Spalling is a mode of failure which occurs in brittle materials. In this paper, the effective factors on spalling phenomenon at Nayriz Marble Mine (Iran) were investigated. Earlier experiments have proven that this type of failure can occur when the stress is as high as one-third of the material's uniaxial compressive strength. Anisotropy and fluctuations of temperature also contributes to weakening of the rock as well as inducing thermal stresses which helps spalling to occur at lower stress levels.

Samples from the mine were taken and their mechanical parameters were determined in the laboratory. For determination of stress state at the mine wall, a new modified Under Coring Method was used; a numerical code was used to calculate the redistributed state of stress at the mine wall. The effect of temperature was also considered in the analysis by performing a thermo-mechanical analysis. This effect can be as high as 15MPa due to 20 degrees Celsius temperature change. The results showthat the concentrated stresses at the wall due to in situ stress filed can not by itself provide necessary conditions for spalling failure to occur, and other factors (such as temperature variations, anisotropy, and/or time dependent behavior etc) should also play a role to cause spalling. The present paper explains stress determination at site in more details and other parameters need further investigations.

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