Tunnel and shaft solutions brochure - Humes
Tunnel and shaft solutions brochure - Humes
Tunnel and shaft solutions brochure - Humes
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Top:<br />
Underpin method<br />
of <strong>shaft</strong> installation<br />
Bottom:<br />
Segment lifting<br />
frame for underpin<br />
method<br />
Underpin method<br />
The underpin method can be used in self supported soil<br />
where caisson installation is not possible. In this method,<br />
the precast concrete elements are progressively installed<br />
at the base of the excavation. Segmental rings are built<br />
<strong>and</strong> the annulus between their outside perimeter <strong>and</strong><br />
the excavated ground is immediately grouted.<br />
The recommended installation procedure is as follows:<br />
• Secure the first installed ring by casting a concrete<br />
collar around it prior to excavating underneath<br />
to construct the next ring. Shear connection may<br />
be required.<br />
• Always excavate, install <strong>and</strong> grout one ring at a time.<br />
This reduces the risk of overloading the upper rings<br />
which could pull down the whole ring build, due to<br />
lack of ground friction.<br />
• Excavation of the next ring below can commence once<br />
the grout reaches it recommended strength.<br />
• The underpin segments are designed to be installed<br />
using a specialised h<strong>and</strong>ling/lifting frame. The<br />
segment will be secured into the frame via the plastic<br />
grout socket assembly. If you wish to hire a frame,<br />
contact <strong>Humes</strong> for assistance.<br />
10 <strong>Tunnel</strong> <strong>and</strong> <strong>shaft</strong> <strong>solutions</strong>
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