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SUMMARYThis paper proposes an extension to the key-block method, called 'key-group method', that considers not only individual key blocks but also groups of collapsable blocks into an iterative and progressive analysis of the stability of discontinuous rock slopes. The basics of the key-block method are recalled herein and then used to prove how key groups can be identified. We reveal that a key group must contain at least one basic key block, yet this condition is not entirely sufficient. The second block candidate for grouping must be another key block or a block whose movement-preventing faces are common to one or more single key blocks.We also show that the proposed method yields more realistic results than the basic key-block method and a comparison with results obtained using a distinct element analysis demonstrates the ability of this new method.

In this paper, considering the non-linear Hoek-Brown failure criterion, a new theoretical model is presented to predict the stress components and estimate the plastic zone radius around a circular tunnel. The tunnel is excavated in an elasto-plastic rock mass subjected to plane hydrostatic and axial in situ stresses. Effects of the axial in situ stress on the plastic zone radius and stress components are studied. Based on the combination of plane hydrostatic and axial in situ stresses with the equilibrium equation and a suitable failure criterion (Hoek & Brown failure criterion), several cases are considered. For each case, the stress components, the plastic zone radius and the necessary conditions for its occurrence are determined. The results obtained by the present method are compared with those using Mohr-Coulomb criterion and with the experimental data, illustrating the validity of the present model in predicting the failure zone radius.Keywords: Analytical solution, Hoek-Brown criterion, Plastic zone radius, axial in situ stress W artykule zaprezentowano opracowany w oparciu o nieliniowy warunek wytrzymałości HoekaBrowna nowy model teoretyczny przeznaczony do prognozowania składowych naprężeń i estymowania promienia strefy plastycznej wokół tunelu o przekroju kołowym. Tunel wydrążony został w sprężysto--plastycznej skale pozostającej pod wpływem płaskich stanów naprężenia (naprężeń hydrostatycznych) oraz naprężeń osiowych zarejestrowanych in situ. Przeanalizowano skutki oddziaływania naprężeń osiowych in situ na promień strefy plastycznej oraz na składowe naprężenia. Zakładając połączenie płaskich stanów naprężenia, naprężeń osiowych działających in situ z warunkiem równowagi i odpowiednim warunkiem wytrzymałości (warunek wytrzymałości Hoeka-Browna), przeanalizowano kilka wyodręb-nionych przypadków. Dla każdego z rozważanych przypadków określono składowe naprężenia, promień

SUMMARYThe sawing rate is one of the most significant and effective parameters in extracting building stones via diamond wire sawing. This parameter designates the capability of diamond wire sawing for sawing different stones; in addition, the parameter gives rise to economical considerations for quarry designers. In this study, the existent relations between stone geotechnical parameters and the sawing rate of stones via diamond wire sawing were analyzed using regression and correlation coefficient as well as the collected data from Marmarit stone quarries. Moreover, we estimated the sawing rate of Marmarit using the dimensional stone rock mass rating (DSRMR); upon comparison of the data obtained from DSRMR our pre-collected data on quarries, we did not gain satisfactory results from DSRMR, hence we used artificial neural network (ANN). The results showed that the percentage of Silica, the coefficient of water absorption, the uniaxial compressive strength (UCS), and abrasive hardness are the proper parameters for creating the ANN. Discontinuities have the least effects possible on diamond wire sawing. Having given the training possibility of the ANN, and its ability to evaluate relations among input parameters, the ANN, which was being trained with Marmarit's traits, was an accurate network for estimating diamond wire sawing in Marmarit quarries, although it could not generalize this network for other stones such as Chini and Crystal.

SUMMARYThe methods used in conducting static stability analyses have remained pertinent to this day for reasons of both simplicity and speed of execution. The most well-known of these methods for purposes of stability analysis of fractured rock masses is the key-block method (KBM).This paper proposes an extension to the KBM, called the 'key-group method' (KGM), which combines not only individual key-blocks but also groups of collapsable blocks into an iterative and progressive analysis of the stability of discontinuous rock slopes. To take intra-group forces into account, the Sarma method has been implemented within the KGM in order to generate a Sarma-based KGM, abbreviated 'SKGM'. We will discuss herein the hypothesis behind this new method, details regarding its implementation, and validation through comparison with results obtained from the distinct element method.Furthermore, as an alternative to deterministic methods, reliability analyses or probabilistic analyses have been proposed to take account of the uncertainty in analytical parameters and models. The FOSM and ASM probabilistic methods could be implemented within the KGM and SKGM framework in order to take account of the uncertainty due to physical and mechanical data (density, cohesion and angle of friction). We will then show how such reliability analyses can be introduced into SKGM to give rise to the probabilistic SKGM (PSKGM) and how it can be used for rock slope reliability analyses.