Emergency repair works were needed at Junction 14 of the M11 to address voids beneath the carriageway close to bridge abutments that posed a risk of settlement or collapse. Geobear designed an innovative solution to stabilize the embankments by pumping a two-component geopolymer material into the voids through steel tubes inserted into the road surface. Working through the night over three weeks, four Geobear crews were able to fill the voids and stabilize the area, completing the project on time and within budget with minimal disruption to traffic.

1. 1 M11 STABILISATION WORKS GEOBEAR
The project involved emergency remedial works at junction 14 of the A14 Cambridge to
Huntingdon Major Improvement scheme. The junction comprises a two-lane slip road section
of motorway with cloverleaf junction that links the M11 to the A428 and A14. This section of the
northbound M11 carries around 40,000 vehicles a day and forms part of the strategic highway
network which also serves Stansted Airport and provides access to strategic ferry ports.
Issues with the embankments to the bridge abutments on the M11 overbridge at Jct 14 had
been identified by Highways England as part of routine maintenance inspections. Further
investigation through visual and ground penetrating surveys and dynamic probing identified
the presence of voids beneath the carriageway close to the abutments which, if left, could
have resulted in significant risk of settlement or collapse of the carriageway.
An urgent solution was needed that would meet both technical and programme requirements
without compromising safety. The solution required the improvement of the foundation strata
compressive strength to 4MPa, implemented with minimal disruption to road users and the
wider improvement scheme. Geobear were consulted by WSP and subsequently designed
an innovative and time efficient solution that could be implemented from the carriageway
surface with minimal disturbance to the carriageway surface, and minimal reinstatement
works.Karl Brooks, Highways England
M11 Stabilisation
Geobear’s solution to the essential
embankment repair at M11 Girton
interchange has been a highlight of this
year’s 2018/19 programme of works.

2. 2 M11 STABILISATION WORKS GEOBEAR
Four Geobear crews worked through the
night over a three week period to deliver
the emergency works.
Specialist two-component geopolymer
material was used to fill the voiding
beneath the M11 and stabilise the area.
The material is mixed on site and pumped
into the void through steel tubes.

3. 3 M11 STABILISATION WORKS GEOBEAR
A drilling rig was used to core 50mm holes
into the road surface and through the
slab. The holes would accomodate the
steel tubes and also be used for a cctv
monitoring.
With the drilling completed the
programme of injection works could be
agreed. Sequences of material placement
were designed by the Geobear engineering
team.

4. 4 M11 STABILISATION WORKS GEOBEAR
Laser monitoring is used while material
is injected into the ground to ensure no
vertical movement of the slab.
Steel tubes
are positioned
through the slab
to place material.

5. 5 M11 STABILISATION WORKS GEOBEAR
Geopolymer injection
Material is pumped
directly from the self
contained Geobear
units through a hose
and controlled with an
injection mechanism .

6. 6 M11 STABILISATION WORKS GEOBEAR
The material injections are sequentially
planned, but engineering teams on-site
make variations as required.
Technical teams keep a record of the
quantity of material injected through each
steel tube into the void. This, together with
visual surveys ensures the voids are filled.

7. 7 M11 STABILISATION WORKS GEOBEAR
The methodology allows for teams to work
in localised areas ensuring crucial routes
can be kept open.
Once a voided area has been filled and stabilised,
the steel tubes are cut and the holes in the road
surface filled.
Project was completed on time and and within
budget. The scheme of works was recognised as a
finanlist at the 2019 Ground Engineering Awards.