In the rigid pile composite foundation that pile is long enough and is not more than 6 times the pile diameter

the internal shear force between pile and soil and under friction of the pile-soil interaction

the soil pressure in the top section of the pile only increased at a certain depth range

it decays rapidly with depth and axial force of top pile increases with depth in soil shear stress and friction. Based on this characteristic of the rigid piles composite foundation

when there is rigid pile composite foundation surrounding excavation and the excavation bottom is higher than rigid pile bottom

soil pressure on the retaining structure which is caused by the additional vertical stress of rigid pile composite foundation can be simplified as an inverted triangle; and the maximum earth pressure effect on intersection of the rigid pile top plane and supporting structure

as the depth increasing

the active earth pressure attenuates to zero. It is shown that the calculation method is consistent with the engineering reality.