EXC/Support Systems/TBT-EXC-014

Battered Excavation Design

Excavations › Support Systems › Battered Excavation Design

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A battered excavation uses sloped sides instead of vertical faces to prevent collapse.
The safe angle of batter depends on soil type, moisture content, depth, and surcharge loading.
Sandy and granular soils require shallower batter angles than cohesive clay soils.
Battered excavations require significantly more space than supported vertical excavations.
A competent person must determine the safe batter angle based on actual ground conditions.
Surcharge loads from plant, materials, or spoil heaps near the edge reduce the safe angle.
Water ingress from rain or groundwater weakens the soil and can trigger sudden slope failure.
Battered excavations must still be inspected at the start of each shift and after rainfall.
Spoil must be stored far enough from the edge to avoid loading the battered slope.
Tension cracks at the top of a battered face are an early warning sign of imminent failure.

Prevent collapse	Excavation collapse kills and buries workers in seconds — correct batter angles are a primary control measure.
Ground variability	Soil conditions change with depth and weather — what appears stable today may collapse after rain tomorrow.
Legal requirement	CDM 2015 requires excavations to be designed and inspected by competent persons to prevent danger.

Don't

Engage a competent person to determine the safe batter angle for the soil type
Assess the ground conditions including soil type, moisture, and groundwater level
Allow adequate space on site for the batters when planning the excavation layout
Inspect battered excavations at the start of each shift and after rain
Keep spoil heaps and heavy loads well back from the top of the batter
Install dewatering if groundwater or surface water is affecting slope stability
Monitor the batter face for signs of cracking, bulging, or seepage
Reduce the batter angle if conditions are wetter or weaker than expected
Fence the top of battered excavations to prevent people and plant from the edge
Record inspections and any changes to the batter angle in the site records

See also: Trench Collapse Prevention | Excavation Inspection Requirements

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