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Saturday, August 4, 2007

SOIL NAILING

Soil nailing is a method to stabilize and strength the existing ground or slope. The basic method is reinforcing by installing threaded steel bars (the nails) into the soil or slope as construction proceeds from top down. The bars are inserted closely spaced pattern to increase its overall shear strength.The steel bars are then grouted to create stable mass of soil. Steel bars commonly be used, with diameters ranging from 15 to 46 mm, stronger than driven nails (about 60 ksi). Grouted nails are inserted into boreholes of 10-15 cm and then cement-grouted.
The cement grouting process is by injecting the Grade 30 cement with water/cement ratio is about 0.45 to 0.5. The cement grout shall be carried out by tremie method. 0.75” to 1” diameter HDPE grout hose is inserted into the borehole and grout tremie out under a normal pressure of about 0.7 MPa or just enough to pump the grout into the borehole. The grouting process shall be continued until neat cement grout flows out from the bore holes. If temporary casings are used, the casings shall be removed by immediately after grouting work is completed. During and after removal of casing, the grout column is to be topped up when necessary.
Soil nail bars shall be locked. Stressing or locking of the soil nails shall only commence after a minimum of 5 days curing period or when the cube strength for the cement grout achieved 75% of design strength. Stressing or locking of the nail bar shall be by either a hydraulic jack or simply by a torque wrench to the required load 5kN. Soil nail head shall be constructed after stressing work finished.

Soil nail construction has many advantages:

  • Soil nail walls can be built to follow curved or zigzagged outlines.
  • The equipment used is highly portable and can fit easily into small spaces.
  • The process is flexible and makes modifications easy to carry out (e.g., nails can be moved as needed during construction).
  • Construction causes less noise and traffic obstruction on highways.
  • The process creates less impact on adjacent or nearby properties than do other construction methods.
  • It generally requires less space and manpower

1 comment:

Sreekumar Nair said...

Thank you! your details in regard to soil nailing was very much informative

Sreekumar Nair