Additionally these piles can go to depths exceeding those achievable by many other pile types. higher shaft stresses and moments being transferred into the piles. This pile type is predominantly favoured on bridges which carry significant loads under strict settlement criteria SICAP provides higher confidence in the construction methodology and also allows for good quality assurance tests subsequently allowing geotechnical engineers to design for. Screwed-in-Casing Augered Piles (SICAP) are a commonly used foundation type for bridges around the world.
This is unlike most blocks on the South African market which rely on friction between blocks and grids to keep the grids in place and to transfer the load.This article aims to highlight the critical importance of the positive geogrid connection, and why road agencies across the world, including the FHWA (Federal Highway Administration, United States) and more recently SANRAL (South African National Roads Agency Limited), mandate their use for block retaining walls supporting freeway infrastructure.
The block has a concrete bar that locks the geogrid into the block, forming a “positive connection”. The block is called the Vertical Fixed Connection (VFC) block developed by Bosun and can be constructed at 90°. ASTM D6638 connection capacity tests were undertaken, using most of the geogrids available in South Africa, with a new highly innovative and fully locally developed block. Testing has demonstrated the reduction in connection capacity due to non-horizontal draping on high-strength geosynthetics through a castellated block as measured using test method ASTM D6638. This article discusses the importance of a positive geogrid connection and shear nibs in SRW blocks, particularly when there is an expectation of load transfer from actions above the wall, such as foundations and impact loads.
This article forms part of a series of articles on segmental retaining walls (SRWs), following on Mind the Gap – towards the elimination of open assembly configuration in segmental retaining walls and The Proof is in the Pulling which appeared respectively in the April 2018 and April 2019 editions of Civil Engineering.
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