The paper deals with the new principles of estimation of tension stress, acting inside rock massive and its strength against it according to the estimation of rock masses of block type. The proposed method of calculation is based on the data of field and model experiments and takes into consideration tensile strength of rock masses, tension, structural peculiarities of the massand the form of sliding surface. Observations of the real forms of stability failure of rock slopes and experimental investigations on the models of block type slopes showed that the development of the process of the stability break of rock mass begins from formation of tension crack on the surface of the slope and it is the beginning of the future failure (Fig. 1).
The process is accompanied by the simultaneous formation of potential surface of slipping. Failure of the rock mass of block type happens on the reach of failure surface as the result of the tension crack. This surface, as experiments show, in most cases has flat or step form, especially under layer construction of rocks (Fig. 2). The latter form can be easily approximated in the form or the straight line on the draft.
The type and degree of the tension crack is determined by structure - texture peculiarities of rock's inner structure. We should point out thick layers and monolitic layers (non-layer and nonsystem cracked) (Fig. 3). Rock mass structure is determined by its inner structure and the conditions of overlapping of individual blocks in layers, for example as "brick building". In layer rock masses as they are widely spread in nature, two main structures: heterogeneous and homogeneous (Fig. 3) are to be noted. Besides a large group of intermediate structures are formed in nature.
(Figure in full paper)
Tension crack, as a rule, is vertioal or steep. The analysis of the character of stress distribution inside the slope showed that it is the result of the influence of horizontal tension stress, that are formed in the upper part of the slope before destruction. The role of tension stress for formation of the tension cracks and stability break of slopes was underlined by Bernatski L.N.(1935), Nichiporovitch A.A. (1948),Maslov N.N. (1949), Lykoshin A.G. (1953) and other scientistsf1–4].
In such conditions stability break of rock slopes made of blocks of rock masses of different stability doesn't occur at once and develops during long time from several years to dozens of years (Odessa - 5–7 years, Makedonia land-slope, according to Shukle L.- 30 years) [5]. During this time formation of tension crack and its appearance on the surface of and destruction of landslide slope out of the main massive occurs. Besides, as the analysis showed, most part of destruction would be impossible without departure of landslide block from the main massive by tension crack.
(Figure in full paper)
Different depth of the forming tension cracks is explained by inner construction of the-rook massives, which due to its cracking, differ ordinary soil.
