The Basic Introduction of Soil Nail
Soil nailing structure is a new retaining structure for soil excavation and slope stabilization since the 1970s. It combines soil mass, soil nail body and concrete front-panel. Through installing soil nail with certain length and density in soil mass, soil nail forms compound soil body based on cohesive force and frictional resistance. Under the circumstance of soil deformation, soil nail accepts passive stress and then reinforce the soil mass by the tension effect. This will not only enhance the stiffness of entire soil body, but also remedy the weakness of soil body: shear-resistance and low-extension strength. Then, the supporting structure with active restriction mechanism is formed, which will enhance the entire stability and improve soil body’s plastic deformation and failure property.
Soil nail has the functions of convenient, reliable and economical. At the same time, during soil nail construction, the influence for surrounding environment is little. So, soil nail supporting is widely used in foundation excavation project.
In loose soil and broken rock conditions, advance reinforcement should be carried out, such as grouting and micro pile underpinning.
1. The application of soil nail.
Generally speaking, soil nail is suitable for foundation excavation support and slope stabilization in artificial soil, clayey soil and weak consolidated sand. The depth of excavation should be less than 16 meters, and the depth can be increased when combining with pre-stressed anchor bolt. Soil nail should be not used in silty sand layer with rich water, sandy gravel stratum and mucky soil.
2. The exploration of project.
As for soil nail support, the previous exploration is necessary for the security of project. It includes underground pipelines and rainfall.
3. The design and monitoring.
Accurate and reasonable design is the premise of ensuring construction quality, which influences the security, construction period and investment of project. So the design should bebased on geological survey report, analyze soil property, combining theoretical analysis with project experience. During the process of construction, design parameters should be adjusted according to site conditions. Monitoring work should be also done, it includes horizontal displacement, sedimentation, soil nail stress and soil pressure, etc.