This award winning, patented system has been used extensively within the UK and overseas for anchoring in soils and weak rock. It generally provides double the efficiency in mobilisation of in-situ ground strength over normal fixed anchor lengths of 8 to10m. The system has demonstrated that in the majority of medium strength soils unltimate loads in the 250 to 400 tonne range can be repeatedly achieved. The principles of the system and its load transfer mechanism are acknowledged in BS8081 and the corrosion protection system adopted for permanent works is the simplest in concept yet the most reliable in practice. The entire length of the steel members within the ground is isolated from the environment by two continuous layers of plastic, in addition to several supplementary layers of cementitious grout.

The fact that each individual investigatory anchor, which has been tested to failure, identifies values of ultimate bond stress at the grout/ground interface in each of the multiple of anchors in the anchor borehole, has allowed extensive research into the influence of chosen fixed length on utilisation of soil strength. It is commonly accepted that the progressive debonding phenomenon results in a reduction in anchor efficiencey with increase in fixed length. However, it is the depth of data established from SBMA testing that has allowed this efficiency to be accurately quantified, such that a correction factor can now be introduced into the accepted formulae for the design of anchors in soils and weak rocks.

An index of available, published technical papers is provided here for reference. Further details of these papers and other technical literature on ground anchors can be found at www.TheAnchorman.com.

An example of a design for SBMAs based on "Procedures of Geotechnical Engineering Handbook - 2003" (Publisher Ernst & Sohn), written by Tony Barley and H. Ostermeyer, can be be downloaded as a .pdf file by clicking here.

The Actively Stressed Soil Nail System provides the industry with a slope or face retention method that allows usage of a lightweight facing that itself may be retained by the soil in the resistant zone. It does not require heavy structural facing as required by prestressed ground anchors. Both the facing and the active soil mass are tied independently to the resistant zone of the soil mass.

At last the answer to those who have bandied around the term 'prestressed soil nail' has been made available to the Geotechnical Specialist.

This new system, developed at a university in Korea, uses fibre optics to monitor movements in a slope. The results are transmitted to a computer where they can be remotely accessed and analysed in real time.