Slope angle in construction – definition, calculation and practical tips

Summary

The slope angle determines how steep excavation pits and trenches can be constructed without soil slipping.Depending onSoil typeDifferent guidelines apply according toDIN 4124: e.g.45° for clay,60° for sand. AlsoDepth, groundwater, contamination at the edgeandweatherinfluence the permissible inclination.

Too steep? Then protection measures such as shoring, drainage, or geotextiles are mandatory.When conditions are cramped,Articulated telescopic platformsto safely work on hard-to-reach areas –without driving on the embankment. Always important:Analyze soil, comply with regulations, ensure safety.

When excavating excavations and trenches, the slope angle determines stability. It determines how steep the walls can be to prevent the soil from sliding. This protects not only construction workers and machinery, but also adjacent buildings and pipes. In this guide, you'll learn how the slope angle is determined according to DIN 4124, which factors influence it, and what measures you need to take in problematic soil conditions.

What is the angle of repose?

The slope angle describes the inclination of a embankment and is measured in degrees. The steeper the angle, the more space-efficient the excavation pit is—but also the greater the risk of a landslide. An angle that is too shallow, on the other hand, provides safety, but requires more space and increases the excavation. The trick, therefore, lies in finding the right balance between safety and efficiency .

Slope angle according to DIN 4124

DIN 4124 is the authoritative standard in civil engineering for sloped pits and trenches. It specifies guideline values that apply depending on the soil type and pit depth . These values serve as the basis for planning and must not be exceeded for safety reasons.

These guidelines are intended as a guideline. Deviations may be necessary in practice – for example, in the presence of groundwater, frost, or high loads at the slope edge.

What factors influence the slope angle?

In addition to the DIN, several conditions play a role that directly influence the slope angle:

Soil type

Rocky soils are very stable and allow for steep slopes up to 80°. Cohesive soils such as loam and clay are less stable and require shallower angles. Non-cohesive soils such as sand and gravel are considered particularly critical because they tend to give way when exposed to moisture or vibration.

Depth of the excavation pit

The deeper the excavation, the greater the lateral earth pressure. From a depth of 5 m, stricter regulations apply, often requiring additional safety measures such as retaining walls.

Groundwater and weather influences

A high groundwater table can soften and unstable slopes. Rain and freeze-thaw cycles also weaken stability. In such cases, drainage or shoring are essential.

Load at the embankment edge

Heavy machinery, stored construction materials, or traffic near the slope increase the risk of collapse. Therefore, the edge area should always be kept free of loads. If this is not possible, the slope angle must be increased or the slope must be additionally secured.

How is the optimal slope angle determined?

The determination takes place in several steps:

1. Soil analysis: Examination of soil type, moisture content and bearing capacity.
2. DIN guideline values: Application of the specifications from DIN 4124.
3. Individual adaptation: consideration of groundwater, loads and space conditions.

Practical example:

• A 3 m deep excavation pit in clay soil: approx. 45° slope angle.
• A 3 m deep excavation pit in sandy soil: approx. 60° slope angle.

If the space does not allow for a sloped excavation pit, a shoring system is the only safe solution.

Safety measures for steep slopes

Where the DIN angles cannot be maintained, additional safeguards must be installed:

• Retaining walls: prevent slipping and secure the excavation pit.
• Drainage systems: drain groundwater and prevent softening.
• Geotextiles or greening: protect against erosion caused by rain and wind.
• Shotcrete or sheet piling: for deep and heavily loaded excavations.

Common mistakes on construction sites

In practice, problems often arise because basic rules are ignored:

• Slopes too steep due to lack of space
• Heavy loads directly at the edge of the embankment
• No consideration of rain or frost
• Missing or delayed drainage

These errors massively increase the risk of slope collapses – with dangerous consequences for people and machines.

Slope angles and work platforms

When working in excavations or on slopes, choosing the right work platform is crucial. Articulated boom lifts are particularly well-suited for use on slopes because their reach and flexible booms allow them to reach hard-to-reach areas without driving onto the slope. This increases safety and avoids unnecessary strain on the edges.

Conclusion

The slope angle is a key factor in civil engineering. It influences safety, costs, and space requirements. DIN 4124 provides clear guidelines, which must be supplemented by factors such as soil type, groundwater, and load. Planning too steeply risks collapse; planning too shallow wastes resources.

Our tip: Always calculate slope angles professionally, plan for additional safety measures, and choose the right work platform for working in excavations. This will keep your projects safe, efficient, and cost-effective.

About the author

Martin Biberger

Managing Director

Martin is the founder and managing director of BIBERGER Arbeitsbühnen & Forklifts.

He is responsible for thetechnical areaTogether with his team, he is responsible for thetechnical purchasingthe machines thatFurther development of the machine inventoryand the smooth operation of over 1,500 BIBERGER rental devices.

From many years of experience he knows theStrengths and weaknesses of all device classes, the possibleAreas of applicationand thetechnical possibilities– always with a view to theDevelopment of the entire industryand future innovations.