Shear resistance:

Maximum shear stress that a soil can endure without reaching breaking, expressed as the following relation: τRk = ck + σn tg φk Two situations are distinguished: a) “with drainage”; refers to those situations in which, either for good conditions of permeability, either for the long time elapsed since the load application, the ground has dissipated the excess interstitial pressure that could have been generated during the loading process. b) “Without drainage”: refer to those situations in which, either for lack of drainage, either for the limited time elapsed since the load applications, there are on the ground the same interstitial pressures that have been generated during the loading process.