Rock brittleness is one of the most important issues in rock mechanics. There is not yet an available method for defining or measuring directly the rock brittleness. The aim of this study is to suggest a new chemical index parameter for the prediction of basaltic rocks’ brittleness. In the order of that abovementioned purpose, a total of 23 basaltic rock samples were collected from different region of Turkey. Samples were initially tested to determine their chemical properties. Then, mechanical tests were carried out to define the brittleness indices (B1, B2, and B3) for each corresponding sample. Finally, relations between parameters obtained from test results and brittleness indices were examined with regression analysis. According to the results obtained, a new chemical parameter (CP) was proposed for predicting brittleness via major oxide element components of basaltic rocks. It was found out that, B1 and B2 are not reliable parameters for predicting the different properties, however; B3 and CP can be employed as good criteria for predicting the different properties of basaltic rocks (especially in terms of chemical and mechanical properties)., Candan Bilen, Selman Er, Atiye Tuğrul and Murat Yilmaz., and Obsahuje bibliografii
In order to quantitatively study the influence of temperature and confining pressure on brittle plasticity of granite, this paper reviews previous studies regarding quantitative calculation methods for the brittle-plastic behaviors of rocks and their mechanical characteristics under high temperatures and confining pressures. Combining the experimental results for temperatures and confining pressures with theoretical calculations of brittleness and plasticity allowed quantitative calculations and evaluations for the brittleness and plasticity of granite to be obtained. The main conclusions are as follows. (1) High temperatures lead to a transformation of granite from brittle failure to plastic failure. Comparing six conventional empirical equations from the literature, the B3 and B6 can more accurately describe the relationship between the brittleness and temperature of granite. (2) When the confining pressure σ3 is less than 20 MPa, the internal pore structure and fractures of granite are re-compacted and reduced, which gradually increases its brittleness. With the increasing confining pressure, the pore structure changes again after exceeding 20 MPa. This initiates new cracks, which ultimately leads to a decrease of the granite brittleness. (3) The abrupt temperature for the brittle-plastic transformation of granite is approximately 800 °C, and the brittle-plastic transformation of granite is mainly affected by temperature and not the confining pressure.