For temporary soil nailing, there is no need to use plastic casing. The angle deviation between flat plate or domed plate and self drilling anchor bar is up to 3°. Generally temporary support time for foundation pit engineering is 3-6 months, not more than 24 months.
For permanent soil nailing, the support time for general projects is 2-30 years, important projects not less than 50 years and major projects not less than 100 years. And the corrosion allowance is considered in the production in view of the self drilling anchor bar corrosion over time.
1) Casing is needed for permanent soil nailing. The depth of plastic tube inserted into the soil should be at least 20cm;
2) The surface thickness of concrete should be at least 50mm or filled with corrosive materials;
3) To avoid the conductive contact between the rebar and the nail;
4) Permanent soil nailing should adopt grouting soil nailing;
5) Soil nailing should have enough mortar layer thickness;
6) The nail head should be placed in a certain depth in the surface layer for protection;
7) It’s better to use plastic materials instead of metal materials to make centralizer;
8) Permanent soil nailing can be used to expand the area of soil nail material to replace the anti-corrosion layer;
9) For non corrosive strata, we can adopt epoxy coating protection measures. The thickness of epoxy coating should be not less than 60-80μm and galvanizing not less than 65um. It is suggested that the minimum thickness of the protective film should prevent the damage caused by normal operation or construction.
10) For corrosive strata, we can use corrugated pipe protection measures. The thickness of cement mortar layer between the corrugated pipe and the hole wall should not be less than 30mm;
11) The use of accelerator should be compatible with cement, no corrosion to soil nail, and make the paste does not produce cracking or shrinkage.