Shearing strength and tensile strength of soil body can almost ignored, but it exists certain structural integrity. After installing soil nail system with certain length and density, soil nail system and soil body can work together. It can cover the shortage of soil body’s strength and form composite soil. soil nail system has the main functions in composite soil.

1. Constraint force.

It depends on stiffness, strength and spacial combination form of soil nail system in soil. soil nail system has the function of constraining the deformation of soil body and makes composite soil become a whole.

2. Bearing capacity.

In composite soil, soil nail system and soil body bear external load and gravity stress together. After soil body reaching plastic state, stress transfers to soil nail system gradually, soil nail system’s bearing capacity is more prominent because of high shearing strength. The proportion of soil nail system’s bearing capacity depends on stiffness ratio of soil nail system and soil body, soil nail system’s spatial location and composite soil’s stress level.

3. Transmission and diffusion of stress.

Under the same load condition, strain level in soil nail system parts is lower than plain soil slope, which postpones the formation and development of cracking zones.

4. Constraint force of slope deformation.

Steel fabric sprayed concrete panel is settled on slope with soil nail system, which restricts excavation unloading and swelling deformation and then strengthens constraint force to boundary.