The design principle and construction method from the case of Gome Shoppingcity excavation project on two-step composite soil nailing combined with spline-pipe soil nail

general soil nail and prestressed anchor are presented. A field investigation

including tensile forces of soil nail

excavation displacements and anchor stresses

and comprehensive analyses of the results are addressed. The characteristics of two-step composite soil nailing of excavation in sand and gravel layer are further investigated. Owning to the backslide effects

the mechanisms of soil nailing are changed. It also suggests that the horizontal deformation of excavation is controlled well by prestressed anchor of composite soil nailing support system. And the prestress loss of anchor after locking is obvious because of some factors

such as the limit of surface stiffness of soil-nailing wall and the small thickness of bearing plate. The curve which is formed by positions of maximum tensile forces of soil nails may be the most dangerous sliding curve.