Beckton STW Land Slip Learning Bulletin Dated 04 06...

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