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An anchor tendon with a 8m fixed length in soil or rock will, at test load, need to extend some 25mm at the proximal end of the fixed length before any load will be transferred to the distal end of the tendon.
It is unusual for the elastic behaviour of the grouted soil around the anchor tendon to be compatible with the elasticity of the tendon and allow a uniform distribution of load along the fixed length.
Thus, it is widely acknowledged that, in the majority of circumstances where conventional anchors are used, debonding at the tendon/grout or the grout/ground interface must occur as anchor load increases and prior to any load being transferred to the distal end of the fixed length.
This phenomenon is commonly known as progressive debonding and is associated with
Information has been published by a multitude of researchers on this topic.
Progressive debonding generally results in a highly inefficient use of the existing ground strength. In circumstances where the ground strength far down the fixed length is being utilised, the ground strength above this has been exceeded and only some residual strength is available. This reduces the overall efficiency of the fixed length (Fig.1).
Stronger by design
However, a system that can transfer the load simultaneously to a number of shorter
lengths in the fixed anchor bore without the occurrence of Progressive Debonding,
will mobilise the in-
This is the principle of the single bore multiple anchor (SBMA).
SBMA systems offer technology that completely isolates the tensile steel tendon from the surrounding environment.
In the fixed length this is achieved by employing double corrosion protection via two impermeable corrugated HDPE ducts in accordance with:
In the free length two plastic sheaths are used to create a suitable barrier from the environment, again providing double corrosion protection.
NOTE: Total anchor load equates to shaded area under the curves
Anchor Load Distribution For Normal Anchor
Single Tendon Fixed Length
Load Distribution Along Fixed Anchor
Fixed anchor length generally 10m max
SBMA Load Distribution
Load Distribution Along Fixed Multiple Anchors
Fixed anchor length can be increased to 25m+
Multiple Anchor Units