Mechanical behaviour of flysch formation consolidated by anchor cables

The aim of this paper is the evaluation of anchor cables mechanical behavior, which can be used to increase the stability of an excavation realised in a stratified rock mass. Anchoring zone behavior is analysed with particular reference to cables installed in a non-homogeneous rock mass showing strong hysotropic behavior. This is the case of flyschoide formations, frequently present in the Northern Apennines (Italy), characterised by a sequential alternation of torbiditic beds and banks, where the phase of sedimentation succession is recognisable. The resistant shear and tension stresses induced in the anchor elements depend upon geometrical and mechanical features of rock formation and support. In order to evaluate the anchor cables-rock structure behavior and the bearing capacity of the system, field tests (pull-out tests) were performed. The pull-out tests were then interpreted through a numerical simulation which allows for the determination of the maximum force acting on the support elements itself and of the force-displacement behavior of the system.