What is the minimum factor of safety for a permanent anchor?

A minimum factor of safety of 2.0 to 2.5 on the anchor capacity is recommended (Table 2).

What are the main types of anchor tests?

Suitability Test (on sacrificial anchors to validate design), Proof Test (on 10-25% of working anchors), and Acceptance Test (on all working anchors) (Clause 7).

What is the difference between free length and bond length?

The bond length (fixed length) is where the tendon is bonded to the ground via grout to transfer the load. The free length (unbonded length) is where the tendon can stretch freely to apply the prestressing force (Clause 3.1 & 3.10).

What is the maximum test load for a proof test?

The maximum load in a proof test is typically 125% (1.25 times) the design load (Clause 7.4.2).

IS 14986

: 2001

Code of Practice for Design and Construction of Ground Anchors

CurrentSpecializedCode of PracticeBIMGeotechnical · Geosynthetics and Ground Improvement

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This standard provides guidelines for the design, construction, and testing of prestressed ground anchors. It covers materials, design considerations like load capacity and corrosion protection, construction procedures including drilling and grouting, and detailed testing protocols to verify anchor performance.

Covers guidelines for the design and construction of ground anchors for various applications.

Quick Reference Values

Overall Factor of Safety (Permanent Anchor)2.0 to 2.5

Overall Factor of Safety (Temporary Anchor)1.5 to 2.0

Maximum Proof Test Load1.25 x Design Load (DL)

Maximum Suitability Test Load1.50 x Design Load (DL)

Minimum Free (unbonded) Length3.0 m

Minimum Bond Length for Rock3.0 m

Minimum Bond Length for Soil5.0 m

Key Formulas

Tu = π * D * Lb * τu — Ultimate load capacity of anchor based on skin friction

Practical Notes

On-site suitability tests are crucial before mass installation to validate design assumptions, especially the assumed ground-grout bond strength.

Proper corrosion protection is paramount for permanent anchors, as failure can be catastrophic. The level of protection should match the design life and aggressiveness of the ground environment.

Grout quality (W/C ratio, additives) and injection procedure are key to achieving the desired bond strength; bleed and segregation must be controlled.