Beckton STW – Land Slip Learning Bulletin
Incident Learning Bulletin
Introduction – At 9.45am on Thursday 23
collapsed.
Remedial works to the batter consisted of a reduced
batter and a step introduced to the profile over zone of
the collapse.
The collapse was reviewed by the Geotechnical
Engineering team and remedial works approved prior to
recommencing works.
All excavation inspections had been carri
observations of surface cracking or movement. The
excavation had been carried out in strict accordance with
the temporary works. Cranes were rigged at 6m from the
excavation crest in accordance with CIRIA guidance.
Learning
Following review by the Geotechnical Engineer and analysis of the fa
of water at an isolated location has significantly altered the parameters of the
fully drained condition, consistent with considerable water ingress. Existing services, tree roots and silt partings
may have provided the water path.
Control measures implemented for the remainder of the excavation works:
• Existing services are marked and identified for thorough
• Excavation inspections carried out 3 times per day
• Checklist used for identifying specific excavation risks
ingress, surface movements, surface cracking
• Specific reference to the excavation inspections and access requirements in all safe systems of works.
It is important to assess existing services and protrusions that may influence ground conditions in the vicinity of an
excavation, especially close to a batter crest.
Land Slip Learning Bulletin – Dated 04.06.2013
Beckton STW
Incident Learning Bulletin
At 9.45am on Thursday 23rd May 2013, a section of the Settled Sewage Pipeline excavation
An operative within the trench observed a crack form
at the upper right hand side of the batter
begin to move. All personnel left the trench
immediately.
The operative then observed the slow, progressive
collapse of the batter propagating to the left to a
distance of 9.1m, as shown in the photo
consisted of a reduced
batter and a step introduced to the profile over zone of
The collapse was reviewed by the Geotechnical
Engineering team and remedial works approved prior to
All excavation inspections had been carried out with no
observations of surface cracking or movement. The
excavation had been carried out in strict accordance with
were rigged at 6m from the
with CIRIA guidance.
ew by the Geotechnical Engineer and analysis of the failure mode, it appears that
has significantly altered the parameters of the clay. It behaved as if in a long term
with considerable water ingress. Existing services, tree roots and silt partings
Control measures implemented for the remainder of the excavation works:
Existing services are marked and identified for thorough, continuing inspection;
Excavation inspections carried out 3 times per day by the Temporary Works Supervisor
Checklist used for identifying specific excavation risks forms part of the excavation inspection i.e. water
ingress, surface movements, surface cracking;
Specific reference to the excavation inspections and access requirements in all safe systems of works.
It is important to assess existing services and protrusions that may influence ground conditions in the vicinity of an
batter crest.
Dated 04.06.2013
a section of the Settled Sewage Pipeline excavation
perative within the trench observed a crack form
at the upper right hand side of the batter and the bank
begin to move. All personnel left the trench
The operative then observed the slow, progressive
collapse of the batter propagating to the left to a
distance of 9.1m, as shown in the photo opposite.
it appears that significant ingress
clay. It behaved as if in a long term
with considerable water ingress. Existing services, tree roots and silt partings
by the Temporary Works Supervisor;
forms part of the excavation inspection i.e. water
Specific reference to the excavation inspections and access requirements in all safe systems of works.
It is important to assess existing services and protrusions that may influence ground conditions in the vicinity of an