Removable ground anchor mainly consists of the following types:
Ⅰ. Mechanical removable anchor
The removing principle of the mechanical removable anchor is to separate the steel strand from the anchorage device through twisting, pulling or striking at the steel strand
Advantage: There is larger clearance fit between the steel strand and the protective casing and this eased the recovery operation after unlocking.
Disadvantage: The anchor fails to recover normally due to the slurry leakage, unstable long-distance transmission and rusting of the unlocking device (complex underground environment, corrosion, etc.). As it is unable to predict the recoverable of the anchor through measurement, it appears to be more passive when taking remedial measures such as strong pulling and coring operation with casing.
Ⅱ. "U" shape rotary removable anchor
"U" shape rotary is a technology that forms a turn at the anchorage via unbonded steel strand. Next, pull one end of the steel strand, the steel strand is recovered by rotating the rotary body.
Advantage: Stable recovery rate.
Disadvantage: The rotational radius of the steel strand has to be controlled precisely or else it cannot be recovered normally. Equipment is required if unbonded steel strands are used. Similarly, since it is unable to predict the recoverable of the anchor through measurement, it appears to be more passive when taking remedial measures such as strong pulling and coring operation with casing.
Ⅲ. Hot melt removable anchor
Hot melt removable anchor product is to implant a hot melt device in the recovering anchorage device which unlocked by electric heating.
Recovering rate can be guaranteed through inspection at multiple stages.
1. Carry out inspection before construction to ensure all anchor rods have normal electrical conduction.
2. Conduct the test again after construction. Remove the anchor and reconstruct again if the anchor rod cannot be energized.
3. Inspect the anchor for its electrical conductivity before removing it. Remedy measures can be made beforehand for anchors that fail to energized.
1. Strong pulling to recover the anchor with large tonnage.
2. Casing drilling to obtain core method to recover the anchors.