angle of friction [TECH.] | der Reibungswinkel Pl.: die Reibungswinkel
friction angle [TECH.] | der Reibungswinkel Pl.: die Reibungswinkel
https://dict.leo.org/englisch-deutsch/Ersatzreibungswinkel

Furthermore parameters, e.g. the stiffness modulus Es or the friction angle φ′, are limited in its application to certain boundary conditions.
https://core.ac.uk/download/pdf/236376985.pdf

Tabelle 2. Beziehungen zur Ableitung von Ersatzreibungswinkeln φcu bei undrädnierten Bedingungen
Table 2. Equations to approximate the undrained angle of internal friction φcu from undrained strength cu
https://www.kup-geotechnik.com/media/2002h_kempfert_gebresel...

Equivalent Friction Angle and Cohesion of the Generalized Hoek-Brown Failure Criterion in terms of Stress Invariants
https://www.researchgate.net/publication/264182659_Equivalen...

Cohesion and the equivalent friction angle of pure soil and root-soil composite.
https://www.researchgate.net/figure/Cohesion-and-the-equival...

To include the dependency of cohesion and friction angle on stresses, efforts are being made to estimate equivalent values of the M-C parameters for the range of stresses applicable to a particular design. The paper suggests a new and convenient approach to find the equivalent friction angle and cohesion from any failure criterion that can be expressed in terms of the Nayak and Zienkiewicz's stress invariants.
https://ui.adsabs.harvard.edu/abs/2014RMRE...47..371L/abstra...

For this purpose, a concept of equivalent friction angle is usually used [3, 5, 6, 8]. This angle is defined as the friction angle of the MC surface that would pass through the particular stress point given by the shear strength criterion under consideration.
https://sciendo.com/pdf/10.2478/sgem-2018-0016