ANALYSIS OF PLASTIC ZONE AND LOOSE ZONE AROUND OPENING IN SOFTENING ROCKMASS
Yuan Wenbo and Chen Jin (Beijing Post-graduate Department, China Institute of Mining Technology)
An elasto plastic softening model is set up according to strain-softening deformation characteristics of rockmass; mechanical behaviours of plastic and loose zone arouud the opening in the soft rock are also analyzed; a formula for calculating the radius of plastic zone is derived, which is more practical and has a wider application scope than Kastner formula. The results of this paper have shown that the strain-softening behaviour of rockmass has a great bearing on the mechanical behaviour of surrounding rock,the radii of plastic and loose zones and stability of the surrounding rock. Reinforcement of the rock around the openings is an effective method for controlling softening of rockmass and increase of its residual strength.