Stepwise repeated destabilization and stabilization of highly collapsible soil mass by ‘soil nailing technique’ used for construction of railway/road underpass

A process for making an underpass through a railway track or road without service interruption by stepwise destabilization and stabilization of a collapsible soil mass by a soil nailing technique, the process comprising the steps of:

• (i) marking a position of a box on a vertical face of a first retaining wall or an embankment;
• (ii) dismantling the retaining wall above the marked position of the box and providing temporary support by shuttering plates having holes for pre-decided positions of nails to be driven in the vertical face;
• (iii) nailing the soil mass by using grouted nails and driven nails above the marked position of the box;
• (iv) again dismantling the first retaining wall, placing the shuttering plates with pre-drilled positions of nails and inserting only the driven nails from the top to the bottom of a box pushing area;
• (v) leaving a complete nail system for a period in the range of 8 to 12 hrs to mobilize the friction of the nails;
• (vi) bringing the box close to the soil-nailed, wall face;
• (vii) loosening one top row of shuttering plates, and excavating the soil to a 30 to 40 cm depth;
• (viii) repeating step (vii) until the entire rows of the nails are covered for a 30 to 40 cm depth followed by pushing the box into the excavated area of 30 to 40 cm depth;
• (ix) pushing the nails into the soil mass and again tightening of the shuttering plates;
• (x) repeating steps (vii) to (ix) until 50% of the box pushing length;
• (xi) cutting the nails in the range of 25 to 35 cm to create a space for box pushing wherein first/pointed ends of the nails will touch a second retaining wall, followed by placing vertical nails in order to increase the stability of the cut slope;
• and
• (xii) again repeating steps (vii) to (ix) until complete insertion of the box for making an underpass.