Abstract: The element limit analysis method is used to study the influence of soil nail length on the overall stability of soil nailing in soft soil /hard clay foundation pit with vertical slope; and then the limit height is obtained.The influence of soil bearing capacity and slope angle on the overall stability of soil nailing in the soft soil is studied. The results show that the length of soil nails in the vertical foundation pit is 1.4 to 1.5 times the depth of the pit in the soft soil; and the depth of the pit is 0.8 to 1.0 times in the hard clay. When the bearing capacity of the bottom soil is increased, the failure mode changed from passing through the pit bottom soil to passing through the pit toe; and the safety factor is increased. Decreasing the slope angle has no much influence on the overall stability of the soil nailing in the soft soil.

Key words: soil nailing, soft clay, overall stability, sloping, limit analysis