Anti-slide piles are a main measure to reinforce slope for slope stability engineering

in which soil arch is easily formed between piles. Soil arch supported by adjacent piles is assumed to be horizontal and usually kept in plane strain status in vertical direction. It studies the calculating method of the soil arch supported by side surface friction of piles

which is combined with soil mass gravity. Then the influence of the soil gravity on arch bodies is further investigated in the view of quantity calculation. The research results show that the arch body in soil mass if considered to be weightless

is very safe for design purpose

because the gravity stress of soil mass has an important strengthening effect on the soil arch bodies formed between adjacent piles.