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It took a lot of effort to find it, please tell me if I find anything wrong! 1. If the soil quality is good, the trench does not need to be sloped, and there is no underground water, the cross-sectional width of the trench should be based on the outer diameter of the pipe D+2 * 0.30m ； The depth H is 1.80m (if the designed buried depth of the pipe bottom is 1.80m, the thickness of the pipe foundation should also be added. When the pipe foundation is concrete, the base width should add 0.30m on each side of the concrete foundation). Right now: (Trench bottom width) B1=D+2 * 0.30m pipe trench cross-sectional area S=B1 * H Earth excavation work volume V = (total length of pipe trench) L * S 2. If grading is required, the grading coefficient of general soil is 0.43, that is: (Upper opening width) B2=H * 0.43 * 2+B1 Pipe trench cross-sectional area S=(B1+B2)/2 * H. If drainage is required, the ditch bottom width B1 should also be added to the drainage ditch width. Quantity of earthwork excavation V = (total length of pipe trench) L * S The pipe itself has a drainage slope. Generally, i=3~5‰. If the pipe trench is long, the trench digging depth H must be adjusted according to the drainage slope of the pipe. * * * When laying multiple pipes in the same trench * * * * * * * * * ： When multiple pipes are laid in the same trench, the trench bottom width should be based on the trench bottom width of a single pipe. For each additional pipe, the trench bottom width should be increased by the pipe diameter plus 400mm.