Work Methodology of Cable Anchors

Introduction: To work in a Hydro sector support system plays very important role. Either to support the rock or slope some of the most important method are Rock Bolting, Rock Anchoring, shotcreting, wiremesh etc. Out of which Cable Anchoring lays very important role, some people also termed as Tendons. Working methodology for cable Anchoring are described here: 1) Drilling 2) Fabrication of Anchors 3) Lowering of Cables 4) Anchor Grouting 5) Stressing

1. Drilling:

Drilling of Anchor holeswill be completed upto the required depth (Fixed length+Free length) and at require inclination with the help of percussion drilling method.

2. Fabrication of Anchors:

• 7 nos. of 12mm dia. Un-oiled strands shall be cut to the 16m length. Cutting of cable is to bederived as fixed length@9m and free length@6m + extra 1m for stressing purpose.
• Strands are cleaned throughly and dust on the surface is removed 1st coat of epoxy paint is to be appklied uniformly on the strands and it is allow to dry for a period of 2-3hrs. The second coat is applied thereafter and the same is allow to dry for 24hrs. The third coat is applied uniformly thereafter. Quartz sand is to be sprinkled on fix zone of strands when third coat is tacky.
• Place the 100mm ID, 2mm thich flexible HDPE pipe on Free length portion.
• The Pre-stressing strands, greased for the free length portion should be enclosed in 16mm ID HDPE sleeves, 2mm encasing individual strand.
• Fix length of cable is then provided with 84mm ID corrugated HDPE sheathing 2mm thick.
• Fabrication: Fix shoe with the help of brazing at bottom of the cable. Then tie spacer at 1.0m c/c through out the length of the cable.
• Shifting of cable at site: Prepare bundle of suitable diameter so that the same can be loaded and off-loaded in trailer. Keep all cables above ground levels with the help of wooden sleepers.

3. Lowering of Cables:

• A lowering of anchors, check the depth of the hole by inserting a strands piece of similar length.
• After checking depth of holder lower fabricated cable into the hole, while lowering ensure that cable is in suspended position be keeping about 300mm from bottom of the hole and of the cable.

4. Anchor Grouting:

• Grouting of cables will be carried out by using MI-pump which is having output capicity of 1200lit/hr. and working pressure of 30 kg/sq.cm. Prepare cement grout mix of 1;0.4 by calculating volume of grout to be poured in an anchoe length zone. If possible dry cement should be seived to remove lumps or stone from the cement.
• Grout the entire hole (Fix length+Free length) with the help of cement grout. Whilr grouting the grouting operation should be in one go only. There should not be any stoppage in between and no air entrap in between the grout.

5. Stressing:

Stressing of anchor will be carried out when grout has attained required strength. The stressing will be carried out by using hydraulic jack. Use load cell to measure the residual forces on the anchors. After 24 hrs. of stressing, the extra length of the cable above anchor head should be cut by keeping 2'' projection above anchor head with the help of grinder.