An embankment is a natural or artificial kink or jump in terrain. Natural embankments are created by geomorphological processes ( e.g. erosion , uplift , sedimentation ) and are often referred to as "slopes". Artificial embankments are created through the construction of dams and incision structures in water and traffic route construction as well as the construction of sloping excavations and trenches .
The stability of a slope is determined by the slope angle and is dependent on a number of influences. In the event that a slope is not designed to be stable, the slope may break.
A slope is characterized by the slope and the difference in height. The inclinations are given as a gradient ratio or in degrees from the horizontal. A slope of 1: 2 means, for example, a height difference of 1 meter over a horizontal length of 2 meters or against the horizontal. The possible slope of a slope depends on the characteristics of the slope soil.
In addition to the vegetation, the slope angle is decisive for the stability of the slope in predominantly dry locations. A natural slope made of non-cohesive material has the slope inclination that corresponds to the angle of internal friction (the angle of friction ). Even an artificial embankment can have this slope at most. A higher gradient leads to a slope failure.
Cohesive material that contains fine components such as clay and silt also has a cohesion that holds the material together. This allows the slope to have a steeper angle. The same applies to damp sand when it is compressed. But if it dries up, the embankment collapses. The angle of repose for loose ground, the so-called angle of repose , is in the range of 25–45 °, for other angles of repose see angle of friction .
The following slope inclinations must not be exceeded without mathematical proof:
- non-cohesive or soft soil = 45 °,
- cohesive soil = 60 °,
- Rock = 80 °.
Influences on stability
The stability is influenced by various factors. The properties of the existing soil types, such as geological fault zones and unfavorable storage conditions, are essential for stability. Corresponding water conditions ( groundwater , surface water , excess pore water pressure ) also favor a slope failure. Loads on the top edge of the slope from buildings and traffic as well as vibrations from earthquakes can also cause the slope to break. With embankments in hydraulic engineering, the additional hydrostatic and hydrodynamic effects of the water, which often require the arrangement of embankment revetments , must be taken into account .
Slope in civil engineering
The formation of slopes is suitable for creating excavations and trenches if there is sufficient space. From an economic point of view, the greatest possible slope angle is to be aimed for. According to DIN 4124, the following slope angles must be observed:
- 45 ° for non-cohesive or soft cohesive soils
- 60 ° for stiff or semi-firm cohesive soils
- 80 ° on rock
If a stable construction of the embankment is not possible, a suitable construction method must be selected.
Embankment in road construction
In road construction , dams and cuttings allow a road course largely independent of the terrain. The embankments associated with this are usually built with a standard slope inclination of 1: 1.5. For the purpose of landscape protection , the preservation of the landscape and the reduction of erosion, the slope areas are to be planted and greened.
A poorly cultivated embankment is an ecologically important linear biotope . Such an area is often rich in perennials or shrubs , where direct disturbance of the plant and animal species living here is rare. It therefore makes an important contribution to biodiversity .
Approach angle for vehicles
For off-road vehicles , but also for buses and trucks , the indication of the slope angle (also overhang angle) denotes the maximum gradient that can be approached from the plane without overhanging body parts touching the ground. A distinction is made between the front and rear slope angle. Prerequisite for large angles are as high as possible lying and short body overhangs or extensions (eg. As winch , bumper, trailer hitch).
Norms and standards
- DIN 4124 excavations and trenches
- DIN 1054 subsoil - proof of safety in earthworks and foundation work
- Additional technical contract conditions and guidelines for earthworks in road construction (ZTVE-StB)
- Slopes and jumps in terrain. Script of the Chair for Foundation Engineering, Soil Mechanics and Rock Mechanics at the Technical University of Munich (PDF; 1.34 MB) ( Memento from July 18, 2013 in the Internet Archive )