Versatile and effective ground engineering solutionActive and passive anchors
Active anchors as those with a designed bonded and free length and subject to post tensioning after installation. Passive anchors are fully grouted tension micropiles, subject to no post tensioning and are only “activated” when there is movement within the ground.Temporary and permanent anchors
The main difference between temporary and permanent anchors are the design life of the system. Temporary anchors are those with a service life of two years, longer than this is considered a permanent application. The EN 1537 provides guidelines for the temporary corrosion protection of ground anchors and the EN 14199 for the temporary and permanent application of tension piles.
Permanent applications or active anchors are those with a design bonded free length and are subject to post tensioning after installation. These also have a service life of >100 years. Passive anchors are fully grouted tension micropiles, subject to no post tensioning and are only “activated” when there is movement within the ground. With this application in a permanent situation, corrosion factors need to be used. Either a surface coating or a calculation using sacrificial corrosion allowance. Permanent anchors have a bonded length and a free length which uses an HDPE tube over the designed depth.
Permanent anchors have a bonded length, and a free length which uses an HDPE tube over a designed depth. Forces are then transmitted to the ground via the bond length. These are prestressed to control the movement of the wall during the various construction phases.
It is worth nothing that all anchors with a free length, are known as ground anchors, but anchors that are fully grouted and not post-tensioned are known as tension micropiles.
Ground anchors or tiebacks are versatile solutions used to retain and support civil engineering structures, either temporarily or permanently.
An effective method of progressing the excavation, clearance and construction of a site, is to maximise the space available. Traditional methods of internal propping and shoring occupy a significant proportion of a construction site’s area. This limits space, restricting movement of plant and ultimately impacting on the programme.
Given the necessary approvals, tension microplies can be installed beneath highways temporarily. Utilities, once identified, can be avoided by increasing the tie back anchors angle of installation.
The use of temporary works tieback anchors to retain structures eliminates the need for temporary propping or shoring, freeing up space on site. This enables the groundworks and construction to progress efficiently with minimum disruption.
Supporting various types of permanent retaining walls, incl. sheet piled walls, permanent piled walls, diaphragm walls, dams and in marine and port applications.
Temporary works in civil engineering often have a requirement to have designed anchors for instance in basement or sheet piled applications. When this is required, holes are drilled using rotary and percussion techniques with or without casing. A hollow Titan bar is drilled, this creates the bore hole to the designed depth and the borehole is then grouted simultaneously whilst drilling. When the anchor is completely installed, it is then tensioned and locked off against a head plate using a spherical nut.
When the service life of the anchor is limited to less than two years, it may be detailed as a temporary anchor, depending on the site conditions, consequence of failure and risk of corrosion. Temporary anchors have reduced corrosion protection, simpler detailing can be specified so that they may be removed after their designed service life. Temporary anchors generally have a bonded length, and a free length which uses an HDPE tube over a designed depth. Forces are then transmitted to the ground via the bond length. It is generally prestressed to control the movement of the wall during the various construction phases.
- Up to 3 times greater productivity than conventional cased anchor systems.
- Grout injection technique continually scours and flushes the sides of the drill hole, enhancing the mechanical connection to the soil.
- No casing is required in collapsing ground conditions.
- Made from a high quality, high yield, low carbon steel, which does not suffer from hydrogen embrittlement or stress corrosion cracking.
- The grout body and controlled crack widths provide permanent corrosion protection.
- Very low creep characteristics of the bar eliminate the need for restressing
VERSATILE AND EFFECTIVE GROUND ENGINEERING SOLUTION
Ground Anchors Installed At Belfast Harbour
This was a challenging project in terms of access, logistics, ground conditions and design. The type of conditions where Ischebeck Titan ground anchor solutions are regularly called for. In 1990, ground investigations near the site were undertaken and the bore hole records showed mixed, variable and challenging conditions.
Byland Engineering Ltd were commissioned by Quinn Piling Ltd, to undertake the element design of 11 No. permanent ground anchors. The ground anchors were required to support an approx 34m long section of new sheet pile wall, installed in front of the existing ‘failing’ wall, as part of the Wing Wall remedial works at West Twin Wharf.