Abstract:  In manual excavation of slopes two cantilever anti-slide piles are constructed in rational spacing.Through stacking boulder strips on the top of fill heaped on the back of piles,horizontal deformation of breast boards and soil pressure ratio of piles to breast board are studied when the breast boards are constructed in front of piles.In order to simulate the excavation process of soil in front of piles,the boards are taken down from top to bottom after the readings of displacement sensors and soil pressure cells are stable.The action extents and ranges of direct and friction soil arches are discussed according to the analysis on regularities of x-direction soil pressure distribution along different levels.The partial slump surface of soil between piles is measured after the breast boards are taken down.The results which contrast the partial slump surface of soil between piles and influence circle of three-dimensional soil arching effect testify that partial slump surface is usually located at the inner of soil arching area between piles with rational spacing.Finally,a simple static penetration device is made for evaluating the solidity of undisturbed soil on shear failure line of arch spring,and the ultimate thicknesses of shear action are analyzed at different heights based on the measured penetration curves.