Safety and health alert 18/05 Concrete panel retaining wall failure Incident A 20-tonne con crete tilt-up pan el recently colla psed, resulting i n significant d amage to a work vehicle. The concrete panel was part of a retaining wall consisting of individual concrete panels. The retaining wall had been in situ and had been backfilled with soil for approximately 9 months prior to the incident. At the time of the incident, the concrete panel failed to withstand the forces applied by the backfill soil, falling outwards into an adjacent car park and onto a work vehicle. The concrete panel had been poured on site and lifted into position (tilt–up), with a footing being poured after the panel was in place (post pour footing), in accordance with the design engineer’s requireme nts. Each concrete panel of the retaining wall was free-standing. They were held into position by reinforcing steel through the base of each panel into a postpoured footing. No ground anchors were part of the design. An investigation following the i ncident revea led a section of the footing was una ble to withstand the forces applied to the footing. The front (toe) section of the footing failed, allowing the concrete panel to fall over. Advice to WorkSafe indicates that the incident was a result of a design fault that would not be obvious to most structural enginee rs. Factors • The retaining wall consisted of concrete panels that were not anchored into the backfill or tied together. • The concrete panel was being held in position by way of reinforcing steel through the base of the panel into the post-poured concrete footing. • The design of the retaining wall did not adequately address the forces that were to be applied to the footing. Recommendations 1. Persons wh o have con trol of workp laces where freestanding concrete pa nels are i n use as retaining walls should confirm that the wall is structurally sound. 2. Section 23(3a) of the Occupational Safety and Health Act 1984 requires persons who design and construct any buildin g or structure for use at a workplace to, as far as is practicable, ensure that the design and construction is such that persons who properly use the building or structure are not exposed to hazards. Designers of retaining walls need to consider the adequacy of their designs in terms of all the forces likely to be imposed on the retaining walls and their footings. Further information Further information can be obtained from the WorkSafe internet site www.worksafe.wa.gov.au , or by contacting customer service on 1300 307 877 or email: [email protected] . A 412507 Date: September 2005

Safety Alerts 2005-18-05 Concrete Panel Retaining Wall Failure

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Safety and health alert

18/05 Concrete panel

retaining wall failure Incident

A 20-tonne concrete tilt-up panel recently collapsed, resulting in significant damage to awork vehicle. The concrete panel was part of a retaining wall consisting of individualconcrete panels. The retaining wall had been in situ and had been backfilled with soil forapproximately 9 months prior to the incident. At the time of the incident, the concrete panelfailed to withstand the forces applied by the backfill soil, falling outwards into an adjacent carpark and onto a work vehicle.

The concrete panel had been poured on site and lifted into position (tilt–up), with a footingbeing poured after the panel was in place (post pour footing), in accordance with the designengineer’s requirements. Each concrete panel of the retaining wall was free-standing. Theywere held into position by reinforcing steel through the base of each panel into a postpouredfooting. No ground anchors were part of the design.

An investigation following the incident revealed a section of the footing was unable towithstand the forces applied to the footing. The front (toe) section of the footing failed,allowing the concrete panel to fall over. Advice to WorkSafe indicates that the incident was aresult of a design fault that would not be obvious to most structural engineers.

Factors• The retaining wall consisted of concrete panels that were not anchored into the

backfill or tied together.

• The concrete panel was being held in position by way of reinforcing steel through thebase of the panel into the post-poured concrete footing.

• The design of the retaining wall did not adequately address the forces that were to beapplied to the footing.

Recommendations

1. Persons who have control of workplaces where freestanding concrete panels are in

use as retaining walls should confirm that the wall is structurally sound.2. Section 23(3a) of the Occupational Safety and Health Act 1984 requires persons who

design and construct any building or structure for use at a workplace to, as far as ispracticable, ensure that the design and construction is such that persons whoproperly use the building or structure are not exposed to hazards. Designers ofretaining walls need to consider the adequacy of their designs in terms of all theforces likely to be imposed on the retaining walls and their footings.

Further informationFurther information can be obtained from the WorkSafe internet sitewww.worksafe.wa.gov.au, or by contacting customer service on 1300 307 877 or email:[email protected].

412507 Date: September 2005