressive stress increment of a
soil mass unit; and the delta H3 is the upright depth decrement of the side wall of the foundation pit caused by the vertical compressive stress increment of the
soil mass unit. Compared with results of various current
design methods of the
anchor bolt or support retaining structures, the material usage can be reduced by 50%-80% on the premise of ensuring the reliability of the row
pile supporting structure of the side wall of the foundation pit.