Project
As part of the structural upgrade of the Camber Dock, a new sheet
pile wall required supporting over a 236m lenght of wall.
The client originally proposed a tie bar system, which involved
the demolition of a fisherman's store structure to allow trenching
and installation of the tie rods and driving of rear pile wall.
Soil Conditions
The geology behind the existing quay wall consisted of fill and
marine deposits overlying Bracklesham Beds. This main stratum was
stiff to hard silty sandy Clay and clay-bound sand. Additional complications
included the presence of old retaining walls buried behind the existing
quay side structure.
Solution
Keller Ground Engineering proposed high capacity ground anchors
at 4m spacings along the wall. This demanded a working load of up
to 1300kN per anchor, probably the highest permanent anchor working
load used in a stiff to hard sandy clay stratum. Such loading is
only possible due to the SBMA efficiency in using ground strength
over a multiple of anchor unit fixed lengths totalling 25m. An additional
complication arose from the problem of anchor interference due to
the curvature of the wall layout.
The
complex anchor arrangement, utilising anchors at a variety of inclinations,
was prepared using Autocad systems. The construction of the final
anchor layout demended precision in set-up and drilling control
and monitoring in both directions with minimal borehole deviation.
Test anchors were installed and tested up to 2.5 times the working
load (3250kN) to ensure satisfactory performance of the designed
anchors.
Construction
All ground anchors were installed using Keller's specially converted
machines for under-slung drilling. Despite the severity of the drilling
difficulties in penetrating a muLtiple of existing barriers (concrete,
masonry and steel) all anchors were installed successfully and no
unacceptable deviations occurred causing anchor interference.
| Client
and Engineer |
Portsmouth
City Council |
| Main
Contractor |
J
T Mackley Ltd. |
| Specialist
Sub-contractor |
Keller
Ground Engineering |
|
