ABSTRACT
The presence of joints in a rock mass has a significant influence on its shear strength and deformation characteristics. In hard rocks, for relatively closely spaced joints, the mechanical behaviour of the rock mass is similar to that of the joints in relation to the strength of the intact rock material. The shearing of rough joints no longer takes place under constant normal load. This chapter discusses the studies conducted on the behaviour of clean/unfilled rock joints, particularly those of experimental modeling. The presence of joints in a rock mass can affect its mechanical behaviour, depending on the underground situation. In general, the Constant Normal Load (CNL) condition is only realistic for shearing of planar interfaces, where the normal stress applied to the shear plane remains relatively constant such as in the case of rock slope stability problems.
