Temporary earth retention systems hold back soil to allow safe construction of basements, deep foundations, and underground structures. They include sheet piles, secant piles, contiguous piles, and soldier pile walls with timber lagging. These systems must be designed for the specific ground and water conditions and monitored throughout their working life. This talk covers the key hazards and controls for temporary earth retention.
Key Hazards
Retaining wall failure causing soil collapse into the excavation below
Water pressure build-up behind the wall leading to sudden breakthrough or piping
Ground movement affecting adjacent structures and buried services nearby
Incorrect installation sequence deviating from the temporary works design
Control Measures
Ensure every earth retention system is designed by a competent temporary works engineer.
Install the system in the exact sequence specified in the temporary works method statement.
Monitor wall movement using inclinometers or survey targets at the intervals the designer specifies.
Control groundwater behind the wall using dewatering as specified in the design.
Report any signs of wall movement, water seepage, or ground settlement immediately to the site manager.
Maintain exclusion zones at the toe of the wall and behind the crest during installation.
Do not excavate below any level ahead of the retention system installation without designer approval.
Record all monitoring readings in the temporary works register and review against trigger values.
Brief operatives on the monitoring trigger levels and the emergency response if they are exceeded.
Remember
Every temporary earth retention system must be designed by a competent temporary works engineer
Install in the exact sequence specified in the method statement without deviation
Monitor wall movement at the intervals the designer specifies and record all readings
Report any wall movement, water seepage, or ground settlement to the site manager immediately
Do not excavate below any level ahead of the retention system without the designer's approval
Review monitoring readings against trigger values and know the emergency response procedure
Applicable Legislation: CDM Regulations 2015 · BS 5975:2019 (Temporary Works) · BS 8002 (Earth Retaining Structures) · Health and Safety at Work etc. Act 1974