| Permanent
Single Bore Multiple Anchors (S.B.M.A.) were installed to new
sheet pile walls. The site is an area of protected status requiring
minimum environmental impact. |
|
Project
The Environment Agency's Broadland Strategy aims to reduce the risk
of flooding along almost 240 km of river bank. At the Berney Arms
and Reedham Ferry sites protected land plus a bird sanctuary gave
severe problems to the Client in the reconstruction of the river wall.
The original retention scheme consisted of tie bars at close centers
along the wall which was unacceptable to the various authorities.
Soil
Conditions
Ground conditions behind the walls consisted of thick deposits of
very soft alluvium overlying a medium dense fine sand deposit with
interbedded clay bands.
Solution
To minimise disruption to the surroundings, Keller Ground Engineering
proposed to use a high capacity ground anchor alternative with SBMA
anchors at maximum spacings. This
allowed anchors to be installed at 4.8m centres producing a cost
effective solution. In all 117 No, 600kN anchors were installed
at Berney Arms Reach and 160 No. were installed at Reedham Ferry.
To confirm the design assumptions, two trial anchors were tested
up to 1200kN without failure.
Construction
All plant and materials were brought in by boat. Drilling and installation
took place from a specially designed cantilever platform. The anchors
were installed using rotary percussive drilling methods with flush
returns carefully controlled within a sump consisting of the gap
between the old and new piles. All anchors were successfully test
loaded to BS8081 standards.
| Client |
Environment
Agency |
| Engineer |
Sir
William Halcrow & Partners |
| Main
Contractor |
Tilbury
Douglas Construction Ltd. |
Specialist
Sub-contractor |
Keller
Ground Engineering |
|
