Abstract: In engineering design, the soil arching and the entire stability of the soil mass between the soldier piles are usually neglected. The research was carried out on the soil arching and the entire stability of soil mass between the soldier piles in excavation. Expressions of the loading ratio and the spacing of the piles were obtained. Through the verification in four types of clays, it is found that in the silt and clay with higher strength index, the loading ratio reaches 100% when b/S is up to 0.5; where b is width of pile cross-section; S is pile spacing; and in the mucky clay with lower strength index, the b/S should be 0.8 for the 100% loading ratio. The pile spacing can be relatively wider under the condition of the entire stability of soil mass. For the pile with regular diameter, the pile spacing should be designed meeting the stability of the soil arching, while in silt with higher friction angle but lower cohesion, especially for the piles with large diameter, the pile spacing should be designed according to the entire stability of the soil mass between piles.

Key words: pile spacing, soil arching, entire stability, loading ratio