Slope stability

The Gleitkreisverfahren (English: "Method of Slices " and "general limit equilibrium method") is a method of stability calculation of embankments in geotechnical engineering ( slope failure detection).

The procedure

Because of the collapse of an embankment often circular arc slip surfaces occur ( particularly clear in tone, where Alexandre Collin this, first observed in the 1840s ), examines one circular broken body and therefore speaks of Gleitkreisverfahren. In the calculation process, a distinction is free laminate (where there is a single rupture body) and slice method ( in this case, the breaking body in a plurality of vertical wheels, the blades divided ). The methods are further subdivided depending on the forces ( weight, soil pressure, water pressure, buoyancy, traffic load, etc. ) and resistance (friction, shear strength ) and the mechanisms that are taken into account or neglected. The first, the calculations performed by the Gleitkreisverfahren were Knut Petterson and Sven Hultin by the Port Authority in Gothenburg in 1916. They calculated the landslide a Hafenkaimauer in Gothenburg. Fellenius (and Krey ) improved the method in the 1920s to such an extent that today it is better known under the name Fellenius process or as Krey - Bishop method. Various authors have later ( in the 1950s and thereafter) contributions and improvements delivered ( Otto Karl Fröhlich, Alan W. Bishop, Nilmar Janbu, Hubert Borowicka etc.).

In addition to the Gleitkreisverfahren there are also methods using polygonal slide surfaces, eg after Janbu.

Today you can find in DIN 4084 guidelines for terrain and slope stability calculations by these methods.

In a concrete proof of stability of a slope varying gradually the center and radius of the slip circles until you have found the arc with the lowest and thus relevant security.

Lamellae free process

The lamellar bodies of the breaking -free process is considered as if it slips off as a whole in a circular arc-shaped surface. All invasive external forces are combined into a resultant force and compared to the resisting forces in the slip plane. The stability is determined by Fellenius for the determined slip circle from the ratio of resisting forces to the attacking forces and the torques about the center of the circle.

Slice method

With slat method according Krey / Bishop dividing the fracture body in a more vertical slats, on which act the various forces. At each lamella formulating the equilibrium of forces. These forces are in addition to the above-mentioned addition Erddruckkräfte the two sides of the slats. The forces of the slats summing on the overall balance.

An alternative method for the calculation of embankments is the kinematic element method.